Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore.
J Glob Antimicrob Resist. 2020 Sep;22:613-619. doi: 10.1016/j.jgar.2020.06.004. Epub 2020 Jun 12.
Zinc oxide is used to prevent post-weaning diarrhoea in pigs as an alternative to antimicrobial growth promoters. This study aims to determine if the use of zinc oxide selects for extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and affects the expression of bla in E. coli.
Using an in vitro faecal micro-cosmos model, the selective properties of zinc were investigated using an E. coli strain with bla encoded by a natural IncI1 resistance plasmid (MG1655/pTF2) and another strain where the same gene was located on the chromosome (MG1655::bla). The micro-cosmos was seeded with faecal material containing an increasing concentration of zinc (0-8 mM). Outcome measurements consisted of colony-forming units (CFU) of the inoculated ESBL E. coli and naturally occurring coliforms as determined by plate counting on MacConkey with and without 5 mg/L cefotaxime as well as total viable bacteria determined on Luria agar without cefotaxime. Expression of bla under the experimental zinc concentrations was determined by quantitative polymerase chain reaction.
The proportion of MG1655/pTF2 of the total viable bacteria was significantly higher at high zinc concentrations (6 and 8 mM) compared with low concentrations (0-4 mM). The messenger RNA (mRNA) levels of bla in the two ESBL strains increased at increasing zinc concentrations and varied with the growth phase.
The growth of the inoculated CTX-M-1-encoding E. coli MG1655 strains and naturally occurring coliforms was impacted differently when exposed to zinc oxide. The bla mRNA expression levels seemed to increase with increasing zinc concentrations, but varied with growth phase, but not gene location.
氧化锌被用作替代抗菌生长促进剂来预防断奶后腹泻。本研究旨在确定氧化锌的使用是否选择产生超广谱β-内酰胺酶（ESBL）的大肠杆菌，并影响大肠杆菌中 bla 的表达。
使用体外粪便微生物群模型，使用带有 bla 的大肠杆菌菌株（MG1655/pTF2）和另一种 bla 位于染色体上的菌株（MG1655::bla）来研究锌的选择性特性。微生物群用含有递增浓度锌（0-8 mM）的粪便材料接种。结果测量包括接种的 ESBL 大肠杆菌和自然发生的大肠菌群的菌落形成单位（CFU），通过在含有和不含有 5mg/L 头孢噻肟的 MacConkey 平板上计数确定，以及在不含头孢噻肟的 Luria 琼脂上确定总活菌数。通过定量聚合酶链反应确定 bla 在实验锌浓度下的表达。
在高锌浓度（6 和 8mM）下，MG1655/pTF2 在总活菌中的比例明显高于低浓度（0-4mM）。两种 ESBL 菌株的 bla 信使 RNA（mRNA）水平随着锌浓度的增加而增加，并随生长阶段而变化。
当暴露于氧化锌时，接种的 CTX-M-1 编码大肠杆菌 MG1655 菌株和自然发生的大肠菌群的生长受到不同的影响。bla mRNA 表达水平似乎随着锌浓度的增加而增加，但随生长阶段而变化，而与基因位置无关。
