Rapid Inversion of the Prevalences of Macrolide Resistance Phenotypes Paralleled by a Diversification of T and emm Types among Streptococcus pyogenes in Portugal

Abstract

In Portugal erythromycin resistance of 26.6% (n ‫؍‬ 352) remained constant during 1998 to 2003, however in 1998 the MLS B phenotype dominated (85%), whereas in 2003 the M phenotype prevailed (77%). A decline in T12/emm22 MLS B isolates could partially explain the drop in this phenotype, but the rise of the M phenotype was not due to clonal expansion.Although penicillin remains the antibiotic of choice in the treatment of Lancefield group A streptococci (GAS) infections, macrolides and lincosamides are recommended as suitable alternatives for patients allergic to penicillin (5). Newer macrolides, such as azithromycin, may be given once a day, making this an attractive option for the treatment of pharyngitis due to Streptococcus pyogenes. In Portugal, where penicillin V is not available, macrolides and lincosamides have the additional advantage of being a therapeutic option with an oral route of administration. High macrolide resistance in GAS was previously identified in Portugal (13) in line with other European countries (1, 4, 6) but in contrast to others (14,16). The aims of this study were to determine the prevalence of macrolide resistance phenotypes and its temporal trends and to evaluate the correlation with T and emm-types.A total of 1,321 GAS from clinical infections were collected from 30 laboratories, geographically distributed throughout Portugal, from January 1998 to December 2003. The isolates were distributed in the study period as follows: 153 in 1998, 240 in 1999, 213 in 2000, 216 in 2001, 270 in 2002, and 229 in 2003. The laboratories were asked to submit all nonduplicate GAS isolated from outpatients during the study period. Antimicrobial susceptibility testing, T-typing, and macrolide resistance phenotype and genotype were determined as previously described (7, 13). Strains were emm typed according to the recommendations of the Centers for Disease Control and Prevention (CDC) (http://www.cdc.gov/ncidod/biotech/strep/protocols .htm). The sequences of representatives of each restriction profile were searched against GenBank as well as the emm CDC database (http://www.cdc.gov/ncidod/biotech/strep /strepindex.htm). An isolate was considered to be of a given emm type if it had Ͼ95% identity over the 160 bases considered (3).Among this collection, 352 isolates (26.6%) were erythromycin resistant. Although there was a higher prevalence of resistant isolates recovered in 1998 (34.6%), the variation of the overall prevalence in the following years (19.6% in 1999, 27.7% in 2000, 25.5% in 2001, 23.7% in 2002, and 20.5% in 2003) was not significant ( 2 test, P ϭ 0.22) (Fig. 1). Only the 325 erythromycin-resistant isolates recovered from throat swabs associated with a diagnosis of pharyngitis were characterized further.Resistance to tetracycline was expressed by 38.7% (n ϭ 126) of the isolates (MIC 90 ϭ 96 g/ml, MIC range, 12 to 512 g/ml). The distribution of tetracycline-resistant isolates among the study years was as follows: 84.9% of the isolates recovered in 1998, 70.2% in 1999, 28.8% in 2000, 30.9...

Macrolide and Tetracycline Resistance andemmType Distribution ofStreptococcus pyogenesIsolates Recovered from Turkish Patients

“…In this study, erythromycin resistance rate (9%) was lower compared with that in many countries (21.3%-45%). 8,29,33,39 Low erythromycin resistance rates (0.6%-6.8%) were reported in some countries. 14,15,21,23,25,28,30,37 Our erythromycin resistance rate was similar to rates in the United States (9.6%), 19 Germany (12.7%), 4 and Greece 280 DUNDAR ET AL.…”

Illustration of a Common Framework for Relating Multiple Typing Methods by Application to Macrolide-Resistant Streptococcus pyogenes

“…Results of antimicrobial susceptibility testing, T typing, macrolide-resistant phenotyping and genotyping, and emm typing were reported previously (29). Eleven T types were identified (1, 2, 4, 5/27/44, 6, 9, 12, 13, 25, 28, and B3264).…”

Disease Manifestations and Pathogenic Mechanisms of Group A Streptococcus

“…However, in this case, high rates of macrolide resistance were due to the emergence of a resistant emm 12 clone. Variations in clonal prevalence can lead to significant temporal variations in the rates of macrolide resistance among GAS strains (111,496,508).…”