Macrolide-resistant Streptococcus pyogenes in Norway: population structure and resistance determinants

An Overview of Macrolide Resistance in Streptococci: Prevalence, Mobile Elements and Dynamics

Streptococcal infections are usually treated with beta-lactam antibiotics, but, in case of allergic patients or reduced antibiotic susceptibility, macrolides and fluoroquinolones are the main alternatives. This work focuses on studying macrolide resistance rates, genetic associated determinants and antibiotic consumption data in Spain, Europe and also on a global scale. Macrolide resistance (MR) determinants, such as ribosomal methylases (erm(B), erm(TR), erm(T)) or active antibiotic efflux pumps and ribosomal protectors (mef(A/E)-mrs(D)), are differently distributed worldwide and associated with different clonal lineages and mobile genetic elements. MR rates vary together depending on clonal dynamics and on antibiotic consumption applying selective pressure. Among Streptococcus, higher MR rates are found in the viridans group, Streptococcus pneumoniae and Streptococcus agalactiae, and lower MR rates are described in Streptococcus pyogenes. When considering different geographic areas, higher resistance rates are usually found in East-Asian countries and milder or lower in the US and Europe. Unfortunately, the availability of data varies also between countries; it is scarce in low- and middle- income countries from Africa and South America. Thus, surveillance studies of macrolide resistance rates and the resistance determinants involved should be promoted to complete global knowledge among macrolide resistance dynamics.

A global snapshot on the prevalent macrolide-resistant emm types of Group A Streptococcus worldwide, their phenotypes and their resistance marker genotypes during the last two decades: A systematic review

Watchful epidemiological surveillance of macrolide-resistant Group A Streptococcus (MRGAS) clones is important owing to the evolutionary and epidemiological dynamic of GAS. Meanwhile, data on the global distribution of MRGAS emm types according to macrolide resistance phenotypes and genotypes are scant and need to be updated. For this, the present systematic review analyses a global set of extensively characterized MRGAS isolates from patients of diverse ages and clinical presentations over approximately two decades (2000 to 2020) and recaps the peculiar epidemiological features of the dominant MRGAS clones. Based on the inclusion and exclusion criteria, 53 articles (3593 macrolide-resistant and 15,951 susceptible isolates) distributed over 23 countries were dissected with a predominance of high-income countries over low-income ones. Although macrolide resistance in GAS is highly variable in different countries, its within-GAS distribution seems not to be random. emm pattern E, 13 major emm types (emm12, 4, 28, 77, 75, 11, 22, 92, 58, 60, 94, 63, 114) and 4 emm clusters (A-C4, E1, E6, and E2) were significantly associated with macrolide resistance. emm patterns A-C and D, 14 major emm types (emm89, 3, 6, 2, 44, 82, 87, 118, 5, 49, 81, 59, 227, 78) and 3 well-defined emm clusters (A-C5, E3, and D4) were significantly associated with macrolide susceptibility. Scrutinizing the tendency of each MRGAS emm type to be significantly associated with specific macrolide resistance phenotype or genotype, interesting vignettes are also unveiled. The 30-valent vaccine covers ~95% of MRGAS isolates. The presented data urge the importance of comprehensive nationwide sustained surveillance of MRGAS circulating clones particularly in Low and Middle income countries where sampling bias is high and GAS epidemiology is obfuscated and needs to be demystified.

emm Types and clusters and macrolide resistance of pediatric group A streptococcal isolates in Central Greece during 2011-2017

Background

The surveillance of emm types and macrolide susceptibility of group A streptococcus (GAS) in various areas and time periods enhances the understanding of the epidemiology of GAS infections and may guide treatment strategies and the formulation of type-specific vaccines. Greece has emerged as a country with high macrolide use. However, studies suggest a gradual reduction in macrolide consumption after 2007.

Methods

During a 7-year period (2011–2017), 604 GAS isolates were recovered from consecutive children presenting with pharyngeal or nonpharyngeal infections in Central Greece; 517 viable isolates underwent molecular analysis, including emm typing.

Results

Isolates belonged to 20 different emm types (in decreasing order of prevalence: 1, 89, 4, 12, 28, 3, 75 and 6, accounting for 88.2% of total isolates). The emm types comprised 10 emm clusters (five most common clusters: E4, A-C3, E1, A-C4 and A-C5). The emm89 isolates were acapsular (‘new clade‘). Overall macrolide resistance rate was 15.4%, and cMLS_B emerged as the predominant resistance phenotype (56.4%). The lowest annual resistance rates occurred in 2014 (13.1%), 2016 (5.5%) and 2017(8.0%) (P for trend = 0.002). Consumption of macrolide/lincosamide/streptogramin B declined by 22.6% during 2011–2017. Macrolide resistance and emm28 and emm77 types were associated (both P<0.001). The most frequently identified genetic lineages of macrolide-resistant GAS included emm28/ST52, emm77/ST63, emm12/ST36, emm89/ST101 and emm4/ST39. We estimated that 98.8% of the isolates belonged to emm types incorporated into a novel 30-valent M protein vaccine.

Conclusions

In Central Greece during 2011–2017, the acapsular emm89 isolates comprised the second most prevalent type. Susceptibility testing and molecular analyses revealed decreasing GAS macrolide resistance rates, which may be attributed to the reduction in the consumption of macrolides and/or the reduced circulation of macrolide-resistant clones in recent years. Such data may provide valuable baseline information in targeting therapeutic intervention and the formulation of type-specific GAS vaccines.

Effect of Tulathromycin on Colonization Resistance, Antimicrobial Resistance, and Virulence of Human Gut Microbiota in Chemostats

To evaluate microbiological safety of tulathromycin on human intestinal bacteria, tulathromycin (0, 0.1, 1, 10, and 100 μg/mL) was added into Chemostats. Before and after drug exposure, we monitored (1) population, SCFA products, antimicrobial resistance, and colonization resistance of gut microbiota, and (2) the antimicrobial resistance genes, transferability, virulent genes, pathogenicity of Enterococus faecalis. Results showed that low level of tulathromycin did not exhibit microbiological hazard on resistance selection and colonization resistance. However, high level of tulathromycin (10 and 100 μg/mL) may disturb colonization resistance of human gut microbiota and select antimicrobial resistant E. faecalis. Most of the selected resistant E. faecalis carried resistant gene of ermB, transferable element of Tn1545 and three virulence genes (esp, cylA, and ace). One of them (E. faecalis 143) was confirmed to have higher horizontal transfer risk and higher pathogenicity. The calculated no observable adverse effect concentration (NOAEC) and microbiological acceptable daily intake (mADI) in our study was 1 μg/mL and 14.66 μg/kg.bw/day, respectively.

Decline in macrolide resistance rates among Streptococcus pyogenes causing pharyngitis in children isolated in Italy

Macrolides are often used to treat group A streptococcus (GAS) infections, but their resistance rates reached high proportions worldwide. The aim of the present study was to give an update on the characteristics and contemporary prevalence of macrolide-resistant pharyngeal GAS in Central Italy. A total of 592 isolates causing pharyngitis in children were collected in the period 2012–2013. Clonality was assessed by emm typing and pulsed-field gel electrophoresis (PFGE) for all macrolide-resistant strains and for selected susceptible isolates. Genetic determinants of resistance were screened by polymerase chain reaction (PCR). Forty-four GAS were erythromycin-resistant (7.4 %). Among them, 52.3 % and 50 % were clindamycin- and tetracycline-resistant, respectively. erm(B)-positive isolates (52.3 %) expressed the constitutive cMLS_B phenotype. mef(A) and its associated M phenotype were recorded in 40.9 % of the cases. The remaining erm(A)-positive isolates expressed the iMLS_B phenotype. Seventeen tetracycline-resistant isolates carried tet(M) and five isolates carried tet(O). Twenty-five emm types were found among all strains, with the predominance of emm types 12, 89, 1, and 4. Eleven emm types and 12 PFGE clusters characterized macrolide-resistant strains, with almost two-thirds belonging to emm12, emm4, and emm11. Macrolide-susceptible and -resistant emm types 12, 89, 11, and 4 shared related PFGE profiles. There was a dramatic decline in macrolide resistance in Central Italy among pharyngeal GAS isolates in 2012–2013 when compared to previous studies from the same region (p < 0.05), although macrolide consumption remained stable over the past 15 years. We observed a decrease in the proportion of macrolide-resistant strains within emm types commonly associated with macrolide resistance in the past, namely emm12, 1, and 89.

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.

Antimicrobial drug use and macrolide-resistant Streptococcus pyogenes, Belgium

In Belgium, decreasing macrolide, lincosamide, streptogramins B, and tetracycline use during 1997–2007 correlated significantly with decreasing macrolide-resistant Streptococcus pyogenes during 1999–2009. Maintaining drug use below a critical threshold corresponded with low-level macrolide-resistant S. pyogenes and an increased number of erm(A)-harboring emm77 S. pyogenes with low fitness costs.

Molecular epidemiology, antimicrobial susceptibilities and resistance mechanisms of Streptococcus pyogenes isolates resistant to erythromycin and tetracycline in Spain (1994-2006)

Background

Group A Streptococcus (GAS) causes human diseases ranging in severity from uncomplicated pharyngitis to life-threatening necrotizing fasciitis and shows high rates of macrolide resistance in several countries. Our goal is to identify antimicrobial resistance in Spanish GAS isolates collected between 1994 and 2006 and to determine the molecular epidemiology (emm/T typing and PFGE) and resistance mechanisms of those resistant to erythromycin and tetracycline.

Results

Two hundred ninety-five out of 898 isolates (32.8%) were erythromycin resistant, with the predominance of emm4T4, emm75T25, and emm28T28, accounting the 67.1% of the 21 emm/T types. Spread of emm4T4, emm75T25 and emm28T28 resistant clones caused high rates of macrolide resistance. The distribution of the phenotypes was M (76.9%), cMLS_B (20.3%), iMLS_B (2.7%) with the involvement of the erythromycin resistance genes mef(A) (89.5%), msr(D) (81.7%), erm(B) (37.3%) and erm(A) (35.9%).

Sixty-one isolates were tetracycline resistant, with the main representation of the emm77T28 among 20 emm/T types. To note, the combination of tet(M) and tet(O) tetracycline resistance genes were similar to tet(M) alone reaching values close to 40%. Resistance to both antibiotics was detected in 19 isolates of 7 emm/T types, being emm11T11 and the cMLS_B phenotype the most frequent ones. erm(B) and tet(M) were present in almost all the strains, while erm(A), mef(A), msr(D) and tet(O) appeared in less than half of them.

Conclusions

Spanish GAS were highly resistant to macrolides meanwhile showed minor resistance rate to tetracycline. A remarkable correlation between antimicrobial resistance and emm/T type was noticed. Clonal spread of emm4T4, emm75T25 and emm28T28 was the main responsable for macrolide resistance where as that emm77T28 clones were it to tetraclycline resistance. A wide variety of macrolide resistance genes were responsible for three macrolide resistance phenotypes.

Phenotypes and genotypes of erythromycin-resistant Streptococcus pyogenes strains isolated from invasive and non-invasive infections from Mexico and the USA during 1999-2010

OBJECTIVE

To compare the prevalence, phenotypes, and genes responsible for erythromycin resistance among Streptococcus pyogenes isolates from Mexico and the USA.

METHODS

Eighty-nine invasive and 378 non-invasive isolates from Mexico, plus 148 invasive, 21 non-invasive, and five unclassified isolates from the USA were studied. Susceptibilities to penicillin, erythromycin, clindamycin, ceftriaxone, and vancomycin were evaluated according to Clinical and Laboratory Standards Institute (CLSI) standards. Phenotypes of erythromycin resistance were identified by triple disk test, and screening for mefA, ermTR, and ermB genes was carried out by PCR.

RESULTS

All isolates were susceptible to penicillin, ceftriaxone, and vancomycin. Erythromycin resistance was found in 4.9% of Mexican strains and 5.2% of USA strains. Phenotypes in Mexican strains were 95% M and 5% cMLS; in strains from the USA, phenotypes were 33.3% iMLS, 33.3% iMLS-D, and 33.3% M. Erythromycin resistance genes in strains from Mexico were mefA (95%) and ermB (5%); USA strains harbored ermTR (56%), mefA (33%), and none (11%). In Mexico, all erythromycin-resistant strains were non-invasive, whereas 89% of strains from the USA were invasive.

CONCLUSIONS

Erythromycin resistance continues to exist at low levels in both Mexico and the USA, although the genetic mechanisms responsible differ between the two nations. These genetic differences may be related to the invasive character of the S. pyogenes isolated.

Description of macrolide-resistant and potential virulent clones of Streptococcus pyogenes causing asymptomatic colonization during 2000-2006 in the Lisbon area

The asymptomatic oropharyngeal colonization rate by Streptococcus pyogenes was 10.7% in children (901 among 8,405 children 0-16 years old) and 3.3% in adults (37 among 1,126 households of children) in the Lisbon area during 2000-2006. Macrolide-resistant S. pyogenes from children (n = 149) was variable with time: 9.8-10.7% in 2000-2002, 28.1% in 2003, 19.6-2.7% in 2004-2005 and 14.6% in 2006. Eight lineages (97.3% of isolates) were identified based on at least 80% similarity of PFGE patterns, T types, emm types and multilocus sequence types (ST). The elevated frequency of macrolide resistance was associated with M phenotype lineages I (emm12/ST36) and V (emm4, emm75/ST39 and a novel emmstMrp6 type) and with one cMLS(B) lineage IV (emm28/ST52) known to be associated with upper respiratory tract and invasive infections. Significant associations (p < 0.05) between emm type/virulence genotype were found, such as emm1/speA (+) ssa (-), emm4/ssa (+) prtF1 (+), emm12/speA (-) ssa (-). The high prevalence (>20%) of speC, prtF1 or ssa was probably caused either by clonal dissemination (speC), or to horizontal gene transfer events (prtF1 and ssa). This report contributes to a better understanding of the molecular epidemiology and evolution of macrolide-resistant S. pyogenes causing symptom-free oropharyngeal colonization. These colonizing strains carry macrolide resistance and virulence genes capable of being transferred to other bacterial species sharing the same niche.

Population biology of Gram-positive pathogens: high-risk clones for dissemination of antibiotic resistance

Infections caused by multiresistant Gram-positive bacteria represent a major health burden in the community as well as in hospitalized patients. Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium are well-known pathogens of hospitalized patients, frequently linked with resistance against multiple antibiotics, compromising effective therapy. Streptococcus pneumoniae and Streptococcus pyogenes are important pathogens in the community and S. aureus has recently emerged as an important community-acquired pathogen. Population genetic studies reveal that recombination prevails as a driving force of genetic diversity in E. faecium, E. faecalis, S. pneumoniae and S. pyogenes, and thus, these species are weakly clonal. Although recombination has a relatively modest role driving the genetic variation of the core genome of S. aureus, the horizontal acquisition of resistance and virulence genes plays a key role in the emergence of new clinically relevant clones in this species. In this review, we discuss the population genetics of E. faecium, E. faecalis, S. pneumoniae, S. pyogenes and S. aureus. Knowledge of the population structure of these pathogens is not only highly relevant for (molecular) epidemiological research but also for identifying the genetic variation that underlies changes in clinical behaviour, to improve our understanding of the pathogenic behaviour of particular clones and to identify novel targets for vaccines or immunotherapy.

Macrolide and tetracycline resistance and emm type distribution of Streptococcus pyogenes isolates recovered from Turkish patients

The aims of this study were to determine the susceptibilities to macrolide and tetracycline antibiotics and emm type distribution of Streptococcus pyogenes strains isolated in the Kocaeli University Hospital, Turkey. A total of 127 S. pyogenes clinical isolates were tested. Eleven (9%) isolates were resistant to erythromycin, and 23 (18%) isolates were resistant to tetracycline. Ten of the erythromycin-resistant isolates were also resistant to tetracycline. By the triple-disk test, all erythromycin-resistant isolates showed the inducible macrolide-lincosamide-streptogramin-C phenotype and harbored erm(TR) gene. tet(O) was the most common tetracycline resistance gene. Among erythromycin-tetracycline coresistant isolates, seven harbored the tet(O) gene. emm 4, emm 1, emm 2,114, and emm 89 were the most common emm types. These isolates were more susceptible to erythromycin. There was considerable emm type heterogeneity in macrolide or tetracycline resistant isolates. According to our knowledge, this is the first study in which emm type distribution is investigated in Turkey. More comprehensive studies are needed to obtain true information about the epidemiology of macrolide and tetracycline resistance and emm type distribution in Turkey.

Streptococcus pyogenes isolates causing severe infections in Norway in 2006 to 2007: emm types, multilocus sequence types, and superantigen profiles

To investigate the epidemiological patterns and genetic characteristics of disease caused by group A Streptococcus (GAS), all available isolates from invasive cases in Norway during 2006 to 2007 (262 isolates) were subjected to antimicrobial susceptibility testing, T serotyping, emm typing, and multilocus sequence typing and screened for known streptococcal pyrogenic exotoxin (Spe) genes, smeZ, and ssa. The average incidence rate was 3.1 cases per 100,000 individuals. The most prevalent sequence types (STs) were STs 52, 28, and 334. In association with emm types 28, 77, and 87, the serotype T-28 comprised 24.8% of the strains. emm types 28, 1, and 82 were dominating. In 2007, a sharp increase in the number of emm-6 strains was noted. All strains were sensitive to penicillin and quinupristin-dalfopristin, while 3.4% and 6.1% of the strains were resistant to macrolides and tetracycline, respectively. Furthermore, the emm-6 strains had intermediate susceptibility to ofloxacin. Isolates displayed a wide variety of gene profiles, as shown by the presence or absence of the Spe genes, smeZ, and ssa, but 48% of the isolates fell into one of three profiles. In most cases, an emm type was restricted to one gene profile. Although the incidence decreased during this study, invasive GAS disease still has a high endemic rate, with involvement of both established and emerging emm types displaying variability in virulence gene profiles as well as differences in gender and age group preferences.

[Surveillance and prevalence of antimicrobial resistance in Norway]

BACKGROUND

Antimicrobial resistance has become increasingly prevalent in clinically important microbes since the 1970s. The global situation affects also Norway. This article reviews the surveillance of antimicrobial resistance in Norway and its results in recent years.

MATERIAL AND METHODS

The article is based on the author's own experience and a non-systematic literature review.

RESULTS

There are three systems for surveillance of antimicrobial resistance in Norway: The Norwegian Surveillance System for Communicable Diseases (MSIS), the Norwegian Surveillance System for Antimicrobial Drug Resistance (NORM), and the European Antimicrobial Resistance Surveillance System (EARSS). Surveillance results and individual studies show that the prevalence of resistance is lower in Norway than in other countries. However, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), penicillin non-susceptible pneumococci and gram-negative enteric bacteria with extended spectrum betalactamases are present within the bacterial population in Norway.

INTERPRETATION

The surveillance systems support each other and are important tools to combat antimicrobial resistance. Continued surveillance, good laboratory diagnostics, prudent antibiotic use and effective infectious disease control are necessary measures to prevent and contain antimicrobial resistance in Norway.

Molecular characterization of invasive and non-invasive Streptococcus pyogenes isolates from Romania

In 2002, the Romanian National Reference Laboratory was invited to join the Strep-EURO project to study invasive Streptococcus pyogenes infections. During 2003 and 2004, a total of 33 isolates recovered from invasive disease were received from eight Romanian counties. For comparison, 102 isolates from non-invasive disease, as well as a collection of 12 old invasive strains (isolated between 1967 and 1980) were included. All isolates were characterized by several methods: T and emm typing, presence of the fibronectin-binding protein F1 gene (prtF1), serum opacity factor (sof), and superantigen (SAg) genes (speA, speB, speC, speF, speG, speH, ssa and smeZ). The recent invasive isolates exhibited 19 emm-types, of which emm1, emm81, emm76, emm49 and emm78 covered 57 % of the strains. Furthermore, multilocus sequence typing analysis revealed nine new sequence types, corresponding to emm types 1, 12, 49, 81, 92, 100, 106 and 119. The non-invasive isolates comprised 24 different emm types with a predominance of emm1 and 12; the old invasive strains were of eight emm types, of which four were unique for this group. All isolates harboured speB and speF; smeZ was detected in all invasive strains, except for the emm49 and emm81 isolates. The majority of isolates from carriers, and patients with pharyngitis were prtF1 positive, most of these (14 strains) being emm12. High tetracycline resistance rates were noted among both invasive and control isolates (54 % and 35 %, respectively), whereas macrolide resistance rates were low (3 % and 5 %, respectively). Active and continuing surveillance is required to provide an accurate assessment of the disease burden and to provide epidemiological data on the character of isolates in Romania.

Boesenbergia pandurata (Roxb.) Schltr., Eleutherine americana Merr. and Rhodomyrtus tomentosa (Aiton) Hassk. as antibiofilm producing and antiquorum sensing in Streptococcus pyogenes

Biofilm formation has been demonstrated as a potentially important mechanism contributing to antibiotic treatment failure on Streptococcus pyogenes. It could play a significant role in recurrent and chronic infections. Boesenbergia pandurata (Roxb.) Schltr., Eleutherine americana Merr. and Rhodomyrtus tomentosa (Aiton) Hassk. have been previously reported from our laboratory as effective agents against S. pyogenes. Therefore, in the present study, we observed the effect of these plants on biofilm formation. The bacterial biofilms were quantified by safranin staining and absorbance at 492 nm. The results clearly demonstrated that all subinhibitory concentrations [1/32-1/2 minimal inhibitory concentration (MIC)] of E. americana (7.81-125 microg mL(-1)) and R. tomentosa (0.24-7.81 microg mL(-1)) extracts significantly prevented biofilm formation while 1/2MIC (7.81 microg mL(-1)) of B. pandurata extract produced this effect. The issue of antiquorum sensing of this pathogenic bacterium has been further explored. A correlation between antiquorum-sensing and antibiofilm-producing activities was demonstrated. Strong inhibition on quorum sensing was displayed with the extract of R. tomentosa. Eleutherine americana extract showed partial inhibition, while B. pandurata did not show this activity. By contrast, an assay of microbial adhesion to hydrocarbon revealed no changes in the cell-surface hydrophobicity of the treated organisms. Active organisms with the ability to inhibit quorum sensing and biofilm formation are worth studying as they may provide complimentary medicine for biofilm-associated infections.

Sequence type and emm type diversity in Streptococcus pyogenes isolates causing invasive disease in Norway between 1988 and 2003

The incidence of invasive group A streptococcal disease has increased in Norway since the 1980s. Analysis of 100 isolates recovered from 1988 to 2003 showed an increased genotypic diversity over time, while the prevalence of the strain that dominated in 1988, sequence type (ST)-28/emm-1, decreased. Necrotizing fasciitis was often associated with ST-15/emm-3.

Topical Retapamulin Ointment, 1%, versus Sodium Fusidate Ointment, 2%, for Impetigo: A Randomized, Observer-Blinded, Noninferiority Study

BACKGROUND

Retapamulin is a novel pleuromutilin antibacterial developed for topical use.

OBJECTIVE

To compare the efficacy and safety of retapamulin ointment, 1% (twice daily for 5 days), with sodium fusidate ointment, 2% (3 times daily for 7 days), in impetigo.

METHODS

A randomized (2:1 retapamulin to sodium fusidate), observer-blinded, noninferiority, phase III study in 519 adult and pediatric (aged > or = 9 months) subjects.

RESULTS

Retapamulin and sodium fusidate had comparable clinical efficacies (per-protocol population: 99.1 and 94.0%, respectively; difference: 5.1%, 95% confidence interval: 1.1-9.0%, p = 0.003; intent-to-treat population: 94.8 and 90.1%, respectively; difference: 4.7%, 95% confidence interval: -0.4 to 9.7%, p = 0.062). Bacteriological efficacies were similar. Success rates in the small numbers of sodium-fusidate-, methicillin- and mupirocin-resistant Staphylococcus aureus were good for retapamulin (9/9, 8/8 and 6/6, respectively). Both drugs were well tolerated.

CONCLUSION

Retapamulin is a highly effective and convenient new treatment option for impetigo, with efficacy against isolates resistant to existing therapies.