Division of Microbiology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079, USA.
Antibiotics (Basel). 2013 Dec 2;2(4):485-99. doi: 10.3390/antibiotics2040485.
There is much debate on whether continuous exposure of commensal bacteria and potential pathogens residing in the human intestinal tract to low levels of antimicrobial agents from treated food animals pose a public health concern. To investigate antimicrobial effects on bacteria under colonic conditions, we studied resistance development in Salmonella enterica and Listeria monocytogenes exposed to enrofloxacin in the presence of fecal extract. The bacteria were incubated at 37 °C in Mueller-Hinton broth, with and without 0.01~0.5 μg/mL enrofloxacin, in the presence and absence of sucrose, and with 1% or 2.5% filter-sterilized fecal extract, for three passages. In the second and third passages, only the bacteria incubated in the media containing sterilized fecal extract grew in 0.5 μg/mL of enrofloxacin. Fecal extract (1% and 2.5%) decreased the sensitivity of S. enterica to enrofloxacin in the medium containing the efflux pump inhibitors reserpine and carbonyl cyanide-m-chlorophenylhydrazone (CCCP) and affected the accumulation of ethidium bromide (EtBr) in this bacterium. Enrofloxacin (0.06 µg/mL) and fecal extract altered the composition of fatty acids in S. enterica and L. monocytogenes. We conclude that fecal extract decreased the susceptibilities of S. enterica and L. monocytogenes to concentrations of enrofloxacin higher than the MIC and resulted in rapid resistance selection.
关于食用动物经治疗后，其肠道内共生菌和潜在病原体持续暴露于低浓度抗菌药物是否会对公共健康构成威胁，目前存在广泛争议。为了研究抗菌药物对结肠条件下细菌的影响，我们研究了在粪便提取物存在的情况下，恩诺沙星对食源性沙门氏菌和单核细胞增生李斯特菌的耐药性发展。将细菌在 37°C 下于 Mueller-Hinton 肉汤中孵育，有或无 0.01~0.5μg/mL 的恩诺沙星，有无蔗糖，有无 1%或 2.5%过滤的粪便提取物，孵育 3 个传代。在第 2 和第 3 个传代中，只有在含有无菌粪便提取物的培养基中孵育的细菌在 0.5μg/mL 的恩诺沙星中生长。粪便提取物（1%和 2.5%）降低了含外排泵抑制剂利血平和羰基氰化物 m-氯苯腙（CCCP）的培养基中沙门氏菌对恩诺沙星的敏感性，并影响了该细菌中溴化乙锭（EtBr）的积累。恩诺沙星（0.06μg/mL）和粪便提取物改变了沙门氏菌和单核细胞增生李斯特菌中脂肪酸的组成。我们得出结论，粪便提取物降低了沙门氏菌和单核细胞增生李斯特菌对高于 MIC 的恩诺沙星浓度的敏感性，并导致快速耐药性选择。
