Molecular characterization of methicillin-resistant Staphylococcus aureus isolates from a tertiary pediatric hospital in southern Brazil

  1. Érika Medeiros dos Santos
  2. Damaris Krul
  3. Thais Muniz Vasconcelos
  4. Adriele Celina Siqueira
  5. Danieli Conte
  6. Ana Paula Oliveira Tomaz
  7. Dany Mesa
  8. Luiza Souza Rodrigues
  9. Libera Dalla-Costa

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Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading  cause of hospital- and community-acquired infections (HA-MRSA and CA-MRSA, respectively). Although this microorganism is associated with childhood bacteremia, its epidemiology and predictive factors are not well established. In this study, the susceptibility profiles and molecular characteristics of 46MRSA isolates obtained from blood samples and other sterile fluids of pediatric patients between January 2017 and May 2022 were characterized. The isolates were identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry. After that, their antimicrobial susceptibility profiles were assessed trough broth microdilution, and their molecular characteristics was performed by whole genome sequencing. Antibiotic susceptibility tests showed that the  isolates were 100% sensitive to vancomycin, linezolid, and sulfamethoxazole-trimethoprim. In terms of SCCmec, types IV and II were the most prevalent, accounting for 47.82% (22/44) and 47.72% (21/44) of the isolates, respectively,  whereas type I was identified in just one isolate (2.27%). Thus, 50% of infections were caused by CA-MRSA and HA-MRSA. Sequencing analysis revealed polyclonal spread, with several sequence types (STs) identified. Five STs belonging to the CC5 clonal complex (ST5, ST105, ST1649, ST1176, and ST1307) accounted for most of the isolates (n=38). The detected virulence genes were sak, tst-1, ACME, hlgA, lukF-PV/lukS-PV, and lukD/lukE. The Panton–Valentine Leukocidin (PVL) toxin gene was found in nine isolates, all of which were CA-MRSA and carried SCCmec type IV. Several antimicrobial resistance genes encoding resistance to different antibiotic classes were identified. In conclusion, we conclude that CA-MRSA strains are currently ubiquitous in hospital environments, causing serious infections, with CC5 being predominant over the past five years.

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  2. Version published to 10.1099/acmi.0.001112.v1 on Access Microbiology