Evaluation of a cow-side test for detection of gram-negative bacteria in milk from cows with mastitis.
A modified Limulus amebocyte lysate (LAL) cow-side test was evaluated under field conditions. The principle of the test is to visualize reactions between test components and endotoxin from the cell wall of Gram-negative bacteria. The practical purpose is to detect such bacteria in mastitic milk. Secretions from 789 udder quarters with clinical mastitis were examined by the LAL-test. Parallel quarter milk samples were sent to a mastitis laboratory of microbiological examination. Eleven veterinary surgeons in three veterinary districts in Norway performed the field investigations. Results of the LAL-test and culture agreed in 93% of all milk samples tested, agreement measured by kappa being 0.63. The sensitivity of the test in detecting Gram-negative bacteria was 63%, while the specificity was 97%. The predictive value of a positive test result was 70%, the figure being somewhat higher (75%) when the material was limited to milk samples without antibiotic residues. The predictive value of a negative test result was 95%. The LAL-test is considered to constitute a valuable cow-side test for the veterinary practitioner, aiding the selection of antibacterial drug of choice for the initial treatment of clinical mastitis.
Waage
S
S
National Veterinary Institute, Oslo, Norway.
Jonsson
P
P
Franklin
A
A
D000818:Animals; D002417:Cattle; D005260:Female; D006090:Gram-Negative Bacteria / Q000302:isolation & purification*; D016905:Gram-Negative Bacterial Infections / Q000175:diagnosis / Q000662:veterinary*; D008033:Limulus Test / Q000662:veterinary; D008414:Mastitis, Bovine / Q000175:diagnosis*; D008892:Milk / Q000382:microbiology*; D011237:Predictive Value of Tests