Puzzling lab results, mastitis, please help!

[Obsidian_Fire]

Last Tuesday (a week ago) I arrived at the barn to find my mare in a full-blown mastitis event. Udder swollen, goo hanging from the teats, edema from the udder forward almost a foot.
Straight to vet we went. Vet milked out the most disgusting yellow chunky goop ever, and sent it to pathology. Put mare on SMZ’s.
SAA was over 700.
Took miss mare several days to act “normal”, and not punky. She is still not really eating like normal.
Yesterday, Monday, I talked with vet. Pathology came back and it GREW NOTHING. Vet is very puzzled by this and is going to call the lab to ask questions.

How do you have an obvious infection, yet grow nothing from a culture? What is (or might be) going on here?

[Rosewatt]

I have no idea, but am interested in hearing other experiences or ideas on this matter.

I did find this, which was an interesting read for me: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6417605/

[trubandloki]

Jingles for your mare. That sounds so uncomfortable.

(I can’t answer your question, but just wanted to add support.)

[Obsidian_Fire]

Yes, the usual suspect in these cases is “inappropriate lactation” but in my mare’s case that is not so.

Vet said opportunistic bacteria entered thru the teat hole, and voila!, infection.

[victoriakent]

This is one of my favorite papers. " Idiopathic inappropriate lactation" makes me chuckle every time. My TB mare also randomly lactates year round with no found reason and I always say “well, she is an idiot sometimes so that sounds right.”

[Skip_s_Rider]

Many milk samples from cows with mastitis do not show any growth when cultured. Usually they suspect the infection to be caused a gram negative bacteria, which the cow has cleared on her own. Therefore, there are no live bacteria remaining in the milk. These infections, however, can cause quite severe systemic symptoms such as lethargy, fever, and poor appetite in addition to signs present in and around the udder. These cows often will receive supportive care involving fluids and antiinflammatory drugs.

[Simkie]

Not everything out there cultures. Not every sample is handled appropriately from animal to lab. Not every sample taken is representative of the spectrum of stuff that may grow.

I’d be totally comfortable to chalking this up to “if it walks like a duck, and talks like a duck, it’s a duck” and continue to treat like a mastitis. If it doesn’t improve or respond to your current treatment, repeat the culture. Maybe with a few samples.

Fwiw, when I had a dry mare develop a mastitis, it also took her quite a while to really feel better. We had her on doxy for a month, I think.

[JBCool]

UGGGHH!! Poor mare mare. That sounds awful! Sorry, not more helpful.

[floppyammy]

Ok all, tagging on to this thread from last year as I am facing something that sounds very similar with my mare.

15 yr old maiden mare. Never been bred, not stabled with or near any intact horses. Mare is on dry lot, feed and supplements have not changed in months.

6 days ago mare presented with swollen teats, right far bigger than left, and large swellings in front of teats. Lots of discharge, yellow,/amber in color, thick and sticky. Mare did NOT want to be touched in the area. Handwalked and cold hosed and the swelling came down. Mare was happy to have her teats washed. No temp. Vet appointment scheduled for Monday.

4 days ago temp spikes to 102.2. Vet sedates, milks out really disgusting discharge, puts her on SMZs and takes samples for lab.

Days 3 & 2 on SMZs, her temp goes back to normal but swelling and discharge do not improve.

Today the lab results came back - NO Bacteria present. Vet is stumped. She is consulting a reproductive specialist.

Edited to add: Mare is acting totally normal. Eating, drinking, moving around comfortably. Bright, perky, wondering why we all keep making a fuss about her undercarriage.

@Obsidian_Fire how did you make out with your mare? Were you able to figure out what caused your Mare’s issue and were you able to resolve it?

Current state of teats:

[Simkie]

Not everything cultures. If it looks like infection and smells like infection and creates a fever like infection and responds to antibiotics like infection…

I see I responded last year pretty much identically lol.

[floppyammy]

I was really hoping for the culture to give us some guidance. I feel like the SMZs are helping – to a point – but not enough. Do we just play antibiotic roulette until we find something that works?

[Simkie]

When I had a dry mare with mastitis, it took 30 days of doxy. It takes AWHILE.

The fact your temp is back to normal is at least suggestive that you have good coverage with your current abx. I’d just stay the course.

[OzarksRider]

Do you know if they cultured for anaerobic bacteria?

[floppyammy]

I don’t know if they did or not. I do have the cytology report if that would help.

[Simkie]

Just to further expand on what @Skip_s_Rider states above:

Bacterial Community Profiling of Milk Samples as a Means to Understand...

“Collectively, these results provide evidence that cases of culture negative mastitis can be associated with bacterial species that may be present below culture detection thresholds used here.”

Abstracts378.pdf

“Research in Finland using real-time PCR of 79 clinical mastitis samples with no growth in conventional culture, identified 43% samples as positive for at least one common bacterial pathogen.”

Negative cultures in mastitis isn’t uncommon. I doubt there’s much work done in this vein in equines, but drawing a parallel from bovines isn’t terribly unreasonable.

Even in people, “negative cultures do not rule out mastitis.”

https://apps.sbgh.mb.ca/labmanual/test/view?seedId=40652

[Obsidian_Fire]

Sorry I’m not much help, I think what others have posted is most likely. My vet just said possibly bacteria got up in there thru an opening in the teat that wasn’t completely ‘closed’. She also said if she had a nickel for every case of mastitis she’d be a millionaire by now.
IIRC, we resolved it with SMZ’s.

[floppyammy]

My vet took another sample today. She has been working her contacts across the country and was able to secure some additional testing at Texas A&M. Something about having the ability to detect sub-microscopic levels of proteins and bacteria? I may or may not have that right. And a separate cellular test that could rule in/out a reproductive tumor. Results will be back on Tuesday.

[Simkie]

Maybe PCR? But there might not be much there with the abx on board and doing the job. Do you get a sensitivity out of this additional testing?

[floppyammy]

You’ll have to forgive me - I don’t have the specifics. The office staff relayed the message to me. I’m unfortunately unavoidably out of town this weekend so I wasn’t able to be there for the sample collection. On the plus side my vet seems to be taking this as a personal challenge and has thrown her considerable efforts, contacts and network into figuring this out.