Baird-Parker琼脂上被抑制的金黄色葡萄球菌的筛选与特征研究

目的对在Baird-Parker琼脂平板上被抑制的金黄色葡萄球菌(以下简称金葡菌)的遗传特征进行深入研究,并提出针对性检验措施。方法通过对127株不同来源的金葡菌和8株金葡菌标准菌株在Baird-Parker琼脂平板上进行测试,筛选在Baird-Parker琼脂平板上被抑制的金葡菌,并对菌株的遗传特征进行分析,同时检测Baird-Parker琼脂平板中的抑菌成分对金葡菌的抑制作用。结果 3株分离自北京猪肉馅中的菌株和金葡菌标准菌株(CMCC 26112)在Baird-Parker琼脂上生长率低于万分之一,Baird-Parker琼脂基础培养基中添加甘氨酸(12.0 g/L)可明显抑制这4株金葡菌的生长,而六水合氯化锂(5.0 g/L)、丙酮酸钠(10.0 g/L)和卵黄亚碲酸钾(50 ml)的添加对这4株金葡菌的生长没有明显影响;这4株菌在高盐甘露醇琼脂和科马嘉显色平板上的生长率均高于60%;脉冲场电泳(PFGE)分析发现,北京来源的3株金葡菌为同一PFGE型别,与标准菌株(CMCC 26112)存在明显差异。结论为保证食品安全国家标准检验方法 GB 4789.10—2010对不同金葡菌计数的覆盖性,计数检验过程中应使用两种或两种以上金葡菌选择性平板。

Screening and characterization of Staphylococcus aureus isolates inhibited on Baird-Parker agar

To characterize the Staphylococcus aureus(S.aureus) isolates that were inhibited on Baird-Parker agar and propose the possible solutions for the enumeration of these isolates.Methods The isolates inhibited on Baird-Parker agar were identified from 127 S.aureus isolates from different sources and eight S.aureus reference strains. The characteristics of these isolates were analyzed and the inhibitory effects of the components in Baird-Parker were determined. Results Three S.aureus isolates from the ground pork samples in Beijing and a reference strain S.aureus (CMCC 26112) showed poor growth on Baird-Parker agar. The glycine (12.0 g/L) in the Baird-Parker agar could inhibit the growth of these four isolates, and the supplement of sodium pyruvate, lithium chloride and egg yolk potassium tellurite didn''t inhibit the growth of these isolates. These four isolates showed over 60% growth rate on mannitol salt agar and chromogenic agar. The pulsed field gel electrophoresis (PFGE) showed that three isolates from Beijing had the same PFGE pattern which was significantly different from the pattern of (CMCC 26112).Conclusion To guarantee the good coverage of the national food safety standard GB 4789.10-2010 on S.aureus, two or more categories of agar plates should be used in the S.aureus enumeration of food samples.