Detection of Vancomycin resistant Enterococci from clinical specimens at University Teaching Hospitals

Abstract

Enterococci are commensal gram-positive bacteria in the gastrointestinal tract of humans. They have emerged as important nosocomial pathogens due to their ability to acquire and confer antimicrobial resistance genes, hence making management of infections due to Enterococcus species difficult. Resistance to glycopeptide antibiotics, especially Vancomycin is of special concern as Vancomycin resistant genes are encoded on plasmids which can be transferred to other organisms. Currently, there is no documented information relating to the occurrence and resistance genes of VRE at the University Teaching Hospitals (UTH’s) in Lusaka Zambia. To isolate and determine the occurrence of Vancomycin resistant Enterococcus (VRE), and the genes responsible for VRE resistance from blood, urine and pus specimens received in the Microbiology Laboratory at the UTH’s, Lusaka. This was a cross-sectional study. Enterococci were isolated from urine, pus and blood specimens submitted to UTH’s Microbiology Laboratory from July to August 2017. Enterococci isolation was done by culture of specimens on blood agar, cystine lactose electrolyte deficient medium (CLED), and Bile Esculin Azide (BEA) agar. Presumptive identification of VRE isolates was carried out using Brilliance VRE chromogenic media. Identification to species level, antibiotic susceptibility testing and minimum inhibitory concentrations (MIC) was determined with the Vitek 2 compact. Polymerase chain reaction (PCR) was used to confirm presence of resistance genes. Out of 817 specimens, 25 (3%) Enterococcus isolates, comprising 22 Enterococcus faecalis and 3 Enterococcus faecium, were Vancomycin resistant as shown by chromogenic media and Vitek 2 compact. VanB genes were confirmed by PCR with most isolates coming from urine, followed by pus then blood. Some isolates were resistant to Penicillin, Ampicillin and Clindamycin, with none being resistant to nitrofurantoin. More enterococci were isolated from urine compared to pus and blood, with most patients affected being aged between 28 and 46. More women were affected as compared to men. Brilliance chromogenic media was accurate in detection of VRE, as was PCR in confirming presence of resistance genes from the isolates. Vancomycin resistant Enterococci were isolated, with the main isolate being E. faecalis as compared to E. faecium. VanB genes were detected by PCR. The study showed presence of multidrug resistant VRE. There is need for determination of risk factors and regular surveillance of antimicrobial susceptibilities for VRE. Keywords: Vancomycin resistant enterococci, Chromogenic media, Glycopeptide antibiotics, Polymerase chain reaction