Epidemiology of invasive infections caused by vancomycin sensitive and resistant enterococcal strains among oncology patients at the National Cancer Institute of Sri Lanka from 1st of July 2012 to 31st of July 2013

Introduction and Objectives: Enterococci have traditionally been regarded as low grade pathogens but have emerged as an increasingly important cause of nosocomial infections in the last decade. While the Enterococcus faecalis remains the predominate species in clinical infection, Enterococcus faecium isolates are increasing in proportion. This study was carried out to describe the epidemiology of invasive enterococcal infections among oncology patients at the National Cancer Institute of Sri Lanka (NCISL).

Methods: 60 patients with invasive enterococcal infections, who were treated as inward patients at the National Cancer Institute of Sri Lanka from 1.7.2012 to 31.7 21013 whose samples were sent for microbiological investigation were included in this study. Speciation of the isolates was done by using a rapid manual analytic system (RapID STR panel-Oxoid). Vancomycin sensitivity was assessed in all enterococcal isolates by disc diffusion method, agar dilution screening method (CLSI guideline 2013)16 and detection of minimum inhibitory concentration (MIC) by using Vancomycin gradient strips. Teicoplanin MIC was assessed only in vancomycin resistant isolates using teicoplanin gradient strips. Associated factors for getting an infection with vancomycin resistant strains were assessed using a data extraction sheet.

Results: The incidence of invasive enterococcal infections among oncology patients was 1.1 per 1000 admissions. The incidence of invasive enterococcal infection caused by vancomycin resistant species was 0.16 per 1000 admissions. E. faecium was the dominant species causing invasive enterococcal infections (55%). Using the gradient strip method for determination of vancomycin MIC as the gold standard, the screening agar dilution method had 100% sensitivity and specificity and the disc diffusion test had a low specificity (77.8%). Almost all the participants (96.6%) had acquired the enterococcal infection from the hospital. Vancomycin resistant infections were more common in patients who had haematological malignancies, who were treated with 3rd generation cephalosporins and cytotoxic chemotherapy drugs.

Conclusions: E. faecium is the dominant species causing invasive enterococcal infections in oncology patients (55%) and phenotypically compatible with the VanA phenotype of glycopeptide resistant enterococci.