Characterization of coagulase-negative staphylococcal isolates from blood with reduced susceptibility to glycopeptides and therapeutic options.

BACKGROUND: Coagulase-negative staphylococci (CoNS) are a major cause of nosocomial blood stream infection, especially in critically ill and haematology patients. CoNS are usually multidrug-resistant and glycopeptide antibiotics have been to date considered the drugs of choice for treatment. The aim of this study was to characterize CoNS with reduced susceptibility to glycopeptides causing blood stream infection (BSI) in critically ill and haematology patients at the University Hospital Tor Vergata, Rome, Italy, in 2007. METHODS: Hospital microbiology records for transplant haematology and ICU were reviewed to identify CoNS with elevated MICs for glycopeptides, and isolates were matched to clinical records to determine whether the isolates caused a BSI. The isolates were tested for susceptibility to new drugs daptomicin and tigecycline and the genetic relationship was assessed using f-AFLP. RESULTS: Of a total of 17,418 blood cultures, 1,609 were positive for CoNS and of these, 87 (5.4%) displayed reduced susceptibility to glycopeptides. Clinical review revealed that in 13 cases (7 in haematology and 6 in ICU), CoNS with reduced susceptibility to glycopeptides were responsible for a BSI. Staphylococcus epidermidis was the causative organism in 11 instances and Staphylococcus haemolyticus in 2. The incidence of oxacillin resistance was high (77%), although all isolates remained susceptible to linezolid, daptomycin and tigecycline. Fingerprinting of CoNS identified one clonal relationship between two isolates. CONCLUSION: Multi-resistant CoNS with reduced susceptibility to glycopeptides, although still relatively infrequent in our hospital, are emerging pathogens of clinical concern. Surveillance by antibiotyping with attention to multi-resistant profile, and warning to clinicians, is necessary.

High performance liquid chromatographic determination of plasma free and total tazobactam and piperacillin.

A high-pressure liquid chromatography (HPLC) method with ultraviolet detection was developed for the measurement of plasma free and total tazobactam and piperacillin. This method is simple and fast, requiring only 11 min for the HPLC run and a sample preparation of about 11 min for total drugs and 10 min for free drugs. The procedure for the assay involves the treatment of plasma with acetonitrile for total drugs determination, and the use of a centrifugal filter device to deproteinize plasma for free drugs determination. The HPLC column, a Hypersil-ODS, was equilibrated with an eluent mixture composed of acetonitrile-potassium phosphate (pH 2.6). CVs for repeatability of tazobactam and piperacillin measurements ranged from 4.30 to 6.60; CVs for reproducibility ranged from 5.60 to 9.40. Mean analytical recoveries ranged from 100.4 to 103%. A linear relationship was obtained between peak area and drugs concentration in the range studied (0-62.5mg/L for tazobactam and 0-500mg/L for piperacillin). The equation for regression line were y=19x-1.4 for tazobactam and y=1.7x-0.9 for piperacillin; correlation coefficients were >0.999. The lower limit of quantitation (LLQ) for standard samples was about 0.12 mg/L for tazobactam and 0.49 mg/L for piperacillin, respectively. The lower limit of detection (LLD) was 0.06 mg/L for tazobactam and 0.24 mg/L for piperacillin. This HPLC assay for tazobactam and piperacillin is sensitive and accurate, and provides a reliable determination of both free and total tazobactam and piperacillin in human plasma, thus allowing the determination of these analytes in patients receiving tazocillin therapy.

Acinetobacter baumannii in intensive care unit: a novel system to study clonal relationship among the isolates.

BACKGROUND: The nosocomial infections surveillance system must be strongly effective especially in highly critic areas, such as Intensive Care Units (ICU). These areas are frequently an epidemiological epicentre for transmission of multi-resistant pathogens, like Acinetobacter baumannii. As an epidemic outbreak occurs it is very important to confirm or exclude the genetic relationship among the isolates in a short time. There are several molecular typing systems used with this aim. The Repetitive sequence-based PCR (REP-PCR) has been recognized as an effective method and it was recently adapted to an automated format known as the DiversiLab system. METHODS: In the present study we have evaluated the combination of a newly introduced software package for the control of hospital infection (VIGI@ct) with the DiversiLab system. In order to evaluate the reliability of the DiversiLab its results were also compared with those obtained using f-AFLP. RESULTS: The combination of VIGI@ct and DiversiLab enabled an earlier identification of an A. baumannii epidemic cluster, through the confirmation of the genetic relationship among the isolates. This cluster regards 56 multi-drug-resistant A. baumannii isolates from several specimens collected from 13 different patients admitted to the ICU in a ten month period. The A. baumannii isolates were clonally related being their similarity included between 97 and 100%. The results of the DiversiLab were confirmed by f-AFLP analysis. CONCLUSION: The early identification of the outbreak has led to the prompt application of operative procedures and precautions to avoid the spread of pathogen. To date, 6 months after the last A. baumannii isolate, no other related case has been identified.

A novel mutation of varicella-zoster virus associated to fatal hepatitis.

BACKGROUND: Lethal varicella in immunocompetent hosts is rare and its pathogenesis is largely unknown. The discovery of glycoprotein E (gE) mutants showing attributes consistent with increased virulence in vitro and in animal models, provided a possible molecular mechanism underlying a more aggressive virus infection. However, these mutants have never been associated with unusually severe clinical cases. OBJECTIVES: To varicella-zoster virus (VZV) mutations that correlate with increased virulence. RESULTS: We report a case of fatal hepatitis caused by a VZV bearing a novel mutation on the 3B3 monoclonal antibody epitope of gE in an immunocompetent host. CONCLUSIONS: This report describes a mutant VZV responsible for an aggressive clinical course in an immunocompetent host. Linking these severe clinical presentations of VZV infection to virus mutations might provide insights into the underlying pathogenic mechanisms.

Microbiologic characteristics and predictors of mortality in bloodstream infections in intensive care unit patients: A 1-year, large, prospective surveillance study in 5 Italian hospitals.

BACKGROUND: Bloodstream infections (BSIs) from multidrug-resistant (MDR) bacteria cause morbidity and mortality in intensive care unit (ICU) patients worldwide. This study investigated the incidence of BSIs in 5 adult general ICUs in Rome, Italy, and evaluated the mortality rate and risk factors associated with these infections. METHODS: Over a 12-month period, 1,318 patients were enrolled. Demographic characteristics, Simplified Acute Physiology Score II (SAPS II), comorbidities, and BSI isolate data were collected. After stratification for the outcome, statistical analysis was performed to assess the impact of patient risk factors on in-hospital mortality. RESULTS: There were 324 BSIs in 175 patients recorded, with an in-hospital mortality rate of 46%. Univariate analysis revealed that SAPS II, cardiac comorbidity, and Klebsiella pneumoniae BSI were significantly associated with a higher risk of death. Having a K pneumoniae BSI and cardiac illness at admission were both confirmed to be associated with death by multivariate analysis (P = .0162 and P = .0158, respectively). Most of the K pneumoniae isolates showed high resistance rates to carbapenems. CONCLUSION: BSIs caused by K pneumoniae and cardiovascular comorbidity in ICU patients are associated with a higher risk of death. Thorough surveillance for MDR pathogens and stratification of the patients' risk on admission into the ICU are key to improving the outcomes of these infections.

In vitro fluconazole susceptibility of 1565 clinical isolates of Candida species evaluated by the disk diffusion method performed using NCCLS M44-A guidelines.

We determined the in vitro activity of fluconazole against 1565 clinical Candida spp. isolates collected from different specimens of non-AIDS outpatients and inpatients in 3 different regions of Italy. Susceptibility testing was performed by agar disk diffusion using the NCCLS document M44-A guidelines. Candida albicans was the most frequently isolated yeast (68%) followed by C. glabrata (15%), C. tropicalis (5%), C. parapsilosis (5%), and C. krusei (5%). Other yeasts represented 4% of all isolates. Of the 1565 isolates tested, 1449 (92.6%) were susceptible (S) to fluconazole, 43 (2.7%) were susceptible dose-dependent (S-DD) and 73 (4.7%) were resistant (R). Almost all (98.2%) of the C. albicans isolates were classified as S or S-DD. Despite its widespread use, fluconazole displayed good activity against the isolates we tested, and the disk diffusion method was confirmed as a reliable approach to the evaluation of in vitro susceptibility of yeasts to this antimycotic agent.