Metallo-beta-lactamase production among Pseudomonas species and Acinetobacter species in costal Karnataka

Background and objectives: The emergence of multidrug resistance among Pseudomonas species and Acinetobacter species is a notable threat. Acquisition of the metallo-beta-lactamase (MBL) gene is an important mechanism of broad-spectrum-beta-lactam resistance. The aim of the study is to detect the prevalence of MBL among Pseudomonas spp. and Acinetobacter spp. isolated from various clinical samples collected from different age groups. Materials and Methods: A total of 54 meropenem resistant Pseudomonas spp. and Acinetobacter spp., tested by the disc diffusion method, were included in the study. The strains were isolates obtained from burn wounds, ulcers, sputum and urine collected from the patients aged from one year to 90 years. The strains were identified up to the species level and the EDTA disk synergy test was used, with simultaneous testing of different beta-lactams (meropenem and aztreonam). Results: Of the 54 meropenem resistant strains, 16(30%) were MBLs producing isolates, of which 13(81%) were isolates of samples from male patients and 3(19%) were those from female patients. More strains of MBLs [13(81%)] were seen in the age group of 40-75 years and only few strains of MBLs [3(19%)] were isolated from samples in the age group below 40 years and above 75 years. MBLs were more prevalent in respiratory specimens 4(45%) and less prevalent in urine specimens 3(21%) when compared to other specimens. Pseudomonas putida 7(64%) had more number of MBLs producing organisms as compared to other species of Pseudomonas. The isolates producing MBLs were more resistant to Tobramycin [16(100%)] and Gentamicin [15 (94%)] and were less resistant to Piperacillin [10(63%)] than meropenem -non susceptible isolates which did not produce MBLs. Conclusion: The rapid discrimination of MBL producers is worrisome and necessitates the implementation of not just surveillance studies, but also the proper and judicious selection of antibiotics, especially carbapenems.