Detection of colistin resistant Gram negative bacilli in intensive care unit patients admitted to Ain Shams University Hospitals

Abstract

Background: Colistin is the last choice for serious infections caused by multidrug-resistant Gram negative bacteria and one of the prominent causes for spreading the resistance is Plasmid-borne Mobile Colistin Resistance (mcr). Broth microdilution method (BMD) is the reference tool for colistin minimum inhibitory concentrations (MIC) determination, but it has many obstacles, so commercial BMD methods had been developed that are more user-friendly than the reference method and (Liofilchem ® ComASPTM) is one of them, which we used to determine colistin MIC in this study. Objective: To detect colistin resistant Gram negative bacilli (GNB) by ComASPTM colistin (formerly Sensi Test™Colistin) among Intensive Care Units (ICUs) patients admitted to Ain Shams university hospitals and to screen the presence of mcr-1 gene by Polymerase Chain Reaction (PCR) in Colistin resistant isolates. Method: This Observational cross-sectional study was performed in the Medical Microbiology and Immunology Department, Faculty of Medicine, Ain Shams University between June 2019 to November 2019. One hundred isolates of Gram negative bacilli were obtained from patients admitted at different ICUs of Ain Shams University Hospitals. Full identification was done by conventional microbiological methods, Then MIC was measured for all isolated organisms by using commercial BMD ComASPTM colistin, PCR was done for colistin resistant isolates to detect mcr-1 gene. Results: 60% of the GNB isolates were K.pneumoniea. Colistin resistance was 14% among 100 GNB, 35.7% of these colistin resistant were K.pneumoniea obtained from urine samples. Prevalence of mcr-1 gene was 7.1%. Conclusion: Commercial BMD ComASPTM colistin is simple and uncomplicated method for detection colistin susceptibility.