酸奶中乳酸菌耐药性

Antibiotics resistance of lactic acid bacteria isolated from yoghurt

目的探究酸奶中乳酸菌在不同浓度的不同抗生素传代诱导培养下,乳酸菌耐药性变化情况及产生规律。方法以实验室前期研究分离的保加利亚乳酸杆菌(Lactobacillus bulgaricus)和嗜热链球菌(Streptococcus thermophilus)为实验菌株,分别使2种菌在不同浓度抗生素作用下传代培养,并对培养后菌株分别进行抑菌圈测定,以判断其对抗生素的敏感性。结果保加利亚乳酸杆菌(L. bulgaricus)和嗜热链球菌(S. thermophilus)经氨苄青霉素、硫酸庆大霉素和氯霉素低浓度(1.0×10–4~1.0×10–10 mg/mL)耐药诱导培养后表现出耐药;经1.0×10–2 mg/mL氨苄青霉素诱导培养的保加利亚乳酸杆菌(L. bulgaricus)和经1.0×10–6 mg/mL氨苄青霉素诱导培养的嗜热链球菌(S. thermophilus),药敏实验中其抑菌圈直径随着传代次数增加而减小(r(L. b)=–0.84,r(S. t)=–0.98,P <0.05),而经低浓度(1.0×10–10 mg/mL)氨苄西林钠诱导培养的2种乳酸菌的抑菌圈直径则随着传代次数的增加而增大(r(L. b)=0.96,r(S. t)=0.82,P <0.05),氯霉素和硫酸庆大霉素对保加利亚乳酸杆菌(L. bulgaricus)和嗜热链球菌(S. thermophilus)的抑菌圈直径不随传代次数的增加而发生变化,P值均> 0.05。结论长时间接触低浓度抗生素会导致保加利亚乳酸杆菌(L. bulgaricus)和嗜热链球菌(S. thermophilus)产生耐药性,故在生产实践中要加强酸奶中乳酸菌的耐药性监测和原料乳中抗生素残留的控制以防乳酸菌耐药性的产生。

Objective To explore patterns and variations of antibiotic resistance of lactic acid bacteria isolated from yoghurt after serial subcultivation with antibiotics at various concentrations. Methods Previously isolated strains of lactic acid bacteria(Lactobacillus bulgaricus [L. bulgaricus] and Streptococcus thermophilus [S. thermophilus]) were cultivated under the different concentration of antibiotics. Then, the sensitivity to the antibiotics of the strains were evaluated by detecting inhibition zone diameters. Results Both stains of L. bulgaricus and S. thermophilus exhibited resistance to antibiotics after incubation with low concentration(1.0 × 10 –4 – 1.0 × 10 –10 mg/mL) of ampicillin, gentamicin sulfate and chloramphenicol. The diameter of the inhibition zone decreased significantly with the increment of serial subcultivation for the strain of L. bulgaricus incubated with 1.0 × 10 –2 mg/mL ampicillin and the strain of S. thermophilus with 1.0 ×10 –6 mg/mL ampicillin(r(L. b)=– 0.84, r(S. t)=– 0.98, both P < 0.05). However, for both L. bulgaricus and S. thermophilus incubated with low concentration of ampicillin sodium, the diameter of the inhibition zone increased with the increment of serial subcultivation(r(L. b)= 0.96, r(S. t)= 0.82, P < 0.05). While, the diameter of the inhibition zone demonstrated no significant variation with the increment of serial subcultivation for the strains of L. bulgaricus and S. thermophilus incubated with gentamicin sulfate and chloramphenicol(both P > 0.05). Conclusion Long term exposed to low concentration antibiotics will lead to antibiotic resistance in L. bulgaricus and S. thermophilus. Therefore, monitoring on antibiotic residues in raw milk and antibiotic resistance of lactic acid bacteria should be strengthened in the production of yoghurt.