Milan Seman

Antibiotic resistance and virulence factors among clinical and food enterococci isolated in Slovakia

The resistance to antibiotics and the distribution of virulence factors in enterococci isolated from traditional Slovak sheep cheese bryndza was compared with strains from human infections. The occurrence of 4 enterococcal species was observed in 117 bryndza-cheese isolates. The majority of strains were identified asE. faecium (76%) andE. faecalis (23%). Several strains ofE. durans and 1 strain ofE. hirae were also present. More than 90% of strains isolated from 109 clinical enterococci wereE. faecalis, the rest belonged toE. faecium. The resistance to 6 antimicrobial substances (ampicillin, ciprofloxacin, higher concentration of gentamicin, nitrofurantoin, tetracycline and vancomycin) was tested in clinical and food enterococci. A higher level of resistance was found in clinical than in food strains andE. faecium had a higher resistance thanE. faecalis; no resistance to vancomycin was detected. The occurrence of 3 virulence-associated genes,cylA (coding for hemolysin),gelE (coding for gelatinase) andesp (coding for surface protein) was monitored. Differences were found in the distribution ofcylA gene between clinical and bryndza-cheeseE. faecalis strains; in contrast to clinical strains (45%),cylA gene was detected in 22% of food isolates. The distribution of 2 other virulence factors,gelE andesp, was not significantly different in the two groups ofE. faecalis strains.cylA andgelE genes were not detected inE. faecium but more than 70% of clinicalE. faecium were positive foresp, even thought none of the 79E. faecium cheese isolates contained this gene.

PCR-based methods for identification of Enterococcus species.

Two DNA-based techniques were used for species identification of enterococci.PvuII digestion of the genus-specific PCR product yielded four different restriction profiles among 20 enterococcal species; one of them was species-specific forE. faecium. In the second case, 32 reference strains belonging to 20 enterococcal species were divided to 12 groups by amplification of internal transcribed spacer of rRNA operon. Interspecies and some intraspecies profile variability was determined. Both methods gave similar results.

Gould-Jacobs reaction of 6-amino-2,3-diphenylquinoxaline

SummaryCatalytic hydrogenation of 2,3-diphenyl-6-nitroquinoxaline led to the corresponding amine1 which in turn afforded products3a-i on reaction with alkoxymethylene derivatives2a-i. Thermal cyclization of3b and3f yielded substituted pyrazinoquinolones5b and5f, respectively. Optimal conditions for the successful hydrolysis of ester5b were found. The structures of all products were deduced from their IR, UV,1H, and13C NMR spectroscopic data.ZusammenfassungKatalytische Hydrierung von 2,3-Diphenyl-6-nitrochinoxalin ergibt das entsprechende Amin1, welches bei Reaktion mit den Alkoxymethylenderivaten2a-i zu den Produkten3a-i führt. Thermische Cyclisierung von3b und3f liefert die substituierten Pyrazinochinolone5b und5f. Für die Hydrolyse des Esters5b wurden optimale Bedingungen ermittelt. Die Strukturen aller Produkte wurden aus spektroskopischen Daten hergeleitet (IR, UV,1H- und13C-NMR).

Isolation, identification, and characterization of Vibrio cholerae from the Danube River in Slovakia

The occurrence of Vibrio cholerae, an important aquatic pathogen, was assessed in the surface water of the Danube River near Bratislava. The isolates were distinguished by biochemical tests and grouped by ARDRA to three clusters corresponding to three species (V. cholerae, Vibrio metschnikovii, and Aeromonas spp.). The identification of V. cholerae was confirmed by multiplex PCR using primer pairs targeted to ompW gene (membrane protein), ctxA gene (toxicity gene), and toxR gene (regulatory gene). None from the isolated V. cholerae from surface water contained ctxA gene; seven of them possessed toxR gene. Serotyping of V. cholerae isolates with polyvalent O antiserum and O/139 antiserum was negative. All isolates of V. cholerae were susceptible to chloramphenicol, rifampicin, tetracycline, variable to ampicillin, and resistant to kanamycin and streptomycin.

The Water quality of the Danube River and gravel pits in the Bratislava area (Slovakia)

The gravel pits are typical features of Bratislava. By their origin they are related to the river Danube. The water quality is determinated by various indicators, especially hydrochemical and microbiological ones. In the gravel pits water was determined for increase of chloride concentration and drop of sulphate concentration. Significant indicator of faecal contamination is the presence of enterococci. Faecal enterococci (E.faecalis, E.faecium, E.durans, E.hirae) dominates in the river Danube, and only two non-faecal enterococcal species, E.casseliflavus and E. seriolicida were found in the water of gravel pits with other enterococcal very related taxa: Lactococcus lactis and Aeromonas spp.

The occurrence of coliform bacteria in the cave waters of Slovak Karst, Slovakia

The diversity and abundance of coliform bacteria (taxonomically enterobacterias), an important quality water indicator, were determined for four representative caves in Slovak Karst: Domica Cave, Gombasecká Cave, Milada Cave and Krásnohorská Cave. Three hundred and fifty-two enterobacterial isolates were successfully identified by biochemical testing (commercial ENTEROtest 24) and selected isolates confirmed by molecular techniques (PCR, 16S rDNA sequence analysis). A total of 39 enterobacterial species were isolated from cave waters, with predominance of Escherichia coli, Serratia spp. and Enterobacter spp. PCR amplification of lacZ gene is not specific enough to provide a reliable detection of coliform bacteria isolated from the environment. Sequence analysis of 16S rDNA confirmed that all of the selected isolates belong to the family Enterobacteriaceae. In general, physical and chemical parameters of cave waters in Slovak Karst corresponded to national drinking water quality standards.