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Microbiological and molecular genetic characterization of Staphylococcusaureus and Staphylococcuspseudintermedius

Coagulase-positive staphylococci are an important infectious agentcausing numerous infections in animals. Staphylococcus aureus andStaphylococcus pseudintermedius share a number of similar cultural andbiochemical characteristics, which makes their differentiation difficult.Since these species have different zoonotic potential, it is advisable todevelop rapid and specific schemes for species differentiation of pathogens.We have studied the cultural and biochemical characteristics ofStaphylococcus spp. isolated from dogs, cats and cows. In total, 103halophilic coccal cultures were isolated from companion animals and45 from cows, of which 55 and 30 cultures were coagulase-positivestaphylococci, respectively. The reactions that can be used to differentiateS. pseudintermedius and S. aureus were studied. Growth inhibition zonesaround the disk with polymyxin B antibiotic for S. pseudintermediuswere statistically higher (p<0.001) than for S. aureus. The determinationof acetone production to differentiate between these pathogens hasless specificity, as 30% of S. pseudintermedius showed a false-positivereaction. The belonging of two isolates to the species Staphylococcuspseudintermedius was confirmed by MALDI-TOF.The virulence of staphylococci is due to the presence of genesthat regulate the synthesis of various pathogenicity factors and causeantibiotic resistance. Molecular genetic methods can detect the presenceof gene specificity and help to assess the risk of a particular strain causinginfection. Using classical and real-time PCR, the mecA gene was detectedin 8 S. aureus strains and 1 S. pseudintermedius strain that showedphenotypic resistance to methicillin. The pathogenicity genes lukF andsiet were present in 100%, and the lukS gene in 90% of the studiedStaphylococcus pseudintermedius.The study highlights a number of aspects of the diagnosis anddifferentiation of coagulase-positive staphylococci. The possibility ofusing the Neonatal FAST well D-ONE microculture system for use inveterinary laboratories was also studied. The data obtained can be usedto develop methodological approaches to the identification of pathogenicstaphylococci using a combination of different methods.

Key words: S. pseudintermedius, resistance to methicillin,pathogenicity genes, MALDI-TOF MS.


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