Phenotypic characteristics and population genetics of Enterococcus faecalis cultured from patients in Tehran during 2000-2001

Department of Microbiology, Alzahra University, Vanak, Tehran, Iran.
Canadian Journal of Microbiology (Impact Factor: 1.22). 11/2003; 49(10):645-9. DOI: 10.1139/w03-082
Source: PubMed


Conventional bacteriology techniques were used to identify enterococci isolates cultured from patients at different hospitals in Tehran during 2000-2001. The identification was confirmed using species-specific PCR targeting the D-alanyl-D-alanine ligase gene. A total of 59 isolates of Enterococcus faecalis were identified. The rates of resistance to different antibiotics were in the following order: penicillin 84%, ciprofloxacin 42%, high-level gentamicin 30%, nitrofurantoin 14%, imipenem 4%, and chloramphenicol 2%. Resistance to ampicillin was found to be rare among the Iranian isolates of E. faecalis. Multi-locus enzyme electrophoresis was then used to analyze the strains. Forty-five electrophoretic types were obtained when 10 enzyme loci were screened. Although the collection of bacterial isolates was limited in time and location, considerable heterogeneity was found. Analysis of strains for linkage disequilibrium demonstrated that the studied population is not clonal, since the index of association was not significantly different from zero (Ia = 0.0296). Enterococcus faecalis isolates recovered from patients in Tehran were genetically diverse and seemed to possess a high potential for genetic recombinations, though none were resistant to vancomycin.

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    ABSTRACT: Background: Enterococci faecalis are predominating species of Enterococci causing nosocomial infections. Acquisition of resistance to antibacterial agents, and ability to transfer the re- sistant genes made them clinically important. This study was performed to determine the frequency of isolation of different species of Enterococci, and the antibacterial resistance pattern of the isolated species. Methods: Enterococcal species were isolated from clinical samples. In vitro susceptibility of the isolates to 10 antibacterial agents was tested by standard methods and β-lactamase produc- tion was detected using starch-iodide method. Results: 100 Enterococci were isolated from 585 different clinical samples. 73% of the isolates were E. faecalis, 13% E. faecium and 14% which were not identified as either one, were regarded as other enterococcal species. Highest rate of resistance (98% or more) was found for oxacillin and penicil- lin while vancomycin and chloramphenicol were among the most active agents. Resistance to antibacterial agents was more common for E. faecium and β-lactamase production was found in 81% of the isolates. Conclusion: E. faecalis was the dominant species, with the higher rate of β-lactamase production. E. faecium was more resistant to antibacterial agents as compared to other isolates. 80% of the isolates had multiple drug resistance phenotypes (MDR). Low−level resistance to vancomycin (intermediate reaction in disk diffusion method, minimum inhibitory con- centrations range ≥4−16 µg/ml) and presence of MDR isolates is very important and should be considered as an danger alarm for serious enterococcal infections. Iran J Med Sci 2005; 30(2): 68-72.
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    ABSTRACT: The prevalence of resistance to high levels of gentamicin among 182 isolates of Enterococcus faecalis from 2 Iranian hospitals was 42%. Gentamicin resistance was associated with conjugative plasmids (>70 kb) in most strains. Fingerprinting using EcoRI and HindIII showed genetic variation among these plasmids and gave evidence of nosocomial outbreaks and persistence of infection in different wards of the study hospitals, as well as transfer of plasmids between genetically diverse isolates. Using EcoRI, hospital-based specific plasmid fingerprints were detected for the isolates that had previously proved to be unrelated by multilocus enzyme electrophoresis, suggesting the persistence of related plasmids at each hospital, though minor changes in these related plasmids could be detected with HindIII.
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