Aim: The aim of this study is to identify antibiogram and heavy metal resistance pattern of Aeromonas hydrophila and Edwardsiella tarda isolated from red hybrid tilapia (Oreochromis spp.) coinfected with motile aeromonas septicemia and edwardsiellosis in four commercial fish farms.

Materials and Methods: A. hydrophila and E. tarda were isolated using glutamate starch phenol red and xylose lysine deoxycholate (Merck, Germany) as a selective medium, respectively. All the suspected bacterial colonies were identified using conventional biochemical tests and commercial identification kit (BBL Crystal, USA). Susceptibility testing of present bacterial isolates to 16 types of antibiotics (nalidixic acid, oxolinic acid, compound sulfonamides, doxycycline, tetracycline, novobiocin, chloramphenicol, kanamycin, sulfamethoxazole, flumequine, erythromycin, ampicillin, spiramycin, oxytetracycline, amoxicillin, and fosfomycin) and four types of heavy metals (mercury, chromium, copper, and zinc) were carried out using disk diffusion and two-fold agar dilution method, respectively.

Results: Three hundred isolates of A. hydrophila and E. tarda were successfully identified by biochemical tests. Antibiotic susceptibility testing results showed that 42.2% of the bacterial isolates were sensitive to compound sulfonamides, sulfamethoxazole, flumequine, oxytetracycline, doxycycline, and oxolinic acid. On the other hand, 41.6% of these isolates were resistant to novobiocin, ampicillin, spiramycin, and chloramphenicol, which resulted for multiple antibiotic resistance index values 0.416. Among tested heavy metals, bacterial isolates exhibited resistant pattern of Zn²⁺ > Cr⁶⁺ > Cu²⁺ > Hg²⁺.

Conclusion: Results from this study indicated that A. hydrophila and E. tarda isolated from coinfected farmed red hybrid tilapia were multi-resistant to antibiotics and heavy metals. These resistant profiles could be useful information to fish farmers to avoid unnecessary use of antimicrobial products in the health management of farmed red hybrid tilapia.

Keywords: antibiotic, edwardsiellosis, heavy metal, motile aeromonas septicemia, multiple antibiotic resistance index, red hybrid tilapia.

1. Lee, S.W., Najiah, M., Wendy, W. and Nadirah, M. (2010) Antibiogram and heavy metal resistance of pathogenic bacteria isolated from moribund cage cultured silver catfish (Pangasius sutchi) and red hybrid tilapia (Tilapia sp.). Front. Agric. China, 4(1): 116-120. [Crossref]

2. Shetty, M., Maiti, B., Venugopal, M.N., Karunasagar, I. and Karunasagar, I. (2014) First isolation and characterization of Edwardsiella tarda from diseased striped catfish, Pangasianodon hypophthalmus (Sauvage). J. Fish Dis., 37: 265-271. [Crossref] [PubMed]

3. Zhang, D., Xu, D.H. and Shoemaker, C. (2016) Experimental induction of motile Aeromonas septicemia in channel catfish (Ictalurus punctatus) by waterborne challenge with virulent Aeromonas hydrophila. Aquac. Rep., 3: 18-23. [Crossref]

4. Lee, S.W., Najiah, M., Wendy, W., Zahrol, A. and Nadirah, M. (2009) Multiple antibiotic resistance and heavy metal resistance profile of bacteria isolated from giant freshwater prawn (Macrobrachium rosenbergii) hatchery. Agric. Sci. China, 8(6): 740-745. [Crossref]

5. Lee, S.W., Najiah, M., Wendy, W., Nadirah, M. and Faizah, S.H. (2009) Occurrence of heavy metals and antibiotic resistance in bacteria from organs of American bullfrog (Rana catesbeiana) cultured in Malaysia. J. Venom. Anim. Toxins Trop. Dis., 15(2): 353-358.

6. Xu, T. and Zhang, X.H. (2014) Edwardsiella tarda: An intriguing problem in aquaculture. Aquaculture, 431: 129-135. [Crossref]

7. Resende, J.A., Silva, V.L., Fontes, C.O., Souza-Filho, J.A., Oliveira, T.L.R., Coelho, C.M., Cesar, D.E. and Diniz, C.G. (2012) Multidrug-resistance and toxic metal tolerance of medically important bacteria isolated from an aquaculture system. Microbes Environ., 27(4): 449-455. [Crossref] [PMC]

8. Yu, Z., Gunn, L., Wall, P. and Fanning, S. (2017) Antimicrobial resistance and its association with tolerance to heavy metals in agriculture production. Food Microb., 64: 23-32. [Crossref] [PubMed]

9. Clinical and Laboratory Standards Institute. (2015) Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Fifth Informational Supplement. CLSI Document M100-S25. Clinical and Laboratory Standards Institute, Wayne, Pennsylvania, USA.

10. Allen, D.A., Austin, B. and Colwell, R.R. (1977) Antibiotic resistance patterns of metal-tolerant bacteria isolated from an estuary. Antimicrob. Agents Chemother., 12(4): 545-547. [Crossref]

11. Miranda, C.D. and Castillo, G. (1998) Resistance to antibiotic and heavy metals of motile aeromonads from Chilean freshwater. Sci. Total Environ., 224: 167-176. [Crossref]

12. Lee, S.W. and Wendy, W. (2012) Characterization of Vibrio alginolyticus isolated from white leg shrimp (Litopenaeus vannamei) with emphasis on its antiprogram and heavy metal resistance pattern. Vet. Arhiv., 82(2): 221-227.

13. Sudhesh, P.S., Al-Ghabshi, A., Al-Mazrooei, N. and Al-Habsi, S. (2012) Comparative pathogen omics of bacteria causing infectious diseases in fish. Int. J. Evol. Bio., 2012: Article ID: 457264, 16.

14. Bergh, O., Nilsen, F. and Samuelsen, O.B. (2001) Diseases, prophylaxis and treatment of the Atlantic halibut Hippoglossus hippoglossus: A review. Dis. Aquat. Org., 48: 57-74. [Crossref] [PubMed]

15. Katharios, P., Kokkari, C., Dourala, N. and Smyrli, M. (2015) First report of Edwardsiellosis in cage-cultured sharp snout sea bream, Diplodus puntazzo from the Mediterranean. BMC Vet. Res., 11: 155. [Crossref] [PubMed] [PMC]

16. Giraud, E., Douet, D.G., Le Bris, H., Bouju-Albert, A., Donnay-Moreno, C., Thorin, C. and Pouliquen, H. (2006) Survey of antibiotic resistance in an integrated marine aquaculture system under oxolinic acid treatment. FEMS Microbiol. Ecol., 55(3): 439-448. [Crossref] [PubMed]

17. Lai, H.T. and Lin, J.J. (2009) Degradation of oxolinic acid and flumequine in aquaculture pond waters and sediments. Chemosphere, 75(4): 462-468. [Crossref] [PubMed]

18. Phu, T.M., Phuong, N.T., Scippo, M.L. and Dalsgaard, A. (2015) Quality of antimicrobial products used in striped catfish (Pangasianodon hypophthalmus) aquaculture in Vietnam. PLoS One, 10(4): e0124267. [Crossref]

19. Phu, T.M., Scippo, M.L., Phuong, N.T., Tien, C.T.K., Son, C.H. and Dalsgaard, A. (2015) Withdrawal time for sulfamethoxazole and trimethoprim following treatment of striped catfish (Pangasianodon hypothalamus) and hybrid red tilapia (Oreochromis mossambicus x Oreochromis niloticus). Aquaculture, 437: 256-262. [Crossref]

20. Yazdankhah, S., Rudi, K. and Bernhoft, A. (2014) Zinc and copper in animal feed-development of resistance and co-resistance to antimicrobial agents in bacteria of animal origin. Microb. Ecol. Health Dis., 25: 25862.

21. Hassen, A., Saidi, N., Cherif, M. and Boudabous, A. (1998) Resistance of environmental bacteria to heavy metals. Biores. Technol., 64(1): 7-15. [Crossref]

22. Lima de Silva, AA., de Carvalho, M.A.R., de Souza, S.A.L., Dias, P.M.T., da Silva Filho, R.G., de Meirelles Saramago, C.S., de Melo Bento, C.A. and Hofer, E. (2012) Heavy metal tolerance (Cr, Ag and Hg) in bacteria isolated from sewage. Braz. J. Microb., 43(4): 1620-1631. [Crossref]