Patterns of mycoplasma shedding in the milk of dairy cows with intramammary mycoplasma infection.
OBJECTIVE
To determine patterns of mycoplasma shedding in the milk of dairy cows with intramammary mycoplasma infection.


METHODS
Prospective clinical trial.


METHODS
10 Holstein cows with intramammary mycoplasma infection.


METHODS
Milk samples were collected from each cow daily for 28 days and plated on mycoplasma agar to evaluate shedding patterns. To determine whether enrichment improved recovery of organisms, some samples were also inoculated in mycoplasma enrichment medium and incubated for 4 days prior to plating. Somatic cell count (SCC) was determined in samples collected weekly.


RESULTS
Mycoplasma organisms were not isolated from 81 of 280 (29%) composite milk samples, but > 10(6) colonies/mL were obtained from 151 (54%). Similarly, mycoplasma organisms were not isolated from 433 of 1,008 (43%) quarter milk samples, but > 10(6) colonies/mL were obtained from 392 (39%). For 71 of 104 (68%) samples, mycoplasma organisms were isolated both following direct plating and following enrichment; for 24 of 104 (23%), mycoplasma organisms were isolated only following enrichment; and for 9 of 104 (9%), mycoplasma organisms were isolated only after direct plating. There was a linear correlation between logarithm of the SCC and logarithm of the number of colony-forming units of mycoplasma per milliliter of milk for composite and quarter milk samples.


CONCLUSIONS
Shedding of organisms was inconsistent in dairy cows with intramammary mycoplasma infection, increasing the risk of misdiagnosis if multiple milk samples are not tested.
Department of Animal Sciences, Washington State University, Pullman, WA 99164, USA.
Mary K
MK
Biddle
Larry K
LK
Fox
Dale D
DD
Hancock
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology; D015169:Colony Count, Microbial / Q000662:veterinary; D005260:Female; D007774:Lactation; D008414:Mastitis, Bovine / Q000382:microbiology*; D008892:Milk / Q000166:cytology / Q000382:microbiology*; D009174:Mycoplasma / Q000302:isolation & purification*; D009175:Mycoplasma Infections / Q000382:microbiology / Q000662:veterinary*; D011446:Prospective Studies