하리자돈으로부터 분리한 대장균에 관하여

Studies on Escherichia coli isolated from piglets with diarrhea

Ninty strains of Escherichia coli isolated from 40 piglets with diarrhea by rectal swab were tested for the resistance to 11 antimicrobial drugs and distribution of transferable R plasmid. In addition, the ability of E. coli isolates to agglutinate erythrocytes of sheep, chicken and guinea pig, to produce colicin or heat labile toxin (LT) and their co-transfer with R plasmid were tested. Of total 90 strains, 88 (97.8%) were resistant to tetracycline (Tc), 78 (86.7%) to streptomycin (Sm), 56 (62.2%) to sulfadimethoxine (Su), 36 (40.0%) to ampicillin(Am), 35 (38.9%) to chloramphenicol(Cm), 33(36.7%) to spectinomycin(Sp), 31(34.4%) to kanamycin(Km), 13(14.4%) to gentamicin(Gm), 2(2.2%)) to colistin (Cl), and 1 (l.1%) to rifampicin(Rf). The minimum inhibitory concentration ranges of 90 E. coli isolates were shown as 3.1-400㎍/ml to Tc, 6.3-＞1,600㎍/ml to Sm and Km, 50-＞1,600㎍/ml to Su, 3.1-＞1,600㎍/ml to Am, 3.1-800㎍/ml to Cm, 12.5-＞1,600㎍/ml to Sp, 1.6-＞1,600㎍/ml to Gm, 0.8-200㎍/ml to Cl, 6.3-50㎍/ml to Rf, and 3.1-25㎍/ml to Na. 50% MICs of E. coli isolates were shown as 0.8㎍/ml to Cl, 3.1㎍/ml to Gm and Na, 6.3㎍/ml to Am, 12.5㎍/ml to Cm, Km and Rf, 200㎍/ml to Tc and Sm, and＞1,600㎍/ml to Su. 90% MICs of E. coli isolates were shown as 0.8㎍/ml to C, 6.3㎍/ml to Na, 25㎍/ml to Rf, 50㎍/ml to Gm, 200㎍/ml to Tc, 800㎍/ml to Cm and Sp, 1,600㎍/ml to Sm and Am, and ＞ 1,600㎍/ml to Su and Km. There were no significant differences between 50% MIC for. Tc, Su and Cl. Eighty eight strans (97.8%) of 90 E. coli isolates were resistant to one or more drugs tested. The most common resistance pattern was Tc and Sm resistance, and followed by Tc, Sm, Su, Am, Cm and Sp resistance. Of 90 E, coli isolates, 12 strains(13.3%) produced colicin and conjugative R plasmid were detected in 7 strains (56.7%),which had no conjugative Col plasmid. Only one strains of 34 strains tested produced heat labile toxin, but the strain had no conjugative R plasmid. Mannose-resistant strains of all isolates were 2 strains to sheep erythrocytes, 3 to chicken erythrocytes and 4 to guinea pig erythrocytes, and R-positive transconjugants of these strains were able to agglutinate erythrocytes.