The relationship between antibiotic resistance and virulence factors in urinary Enterococcus isolates

Increasing multidrug resistance in nosocomial Enterococcus strains from all over the world recently enhances the need for further investigation of enterococci, especially their virulence factors. There are still many lacking parts about virulence factors of clinical enterococcus isolates. In this study, it was aimed to investigate the antibiotic resistance and the presence of potential virulence factors of 91 Enterococcus strains (59 E.faecalis, 31 E.faecium and 1 E.gallinarum) isolated from urine cultures of inpatients between January 2008-June 2010 in our hospital and also to evaluate whether a correlation existed between antibiotic resistance and potential virulence factors. The genes which encoded virulence factors of enterococci; aggregation substance (AS), enterococcal surface protein (ESP) and hyaluronidase (HYL) (asa1, esp, hyl respectively) were studied by molecular methods and haemolysin production and gelatinase activity were studied by phenotypic methods. Vancomycin resistant strains were checked for the presence of vanA and vanB genes. Eight (25.8%) E.faecium isolates were found glycopeptide resistant. In seven of these isolates resistance type was vanA and in one it was neither vanA nor vanB. High-level gentamicin and high-level streptomycin resistance rates were 74.2% and 61.3% in E.faecium strains and were 22% ve 27.1% in E.faecalis strains, respectively. Beta-lactamase production and linezolid resistance were not detected in any of the strains. E.faecium isolates were more resistant (p< 0.001-0.013) than E.faecalis isolates to all tested antibiotics except tetracycline, minocycline, doxycycline and streptogramin (p< 0.001). hyl gene positivity (p< 0.001) was found higher in E.faecium isolates whereas esp (p= 0.003) and asa1 (p< 0.001) gene positivity, haemolysin production (p=0.014) and gelatinase activity (p= 0.029) were higher in E.faecalis isolates. AS and ESP were the most frequent virulence factors, with the rates of 26.7% and 25.6%, respectively. There were 32 (35.6%) strains without any of the investigated virulence factors. We have also detected that asa1 gene positive E.faecalis isolates were more resistant to ciprofloxacin (p= 0.001), norfloxacin (p= 0.006) and levofloxacin (p= 0.001) than asa1 gene negative isolates; esp gene positive E.faecalis isolates were more resistant to doxycycline (p= 0.043) than esp gene negative isolates and hyl gene positive E.faecium isolates were more resistant to nitrofurantoine (p= 0.011) than hyl