Prevalence of extended-spectrum beta-lactamases, AmpC beta-lactamase, and metallo-beta-lactamase producing Pseudomonas aeruginosa and Acinetobacter baumannii in an intensive care unit in a tertiary care hospital

Background: Resistance to broad-spectrum beta-lactams, mediated by extended-spectrum beta-lactamases (ESBL), AmpC beta-lactamase, and metallo-beta-lactamase (MBL) enzymes, is an increasing problem worldwide. Aim of the study: This study was undertaken to detect ESBL, AmpC beta-lactamase and metallo-beta-lactamase producing Pseudomonas aeruginosa and Acinetobacter species from the endotracheal aspirates. Materials and Methods: A prospective study was performed over a period of 15 month in a tertiary care hospital. A total of 26 clinical isolates of P.aeruginosa and 40 of Acinetobacter species were tested for the presence of ESBL, AmpC beta-lactamase, and metallo-beta-lactamase enzyme. Detection of ESBL was done by the combined disk diffusion method as per Clinical and Laboratory Standards Institute (CLSI) guidelines, and MBL was detected by imipenem-Ethylenediaminetetraacetic acid (EDTA) combined disk method. Isolates showing reduced susceptibility to cefoxitin (30 μg) disk were considered 'screen positive' for AmpC beta-lactamases and selected for detection of plasmid-mediated AmpC by the AmpC disk test. Results : 42.30% isolates of P.aeruginosa were positive for ESBL while 53.85% were MBL producers. Among 39 isolates of Acinetobacter baumannii, 43.59% were AmpC producers while 48.72% were MBL-producing strains. Conclusion: The study emphasizes the high prevalence of multidrug-resistant P.aeruginosa and A.baumannii producing beta-lactamase enzymes of diverse mechanisms. Thus, proper antibiotic policy and measures to restrict the indiscriminative use of cephalosporins and carbapenems should be taken to minimize the emergence of this multiple beta-lactamase-producing pathogens.