KNOW POLYMYXINS BETTER TO COMBAT ANTIMICROBIAL RESISTANCE: MICROBROTH DILUTION METHOD RECOMMENDED ROUTINE TESTING METHOD FOR SCREENING COLISTIN RESISTANCE IN GRAM NEGATIVE BACTERIA:
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Keywords
Colistin, Antimicrobial susceptibility testing (AST), Minimum Inhibitory Concentration (MIC), E- Strip test, Microbroth dilution (MBD), BD Phoenix M-50 Automated system, NCDC (National Centres for disease control)
Abstract
Introduction: With increasing threat of multidrug-resistant organisms (MDROs), Colistin has become popular in clinical practice. Minimum inhibitory concentrations (MICs) are used to monitor Colistin resistance. Microbroth dilution (MBD) stays as the reference testing method for determination of resistance to Colistin and is considered essential for patient management.
Aim: To evaluate performance of MBD over E-strip and automated systems for the determination of Colistin MIC.
Methodology: Study conducted in Microbiology Department of tertiary care hospital of western Uttar Pradesh from March-September 2024. Total of non-repeat clinically significant strains of common Gram-negative bacteria (GNBs) isolated from various clinical specimen of patients received from various departments of hospital for routine Culture Sensitivity testing were processed. MIC was obtained by E-strip, MBD and automated system was interpreted and compared as per NCDC guidelines.
Results: Total 232 GNBs isolated from various clinical specimens were studied for in-vitro Colistin susceptibility by E- Strip method, MBD and BD Phoenix M-50 automated system. Majority of isolates tested were of Escherichia coli 132(55%), followed by Pseudomonas aeruginosa 42(17.5%), Klebsiella spp. 32(13.33%), Acinetobacter baumannii complex 26 (10.83%). The overall Colistin resistance found in 45(18.75%) isolates by gold standard BMD method. Categorical agreement (CA), Essential agreement (EA), Very major error (VME) and Major error (ME) rates for Escherichia coli were 84.85%, 57.14%, 3.78%, and 2.27% by Automated system and 87.88%, 77.67%, 1.51%, 4.54% by E-strip.
Conclusion: Different susceptibility testing methods for Colistin show great variation in their results and BMD may be considered as best choice over E- strip and automated method.
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Dr Sonal Jindal
(MBBS, MD Microbiology) Professor, Department of Microbiology, Rama Medical College, Kanpur, UP.
Dr Ankita Gupta
Assistant Professor, Department of Microbiology, Santosh Medical College and Hospitals, Ghaziabad, U.P.
Dr Sonali Chaturvedi
Assistant Professor, Department of Biochemistry, Maa Vindhyavasini Autonomous Medical College, Mirzapur