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