Typing and investigation of some virulence genes with antimicrobial susceptibility of Mannheimia haemolytica strains isolated from respiratory tracts

In this study, it was aimed to determine the biochemical properties, distribution of important virulence genes, antimicrobial susceptibilities and resistance genes of Mannheimia (M.) haemolytica isolates identified from the respiratory tracts of sick and healthy cattles and sheeps. 48 (87.3%) of 55 M. haemolytica isolates found suspicious cultured from naso-pharyngeal and trachea-bronchial swaps were identified as M. haemolytica by Real Time-PCR. According to the differences in arginine-arginine and sorbitol tests, 4 different biochemical profiles were determined in the isolates examined. Three virulence gene profiles were detected in the isolates examined by Real Time-PCR. 37.5%, 33.3%, 12.5% of the isolates examined were identified as I, III and II, respectively. While all virulence-related genes were identified in the isolates with virulence gene profile II, it was determined that there were no nmaA gene in profile I isolates and nmaA and tbpB genes in profile III isolates. At the same time, it was determined that biochemical profile II was associated with disease cases and this was related to arginine-arginine negativity. In addition, it was determined that isolates with virulence gene profile I were associated only with biochemical profile I and that this was due to arginine-arginine negativity, whereas the relationship between arginine-arginine positive isolates and virulence gene profile III was found to be significant. Furthermore, antimicrobial resistance was determined in 9 (18.75%) of the isolates whose antimicrobial susceptibilities and minimum inhibitory concentration (MIC) values were examined by epsilometer test (E-test). One and two isolates were found to be resistant to erythromycin and penicillin, respectively. Also, the antimicrobial resistance was found to tilmicosin and penicillin in one isolate. One of the isolates examined was found antimicrobial resistance to tilmicosin, streptomycin and penicillin, too. One erythromycin-tilmicosin-streptomycin resistant isolate also exhibited resistance to tetracycline. Beside, three erythromycin-tilmicosin-streptomycin-tetracycline resistant isolates was found resistance to penicillin and ampicillin, too. Multiple resistance was observed in the majority of the resistance isolates (66.6%). The macrolide erm42, mphE, msrE genes were found in 6 (66.6%) of the 9 isolates determined to be resistant by E test, and the aminoglycoside resistance gene strA was detected in 5 (55.5%) of these isolates, too. As a result; arginine-arginine negativity and gcp, gs60, tbpB, lktC, adh positive, nmaA negative isolates may be the epidemiological criteria that can be used to differentiate commensal and pathogen M. haemolytica isolates and new studies on the subject should be done. Also, it was conclude that in M. haemolytica isolates, erm42, mphE, msrE genes are responsible for macrolide resistance genes and strA gene is the genes responsible for aminoglycoside resistance and these genes can be detected in total DNA, while the tetH and blaROB-1 genes could not be detected in total DNA. it is suggested that tetH and blaROB-1 genes can be identified in extrachromosomal DNA such as plasmids and transposons, and therefore new studies to investigate other mechanisms related to the antimicrobial resistance gene are required.