Sawant Ashish A, Pillai Shreekumar R, Jayarao Bhushan M
Department of Veterinary Science, The Pennsylvania State University, University Park 16802, USA.
J Dairy Sci. 2002 May;85(5):1127-32. doi: 10.3168/jds.S0022-0302(02)74174-X.
Five selective media including Edwards modified medium, Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L), Streptococcus selective medium, Streptosel agar, and thallium-crystal violet-toxin-ferric citrate medium were evaluated for the isolation of streptococci and streptococci-like organisms from raw milk. The sensitivity and specificity of these selective media for streptococci and streptococci-like organisms were determined by using American Type Culture Collection reference strains. Under experimental conditions Edwards modified medium with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) showed the highest sensitivity (100%) and specificity (100%) for streptococci and streptococci-like organisms followed by thallium-crystal violettoxin-ferric citrate medium, Edwards modified medium, Streptococcus selective medium, and Streptosel agar. Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) allowed growth of all streptococci and streptococci-like organisms, while inhibiting growth of the staphylococci and gram-negative reference strains. Bulk tank milk samples from 114 dairy herds were spiral plated onto Edwards modified medium with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L). A total of 344 isolates (at least three isolates from each sample) were randomly selected and identified to their species. This medium permitted growth of 328 streptococci and streptococci-like organisms belonging to genera Aerococcus, Enterococcus, Gemella, Lactococcus, Streptococcus, and Vagococcus. When Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) was evaluated using bulk tank milk samples, the sensitivity and specificity of this medium for streptococci and streptococci-like organisms were observed to be 100 and 87.5%, respectively. The positive predictive value for streptococci and streptococci-like organisms was observed to be 99.4%. The results of the study indicate that Edwards modified medium supplemented with colistin sulfate (5 mg/L) and oxolinic acid (2.5 mg/L) can be used as a selective medium for the isolation of streptococci and streptococci-like organisms from bulk tank milk.
对五种选择性培养基进行了评估，包括爱德华兹改良培养基、添加硫酸黏菌素（5毫克/升）和恶喹酸（2.5毫克/升）的爱德华兹改良培养基、链球菌选择性培养基、链球菌琼脂和铊-结晶紫-毒素-柠檬酸铁培养基，用于从生牛奶中分离链球菌和类链球菌微生物。通过使用美国典型培养物保藏中心参考菌株来确定这些选择性培养基对链球菌和类链球菌微生物的敏感性和特异性。在实验条件下，添加硫酸黏菌素（5毫克/升）和恶喹酸（2.5毫克/升）的爱德华兹改良培养基对链球菌和类链球菌微生物显示出最高的敏感性（100%）和特异性（100%），其次是铊-结晶紫-毒素-柠檬酸铁培养基、爱德华兹改良培养基、链球菌选择性培养基和链球菌琼脂。添加硫酸黏菌素（5毫克/升）和恶喹酸（2.5毫克/升）的爱德华兹改良培养基允许所有链球菌和类链球菌微生物生长，同时抑制葡萄球菌和革兰氏阴性参考菌株的生长。将来自114个奶牛群的大罐牛奶样品螺旋接种到添加硫酸黏菌素（5毫克/升）和恶喹酸（2.5毫克/升）的爱德华兹改良培养基上。总共随机选择344个分离株（每个样品至少三个分离株）并鉴定到种。该培养基允许属于气球菌属、肠球菌属、孪生球菌属、乳球菌属、链球菌属和漫游球菌属的328个链球菌和类链球菌微生物生长。当使用大罐牛奶样品评估添加硫酸黏菌素（5毫克/升）和恶喹酸（2.5毫克/升）的爱德华兹改良培养基时，观察到该培养基对链球菌和类链球菌微生物的敏感性和特异性分别为100%和87.5%。观察到链球菌和类链球菌微生物的阳性预测值为99.4%。研究结果表明，添加硫酸黏菌素（5毫克/升）和恶喹酸（2.5毫克/升）的爱德华兹改良培养基可作为从大罐牛奶中分离链球菌和类链球菌微生物的选择性培养基。
