Emergence of plasmid-mediated mcr genes from Gram-negative bacteria at the human-animal interface

• Published in: Gut pathogens 2020-11, Vol.12 (1), p.1-54, Article 54
• Main Authors: Javed, Humera, Saleem, Sidrah, Zafar, Aizza, Ghafoor, Aamir, Shahzad, Ahmad Bin, Ejaz, Hasan, Junaid, Kashaf, Jahan, Shah
• Format: Article
• Language: English
• Subjects: Animals; Antibacterial profile; Antibiotic resistance; Antibiotics; Antimicrobial agents; Antimicrobial resistance; Bacteria; Bacterial infections; Carbapenems; Care and treatment; Cephalosporins; Chloramphenicol; Colistin; Colistin resistance; Cotrimoxazole; Deoxyribonucleic acid; DNA; Drug resistance; Drug resistance in microorganisms; E coli; Genes; Genetic research; Gram-negative bacteria; Health aspects; Infection; mcr genes; Medical research; Medicine, Experimental; Minimum inhibitory concentration; Mobile colistin resistance; Moxifloxacin; Multidrug resistance; Pathogens; Phenotypes; Piperacillin; Piperacillin-tazobactam; Plasmid-mediated resistance; Polymerase chain reaction; Poultry; Statistical analysis; Strains (organisms); Tazobactam; Urine; Veterinary medicine
• ISSN: 1757-4749; 1757-4749
• DOI: 10.1186/s13099-020-00392-3

Background The global emergence of plasmid-mediated colistin resistance (Col-R) conferred by mcr genes in gram-negative rods (GNRs) has jeopardized the last treatment option for multidrug-resistant bacterial infections in humans. This study aimed to assess the emergence of mcr gene-mediated Col-R in GNRs isolated from humans and animals in Pakistan. Methods Animal and clinical specimens collected from various sources were prospectively analysed using standard microbiological procedures. Pathogens were identified using the API 20E and API 20NE systems (bioMerieux). Minimum inhibitory concentration (MIC) against colistin was determined using the MIC detection methods, and multiplex polymerase chain reaction (PCR) was used to amplify the mcr-1 to mcr-5 genes. Results We isolated 126 (88.1%) animal and 17 (11.9%) human Col-R phenotypes, among which there was a significant association (P < 0.01) of Escherichia coli and Proteus mirabilis with animals and of Acinetobacter baumannii with humans. Animal strains exhibited statistically significant (P < 0.05) resistance to co-trimoxazole, chloramphenicol, and moxifloxacin, and the human pathogens exhibited statistically significant (P < 0.05) antibiotic resistance to cephalosporins, carbapenems, and piperacillin-tazobactam. For Col-R strains, MIC.sub.50 values were > 6 [micro]g/mL and > 12 [micro]g/mL for human and animal isolates, respectively. mcr genes were detected in 110 (76.9%) bacterial strains, of which 108 (98.2%) were mcr-1 and 2 (1.8%) were mcr-2. Conclusions The detection of a considerable number of mcr-1 and mcr-2 genes in animals is worrisome, as they are now being detected in clinical pathogens. The acquisition of mcr genes by colistin-susceptible bacteria could leave us in a post-antibiotic era. Keywords: Antibacterial profile, Antimicrobial resistance, Colistin resistance, mcr genes, Mobile colistin resistance, Plasmid-mediated resistance