Prevalence of AmpC beta-lactamase and extended spectrum beta-lactamase co-producer in Escherichia coli and Klebsiella species in a teaching hospital.

INTRODUCTION: Beta-lactamase producing bacterial infection has been on surge due to selection pressure and injudicious antibiotics usage. Organisms that co-produced more than one beta lactamase enzyme posed diagnostic challenges which may result in inadequate treatment. To date, there is no standardised guideline offering phenotypic detection of AmpC β-lactamase. The purpose of this study was to determine the prevalence of ESBLs, AmpC β-lactamase and co-producer organisms in a teaching hospital.

MATERIALS AND METHODS: Three hundred and four isolates of E. coli and Klebsiella sp. had been selected via convenient sampling. These isolates were identified using conventional laboratory methods and their antimicrobial susceptibilities were determined using disc diffusion method. Those isolates were then proceeded with ESBL confirmatory test, cloxacillin-containing Muller Hinton confirmatory test, modified double disk synergy test and AmpC disk test.

RESULTS: Out of 304 isolates, 159 isolates were E. coli and 145 were Klebsiella sp. The prevalence of organisms which co-produced AmpC β-lactamase and ESBL enzymes were 3.0%. Besides that, 39 cefoxitin resistant and three cefoxitin susceptible isolates (13.8%) were proven to produce AmpC β-lactamase through AmpC disk test. Through the CLSI confirmatory test, 252 (82.9%) isolates were identified as ESBLs producers and the prevalence increased slightly when cloxacillin-containing Muller Hinton were used. Only three ESBLs positive organisms were positive for modified double disk synergy test.

CONCLUSION: Distinguishing between AmpC β-lactamase and ESBL-producing organisms has epidemiological significance as well as therapeutic importance. Moreover, AmpC β-lactamase and ESBLs co-producing organisms can lead to false negative ESBL confirmatory test. Therefore, knowing the local prevalence can guide the clinician in navigating the treatment.