Detection and prevalence of shiga (vero) toxin producing E-coli 0157 in different age groups of dairy cattle from the Batangas Dairy Cooperative (BADACO) by Ma. Clarissa Angela S. Nuestro

Thesis (Doctor of Veterinary Medicine) Cavite State University

Includes bibliographical references.

College of Veterinary Medicine and Biomedical Sciences (VETMET)

NUESTRO, MA. CLARISSA ANGELA S., Cavite State University, Indang, Cavite. April 2005. Detection and Prevalence of Shiga (Vero) Toxin-Producing Escherichia coli 0157 in Different Age Groups of Dairy Cattle (Bos Taurus) from the Batangas Dairy Cooperative (BADACO). Adviser: Ma. Cynthia N. Rundina, DVM, MS.
This study was conducted primarily to detect and establish the prevalence of Shiga (Vero) toxin-producing Escherichia coli 0157 from the rectal fecal samples of 125 apparently healthy dairy cattle (Bos taurus) belonging to different age groups. Specifically, it aimed to isolate Shiga (Vero) toxin-producing E. coli 0157 by direct culture and characterize the isolates morphologically, biochemically and serologically. Finally, Shiga (Vero) toxin detection was done by the use of the Polymerase Chain Reaction (PCR) using slt-II primer. The rectal fecal samples were all subjected to direct culture onto Cefixime Tellurite-Sorbitol MacConkey Agar (CT-SMAC). In this medium a total of 61 (48.8%) non-sorbitol fermenting colonies, which was considered as presumptive Enterohemorrhagic Escherichia coli (EHEC) were isolated: 21 (34.4%) from calves, 15 (24.6%) in yearlings, 16 (26.2%) from heifers and 9 (14.8%) from cows. The 61 presumptive EHEC isolates were then tested for cytochrome oxidase activity and only 23 (37.7%) produced negative results. These were further characterized morphologically and biochemically and all were found to be gram negative and rod-shaped organisms. Biochemically, the isolates produced the following typical reactions: Acid slant/Acid butt with gas production (A/A gas) in the Triple Sugar Iron (TSI) agar, Voges Proskauer test negative (-), Urease negative (-), Citrate negative (-), no hydrogen sulfide produced and motile in Sulfide Indole Motility (SIM) medium, Indole positive (+) and Methyl Red positive (+) and Lysine Decarboxylase positive (+). The highest number of presumptive EHEC isolates was obtained from the age group of calves, having 10 (43.4%) while the least number of isolates was obtained from heifers, having 3 (13%) isolates. Three out of 23 (13%) of the presumptive EHEC did not ferment sorbitol in the sorbitol utilization test. These isolates were considered as presumptive Enterohemorrhagic Escherichia coli and were subjected to agglutination with 0157 antiserum. None of the samples agglutinated with the 0157 antiserum. Further test using the Polymerase Chain Reaction (PCR) of the BIOTECH 12 and BIOTECH 13 primers for E. coli 0157 also showed that none of the samples amplified the primers. Polymerase Chain Reaction using slt-II primer on the other hand, yielded 2 isolates which did not amplify the primer whereas, 1 isolate amplified the primer. These results showed that none of the isolates were E. coli 0157:H7 although one sample probably possessed the slt-II gene. This study showed that the EHEC strain E. coli 0157:H7 may not be present in the dairy cattle sampled in this study. However, these results could indicate that other EHEC strains may be present and as such similar studies on equally important EHEC strains are warranted. Moreover, based on the results of the PCR, non-E. coli 0157:H7 isolates are also capable of producing Shiga (Vero) toxins. Therefore, similar precautionary measures on handling of cattle as well as produce from these animals are
also necessary.

Submitted to the University Library 07/18/2007 T-2974