Improved Sorbitol MacConkey Agar Medium Containing Cefixime and Potassium Tellurite for Isolation and Diagnosis of E. coli O157:H7 from clinical case

Subject Areas : Diagnostic Microbiology

Yahya Tahamtan ¹ , Masomeh Hayati ² , Mohammad Mehdi Namavari ³ , Gholam Reza Moazeni ⁴

1 - Department of Bacteriology vaccine and serum research institute of Razi, Shiraz, Iran
2 - Department of Bacteriology vaccine and serum research institute of Razi, Shiraz, Iran
3 - Department of Bacteriology vaccine and serum research institute of Razi, Shiraz, Iran
4 - Department of Bacteriology vaccine and serum research institute of Razi, Shiraz, Iran

Received: 2009-04-14 Accepted : 2009-05-15 Published : 2009-04-01

Keywords: E. coli O157, CT-SMAC, Ceffexime, Potassium tellurite,

Abstract :

Introduction and Objectives: E. coli O157:H7 form colorless colonies on SMAC and may be distinguished from intestinal flora. Some Enterobacteriaceae present in gut, also grow on SMAC and made difficulty to differentiation and diagnosis. Therefore modification and improvement of SMAC medium is necessary to select E. Coli O157. The aim of this study is improvement this medium in order to better differentiation of this bacterium. Material and Methods: 250 fecal swab sheep slaughtered in slaughterhouses Shiraz to isolate the bacteria E. coli O157 was selected. Prepared SMAC plates containing from 0.05 mg L-1 ceffexime and 2.5 mg L-1 potasium tellurite as standard (1S) to 6 time standard (6S). Certain pure E. coli O157 EDL933 was plated on SMACs.All plates incubated in 37°C over night. Results: E. coli O157 was growth on all six SMACs, but all plates had grown with the same count in 1S to 3S plats. Some bacteria decreased according to dose of antibiotics. Two  and four percent contamination rate was shown high sensitivity in 3 S than 1 S. use of media with high antibiotic deleted extra intestinal bacteria. Conclusion: We   recommend using ICT-SMAC medium supplemented with 1.5 and 7.5 mg L-1 ceffexime and potassium tellurte respectively in spite of current SMAC to isolate E. coli O157 from clinical case.