台灣北部與東部乳牛場細菌藥物感受性及乳汁中藥物殘留調查

Abstract

本研究針對台灣北部及東部共16場乳牛場進行乳牛及所生產生乳、牧場環境及工作人員的口腔、鼻腔等分離細菌進行抗生素感受性試驗，並同時調查生乳及總乳中的藥物殘留。結果共分離到226株的大腸桿菌（Escherichia coli，其中包括2株的腸出血型大腸桿菌E. coli O157:H7）、30株的假性單胞菌（Pseudomonas spp.，其中包括7株綠膿桿菌P. aeruginosa）、271株的腸球菌（Enterococcus spp.）、314株的葡萄球菌（Staphylococcus spp.）及195株的鏈球菌（Streptococcus spp.）。分離菌共有88%具磺胺二甲氧嘧啶（sulfadimethoxine）抗藥性，革蘭氏陰性分離菌則有48%（249/515）具羥四環黴素（oxytetracycline）抗藥性及78%（404/515）對鏈黴素（streptomycin）有抗藥性。東部牧場陽性分離菌之抗藥性較北部嚴重，顯示低污染環境並未減少抗藥性產生。本研究在不同地區分離到2株產vt2腸毒素的E. coli O157:H7，與過去台灣分離株相較分別有82%及67%的親緣性相似度。乳汁樣本以酵素免疫分析套組檢測盤尼西林（penicillin）、鏈黴素及羥四環黴素，結果顯示總殘留率為6.5%，16個總乳樣本亦有5個羥四環黴素殘留，並有超過食品衛生管理法動物用藥殘留標準樣本。本研究提供乳牛場常用抗菌藥物之感受性情形，其結果顯示目前需要更周延的策略才足以讓產食動物牧場更嚴謹及安全的使用抗菌藥物。

Bacteria isolated from dairy cows, dairy farm environments, and dairy workers in two geographically different areas - eastern and northern Taiwan - were evaluated for antibiotic susceptibility. The residues of antibiotics in raw milk of the same farms were also screened. There were 1346 bacteria identified, including 226 Escherichia coli (2 E. coli O157:H7), 271 Enterococcus spp., 30 Pseudomonas spp. (7 P. aeruginosa), 314 Staphylococcus spp., 195 Streptococcus spp., 51 other Gram-positives and 259 other Gram-negatives. Among them, 88% of the isolates were resistant to sulfadimethoxine. The percentages of Gram-negative bacteria resistant to oxytetracycline and streptomycin were 48% (249/515) and 78% (404/515), respectively. Gram-positive bacteria isolated from eastern Taiwan, the least polluted region of Taiwan, were found to have more antibiotic resistance than those isolated from northern Taiwan. Two E. coli O157:H7 from two different geographical areas were isolated and both showed vt2-positive but vt1-negative, and had phylogenetic similarities of 82% and 67%, respectively, to previous Taiwan isolates. This study detected 6.5% of residues oxytetracycline, penicillin, and streptomycin in raw milk samples. Oxytetracycline was detectable in the tank milk of five out of the sixteen dairy farms. Residue levels of antibiotics exceeding regulated concentrations were also observed. Information on antibiotic susceptibility of dairy farms may serve as a baseline for future studies and may also highlight the need to formulate better regulation strategies for the safe use of antibiotics on food-producing farms.