Evaluation of 4 different teat disinfection methods prior to collection of milk samples for bacterial culture in dairy cattle

摘要

The first objective of this study was to determinewhether differences would occur among teat endpreparation techniques with regard to potential contaminationof milk samples collected for bacterial culture.The second objective was to determine whetherdifferences would be detected in genus or species ofbacteria isolated from samples collected using thevarious methods as well as from contaminated oruncontaminated samples. Mammary quarter foremilksamples were collected from lactating dairy cattle atthe University of Missouri Foremost Research DairyFarm (Columbia). Four different teat end preparationmethods were used to compare contamination rates inmilk samples. Sampling techniques used before milkcollection included (1) no preparation, (2) pre-milkingdisinfection and single-use towel drying of teats only,(3) scrubbing of the teat end with alcohol only, and(4) pre-milking disinfection, single-use towel drying,and scrubbing of the teat end with alcohol. Milk wasplated on Columbia blood agar. Cultures were readat 48 h, with the number of morphologically differentbacterial colony types quantified and isolated. Isolateswere identified using MALDI-TOF mass spectrometry.Median numbers of colony types were compared amonggroups using Kruskal-Wallis ANOVA with post-hocpairwise comparisons, and proportional data werecompared using the chi-squared test. A total of 168cows, including 665 quarters, were sampled, and 1,614isolates resulted. Analysis with MALDI-TOF identified29 unique genera and 81 unique species amongthe samples. More contaminated samples occurred ingroups 1 and 2 compared with groups 3 and 4. Group3 had more contaminated samples than group 4. Themajority of Pseudomonas spp. isolates were identifiedwithin group 2. When applying previously describedniches to Staphylococcus spp., environmental specieswere more likely to be identified among contaminatedsamples, whereas host-adapted species were more likelyto be identified among uncontaminated samples. Thesedata confirm that scrubbing the teat end with alcoholafter pre-milking disinfection with an iodine-based teatdisinfectant and drying of the teat minimizes contaminationof the milk sample.