Molecular Typing, Antibiogram and PCR-RFLP Based Detection of Complex Isolated from .

Motile Aeromonas septicemia is a common bacterial disease that affects and causes tremendous economic losses globally. In order to investigate the prevalence, molecular typing, antibiogram and the biodiversity of complex, a total of 250 tilapia () were collected randomly from 10 private tilapia farms (25 fish/farm) at El-Sharkia Governorate, Egypt. The collected fish were subjected to clinical and bacteriological examinations. The majority of infected fish displayed ulcerative necrosis, exophthalmia, and internal signs of hemorrhagic septicemia. The prevalence of complex was 13.2%, where the liver was the most predominant affected organ (54.1%). Polymerase chain reaction (PCR) was used to verify the identification of complex using one set of primers targeting B as well as the detection of virulent genes (A, , and ). All isolates were positive for the B-conserved gene and harbored A and virulence genes. However, none of those isolates were positive for the gene. The antimicrobial sensitivity was carried out, where the recovered strains were completely sensitive to ciprofloxacin and highly resistant to amoxicillin. All retrieved strains showed the same phenotypic characteristics and were identical based on the restriction fragment length polymorphism (RFLP). Experimentally challenged fish presented a high mortality rate (76.67%) and showed typical signs as in naturally infected ones. In conclusion, the synergism of phenotypic and genotypic characterization is a valuable epidemiological tool for the diagnosis of complex. RFLP is a fundamental tool for monitoring the biodiversity among all retrieved strains of .