Indoor airborne dust in veterinary facilities as a reservoir of bacterial pathogens and antimicrobial resistance

Introduction – Airborne dust in veterinary facilities can act as a reservoir for pathogens and contribute to the spread of antimicrobial resistance (AMR). This study examines airborne bacteria and their resistance profiles in veterinary hospitals and clinics. Methods – A total of 179 airborne dust samples were collected from treatment rooms (n = 103) and inpatient wards (n = 76) across 103 veterinary facilities. Total bacterial loads were quantified by direct plate counts and averaged per sample. ESKAPE pathogens, along with Escherichia coli, Salmonella, and Streptococcus, were isolated and assessed for resistance to clinically important antimicrobials, disinfectant minimum inhibitory concentrations (MICs), and plasmid conjugative transfer. Results – Airborne bacterial concentrations varied widely, ranging from 33.37 to 2, 881.82 CFU/m³. High bacterial loads (>1, 000 CFU/m³) were observed in a small proportion of treatment rooms (9.7%) and inpatient wards (9.2%), with mean concentrations of 1, 243.8 CFU/m³ and 1, 550.8 CFU/m³, respectively. Staphylococcus and Enterococcus were the most frequently detected genera (71.8% and 55.3%, respectively), while Acinetobacter predominated among Gram-negative bacteria (37.9%). Airborne isolates resistant to clinically important antimicrobials were isolated, including ciprofloxacin-, ceftazidime-, or colistin-resistant Escherichia coli; vancomycin-resistant Enterococcus spp.; meropenem-, imipenem-, levofloxacin-, or tigecycline-resistant Acinetobacter spp.; and mupirocin- or cefoxitin-resistant Staphylococcus spp. Notably, Acinetobacter isolates demonstrated horizontal transfer of ampicillin- and colistin-resistance-encoding plasmids to E. coli. MIC distributions for triclosan, chlorhexidine, and benzalkonium chloride were narrow, indicating no or limited reduced susceptibility to these disinfectants. Significant associations between disinfectant MICs and AMR were observed (p < 0.05), supporting potential co-selection and cross-resistance. In Enterococcus, these associations were confined to chlorhexidine and correlated with resistance to certain antibiotics. In Enterococcus, these associations were confined to chlorhexidine and correlated with resistance to certain antibiotics. Discussion – Indoor airborne dust in veterinary facilities may serve as a potential reservoir of pathogens, posing risks to animal and human health and underscoring the need for strengthened antimicrobial stewardship, infection control, ventilation, and routine AMR bioaerosol surveillance within a One Health framework.