Prevalence and Clonal Characterization of Streptococcus pyogenes Clinical Isolates with Reduced Fluoroquinolone Susceptibility in Spain

Abstract

The aim of this study was to determine the prevalence and characteristics of non-fluoroquinolone (FQ)-susceptible Streptococcus pyogenes isolates and to study their mechanisms of resistance. We performed a prospective prevalence study with 468 isolates collected from 2005 to 2007 and a retrospective study that was based on the examination of existing data collected from 1999 to 2008. The retrospective study included data for isolates with high-level resistance (HR) to ciprofloxacin (MIC > 32 g/ml) (HR isolates) and isolates with the same emm types as those reported in the literature with low-level resistance (LR) to ciprofloxacin (MICs, 2 to 8 g/ml) (LR isolates, n ‫؍‬ 205). Genetic characterization of the isolates was performed by means of emm typing and multilocus sequence typing. The prevalence of LR ranged from 1.9% in 2005 to 30.8% in 2007. This increase was mainly due to the circulation of an emm6 subtype (emm6.4) that represented 77.1% of the LR isolates in 2007. Notably, another emm6 subtype, also detected in 2007 (emm6.37), showed coresistance to 14-and 15-membered macrolides mediated by the mefA gene. Only three HR isolates were detected (isolates emm68.1/ST247/T3,13,B3264, emm77/ST399/T28, and emm28/ST52/T28), and all were identified in the retrospective study. Overall, the 673 isolates represented 25 emm types. All LR isolates were clustered into two emm types: emm6 (six emm6 subtypes) and emm75. All the 156 emm6 isolates had LR, harbored the Ser79/Ala mutation in the parC gene product, and had the same sequence type (ST), ST382. Most (21/33) of the emm75 isolates had LR, showed the Ser79/Phe plus Asp91/Asn double mutation in the parC gene product, and were ST150. The Asp91/Asn mutation by itself did not confer resistance to FQs.

Genome-wide analysis of Streptococcus pyogenes associated with pharyngitis and skin infections. (c2015)

“…These findings were in harmony with the global increase in fluoroquinolone resistance. In Belgium and Spain resistance rates rose from 4.3% and 1.9% to 21.6% and 30.8% respectively, during a span of two to three years (Montes et al, 2010;Van Heirstraeten et al, 2012). However in contrast to these two studies, the sequenced isolates were not limited to a set of emm types.…”

“…Fluoroquinolone resistance is another feature of GAS that has been reported by several studies (Wajima et al, 2008;Yan et al, 2008;Montes et al, 2010). Two types of resistance are observed, a low-level resistance, and a high level resistance which occurs much less frequently (Perez-Trallero et al, 2011).…”

“…Resistance to tetracycline and fluoroquinolones has also been registered with 38% of the strains being resistant to the former globally (Ayer et al, 2007). A significant rise in fluoroquinolone resistance is also being reported in Europe with rates as high as 20% to 30% in some countries (Van Heirstraeten et al, 2007;Montes et al, 2010). Successful treatment faces another major hurdle in cases where identification of the causative organism and diagnosis of the condition are delayed.…”

“…Two types of resistance are observed, a low-level resistance, and a high level resistance which occurs much less frequently (Perez-Trallero et al, 2011). The former is conferred by mutations in the quinolone-resistance-determining region (QRDR) located within the topoisomerase IV, namely the parC and parE genes, while the latter is due to additional mutations in gyrA and gyrB genes of the DNA gyrase (Montes et al, 2010). In our study, all of the isolates showed high-level fluoroquinolone resistance, seen through mutations in the DNA gyrase A and B subunits (gyrA, gyrB) in addition to mutations in the topoisomerase IV B and C subunits (parC and parE).…”

“…Low-level resistance is a result of mutations in a region of the bacterial topoisomerase IV. High-level resistance is caused by an additional mutation in the DNA gyrase genes (Montes et al, 2010). Both mutations can be acquired spontaneously or through horizontal gene transfer.…”