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No.26 (1979/12) >

Title :子豚糞便における薬剤耐性大腸菌の経時的消長(畜産学科)
Title alternative :Persistence of drug resistant fecal Escherichia coli in piglets (Department of Animal Husbandry)
Authors :金城, 俊夫
Authors alternative :Kinjo, Toshio
Issue Date :11-Dec-1979
Abstract :飼料安全法実施初年度において, 本法の薬剤耐性菌及びR因子保有(R^+)菌の出現に及ぼす影響を調べるため, 4腹の子豚40頭の糞便由来大腸菌を対象に経時的に調査した。便宜上, 子豚の出生当日から出荷される60日目までを6期(I期, 出生当日∿翌日;II期2∿5日;III期6∿10日;IV期11∿20日;V期 21∿35日;VI期36∿60日)に区分し, 各期より被検菌を分離し, 総計2,455株を得て6種の抗菌剤(APC, SM, TC, CP, KM, SA)に対する耐性試験とR^+菌の検索を行った。得られた成績は以下の通りである。1.耐性菌はI期の糞便からも46.4%と比較的高率に検出されたが, その主体はTCの単剤耐性菌であった。耐性菌の検出率はその後SA及びSM耐性菌の増加によりIV期の51.8%まで僅かに上昇している。しかしV期に至ってKM耐性菌の急激な出現及びSM, TC, SA耐性菌の増加によって, 耐性菌の検出率は86.1%に急上昇し, さらにこの傾向はVI期まで続いて, 60日令の段階では98.1%と殆んどの菌が耐性菌となった。2.各期をとおして全体では, 2,455株中1,568株, 63.9%が耐性菌で, 薬剤別ではTC耐性菌が46.6%で最も高く, 以下SA33.2%, SM29.2%, KM16.4%, APC3.3%, CP0.9%の順であった。3.耐性菌の検出率が生後日数の経過に伴って増加するのは, 多剤耐性化に起因する。即ちI期では単剤耐性菌が主であったのが, 漸次多剤耐性菌と代り, VI期では3剤或いは4剤以上に耐性の高次多剤耐性菌が主体を占めた。4.耐性菌1,568株中R^+菌は390株で, 24.9%に相当した。各期別の消長をみると, I期が3.6%と最も低く, その後漸次増加して, V期には最高の48.2%に達しているが, VI期には逆に38.5%とやゝ減少している。薬剤別にR^+菌の検出率をみると, 耐性菌の検出率の低くかったAPC, CPがそれぞれ64.2%, 31.8%と高く, 逆に耐性菌の検出率が最も高かったTCが11.5%と最低値を示した。5. 4頭の母豚の糞便由来大腸菌計256株についても, 耐性菌とR^+菌の検索を行ない, それぞれの子豚の成績と比較したが, 子豚糞便大腸菌の耐性化の原因をその母豚のそれに結びつけるだけの明確なデータは得られなかった。6.出荷時の子豚の成績から飼料安全法実施後も耐性菌及びR^+菌が高率に検出されており, 従って耐性菌等の出現を抑えるためには既に汚染された環境の清浄化等も同時に進める必要のあることを考察した。
Legislative control of the use of antimicrobial drugs in animal feeds in Japan became effective in January 1977. To confirm the effect of this control for incidences of drug resistant and R factors-carrying (R^+) E. coli strains, the present experiments were performed. A total of 2,455 E. coli strains isolated from rectal swabs from 40 piglets of 4 litters during first 60 days of their lives were tested for resistance to 6 antimicrobial drugs, i. e. APC, SM, TC, CP, KM, and SA. The experimental periods, for convenience, were divided into 6 stages as follows; stage I, 0 (the day of birth)-1 day after birth; stage II, 2-5 days; stage III, 6-10 days; stage IV, 11-20 days; stage V, 21-35 days and stage VI, 36-60 days. The results are summarized as follows : 1. A relatively high proportion (46.4%) of the strains of stage I was resistant to drugs, mainly to TC, and the proportion gradually increased until stage IV. At stage V, however, the percentage of resistant strains markedly increased up to 86.1% with sudden increase in those of KM resistant strains. This tendency continued until stage VI, when the percentage was 98.1. 2. Totally, of 2,455 strains, 1,568 (63.9%) were found to be resistant. The percentages of strains resistant to TC, SA, SM, KM, APC and CP were 46.6,33.2,29.2,16.4,3.3 and 0.9%, respectively. 3. Isolation frequencies of multiple resistant strains were increased with the lapse of days after birth of piglets from which the strains originated. At stage VI, 95.0% of strains tested were multiply resistance, of which patterns were mainly composed of SM, TC, KM and SA. 4. Of 1,568 resistant strains, 390 (24.9%) were found to carry R factors. The isolation frequencies of the R^+ strains among the reistant strains at stages I to VI were 3.6,6.0,8.4,27.2,48.2 and 38.5%, respectively. 5. Isolation frequencies of resistant and R^+ strains among 256 fecal E. coli strains isolated from 4 sows from which the piglets were derived were also tested and compared with those of piglets. No definite relations which may support a vertical contamination of resistant strains were obtained. 6. From the data obtained in the present experiments, it could be said that incidence of drug resistant strains was uncontrollable only by taking off the drugs from animal feeds. Therefore, clean up of already contaminated environments should be necessary.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/4172
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.26 p.395 -404
Appears in Collections:No.26 (1979/12)

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