Yersinia ruckeri is the causative pathogen of a systemic disease called enteric red mouth disease. It can infect different fish species causing considerable economic losses in fish farms. This research was conducted to evaluate antimicrobial susceptibility of isolated Yersinia ruckeri (Y. ruckeri) from diseased Nile tilapia as well as molecular detection of some antibiotic resistance genes was carried out. In this study, a total of ninety-six Y. ruckeri isolates were recovered from 150 examined fish samples.
Results of antibiotic sensitivity test revealed that isolates were sensitive to ciprofloxacin (63.5%), difloxacine (70.8%) and sulphamethoxazole-trimethoprim (55.2%), but isolates were moderately sensitive to enrofloxacin (52%), erythromycin (82.2%) and doxycycline (61.4%). Meanwhile, high resistance to oxytetracycline, gentamycin, amoxicillin and flumequine was observed. Antibiotic resistance genes were screened in 5 isolates by multiplex PCR and recorded resistance genes qnrA, blaTEM, aadA1 and ereA at 516, 516, 484, 420 bp respectively in all isolates. This observation revealed that Y. ruckeri isolates have multiple resistance to antibiotics and hence difficult
control and treatment of disease. Consequently, there is a necessity to develop an innovative strategy for controlling Yersiniosis outbreaks in diseased farms.