DIRECT ANTIMICROBIAL SUSCEPTIBILITY TESTING OF GRAM NEGATIVE BACILLI FROM POSITIVE BLOOD CULTURES

Abstract

Conventional blood culture and susceptibility pattern takes around 48 hours after blood culture bottles turns positive on Bact/ALERT system. Rapid initiation of antimicrobial therapy is required in management of sepsis patients to reduce its adverse effects on mortality and morbidity. Objective of this study was to execute rapid and accurate direct antimicrobial susceptibility testing (DST) of gram negative bacilli on positive blood culture bottles by the disk diffusion method and compare the results with those of standard antimicrobial susceptibility testing (AST). This prospective study was performed at the Saveetha Institute of Medical and Technical Science, Sriperumbudur, with mono-bacterial gram negative bacilli. 100-gram negative bacilli (GNB) samples were agged from positive blood cultures with duration of 3 months. Both DST and AST results were interpreted, and the isolates were identied by vitek2. On 100 GNB isolates, the most common organism was Escherichia coli, followed by Klebsiella pneumoniae (27%), Pseudomonas aeruginosa (11%), Acinetobacter baumanii (8%), Salmonella typhi (7%), Enterobacter cloacae (3%), Acinetobacter lwof(3%) and Serratia marsacens. The DST and AST correlations were found to be in 99% categorical agreement, with 1% minor error, 0% major error, and 0% very major error. The concentration of bacterial inoculums impacts the results between DST and AST. DST reduces the crucial time from 24 to 48 hours for patients with bloodstream infections treated with empirical antibiotic therapy, which may or may not be resistant. DST initiates early antibiotic therapy that is susceptible to treating a bloodstream infection or sepsis. Aims and Objective: To evaluate categorical agreement of antimicrobials between DST and AST from positive blood culture bottles by Kirby-Bauer disk diffusion method. Materials and methods: A prospective study was conducted in tertiary care hospital, with sample size of 100 gram negative bacilli from positive blood culture bottles in patients suspected with blood stream infections during the period from October 2022 to December 2022. RESULTS: Out of 100 gram negative bacilli , Escherichia coli (37%) was the most common isolate, followed by Klebsiella pneumonia (27%), Pseudomonass aeroginosa (11%), Acinetobacter baumanii (8%), Salmonella typhi (7%), Enterobacter clocae (3%), Acinetobacter lw of(3%) and Serratia marsacens (2%). Conclusion: During this study, there was 99% categorical agreement between DST and AST. Earlier treatment with antimicrobials can reduce the mortality and morbidity in bacteraemia patients