Antibacterial activity of colistin and tigecycline against Enterobacteriaceae and Acinetobacter clinical isolates in Sohag University Hospital

Document Type : Original Article

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Department of Medical Microbiology and Immunology , Faculty of Medicine, Sohag University, Egypt

Abstract

Background: Enterobacteriaceae are very common in nosocomial and community-acquired illnesses. These organisms have developed a progressive resistance to a number of antibiotic classes, including carbapenems, which are frequently used as a last resort to treat infections caused by isolates that produce extended-spectrum β-lactamases (ESBLs) all over the world. The purpose of this investigation was to determine the in vitro susceptibility of strains of Acinetobacter and Enterobacteriaceae to tigecycline and colistin, as well as to identify the colistin resistance gene mcr-1 in each isolated strain.
Methodology: Enterobacteriaceae and Acinetobacter strains from different clinical samples were isolated on suitable media and identified manually. Confirmation of manual identification of bacterial isolates, identification to species level and determination of antibiotic susceptibility was done using vitek-2 system. Evaluation of invitro susceptibility of Enterobacteriaceae and Acinetobacter strains to colistin by colistin elution test and tigecycline by disc diffusion test. Detection of colistin resistance gene mcr-1 in all isolated strains by conventional PCR and comparing colistin resistance phenotypically and genotypically. Results: Among the study strains 16 (14.3%) were resistant to colistin while 13 (11.6%) were resistant to tigecycline. The most common organism to be resistant to colistin was Kl. Pneumoniae (37.5%), followed by E. coli (31.3%). Higher resistance to tigecycline was observed among E. coli (46.2%) followed by K. pneumoniae (23.1%). mcr-1 gene was detected in eight (7.14%) strains, from which 50 % are phenotypically resistant to colistin. Conclusion: there is increasing concern about the emergence of clinical MDR microorganisms resistant to colistin, an antibiotic of last resort, since it causes infectious illnesses that are thus challenging to treat.

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