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.

大肠菌群是娱乐水域中重要的细菌污染指标。关于南加州海滩大肠菌群的抗生素耐药性知之甚少。这项研究通过在干燥和潮湿天气后从两种类型的海滩的海岸取样，检查了受限制和不受限制的波浪作用海滩中大肠菌群的数量以及耐抗生素大肠菌群的发生率。通过膜过滤到 mEndo 琼脂上选择总大肠菌群，然后计数。从每个位置随机选择的分离株通过磁盘扩散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，下雨后总大肠菌群的数量显着增加。在非限制性波浪作用部位，总大肠菌群数量没有显着升高。与干燥天气相比，受限制的波浪作用地点在潮湿天气后的 MAR 指数增加了 78.5%。在近 50% 的分离物中观察到对氨苄青霉素的耐药性，并且不受波浪作用或天气的显着影响。最低抑菌浓度试验表明，许多分离株对氨苄青霉素具有高度耐药性。这项研究首次报告了在南加州海滩发现的大肠菌群的抗生素耐药性，并强调了氨苄青霉素耐药性的普遍性。在近 50% 的分离物中观察到对氨苄青霉素的耐药性，并且不受波浪作用或天气的显着影响。最低抑菌浓度试验表明，许多分离株对氨苄青霉素具有高度耐药性。这项研究首次报告了在南加州海滩发现的大肠菌群的抗生素耐药性，并强调了氨苄青霉素耐药性的普遍性。在近 50% 的分离物中观察到对氨苄青霉素的耐药性，并且不受波浪作用或天气的显着影响。最低抑菌浓度试验表明，许多分离株对氨苄青霉素具有高度耐药性。这项研究首次报告了在南加州海滩发现的大肠菌群的抗生素耐药性，并强调了氨苄青霉素耐药性的普遍性。