Occurrence, species distribution, antimicrobial resistance and clonality of methicillin- and erythromycin-resistant staphylococci in the nasal cavity of domestic animals.

The research article investigates the presence, distribution, antibiotic resistance, and clonality of methicillin- and erythromycin-resistant staphylococci in the nasal cavity of domestic animals in Denmark. This study contributes to understanding the link between antibiotic use and the emergence of drug-resistant bacteria in animals.

Objective and Methodology

The study aimed to investigate the presence and varieties of methicillin- and erythromycin-resistant staphylococci in the nasal cavities of domestic animals – dogs, horses, pigs, and cattle in Denmark. The researchers collected nasal swabs from a total of 400 animals belonging to each of these species.

Steps taken in the research included:

• Resistant strains were isolated on selective media
• Identifying the strains through 16S rDNA sequencing
• Typing of the bacteria through pulsed field gel electrophoresis (PFGE)

Findings

The study’s findings revealed several important points:

• Methicillin-resistant coagulase-negative staphylococci (MRCoNS) carrying mecA, a gene-associated with drug resistance, were discovered in horses (50%) and dogs (13%), but not in food animals like pigs and cattle. The species were identified as S. haemolyticus, S. vitulinus, S. sciuri, S. epidermidis and S. warneri.
• The resistance to methicillin in S. vitulinus mediated by mecA gene was described for the first time.
• Methicillin-resistant S. aureus, a type of staphylococci bacterium connected with various infections, wasn’t detected.
• Erythromycin-resistant S. aureus (ERSA) was found in 38% of pigs, indicating a high level of resistance in this species. All isolates carried the erm(C) gene, which is constitutively expressed, indicating that the resistance is always operative.
• A major part of the pigs carrying ERSA originated from a farm with a history of frequent use of macrolides, a group of antibiotics including erythromycin, further linking antibiotic use and resistant bacterial strains.
• Most ERSA isolates had indistinguishable or closely related PFGE patterns, suggesting a clonal distribution within the farm.

Significance

The data analysed in the study shed light on the connection between the use of antimicrobials and the occurrence of MRCoNS in companion animals, and ERSA in food animals. Such understanding is crucial for developing effective antimicrobial resistance (AMR) strategies and practices for animals and human health due to the zoonotic potential of some resistant strains.