Evaluation of chromogenic VRE medium versus Conventional Vancomycin E test in Detection of Vancomycin Resistant Enterococci

Abstract

-Enterococci are a part of normal intestinal flora of both humans and animals, however they have also emerged as significant community acquired pathogens and a leading cause of nosocomial infections. - Enterococcus faecalis and Enterococcus faecium, are among the leading causes of several human infections, including bacteremia, septicemia, endocarditis, urinary tract infections, wound infections, neonatal sepsis and meningitis. -Enterococci have become resistant to a wide range of antibiotics which include Beta lactam antibiotics, aminoglycosides, and most importantly glycopeptides like vancomycin. -Transmission of VRE can occur through direct contact with colonized or infected patients or through indirect contact via the hands of health-care workers (HCWs), or via contaminated patient care equipments or environmental surfaces. -The control of VRE has become an increasing burden on health care resources since their discovery over 20 years ago. - Current techniques employed for their diagnosis include time consuming phenotypic methods or molecular methods requiring costly equipment and highly trained staff. An accurate, rapid diagnostic test has the ability to greatly reduce the spread of this organism which has the ability to colonize patients for long periods, potentially even lifelong. This study aimed to compare a new chromogenic media named HiChrome VRE agar in relation to convential vancomycin E.test in detection of vancomycin resistant enterococci. The present study was conducted in Al Abassia Fever hospital, El Sayed Galal Hospital, Tanta University Hospital and Kafr El Sheikh General Hospital during the period from February 2016 to November 2016. Sixty isolates were collected from (thirty eight males and twenty two females) from different surgical and medical departments and ICUs Their ages ranged from 15 years to 92 years. Twenty six isolates were obtained from urine samples while eighteen, eight, six, one and one isolates were obtained from wound, blood, endotracheal aspirate, ascetic fluid and cerebrospinal fluid respectively. These isolates were first identified to genus level then the sensitivity of these isolates to different antibiotics were tested by disc diffusion method. The results obtained regarding vancomycin susceptibility for VRE and VIE isolates by disc diffusion method were then checked by E-test. VRE and VIE isolates were identified by both HiStrep identification kit and vitek-2 to species level. All isolates were cultured on HiChrome VRE agar modified to test its sensitivity in comparision to E. test in detection of VRE and to test its sensitivity to identify VRE isolates to species level in comparison to both HiStrep identification kit and vitek-2 compact system. It was found that: • Antibiogram pattern of all enterococcal isolates (60 isolates) by disc diffusion method showed that the majority of collected isolates were resistant to ampicillin (91.7%), regarding chloramphenicol 31.7% resistant. 80% of isolates were resistant to ciprofloxacin. By disc diffusion 41.7% of isolates were resistant to vancomycin, 91.7% of isolates were resistant to erythromycin. 10% only were resistant to nitrofurantoin. 80% of isolates were resistant to levofloxacin, 76.7% were resistant to norfloxacin, 85% were resistant to rifampicin and 83.3% of them were resistant to penicillin G. • Out of 42 VRE isolates which were vancomycin resistant and intermediate resistant by disc diffusion method 12 (28.6%) were susceptible, 8 (19%) were intermediate resistant and 22 (52.4%) were resistant by E test. • Out of 60 isolates 28 isolates were inhibited when cultured on HiChrome VRE agar modified while the rest 32 (53.3%) isolates showed growth on it . • HiChrome VRE agar modified had 100% sensitivity, 83.3% specificity, 91.7% PPV, 100% NPV and 94.1% accuracy while disc diffusion had only 86.4% sensitivity and 66.7% specificity 82.6% PPV, 72.7% NPV and 79.4% accuracy in detection of vancomycin resistant enterococcal isolates. • Out of 22 VRE isolaes 19 were E.faecium (63.3%) and 3 were E.faecalis (5%) while out of 8 VIE isolates 3 were E.faecium (10%) and 5 were E.faecalis (16.7%). • Both HiChrome VRE agar modified and HiStrep-identification kit (plus added motility test and checking for pigment production) have the same specificity and sensitivity in relation to results obtained by vitek-2 compact system regarding species identification. • Antibiotic sensitivity pattern of VRE.faecium isolates, 100% were resistant to ampicillin, 15.8% were resistant to chloramphenicol, 84.2% were resistant to ciprofloxacin, 78.9% were resistant to erythromycin, 21.1were resistant to nitrofurantoin, 84.2% were resistant to levofloxacin, 57.9% were resistant to norfloxacin, 73.7% were resistant to rifampicin and 94.7% were resistant to penicillin G