ANSWER TO QUESTION OF THE WEEK! The mastitis pathogen in these photos is PSEUDOMONAS. Its colonies on blood agar are large, flat, shiny, and beta-hemolytic (surrounded by a zone of clearing), while on MacConkey agar its colonies are tan or pale pink in color and translucent (clear or semi-clear). These colonies typically have an odor similar to artificial grape flavoring. The identification of Pseudomonas is confirmed by a positive result on the oxidase test. Spraying water while cows are in the parlor is a key risk factor for Pseudomonas mastitis infections. This organism is notorious for thriving in water hoses, water storage tanks, and cisterns (& hot tubs!). It forms a biofilm on surfaces to protect itself from disinfectants. As a gram-negative bacteria, clinical cases can cause systemic illness (“toxic mastitis”), but most cases are mild or moderate in severity. Pseudomonas mastitis infections are unresponsive to treatment and become chronic, because of low antibiotic susceptibility and biofilm protection.
Posted on: Thu, 16 Oct 2014 16:24:42 +0000
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