| Currently, the antibiotics are still the first choice for the treatment and prevention of bacterial diseases in giant pandas gradually. With antibiotic usage, resistance of bacteria may be produced under the pressure to choose antibiotics; Colonization or infection by a resistant bacterial strain can occur as the result of consumption of antimicrobials. Bacterial resistance will make it difficult to cure giant pandas by antibiotics. So it is necessary to study antimicrobial resistance of E. coli giant panda origin. E.coli is always used as indicator strain for antimicrobial resistance that can be predicted by analysis of antimicrobial resistance of E.coli. Therefore, the objective of this study is to investigate the prevalence of antimicrobial resistance in E.coli giant panda origin.1. Isolation and serotypes identification of E.coli from giant pandas149 strains were isolated and identified from fecal samples, urogenital swabs and respiratory swabs of giant pandas in SiChuan. The serotypes were identified by the slide agglutination test. The results showed that 144 of 149 (96.64%) strains were type able.57 different O serotypes were identified. The superiority serotypes among 54 strains were O18, O60, O54, O130, O17, O99, O101 and O107, proportions of each were 6.71%,6.04%,4.7%,4.7%, 3.36%,3.36%,3.36% and 3.36%, respectively. There are a great variety of serotypes in same district. The distribution of serotypes is discrepancy among different districts and superiority serotypes. The distribution of serotypes is discrepancy among different age period as well.2. Antimicrobial susceptibility tests of E.coli isolates from giant pandasMICs of 18 antimicrobial agents were determined in 96 well cell culture clusters by broth dilution method according to the CLSI criteria 22.The results showed that the ranges of MICr of E.coli were wide and great difference. MIC50 was so low that it did not achieve resistant density, and MIC90 of most antimicrobial agents did not achieve resistant density too. The results also showed the level resistant rates of 18 antimicrobial agents in E.coli were low degree (the rate was 1.34%-23.49%).The most common resistance was to tetracycline, the resistant rate was 23.49%, followed by doxycycline and ampicillin, the resistant rates were 16.78% and 10.07%, respectively. The resistance rates of other antimicrobial agents were less than 10%, even non-resistant to amikacin. The rates of resistance were different in different regions.19 resistance patterns were obtained among resistant E.coli, the superiority pattern was TET/DOX. The rate of multidrug resistance was low, and the isolates were mainly resistant to 1 or 2 kinds of antimicrobial agent.3. Detection of resistance genes in E.coli isolates from giant pandas11 kinds of tetracycline resistance genes and 4 kinds of β-lactamase genes were detected. The results showed that tetA(22 strains) and tetB(15srains) were detected, tetC, tetD, tetG, tetK, tetL, tetM, tetS, tetO and tetW were not detected. The β-lactamase genes, TEM gene (13 strains) and CTX-M-28 gene (2 strains), were detected in E.coli, SHV and OXA resistance genes were not detected. Among 13 ampicillin resistance E.coli strains,12 of 13 carried TEM-1 and 1 of 13 carriedTEM-34. The mechanism of tetracycline resistance in E.coli was efflux encoded by tet A or tetB gene, the mainly mechanism of β-lactam antibiotics was producing TEM-1 lactamase.4. Conjugation experiments of R plasmidsConjugal transfer experiments were performed by the filter mating method using E.coli J53 AziR as recipient. The result showed that resistance plasmid can be transferred by horizontal transmission between different strains. The results also showed that transconjugants performed higher MICs that E.coli J53, expecially to tetracycline and P-lactam antibiotics.In conclusion, serotypes of E.coli isolates were widely distributed and 57 serotypes were obtained. Through the investigation of antimicrobial resistance and detection of resistance genes to 149 E.coli isolates from giant pandas, we found that E.coli exhibited low level resistant rates to 18 antimicrobial, and multidurg resistance was not widespread. tet A, tetB and TEM were most prevalence genes in E.coli. The results of conjugal transfer experiments demonstrated the horizontal transmission of resistance genes of E.coli isolates. |
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