Abstract

The potential transfer of antimicrobial agent residues and resistance genes in foods between bacteria creates a significant risk for public health. This research was objectived to investigate the susceptibility of Mannheimia haemolytica isolates from the respiratory tract of animals to antibiotics and antibiotic resistance genes. In the study, 48 Mannheimia haemolytica isolates were cultured by conventional methods. The susceptibilities of the isolates to antimicrobial agents were investigated comparatively by disk diffusion and e-test methods. The presence of antibiotic resistance genes in isolates found to be resistant to various antimicrobial agents was investigated by Real-Time PCR method. In this research, 66.6% of the 9 isolates detected to be resistant to antibiotics were resistant to more than one antibiotic. The macrolide resistance genes (erm42, mphE, msrE) were detected in 6 (66.6%) isolates found resistant by E test. The aminoglycoside resistance gene (strA) was also found in 5 of these 6 isolates, while none of the blaROB-1, tetH and sulII genes were detected in these isolates. Isolates resistant to macrolide group antibiotics had at least one of the erm42, mphE and msrE genes, while all isolates resistant to aminoglycoside group antibiotics had the strA gene. Furthermore, MIC values were higher in isolates with resistance genes. In conclusion, this study showed that macrolide and aminoglycoside resistance genes are responsible for the phenotypic resistance of Mannheimia haemolytica to these antibiotic groups. Furthermore, tetH, blaROB-1 and sulII genes are thought to be transported via extrachromosomal genetic elements. With this study, it was concluded that a broad perspective approach is required in the management of infections caused by Mannheimia haemolytica, in the protection of public health and in the fight against antibiotic resistance, and that it is important to conduct new studies to investigate alternative resistance mechanisms.

Key words: Antimicrobial resistance genes, one health, real time-PCR, e-test,MIC