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Abstract：
Escherichia coli is a major bacterial pathogen which causes diarrhea in the giant panda. This study investigated the biological characteristics of 100 E. coli strains isolated from fecal samples collected from 100 captive giant pandas of different age groups and sexes. A standard Kirby-Bauer disk diffusion antimicrobial susceptibility test was performed with the isolates and we then further evaluated the antibiotic resistance genes (ARGs) by high-throughput quantitative PCR. Additionally, we then analyzed O serogroups through a slide agglutination test, virulence genes and the multi-locus sequence typing (MLST) by PCR. Antimicrobial susceptibility testing demonstrated that the 100 E. coli strains were mainly resistant to ENR (68%), AM (56%), IPM (55%), AMX (54%) and CA (52%), but were susceptible to MEM and FOX. The resistance to TZP, AK, FEP, CAZ, AMS, AZM, AT and IPM was significantly related to age (p < 0.05); the resistance rate of E. coli isolated from female giant pandas to N was significantly higher than in males (p < 0.05). Forty-five different types of ARGs were found, which included a total of 2,258 ARGs, in the 100 E. coli isolates. The top 10 of detection rate of ARGs were: acrA-04, acrA-05, aacC, blaCTX-M-04, ampC-04, blaSHV-01, blaTEM, sul2, blaOXY, tetA-02. ARGs aac (6\')I1, blaCTX-M-03, tetD-02, blaSHV-02 and blaOXY were significantly related to age (p < 0.05), blaSHV-02, blaNDM and ampC-04 were related to sex (p < 0.05). Twelve different O serogroups from 32 E. coli isolates were distinguished, including O4, O8, O9, O15, O18, O20, O55, O88, O112, O157, O158, and O167. The most prevalent O serotype was O20, but O28, O45, O101, O149, and O152 were not detected. Fourteen different types of virulence genes were detected in the 100 E. coli isolates, of which papA (99%) were highly detected, while hlyA, elt and estA were not detected. MLST showed that 41 STs, which had one CCs and six groups with SLVs, in the 100 E. coli strains were identified, the main type was ST37. Our results advocate the need of strict biosecurity and surveillance programs in order to prevent the spread of pathogenic bacteria in the captive giant panda population.
摘要：
大肠杆菌是引起大熊猫腹泻的主要细菌病原体。本研究调查了从100只不同年龄和性别的圈养大熊猫粪便样品中分离的100株大肠杆菌的生物学特性。对分离株进行了标准的Kirby-Bauer圆盘扩散抗微生物敏感性测试，然后我们通过高通量定量PCR进一步评估了抗生素抗性基因（ARG）。此外,然后我们通过载玻片凝集试验分析了血清群，毒力基因和通过PCR进行多位点序列分型(MLST)。药敏试验表明,100株大肠杆菌对ENR主要耐药(68%),AM（56%），IPM（55%），AMX（54%）和CA（52%），但对MEM和FOX敏感。对TZP的抵抗,AK,FEP,CAZ,AMS,AZM,AT和IPM与年龄显著相关(p<0.05);雌性大熊猫分离的大肠杆菌对N的耐药率显著高于雄性(p<0.05)。发现了45种不同类型的ARGs，其中包括总共2258个ARG，在100个大肠杆菌分离物中。ARGs检出率前10位依次为:acrA-04、acrA-05、aacC、blaCTX-M-04,ampC-04,blaSHV-01,blaTEM,sul2,blaOXY,tetA-02.ARGsaac(6')I1、blaCTX-M-03、tetD-02、blaSHV-02和blaOXY与年龄显著相关(p<0.05),blaSHV-02、blaNDM和ampC-04与性别有关(p<0.05)。区分了来自32个大肠杆菌分离株的12个不同的O血清群，包括O4、O8、O9、O15、O18、O20、O55、O88、O112、O157、O158和O167。最普遍的O血清型是O20，但未检测到O28，O45，O101，O149和O152。在100个大肠杆菌分离株中检测到14种不同类型的毒力基因，其中papA（99%）被高度检测，而hlyA,未检测到elt和estA。MLST显示41个STS，其中有一个CC和六个带有SLV的组，在鉴定出的100个大肠杆菌菌株中，主要类型为ST37。我们的结果主张需要严格的生物安全和监测计划，以防止病原菌在圈养大熊猫种群中的传播。
