Petzer Inge-Marie, Karzis Joanne, Van der Schans Theodorus J, Watermeyer Johanna C, Mitchell-Innes Norman, Eloff Stephanie, Fosgate Geoffrey T
Department of Production Animal Studies, University of Pretoria, Onderstepoort.
Onderstepoort J Vet Res. 2012 Feb 10;79(1):E1-6. doi: 10.4102/ojvr.v79i1.343.
The aim of this study was to compare the effects of cryopreservation at approximately -196 °C in liquid nitrogen (N) and freezing at approximately -20 °C in a freezer, on the viability and survival of eight different mastitogenic bacteria inoculated in milk. Bacteria were frozen at approximately -20 °C in a freezer and cryopreserved at approximately -196 °C in liquid nitrogen. An effective preservation method was needed for follow-up samples from cows identified in the South African National Milk Recording Scheme (NMRS) with somatic cell counts above 250 000 cells/mL milk. The organisation responsible for sample collection of the NMRS milk samples also provides producers with liquid nitrogen for their semen flasks at the collection sites. This existing mode of storage and transport could therefore be utilised.Ten samples of each organism were thawed and cultured bi-weekly until week 18 for both temperature treatments. An additional sampling was performed at week 30 for samples frozen at approximately -20 °C. Freezing and cryopreservation did not impair subsequent isolation of Streptococcus dysgalactiae, Streptococcus uberis, Enterococcus faecalis, Staphylococcus aureus (STH) (phage type lytic group III) or Sta. aureus (STA) (phage typed, other than lytic group III). Survival was indicated by the isolation of bacteria from samples, and viability by the strength of growth of the bacteria isolated. The survival of Streptococcus agalactiae decreased after week 12 and Escherichia coli after week 16 of freezing, but both organisms survived under cryogenic preservation until week 18. Coagulase-negative staphylococci survived until week 18 for both freezing and cryogenic preservation.Both storage methods could thus contribute to the improvement of a pro-active approach towards udder health management in South African dairy herds.
本研究的目的是比较在液氮中约-196°C冷冻保存和在冰箱中约-20°C冷冻对接种于牛奶中的8种不同致乳腺炎细菌的活力和存活率的影响。细菌分别在冰箱中约-20°C冷冻以及在液氮中约-196°C冷冻保存。对于南非国家牛奶记录计划（NMRS）中鉴定出的体细胞计数高于每毫升牛奶250000个细胞的奶牛的后续样本，需要一种有效的保存方法。负责NMRS牛奶样本采集的机构也在采集地点为生产商提供液氮用于精液瓶。因此，可以利用这种现有的储存和运输方式。对每种微生物的10个样本进行解冻，并每两周培养一次，两种温度处理均持续到第18周。对于在约-20°C冷冻的样本，在第30周进行了额外采样。冷冻和冷冻保存均未影响随后对无乳链球菌、乳房链球菌、粪肠球菌、金黄色葡萄球菌（STH）（噬菌体III型裂解群）或金黄色葡萄球菌（STA）（除III型裂解群外的噬菌体分型）的分离。通过从样本中分离细菌来表明存活率，通过分离出的细菌的生长强度来表明活力。无乳链球菌在冷冻12周后存活率下降，大肠杆菌在冷冻16周后存活率下降，但两种微生物在低温保存下均存活至第18周。凝固酶阴性葡萄球菌在冷冻和低温保存下均存活至第18周。因此，两种储存方法都有助于改进南非奶牛群乳房健康管理的积极方法。
