Department of Biological Sciences, California State University, 1250 Bellflower Blvd., Long Beach, CA 90840, USA E-mail:
J Water Health. 2020 Oct;18(5):766-775. doi: 10.2166/wh.2020.100.
Coliforms are important bacterial contamination indicators in recreational waters. Little is known about the antibiotic resistance of coliforms from Southern California beaches. This study examined the numbers of coliforms as well as the incidence of antibiotic-resistant coliforms in beaches with restricted and non-restricted wave action by sampling from the shores of both types of beaches following dry and wet weather. Total coliforms were selected by membrane filtration onto mEndo agar and then enumerated. Randomly selected isolates from each location were screened for resistance to nine classes of antibiotics by disk diffusion, and the multiple antibiotic resistance (MAR) index was calculated. Numbers of total coliforms were significantly higher following rain compared to dry weather. Total coliform numbers were not significantly elevated at non-restricted wave action sites. Restricted wave action sites had a 78.5% increase in MAR index following wet weather compared to dry weather. Resistance to ampicillin was observed in almost 50% of isolates and was not significantly impacted by wave action or weather. Minimum inhibitory concentration testing revealed that many isolates were highly resistant to ampicillin. This study is the first to report on the antibiotic resistance of coliforms found in Southern California beaches and highlights the prevalence of ampicillin resistance.
大肠菌群是休闲水域中重要的细菌污染指标。南加州海滩的大肠菌群的抗生素耐药性知之甚少。本研究通过在干燥和潮湿天气后从两种类型海滩的岸边取样，检查了受限制和不受限制波作用海滩的大肠菌群数量以及抗生素耐药性大肠菌群的发生率。总大肠菌群通过膜过滤到 mEndo 琼脂上进行选择，然后进行计数。从每个地点随机选择的分离物通过纸片扩散法筛选对九类抗生素的耐药性，并计算多重抗生素耐药性（MAR）指数。与干燥天气相比，雨后总大肠菌群数量明显更高。非限制波作用地点的总大肠菌群数量没有明显升高。与干燥天气相比，潮湿天气下受限制波作用地点的 MAR 指数增加了 78.5%。几乎 50%的分离物对氨苄西林有耐药性，波作用或天气对其没有显著影响。最低抑菌浓度试验表明，许多分离物对氨苄西林高度耐药。本研究首次报告了南加州海滩发现的大肠菌群的抗生素耐药性，并强调了氨苄西林耐药性的普遍性。
