Iranian Journal of Clinical Infectious Disease 2011;6(1):24-30 Iranian Journal of Clinical Infectious Diseases 2011;6(1):24-30 ©2011 IDTMRC, Infectious Diseases and Tropical Medicine Research Center Tetracycline efflux pump indifferent Salmonella enterica isolated from diarrhea patients in two rural health centers in Western Kenya Onyango David Miruka 1* , Kakai Rose 2 , Waindi Eliud Nyandago 1 1 Department of Zoology, Maseno University, Maseno, Kenya 2 School of Public Health and Community Development, Maseno University, Maseno, Kenya ABSTRACT Background: Tetracyclines (TCs) are a type of broad-spectrum bacteriostatic antibiotics used for treatment of a wide variety of infections. These antibiotics eventually reach terrestrial and aquatic environments via application of manure or slurry to areas used agriculturally, or by other methods. Bacteria resistance to tetracycline is due to efflux pump among others. This study discerned the existence of tetracycline efflux pump in Salmonella enterica belonging to different serovars isolated from diarrhea patients in two rural health centers in Western Kenya. Patients and method: Forty-five unrelated tetracycline-resistant Salmonella isolates from diarrheal patients were cultured and phenotypically identified using conventional methods. Phenotypic tetracycline resistance profile was determined by using Agar Disc Dilution. Tetracycline growth curve for resistant isolates were determined by incubating 10 6 cfu in 10 ml nutrient broth having 30μg/ml tetracycline and incubated at 37°C in a rotary incubator. Generation rate was spectrophotometrically assayed at 600nm. Tetracycline resistant isolates DNA were extracted using QIAMP Qiagen protocol and amplified using specific tetracycline primers. Results: Tetracycline resistance genes were isolated in 62.2% (n=28/45) Salmonella isolates. Out of these, 64.3% (n =18/28) were S. typhi, 17.8% (n =5/28) S. typhimurium, and 14.3% (n=4/28) S. enteritidis. S. typhi expressed resistance to tetA 3.6% (n=1/28), tetB 10.7% (n=3/28), tetD 10.7% (n=3/28), tetG 10.7% (n=3/28), tetE, H, J, 10.7% (n=3/28) and tet AC 17.8% (n=5/28) in isolation or in combination. All the 5 S. typhimurium expressed tetA resistance. Totally, S. enteritidis displayed tetA, tetB and tetC resistance in 7.1%, 3.6%, and 3.6%, respectively. Conclusion: These data show that the identified gene encoded tet resistance gene as MFS–type multi-substrate efflux transporter, which contributes to intrinsic resistance on range of structurally unrelated compounds in Salmonella species. Keywords: Colony forming unit (cfu); Tetracycline; Resistance; Efflux pump. (Iranian Journal of Clinical Infectious Diseases 2011;6(1):24-30). INTRODUCTION 1 Although tetracyclines are the second most commonly used antibiotics worldwide, their efficacy has been curtailed by the high frequency of antimicrobial resistance (1). Tetracycline Received: 29 May 2010 Accepted: 12 December 2010 Reprint or Correspondence: Onyango David Miruka, MD. Department of Zoology, Maseno University, Box 333, Maseno, 40105, Kenya. E-mail: dvdonyango7@gmail.com resistance genes are usually mobile plasmid or transposons encoded and thus resistance arise due to acquisition of new genes from external sources (2). Resistance is primarily due to either energy- dependent efflux of tetracycline or protection of the ribosomes from the action of tetracycline. Efflux as a means of antibiotic resistance is most commonly associated with tetracyclines (e.g. tetA, tetB, tetK pumps) (3). In clinical settings, exposure ORIGINAL ARTICLE