Fluoroquinolone treatment of experimental Salmonella enterica serovar Typhimurium DT104 infections in chickens selects for both gyrA mutations and changes in efflux pump gene expression.
Fluoroquinolone treatment of experimental Salmonella enterica serovar Typhimurium DT104 infections in chickens selects for both gyrA mutations and changes in efflux pump gene expression.
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DOI：
10.1093/jac/dki189
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
L. Randall;D. Eaves;S. Cooles;V. Ricci;A. Buckley;M. Woodward;L. Piddock
中科院分区：
文献类型：
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作者：
L. Randall;D. Eaves;S. Cooles;V. Ricci;A. Buckley;M. Woodward;L. Piddock
目的观察恩诺沙星（拜特利）在鸡体内对三种不同耐药表型肠沙门氏菌的杀灭效果，并探讨产生的突变体的耐药机制。方法在两个单独的重复实验（I和II）中，3株肠沙门氏菌血清型鼠伤寒杆菌DT104[菌株A，完全抗生素敏感菌株；菌株B是A的等基因多重耐药（MAR）衍生物；菌株C（含GyrA ph -83的兽医五抗表型菌株）以约10(3)cfu/只的剂量接种于日龄雏鸡。在第10天，各组雏鸡（n =10）分别在其饮用水中添加50 ppm的恩诺沙星5天或单独饮水（对照组）。监测盲肠内容物是否存在沙门氏菌，将菌落复制到含有抗生素的培养基上或用环己烷覆盖，以确定敏感性降低的分离株的比例。对雏鸡分离株进行抗生素mic测定和环己烷耐受性测定。采用DHPLC检测拓扑异构酶基因突变，RT-PCR检测marA、soxS、acrB、acrD和acrF的表达。结果在实验1中，与未处理对照组相比，恩诺沙星显著降低了A菌株的数量。在实验II中，恩诺沙星显著降低了菌株b的数量，而在实验I中，恩诺沙星对菌株C的脱落没有影响。感染菌株A和B的禽类产生了对氟喹诺酮类药物敏感性降低的分离株。菌株A或菌株B的分离株需要>128 mg/L的钠二酸才能抑制，其中含有GyrA Asn-82或ph -83。被16 mg/L钠二酸抑制的分离株对其他化学类抗生素也不敏感，并变得耐环己烷（如MAR）。结论：推荐的恩诺沙星治疗雏鸡可迅速从全敏和MAR菌株中筛选出对氟喹诺酮类药物敏感性降低的菌株。它还可以选择MAR分离物。
OBJECTIVES To determine the efficacy of enrofloxacin (Baytril) in chickens in eradicating three different resistance phenotypes of Salmonella enterica and to examine the resistance mechanisms of resulting mutants. METHODS In two separate replicate experiments (I and II), three strains of Salmonella enterica serovar Typhimurium DT104 [strain A, fully antibiotic-sensitive strain; strain B, isogenic multiple antibiotic-resistant (MAR) derivative of A; strain C, veterinary penta-resistant phenotype strain containing GyrA Phe-83], were inoculated into day-old chicks at approximately 10(3) cfu/bird. At day 10, groups of chicks (n =10) were given either enrofloxacin at 50 ppm in their drinking water for 5 days or water alone (control). Caecal contents were monitored for presence of Salmonella and colonies were replica plated to media containing antibiotics or overlaid with cyclohexane to determine the proportion of isolates with reduced susceptibility. The MICs of antibiotics and cyclohexane tolerance were determined for selected isolates from the chicks. Mutations in topoisomerase genes were examined by DHPLC and expression of marA, soxS, acrB, acrD and acrF by RT-PCR. RESULTS In experiment I, but not II, enrofloxacin significantly reduced the numbers of strain A compared with the untreated control group. In experiment II, but not I, enrofloxacin significantly reduced the numbers of strain B. Shedding of strain C was unaffected by enrofloxacin treatment. Birds infected with strains A and B gave rise to isolates with decreased fluoroquinolone susceptibility. Isolates derived from strain A or B requiring >128 mg/L nalidixic acid for inhibition contained GyrA Asn-82 or Phe-83. Isolates inhibited by 16 mg/L nalidixic acid were also less susceptible to antibiotics of other chemical classes and became cyclohexane-tolerant (e.g. MAR). CONCLUSIONS These studies demonstrate that recommended enrofloxacin treatment of chicks rapidly selects for strains with reduced fluoroquinolone susceptibility from fully sensitive and MAR strains. It can also select for MAR isolates.