Detection of Virulence factors of Pseudomonas species isolated from fresh water fish by PCR

Abstract

This study was conducted on 100 diseased Nile tilapia (O. niloticus) fish of various sizes collected fromdifferent fish markets in Kaliobia Governorate to estimate the prevalence of Pseudomonas infection anddetection of some virulence genes in the isolated P. aeruginosa strains. The results of bacteriologicalexamination revealed that the prevalence of Pseudomonas septicemia with Pseudomonas speciesisolation was 17.0% (17 100 examined fish). These cases were attributed to P. anguilliseptica; P.aeruginosa and P. fluorescens (14/43.7%; 12/37.5% and 6/18.8%), respectively. In addition, 32Pseudomonas species were isolated, 11from liver samples (34.4%); 10 from kidney samples (31.2%); 6from gill samples (18.8%) and 5 from skin samples (15.6%). Moreover, 14 P. anguilliseptica wereisolated with an incidence of 35.7%, 28.6%, 21.4% and 14.3% followed by 12 P. aeruginosa 33.3%,25%,16.7% and 25% respectively; 6 P. fluorescens 33.3%; 50.0%,16.7% and 0.0% from the liver,kidney, gill and skin samples respectively. The in-vitro antimicrobial sensitivity test showed that theisolated Pseudomonas strains were sensitive to gentamycin; enrofloxacin; norfloxacin; ciprofloxacinand florphenicol. Meanwhile; they were intermediate sensitive for doxycycline; sulfa-trimethoprim;oxytetracycline; nalidixic acid and streptomycin. In contrast, they were resistant for cefotaxime;erythromycin; amoxicillin; methicillin; oxacillin and ampicillin. Moreover, the PCR results revealedthat, opr L and exo S virulence genes were detected in all six studied strains (100.0%). Meanwhile, phzM virulence gene was detected in 5 out of 6 studied strains (83.3%) and tox A virulence gene wasdetected in 4 out of 6 studied strains (66.7%) i.e., all studied strains were Ps. aeruginosa and all of themwere virulent strains