Colistin is an important drug of last resort against lethal infections with multidrug-resistant gram-negative bacteria, this antibiotic interacts on phosphate groups of lipopolysaccharides present on the outer membrane of gram-negative bacteria. This first mechanism of transferable colistin resistance involves a gene called mcr-1. Here, we described different tools such as Colistin susceptibility test, Minimal Inhibitory Concentration to find the colistin profiles of Mannheimia haemolytica and Pasteurella multocida serogroup A Moroccan strain isolated from nasal swabs and lung taken from sheep, goat and cattle with respiratory diseases during January 2015 to December 2017 in six different regions, in addition, we investigated either real time PCR to detect mcr-1 gene. Antimicrobial sensitivity test, was achieved for Forty-one isolates, the resistance rates of isolates from Pasteurellaceae species were between 59 and 71%, which respectively correspond to Mannheimia haemolytica and Pasteurella multocida segroup A. The sensitive ratios were between 29 and 41% which respectively correspond to Pasteurella multocida segroup A and Mannheimia haemolytica. Also, the MIC test was done against colistin, the results showed a resistant profile with a MIC >=64 μg/ml except for 3 strains from ruminants which have a value <2 μg/ml. The real time PCR screening test was detected with ct values ranging from 23 to 31 and confirmed the results obtained by MIC test. To our knowledge the present study is the first study which reports the resistance to colistin in Pasteurellaceae species strains isolated from ruminants in Morocco, our results suggest the necessity and the urgency for establishing a national program for monitoring antibacterial resistance against colistin.

To Cite This Article: Sebbar G, Fellahi S, Filali-Maltouf A and Belkadi B, 2021. Detection of colistin resistance in Mannheimia haemolytica & Pasteurella multocida isolates from ruminants in Morocco. Pak Vet J, 41(1): 127-131. http://dx.doi.org/10.29261/pakvetj/2020.077