Genetic characterization of Staphylococcus aureus isolated from Norway rats in Boston, Massachusetts

• Published in: Veterinary medicine and science 2023-01, Vol.9 (1), p.272-281
• Main Authors: Gerbig, Gracen R., Piontkivska, Helen, Smith, Tara C., White, Ruairi, Mukherjee, Jean, Benson, Hayley, Rosenbaum, Marieke, Leibler, Jessica H.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Wild; Anti-Bacterial Agents - pharmacology; Antibiotic resistance; Antibiotics; Bacterial infections; Boston; Domestic animals; Drug resistance; Erythromycin; Genes; Genetic relationship; Genomes; Genomics; Glycerol; Homeless people; Humans; Laboratories; Methicillin; Methicillin-Resistant Staphylococcus aureus - genetics; Original; Pathogens; Penicillin; Phylogeny; Public health; Rats; Rattus norvegicus; RODENTS; Staphylococcal Infections - epidemiology; Staphylococcal Infections - microbiology; Staphylococcal Infections - veterinary; Staphylococcus aureus; Staphylococcus aureus - genetics; Staphylococcus infections; urban health; Virulence; wild rodent; zoonoses
• ISSN: 2053-1095; 2053-1095
• DOI: 10.1002/vms3.1020

Background Despite the importance of domesticated animals in the generation and transmission of antibiotic‐resistant Staphylococcus aureus, the role of wild animals, specifically rodents, in the ecology of S. aureus remains unclear. We recovered and genotyped S. aureus isolates from wild Norway rats (Rattus norvegicus) in Boston, Massachusetts to examine genetic relationships between common human and animal S. aureus isolates in a large US metropolitan area. Methods We collected and necropsied 63 rats from June 2016 to June 2017. Nasal, foot pad, fur, and fecal swabs were collected. Staphylococcus aureus was isolated using culture‐based methods and polymerase chain reaction confirmation. S. aureus isolates were spa typed, tested for antibiotic susceptibility, and whole genome sequenced. Assembled sequences were uploaded to the Comprehensive Antibiotic Resistance Database to identify antibiotic resistance elements. A phylogenetic tree was constructed using the neighbor‐joining method with the maximum composite likelihood distance in MEGA7. Results We recovered 164 Gram‐positive bacterial isolates from Norway rats. Nineteen isolates from eight individual rats were confirmed as S. aureus (prevalence: 12.9% (8/63)). All S. aureus isolates were methicillin‐susceptible S. aureus (MSSA), pvl‐negative, and resistant to penicillin. Two isolates displayed resistance to erythromycin. Four different S. aureus spa types were detected (t933, t10751, t18202, and t189). Thirteen unique antibiotic resistance elements were identified, and all isolates shared genes mepR, mgrA, arlR, and S. aureus norA. Phylogenetic analysis if the 19 S. aureus isolates revealed they were genetically similar to four clades of S. aureus with similar resistance gene profiles isolated from both human‐ and animal‐derived S. aureus, as well as formed a distinct phylogenetic cluster composed only of rat isolates. Conclusions Wild rodents may serve as a reservoir or vector of antibiotic resistance genes in the urban environment with relevance for human and animal health. We identified S. aureus among wild rodents in Boston, MA with antimicrobial resistance genes. Our findings indicate that wild rodents may serve as a under‐studied reservoir of S. aureus and antimicrobial resistance genes with relevance for human exposure and human health.