广州市售鱼、虾、蛤蚌中四环素耐药菌及四环素耐药基因的研究

Tetracycline-resistant Bacteria and Tetracycline-resistant Genes from Fish, Shrimp, and Clams in Guangzhou

摘要:

本文以广州市大型超市的鱼、虾、蛤蚌为研究对象，研究其四环素耐药菌的分布及四环素耐药基因的携带情况。采用平板涂布法分离四环素耐药菌并统计菌落数，计数结果在102~106 CFU/g之间，其中鱼肠中四环素耐药菌的数量达106 CFU/g。通过PCR对样本总DNA中四环素耐药基因的携带情况进行检测，发现每个样本均携带多个（3~7个）四环素耐药基因。9种四环素耐药基因中，tet(E)的检出率最高6.3%，其次分别为tet(S) (5.1%)，tet(M) (3.1%)，tet(C) (1.7%)和tet(G) (0.9%)。Southern杂交试验表明四环素抗性菌株Aeromonas spp.和Escherichia coli携带的耐药基因tet(E)存在于质粒上；在无四环素选择压力下对上述两种菌株进行连续传代，其耐药质粒仍稳定存在于菌株中。本研究表明广州市售鱼、虾、蛤蚌中分离得到的细菌对四环素耐药情况较为严重，应得到相关监管部门以及消费者的足够重视。

Abstract:

Aquatic products (fish, shrimps, and clams) from markets in Guangzhou (Guangdong Province) were tested to determine the presence and distribution of tetracycline (Tet)-resistant (Tetr) genes and bacterial species. The plate-spread method was employed to isolate Tet-resistant bacterial species, allowing detection of 102 CFU to 106 CFU/g Tetr bacteria, with the highest number of Tetr-bacteria counts (106 CFU/g) detected in fish intestines. Conventional polymerase chain reaction (PCR) was conducted on total DNA extracted from product tissues (muscles or intestines) to detect the presence of selected Tetr genes. Results indicated that all host-related samples (tissue and tank water) expressed three to seven Tetr genes. Among nine Tetr genes in this study, tet(E) was found at the highest frequency (6.3%), followed by tet(S) (5.1%), tet(M) (3.1%), tet(C) (1.7%), and tet(G) (0.9%). Southern hybridization showed that tet(E) genes were integrated into the plasmid of Tet-resistant bacteria species Aeromonas spp. and Escherichia coli. Additionally, the Tet-resistant plasmids exhibited good stability, even in the absence of Tet-selective pressure. These results indicated that Tet-resistance was common and serious among bacteria isolated from fish, shrimp, and clams collected from markets in Guangzhou.