OCCURRENCE AND DETECTION OF EXTENDED SPECTRUM β-LACTAMASE AND AmpC β-LACTAMASE IN CLINICAL ISOLATES OF Pseudomonas aeruginosa AND Acinetobacter baumanii BY INHIBITOR BASED METHOD

Background & Objective: Pseudomonsa aeruginosa and Acinetobacter baumanii are common non-fermenters which have emerged as the most common opportunistic pathogens in recent years. Persistent exposure of Pseudomonas aeruginosa and Acinetobacter baumanii to β-lactam antibiotics leads to acquired resistance through mutation and over production of various enzymes which also include AmpC or class C β-lactamases and extended spectrum β-lactamase (ESBL). For clinical microbiologists, detection of ESBL and AmpC-mediated resistance together poses a problem because the phenotypic tests may be misleading; resulting in misreporting and treatment failures.Methods: A total number of 94 consecutive, non-repetitive, imipenem sensitve clinical isolates of Pseudomonas aeruginosa (n=64) and Acinetobacter baumanii (n=30) obtained over a period of 6 months, were screened for β-lactamase production by nitrocefin disc and production of ESBL and AmpC β-lactamase is detected by Inhibitor based test.Results: A total of 50 out of 94 isolates were positive for β-lactamase production; of which 17 (15.98%) and 22(20.68%) were ESBL and AmpC β-lactamase producers respectively.Conclusion: The inhibitor based method is useful for detection of ESBL and AmpC β-lactamase and helpful to differentiate ESBL from AmpC producers. As high incidence of ESBL and AmpC β-lactamase production in gram negative isolates is alarming and urgent actions needs to be taken for therapeutic and infection control measure. This is only possible if correct detection of ESBL and AmpC β-lactamase is done in clinical laboratory.