“AmpC beta-lactamases among Pseudomonas and Acinetobacter species isolates, from a tertiary hospital of North India”

Background: Production of AmpC beta-lactamases in isolates of Pseudomonas and Acinetobacter species have resulted into therapeutic failure and consequently increased mortality and morbidity. Objective: As the reports regarding the prevalence of AmpC beta-lactamases in Pseudomonas and Acinetobacter are fragmentary from India, the present study was conducted to determine occurrence of AmpC beta-lactamases in these pathogenic non-fermenters. Materials and methods: Ninety non-duplicate Pseudomonas and Acinetobacter isolates, resistant to any of the third-generation cephalosporin were collected during October 2010 to September 2011. Antibiotic-susceptibility test was performed by disc diffusion method. Cefoxitin-resistant isolates were subjected to modified-three dimensional extract test for confirmation of AmpC beta-lactamases. Results: Pseudomonas spp. showed highest resistance to cefoxitin (91.78%) followed by ceftriaxone (78.05%), cefepime (72.41%) and then cefoperazone/sulbactam (56.31%); while in case of Acinetobacter spp. maximum resistance was noted for cefoxitin (94.12%) and cefotaxime (94.12%). Resistance against cefepime was noted in 88.24% isolates followed by cefoperazone/sulbactam (71.43%). 83 (92.22%) isolates showed resistance against cefoxitin. Out of total 83 cefoxitin-resistant isolates, 66 (79.52%) were tested positive by modified three-dimensional extract test. Conclusion: Study shows high prevalence of AmpC beta-lactamases in cefoxitin-resistant isolates of Pseudomonas and Acinetobacter species.