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.

Keywords: AmpC β‑lactamase, Extended spectrum β‑lactamase, Extensively drug resistant, Multidrug resistant, Proteus species