AmpC beta lactamases among Gram negative clinical isolates from a tertiary hospital, South India

Abstract

AmpC β-lactamases are cephalosporinases that hydrolyze cephamycins as well as other extended-spectrum cephalosporins and are poorly inhibited by clavulanic acid. Although reported with increasing frequency, the true rate of occurrence of AmpC β-lactamases in different organisms, including members of Enterobacteriaceae, remains unknown. The present study was designed to determine the occurrence of AmpC enzyme-harbouring Gram-negative clinical isolates in a tertiary care hospital in Pondicherry state, South India. A total of 235 Gram negative clinical isolates were tested for resistance to cefoxitin, third generation cephalosporin (3GC) antibiotics, ampicillin, amikacin, co-trimoxazole, gentamicin, meropenem and tetracycline by disc diffusion method. Isolates found resistant to 3GC and cefoxitin were tested for the production of AmpC β -lactamases by three dimensional extraction method and AmpC disc method. Isolates found to sensitive to 3GC were subjected to disc antagonism test for inducible AmpC production. One hundred and thirty four (57%) strains were resistant to 3GC, among which 63(47%) were positive for plasmid-mediated AmpC beta lactamases production. Among the 101 strains sensitive to 3GC, 23 (22.7%) revealed the presence of inducible AmpC beta lactamases by disc approximation test. A total of 80.9% (51/63) of screen positive isolates were detected by Amp C disc test and 93.6% (59/63) by three dimensional extraction method. Out of the 86 AmpC producers, 67 (77.9%) were cefoxitin resistant .Inducible AmpC was not found in Esch.coli and Klebsiella spp. The AmpC producers also concurrently showed multidrug resistance pattern. AmpC producers were found to be prevalent in our hospital and though three dimensional extraction test detects AmpC better, the disk test is easier to perform routinely and is user- friendly.

Phenotypic methods for detection of various β-lactamases in Gram-negative clinical isolates: Need of the hour

“…[5] Mohamudha PR et al in 2010 evaluated a total of 235 strains from tertiary care hospital in south India with 134 strains resistant to third-generation cephalosporins, of which 63 (47%) were plasmid-mediated AmpC β-lactamase producers. [25] In our study, expressions of various β-lactamases either singly or in combination are in agreement with the other studies. The findings in the study are from tertiary hospital in the rural settings and high level of single or multiple ESBL mechanism in MDRO is definitely alarming necessitating an urgent need for evidence-based medicine particularly in rural settings where laboratory facilities are lacking and antibiotics are being rampantly used by the quacks.…”

Prevalence of ESBLs among Enterobacteriaceae and their Antibiotic Resistance Pattern from Various Clinical Samples

“…This is to exclude associated Amp-C type of β-lactamases. 19,20 In the study, K. pneumoniae ATCC 700603 and E. coli ATCC 25922 (HiMedia Laboratories, Mumbai) were used as positive and negative controls throughout, for ESBL production…”

Characterization of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae isolates from the community in Morocco

“…Third-generation cephalosporin resistance in non-ESBL producers (27 E. coli and 6 K. pneumoniae strains) could be due to some other resistance mechanism such as lack of permeation of porins and AmpC b-lactamase production (Mohamudha et al, 2010).…”