F2F Poster 21st Lancefield International Symposium for Streptococci and Streptococcal Diseases 2022

Macrolide-resistance determinants characterization in Streptococcus pyogenes in Barcelona, Spain (2019-2020) (#307)

Dàmaris Berbel Palau 1 2 , Aina Pagès Lara 3 , Jordi Càmara Mas 1 2 , Aida González Díaz 1 2 , Guillem López de Egea 1 2 , Sara Martí Martí 1 2 , Fe Tubau Quintano 1 2 , M. Angeles Domínguez Luzón 1 4 , Carmen Ardanuy Tisaire 1 4
  1. Microbiology Department, Hospital Universitari de Bellvitge, IDIBELL, L'Hospitalet de Llobregat, Barcelona, Spain
  2. CIBER de Enfermedades Respiratorias, ISCIII, Madrid, Spain
  3. Universitat Pompeu Fabra, Barcelona, Spain
  4. Departament of Pathology and Experimental Therapeutics, University of Barcelona., Barcelona, Spain

Background:

Macrolides are used for Streptoccoccus pyogenes (Group A Streptococcus, GAS) infections treatment in case of β-lactam allergy. Macrolide resistance (MR) is mainly mediated by methylases [erm(B) and erm(TR)] and efflux pumps [mef(A)]. These genes located into different genetic elements, mainly transposons of the Tn916-family.

Methods:

All GAS clinical isolates collected from adults from 2019 to 2020 were included. The antibiotic susceptibility was studied by microdilution and disk-diffusion methods. MR isolates were typed by emm-typing and pulsed-field gel electrophoresis (PFGE). MR-genes [mef(A), erm(B), and erm(TR)] were detected by PCR. Putative mobile genetic elements (MGE) were determined using linkage experiments and PCR detection of Tn916-family related genes.

Results:

The overall MR rate was 13.6% (35/267), from these MR GAS 20 (57.14%) had cMLSB phenotype (macrolide, lincosamides and streptogramins group B resistant, constitutively expressed), 9 (25.71%) iMLSB (expression induced) and 6 (17.14%) with an M (only macrolide-resistance) phenotype. Seventeen different emm-types were identified, among which the most frequent were emm11 (n=5), emm77 (n=4), emm81 (n=4), emm75 (n=3), emm94 (n=3), emm169 (n=3), emm9 (n=2) and emm219 (n=2) which accounted for 74.29% of all MR-GAS isolates. MR-GAS emm11 isolates harboured erm(B) encoded into transposons of Tn916-family, emm77 was only associated to erm(TR) and tet(O) and emm81 isolates contained mef(A/E).

Conclusions:

Macrolide resistance rates remained stable between 2019-2020 regarding  previous periods in our area. Macrolide-resistance determinants were associated to both classical transposons but also, we have obtained results suggesting the spread of no previously described elements.