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No.50 (2003/12) >

 
Title :ホルスタイン種親子の直腸便由来大腸菌における薬剤耐性
Title alternative :Antibiotic resistance in Escherichia coli isolates from rectal swab of Holstein cows and calves
Authors :岩崎, 健
鮫島, 好美
下門, 奈月
日越, 博信
Authors alternative :Iwasaki, Ken
Samejima, Yoshimi
Shimojoh, Natsumi
Higoshi, Hironobu
Issue Date :1-Dec-2003
Abstract :今回、2組のホルスタイン種親牛(A親牛およびB親牛)の分娩後1日目と7日目と、各子牛(A子牛およびB子牛)の出生後1日目から7日目までに分離した直腸便由来大腸菌252株(A子牛102株、B子牛90株、A親牛30株、B親牛30株)について、ABPC、CP、CTC、KM、SM、NA、およびSAの7薬剤に対する感受性試験を行い、耐性菌については伝達性Rプラスミドの保有状況を調査した。1)供試菌株の69%(173/252株)が薬剤耐性を示した。個体別による耐性菌検出率の平均は、A親牛20%に対してA子牛で61%、一方B親牛80%に対してB子牛90%と、いずれも親牛より子牛で高率に耐性菌が検出された。生後1日目の子牛では、A子牛47%、B子牛93%とすでに高率に耐性が認められ、生後4日目以降に耐性菌検出率がさらに増加した。2)薬剤耐性菌を薬剤別でみてみると、A親牛は4薬剤(ABPC、CTC、SM、およびSA)、B親牛は5薬剤(CP、CTC、SM、NA、およびSA)でのみ耐性菌が検出された。各子牛ではすでに1日目で親牛と同じ薬剤に耐性を示し、産後日数の経過とともに親牛では認められなかった薬剤にも耐性を示した。A子牛では2日目で他の3薬剤(CP、KM、およびNA)に、B子牛では5日目で他の1薬剤(ABPC)に耐性を示す一方、KMへの耐性は生後7日目まで認められなかった。3)薬剤耐性型をみると、A親牛で3剤型だけの2種類、B親牛で単剤型から4剤型までの5種類に対して、A子牛で単剤型から7剤型まで12種類、B子牛で単剤型から5剤型までの12種類と、子牛の薬剤耐性型が親牛よりも明らかに多かった。両子牛とも1日目で各親牛とは異なる耐性型が認められ、生後1日目から3日目までは単剤型が、4日目以降になると多剤耐性型が優勢となった。4)76株の薬剤耐性菌(A親牛6株、A子牛28株、B親牛11株、B子牛31株)について、伝達性Rプラスミドの保有状況を調査した。伝達性Rプラスミド保有菌はいずれも子牛のみから検出され、A子牛では4日目に単剤(ABPC)伝達性1株と3剤(ABPC-CP-CTC)伝達性1株、6日目に単剤(ABPC)伝達性1株が認められた。B子牛では3日目に2剤(CTC-SA)耐性型の1株だけが認められた。本調査を遂行するにあたり、御協力を頂いた沖縄県畜産試験場の各位に深謝いたします。
A total of 252 Escherichia coli isolates were recovered from rectal swabs of two Holstein cows (designated cow A and B) on postpartum days 1 and 7 and the female calf of each (designated calf A and B, respectively) on postnatal days 1-7. Each isolate was tested for susceptibility to 7 antibiotics [ampicillin (ABPC), chloramphenicol (CP), chlortetracycline (CTC), kanamycin (KM), streptomycin (SM), nalidixic acid (NA), and sulfadimethoxine (SA)] and for prevalence of conjugative R-plasmids. The results of these studies are: 1. Resistance to at least one of antibiotics tested was found in 69% (173/252) of the E. coli isolates. The mean frequency of resistant isolates was: cow A, 20%; calf A, 61%; cow B, 80%; and calf B, 90%. These results show that calves are readily infected with resistant bacteria: on postnatal day 1, 47% of the E. coli isolates from calf A and 93% from calf B were antibiotic-resistant. Furthermore, the fraction of isolates that were antibiotic-resistant increased after postnatal day 3. 2. On postpartum day 7, isolates with resistance to only 4 of the antibiotics tested (ABPC, CTC, SM, and SA) were obtained from cow A and to only to 5 of the antibiotics (CP, CTC, SM, NA, and SA) from cow B. On postnatal day 1, both calves already had isolates with the same-antibiotic resistances as the corresponding cow. By postnatal day 2, isolates from calf A were also resistant to the other 3 antibiotics (CP, KM, and NA). Isolates resistant to one of the other antibiotics (ABPC) were found in calf B by postnatal day 5, but no isolate to the remaining antibiotic (KM) was found in calf B by postnatal day 7. 3. A number of antibiotic resistance patterns were found, ranging from isolates resistant to a single antibiotic to isolates resistant to multiple (i. e., 2-7) antibiotics. Isolates from calves had more resistance patterns than those from cows, and no isolates from cows were resistant to more than 4 antibiotics. On postnatal day 1, isolates from both calves already had different resistance patterns than those from the corresponding cow. Isolates with resistance to a single antibiotic were predominant during postnatal day 1-3. However, after postnatal day 3, isolates with resistance to multiple antibiotics were predominant. 4. The prevalence of a conjugative R-plasmid was investigated in 76 of the antibiotic-resistant isolates; 6 from cow A, 28 from calf A, 11 from cow B, and 31 from calf B. Conjugative R plasmid transfer was found in 4 of these isolates: a day 4 postnatal isolate from calf A with resistance to 1 antibiotic (ABPC), a day 6 postnatal isolate from calf A with resistance to 1 antibiotic (ABPC), a day 4 postnatal isolate from calf A with resistance to 3 antibiotics (ABPC-CP-CTC), and a day 3 postnatal isolate from calf B with resistance to 2 antibiotics (CTC-SA).
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/3595
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.50 p.53 -59
Appears in Collections:No.50 (2003/12)

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