Why should I submit samples for bacteriology?
Sampling cases of clinical mastitis and periodically submitting these for bacteriology testing will give valuable information about the type of bacteria causing infections. This information can be used alongside cell count and mastitis case data to provide insight into appropriate changes required to improve udder health.
Do I have to freeze samples for bacteriology?
No. However, if you are collecting samples from clinical cases or high cell count cows, freezing allows the sample to 'keep' for longer. Frozen samples will remain suitable for culture for up to 6 months, allowing batches of samples to be submitted. If you are submitting bulk tank samples or water samples for differential counts, these must NOT be frozen.
It seems excessive… Do I really have to bother to clean the cow’s teats?
A good sampling technique is essential if meaningful results are going to be generated from the samples you collect. The reason for this is that many of the pathogens that cause mastitis are also in the environment and if samples aren’t collected appropriately it is impossible to differentiate causal organism from contaminants. Also, the teat canal and teat skin are often colonized by minor pathogens and without thorough cleaning and stripping of fore-milk these might predominate in your sample.
Do you test all isolates for sensitivity to antibiotics?
No, we only test isolates from samples as requested. However, we routinely test all Staphylococcus aureus isolates for penicillin sensitivity as this can be a useful indicator of likely response to treatment.
What about testing for Mycoplasma species?
QMMS offers Mycoplasma culture although turnaround times are slower as these organisms take some time to grow. Whilst samples are incubated for Mycoplasma culture, standard bacteriology testing is also undertaken to rule out involvement of other pathogens.
Can I freeze samples that are to be submitted for Mycoplasma spp. culture?
No, samples for Mycoplasma spp culture must be collected, chilled and submitted for culture as quickly as possible as they can lose viability quite quickly.
Is it worth culturing my bulk tank to try to identify mastitis pathogens?
This is a difficult question and the answer is not straight forward. In reality it depends on what pathogens you are looking for. For contagious pathogens that are ‘specific’ to the udder, such as Streptococcus agalactiae and to a lesser extent Staphylococcus aureus this can be a useful screening exercise (though the former is now very rare in the UK). It can also be a useful way to screen a herd for the presence of Mycoplasma spp. However, for most bacterial species (particularly environmental organisms) it is not useful as the organism is unlikely to have originated from an infected cow. That said, on occasions the presence of large numbers of Streptococcus uberis in a bulk milk sample can reflect the presence of an infected cow in the herd.
We’re starting ‘selective dry cow therapy’ – should we do some bacteriology?
If so what’s appropriate? We recommend strategic sampling of some high SCC cows in late lactation to better understand the pathogens you need to cure at drying off and of clinical mastitis cases in early lactation to get an insight into the main pathogens causing new intra-mammary infection in the dry period. A bulk tank sample is NOT an appropriate way to approach or justify blanket antibiotic use at drying off.
