Microbiological and molecular genetic characterization of Staphylococcus aureus and Staphylococcus pseudintermedius

Abstract

Coagulase-positive staphylococci are an important infectious agent causing numerous infections in animals. Staphylococcus aureus and Staphylococcus pseudintermedius share a number of similar cultural and biochemical characteristics, which makes their diff erentiation diffi cult. Since these species have diff erent zoonotic potential, it is advisable to develop rapid and specifi c schemes for species diff erentiation of pathogens. We have studied the cultural and biochemical characteristics of Staphylococcus spp. isolated from dogs, cats and cows. In total, 103 halophilic coccal cultures were isolated from companion animals and 45 from cows, of which 55 and 30 cultures were coagulase-positive staphylococci, respectively. The reactions that can be used to diff erentiate S. pseudintermedius and S. aureus were studied. Growth inhibition zones around the disk with polymyxin B antibiotic for S. pseudintermedius were statistically higher (p<0.001) than for S. aureus. The determination of acetone production to diff erentiate between these pathogens has less specifi city, as 30% of S. pseudintermedius showed a false-positive reaction. The belonging of two isolates to the species Staphylococcus pseudintermedius was confi rmed by MALDI-TOF. The virulence of staphylococci is due to the presence of genes that regulate the synthesis of various pathogenicity factors and cause antibiotic resistance. Molecular genetic methods can detect the presence of gene specifi city and help to assess the risk of a particular strain causing infection. Using classical and real-time PCR, the mecA gene was detected in 8 S. aureus strains and 1 S. pseudintermedius strain that showed phenotypic resistance to methicillin. The pathogenicity genes lukF and siet were present in 100%, and the lukS gene in 90% of the studied Staphylococcus pseudintermedius. The study highlights a number of aspects of the diagnosis and diff erentiation of coagulase-positive staphylococci. The possibility of using the Neonatal FAST well D-ONE microculture system for use in veterinary laboratories was also studied. The data obtained can be used to develop methodological approaches to the identifi cation of pathogenic staphylococci using a combination of diff erent methods.