Tracing Mastitis Pathogens—Epidemiological Investigations of a <i>Pseudomonas aeruginosa</i> Mastitis Outbreak in an Austrian Dairy Herd

• Main Authors: Bernhard Schauer, Regina Wald, Verena Urbantke, Igor Loncaric, Martina Baumgartner
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Animals
• Subjects: <i>Pseudomonas aeruginosa</i>; mastitis; transmission route; udder cleaning microfiber towels; MLVA
• Online Access: https://www.mdpi.com/2076-2615/11/2/279

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.