The presence and restriction fragment length polymorphism (RFLP) of DNA fragments hybridizing with virulence and "house keeping" gene probes were analyzed for 87 group B streptococcal (GBS) strains of human and bovine origin. Most characteristics obtained for bovine strains were similar when compared with those for human strains. The most significant degree of RFLP was discovered for the sizes of HindIII fragments containing bca gene. Human GBS strains with bac gene, encoding beta antigen with IgA binding capacity, were characterized by almost identical complex hybridization patterns with multiple gene probes. At the same time bac gene was not found among bovine GBS strains. Gene scpB that encodes C5a peptidase in all human GBS strains was detected only in 9 of 39 strains of bovine origin. These two characteristics effectively distinguished bovine GBS strains from GBS strains of human origin.

Little has been published about the occurrence, speciesidentification, andpathogenicpotentialofcoagulasenegative staphylococci (CoNS) present in drinking water. In this study, ten species were identified among 57 isolates of staphylococci from 756 samples of chlorinated drinking water taken from public distribution networks in the Slovak Republic. S. warneri (37%), S. haemolyticus (23%), and S. saprophyticus ssp. saprophyticus (14%) were identified most frequently. Isolates did not produce coagulase, DNase, or hyaluronidase; production of gelatinase and lecithinase was observed in 28 and 22 isolates, respectively. Genetically encoded ability for production of enterotoxin SED was revealed in two isolates. Among ten antibiotics tested, resistance to ampicillin (66.7%), penicillin (64.9%), and erythromycin (57.9%) were observed most frequently. Resistance to gentamicin, vancomycin, or clindamycin was not confirmed. Production of β-lactamase was observed in 64.9% of isolates. Fourty-two isolates were resistant to two or more antibiotics tested, and eight isolates showed multiresistance. The presence of mecA gene was confirmed in 8 isolates, while PBP2a was revealed in 7. Two isolates of S. epidermidis were identified as methicillin-resistant (MRSE). The results demonstrate that CoNS in chlorinated drinking water may possess virulence factors and show resistance to various antibiotics. Therefore, their pathogenic potential should not be ignored.

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Nineteen serogroup 1/2a Listeria monocytogenes strains isolated from raw milk, dairy products and salt water in one dairy were analyzed. Pulsed field gel electrophoresis (PFGE) and ribotyping were used to determine whether these strains isolated over a 8-month period are epidemiologically related. The samples of raw milk were contaminated by different L. monocytogenes clones. The clones isolated from dairy products (with the exception of one sample) and salt water were identical. Comparative genetic analysis of the clones isolated from raw milk, salt water and dairy products revealed the source of contamination and identified the L. monocytogenes strain involved in this process.