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Objectives: Since the 1980s members of lactococci, pediococci, leuconostocs and lactobacilli have rarely been indicated as opportunistic pathogens in humans. Generally, these taxa are part of the normal intestinal flora and occur in fermented foods and on plants. Due to their low virulence it is assumed that these bacteria are pathogenic only in immunocompromised hosts. Their sporadic occurrence in human clinical samples is often overlooked and/or they are misidentified. Methods: A total of 59 845 blood samples were isolated at the Department of Clinical Microbiology (Teaching Hospital, Brno, Czech Republic) during the 2000 – 2003. Biochemical identification was performed on selected LAB by API 50 CH kit and by conventional tests. (GTG)5- PCR fingerprinting and whole cell protein profile analysis by SDS-PAGE were performed to confirm the biochemical identification results. The MICs for antimicrobial agents (benzylpenicillin, ampicilin, cefotaxim, imipenem, erytromycin, clindamycin, gentamicin, ciprofloxacin, cotrimoxazol, metronidazol, vancomycin and teikoplanin) were determined by using the E-test MIC (Biodisk, Solna, Sweden). Results: A total of 59.845 investigated blood samples yielded 12.767 (21.3%) infected hemocultures of which 33 (0.25%) contained LAB. They were identified based on phenotypical testing as Lactobacillus plantarum (3 strains), Lactobacillus rhamnosus (7), Lactobacillus paracasei ssp. paracasei (2), Lactobacillus salivarius ssp. salivarius (1), Lactobacillus fermentum (1), Leuconostoc mesenteroides (9), Leuconostoc lactis (5) and Pediococcus pentosaceus (1). The (GTG)5- PCR fingerprinting and whole cell protein profile analysis confirmed above identifications and furthermore identified four strains which were biochemically classified at the genus level as Lactobacillus sakei ssp. carnosus, Lactobacillus curvatus, Leuconostoc pseudomesenteroides and Weissella confusa. All investigated strains (19) were resistant to vancomycin, teicoplanin and metronidazol and most of them to cotrimoxazol. Susceptibility to cefotaxim, imipenem, gentamicin and ciprofloxacin was variable. Conclusion: Lactobacillus rhamnosus and Leuconostoc mesenteroides were the most common LAB species isolated from blood samples. Although isolation of LAB from blood samples is rare, it is of clinical significance and it should be taken into account during treatment decision - especially when they are isolated in pure culture from sterile sites.
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