Susceptibility of Streptococcus pyogenes to two macrolides in northern Israel

Susceptibility of Group A Streptococcus to Antimicrobial Agents in Northern Israel: A Surveillance Study

BACKGROUND

Resistant pathogens are an increasing threat affecting millions of people globally. More complicated patients are presented with pathogens harboring new resistance mechanisms, while the pipeline of new antimicrobials hardly proposes solutions. In such a scenario, more severely ill patients remain with no adequate treatment to offer. In addition, massive misuse of antimicrobials, including excessive length of treatment or wrong dosage, also contributes to increasing the rate of pathogens resistance to antimicrobials. Isolation of Streptococcus pyogenes (Group A Streptococcus-GAS) is the main indication for antibiotic treatment to patients diagnosed with acute tonsillitis. Hence, GAS resistance to antibiotics requires periodic monitoring.

OBJECTIVES

To assess susceptibility rates of GAS to penicillin, macrolides, clindamycin, and tetracycline in northern Israel and to compare the findings to the high antimicrobial susceptibility of GAS isolates reported in the same region in 2004 and to other geographical areas.

METHODS

Throat samples from 300 outpatients were collected and cultured at the regional laboratory of Emek Medical Center during September to October 2011.

RESULTS

In 300 samples, the susceptibility rates of GAS to penicillin, erythromycin, azithromycin, clindamycin, and tetracycline in northern Israel still remain very high.

CONCLUSIONS

Continuous control of antimicrobials usage and periodic surveillance of susceptibility rates, together with educational programs and appropriate and targeted treatment protocols, are essential and highly recommended to keep these high susceptibility rates for as long as possible.

Macrolide-resistant Streptococcus pyogenes: prevalence and treatment strategies

Although penicillin remains the first-choice treatment for Streptococcus pyogenes infection, macrolides are important alternatives for allergic patients and lincosamides are recommended together with β-lactams in invasive infections. S. pyogenes may exhibit macrolide resistance because of active efflux (mef genes) or target modification (erm genes), the latter conferring cross resistance to lincosamides and streptogramin B. Worldwide, resistance is restricted to a limited number of genetic lineages, despite resistance genes being encoded on mobile genetic elements. For reasons that are not completely clear, resistance and the associated phenotypes are highly variable across countries. Although resistance remains high in several countries, particularly in Asia, an overall decreasing trend of resistance has been noted in recent years, mostly in Europe. This decrease is not always accompanied by declines in macrolide consumption, suggesting significant roles of other factors in determining the dynamics of macrolide-resistant clones. Continued surveillance is needed to obtain further insights into the forces governing macrolide resistance in S. pyogenes.

Antibiotic resistant beta-hemolytic streptococci

OBJECTIVE

An antibiotic-sensitivity study was conducted on 117 strains of group A streptococcus (GAS), 60 strains of group G streptococcus (GGS) and 20 strains of group C streptococcus (GCS) in order to understand current resistance trends.

METHODS

All strains were tested by the Kirby Bauer disc diffusion method to 15 antibiotics. Resistant strains were confirmed by testing the minimum inhibitory concentration (MIC) of antibiotics by broth dilution technique.

RESULTS

Among GAS, highest resistance was observed to tetracycline (27.4%) and erythromycin (16.2%). The GGS and GCS tested, showed similar resistance patterns.

CONCLUSION

All beta-hemolytic streptococci were susceptible to penicillin, amoxycillin, cephalosporins and linezolid. Resistance to erythromycin, tetracycline, clindamycin, chloramphenicol, and quinolones is emerging.