"Antibiogram Picture Guide for the Medical Microbiology Practitioner - Part 1: Extended-Spectrum Beta-Lactamases (Esbls) and Cephalosporinases (Ampcs) in Enterobacterales"

Abstract

Antibiotic resistance is a global, far-reaching phenomenon. Natural resistance to antibiotics, expressed or inducible, is common in Enterobacterales and can occur through the production of different enzymes such as penicillinases, ESBLs or cephalosporinases. In association with other resistance mechanisms, strains that lead to untreatable infections can emerge. Improper infection control measures are responsible for the selection and spread of these strains. The dissemination of acquired Extended-Spectrum Beta-Lactamases (ESBLs) across the globe is well known, a wide spectrum of enzymes being responsible for their different hydrolytic activity. Another important set of enzymes, the cephalosporinases (with the chromosomal cephalosporinase AmpC as the most important), are also concerning as their hyper-expression can alter wide spectrum beta-lactams, like carbapenems. These mechanisms can be readily observed through phenotypic tests, like antibiotic interactions on the disk diffusion antibiogram, or derepression / inhibition of enzymes using key antibiotics. Keywords: ESBL, cephalosporinase, AmpC, carbapenemase, cloxacillin, oxacillin, antibiotic resistance, antibiogram, Enterobacterales