Evaluation of Antibiotic Resistance in the Mannhemia hemolytica Isolatesand Their Association with Class I and II Integrons

BACKGROUND AND OBJECTIVESMannhemia hemolytica is a gram-negative, coccobacillus. As a secondary pathogen, it plays animportant role in the progression of severe pleuropneumonia in cattle, sheep and goats. Due to theexcessive use of antibiotics for the treatment of pleuropneumonia, M. hemolytica has become resistantto a large number of antibiotics. Resistance genes have been associated with small plasmids andtransposons. In this research, we investigated the resistance to common antibiotics used against M.hemolytica infection and class I and II integrons and their relationship with antibiotic resistance.MATERIALS AND METHODS۳۵ M. hemolytica isolates from the lungs of sheep that stored in the archives of bacteriologydepartment of the Shiraz Veterinary Faculty were used. After the phenotypic confirmation of theisolates with biochemical tests (catalase, oxidase and hemolysis) resistance to streptomycin,chloramphenicol, penicillin, and gentamicin was evaluated by disk diffusion method. Then, thepresence of class I and II integrons were checked by PCR.RESULTS AND DISCUSSIONAccording to these results, the highest resistances were observed to the gentamicin, erythromycin andstreptomycin and the lowest resistances of the isolates were shown to tylosin and amoxicillin. ThePCR results for the presence of class I and II integrons showed that among the ۳۵ isolates, ۲۴ isolateshad class I integron and ۳۰ isolates had class II integron. The statistical analysis of the results showedthat there is no significant relationship between the presence of class I integrons and the increase inrelative resistance to the studied antibiotic (P>۰/۰۵). Conversely, the frequency of resistance toamoxicillin was significantly higher in strains lacking class II integron (P=۰/۰۱۷). No significantcorrelation was observed between the simultaneous presence of class I and II integrons and thefrequency of resistance to any of the studied antibiotics.CONCLUSIONAccording to the different researches class I and II integrons play a key role in the antibioticresistance of M. hemolytica isolates. Also, with the passage of time and genetic exchanges betweenM. hemolytica isolates, antibiotic resistance genes are transferred and antibiotic resistance increases.There is a need for further study and strict regulations to maintain the effectiveness of drugs andprevent the spread of antibiotic resistance

کلیدواژه ها:

Resistance ، Mannhemia hemolytica ، Pleuropneumonia ، Integron ، PCR