Retrospective study of incidence of metallo-β -lactamase-producing Non-fermenters in nosocomial infections of a tertiary care hospital, in Navi Mumbai

Abstract

Background: The growing increase in the rate of antibiotic resistance is a major cause for concern in both non-fermenting bacilli. β-lactams have been the mainstay of treatment for serious infections, and the most active of these are the carbapenems. Acquired metallo-β-lactamases (MBL) have recently emerged as one of the most worrisome resistance mechanisms owing to their capacity to hydrolyze all β-lactams, including carbapenems. We have undertaken this investigation to ascertain the incidence of MBL-producing non-fermenting bacilli, like Pseudomonas Spp. and Acinetobacter Spp. Aim: To determine the incidence of MBL in Nosocomial infections of non-fermenters and their clinical correlation. Objectives : Screening of nosocomial isolates for multidrug resistance by antibiotic sensitivity tests as per CLSI guidelines as a reference. To perform phenotypic confirmatory test of potential MBL isolates by double disc synergy test Clinical correlation with detection of these enzymes and the patients morbidity/mortality correlation with age, immunocompromised status and hospital stay. Materials and Methods : The study was conducted over a period of 12 months in a teaching hospital, in Navi Mumbai. Isolates included in the study were screened for imipenem resistance by conventional methods. The isolates that showed imipenem resistance were tested for MBL production by imipenem (IMP)-ethylene-diamine-tetra-acetic acid (EDTA) combined disc test. Imipenem-resistant non-MBL isolates also were tested for Modified Hodge test and AmpC β-lactamases production to detect other mechanisms of carbapenem resistance. Results: Total number of isolates tested were 107.Out of 107, 29 (27.1%) were MBL producers and 78(72.9%) were non-MBL producers. Among both types of non-fermenters , 66(61.68%) were Pseudomonas aeruginosa and 41(32.23%) were of Acinetobacters. In the sex distribution, 65.5%were males and 34.5% were females.18.18% were MBL positive Pseudomonas and among Acinetobacter species 41.46% were MBL positive. Mean age of MBL producers was 34 years. Mean hospital stay was 28 days. Mortality rate was 51.7% in MBL producers. Mortality was higher in Acinetobacter MBL producers.when compared to Pseudomonas MBL producers.