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

doi:10.3390/antibiotics9070375

Genetic Characterization of Methicillin-Resistant Staphylococcus aureus Isolates from Human Bloodstream Infections: Detection of MLS_B Resistance

Antibiotics (Basel). 2020 Jul 3;9(7):375. doi: 10.3390/antibiotics9070375.

Authors

Vanessa Silva^{1

2

3

4}, Sara Hermenegildo^{1

2

3

4}, Catarina Ferreira⁵, Célia M Manaia⁵, Rosa Capita^{6

7}, Carlos Alonso-Calleja^{6

7}, Isabel Carvalho^{1

2

3

4}, José Eduardo Pereira⁸, Luis Maltez⁸, José L Capelo^{9

10}, Gilberto Igrejas^{2

3

4}, Patrícia Poeta^{1

4}

Affiliations

¹ Microbiology and Antibiotic Resistance Team (MicroART), Department of Veterinary Sciences, University of Trás-os-Montes and Alto Douro (UTAD), 5001-801 Vila Real, Portugal.
² Department of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro (UTAD), 5001-801 Vila Real, Portugal.
³ Functional Genomics and Proteomics Unit, University of Trás-os-Montes and Alto Douro (UTAD), 5001-801 Vila Real, Portugal.
⁴ Associate Laboratory for Green Chemistry-LAQV, Chemistry Department, Faculty of Science and Technology, University Nova of Lisbon, 2829-516 Lisbon, Portugal.
⁵ CBQF-Centro de Biotecnologia e Química Fina-Laboratório Associado, Universidade Católica Portuguesa, Escola Superior de Biotecnologia, 4169-005 Porto, Portugal.
⁶ Department of Food Hygiene and Technology, Veterinary Faculty, University of León, 24071 León, Spain.
⁷ Institute of Food Science and Technology, University of León, 24071 León, Spain.
⁸ Veterinary and Animal Science Research Center (CECAV), University of Trás-os-Montes and Alto Douro (UTAD), 5001-801 Vila Real, Portugal.
⁹ BIOSCOPE Group, LAQV@REQUIMTE, Chemistry Department, Faculty of Science and Technology, NOVA University of Lisbon, 1349-008 Almada, Portugal.
¹⁰ Proteomass Scientific Society, 2825-466 Costa de Caparica, Portugal.

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 (MLS_B) 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 MLS_B 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 MLS_B phenotypes and belonged to epidemic MRSA clones.

Keywords: EMRSA-15; MLSB; MRSA; bacteremia; bloodstream infections.