Characterization of levofloxacin non-susceptible clinical Streptococcus pyogenes isolated in the central part of Italy

Abstract

We investigated the prevalence, genetics, and clonality of fluoroquinolone non-susceptible isolates of Streptococcus pyogenes in the central part of Italy. S. pyogenes strains (n = 197) were isolated during 2012 from patients with tonsillopharyngitis, skin, wound or invasive infections and screened for fluoroquinolone non-susceptibility (resistance to norfloxacin and levofloxacin minimum inhibitory concentration (MIC) = 2 mg/L) following EUCAST guidelines. First-step topoisomerase parC and gyrA substitutions were investigated using sequencing analysis. Clonality was determined by pulsed field gel electrophoresis (PFGE; SmaI digestion) and by emm typing. The fluoroquinolone non-susceptible phenotype was identified in 18 isolates (9.1 %) and correlated with mutations in parC, but not in gyrA, the most frequent leading to substitution of the serine at position 79 with an alanine. Most of the fluoroquinolone non-susceptible isolates belonged to the emm-type 6, even if other emm-types were also represented (emm75, emm89, and emm2). A significant level of association was measured between PFGE and both emm type and substitutions in parC. The prevalence of fluoroquinolone non-susceptible Streptococcus pyogenes isolates in Italy is of concern and, although the well-known emm type 6 is dominant, other types are appearing and spreading.

Changes in Macrolide Resistance Among Group A Streptococci in Serbia and Clonal Evolution of Resistant Isolates

“…Data from the literature show that fluoroquinolone nonsusceptibility among GASs is increasing not only across Europe, especially in Spain and Belgium, but also in other countries and is frequently related to the spread of emm6. [31][32][33] This type was not found in the present study probably due to its rare association with macrolide resistance. 32,34 On the other hand, the presence of fluoroquinolone resistance among emm75 and emm12 as observed here was also documented in other countries.…”

“…32,34 On the other hand, the presence of fluoroquinolone resistance among emm75 and emm12 as observed here was also documented in other countries. [31][32][33] PFGE characterization of MRGAS isolates revealed the strong association between emm type, resistance determinants, and particular PFGE clusters, indicating high genetic homogeneity of strains belonging to a certain emm type and sharing the same resistance determinant. The predominant MRGAS clone circulating in Serbia was emm75/mefA with PFGE cluster E (n = 28).…”

Identification and Characterization of Fluoroquinolone Non-susceptible Streptococcus pyogenes Clones Harboring Tetracycline and Macrolide Resistance in Shanghai, China

“…In China, consumption of FQs increased by up to 2 × 10 8 standard units during 2001–2010, becoming the third most consumed antibiotic in the adult population (Van Boeckel et al, 2014 ). Increasing frequencies of S. pyogenes isolates with reduced susceptibility to FQs have been observed in many countries (Reinert et al, 2004 ; Malhotra-Kumar et al, 2005 ; Smeesters et al, 2009 ; Montes et al, 2010 ; Pires et al, 2010 ; Van Heirstraeten et al, 2012 ; Petrelli et al, 2014 ), yet data on FQ-non-susceptible S. pyogenes in China remain scarce despite extremely high resistance to primary interventions such as macrolides.…”