Tracing Mastitis Pathogens—Epidemiological Investigations of a <i>Pseudomonas aeruginosa</i> Mastitis Outbreak in an Austrian Dairy Herd
2021
Bernhard Schauer | Regina Wald | Verena Urbantke | Igor Loncaric | Martina Baumgartner
The present study describes an outbreak of <i>Pseudomonas (P.) aeruginosa</i> mastitis in a 20-cow dairy herd where throughout genotyping of isolates reusable udder towels were identified as the source of infection. Sampling of cows during three herd surveys and bacteriological culturing showed that <i>P. aeruginosa</i> was isolated from nine cows with a total of 13 infected quarters. Mastitis occurred as mild clinical or subclinical infection. <i>P. aeruginosa</i> was additionally isolated from a teat disinfectant solution, containing N-(3-aminopropyl)-N-dodécylpropane-1,3-diamine 1 as active component, and microfiber towels used for pre-milking teat preparation. Disc diffusion antimicrobial resistance testing revealed that all isolates were susceptible to piperacillin, piperacillin-tazobactam, ceftazidime, cefepime, aztreonam, imipenem, meropenem, tobramycin, amikacin, and ciprofloxacin. Thirty-two isolates of milk samples and 22 randomly selected isolates of one udder towel and of the teat disinfectant solution were confirmed as <i>P. aeruginosa</i> with matrix-assisted laser desorption, ionization time-of-flight mass spectrometry (MALDI Tof MS). Isolates were further characterized with rep-PCR and randomly amplified polymorphic DNA (RAPD) as well as with multiple locus variable-number tandem repeat analysis (MLVA). Results obtained in this study suggested that one single strain was responsible for the whole outbreak. The transmission occurred throughout a contaminated teat cleaning solution as a source of infection. The farmer was advised to change udder-preparing routine and to cull infected cows.
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