MONITORING OF Eschericia. coli O157 FROM RAW COW’S MILK IN THE STORAGE TANK IN SLEMAN DISTRICT, YOGYAKARTA

Abstract

Escherichia coli O157 is a member of Enterobacteriaceae which has somatic antigen O157. E. coli O157 is
associated with life threatening diseases such as hemorrhagic colitis (HC), hemolytic uremic syndrome
(HUS) and thrombotic thrombocytopenic purpura (TTP). Raw milk is considered a high risk food as it is
highly nutritious and serves as an ideal medium for bacterial growth. The aim of this study was to monitor
E. coli O157 contamination in the storage tank before distribution in Sleman district, Yogyakarta. Total
of 30 raw milk samples were collected from the storage tank in Sleman district. Tryptic Soy Broth (TSB)
media added with novobiocin was used as enrichment medium, while Chromocult Coliform Agar (CCA)
and Chromagar O157 medium for screening test. Additional analysis including serologic and molecular
test of isolates obtained. Based on the screening result, 11,428 colonies were considered as E. coli O157 suspect
that produced red colour in CCA medium. Further screening employing Chromagar O157 medium
resulted in 3 potential colonies which produce mauve colour. These colonies were later tested with Latex
Test O157 for serological reason, showing that none were E. coli O157. Molecular analysis with primer pairs
for detection of Stx1 and Stx2 genes confirm that none of the suspected strains have genes that encoded
the toxin, Stx1 and Stx2. These results showed that the presence of STEC (Shiga toxin E. coli) hasn’t found
in the tested samples of raw cow’s milk.
Keywords: E. coli O157, raw cow’s milk, storage tank, PCR