Document Type : New and original researches in the field of Microbiology.
Authors
1
Department of Medical Microbiology and Immunology, Faculty of Medicine, Cairo University, Cairo, Egypt
2
2Department of Pathology, College of Medicine, Imam Mohammad Ibn Saud Islamic University, Riyadh, Saudi Arabia; Department of Medical Microbiology and Immunology, Faculty of Medicine, Menoufia University, Egypt
3
Microbiology Department, Riyadh Regional Laboratory & Blood Bank, Riyadh, Saudi Arabia; College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
4
Microbiology Department, Riyadh Regional Laboratory & Blood Bank, Riyadh, Saudi Arabia
5
Genetic Section, Research Department, Health Sciences Research Center, Princess Nourah bint Abdulrahman University
6
Medical Student, College of Medicine, Imam Mohammad Ibn Saud Islamic University, Riyadh, Saudi Arabia
Abstract
Background: Colistin is a last therapeutic option for carbapenem-resistant Enterobacterales (CRE) infections. Emergence of plasmid-mediated mcr colistin resistance genes poses a potential threat for treatment of these infections. Integrons are known for their central role in antibiotic resistance. Objectives: The aim of the study was to survey the prevalence of mcr-genes and integrons in colistin-resistant Enterobacterales isolates and to assess methods for colistin susceptibility testing. Methodology: Eighty-six colistin-resistant Enterobacterales strains isolated from different clinical samples of hospitalized patients at King Saud Medical City, Riyadh, from February 2020 to December 2021 were included in the study. Antimicrobial susceptibility testing (AST) was done using Phoenix BD, Sensititre broth microdilution test, and the standard broth microdilution method (BMD). Screening for mcr-1 and mcr-2 genes and class I, II and III integrons was done by PCR. Results: Majority of the colistin-resistant isolates (97.6%) were Klebsiella pneumoniae. Categorial agreement (CA) of Sensititre broth microdilution test and Phoenix BD test with the reference BMD method for colistin susceptibility was 95.3% and 89.5%, respectively. Only 3 isolates (3.5%) were found positive for mcr-1 gene. Class I and II integrons were detected in 79. % and 30.2% of the isolates, respectively. Conclusion: Sensititre broth microdilution test displayed a good performance for colistin AST, while Phoenix BD results should be confirmed by another method. Plasmid borne mcr-mediated resistance plays a minor role in colistin resistance among Klebsiella pneumoniae isolates. The alarming high prevalence of antibiotic resistant class I and II integrons in the studied isolates warrants further investigations.
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