哺乳豚および離乳豚における酸耐性大腸菌の保有状況

志村　仁^1）†　　　板垣光明^1）　　　庭野正人^1）　　　野呂明弘^1）
大井田　廣^1）　　　中澤宗生^2）

要　　　　　約 　哺乳豚および離乳豚における酸耐性大腸菌の保有状況を知る目的で，7農場から集めた20〜40日齢の哺乳豚および離乳豚の直腸便計70検体について調査した．総大腸菌数は10倍階段希釈法で定量し，酸耐性大腸菌数はpH 5，pH 4，pH 3およびpH 2のTSB培地における生存性から求めた．その結果，哺乳豚および離乳豚全体における総大腸菌数（平均値±標準偏差，log10/g）は7.09±1.63であり，pH 5，pH 4，pH 3およびpH 2での酸耐性大腸菌数は，7.24±1.80，7.06±1.75，5.76±2.37および3.19±2.68であった．酸耐性大腸菌数は離乳豚より哺乳豚，正常便より下痢便で高い傾向がみられた．しかし，哺乳豚でのpH 2耐性大腸菌数は正常便（4.15±2.45）と下痢便（3.35±2.31）とで大きな差が認められなかった．一方，離乳豚では正常便（1.51±2.25）より下痢便（4.64±2.45）の方が高い値を示した．さらに，離乳豚の下痢便から分離された溶血性酸耐性大腸菌は24株中23株がVT2遺伝子を保有していた． ――キーワード：酸耐性，大腸菌，哺乳豚，離乳豚． --------------------日獣会誌　54，909〜912（2001） Prevalence of Acid-resistant Escherichia coli in Neonatal and Weaning Piglets Hitoshi SHIMURA＊†, Mituaki ITAGAKI, Masato NIWANO, Akihiro NORO, Hiroshi OOIDA and Muneo NAKAZAWA ＊Gumma Chubu Livestock Hygiene Service Center, 315 Kaminagaiso-cho, Maebashi 371-2165, Japan SUMMARY   Studies to compare populations of acid-resistant Escherichia coli were conducted on 70 samples of rectal feces from neonatal and weaning piglets 20 to 40 days old from 7 farms. For determination of total E. coli, samples were diluted by a volume of 10 times. Acid-resistant E. coli was estimated by viability in TSB media at pH 5, pH 4, pH 3, and pH 2. Total E. coli count in neonatal and weaning piglets was 7.09±1.63 (mean±S.D.，log10/g). The pH 5-resistant E. coli count was 7.24±1.80; the pH 4 count was 7.06±1.75; the pH 3 count was 5.76±2.37; and the pH 2 count was 3.19±2.68. Acid-resistant E. coli counts were frequently higher in neonatal than in weaning piglets, and diarrheal feces generally contained more than normal feces. Although in neonatal piglets there was no significant difference in pH 2-resistant E. coli between diarrheal (3.35±2.31) and normal (4.15±2.45) feces, in weaning piglets the population was greater in diarrheal (4.64±2.45) than normal feces (1.51±2.25). Moreover, 23 of the 24 hemolytic acid-resistant strains isolated from the diarrheal feces of weaning piglets possessed the VT2 gene. ―Key words : acid-resistant, Escherichia coli, neonatal piglet, weaning piglet. †　Correspondence to : Hitoshi SHIMURA (Gumma Chubu Livestock Hygiene Service Center) 315 Kaminagaiso-cho, Maebashi 371-2165, Japan TEL 027-261-0314 --------------------　　　　　J. Jpn. Vet. Med. Assoc., 54, 909〜912 (2001)