Genetic characterization of methicillin-resistant staphylococcus aureus isolates from human bloodstream infections: detection of MLSB resistance

Vanessa Silva, Sara Hermenegildo, Catarina Ferreira, Célia M. Manaia, Rosa Capita, Carlos Alonso-Calleja, Isabel Carvalho, José Eduardo Pereira, Luis Maltez, José L. Capelo, Gilberto Igrejas, Patrícia Poeta*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)
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Abstract

In this study we aimed to characterize antimicrobial resistance in methicillin-resistant Staphylococcus aureus (MRSA) isolated from bloodstream infections as well as the associated genetic lineages of the isolates. Sixteen MRSA isolates were recovered from bacteremia samples from inpatients between 2016 and 2019. The antimicrobial susceptibility of these isolates was tested by the Kirby–Bauer disk diffusion method against 14 antimicrobial agents. To determine the macrolide–lincosamide–streptogramin B (MLSB) resistance phenotype of the isolates, erythromycin-resistant isolates were assessed by double-disk diffusion (D-test). The resistance and virulence genes were screened by polymerase chain reaction (PCR). All isolates were characterized by multilocus sequence typing (MLST), spa typing, staphylococcal chromosomal cassette mec (SCCmec) typing, and accessory gene regulator (agr) typing. Isolates showed resistance to cefoxitin, penicillin, ciprofloxacin, erythromycin, fusidic acid, clindamycin, and aminoglycosides, confirmed by the presence of the blaZ, ermA, ermC, mphC, msrA/B, aac(6’)-Ie-aph(2”)-Ia, and ant(4’)-Ia genes. Three isolates were Panton–Valentine-leukocidin-positive. Most strains (n = 12) presented an inducible MLSB phenotype. The isolates were ascribed to eight spa-types (t747, t002, t020, t1084, t008, t10682, t18526, and t1370) and four MLSTs (ST22, ST5, ST105, and ST8). Overall, most (n = 12) MRSA isolates had a multidrug-resistance profile with inducible MLSB phenotypes and belonged to epidemic MRSA clones.
Original languageEnglish
Article number375
Pages (from-to)1-9
Number of pages9
JournalAntibiotics
Volume9
Issue number7
DOIs
Publication statusPublished - Jul 2020

Keywords

  • Bacteremia
  • Bloodstream infections
  • EMRSA-15
  • MLS
  • MRSA

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