A streamlined method for the fast and cost-effective detection of bacterial pathogens from positive blood cultures for the BacT/ALERT blood culture system using the Vitek MS mass spectrometer.

BACKGROUND AND OBJECTIVE: Prompt pathogen identification of blood stream infections is essential to provide appropriate antibiotic treatment. Therefore, the objective of this prospective single centre study was to establish an inexpensive, fast and accurate protocol for bacterial species identification with SDS protein-extraction directly from BacT/Alert® blood culture (BC) bottles by VitekMS®. RESULTS: Correct species identification was obtained for 198/266 (74.4%, 95%-CI = [68.8%, 79.6%]) of pathogens. The protocol was more successful in identifying 87/96 (91.4%, 95%-CI = [83.8%, 93.2%]) gram-negative bacteria than 110/167 (65.9%, 95%-CI = [58.1%, 73.0%]) gram-positive bacteria. The hands-on time for sample preparation and measurement was about 15 min for up to five samples. This is shorter than for most other protocols using a similar lysis-centrifugation approach for the combination of BacT/Alert® BC bottles and the Vitek® MS mass spectrometer. The estimated costs per sample were approx. 1.80€ which is much cheaper than for commercial kits. CONCLUSION: This optimized protocol allows for accurate identification of bacteria directly from blood culture bottles for laboratories equipped with BacT/Alert® blood culture bottles and VitekMS® mass spectrometer.

Epidemiology of Candida blood stream infections in patients with hematological malignancies or solid tumors.

Invasive Candida infections are associated with high morbidity and mortality. Due to an increased incidence in patients with hematological or oncological malignancies, fluconazole prophylaxis became a common practice in many centers in the late 1990s. Until recently, there was insufficient data on the effect of the use of azoles on the incidence of Candida blood stream infections and species distribution. Here we present a single center retrospective study of the epidemiology of Candida blood stream infections in hospitalized patients at a German university medical center from 2003-2009. Twenty-one Candida species were isolated in culture from blood specimens of 20 patients. The annual rate of candidemia approached 1.1 per thousand hospitalizations, during the first 5 years of the survey, but showed a significant increase after 2007. Candida albicans, although still the dominant species, was recovered as the responsible pathogen from only 28.6% of the cases. A high rate of fatal outcomes was noted at 30 days (56%) and 100 days (67%) after the first positive finding of Candida in blood culture. These results underline the clinical significance of this infectious complication, and the need for continuous monitoring for Candida blood stream infections in order to improve the clinical and therapeutic management of this specific patient population.

Panton-Valentine leukocidin-positive Staphylococcus aureus infections in returning travelers.

Skin and soft tissue infections caused by Panton-Valentine leukocidin-producing strains of Staphylococcus aureus are emerging among travelers returning from the tropics. Here, we here present data on 15 affected individuals. Intrafamiliar spread was documented in one case, and occupational transmission was assumed in another. Spa typing of the strains revealed a broad spectrum of variants, but some were clonally related. Methicillin-resistant Staphylococcus aureus (MRSA) was found in three cases.

First survey of metallo-beta-lactamases in clinical isolates of Pseudomonas aeruginosa in a German university hospital.

A total of 489 clinical isolates of Pseudomonas aeruginosa was investigated for metallo-beta-lactamase (MBL) production. Molecular analysis detected a blaVIM-1 gene in the chromosome of one isolate and a blaVIM-2 gene carried on the plasmid in seven isolates. Moreover, we showed that an initial screening by combined susceptibility testing of imipenem and ceftazidime followed by a confirmatory EDTA combination disk test represents a valid alternative to the molecular investigation of MBL genes, making MBL detection possible in routine diagnostic laboratories.

Prevalence and antimicrobial susceptibility of microorganisms isolated from sputa of patients with cystic fibrosis.

BACKGROUND: New emerging pathogens and associated antimicrobial resistance mechanisms have been observed in the respiratory tract of patients suffering from cystic fibrosis (CF) in the last years. Amongst others, the rate of metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa strains is growing. However, there are no published data on the prevalence of MBL-producing P. aeruginosa in CF patients to our knowledge. METHODS: In this study, 271 sputum samples of 60 CF patients were collected during a 12-months period. Microbiological cultures and antimicrobial susceptibility tests of the most frequently isolated bacteria were performed. RESULTS: 464 bacterial and 414 fungal strains were isolated and characterized. 63.3% of the patients harbored Staphylococcus aureus, 50% P. aeruginosa, 16.6% Haemophilus influenzae, 15% Stenotrophomonas maltophilia and 13.3% non tuberculous Mycobacteria (NTM). Methicillin resistant S. aureus (MRSA) and MBL-producing P. aeruginosa were detected in 3 (5%) and 5 (8.3%) patients respectively. Among the fungi, Aspergillus fumigatus and Candida albicans showed the highest prevalence. CONCLUSIONS: The detection of MBL-producing P. aeruginosa and MRSA in CF patients confirms that antimicrobial resistance patterns should be always kept under surveillance. Moreover hygiene regulations in CF clinics should prevent a further spread of resistant bacterial strains.

Typing of methicillin-resistant Staphylococcus aureus in a university hospital setting by using novel software for spa repeat determination and database management.

The spa gene of Staphylococcus aureus encodes protein A and is used for typing of methicillin-resistant Staphylococcus aureus (MRSA). We used sequence typing of the spa gene repeat region to study the epidemiology of MRSA at a German university hospital. One hundred seven and 84 strains were studied during two periods of 10 and 4 months, respectively. Repeats and spa types were determined by Ridom StaphType, a novel software tool allowing rapid repeat determination, data management and retrieval, and Internet-based assignment of new spa types following automatic quality control of DNA sequence chromatograms. Isolates representative of the most abundant spa types were subjected to multilocus sequence typing and pulsed-field gel electrophoresis. One of two predominant spa types was replaced by a clonally related variant in the second study period. Ten unique spa types, which were equally distributed in both study periods, were recovered. The data show a rapid dynamics of clone circulation in a university hospital setting. spa typing was valuable for tracking of epidemic isolates. The data show that disproval of epidemiologically suggested transmissions of MRSA is one of the main objectives of spa typing in departments with a high incidence of MRSA.