腹泻仔猪源致病性大肠杆菌生物膜与耐药性及毒力的相关性

Association of biofilm formation with drug-resistance and virulence of Escherichia coli isolated from diarrhea piglet

摘要:

【目的】探讨腹泻仔猪源致病性大肠杆菌生物膜形成能力及其与耐药性、毒力之间的相关性。【方法】收集临床分离鉴定的129株致病性大肠杆菌，采用96孔微量板法、K-B法、微量稀释法、寇氏改良法分别测定体外生物膜形成能力、耐药表型、生物膜菌与浮游菌的最小抑菌浓度(MIC)、对小鼠的半数致死量(LD50)。【结果】129株致病性大肠杆菌生物膜阳性率为96.1%，以弱阳性(1+)为主；分离株对四环素、氨苄青霉素、阿莫西林的耐药率分别为92.2%、92.2%、93%，对亚胺培南的耐药率最低为1.6%，共呈现94种多重耐药谱，其中以阿莫西林-氨苄青霉素-四环素-强力霉素-复方新诺明-甲氧苄啶构成比最大，为86.0%，且其与环丙沙星、氟苯尼考、左氧氟沙星、诺氧沙星、头孢拉定及头孢哌酮的耐药性有相关性(P<0.05)，环丙沙星和氟苯尼考对生物膜形成菌的MIC较对应浮游菌分别提高2?16倍和8?16倍；生物膜形成能力3+的菌株LD50最大。【结论】腹泻仔猪源致病性大肠杆菌普遍具有生物膜形成能力，呈现多重耐药，生物膜形成菌对环丙沙星及氟苯尼考的耐药性与生物膜形成能力呈正相关，但随着生物膜形成能力的增强，LD50值则相应增大。

Abstract:

[Objective] To study the association of biofilm formation ability with drug-resistance and virulence of Escherichia coli isolated from diarrhea piglets. [Methods] In total 129 strains of clinically isolated and identified pathogenic E. coli were collected. The in vitro biofilm formation, the drug-resistance phenotype, the minimal inhibitory concentration (MIC) of biofilm bacteria and planktonic, and the median lethal dose (LD50) in mice were then evaluated by the 96-well micro plate method, the K-B method, the micro dilution method, and the Curtiss modified method, respectively. [Results] The positive rate of biofilm formation was 96.1% among the 129 isolates with the majority of them to be lowly positive. The resistance rate to tetracycline, ampicillin and amoxicillin was 92.2%, 92.2%, and 93%, respectively. The lowest resistance rate to imipenem was 1.6%. Ninety-four multi resistant phenotypes were displayed in the isolates, with 86% of them to be amoxicillin-ampicillin-tetracycline-doxycycline-cotrimoxazole-trimethoprim, which was the most frequent type and was correlated to ciprofloxacin, florfenicol, levofloxacin, norfloxacin, cephradine and cefoperazone (p<0.05). The MIC of ciprofloxacin and florfenicol on biofilm bacteria was 2–16 and 8?16 times, respectively, higher than on planktonic bacteria. Isolates with biofilm formation 3+ showed the highest LD50. [Conclusion] Pathogenic E. coli in diarrhea piglets showed the biofilm formation ability and were multi-resistant. Drug resistance of bacteria with biofilm formation to ciprofloxacin and florfenicol was positively correlated to the biofilm formation ability, and LD50 also increased with a stronger biofilm formation ability.