International Journal of Antimicrobial Agents - Articles in Press

Daily serum piperacillin monitoring is advisable in critically ill patients - Corrected Proof

2010-03-12

Abstract: The aim of the present study was to evaluate the benefit of monitoring serum piperacillin concentrations in critically ill patients. This was an 11-month, prospective, observational study in a 30-bed Intensive Care Unit in a teaching hospital, involving 24 critically ill patients with evidence of bacterial sepsis. All patients received a 66mg/kg intravenous bolus of piperacillin in combination with tazobactam (ratio 1:0.125) followed by continuous infusion of 200mg/kg/24h. The dosage was adjusted when the serum piperacillin concentration either fell below 4× the drug's minimum inhibitory concentration (MIC) for the causative agent or exceeded the toxic threshold of 150mg/L. With the initial regimen, serum piperacillin concentrations were within the therapeutic target range in only 50.0% of patients (n=12). This proportion increased to 75.0% (18 patients) (P=0.006) following dosage adjustment. For patients with low initial serum piperacillin concentrations (n=8), the percentage of time during which the concentration remained above 4× MIC (%T>4× MIC) was 7.1±5.9% before dosage adjustment and 27.3±8.6% afterwards. In conclusion, in critically ill patients, monitoring and adjustment of serum piperacillin levels is required to prevent overdosing and might also help to correct underdosing, an important cause of antibiotic therapy failure.

Microbiological outcome of complicated urinary tract infections treated with levofloxacin: a pharmacokinetic/pharmacodynamic analysis - Corrected Proof

2010-03-12

Abstract: The pharmacodynamic targets representing 90% probability thresholds for bacterial eradication were determined in patients with complicated urinary tract infections (UTIs) treated with 500mg of levofloxacin every 24h for 7–14 days. Of 241 pre-treatment strains from 156 patients, 21 strains persisted after treatment. In each patient, plasma concentrations of levofloxacin were simulated based on population pharmacokinetic parameters and patient-specific data. Minimum inhibitory concentrations (MICs) of levofloxacin for the pre-treatment strains determined in our previous study were used. The pharmacodynamic targets representing 90% probability thresholds for bacterial eradication were determined by logistic regression analyses. For all the isolates, Gram-negative bacilli, Gram-positive cocci, Escherichia coli and Enterococcus faecalis, the target values of the area under the concentration–time curve (AUC)/MIC were 14.65, 31.46, 4.85, 43.00 and 3.06, respectively, and the targets of the maximum plasma concentration (Cmax)/MIC were 1.22, 2.74, 0.39, 3.61 and 0.25, respectively. Such thresholds of AUC/MIC and Cmax/MIC in complicated UTIs would be lower than those in infections of other sites. In particular, the Cmax/MIC thresholds for Gram-positive cocci and E. faecalis were <1. These findings suggested that, in addition to its plasma concentration, the high concentration of levofloxacin in the urine might play a role in eradicating bacteria.

Encapsulation in fusogenic liposomes broadens the spectrum of action of vancomycin against Gram-negative bacteria - Corrected Proof

Daria Nicolosi, Marina Scalia, Vito M. Nicolosi, Rosario Pignatello — 2010-03-11

Abstract: Many antibacterial agents, including the glycopeptides, are inactive against Gram-negative bacteria because of their inability to cross the outer membrane of these cells. Different chemical and technological approaches have been described to circumvent such limitation. In this study, we aimed to apply the strategy of fusogenic liposomes, up to now used to carry biological compounds and materials inside cells, to localise a glycopeptide antibiotic, vancomycin (VAN), to the periplasmic space, thus allowing it to exert its bactericidal activity. Small unilamellar liposome vesicles were prepared by an extrusion procedure (SUVETs) from a phospholipid–cholesterol hemisuccinate mixture known for its fusogenic properties with the eukaryotic cell membrane. VAN was loaded with high efficiency into these vesicles and in microbiological experiments in vitro was shown to be able to inhibit to a different extent the growth of wild and standard Gram-negative bacterial strains. Minimum inhibitory concentrations as low as 6mg/L were observed, for instance against clinical isolates of Escherichia coli and Acinetobacter baumannii. In comparison, neither the free antibiotic nor VAN-loaded ‘classical’ (non-fusogenic) liposomes showed any activity against the same bacteria. Scanning and transmission electron microscopy studies allowed confirmation that the produced SUVETs were able to adhere to and fuse with the external membrane of E. coli. According to preliminary experiments, this technological strategy can be proposed as a potentially successful way to enlarge the spectrum of activity of VAN.

Class-dependent relevance of tissue distribution in the interpretation of anti-infective pharmacokinetic/pharmacodynamic indices - Corrected Proof

April Barbour, Francesco Scaglione, Hartmut Derendorf — 2010-03-11

Abstract: The pharmacokinetic/pharmacodynamic (PK/PD) indices useful for predicting antimicrobial clinical efficacy are well established. The most common indices include the time free drug concentration in plasma is above the minimum inhibitory concentration (MIC) (fT>MIC) expressed as a percent of the dosing interval, the ratio of maximum concentration to MIC (Cmax/MIC), and the ratio of the area under the 24-h concentration–time curve to MIC (AUC0–24/MIC). A single PK/PD index may correlate well with an entire antimicrobial class. For example, the β-lactams correlate well with the fT>MIC. However, other classes may be more complex and a single index cannot be generalised to the class, e.g. the macrolides. The rationale behind which PK/PD index best correlates with efficacy depends on several factors, including the mechanism of action, the microbial kill kinetics, the degree of protein binding and the degree of tissue distribution. Studies have traditionally emphasised the first two factors, whilst the significance of protein binding and tissue distribution is increasingly appreciated. In fact, the latter two factors may partially elucidate why the magnitude of reported target indices are not always as expected. For example, tigecycline and telithromycin are clinically efficacious with average serum concentrations below their MICs over a 24-h period. Therefore, to understand more fully the PK/PD relationship of antibiotics and to better predict the clinical efficacy of antibiotic dosing regimens, assessment of free drug concentrations at the site of action is warranted.

Resistance to oral antibiotics in urinary coliform strains isolated between 2000 and 2008 in Sønderborg area, Denmark - Corrected Proof

Zefiryn Cybulski, Poul Kjaeldgaard — 2010-03-08

Coliform organisms, particularly Escherichia coli, are the predominant cause both of community and nosocomial urinary tract infection (UTIs) . Currently, mecillinam, sulfamethizole and trimethoprim are recommended as the first-line treatment in Denmark . The purpose of this study was to examine the antimicrobial susceptibility of urinary coliform isolates to currently recommended oral antimicrobial treatment in a well-defined geographical area in Denmark.

In vitro combined activity of amphotericin B, caspofungin and voriconazole against clinical isolates of Trichosporon asahii - Corrected Proof

Houmin Li, Qiaoyun Lu, Zhe Wan, Jianzhong Zhang — 2010-03-08

Abstract: Disseminated infections caused by Trichosporon asahii are difficult to resolve. Combination regimens with synergistic drugs could provide additional options for treating trichosporonosis. The aim of this study was to evaluate the antifungal activities of voriconazole (VCZ), caspofungin (CAS) and amphotericin B (AMB) alone or in combination in vitro against clinical isolates of T. asahii. The combined antifungal activities of VCZ, CAS and AMB against 18 clinical isolates were assessed by a chequerboard microdilution method. CAS combined with AMB showed the highest percentage of synergistic effects (89%), much higher than those of the other two combinations (AMB/VCZ and CAS/VCZ both 17%). No antagonistic effect was observed in any case. This study demonstrates that the activity of two combined antifungals, especially the combination of CAS and AMB, against T. asahii is more effective than that of a drug alone against this fungus, suggesting that combined antifungal therapy may be a potential strategy for treating disseminated trichosporonosis.

In vivo efficacy of the antimicrobial peptide ranalexin in combination with the endopeptidase lysostaphin against wound and systemic meticillin-resistant Staphylococcus aureus (MRSA) infections - Corrected Proof

Andrew P. Desbois, Curtis G. Gemmell, Peter J. Coote — 2010-03-08

Abstract: New treatments are urgently required for infections caused by meticillin-resistant Staphylococcus aureus (MRSA) as these strains are often resistant to multiple conventional antibiotics. Earlier studies showed that ranalexin, an antimicrobial peptide (AMP), in combination with lysostaphin, an antistaphylococcal endopeptidase, synergistically inhibits the growth of MRSA, meaning that it deserved consideration as a new anti-S. aureus therapy. Using haemolysis and Vero cell viability assays, ranalexin with lysostaphin is proven to be non-toxic at antibacterial concentrations. In human serum, ranalexin with lysostaphin is significantly more effective against MRSA than treatment with either component alone. In a rabbit model of wound infection, ranalexin with lysostaphin reduced MRSA in the wound by ca. 3.5log10 colony-forming units (CFU) compared with the untreated control. The combination is significantly more effective than treatment with ranalexin or lysostaphin alone. In a mouse model of systemic infection, ranalexin with lysostaphin reduced MRSA kidney burden by ca. 1log10CFU/g compared with untreated controls or treatment with ranalexin or lysostaphin alone. Importantly, the combination is synergistically bactericidal against various S. aureus isolates in vitro, including those with reduced susceptibility to lysostaphin or vancomycin. Ranalexin and lysostaphin could be incorporated in wound dressings for the prevention and treatment of topical S. aureus infections. That AMPs can enhance the antibacterial effectiveness of lysostaphin in vivo highlights a new avenue of research in the fight against drug-resistant staphylococci.

Pharmacokinetics of garenoxacin in elderly patients with respiratory tract infections - Corrected Proof

2010-03-08

Abstract: The pharmacokinetics of the new oral des-fluoroquinolone antimicrobial garenoxacin (GRNX) was investigated in elderly patients with respiratory tract infections. Patients were treated with GRNX (200mg or 400mg) once daily for 7 days. Plasma GRNX concentrations were determined and pharmacokinetic parameters were estimated by Bayesian predictions using reported population pharmacokinetic parameters. At each dose, the maximum plasma concentration (Cmax) and the area under the concentration–time curve (AUC) were comparable with those reported in young subjects, except that the estimated Cmax and AUC values in one patient receiving the 200mg dose whose body weight and creatinine clearance rate (CLCr) were 38kg and 17mL/min, respectively, were higher than those of the other patients given 200mg GRNX and were comparable with those of patients who received the 400mg dose. These results suggest that the recommended dose of GRNX should be 400mg for most elderly and young patients, but only 200mg in patients whose body weight and CLCr are <40kg and <30mL/min, respectively.

Detection of the first two Klebsiella pneumoniae isolates with sequence type 258 producing KPC-2 carbapenemase in Denmark - Corrected Proof

2010-03-08

The first findings of carbapenemase-producing Klebsiella pneumoniae isolates have recently been described in Sweden, Norway and Finland . After the other Nordic reports, we have characterised the first two carbapenemase-producing K. pneumoniae isolates obtained from Danish patients.

Rapid induction of resistance to the fluoroquinolone enrofloxacin in Pseudomonas putida NCTC 10936 - Corrected Proof

2010-03-08

Fluoroquinolones are considered essential antibiotics both for human and animal health care . The fluoroquinolone enrofloxacin is often used in the agricultural setting and rapid development of resistance has been observed . Some microorganisms are known to acquire fluoroquinolone resistance by a single mutation in the gyrA gene, whilst others require several mutations . As expected, species belonging to the genera Campylobacter and Pseudomonas, which require a single mutation, become resistant faster than Escherichia coli and Salmonella spp. that need several. This study addresses the following question: what levels of exposure of Pseudomonas putida to a fluoroquinolone lead to what increase in resistance and on what time scale?

Panton–Valentine leukocidin-producing Staphylococcus aureus necrotising pneumonia: measuring toxin levels in microbiological samples to attest of linezolid clinical efficacy - Corrected Proof

P. Pasquier, V. Muller, T. Villevieille, J.M. Rousseau, F. Janvier, J. Etienne — 2010-03-08

We read with interest the short communication by Yanagihara et al. addressing the efficacy of linezolid against Panton–Valentine leukocidin (PVL)-producing Staphylococcus aureus in a mouse model. In human practice, PVL-positive S. aureus is responsible for necrotising pneumonia in immunocompetent adults, with a high mortality rate (56–75%) .

Macrolide-resistant Streptococcus pyogenes in Central Greece: prevalence; mechanism and molecular identification - Corrected Proof

2010-03-08

Streptococcus pyogenes [group A Streptococcus (GAS)] is the most common bacterial agent implicated in acute tonsillopharyngitis and can also cause a variety of skin and soft-tissue infections and severe invasive disease. Macrolides constitute an alternative choice for the treatment of streptococcal tonsillopharyngitis and other respiratory tract infections, especially valuable in patients allergic to β-lactams.

Antimicrobial characterisation of CEM-101 activity against respiratory tract pathogens, including multidrug-resistant pneumococcal serogroup 19A isolates - Corrected Proof

2010-03-08

Abstract: CEM-101 is a novel fluorinated macrolide–ketolide with potent activity against bacterial pathogens that are susceptible or resistant to other macrolide–lincosamide–streptogramin B (MLSB)–ketolide agents. CEM-101 is being developed for oral and parenteral use in moderate to moderately severe community-acquired bacterial pneumonia. The objective of this study was to assess the activity of CEM-101 and comparators against contemporary respiratory tract infection (RTI) isolates. A worldwide sample of organisms was used, including Streptococcus pneumoniae [n=168; 59.3% erythromycin-resistant and 18 multidrug-resistant (MDR) serogroup 19A strains], Moraxella catarrhalis (n=21; 11 β-lactamase positive), Haemophilus influenzae (n=100; 48 β-lactamase positive), Haemophilus parainfluenzae and Haemophilus haemolyticus (n=12), and Legionella pneumophila (n=30). Testing and interpretation were performed using reference Clinical and Laboratory Standards Institute methods. CEM-101 was very potent against S. pneumoniae [minimum inhibitory concentration for 90% of the organisms (MIC90)=0.25mg/L; highest MIC at 0.5mg/L] and was 2- and ≥32-fold more active than telithromycin and clindamycin, respectively. CEM-101 also demonstrated potent activity against S. pneumoniae MDR-19A strains (MIC90=0.5mg/L). CEM-101 was the most potent antimicrobial agent tested against L. pneumophila, with all MIC values at ≤0.015mg/L (telithromycin MIC90=0.03mg/L). CEM-101 was as potent as azithromycin against Haemophilus spp. RTI pathogens (MIC90=2mg/L), with no variations for β-lactamase production. CEM-101 MIC values against M. catarrhalis were all at ≤0.5mg/L. Interestingly, CEM-101 potency was ca. 6log2 dilutions greater than telithromycin MIC results among 44 β-haemolytic streptococci having telithromycin MICs ≥2mg/L. CEM-101 exhibited the greatest potency and widest spectrum of activity against RTI pathogens among the tested MLSB–ketolide agents (azithromycin, clarithromycin, erythromycin, telithromycin, clindamycin and quinupristin/dalfopristin) and was comparable overall with levofloxacin.

Minocycline versus doxycycline for meticillin-resistant Staphylococcus aureus (MRSA): in vitro susceptibility versus in vivo effectiveness - Corrected Proof

Burke A. Cunha — 2010-03-04

Since meticillin-resistant Staphylococcus aureus (MRSA) became widespread in the 1970s it was appreciated that with hospital-acquired MRSA (HA-MRSA) there was a disconnection between in vitro susceptibility testing and in vivo clinical efficacy . Patients with MRSA were treated with antibiotics, e.g. cephalosporins, that appeared to be active in vitro but in vivo were clinically ineffective. Subsequently, this was also shown to be the case for fluoroquinolones with MRSA .

First description of Klebsiella pneumoniae clinical isolates carrying both qnrA and qnrB genes in Portugal - Corrected Proof

2010-03-04

Abstract: In the present study, 21 multidrug-resistant Klebsiella pneumoniae isolates were recovered from patients hospitalised in the Intensive Care Unit of Hospital Infante D. Pedro in Aveiro, Portugal. Fifteen isolates carried qnr genes. Four strains harboured the quinolone resistance genes qnrA and qnrB, both located on a large plasmid in two strains (KP4 and KP10) and on different plasmids in two strains (KP5 and KP6). These findings indicate an extremely high prevalence of qnr genes associated with various mobile elements such as ISCR1 and class 1 integrons.

Clonal spread in Eastern Asia of ciprofloxacin-resistant Escherichia coli serogroup O25 strains, and associated virulence factors - Corrected Proof

2010-03-02

Abstract: A significant problem in the field of infectious diseases is the increase in fluoroquinolone (FQ)-resistant Escherichia coli. Although mutation of strains and clonal dissemination are supposed to be the cause of this increase, little is known about the prevalence of this organism. We investigated 219 FQ-resistant E. coli strains in Japan and nine Asian countries by serotyping and genotyping. Seventy-one strains (32.4%) were serogroup O25, which was prevalent in South Korea, China and Japan, especially in the southwest part of Japan. Aerobactin, a virulence factor in uropathogenic and avian pathogenic E. coli, was associated with the presence of FQ-resistant O25 strains of E. coli. Seven of the seventy-one FQ-resistant E. coli O25 had extended-spectrum β-lactamase genes (six CTX-M-14 and one SHV-12), however, we were unable to find any E. coli O25-ST131 clone that produced CTX-M-15, which was previously reported to have emerged across continents. These data demonstrate that a clonal group of FQ-resistant and virulent E. coli recently became prevalent at least in East Asia and suggest that this might become a public health problem because the strains may acquire resistance to other antimicrobial agents.

In vitro activity of biapenem against Burkholderia pseudomallei - Corrected Proof

Visanu Thamlikitkul, Suwanna Trakulsomboon — 2010-03-02

Burkholderia pseudomallei, a Gram-negative bacterium, causes the disease melioidosis in humans and animals . The bacterium is a soil organism found mainly in Southeast Asia and Northern Australia. Antibiotics currently recommended for therapy of melioidosis are ceftazidime, imipenem, meropenem, amoxicillin/clavulanic acid, trimethoprim/sulfamethoxazole, doxycycline and chloramphenicol . Development of resistance of B. pseudomallei to the aforementioned antibiotics has been recognised , therefore a search for new agents effective against B. pseudomallei is required.

Safety and pharmacokinetics of oseltamivir at standard and high dosages - Corrected Proof

R. Dutkowski, J.R. Smith, B.E. Davies — 2010-03-02

Abstract: Although clinical evidence is currently lacking, opinion in the literature on avian influenza A/H5N1 suggests that increased doses of the oral neuraminidase inhibitor oseltamivir may offer clinical benefits against highly pathogenic influenza where high levels of viral replication and disseminated infection cause severe disease. We assessed the pharmacokinetics and safety/tolerability of oseltamivir at dosages up to 450mg twice daily. Healthy adult volunteers were randomised to receive placebo or oseltamivir 75, 225 or 450mg every 12h for 5 days. Volunteers were followed up to Day 7 for pharmacokinetic parameters, vital signs, adverse events and cardiac safety. In total, 391 volunteers were randomised and evaluated. Pharmacokinetics were linear and dose-proportional, with no evidence of accumulation of oseltamivir or its active metabolite at any dosage. Headache was the most common adverse event (16.8–23.7% across groups), but its incidence was unrelated to dosage. Dosage-related events with oseltamivir included nausea (up to 31.3% of volunteers) and vomiting (up to 16.2%), which generally occurred on Day 1 and lasted <1 day, and possibly dizziness (up to 11.3%). Oseltamivir had no relevant effects on vital signs, laboratory parameters or cardiac function. In conclusion, oseltamivir was well tolerated, with dose-proportional pharmacokinetics and no accumulation. Possible clinical benefit in severe influenza infections could be investigated at dosages higher than those currently recommended.

Emergence of AcrAB-mediated tigecycline resistance in a clinical isolate of Enterobacter cloacae during ciprofloxacin treatment - Corrected Proof

2010-03-02

Abstract: Tigecycline resistance remains rare amongst Enterobacteriaceae in the UK, as elsewhere, but has been associated with upregulation of the AcrAB efflux system. Using isolates of an Enterobacter cloacae strain that developed tigecycline resistance in vivo during ciprofloxacin therapy as well as laboratory-selected mutants, we investigated the role of this pump and the global regulator RamA in tigecycline resistance. Laboratory mutants were selected from a susceptible clinical isolate in vitro by exposure to increasing concentrations of tigecycline. Expression of the acrAB operon and the ramA gene was monitored by real-time reverse-transcription polymerase chain reaction (RT-PCR). Overexpression of ramA was achieved using the pBAD expression vector, whilst insertional inactivation of acrB with a gentamicin resistance cassette was achieved with the bacteriophage λ Red recombination system. Increased tigecycline minimum inhibitory concentrations in the clinical isolate and a laboratory mutant were associated with increases in acrAB and ramA transcripts. Induction of increased ramA expression resulted in increased acrAB expression, whilst insertional inactivation of acrB restored full susceptibility to tigecycline. Treatment with ciprofloxacin, a substrate of AcrAB in E. cloacae, possibly selected for cross-resistance to tigecycline as a result of RamA-mediated AcrAB upregulation.

2-Chloroadenosine (2-CADO) treatment modulates the pro-inflammatory immune response to prevent acute lung inflammation in BALB/c mice suffering from Klebsiella pneumoniae B5055-induced pneumonia - Corrected Proof

Vijay Kumar, Kusum Harjai, Sanjay Chhibber — 2010-03-02

Abstract: Acute lung inflammation (ALI) is a life-threatening pathology and can develop during the course of several clinical conditions such as pneumonia, acid aspiration or sepsis. Adenosine plays a significant role in controlling acute inflammation via binding to A2A receptors on inflammatory cells, i.e. neutrophils or macrophages. The present study was designed to evaluate the anti-inflammatory and immunomodulatory effects of 2-chloroadenosine (2-CADO), alone or in combination with amoxicillin/clavulanic acid (AMC), in Klebsiella pneumoniae B5055-induced acute lung infection in mice. Acute lung infection in mice was induced by directly instilling the selected dose (104 colony-forming units/mL) of bacteria intranasally. Histopathological examination of the lungs was performed to reveal neutrophil infiltration into the lung alveoli. In addition to the major pro-inflammatory cytokines tumour necrosis factor-alpha (TNFα) and interleukin (IL)-1α, levels of the anti-inflammatory cytokine IL-10 were also determined. Intranasal instillation of bacteria caused profound neutrophil infiltration into the lung alveoli as well as a significant increase in the levels of pro-inflammatory mediators (i.e. TNFα and IL-1α). However, intravenous administration of 2-CADO 10μg/kg/day, alone or in combination with an antibiotic (i.e. AMC), significantly decreased neutrophil infiltration into the lung alveoli. A significant decrease in TNFα and IL-1α along with elevation of IL-10 levels in the lung homogenate of mice with acute lung infection was observed upon treatment with 2-CADO alone, with no significant decrease in bacterial counts. Moreover, in combination with AMC, 2-CADO exhibited its immunomodulatory action in acute lung infection and prevented ALI, whilst an antibacterial action was exhibited by AMC.

In vitro activities of fosfomycin and carbapenem combinations against carbapenem non-susceptible Escherichia coli and Klebsiella pneumoniae - Corrected Proof

Thidarat Netikul, Amornrut Leelaporn, Pattarachai Kiratisin, Amorn Leelarasmee — 2010-03-02

Decreased susceptibility to carbapenems among multidrug-resistant (MDR) Enterobacteriaceae contributes to higher mortality rates and seriously limits treatment options . Fosfomycin has been shown to be active against MDR Enterobacteriaceae, including carbapenem non-susceptible isolates . In this study, we investigated combinations of fosfomycin and various carbapenems against Escherichia coli and Klebsiella pneumoniae isolates with decreased susceptibility to carbapenems to determine whether the combinations may have enhanced antimicrobial activities based on the in vitro Etest.

Therapeutic drug monitoring of β-lactams for critically ill patients: unwarranted or essential? - Corrected Proof

Jason A. Roberts, William W. Hope, Jeffrey Lipman — 2010-03-02

Approximately 50% of Intensive Care Unit (ICU) patients have an infection requiring treatment with antibiotics . The associated morbidity and mortality mean that infection in the ICU remains a significant public health problem. Management is further compounded by widespread and rapidly increasing antimicrobial resistance . In the intensive care environment, methods to optimise infection-related patient outcomes and to minimise the development of antibiotic resistance are urgently required. One strategy is to personalise therapy to attain drug exposures associated with a high probability of therapeutic success and with suitably low probabilities of toxicity and generation of antibiotic resistance.

Potential of doripenem for the treatment of infections with multidrug-resistant Pseudomonas spp. - Corrected Proof

R. Naesens, H. Jansens, H. Goossens, M. Ieven, E. Vlieghe — 2010-02-26

We read with interest the article by Fujimura et al. reporting the susceptibility of Pseudomonas aeruginosa clinical isolates from Japan, focusing on the in vitro activity of doripenem. Since therapeutic options for infections with multidrug-resistant (MDR) Pseudomonas spp. are scarce, as the author mentioned, and are often limited to colistin, we were interested in the possible future role of doripenem for the treatment of these infections . We therefore collected 27 clinically relevant consecutive Pseudomonas spp. strains from University Hospital Antwerp (Belgium), a tertiary care hospital, that were resistant to amikacin, fluoroquinolones and all routinely tested β-lactams (cefepime, ceftazidime, piperacillin/tazobactam and meropenem). Only one isolate per patient was included. Susceptibility testing was performed by disk diffusion testing using Clinical and Laboratory Standards Institute (CLSI) breakpoints . Minimum inhibitory concentrations (MICs) for meropenem and doripenem were subsequently determined using the CLSI reference broth microdilution method . Quality control was performed using P. aeruginosa ATCC 27853, which was between reference values . For both meropenem and doripenem, the MIC90 (MIC for 90% of the organisms) of the collected strains was >64mg/L. The MIC50 (MIC for 50% of the organisms) was also identical for the two antibiotics tested (64mg/L) (). None of the strains collected was sensitive according to CLSI criteria (susceptible ≤4mg/L; resistant >8mg/L) . Only marginal differences in MICs of meropenem versus doripenem were found, with a maximal difference of only two dilutions (). In case of such high MICs, these differences were not sufficient to consider treatment with doripenem in infections with MDR Pseudomonas spp. We conclude that, as Fujimura et al. also mentioned, although doripenem is one of the most potent and promising antipseudomonal drugs, in vitro results from our hospital suggest no role of doripenem in the treatment of infections with MDR Pseudomonas spp.

Thioridazine cures extensively drug-resistant tuberculosis (XDR-TB) and the need for global trials is now! - Corrected Proof

2010-02-26

Abstract: Thioridazine (TDZ) has been shown to have in vitro activity against multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis, to promote the killing of intracellular MDR and XDR strains and to cure the mouse of antibiotic-susceptible and -resistant pulmonary tuberculosis (TB) infections. Recently, TDZ was used to cure 10 of 12 XDR-TB patients in Buenos Aires, Argentina. At the time of writing, it is being used for the therapy of non-antibiotic-responsive terminal XDR-TB patients in Mumbai, India, on the basis of compassionate therapy and although it is too early to determine a cure, the patients have improved appetite, weight gain, are afebrile and free of night sweats, and their radiological picture shows great improvement. Because XDR-TB is essentially a terminal disease in many areas of the world and no new effective agents have yet to yield successful clinical trials, global clinical trials for the therapy of XDR-TB are urgently required.

Swine influenza (H1N1) pneumonia: elevated serum procalcitonin levels not due to superimposed bacterial pneumonia - Corrected Proof

Burke A. Cunha, Uzma Syed, Stephanie Strollo — 2010-02-26

The swine influenza (H1N1) pandemic has affected primarily young healthy adults . Early death due to swine influenza (H1N1), similar to avian influenza (H5N1), has been due primarily to respiratory failure/acute respiratory distress syndrome (ARDS) . Human influenza A pandemics have also been complicated by simultaneous (Staphylococcus aureus) or sequential (Streptococcus pneumoniae or Haemophilus influenza) bacterial community-acquired pneumonia (CAP) . In infiltrating pneumonia with bilateral CAP, the chest radiograph (CXR) is usually clear or with accentuation of basal lung markings, although later bilateral patchy interstitial infiltrates may develop.

Drug resistance patterns in Salmonella enterica subspecies enterica serotype Typhi strains isolated over a period of two decades, with special reference to ciprofloxacin and ceftriaxone - Corrected Proof

Gopal Nath, Pushpa Maurya — 2010-02-26

Abstract: Fluoroquinolone-resistant Salmonella enterica subspecies enterica serotype Typhi are being increasingly reported from the Asian subcontinent. This has been hypothesised to be due to a double mutation in the gyrA gene. A total of 113 S. Typhi strains isolated during 1987–2006 in a tertiary-level hospital of North India were monitored for their antibiotic susceptibility by the disk diffusion and minimum inhibitory concentration (MIC) methods. The study period was arbitrarily divided into four equal parts, each comprising 5 years. The antibiotics tested showed an extremely wide range of MICs during all four periods except for ceftriaxone, which showed no resistance during the study period. However, a gradual increase in the MIC of this drug was observed, i.e. 0.047mg/L, 0.098mg/L, 0.211mg/L and 0.3652mg/L during the four study periods. Ninety-one percent of the strains isolated in the final study period were observed to have MIC levels ≥0.125mg/L to ciprofloxacin. Furthermore, gyrA restriction analysis showed no mutation at the two reported sites of the gene, suggesting that the double mutation theory in the development of ciprofloxacin resistance may not be the only mechanism responsible for fluoroquinolone resistance.

Monitoring plasma voriconazole levels following intravenous administration in critically ill patients: an observational study - Corrected Proof

2010-02-26

Abstract: Data relating to the pharmacokinetics of voriconazole in critically ill patients are lacking. A prospective observational study was conducted on 18 non-consecutive critically ill patients aged 24–97 years, comprising 12 patients with normal renal function (NRF) [creatinine clearance (CLCr) ≥60mL/min] and 6 patients with moderate renal impairment (MRI) (CLCr 40–55mL/min), administered voriconazole intravenously (6mg/kg loading dose and 3–4mg/kg twice daily thereafter) in order to determine the suitability of these doses in this patient population. Steady-state blood levels were monitored and liver and renal function were recorded throughout treatment. Large variability in patient plasma levels was observed, ranging from 37% at ≤1mg/L (minimum inhibitory concentration at which, for most fungal pathogens, 90% of isolates are susceptible) to 19% at >5.5mg/L. Moreover, maintaining trough concentrations above clinical breakpoints was not consistently achieved because 16/30 (53%) were ≤1mg/L. In a few MRI patients, average concentrations were found to be significantly different compared with those of NRF patients administered the same dose, however this difference was not noted in pharmacokinetic parameters following dose normalisation. None of the patients experienced deterioration in renal or liver function. Recommended voriconazole doses are inadequate to achieve drug concentrations >1μg/mL over the entire dosing interval in some critically ill patients.

Antimicrobial susceptibility of Neisseria gonorrhoeae isolates determined by the agar dilution, disk diffusion and Etest methods: comparison of results using GC agar and chocolate agar - Corrected Proof

2010-02-26

Abstract: Although the use of GC agar for determining Neisseria gonorrhoeae antimicrobial susceptibilities is suggested by Clinical and Laboratory Standard Institute (CLSI) guidelines, chocolate agar is still used in some regions owing to its low cost and availability. To determine the differences in susceptibilities determined using GC and chocolate agars, 163 non-duplicate N. gonorrhoeae isolates were tested. Minimum inhibitory concentrations (MICs) and percent susceptibilities determined using the GC agar dilution method, respectively, were as follows: ceftriaxone, 0.004–0.125mg/L, 100%; cefixime, 0.002mg/L to >32mg/L, 98.2%; and ciprofloxacin, 0.002mg/L to >32mg/L, 3.1%. Comparison of ceftriaxone MICs determined by the Etest using GC agar and chocolate agar showed that use of GC agar tended to result in lower MICs than GC agar dilution, whilst use of chocolate agar tended to result in higher MICs (concordance, 55.8% and 82.8%, respectively). Disk inhibition zones obtained using GC agar and chocolate agar (and their correlation coefficients) were, respectively: ceftriaxone, 35–55mm and 25–50mm (0.46); ciprofloxacin, 6–55mm and 6–43mm (0.84); and penicillin, 6–47mm and 6–50mm (0.93). Use of chocolate agar with the disk diffusion method for ceftriaxone was associated with a 5.5% false resistance rate. In summary, compared with GC agar, susceptibility testing using chocolate agar tends to yield higher MICs with the Etest and smaller disk inhibition zones with disk diffusion methods. Clinical microbiology laboratories should strictly adhere to CLSI recommendations by using GC agar instead of chocolate agar when performing susceptibility testing for N. gonorrhoeae.

Penetration of doripenem into prostatic tissue following intravenous administration in prostatectomy patients - Corrected Proof

2010-02-26

Abstract: This study examined the prostatic penetration of doripenem in prostatectomy patients. Doripenem 500mg was administered by a 0.5-h infusion and venous blood and prostatic tissue samples were obtained up to 5h afterwards. Drug concentrations in plasma and prostatic tissue were measured chromatographically. The observed maximum concentration (Cmax) (mean±standard deviation; n=9) was 27.5±5.1μg/mL in plasma and 5.09±1.94μg/g in prostate tissue and the prostate/plasma Cmax ratio was 0.189±0.078. The area under the drug concentration–time curve (AUC) was 49.7±6.9μgh/mL in plasma and 3.93±1.89μgh/g in prostate tissue and the prostate/plasma AUC ratio was 0.081±0.047. Based on a three-compartment pharmacokinetic analysis, average drug exposure times above 0.25μg/mL (the minimum inhibitory concentration for isolates of common pathogens) in the prostate were 23.2% for 500mg once daily, 46.2% for 500mg twice daily and 69.9% for 500mg three times daily. The 500-mg regimens all achieved the drug exposure time target (bacteriostatic 20% or bactericidal 40%) in the prostate, despite the relatively low penetrability of doripenem.

Genetic environment of sul genes and characterisation of integrons in Escherichia coli isolates of blood origin in a Spanish hospital - Corrected Proof

2010-02-26

Abstract: The prevalence and characterisation of integrons and the genetic environment of sulphonamide resistance genes were studied in 135 Escherichia coli isolates recovered from blood cultures in a Spanish hospital during 2007. Class 1 and 2 integrons were identified in 54 isolates (intI1, 52 isolates; intI2, 1 isolate; and intI1+intI2, 1 isolate). Of the 53 intI1-positive isolates, 36 (67.9%) contained the classic class 1 integron including the qacEΔ1–sul1 region, and 11 different gene cassette arrangements were demonstrated in 33 of these isolates. Seventeen intI1-positive isolates lacked the qacEΔ1–sul1 region, and 8 gene cassette arrangements were demonstrated in 12 of these isolates. Seventy-one isolates showed a sulphonamide-resistant phenotype, 63 of which contained sul genes. The sul1 gene was associated with intI1 in 36 of 42 sul1-positive isolates, and the sul3 gene was associated with non-classic class 1 integrons in 5 of 7 sul3-positive isolates. Finally, sul2 was found associated with strA–strB genes in 32 of 35 sul2-positive isolates, identifying 11 genetic structures, 1 of them presenting the IS150 element disrupting the strB gene; this structure was included in GenBank with accession no. FJ705354. Almost one-half of the E. coli isolates from blood cultures contained integrons and sul genes. Moreover, sul genes were detected in different structures, one of them new, and could be important determinants in antibiotic resistance dissemination.

Molecular epidemiology and mechanisms of carbapenem resistance in Pseudomonas aeruginosa isolates from Chinese hospitals - Corrected Proof

2010-02-25

Abstract: We investigated the molecular epidemiology and carbapenem resistance mechanisms of 258 non-duplicate carbapenem-resistant clinical isolates of Pseudomonas aeruginosa collected from 2006 to 2007 at 28 hospitals in China. Up to 88% of the carbapenem-resistant isolates were multidrug-resistant. Pulsed-field gel electrophoresis (PFGE) revealed that levels of intrahospital and interhospital dissemination of clones were low. To assess the mechanisms leading to resistance, all 258 carbapenem-resistant isolates were analysed for expression of the chromosomal β-lactamase (AmpC), the porin important for entry of carbapenems (OprD) and an efflux system (MexAB-OprM) known to extrude some β-lactams. Carbapenem resistance was driven mainly by mutational inactivation of OprD, accompanied or not by hyperexpression of AmpC or MexAB-OprM. Metallo-β-lactamase genes were detected in 22 carbapenem-resistant isolates in China, belonging to eight pulsotypes. The blaOXA-50 gene was detected among all of the carbapenem-resistant isolates, whereas the blaGES-5 gene was detected in only one carbapenem-resistant isolate.

Free concentration and protein-binding ratio of ceftriaxone in cerebrospinal fluid in paediatric patients with purulent meningitis caused by Haemophilus influenzae type b - Corrected Proof

Tadashi Hoshino, Naruhiko Ishiwada, Yoichi Kohno — 2010-02-25

Ceftriaxone (CRO), which penetrates well into the cerebrospinal fluid (CSF), is recommended as the antibiotic of choice for empirical and specific therapy of bacterial meningitis in children . However, there is concern that treatment failure may occur with antibiotics having a high protein-binding ratio, such as CRO, since bactericidal activity is achieved by unbound drug at the site of infection . There have been numerous reports of good total concentrations in CSF but few reports on free concentrations. Therefore, in the present study, free CRO concentrations and protein-binding ratios in CSF were examined to enhance our understanding of the clinical efficacy of CRO against bacterial meningitis.

Resistance to rifampicin: at the crossroads between ecological, genomic and medical concerns - Corrected Proof

2010-02-25

Abstract: The first antibiotic of the ansamycin family, rifampicin (RIF), was isolated in 1959 and was introduced into therapy in 1962; it is still a first-line agent in the treatment of diseases such as tuberculosis, leprosy and various biofilm-related infections. The antimicrobial activity of RIF is due to its inhibition of bacterial RNA polymerase (RNAP). Most frequently, bacteria become resistant to RIF through mutation of the target; however, this mechanism is not unique. Other mechanisms of resistance have been reported, such as duplication of the target, action of RNAP-binding proteins, modification of RIF and modification of cell permeability. We suggest that several of these alternative resistance strategies could reflect the ecological function of RIF, such as autoregulation and/or signalling to surrounding microorganisms. Very often, resistance mechanisms found in the clinic have an environmental origin. One may ask whether the introduction of the RIF analogues rifaximin, rifalazil, rifapentine and rifabutin in the therapeutic arsenal, together with the diversification of the pathologies treated by these molecules, will diversify the resistance mechanisms of human pathogens against ansamycins.

Significance of individual adjustment of initial loading dosage of teicoplanin based on population pharmacokinetics - Corrected Proof

2010-02-25

Abstract: An initial loading dose of teicoplanin is required to reach the optimal trough concentration (≥10μg/mL) rapidly. To attain the optimal teicoplanin concentration efficiently, an individual loading dose regimen based on population pharmacokinetics, in which the target trough concentration was set to 15μg/mL, was defined. Among 70 patients, 33 patients received the individual loading dose regimen, 33 patients received the conventional loading dose regimen (200mg or 400mg every 12h on Day 1 followed by 200mg once daily) and 4 patients received no loading dose. The proportion of patients showing an optimal plasma concentration was 88% in the individual loading dose regimen but only 33% in the conventional loading dose regimen. No patient without a loading dose showed the optimal concentration. Both total loading dose and plasma concentration were significantly (P<0.001) higher in the individual loading dose group than in the conventional loading dose group. Notably, the trough concentration was almost constant in patients with individual loading doses ranging from 800mg to 1800mg. These findings suggest that individual adjustment of the initial loading dose of teicoplanin is potentially useful to attain the optimal concentration rapidly.

In vitro prevention of the emergence of daptomycin resistance in Staphylococcus aureus and enterococci following combination with amoxicillin/clavulanic acid or ampicillin - Corrected Proof

José M. Entenza, Marlyse Giddey, Jacques Vouillamoz, Philippe Moreillon — 2010-02-25

Abstract: Daptomycin is bactericidal against meticillin-resistant Staphylococcus aureus (MRSA), glycopeptide-intermediate-resistant S. aureus (GISA) and vancomycin-susceptible and -resistant enterococci. However, selection for daptomycin-resistant derivatives has occasionally been reported during therapy in humans. Here we evaluate whether selection for daptomycin-resistant S. aureus or enterococci could be prevented in vitro by combining daptomycin with amoxicillin/clavulanic acid, ampicillin, gentamicin or rifampicin. Six strains of S. aureus (four MRSA and two GISA) and four strains of enterococci (two Enterococcus faecalis and two Enterococcus faecium) were serially exposed in broth to two-fold stepwise increasing concentrations of daptomycin alone or in combination with a fixed concentration [0.25× minimum inhibitory concentration (MIC)] of either of the second agents. The daptomycin MIC was examined after each cycle. Exposure to daptomycin alone gradually selected for S. aureus and enterococci with an increased MIC. Gentamicin did not prevent the emergence of daptomycin-resistant bacteria. Rifampicin was also unable to prevent daptomycin resistance, although resistance was slightly delayed. In contrast, amoxicillin/clavulanic acid or ampicillin prevented or greatly delayed the selection of daptomycin-resistant mutants in S. aureus and enterococci, respectively. Addition of amoxicillin/clavulanic acid or ampicillin to daptomycin prevents, or greatly delays, daptomycin resistance in vitro. Future studies in animal models are needed to predict the utility of these combinations in humans.

Treatment options for 2009 H1N1 influenza: evaluation of the published evidence - Corrected Proof

2010-02-25

Abstract: We evaluated the evidence regarding the effectiveness of various treatment strategies used for 2009 H1N1 influenza by reviewing available relevant studies. In total, 22 studies (15 cohort studies involving >10 patients, 5 cohort studies with ≤10 patients and 2 case reports) were included. A total of 3020 patients [1068 (35.4%) critically ill, 1722 (57.0%) hospitalised and 230 (7.6%) outpatients, including 909 (30.1%) children] were involved. Notably, 487 (16.1%) were obese [body mass index (BMI) >30)], 362 (12.0%) had asthma or chronic obstructive pulmonary disease and 255 (8.4%) were pregnant. Antiviral treatment was administered to 1622 patients (53.7%), of whom 661 (40.8%) received oseltamivir monotherapy. Corticosteroids were administered in 323 (31.8%) of 1016 patients for whom relevant data were available. Similarly, 633 (85.0%) of 745 patients received antibiotics. Comparative data from the largest included study (involving 1088 patients) indicated that administration of antivirals within 2 days from symptom onset was significantly associated with reduced mortality (P<0.001). In summary, the scarcity of comparative available data hampered the establishment of any firm conclusions regarding the benefit that various treatment strategies may confer to patients with 2009 H1N1 influenza. Studies with a comparative design, as well as randomised studies are needed to clarify further this issue of major importance.

Maintenance haemodialysis and delayed administration of appropriate antibiotics increase 30-day mortality among patients with non-hospital-acquired meticillin-resistant Staphylococcus aureus bacteraemia - Corrected Proof

2010-02-24

Sir, Clinical information is limited regarding the outcome of patients with non-hospital-acquired meticillin-resistant Staphylococcus aureus (NHA-MRSA) infections, particularly those undergoing maintenance haemodialysis on an outpatient basis who are prone to healthcare-associated S. aureus infections. Moreover, NHA-MRSA is of rising clinical significance because of the potential development of life-threatening bacteraemia and fatal outcome in otherwise healthy persons .

Differences in carbapenem resistance genes among Acinetobacterbaumannii, Acinetobacter genospecies 3 and Acinetobacter genospecies 13TU in Taiwan - Corrected Proof

2010-01-27

Abstract: A total of 81 clinical isolates of the three clinically important Acinetobacter spp., namely Acinetobacter baumannii, Acinetobacter genospecies 3 and Acinetobacter genospecies 13TU, were analysed for differences in carbapenem resistance genes. Of the 81 isolates, 40 (49%) were resistant to carbapenems. Most A. baumannii isolates (47/53, 88.7%) contained the ISAba1–blaOXA-51-like gene and exhibited a higher minimum inhibitory concentration to imipenem than A. baumannii without the ISAba1 element. All four carbapenem-resistant A. genospecies 3 isolates contained blaIMP-1 and an ISAba3–blaOXA-58-like gene. Three A. genospecies 13TU isolates contained an ISAba3–blaOXA-58-like and either a blaIMP-1 or a blaVIM-11 gene. The five blaIMP-1-containing strains were resistant to imipenem and were positive for metallo-β-lactamase (MBL) activity by the Etest, and the two blaVIM-11-containing strains were susceptible to imipenem and were MBL-negative by Etest. Imipenem hydrolysis tests showed that the blaIMP-1-containing strains exhibited much higher imipenem-hydrolysing activity than the two blaVIM-11-containing strains. No transcripts of blaVIM-11 or blaOXA-58-like genes were detected. Analysis of outer membrane proteins showed that OprD was absent in the only blaIMP-1-containing A. genospecies 13TU strain owing to the presence of a premature stop codon in the oprD gene. In summary, several differences were detected between the carbapenem resistance genes of clinical Acinetobacter spp. in Taiwan, and loss of OprD may be associated with imipenem resistance in A. genospecies 13TU.

Predictors of acute kidney injury associated with intravenous colistin treatment - Corrected Proof

2010-01-20

Abstract: Colistimethate sodium (CMS) was recently re-introduced into clinical practice as a last resort for the treatment of nosocomial infections caused by multiresistant bacteria. This retrospective cohort study was designed to identify predictors of acute kidney injury (AKI) associated with intravenous (i.v.) CMS treatment. From March 2007 to July 2008, 71 adult patients receiving CMS for ≥72h were enrolled. AKI was defined using Risk, Injury, Failure, Loss and End-stage kidney disease (RIFLE) criteria according to serum creatinine. The median total dose of CMS was 54.3mg/kg (range 27.5–94.5mg/kg). AKI developed in 38 patients (53.5%). Cox regression analysis based of cumulative CMS dose (mg/kg) identified four independent predictors of AKI: male sex [hazard ratio (HR)=3.55, 95% confidence interval (CI), 1.47–8.55]; concomitant use of a calcineurin inhibitor (HR=6.74, 95% CI 2.49–18.24); hypoalbuminaemia (serum albumin level <2.0g/dL) (HR=6.29, 95% CI 2.04–19.39); and hyperbilirubinaemia (total bilirubin level >5mg/dL) (HR=3.53, 95% CI 1.17–10.71). In conclusion, AKI was a common complication of i.v. CMS treatment. Male sex, concomitant use of calcineurin inhibitors, hypoalbuminaemia and hyperbilirubinaemia were independent predictors of AKI. The effect of AKI on patient outcomes was not determined.

Evaluation of azithromycin, trovafloxacin and grepafloxacin as prophylaxis against experimental murine Brucella melitensis infection - Corrected Proof

2009-12-21

Abstract: The prophylactic potential of the azalide azithromycin as well as the fluoroquinolones trovafloxacin and grepafloxacin was assessed for the control of infection with Brucella melitensis in an experimental mouse model, determined by reduction in splenic bacterial burden. Trovafloxacin showed limited protective efficacy when administered 2h following a low-dose B. melitensis challenge, whereas grepafloxacin was ineffective. In comparison, azithromycin provided significant control of infection both following low- and high-dose challenges. Overall, the data confirm the potential utility of azithromycin in the prophylaxis of brucellosis and suggest that neither trovafloxacin nor grepafloxacin would likely be valuable for post-exposure prophylaxis of Brucella infection.

WITHDRAWN: Synergistic interaction of aciclovir and a helicase-primase inhibitor, BAY 57-1293, against herpes simplex virus type 1 - Corrected Proof

Manish Kumar, Hilary W. Thompson, Emily D. Varnell, Herbert E. Kaufman — 2009-01-27

This article has been withdrawn at the request of the author(s). The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

WITHDRAWN: High frequency of mutations in the rpoB gene in rifampicin-resistant clinical isolates of Mycobacterium tuberculosis from Iran - Corrected Proof

Farahnoosh Doustdar, Azar Dokht Khosravi, Parissa Farnia, Ahmad Reza Bahremand — 2007-10-16

This article has been withdrawn consistent with Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). The Publisher apologizes for any inconvenience this may cause.