Hayes M C, Ralyea R D, Murphy S C, Carey N R, Scarlett J M, Boor K J
Department of Food Science, Cornell University, Ithaca, NY 14853, USA.
J Dairy Sci. 2001 Jan;84(1):292-8. doi: 10.3168/jds.S0022-0302(01)74479-7.
The bacterial composition of bulk tank milk from 13 farms was examined over a 2-wk period to characterize sudden elevations in the total bacterial count referred to as "spikes." Bulk tank milk samples collected at each pick-up were analyzed for standard plate count, Petrifilm aerobic count, somatic cell count, gram-negative organisms, and streptococci. Twenty standard plate count spikes were observed: 12 associated with streptococci, 4 associated with gram-negative organisms, 2 associated with streptococci and gram-negative organisms, and 2 that were not definitively characterized. Spikes ranged from 14,000 to 600,000 cfu/ml. Streptococcus uberis was isolated as the predominant organism from 11 spikes, and Escherichia coli was isolated from 4 spikes. Statistical analysis of total bacterial counts indicated a high correlation (r = 0.94) between standard plate counts and Petrifilm aerobic count. Regression analysis of standard plate counts and Petrifilm aerobic counts yielded the equation log10 (standard plate count) = 0.73 + 0.85log10 (Petrifilm aerobic count), indicating that the correlation, although strong, is not one to one. In a related pilot study, triplicate bulk tank milk samples were collected and analyzed for total bacterial count and presumptive streptococcus, gram-negative, and staphylococcus counts. Two-way ANOVA of these triplicate data indicated a lack of significant variation among the triplicate samples, suggesting that one sample can reliably gauge the microbial status of the entire bulk tank.
在为期2周的时间里，对13个农场的贮奶罐乳的细菌组成进行了检测，以确定总细菌数突然升高（即“峰值”）的特征。每次取奶时收集的贮奶罐乳样品都进行了标准平板计数、Petrifilm需氧菌计数、体细胞计数、革兰氏阴性菌和链球菌分析。观察到20次标准平板计数峰值：12次与链球菌有关，4次与革兰氏阴性菌有关，2次与链球菌和革兰氏阴性菌有关，2次无法明确特征。峰值范围为14,000至600,000 cfu/ml。乳房链球菌是11次峰值中分离出的主要细菌，大肠杆菌从4次峰值中分离得到。总细菌数的统计分析表明，标准平板计数与Petrifilm需氧菌计数之间存在高度相关性（r = 0.94）。标准平板计数与Petrifilm需氧菌计数的回归分析得出方程log10（标准平板计数）= 0.73 + 0.85log10（Petrifilm需氧菌计数），表明这种相关性虽然很强，但不是一对一的。在一项相关的试点研究中，收集了一式三份的贮奶罐乳样品，并分析了总细菌数以及推测的链球菌、革兰氏阴性菌和葡萄球菌计数。对这些一式三份数据的双向方差分析表明，一式三份样品之间没有显著差异，这表明一个样品可以可靠地衡量整个贮奶罐的微生物状态。
