Occurrence of Antibiotic-resistant Bacteria to Streptomycin and Oxytetracycline in Agricultural Soils of Gangwon State

초록

Soil can be a natural reservoir of antibiotic-resistant bacteria (ARB) and is capable of transferring them to the environment. The spreading of ARB can be affected by geographical factors such as land type and altitude. This study investigated the occurrence of antibiotic-resistant bacteria from agricultural soils in five regions of Gangwon State, South Korea, focusing on two commonly used agricultural antibiotics, streptomycin (ST) and oxytetracycline (OTC). Soil samples were collected from two plane land fields (Cheorwon, Chuncheon) and three high land fields (Gangneung, Jeongseon, Taebaek) for isolation of ARB against ST and OTC. Thirty-four bacterial strains were isolated, showing resistance to ST and OTC. Examination of cross-resistance between the two antibiotics found that some strains resistant to ST also exhibited reduced susceptibility to OTC, and vice versa. Remarkably, the bacterial strains, CW1 and TB7, showed the highest cross-resistance between the two antibiotics and they were from either plane land fields or high land fields. The strains were identified as diverse genera such as Pseudomonas sp., Lysobacter sp., Telluria sp., Pseudarthrobacter sp., Stenotrophomonas sp., Microbacterium sp., and Flavobacterium sp. The results in this study infer the potential for the spread of ARB or related genes from high land in sloped fields. Taken together, it should be emphasized that a need for careful monitoring of the occurrence of ARB in different types of fields to protect the environment as well as sustainable agriculture by preventing the further spread of these bacteria and related antibiotic-resistant genes in the environment.

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