Distribution of insertion sequences associated with Tn1546 and clonal diversity of vancomycin-resistant enterococci isolated from patients in Tehran, Iran

Department of Bacteriology, Pasteur Institute of Iran, Tehran, Iran.
Iranian Journal of Microbiology 03/2010; 2(1):14-21.
Source: PubMed


Infection with vancomycin-resistant enterococci (VRE) has caused a therapeutic problem. VanA and VanB resistant types are the predominant phenotypes among vancomycin resistant enetrococci. Transposon 1546 (Tn1546) harboring the vanA gene cluster, plays an important role in the horizontal transfer of vanA gene. In this study, we examined the phenotypic and genotypic diversity of a number of clinical VRE.
Twenty-four clinical VRE isolated from two university hospitals in Tehran were examined based on their antimicrobial susceptibility, Tn1546 related element organization and pulsed-field gel electrophoresis (PFGE) patterns. Integration of well-studied insertion sequence elements IS1216V, IS1542 and IS1251 was examined by PCR mapping and sequencing.
From 24 isolates, 15 isolates with VanA phenotype and 9 isolates with VanB phenotype were identified which both groups interestingly possessed the vanA gene. According to PCR mapping, our isolates were assigned to 6 main groups. In 14 (58.3%) isolates, IS1216V was inserted in vanX-vanY region and/or in truncated left-hand of Tn1546-like elements. In 11 (45.8%) isolates, both IS1216V and IS1542 were inserted in vanX-vanY and orf2-vanR regions, respectively and none of them harbored IS1251. Interestingly, PFGE of the isolates showed a high degree of diversity.
PCR mapping revealed that VanA elements in our isolates were highly heterogeneous. Overall, we found no correlation between transposon type and PFGE pattern. Genetic diversity of VRE provides practical information for epidemiological studies and our data showed horizontal transfer of VRE in this region.

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Available from: Parisa Farrokh, Oct 01, 2015
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    • "Enterococci have emerged as very important nosocomial pathogens, and this is attributed, among other factors, to their broad natural and acquired resistance to antimicrobial agents, including glycopeptides, vancomycin and teicoplanin (Cetinkaya et al., 2000; Gold, 2001;Oskoui and Farrokh, 2010). Although a lot of Enterococcus species have been identified, only two are responsible for the majority of human infections, that is, Enterococcus faecalis and Enterococcus faecium. "
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    ABSTRACT: Published data concerning correlation between virulence factors and resistance markers is relatively scarce. The aim of this study was to determine the relationship between antibiotic resistance, gelatinase production and pheromone response in the Enterococcus faecalis pathogens isolated from Egypt. Out of the 19 E. faecalis clinical isolates, 5 were able to produce gelatinase enzyme. These virulent isolates were multidrug resistant and showed high level vancomycin resistance. They were tested for mating ability. They cotransfered pheromone response genes together with vancomycin resistance determinants and gelatinase production to sensitive recipient strains. The gel E gene was detected in all donor isolates and their corresponding transconjugants phenotypically and genotypically. The PCR amplicons of a heavy gelatinase producing isolate and its transconjugants were subjected to sequencing. Significant homology was detected with OG1RF strain following sequence search with a GenBank database. Statistical analysis revealed significant positive direct correlation between vancomycin-and chloramphenicol-resistance, and gelatinase production in E. faecalis isolates.
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