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Research (Published online: 02-09-2014)

1. Detection of tetracycline resistance determinant tetA gene and antimicrobial resistance pattern in Escherichia coli isolates recovered from healthy layer chickens - A. Balasubramaniam, M. Arthanari Eswaran, P. Suresh and K. Sukumar

Veterinary World, 7(9): 635-638



   doi: 10.14202/vetworld.2014.635-638


A. Balasubramaniam: Department of Veterinary Microbiology, Veterinary College and Research Institute, Namakkal, Tamil Nadu, India;

M. Arthanari Eswaran: Department of Veterinary Microbiology, Veterinary College and Research Institute, Namakkal, Tamil Nadu, India;

P. Suresh: Department of Veterinary Microbiology, Veterinary College and Research Institute, Namakkal, Tamil Nadu, India;

K. Sukumar: Department of Veterinary Microbiology, Veterinary College and Research Institute, Namakkal, Tamil Nadu, India;


Received: 06-05-2014, Revised: 02-07-2014, Accepted: 12-07-2014, Published online: 02-09-2014


Corresponding author: A. Balasubramaniam, email:

Aim: The aim was to study the occurrence of tetracycline resistance determinant tetA gene, and antibacterial resistance pattern in commensal Escherichia coli recovered from healthy non-clinical layer chickens.

Materials and Methods: Twenty-four cloacal swabs were obtained from 15 flocks in five different layer farms located at around Namakkal, which is a place of high-intensity layer chicken rearing in south India. Identification of E. coli was carried out by performing cultural and biochemical tests. Antimicrobial resistance test was carried out using disc diffusion method. The polymerase chain reaction employing tetAC forward and tetAC reverse primers were carried out to detect tetA gene conferring resistance to tetracycline.

Result: All the collected cloacal swabs yielded E. coli. Twenty-one isolates (88%) were resistant to tetracycline antibiotic in disc diffusion method. All the isolates showed resistance to more than six antibiotics, which implied existence of multidrug resistant microbiota in intestine of poultry. Only seven (29%) isolates showed the presence of tetA gene indicating the involvement of either other one or more efflux gene(s), namely tetB, tetC and tetD or ribosomal protection encoded by tetM, tetO, tetQ and tetS genes than tetA gene.

Conclusion: Based on the presence of tetA gene among tetracycline-resistant bacteria in healthy non-clinical food-producing animals such as layer chickens, it can be significant in human medicine as tetA gene could easily be spread to other bacteria. This kind of phenomenon can be extrapolated in transfer of resistance for other antibacterial essential for treating bacterial infections in human. We conclude that preventing the spread of antimicrobial resistance through direct or indirect contact, consumed food/feed and through the environment is empirical in reduction of failures while treating bacterial infections.

Keywords: antibacterial resistance, Escherichia coli, tetA gene, tetracycline.

1. Wegener, H.G., Aarestrup, F.M., Gerner-Smidt, P. and Bager, F. (1999) Transfer of antibiotic resistant bacteria from animals to man. Acta. Vet. Scand. Suppl., 92: 51-57.
2. Roberts, M.C. (1996) Tetracycline resistance determinants: Mechanisms of action, regulation of expression, genetic mobility, and distribution. FEMS Microbiol. Rev., 19(1): 1-24.
3. Chopra, I. and Roberts, M. (2001) Tetracycline antibiotics: Mode of action, applications, molecular biology, and epidemiology of bacterial resistance. Microbiol. Mol. Biol. Rev., 65(2): 232-260.
PMid:11381101 PMCid:PMC99026
4. Arzese, A.R., Tomasetig L. and Botta, G.A. (2000) Detection of tetQ and ermF antibiotic resistance genes in Prevotella and Porphyromonas isolates from clinical specimens and resident microbiota of humans. J. Antimicrob. Chemother., 45(5): 577-582.
5. Blake, D.P., Humphry, R.W., Scott, K.P., Hillman, K., Fenlon, D.R. and Low, J.C. (2003) Influence of tetracycline exposure on tetracycline resistance and the carriage of tetracycline resistance genes within commensal Escherichia coli populations. J. Appl. Microbiol., 94(6): 1087-1097.
6. Marinho, C., Silva, N., Pombo, S., Santos, T., Montero, R., Gonçalves, A., Micael, J., Rodrigues, P., Costa, A.C., Igrejas, G., and Poeta, P. (2013) Echinoderms from Azores islands: An unexpected source of antibiotic resistant Enterococcus spp. and Escherichia coli isolates. Mar. Pollut. Bull., 69(1-2): 122-127.
7. Poirel L., Potron A., De La Cuesta C., Cleary T., Nordmann, P. and Munoz-Price L.S. (2012) Wild coastline birds as reservoirs of broad-spectrum-beta-lactamase-producing Enterobacteriaceae in Miami Beach, Florida. Antimicrob. Agents Chemother., 56(5): 2756-2758.
PMid:22314536 PMCid:PMC3346599
8. Kitadai, N., Obi, T., Yamashita, S., Murase, T. and Takase, K. (2012) Antimicrobial susceptibility of Escherichia coli isolated from feces of wild cranes migrating to Kagoshima, Japan. J. Vet. Med. Sci., 74(3): 395-397.
9. Barrow, G.A. and Faltham, R.K.A. (1993) Cowan and Steel's Manual for Identification of Medical Bacteria. 3rd ed. Cambridge University Press, London.
10. Bauer, A.W., Kirby, W.M.M., Sherris, J.C. and Turck, M. (1966). Antibiotic susceptibility testing by a standardized single disk method. Amer. J. Clin. Pathol., 45(4): 493-496.
11. Furushita, M., Shiba, T., Maeda, T., Yahata, M., Kaneoka, A., Takashi, Y., Torii, K., Hasegawa, T., and Ohita, M. (2003) Similarity of tetracycline resistance genes isolated from fish farm bacteria to those from clinical isolates. Appl. Environ. Microbiol., 69(9): 5336-5342.
PMid:12957921 PMCid:PMC194972
12. Rahman, M., Rahman, B.M. and Rahman, B. (2008) Antibiogram and plasmid profile analysis of isolated Escherichia coli from broiler and layer. Res. J. Microbiol., 3: 82-90.
13. Muhammad A.A., Hassan, S.M.R., Alam, S. and Shirin, M. (2009) Antibiotic resistance of Escherichia coli isolated from poultry and poultry environment of Bangladesh. American J. Environ. Sci., 5(1): 47-52.
14. Allan, B.J., Van-den-Hurk, W. and Potter, A.A. (1993) Characterization of Escherichia coli isolated from cases of avian colibacillosis. Can. J. Vet. Res., 57(3): 146-151.
PMid:8358674 PMCid:PMC1263615
15. Blanco, J.E., Blanco, M., Mora, A. and Blanco, J. (1997) Prevalence of bacterial resistance to quinolones and other antimicrobials among avian Escherichia coli strains isolated from septicemic and healthy chickens in Spain. J. Clin. Microbiol., 35(8): 2184-2185.
PMid:9230413 PMCid:PMC229934
16. Karczmarczyk, M., Walsh, C., Slowey R., Leonard N., and Fanning, S. (2011) Molecular characterization of multidrug-resistant Escherichia coli isolates from Irish cattle farms. Appl. Environ. Microbiol., 77(20): 7121-7.
PMid:21856840 PMCid:PMC3194884
17. Daini, O.A. and Adesemowo, A. (2008) Antimicrobial susceptibility pattern and R plasmids of clinical strains of Escherichia coli. Aus. J. Basic Appli. Sci., 2: 397-400.
18. Koo, H. and Woo, G. (2011) Distribution and transferability of tetracycline resistance determinants in Escherichia coli isolated from meat and meat products. Int. J Food Microbiol., 145(2-3): 407-413.
19. Santos, T., Silva, N., Igrejas, G., Rodrigues, P., Micael, J., Rodrigues, T., Resendes, R., Gonçalves, A., Marinho, C., Gonçalves, D., Cunha, R. and Poeta, P. (2013) Dissemination of antibiotic resistant Enterococcus spp. and Escherichia coli from wild birds of Azores Archipelago. Anaerobe., 24: 25-31.