Isolation, identification and antibiogram of Oxidase negative non fermenting gram negative bacilli from the clinical specimens

Abstract

Introduction: Oxidase negative nonfermenters are increasingly being isolated from the clinical specimens. Organisms like acinetobacter have been associated with multidrug resistance which makes the treatment difficult. Proper identification and determination of the antibiogram will help in appropriate management of the patients. Aims and Objectives: The study aims to isolate the oxidase negative gram negative bacilli from the clinical specimens and identify them up to the species level and to know the antibiotic susceptibility pattern of these isolates. Materials and Methods: All the clinical specimens obtained in the microbiology department were processed according to the standard protocols. Organisms were isolated and identified by using conventional biochemical testing methods. Antibiotic susceptibility was done by Kirby Bauer disc diffusion testing following the CLSI standards. Results: A total of 153 oxidase negative NFGNB were isolated from the clinical specimens. Out of these Acinetobacter species constituted 146(95%) of the total isolates and the remaining 7(4.5%) were identified as Stenotrophomonas maltophila. The most common species of Acinetobacter isolated was Acinetobacter baumannii complex (Acb- complex), accounting 107(70%) of the total isolates followed by A.lowffii 25(16%), A. junii 10 (7%) and A.hemolyticus 4(2.7%). Majority of the Acb-complex were isolated from respiratory secretions (50.4%) followed by pus samples (30.8%). Stenotrophomonas species were also isolated predominantly from respiratory secretions (71.4%). The most effective antibiotic against these NFGNB were polymyxin B (98% sensitive) followed by tigecycline (96% sensitive). Cotrimoxazole retained its susceptibility against Stenotrophomonas maltophila with all the isolates being susceptible. Conclusion: Speciation of oxidase negative NFGNB has gained importance because of the diverse species involved and their varied antibiogram patterns. Identifying the etiological agents and th