Reduced Susceptibility to Biocides among Enterococci from Clinical and Non-Clinical Sources / 감염과화학요법

Background@#Wide use of biocidal agents such as benzalkonium chloride (BCC) and chlorhexidine digluconate (CHX) in hospitals and non-hospital environments, has raised concerns over the emergence of non-susceptible strains. Efflux pumps are of known main mechanisms in biocide tolerance which have been rarely addressed in enterococci - members of gut microbiota which can cause serious problems particularly in hospitalized patients. The purpose of this study was to investigate the susceptibility of enterococci from different sources (clinical and fecal isolates) toward BCC and CHX, and its correlation with efflux associated genes. Also, possible link between biocide tolerance and antibiotic resistance was examined. @*Materials and Methods@#One hundred and four enterococcus isolates including clinical (n = 54) and fecal isolates (n = 50) were studied for susceptibility toward BCC, CHX, ciprofloxacin, gentamicin and vancomycin. Twelve efflux associated genes were investigated by polymerase chain reaction assay. @*Results@#In clinical isolates, reduced susceptibility to CHX and resistance to gentamicin and ciprofloxacin were significantly higher than fecal isolates. Vancomycin resistance was associated with increasing minimum inhibitory concentration of CHX. Among all investigated genes, only three ones, efrA, efrB and emeA were detected which were significantly associated with reduced susceptibility to CHX and were more frequent among clinical isolates. Also, high level resistance to gentamicin was significantly associated with the presence of efrA/B as well as with reduced susceptibility to CHX. @*Conclusion@#As expected, reduced susceptibility to CHX, was significantly higher in clinical isolates. However, the presence of a vancomycin-resistant enterococci among fecal isolates of healthy people which showed resistance/tolerance to studied antimicrobial agents, was unexpected and highlights the need to investigate other non-hospital environments to avoid dissemination of antimicrobial resistance. Correlation between reduced susceptibility to CHX and high level resistance to gentamicin, substantiates monitoring of biocide tolerance particularly in the healthcare settings to control the establishment of antimicrobial resistant strains.

Virulence Genes, Antibiotic Resistance and Capsule Locus Polymorphisms in Enterococcus faecalis isolated from Canals of Root-Filled Teeth with Periapical Lesions / 감염과화학요법

Frequent isolation of Enterococcus faecalis from root canal treated teeth with apical periodontitis, has proposed the role of this organism in endodontic treatment failures. Different factors have been suggested in the pathogenicity of this organism. In this study, 22 E. faecalis isolates from canals of root-filled teeth were identified, and phenotypic and genotypic characteristics were investigated. No resistance to vancomycin and gentamicin was noted, and most isolates (91%) were susceptible to ampicillin. Biofilm formation was detected in 73% of the isolates and may be considered as the most important virulence factor involved in the pathogenesis of these isolates.

Virulence Genes, Antibiotic Resistance and Capsule Locus Polymorphisms in Enterococcus faecalis isolated from Canals of Root-Filled Teeth with Periapical Lesions / 감염과화학요법

Frequent isolation of Enterococcus faecalis from root canal treated teeth with apical periodontitis, has proposed the role of this organism in endodontic treatment failures. Different factors have been suggested in the pathogenicity of this organism. In this study, 22 E. faecalis isolates from canals of root-filled teeth were identified, and phenotypic and genotypic characteristics were investigated. No resistance to vancomycin and gentamicin was noted, and most isolates (91%) were susceptible to ampicillin. Biofilm formation was detected in 73% of the isolates and may be considered as the most important virulence factor involved in the pathogenesis of these isolates.

Survey for Correlation between Biofilm Formation and Virulence Determinants in a Collection of Pathogenic and Fecal Enterococcus faecalis Isolates / 감염과화학요법

BACKGROUND: Enterococcus faecalis is an opportunistic pathogen that causes most of the enterococcal infections. Among the different factors implicated in the pathogenesis of these organisms, biofilm formation and antibiotic resistance are the most important. The ability for biofilm formation has been attributed to the presence of some virulence genes. However, no definite correlation has been found. This study aimed to detect biofilm formation and antibiotic resistance patterns in E. faecalis isolates collected from clinical and fecal samples, and to investigate possible correlation between some virulence genes (esp, cyl, gelE) and biofilm formation. MATERIALS AND METHODS: A collection of 123 E. faecalis isolates were investigated for antibiotic resistance and production of hemolysin, gelatinase, and biofilm using phenotypic methods. The esp, gelE and cyl genes were detected using polymerase chain reaction. RESULTS: Thirty-eight pathogenic isolates (37%) were positive for biofilm formation. Additionally, the gelE, esp, and cyl genes were detected in 74 (71.8%), 79 (76.7%) and 42 (40.8%) isolates, respectively. In the fecal samples, 18 (90%) isolates were biofilm producers and 11 (55%), 17 (85%) and 8 (40%) isolates were positive for gelE, esp, and cyl, respectively. There were significant differences in biofilm production between pathogenic and fecal isolates (P <0.001). Multidrug resistance (MDR) was found among 32% (n = 33) and 15% (n = 3) of the clinical and fecal isolates, respectively. However, no significant difference was seen between MDR and biofilm formation. Five pathogenic and two fecal isolates were negative for all investigated genes while they were they were biofilm producers. In contrast, 22 pathogenic isolates and 1 fecal isolate were positive for the tested genes, but did not form any biofilm. No significant differences were observed between biofilm formation and the presence of the esp, gelE and cyl genes in the pathogenic and fecal isolates (P ˃0.05). CONCLUSION: The presence of the esp, gelE and cyl genes might not be determining factors for biofilm formation in enterococci and other mechanisms might be involved in this process.