Plasmid-mediated (β-lactam resistance in pathogenic Gram-negative bacteria isolated in South India

Abstract

A field study was undertaken at the Christian Medical College Hospital in Vellore, South India in 1984. Two hundred and eighty-four clinical isolates of enterobacteria were collected from patients with significant bacteriuria and their sensitivities to a series of β-lactam antibiotics were determined. There was a very high incidence of β-lactam resistance (ampicillin resistance > 80% and cephaloridine resistance > 65%) amongst these isolates. There was significant resistance to the combination of ampicillin and clavulanic acid but few of the isolates were resistant to cefuroxime or ceftazidime. Seventy seven per cent of the Escherichia coli isolates were resistant to ampicillin and 57% were resistant to cephaloridine. Most of the resistant Esch. coli isolates carried resistance genes for both ampicillin and cephaloridine which were transferable, either by direct conjugation or by mobilization with the X⁺ plasmid. Characterization of the R-plasmids revealed considerable diversity. Although the distribution of plasmid-mediated β-lactamases was broadly similar to those found in other surveys, three new β-lactamases were identified and atypically some of the Esch. coli isolates produced PSE β-lactamases.