Interference of <i>Streptococcus agalactiae</i> Blitz Therapy in <i>Staphylococcus aureus</i> Microbiological Diagnosis in Subclinical Bovine Mastitis
2024
Ana Flávia Novaes Gomes | Fúlvia de Fátima Almeida de Castro | Márcio Roberto Silva | Carla Christine Lange | João Batista Ribeiro | Alessandro de Sá Guimarães | Guilherme Nunes de Souza
Bovine mastitis is an important and costly disease to dairy cattle. Diagnostic methods usually performed in Brazil are somatic cell counts (SCC) and milk microbiology. Low bacteria shedding in milk implies no colony growth in microbiological tests and false negative results. <i>Streptococcus agalactiae</i> and <i>Staphylococcus aureus</i> are principal pathogens of mixed mastitis. However, <i>S. agalactiae</i> has a higher bacterial release from the mammary gland than <i>S. aureus</i>, affecting microbiological sensitivity to diagnose <i>S. aureus</i>. This study aimed to estimate the SCC and total bacterial count (TBC) from cows according to pathogen isolated in milk and to evaluate variation in <i>S. aureus</i> diagnosis by a microbiological test during <i>S. agalactiae</i> treatment, which is called blitz therapy. Both <i>S. agalactiae</i> and <i>S. aureus</i> presented high SCC means, although <i>S. agalactiae</i> showed shedding of bacteria 2.3 times greater than <i>S. aureus</i>. Microbiological sensitivity to <i>S. aureus</i> increased for 5 months during <i>S. agalactiae</i> treatment. The prevalence of <i>S. agalactiae</i> fell after 5 months of therapeutic procedures. The prevalence of <i>S. aureus</i> increased to 39.0. The results showed that due to high sensitivity, the polymerase chain reaction (PCR) could be used at the beginning of blitz therapy with the goal of <i>S. agalactiae</i> eradication from the dairy herd.
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