Full Length Research Paper

Transfer of tetracycline resistance gene (tet^r) between replicons in some enteric bacteria of diarrhoeal origin from some hospitals in South-South, Nigeria

E.E. Akortha¹* and O. S. Egbule²

¹Department of Microbiology, Faculty of Life Science, University of Benin, Benin City, Nigeria.

²Department of Microbiology, Delta State University, Abraka, Delta State, Nigeria.

*Corresponding author. E-mail: eeakortha@yahoo.com. Tel: 08062342257.

Accepted 12 June, 2008

From April to June 2005, a total of 120 feacal samples were obtained from diarrheagenic patients (0-5 years) attending Baptist Medical Center, Eku (BMC), Central Hospital, Agbor (CHA) and University of Benin Teaching Hospital, Benin City (UBTH). These were screened for the presence of bacteria that could cause diarrhoea. The enteric organisms isolated included Escherichia coli, Klebsiella spp., Salmonella spp., Aeromonas spp., Shigella spp. and Shigella spp. Antimicrobial susceptibility testing among the isolates showed resistance to amoxicillin (92%), amoxicillin-clavulanic acid (84.4%), tetracycline (71.4%), gentamycin (43.5%), nalidixic acid (38.3%) and nitrofurantoin (7.9%).  E. coli showed the highest resistance to most of the antibiotics. Tetracycline resistance gene was detected in about 72% (110) of the total isolates, out of which 76 (69%) were subjected to curing experiment in the presence of 75 µg/ml acridine orange. Sixty (79%) of tetracycline resistant isolates lost their tetracycline resistance markers (tet^r) indicating that the tet^r gene was located on a plasmid. Attempt was made to transfer the tet^r gene from one replicon to the other within the same species and from one genus to the other. The rate of intra-species transfer of tet^r gene (67%) was significantly higher (< 0.05) than its rate of inter-generic transfer (24%).

Key words: Tetracycline resistance gene (tet^r), replicon, intra-species, inter-generic gene transfer.