Differences between Macrolide-Resistant and -Susceptible Streptococcus pyogenes: Importance of Clonal Properties in Addition to Antibiotic Consumption

Abstract

A steady decline in macrolide resistance among Streptococcus pyogenes (group A streptococci [GAS]) in Portugal was reported during 1999 to 2006. This was accompanied by alterations in the prevalence of macrolide resistance phenotypes and in the clonal composition of the population. In order to test whether changes in the macrolide-resistant population reflected the same changing patterns of the overall population, we characterized both macrolide-susceptible and -resistant GAS associated with a diagnosis of tonsillo-pharyngitis recovered in the period from 2000 to 2005 in Portugal. Pulsed-field gel electrophoresis (PFGE) profiling was the best predictor of emm type and the only typing method that could discriminate clones associated with macrolide resistance and susceptibility within each emm type. Six PFGE clusters were significantly associated with macrolide susceptibility: T3-emm3-ST406, T4-emm4-ST39, T1-emm1-ST28, T6-emm6-ST382, B3264-emm89-ST101/ST408, and T2-emm2-ST55. Four PFGE clusters were associated with macrolide resistance: T4-emm4-ST39, T28-emm28-ST52, T12-emm22-ST46, and T1-emm1-ST28. We found no evidence for frequent ongoing horizontal transfer of macrolide resistance determinants. The diversity of the macrolide-resistant population was lower than that of susceptible isolates. The differences found between the two populations suggest that the macrolide-resistant population of GAS has its own dynamics, independent of the behavior of the susceptible population.

Seven-Year Surveillance of emm Types of Pediatric Group A Streptococcal Pharyngitis Isolates in Western Greece

“…In previous reports, a similar correlation was found between macrolide susceptibility and emm 1 [29], [30], emm 3 [28], [30], emm 12 [30], emm 6 [28] and emm 89 [28]. On the other hand, we also established significant association between macrolide resistance and emm 4, emm 22 and emm 77.…”

“…On the other hand, we also established significant association between macrolide resistance and emm 4, emm 22 and emm 77. In previous studies, a similar correlation has been found for emm 4 [28], [30]–[32], emm 22 [28], [29], [31] and emm 77 [29].…”

“…Increased rates of macrolide-resistant GAS, sometimes as high as 35%, followed by a decrease have been also reported in recent studies from other European countries [25], [26]. It has been suggested that this decline may be attributed to decreased macrolide consumption [27] as well as GAS clonal properties [28]. Even though there has been a decrease in the rates of macrolide resistance among GAS isolates, it should be underlined that Greece remains one of the countries with the highest macrolide resistance rates in Europe.…”

“…The frequency of emm 4 was 5.9-fold higher among macrolide-resistant GAS compared to macrolide-susceptible isolates. Increased prevalence of emm 4 has been identified in a recent survey from Ontario, Canada [35] as well as in other pharyngitis surveys [28], [33], [36]. A high frequency of emm 4 among macrolide-resistant GAS isolates, mostly with M phenotype, has been described in Spain (ranked 1 st ) [30], in Italy (2 nd marginally) [31], in Portugal (2 nd ) [28] and in the United States (3 rd ) [34].…”

Extremely Low Prevalence of Erythromycin-Resistant Streptococcus pyogenes Isolates and Their Molecular Characteristics by M Protein Gene and Multilocus Sequence Typing Methods

“…Apart from emm typing, better characterization of the GAS genetic lineages are proposed by the use of multilocus sequence typing (MLST) (11). MLST is a typing method that utilizes nucleotide sequence determination and targets seven neutral house-keeping genes of bacteria.…”