Resistance to bacitracin inStreptococcus pyogenesfrom oropharyngeal colonization and noninvasive infections in Portugal was caused by two clones of distinct virulence genotypes

Abstract

During 2000-2007 in Lisbon, we identified 45 bacitracin-resistant Streptococcus pyogenes isolates among 1629 isolates: 24 from oropharyngeal healthy carriers (out of 1026), 21 from patients with noninvasive infections (out of 559) and zero from invasive infections (out of 44). Forty-four of those isolates, mainly of colonization, are low-level bacitracin-resistant members of the cMLS(B)-macrolide-resistant and tetracycline-susceptible emm28/ST52 clone previously detected in Europe, but only among clinical samples. One high-level bacitracin-resistant isolate, associated with a tonsillitis/pharyngitis episode, is cMLS(B)-macrolide-resistant and tetracycline-resistant member of the emm74/ST120 lineage, which was not previously known to include bacitracin-resistant isolates. The bcrABDR operon encoding an ATP-binding cassette transporter in Enterococcus faecalis was not detected among these bacitracin-resistant S. pyogenes strains. Virulence profiling indicated that genes coding for exotoxins and superantigens seem to be clone specific. This study provides an increased knowledge about specific bacitracin-resistant S. pyogenes strains, which may be useful in future investigations aiming to understand the mechanism(s) leading to bacitracin resistance and the cause(s) for differences in colonization and/or dissemination potential.

Description of macrolide-resistant and potential virulent clones of Streptococcus pyogenes causing asymptomatic colonization during 2000–2006 in the Lisbon area

“…The cMLS B phenotype isolates of lineage IV were resistant to bacitracin [14]. cMLS B isolates genetically related to the ones found in our study were already detected, associated with oropharyngeal colonization in China [9], as well as with pharyngitis in Europe [29][30][31][32], and were also described as dominant among invasive isolates in Portugal [25] and other countries [33,34].…”

“…All macrolide-resistant isolates were analyzed for detection of speA and speC genes, encoding streptococcal pyrogenic exotoxins, the ssa gene, encoding a superantigen, and the prtF1 gene, encoding a fibronectin-binding protein [14].…”

“…Chromosomal DNA preparation and digestion with SmaI (New England Biolabs®, Beverly, MA, USA) and Cfr9I (Fermentas, Vilnius, Lithuania) were performed as previously described [14]. The analysis of chromosomal DNA band patterns was first performed by visual inspection, and since the number of DNA fragments was frequently less than 10, a single band difference was used as a criterion to define a different pattern, as suggested [17].…”

Emergence of Ciprofloxacin-Nonsusceptible Streptococcus pyogenes Isolates from Healthy Children and Pediatric Patients in Portugal

“…The relationship among all the ciprofloxacin-nonsusceptible isolates was assessed by pulsed-field gel electrophoresis (PFGE) (20). Detection of emm types was carried out as described at http://www.cdc.gov/ncidod/biotech /strep/strepindex.htm, and representative isolates of different PFGE pattern/emm-type associations (n ϭ 14) were analyzed by multilocus sequence typing (MLST) (http://spyogenes.mlst .net).…”

In Vitro Activities of Retapamulin and 16 Other Antimicrobial Agents against Recently Obtained Streptococcus pyogenes Isolates

“…All bacitracin-resistant isolates belonged to a single multiresistant clone (11) already detected in several countries in Europe and in the United States (7,15). Neomycin had the lowest intrinsic activity of the antibiotics tested.…”