Effects of antimicrobials over sessile and planktonic microbiota associated with an industrial cooling water system

The bacterial community from a cooling water system was investigated through culture-dependent and independent strategies, and the responses of planktonic and sessile bacteria (grown in glass slides and stainless-steel coupons) to antimicrobials of industrial and clinical use were assessed. The morphotypes with higher biofilm-forming potential were <i>Pseudoxanthomonas</i> sp., <i>Rheinheimera</i> sp., <i>Aeromonas</i> sp. and <i>Staphylococcus</i> sp., and the first also exhibited lower susceptibility to all antibiotics and biocides tested. 16S rRNA high throughput sequencing indicated that Pseudomonadota (77.1% on average, sd 11.1%), Bacteroidota (8.4, sd 5.7%), and Planctomycetota (3.0, sd 1.3%) were the most abundant phyla. KEGG orthologs associated with antibiotics and biocide resistance were abundant in all samples. Although the minimum inhibitory and bactericidal concentrations were generally higher for biofilms, morphotypes in planktonic form also showed high levels of resistance, which could be associated with biofilm cells passing into the planktonic phase. Overall, monochloramine was the most effective biocide.

本研究通过依赖培养与非依赖培养的研究策略，对某冷却水系统中的细菌群落展开调查，并评估了浮游菌以及附着在载玻片、不锈钢试片上的定殖菌对工业及临床常用抗菌剂的响应。具有较高生物膜形成潜力的菌群形态型为假黄色单胞菌属（Pseudoxanthomonas）未定种、莱茵海默氏菌属（Rheinheimera）未定种、气单胞菌属（Aeromonas）未定种与葡萄球菌属（Staphylococcus）未定种，其中假黄色单胞菌属同时对本次测试的所有抗生素与杀菌剂表现出更低的敏感性。16S rRNA高通量测序结果显示，丰度位居前三的菌门依次为变形菌门（Pseudomonadota，平均相对丰度77.1%，标准差11.1%）、拟杆菌门（Bacteroidota，8.4%，标准差5.7%）以及浮霉菌门（Planctomycetota，3.0%，标准差1.3%）。与抗生素及杀菌剂抗性相关的KEGG直系同源基因（KEGG orthologs）在所有样本中均呈现高丰度分布。尽管生物膜的最低抑菌浓度（minimum inhibitory concentration, MIC）与最低杀菌浓度（minimum bactericidal concentration, MBC）普遍更高，但浮游态的菌群形态型同样表现出较高的耐药水平，这一现象可能与生物膜细胞解离进入浮游相有关。综合来看，一氯胺是本次测试中效果最优的杀菌剂。