Tuckfield R Cary, McArthur J Vaun
Savannah River National Laboratory, Washington Savannah River Co., Bldg. 773-42A, Aiken, SC 29808, USA.
Microb Ecol. 2008 May;55(4):595-607. doi: 10.1007/s00248-007-9303-5.
The spatial pattern of antibiotic resistance in culturable sediment bacteria from four freshwater streams was examined. Previous research suggests that the prevalence of antibiotic resistance may increase in populations via indirect or coselection from heavy metal contamination. Sample bacteria from each stream were grown in media containing one of four antibiotics-tetracycline, chloramphenicol, kanamycin, and streptomycin-at concentrations greater than the minimum inhibitory concentration, plus a control. Bacteria showed high susceptibilities to the former two antibiotics. We summarized the latter two more prevalent (aminoglycoside) resistance responses and ten metals concentrations per sediment sample, by Principal Components Analysis. Respectively, 63 and 58% of the variability was explained in the first principal component of each variable set. We used these multivariate summary metrics [i.e., first principal component (PC) scores] as input measures for exploring the spatial correlation between antibiotic resistance and metal concentration for each stream sampled. Results show a significant and negative correlation between metals PC scores versus aminoglycoside resistance scores and suggest that selection for metal tolerance among sediment bacteria may influence selection for antibiotic resistance differently in sediments than in the water column. Our most important finding comes from geostatistical cross-variogram analysis, which shows that increasing metal concentration scores are spatially associated with decreasing aminoglycoside resistance scores--a negative correlation, but holds for contaminated streams only. We suspect our field results are influenced by metal bioavailability in the sediments and by a contaminant promoted interaction or "cocktail effect" from complex combinations of pollution mediated selection agents.
研究了来自四条淡水溪流的可培养沉积物细菌中抗生素抗性的空间格局。先前的研究表明，抗生素抗性的流行率可能会通过重金属污染的间接或共选择作用在种群中增加。从每条溪流中采集的样本细菌在含有四种抗生素（四环素、氯霉素、卡那霉素和链霉素）之一的培养基中培养，浓度高于最低抑菌浓度，外加一个对照。细菌对前两种抗生素表现出高敏感性。我们通过主成分分析总结了后两种更普遍的（氨基糖苷类）抗性反应以及每个沉积物样本中的十种金属浓度。在每个变量集的第一主成分中，分别解释了63%和58%的变异性。我们将这些多变量汇总指标[即第一主成分（PC）得分]用作输入量度，以探索每个采样溪流中抗生素抗性与金属浓度之间的空间相关性。结果表明，金属PC得分与氨基糖苷类抗性得分之间存在显著的负相关，并表明沉积物细菌中对金属耐受性的选择可能对沉积物中抗生素抗性的选择产生与水柱中不同的影响。我们最重要的发现来自地质统计学交叉变异函数分析，该分析表明，金属浓度得分的增加在空间上与氨基糖苷类抗性得分的降低相关——呈负相关，但仅适用于受污染的溪流。我们怀疑我们的实地结果受到沉积物中金属生物有效性以及污染介导的选择剂复杂组合产生的污染物促进相互作用或“鸡尾酒效应”的影响。
