Abstract
Enterococcus spp. are remarkable multidrug resistant (MDR) bacteria that are causing serious healthcare-associated infections. The current study investigated the frequency of Enterococcus spp., antimicrobial susceptibility, biofilm formation and the presence of some plasmid-mediated virulence characters and antimicrobial resistance determinants in enterococcal isolates from Egyptian hospitals in Cairo. Enterococcus bacterial isolates were recovered from different clinical specimens and identified using biochemical testing and KB005A HiStrep™ identification kit. Kirby-Bauer disc diffusion method and/or broth microdilution method were used to determine the antimicrobial susceptibility patterns. Phenotypic assays were performed to study biofilm formation and cytolysin and gelatinase production. PCR assays targeting the plasmid-carried genes aac(6’)-aph(2’), aph(3)-IIIa, vanA, agg and cylA were performed. In this study, 50 isolates of diverse Enterococcus spp. were identified with E. faecium was the most frequently isolated one. High resistance profiles were determined against tested antimicrobials and all isolates were MDR. Moderate biofilm formation was detected in 20% of isolates, 18% showed complete blood hemolysis and 12% produced gelatinase. All isolates carried the tested aminoglycosides resistance genes, while vanA was found only in 4 isolates (8%). The virulence genes agg and cylA were detected in 4% and 32% of isolates, respectively. In conclusion, E. faecium was the most prevalent species. The entire isolates set were MDR and the plasmid-carried aminoglycoside resistance genes were extensively disseminated among MDR isolates. Thus, regular surveillance studies, from the area of study or other geographical regions in Egypt, and strict infection control measures are required to monitor the emerging MDR enterococci.
Highlights
Enterococci are ubiquitous Gram-positive bacteria that naturally reside in the mouth and the gastrointestinal tract of the human being[1]
Study of the antimicrobial resistance profiles of the tested isolates showed that all isolates showed resistance to ampicillin, ciprofloxacin, tetracycline, rifampicin and tobramycin, while 68%, 48%, 80%, 56% and 8% of the entire isolates collection were resistant to high-level streptomycin, high-level gentamicin, chloramphenicol, nitrofurantoin and linezolid, Fig. 1
Contrary to the disc diffusion method, which showed full vancomycin-resistant enterococci (VRE) profile; broth microdilution assay revealed only one E. faecium isolate had intermediate resistance pattern to vancomycin showing a VanB phenotype since susceptible to teicoplanin by Polymerase chain reactions (PCR) we detected a plasmidic vanA gene in this isolate, in other 3 strains still completely susceptible to vancomycin, these incongruent Enterococcus genotypes-phenotypes should be related to mutations or deletions in the VanA operons as previously described[41,42,43]. Results suggested that both minimal inhibitory concentration (MIC) and PCR should be taken into consideration in evaluating the susceptibility to vancomycin and identification of Vancomycin incongruence genotypes-phenotypes isolates, respectively and recommended the exclusion of vancomycin as therapy in patients were these isolates are detected
Summary
Enterococci are ubiquitous Gram-positive bacteria that naturally reside in the mouth and the gastrointestinal tract of the human being[1]. Virulence factors help in bacterial adhesion and attack of the host cells and modulating the host defences along with the production of extracellular enzymes and toxins[11]. Such virulence factors include capsule formation, the Enterococcus surface protein (Esp), aggregation substance and gelatinase enzyme which play important roles in establishing a biofilm on the abiotic surfaces in health care settings[5,11]. The plasmid-carried antimicrobial resistance determinants genes such as genes encoding aminoglycoside-modifying enzymes (aac(6’)aph(2’), aph(3)-IIIa) and vancomycin resistance gene vanA, in addition to the frequency of the genes encode the plasmid-mediated virulence factors including aggregation encoding gene agg and cytolysin biosynthesis encoding gene cylA were studied among Enterococcus spp. isolates collected in this study
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