Phenotypic Detection and Antibiogram of β-lactamase-producing Proteus Species in a Tertiary Care Hospital, India.

Abstract

Background: Proteus species cause a variety of community- and hospital-acquired illnesses. Synthesis of β-lactamases is the predominant mechanism for resistance to β-lactam antibiotics. Among the β-lactamases, extended spectrum β-lactamases (ESBLs) and AmpC β-lactamases are the most common.

Aim: The objective of this study was to determine the occurrence of ESBL and AmpC β-lactamases in Proteus species among various clinical isolates at a tertiary care hospital, India.

Materials and methods: This study was done to identify various species of Proteus from clinical samples (n = 3922). Antimicrobial susceptibility was performed by Kirby-Bauer disc diffusion method. ESBL production was detected by modified double-disc synergy test and indirect modified three-dimensional tests and AmpC β-lactamase production by AmpC disc test and modified Hodge test.

Results: Proteus species were isolated in 5.4% (101/1876) specimens. Three Proteus species isolated were Proteus mirabilis 62.4% (63/101), Proteus vulgaris 29.7% (30/101), and Proteus penneri 7.9% (8/101). ESBL producers confirmed by both tests were of 88.1% (89/101). Only AmpC β-lactamase was produced by four isolates. Coproduction of ESBL and AmpC β-lactamase was observed in 58.4% (52/89) of isolates. Twelve isolates were non-β-lactamase producers. Multidrug resistance (MDR) was found in 95.1% (96/101) of isolates, 50.5% (51/101) were possibly extensively drug resistant and none were pan drug resistant. None of the isolates were resistant to piperacillin-tazobactam. P. penneri isolates exhibited high resistance to most of the antibiotics.

Conclusions: A high prevalence of ESBL and AmpC β-lactamases was found that concurrently showed MDR. Phenotypic methods for the detection of β-lactamases are easy and simple and can be implemented in routine diagnostic laboratories along with susceptibility testing. These data will assist the clinicians in the management and control of infections.