[Isolation and serotyping of Vero toxin-producing Escherichia coli (VTEC) from pig]

As a part of basic studies to elucidate the source of infection of Verotoxin-producing Escherichia coli (VTEC) infectious disease, fresh feces were collected from pigs raised in Kanto District (A and B Prefectures) and Kyushu District (C and D Prefectures) between April and October in 2000, and isolation, serotyping, toxin typing, and drug sensitivity test of VTEC were performed. 1) Of 411 fecal samples tested, VTEC was isolated from 44 samples (10.7%), consisting of 12 of 112 samples (10.7%) from A Prefecture, nine of 100 samples (9.0%) from B Prefecture, 18 of 99 samples (18.2%) from C Prefecture, and five of 100 samples (5.0%) from D Prefecture. 2) Forty-five isolates were serotyped. Four isolates (8.9%) were typed as type 3, but the remaining 41 isolates (91.1%) could not be typed. The four typed isolates consisted of two O112ac:H- isolates and one each of O126:H- and O157:H7. 3) Toxin was typed in 45 isolates. Twenty-seven (60.0%) and 17 isolates (37.8%) produced VT 2 and VT1, respectively, and one isolate (2.2%) produced both VT1 and VT2. 4) Drug sensitivity tests of 45 isolates were performed. All 45 isolates (100%) were multidrug-resistant that were resistant to multiple drugs. Nineteen, nine, four, four, seven, one, and one isolates were resistant to five, six, two, three, four eight, and nine drugs, respectively. The above findings confirmed contamination in all districts, although the VTEC isolation rate varied among the sampling districts. Serotyping clarified the presence of O157:H7 and O112ac:H- that are detected in human VTEC infectious disease. The drug sensitivity tests clarified the presence of many multidrug-resistant strains.