Persistence of multidrug-resistant Staphylococcus haemolyticus in an animal veterinary teaching hospital clinic

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance
• Molecular Epidemiology

Background:

• Coagulase-negative staphylococci (CNS) are increasingly recognized as nosocomial pathogens, exhibiting resistance to antibiotics and disinfectants.
• Multidrug-resistant CNS are prevalent in human hospitals, but their occurrence and persistence in veterinary settings remain understudied.
• Understanding the environmental reservoirs and transmission dynamics of resistant bacteria in animal clinics is crucial for public health.

Purpose of the Study:

• To investigate the presence and persistence of multidrug-resistant CNS in the environment of a small animal clinic.
• To characterize the genetic basis and epidemiological relatedness of multidrug-resistant Staphylococcus haemolyticus isolates found in the clinic.

Main Methods:

• Environmental sampling within a small animal clinic over a three-year period.
• Isolation and identification of bacterial species, focusing on Staphylococcus haemolyticus.
• Molecular techniques including pulsed-field electrophoresis, multilocus enzyme typing, and genotypic characterization of resistance genes (e.g., mecA, blaZ, qacA/B, tetK, ermB, cat, aacA-aphD).
• Plasmid analysis and investigation of gene integration mechanisms (e.g., IS257).

Main Results:

• Multidrug-resistant Staphylococcus haemolyticus was isolated from cage floors and a cat's wound infection, indicating persistence over three years.
• All isolates belonged to a single epidemiological clone and harbored a chromosomal mecA gene and a plasmid with blaZ and qacA/B.
• Multiple small plasmids (<5 kb) conferred resistance to tetracycline (tetK), macrolides (ermB), and chloramphenicol (cat); one isolate also had gentamicin resistance (aacA-aphD).
• IS257-mediated integration of the tetK plasmid into the chromosome was observed in a macrolide- and chloramphenicol-susceptible isolate, demonstrating gene mobility.

Conclusions:

• Multidrug-resistant Staphylococcus haemolyticus can persist in animal clinic environments, posing a potential risk.
• The study demonstrates significant intracellular mobility of bacterial resistance genes, facilitated by insertion sequences like IS257.
• Findings underscore the importance of monitoring antimicrobial resistance in veterinary settings and understanding the evolution of resistance determinants.