Prevalence of Multiple Antibiotic Resistant Escherichia coli Serotypes in Cow Raw Milk Samples and Traditional Dairy Products in Osun State, Nigeria

Abstract

Aims: Isolation and characterization of multiple antibiotic resistant Escherichia coli serotypes in cow raw milk and traditional dairy products in Osun state, Nigeria was reported. Study Design: Experimental based study of raw milk of lactating cows, local cheese and yoghurt. Place and Duration of Study: Samples were collected at different markets in Ile-Ife, Modakeke, Edun-abon, and Akinlalu in Osun State, Nigeria, between June and August, 2011. Methodology: Samples of cow raw milk, cheese and yoghurt were enumerated bacteriologically on MacConkey agar at 37ºC for the total coliform. Isolation of E. coli was done on eosin methylene blue agar at 37ºC using pour plate technique. The isolate identity was further confirmed by biochemical tests and serotyping. Antibiotic susceptibility of the isolates was determined by the disk diffusion technique. Molecular typing of Escherichia coli was performed using polymerase chain reaction (PCR) technique. Result: The coliform count ranged from 1.0 to 6.00×105cfu/g in raw milk, 1.30 to 9.60×105cfu/g in cheese and 1.3 to 5.0×105cfu/g in yoghurt. The presence of E. coli was significantly low in cow raw milk compared to yoghurt and cheese (p< 0.05). Resistance to antibiotics varied among the E. coli isolates with the highest resistance to tetracycline (88.6%), cotrimoxazole (77.2%) and nitrofurantoin (6.81%). Most E. coli isolates were multiple antibiotic resistant types displaying 17 different multiple antibiotic resistance patterns. All the E. coli strains belonged to 9 serogroups (‘O’) and 17 serotypes (‘H’). The ‘O’ serogroups identified include O26 (2), O55 (4), O86 (3), O111 (11), O114 (1), O119 (1), O127 (5), O128 (1) and O142 (4) with 0111 (35.48%) being the most prevalent serotype. The flagellin (fliC) gene restriction analysis of E. coli serotypes showed that 72.7% were motile with 17 H-type while 27.3% were non-motile (O55 (1), O86 (1), O111 (5), O119 (2), O127 (2), O142 (1) ). The polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) patterns for the amplified fliC gene in the E. coli strains, produced bands of sizes ranging from 0.9 to 1.8 kb. Conclusion: The identification of E. coli O55:H27, O111:H8, O127:H42 and O142:H6 serotypes in the dairy products is of great public health concern.