Incidence of AmpC ß-lactamase producing bacteria isolated in Bamrasnaradura Infectiouse Disease Institute during July-September 2007

Abstract

          Like extended-spectrum ß-lactamases (ESBLs), AmpC ß-lactamase has a broad substrate profile that includes penicillins, cephalosporins, and monobactam. In contrast to ESBLs, they hydrolyze cephamycin and are not inhibited by commercial available ß-lactamase inhibitors. These enzymes are typically associated with multiple antibiotic resistances, leaving few therapeutic options. Bacteria, mostly Klebsiella pneumoniae and Escherichia coli, producing AmpC ß-lactamases have been responsible for nosocomial outbreaks of infection and colonization. Although AmpC ß-lactamases were first reported in the late 1980s, many infectious disease personnel remain unaware of their clinical importance. These enzymes are typically produced by isolates of E. coli, Klebsiella spp., Proteus mirabilis, and Salmonella spp.. AmpC ß-lactamases have been associated with false in vitro susceptibility to cephalosporins. Many laboratories do not test for this resistance mechanism because current tests are inconvenient, subjective, lack sensitivity and/ or specific, or require reagents that are not readily available. In this study the AmpC disk test was applied as a study tool for study the incidence of AmpC ß-lactamase producing bacteria isolated from July-September 2007 in Bamrasnaradura Infectious Diseases Institute. Among 117 strains of nonduplicated clinical isolates of gram negative bacteria, 18 isolates have been produced the AmpC ß-lactamase (15.8%). Beyond source of specimens, 7 strains of AmpC ß-lactamase producing bacteria has been isolated from 40 sputums (17.5 %), 4 strains have been isolated from 26 pus samples (15.4%), 6 strains have been isolated from 41 urine samples (14.6%), and 1 strain has been isolated from 7 hemoculture samples (4.3%), respectively.