Investigation of Mobile Colistin Resistance (mcr) Genes among Carbapenem Resistance Pseudomonas Aeruginosa Isolates from Bovine Mastitis in Mashhad, Iran

Background: The most severe pathology affecting the dairy industry is bovine mastitis (BVM). Pseudomonas aeruginosa is widely associated with several infections, including the BVM. The current study aimed to investigate the incidence of carbapenemase and mobile-colistin resistance (mcr) genes among resistant P. aeruginosa isolates from Mashhad, northeast Iran.Methods: The current study was conducted on archived P. aeruginosa isolates from mastitis. The antimicrobial susceptibility testing was performed; the carbapenem resistance isolates were subsequently sought to demon-strate the carbapenemase-producing isolates using the modified-carbapenem inactivation method. In addition, the colistin broth disc elution method was carried out to determine the frequency of resistance against colistin. Finally, resistance isolates were further tested for detecting related carbapenemase and mobile-colistin resistance (mcr) genes, including blaNDM, blaOXA-48, blaVIM, blaKPC, blaIMP, and mcr1-5, using the polymerase chain reaction procedure (PCR).Results: Among carbapenem-tested antibiotics, meropenem has revealed the least activity (8 %); on the other hand, aztreonam, gentamycin, and tobramycin were 100 % effective. Two isolates (4 %) have shown colistin resistance (with MIC >= 4 mu g/mL). The PCR analysis has displayed the high frequency of blaVIM among (43/43) meropenem resistance isolates. Also, the presence of mcr-2 was detected for two colistin resistance isolates.Conclusion: The substantial resistance to carbapenems and emerging colistin resistance in veterinary have been observed. Thus, the following antimicrobial stewardship in farm animals reduces the increasing multi-drug resistance of P. aeruginosa isolates.