【摘要】 【目的】调查中国6个省食品动物源耐甲氧西林金黄色葡萄球菌(livestock-associated methicillinresistant staphylococcus aureus,LA-MRSA)对大环内酯类-林可酰胺类-链阳菌素B类(macrolides, lincosamides and type B streptogramin, MLS_B)抗生素的耐药情况及MLS_B耐药基因的流行情况。【方法】从广东、河南、河北、福建、山东以及湖南等6省采集的食品动物源(猪、鸡以及鸭)样品约6 500份,分离金黄色葡萄球菌,通过苯唑西林药物敏感性测定和mecA,mecC基因检测鉴定MRSA菌株。采用二倍琼脂稀释法和微量肉汤稀释法测定LA-MRSA菌株对MLS_B以及其他常见的10种抗菌药物的敏感性,采用PCR方法检测MLS_B耐药基因(ermA-C和ereA-B)以及其他16种常见耐药基因。【结果】6 500份动物源样品中分离出480株金黄色葡萄球菌,其中101株为LA-MRSA,LA-MRSA分离率为1.54%(101/6500),金黄色葡萄萄球菌中LA-MRSA检出率达21.04%(101/480)。LA-MRSA菌株对MLS_B类抗生素呈现高度耐药的情况,耐药率高达99.00%以上,对其他常见的抗菌药物氟苯尼考、四环素、头孢噻肟以及庆大霉素等抗菌药物也均呈现高度耐药,耐药率为94.00%—99.00%。MLS_B耐药基因检测结果显示,ermC的检出率最高,为100.00%;其次是ereB,为79.20%,接着是ermA和ereA,检出率分别为45.54%和40.59%,而ermB的检出率最低,为11.88%。其他耐药基因的检测结果显示fexA、tetL、aadA1、aph(4’)-Ia的检出率较高,分别是92.10%、97.02%、97.29%和83.17%;其次是tet(M),检出率为71.29%;而aac(6’)-Ib、aac(3’)-Ic、aph(3’)-II、aph(3’)-IV、optrA、tet(A)、tet(C)的检出率相对较低,分别是49.50%、46.53%、39.60%、37.62%、33.67%、29.70%和20.79%;接着检出率更低的是cfr、tet(K)、lnuA以及lnuF,分别为17.82%、14.85%、5.94%和3.96%。进一步分析LA-MRSA菌株中MLS_B耐药基因检出个数与对受试抗菌药物的耐药数目之间的关系,发现随着动物源MRSA菌株对受试抗菌药物的耐药数目增加时,菌株中MLS_B耐药基因检出个数也在增加。【结论】动物源MRSA菌株对MLS_B高度耐药,其与菌株中ermC基因的高检出率一致,并且LA-MRSA菌株多重耐药情况严重,这与MLS_B耐药基因检出个数以及其他耐药基因的高检出率密切相关。因此,养殖场中MLS_B类药物使用应规范使用,以减少动物源MRSA菌株的多重耐药性。更多还原

【Abstract】 【Objective】 The aim of this study was to investigate the prevalence of genes encoding resistance to macrolides,lincosamides and streptogramins(MLS_B) among methicillin-resistant Staphylococcus aureus from food animals in China. 【Method】Staphylococcus aureus were isolated from about 6 500 samples of pig, chicken and duck origins among six different provinces,including Guangdong, Henan, Hebei, Fujian and so on, in China. LA-MRSA was confirmed from staphylococcus aureus through detecting the susceptibility of oxacillin and the presence of mecA and mecC genes. Susceptibility test of LA-MRSA resistant to MLS_B and other common antibiotics were determined by agar dilution method and microdilution broth method. And the MLS_B resistance genes(ermA-C and ereA-B) and other common resistant genes were detected by PCR. 【Result】Four hundred and eighty Staphylococcus aureus isolates and 101 LA-MRSA isolates were found among about 6 500 samples, and the isolation rate of Staphylococcus aureus and the detection rate of LA-MRSA among Staphylococcus aureus isolates were 1.54%(101/6500) and21.04%(101/480), respectively. Susceptibility test showed high resistance rate of LA-MRSA to MLS_B was found with over 99.00%among LA-MRSA isolates. High resistance rate to other common antibiotics was also found among LA-MRSA, including florfenicol,tetracycline, cefotaxime and gentamycin with the resistance rates of 99.01%, 96.39%, 96.39%, 96.39% and 94.05%, respectively.MLS_B resistance genes detection showed that ermC was found in all LA-MRSA isolates, followed by ereB(79.20%), ermA(45.54%)and ereA(40.59%), while, ermB was present with a low detection rate(11.88%). Other drug-resistant genes test results showed that fexA, tetL, aadA1, aph(4’)-Ia detection rate was higher, which was 92.10%, 97.02%, 97.29% and 83.17%, respectively; secondly,tet(M), the detection rate was 71.29%; the detection rate of aac(6’)-Ib, aac(3’)-Ic, aph(3’)-II, aph(3’)-IV, optrA, tet(A) and tet(C) was relatively low, which was 49.50%, 46.53%, 39.60%, 37.62%, 33.67%, 29.70% and 20.79%, respectively; the detection rate of cfr, tet(K), lnuA and lnuF was the lowest, which was 17.82%, 14.85%, 5.94% and 3.96%, respectively. The relationship of the number of MLS_B resistance genes and the number of resistance to antibiotics was further analyzed, which indicated the increased number of resistance to antibiotics was corresponding with the increased number of MLS_B resistance genes and high detection rate of other resistant genes among the LA-MRSA isolates. 【Conclusion】In conclusion, in this study, a high resistance to MLS_B was found and it was consistent to the high detection rate of ermC gene among LA-MRSA isolates. The multi-drug resistance of LA-MRSA isolates was serious and this was closely related to the number of MLS_B resistance genes. Therefore, it is urgently needed to take action in the rational use of antibiotics, as to reducing the emergence of multi-drug resistance LA-MRSA.更多还原