Antimicrobial drug susceptibility and mecA finding in clinical isolates of Staphylococcus spp. from canine pyoderma

Abstract number: P1662

Emanuele M.C., Bosco R., Piraino C., La Giglia M., Bivona M., Vitale M.

Objectives: The susceptibility to selected antimicrobial agents of Staphylococcus spp isolates from dogs affected by recurrent canine pyoderma was tested. The methicillin resistance was also investigated by conventional and molecular methods, since companion animals can act as reservoirs for MRSA/MRSI spreading for human infections.

Methods: 15 strains of Staphylococcus (3 S. aureus and 12 S. intermedius) were tested for their antimicrobial susceptibility by disk diffusion test (DDT) against the following agents: ampicillin (AMP), amoxicillin+clavulanate (AMC), cefotaxime (CTX), clindamycin (CL), enrofloxacin (ENR), eritromycin (E), penicillin (P), tetracycline (TE), vancomycin (VA). Oxacillin (OX) susceptibility was tested by DDT and by microdilution test, according to NCCLS guidelines. The strains were also analyzed for the presence of mecA gene by PCR on DNA extracted from the isolates.

The reference S. aureus strains: ATCC29213 and ATCC43300 were included as controls.

Results: All strains showed resistance to at least three of the antimicrobials tested whereas are susceptible to cefotaxime, enrofloxacin and vancomycin. Frequently the strains exhibited associations and the resistance phenotypes are showed in the table. 5 of them showed eritromycin resistance, in 2 strains together with clindamycin. The mecA gene was found in 3 multiresistant S. intermedius strains and 1 S. aureus, showing heterogeneous characteristics, phenotipically susceptible or with low levels of MIC. Because of the heterogeneous expression of methicillin resistance in Staphylococcus, the finding of mecA phenotipically susceptible strains suggests a repressed mec A expression.

Conclusion: The finding of antibiotic resistance in all the isolates is likely to be due to the selective pressure exerted by previous and repeated antimicrobial treatment since the dogs were affected from recurrent pyoderma. Multiresistant S. intermedius mecA-positive from dog have been reported in Europe and their finding implies the risk of the carriage to human.

Monitoring of antibiotic resistance in animals can elucidate the possible contribution of pet to the spread of staphylococcus methicillin resistant in the community and surveillance activity worldwide contributes to acquire updated epidemiological data.