Document Type : New and original researches in the field of Microbiology.
Authors
1
Department of Medical Microbiology and Immunology, Faculty of Medicine, Menoufia University, Egypt
2
Department of Clinical Pathology, National Liver Institute, Menoufia University, Egypt
3
Department of Clinical Microbiology and Immunology, National Liver Institute, Menoufia University, Egypt
Abstract
Background: Acinetobacter baumannii (A. baumannii) is one of the most important nosocomial pathogen. With the introduction of colistin as a last resort in treatment of A. baumannii, resistant strains. Using combined antibiotics could increase the success of treatment and reduce resistance. Objectives: To assess potential in-vitro synergistic activity of colistin when combined with (vancomycin, teicoplanin, rifampicin, tigecycline, meropenem, amikacin, and ceftazidime) against colistin resistant A. baumannii (CRAB). Also, to screen the prevalence of plasmid mediated colistin resistance (mcr) genes (mcr-1 to mcr-5) in colistin resistant isolates. Methodology: A. baumannii strains were isolated from different microbial specimens. Antibiotic susceptibility testing was done for all isolates by disk diffusion method while broth micro dilution (BMD) was performed to determine colistin minimum inhibitory concentration (MIC). Genotypic detection of mcr genes was done using multiplex PCR. Checkerboard method was done to detect potential synergistic activities between colistin and other tested antibiotics against CRAB. Results: A total of 94 A. baumannii strains were isolated from 373 different clinical samples. Colistin resistance was detected in 44/94 (46.8%) of isolated A. baumannii. Only 2 out of 44 CRAB (4.5%) carried mcr-1 gene and neither of other mcr genes could be detected. All isolated CRAB were resistant to 7 tested antibiotics by BMD. But when colistin was included in a checkerboard pattern, colistin-based combinations with vancomycin, meropenem, rifampicin, teicoplanin and ceftazidime showed synergy in 93.2%, 90.9%, 88.7%, 86.4% and 79.5% of isolated CRAB respectively. For both tigecyclin and amikacin more than 90% of CRAB showed indifference in combination with colistin. Conclusion: Further studies are needed to determine the ability of colistin based antimicrobial combinations as an alternative therapy to treat CRAB infections and confirm that synergy.
Keywords
Main Subjects
)
View on SCiNiTO