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Faculty Sponsor

Dr. Shree S. Dhawale, Dr. Ahmed Mustafa


Department of Biology

University Affiliation

Indiana University – Purdue University Fort Wayne


Tilapia and coho salmon are commercially important aquaculture fish. Antibiotics and antibiotic resistant bacteria have been detected in the aquaculture system. These two fish species were tested for presence of antibiotic resistant microbes in their gut samples. The objectives were to look for the presence of antibiotic resistant bacteria their guts, determine antibiotic resistance phenotype of resistant bacterial isolates and further test for the presence of plasmids in selected resistant isolates. Tilapia (Oreochromis niloticus) and coho salmon (Oncorhynchus kisutch) were obtained from hatcheries and maintained in a fish laboratory at IPFW. The antibiotic resistant bacteria were isolated on the basis of their resistance to ampicillin. Out of 8 tilapia 6 (75%) yielded bacterial isolates with antibiotic resistance. As for salmon, out of 8 only 3 (38%) yielded antibiotic resistant isolates. The results indicated prevalence of antibiotic resistant bacteria in fish guts. Comparatively tilapia had higher percentage (75%) of fish with resistant isolates. Antibiotic sensitivity tests were performed for all 45 bacterial isolates using six additional antibiotics -penicillin , vancomycin, chloramphenicol , tetracycline , streptomycin and gentamicin. Many isolates showed multidrug resistance. From this group six bacterial isolates were selected to test for the presence of plasmid because plasmids are known to carry and spread antibiotic resistant genes. Only two bacterial isolates were found to have plasmids which suggest that antibiotic resistance in many isolates is of chromosomal origin. Two isolates containing plasmids were identified as Peudomonas alcaligens or P. pseudoalaligens and Aeromonas salmonicida subspecies smithia from tilapia. At this point we don’t know whether the plasmids found in these two isolates are responsible for conferring antibiotic resistance to these microbes, future studies are necessary. However, the presence of antibiotic resistant bacteria is worrisome because fish handlers and consumers may acquire resistant bacteria and transfer resistance genes to pathogenic bacteria.


Biology | Life Sciences

Do Hatchery-raised Tilapia and Coho Salmon Have Antibiotic Resistant Bacteria in Their Guts?

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