PREVALENCE OF MULTIDRUG-RESISTANT BACTERIA IN THE NASAL CAVITY OF HORSES ASYMPTOMATIC FOR RESPIRATORY DISEASES

The application of antibiotic therapy in animals is mostly performed without orientation, which contributes to increasing microbial resistance. In this scenario, the present study was conducted to examine the prevalence of multidrug-resistant bacteria in the nasal cavity of horses asymptomatic for respiratory diseases. Nasal swab samples were collected from 50 horses asymptomatic for respiratory diseases. The samples were cultivated in Petri dishes containing blood agar and MacConkey agar, where they were incubated under aerobic and microaerophilic conditions at 37 degrees C for 48 h. Pure cultures were subjected to identification for conventional colony-morphological, staining-morphological and biochemical-physiological traits. In addition, in vitro antimicrobial susceptibility was tested and the multidrug resistance index was calculated. Staphylococcus aureus, coagulase-negative Staphylococcus, Streptococcus spp., Micrococcus spp., Enterobacter spp. and Escherichia coli were isolated from the analyzed samples. In terms of antimicrobial resistance, the genus Staphylococcus showed resistance to all of the antibiotics tested, except linezolid; the genus Streptococcus, to beta-lactams, tetracyclines and glycopeptides; Enterobacter, to ss lactams, cephalosporins, monobactam, quinolones, amphenicols, sulfozamides and aminoglycosides (amicacine and tobramycin); and E. coli, to beta-lactams, some cephalosporins, monobactam, quinolones, aminoglycosides, amphenicols, sulfonamides and tetracycline. All analyzed strains exhibited multidrug resistance. In conclusion, healthy horses without respiratory alterations have microorganisms with pathogenic potential in their nasal cavities. Additionally, the high level of microbial resistance is worrying and serves as a warning for the possible indiscriminate use of antibiotics, which can affect animal and human health.