High macrolide resistance in Streptococcus pyogenes strains isolated from children with pharyngitis in China

Success of susceptibility-guided eradication of Helicobacter pylori in a region with high secondary clarithromycin and levofloxacin resistance rates

BACKGROUND

Resistance to clarithromycin (CLA) and levofloxacin (LFX) of Helicobacter pylori (H. pylori) is increasing in severity, and successful eradication is essential. Presently, the eradication success rate has greatly declined, leaving a large number of patients with previous treatment histories.

AIM

To investigate secondary resistance rates, explore risk factors for antibiotic resistance, and assess the efficacy of susceptibility-guided therapy.

METHODS

We recruited 154 subjects positive for Urea Breath Test who attended The First Affiliated Hospital of China Medical University between July 2022 and April 2023. Participants underwent a string test after an overnight fast. The gastric juice was obtained and transferred to vials containing storage solution. Subsequently, DNA extraction and the specific DNA amplification were performed using quantitative polymerase chain reaction (qPCR). Demographic information was also analyzed as part of the study. Based on these results, the participants were administered susceptibility-guided treatment. Efficacy was compared with that of the empiric treatment group.

RESULTS

A total of 132 individuals tested positive for the H. pylori ureA gene by qPCR technique. CLA resistance rate reached a high level of 82.6% (n = 109), LFX resistance rate was 69.7% (n = 92) and dual resistance was 62.1% (n = 82). Gastric symptoms [odds ratio (OR) = 2.782; 95% confidence interval (95%CI): 1.076-7.194; P = 0.035] and rural residence (OR = 5.152; 95%CI: 1.407-18.861; P = 0.013) were independent risk factors for secondary resistance to CLA and LFX, respectively. A total of 102 and 100 individuals received susceptibility-guided therapies and empiric treatment, respectively. The antibiotic susceptibility-guided treatment and empiric treatment groups achieved successful eradication rates of 75.5% (77/102) and 59.0% (59/411) by the intention-to-treat (ITT) analysis and 90.6% (77/85) and 70.2% (59/84) by the per-protocol (PP) analysis, respectively. The eradication rates of these two treatment strategies were significantly different in both ITT (P = 0.001) and PP (P = 0.012) analyses.

CONCLUSION

H. pylori presented high secondary resistance rates to CLA and LFX. For patients with previous treatment failures, treatments should be guided by antibiotic susceptibility tests or regional antibiotic resistance profile.

Severe problem of macrolides resistance to common pathogens in China

With the widespread use of macrolide antibiotics in China, common pathogens causing children's infections, such as Streptococcus pneumoniae, Streptococcus (including Group A streptococcus, Group B streptococcus), Staphylococcus aureus, Bordetella pertussis, and Mycoplasma pneumoniae, have shown varying degrees of drug resistance. In order to provide such problem and related evidence for rational use of antibiotics in clinic, we reviewed the drug resistance of common bacteria to macrolides in children recent 20 years.

Molecular characterization of Streptococcus pneumoniae isolated from pediatric patients in Shanghai, China

BACKGROUND

Streptococcus pneumoniae is a major cause of bacterial infection among infants and young children with high morbidity and mortality. The serotype distribution of S. pneumoniae varies with geography, time, age, and disease.

AIM

We aimed to investigate the current status of molecular characteristics of S. pneumoniae strains isolated from pediatric patients in Shanghai, China.

METHODS

Between 2016 and 2018, 73 clinical S. pneumoniae isolates were characterized by capsular serotype, multilocus sequence typing, antibiotic susceptibility, and resistant genes.

RESULTS

The most common serotypes were 19F (39.7%), 19A (16.4%), 6A (11.0%), 14 (9.6%), and 6B (8.2%). The coverage rates of the 7-, 10- and 13-valent pneumococcal conjugate vaccines were 64.4%, 64.4%, and 91.8%, respectively. The five predominant sequence types were ST271 (37.0%), ST320 (19.2%), ST3173 (11.0%), ST876 (6.8%), and ST81 (4.1%), which were mainly associated with serotypes 19F, 19A, 6A, 14, and 23F, respectively. The rates of resistance to penicillin and ceftriaxone were 21.9% and 39.7%, respectively. All strains displayed resistance to macrolides, 54.8% of which possessed both erm(B) and mef(A/E) genes, and 41.1% carried the erm(B) gene alone. Tn2010 (41.1%) was the most common transposon.

CONCLUSIONS

Clonal complex 271 (Taiwan19F-14 clone) played a dominant role in the dissemination of pneumococcal isolates. The prevalent serotypes indicated a lack of the 7-valent pneumococcal conjugate vaccine, which has not been included in national immunization programs in mainland China. The high rate of macrolide resistance made the empirical use of macrolides alone not suitable for treating pediatric pneumococcal disease.

Changes in epidemiologic characteristics and antimicrobial resistance of Streptococcus pyogenes isolated over 10 years from Japanese children with pharyngotonsillitis

Introduction. Pharyngotonsillitis caused by Streptococcus pyogenes (group A streptococci, or GAS) is among the most common infections treated with antibiotics in pediatric patients.Aim. This study aimed to analyse changes in molecular epidemiology and antibiotic susceptibility among GAS isolates in three study periods spanning 10 years.Methodology. GAS isolated from paediatric patients with pharyngotonsillitis during Period I (mid-2007 to 2008, n=235), Period II (2012, n=210), and Period III (2018, n=189) were analysed for emm type, multilocus sequence type (MLST), antibiotic susceptibility, and macrolide (ML)- and quinolone (QL)-resistance genes.Results. Over 20 % of isolates represented emm1 and emm12 types, remaining common in all three periods. Among other emm types, emm4 was common in Period I, emm28 and emm89 in Period II, and emm3 and emm89 in Period III. All isolates remained highly susceptible to penicillins and cephalosporins. Isolates possessing mefA, ermA, or ermB genes mediating ML resistance increased from 34.9 % in Period I to 60.9 % in Period II, but fell to 27.5 % in Period III. QL-resistant isolates with amino acid substitutions affecting ParC and/or GyrA gradually increased from 11.5 to 14.3 %. Specific sequence types identified by MLST and emm typing were associated closely with ML or QL resistance.Conclusion. Our findings indicate that even in ambulatory care, antibiotic choice for these infections should be based on rapid identification and characterization of causative pathogens.

Clinical And Bacteriological Impact Of Clarithromycin In Streptococcal Pharyngitis: Findings From A Meta-Analysis Of Clinical Trials

Introduction

Among the bacterial upper respiratory tract infections (UTRIs), the most medically significant is pharyngitis due to Group A beta-hemolytic Streptococci (GABHS). A 2012 meta-review and a 2016 Cochrane systematic review reported favorably on the comparative efficacy and safety of clarithromycin in pediatric patients with URTIs and in adults with GABHS pharyngitis. In this paper, the evidence base for clarithromycin in patients with URTIs is augmented by a meta-analysis of comparative studies in GABHS pharyngitis.

Methods

A series of five outpatient trials of clarithromycin for the treatment of streptococcal pharyngitis from an internal database were subjected to meta-analysis. Active comparators comprised penicillin VK and erythromycin.

Results

Rates of clinical cure or improvement were very similar in all treatment assignments, but the rates of bacteriological cure were numerically higher with clarithromycin than with comparator antibiotics. Adverse events data indicated that clarithromycin was generally well tolerated in these studies, with a relatively low incidence of adverse events and few severe incidents.

Discussion

Though currently not advised as a first-line therapy for URTI in most guidelines, the results of the meta-analysis indicate that clarithromycin is nevertheless a valid, effective and largely well-tolerated treatment option for GABHS pharyngitis patients who cannot benefit from other agents.

Genome analysis of a multidrug-resistant Streptococcus sanguis isolated from a throat swab of a child with scarlet fever

OBJECTIVES

A multidrug-resistant strain of the opportunistic pathogen Streptococcus sanguis (S28) was isolated from a throat swab of a child with scarlet fever as a rare case. Genome sequencing and analysis of strain S28 were performed to gain a better understanding of the multidrug resistance mechanisms of S. sanguis and its relationship with scarlet fever.

METHODS

The genome of S. sanguis S28 was sequenced on a Illumina HiSeq platform. Genome assembly was conducted using SOAPdenovo v.2.04 and the assembled genome sequence was submitted to NCBI for annotation.

RESULTS

The 1 268 358 696bp genome of S. sanguis S28 contains 2287 coding sequences (CDS) with a GC content of 43.2%. Strain S28 possesses four antimicrobial resistance genes (ARGs), which is consistent with phenotypic analysis. A novel transposon with three genes conferring resistance to macrolide-lincosamide-streptogramin B (MLS_B) antibiotics, tetracyclines and aminoglycosides was discovered.

CONCLUSION

To our knowledge, this is the first report of a S. sanguis genome isolated from a throat swab of a child with scarlet fever and the first report of a transposon with three activated ARGs conferring resistance to MLS_B, tetracyclines and aminoglycosides together.

Intracellular Streptococcal Uptake and Persistence: A Potential Cause of Erysipelas Recurrence

Erysipelas is a severe streptococcal infection of the skin primarily spreading through the lymphatic vessels. Penicillin is the treatment of choice. The most common complication consists in relapses which occur in up to 40% or more of patients despite appropriate antibiotic treatment. They cause lymphatic damage resulting in irreversible lymphedema and ultimately elephantiasis nostras and lead to major health restrictions and high socio-medical costs. Prevention of relapses is an unmet need, because even long-term prophylactic penicillin application does eventually not reduce the risk of recurrence. In this article we assess risk factors and causes of erysipelas recurrence. A systematic literature search for clinical studies addressing potential causes and measures for prevention of erysipelas recurrence was combined with a review of experimental and clinical data assessing the ability and clinical relevance of streptococci for intracellular uptake and persistence. The literature review found that venous insufficiency, lymphedema, and intertrigo from fungal infections are considered to be major risk factors for recurrence of erysipelas but cannot adequately explain the high recurrence rate. As hitherto unrecognized likely cause of erysipelas relapses we identify the ability of streptococci for intracellular uptake into and persistence within epithelial and endothelial cells and macrophages. This creates intracellular streptococcal reservoirs out of reach of penicillins which do not reach sufficient bactericidal intracellular concentrations. Incomplete streptococcal elimination due to intracellular streptococcal persistence has been observed in various deep tissue infections and is considered as cause of relapsing streptococcal pharyngitis despite proper antibiotic treatment. It may also serves as endogenous infectious source of erysipelas relapses. We conclude that the current antibiotic treatment strategies and elimination of conventional risk factors employed in erysipelas management are insufficient to prevent erysipelas recurrence. The reactivation of streptococcal infection from intracellular reservoirs represents a plausible explanation for the frequent occurrence erysipelas relapses. Prevention of erysipelas relapses therefore demands for novel antibiotic strategies capable of eradicating intracellular streptococcal persistence.

Increasing Resistance to Azithromycin in Neisseria gonorrhoeae in Eastern Chinese Cities: Resistance Mechanisms and Genetic Diversity among Isolates from Nanjing

Azithromycin resistance (AZM-R) of Neisseria gonorrhoeae is emerging as a clinical and public health challenge. We determined molecular characteristics of recent AZM-R Nanjing gonococcal isolates and tracked the emergence of AZM-R isolates in eastern Chinese cities in recent years. A total of 384 N. gonorrhoeae isolates from Nanjing collected from 2013 to 2014 were tested for susceptibility to AZM and six additional antibiotics; all AZM-R strains were characterized genetically for resistance determinants by sequencing and were genotyped using N. gonorrhoeae multiantigen sequence typing (NG-MAST). Among the 384 isolates, 124 (32.3%) were AZM-R. High-level resistance (MIC, ≥256 mg/liter) was present in 10.4% (40/384) of isolates, all of which possessed the A2143G mutation in all four 23S rRNA alleles. Low- to mid-level resistance (MIC, 1 to 64 mg/liter) was present in 21.9% (84/384) of isolates, 59.5% of which possessed the C2599T mutation in all four 23S rRNA alleles. The 124 AZM-R isolates were distributed in 71 different NG-MAST sequence types (STs). ST1866 was the most prevalent type in high-level AZM-R (HL-AZM-R) isolates (45% [18/40]). This study, together with previous reports, revealed that the prevalence of AZM-R in N. gonorrhoeae isolates in certain eastern Chinese cities has risen >4-fold (7% to 32%) from 2008 to 2014. The principal mechanisms of AZM resistance in recent Nanjing isolates were A2143G mutations (high-level resistance) and C2599T mutations (low- to mid-level resistance) in the 23S rRNA alleles. Characterization of NG-MAST STs and phylogenetic analysis indicated the genetic diversity of N. gonorrhoeae in Nanjing; however, ST1866 was the dominant genotype associated with HL-AZM-R isolates.

Throat Carriage Rate and Antimicrobial Resistance of Streptococcus pyogenes In Rural Children in Argentina

OBJECTIVES

The aim of this study was to determine the prevalence of asymptomatic carriers of group A β-hemolytic streptococci (GAS) in children living in a rural community and to investigate the association between episodes of acute pharyngitis and carrier status.

METHODS

Throat swabs were collected from September to November 2013 among children 5-13 years of age from a rural community (Maria Ignacia-Vela, Argentina). The phenotypic characterization of isolates was performed by conventional tests. Antimicrobial susceptibility was assayed for penicillin, tetracycline, chloramphenicol, erythromycin, and clindamycin (disk diffusion). The minimum inhibitory concentration was determined for penicillin, cefotaxime, tetracycline, and erythromycin.

RESULTS

The carriage of β-hemolytic streptococci was detected in 18.1% of participants, with Streptococcus pyogenes in 18 participants followed by S. dysgalactiae ssp. equisimilis in 5. The highest proportion of GAS was found in 8 to 10-year-old children. No significant association between the number of episodes of acute pharyngitis suffered in the last year and the carrier state was detected (p>0.05). Tetracycline resistance (55.5%) and macrolide-resistant phenotypes (11.1%) were observed. Resistance to penicillin, cefotaxime, or chloramphenicol was not expressed in any streptococcal isolate.

CONCLUSIONS

The present study demonstrated significant throat carriage of GAS and the presence of group C streptococci (S. dysgalactiae ssp. equisimilis) in an Argentinian rural population. These results point out the need for continuous surveillance of GAS and non-GAS carriage as well as of antimicrobial resistance in highly susceptible populations, such as school-aged rural children. An extended surveillance program including school-aged children from different cities should be considered to estimate the prevalence of GAS carriage in Argentina.

Use of next generation sequence to investigate potential novel macrolide resistance mechanisms in a population of Moraxella catarrhalis isolates

Although previous studies have confirmed that 23S rRNA gene mutation could be responsible for most of macrolide resistance in M. catarrhalis, a recent study suggested otherwise. Next generation sequence based comparative genomics has revolutionized the mining of potential novel drug resistant mechanisms. In this study, two pairs of resistant and susceptible M. catarrhalis isolates with different multilocus sequence types, were investigated for potential differential genes or informative single nucleotide polymorphisms (SNPs). The identified genes and SNPs were evaluated in 188 clinical isolates. From initially 12 selected differential genes and 12 informative SNPs, 10 differential genes (mboIA, mcbC, mcbI, mboIB, MCR_1794, MCR_1795, lgt2B/C, dpnI, mcbB, and mcbA) and 6 SNPs (C619T of rumA, T140C of rplF, G643A of MCR_0020, T270G of MCR_1465, C1348A of copB, and G238A of rrmA) were identified as possibly linked to macrolide resistance in M. catarrhalis. Most of the identified differential genes and SNPs are related to methylation of ribosomal RNA (rRNA) or DNA, especially MCR_0020 and rrmA. Further studies are needed to determine the function and/or evolution process, of the identified genes or SNPs, to establish whether some novel or combined mechanisms are truly involved in M. catarrhalis macrolide resistance mechanism.

Antibacterial resistance in Streptococcus pyogenes (GAS) from healthy carriers and tonsillitis patients and association with antibacterial sale in the Faroe Islands

The aim of this study was to investigate the antibacterial resistance of Streptococcus pyogenes (GAS), and correlate the findings with the sales of erythromycin and tetracycline. General practitioners in the Faroe Islands were recruited to send oropharyngeal swabs. From an ongoing pneumococcal study, nasopharyngeal swabs were sampled from healthy children 0-7 years of age. Erythromycin susceptibility data from Iceland were obtained from the reference laboratory at the Landspitali University Hospital. Susceptibility testing in the Faroe Islands and Iceland was performed according to CLSI methods and criteria. The resistance rate to erythromycin and tetracycline found in patients in the Faroe Islands in 2009/2010 was 6% and 30% respectively. Tetracycline resistance in patients declined significantly from 2009 to 2010 (37-10%, p-value = 0.006 < 0.05) and differed significantly between age groups (p-value = 0.03 < 0.05). In Iceland, there was a peak in erythromycin resistance in 2008 (44%) and a substantial decrease in 2009 (5%). Although the prevalence of erythromycin and tetracycline resistance in the Faroe Islands and Iceland may be associated with antimicrobial use, sudden changes can occur with the introduction of new resistant clones.

Recurrent bacteremia with different strains of Streptococcus pyogenes in an immunocompromised child

We report an immunocompromised child who experienced two episodes of bacteremia due to Streptococcus pyogenes. Random amplification of polymorphic DNA profiles, emm genotypes, superantigen profiles, antimicrobial susceptibility, and resistance-related genes were investigated, and the results showed different profiles between the two isolates. This is the first report describing recurrent bacteremia caused by different strains of S. pyogenes.

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.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Disease manifestations and pathogenic mechanisms of Group A Streptococcus

Streptococcus pyogenes, also known as group A Streptococcus (GAS), causes mild human infections such as pharyngitis and impetigo and serious infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. Furthermore, repeated GAS infections may trigger autoimmune diseases, including acute poststreptococcal glomerulonephritis, acute rheumatic fever, and rheumatic heart disease. Combined, these diseases account for over half a million deaths per year globally. Genomic and molecular analyses have now characterized a large number of GAS virulence determinants, many of which exhibit overlap and redundancy in the processes of adhesion and colonization, innate immune resistance, and the capacity to facilitate tissue barrier degradation and spread within the human host. This improved understanding of the contribution of individual virulence determinants to the disease process has led to the formulation of models of GAS disease progression, which may lead to better treatment and intervention strategies. While GAS remains sensitive to all penicillins and cephalosporins, rising resistance to other antibiotics used in disease treatment is an increasing worldwide concern. Several GAS vaccine formulations that elicit protective immunity in animal models have shown promise in nonhuman primate and early-stage human trials. The development of a safe and efficacious commercial human vaccine for the prophylaxis of GAS disease remains a high priority.

Characteristics of group A Streptococcus strains circulating during scarlet fever epidemic, Beijing, China, 2011

Scarlet fever is one of a variety of diseases caused by group A Streptococcus (GAS). During 2011, a scarlet fever epidemic characterized by peak monthly incidence rates 2.9–6.7 times higher than those in 2006–2010 occurred in Beijing, China. During the epidemic, hospital-based enhanced surveillance for scarlet fever and pharyngitis was conducted to determine characteristics of circulating GAS strains. The surveillance identified 3,359 clinical cases of scarlet fever or pharyngitis. GAS was isolated from 647 of the patients; 76.4% of the strains were type emm12, and 17.1% were emm1. Almost all isolates harbored superantigens speC and ssa. All isolates were susceptible to penicillin, and resistance rates were 96.1% to erythromycin, 93.7% to tetracycline, and 79.4% to clindamycin. Because emm12 type GAS is not the predominant type in other countries, wider surveillance for the possible spread of emm12 type GAS from China to other countries is warranted.

A report on the first outbreak of a single clone group A Streptococcus (emm-type 89) tonsillopharyngitis in China

In 2012, 28 out of 140 staff working for a film crew in a Beijing movie and television base experienced a sudden onset of fever, sore throat, and/or tiredness, headache within the 24 hour period of July 26-27. All of the patients visited the hospital and were diagnosed as having tonsillopharyngitis. On July 28, 2012, a team of Centers for Disease Control and Prevention staff arrived and initiated an outbreak investigation. Pharyngeal swabs were obtained from patients for microbiologic analysis. All isolates of the outbreak were analyzed for toxin-genes and drug-resistance genes by polymerase chain reaction, and were performed for the emm typing and pulsed-field gel electrophoresis typing. On July 30, 2012, Group A Streptococcus was isolated from eight of the 16 throat swab specimens obtained on site. These isolates were found to have the same genotype emm 89. This is the first report to identify Group A Streptococcus emm type-89 as a cause of tonsillopharyngitis in Beijing, China.

Streptococcus pyogenes and re-emergence of scarlet fever as a public health problem

Explosive outbreaks of infectious diseases occasionally occur without immediately obvious epidemiological or microbiological explanations. Plague, cholera and Streptococcus pyogenes infection are some of the epidemic-prone bacterial infections. Besides epidemiological and conventional microbiological methods, the next-generation gene sequencing technology permits prompt detection of genomic and transcriptomic profiles associated with invasive phenotypes. Horizontal gene transfer due to mobile genetic elements carrying virulence factors and antimicrobial resistance, or mutations associated with the two component CovRS operon are important bacterial factors conferring survival advantage or invasiveness. The high incidence of scarlet fever in children less than 10 years old suggests that the lack of protective immunity is an important host factor. A high population density, overcrowded living environment and a low yearly rainfall are environmental factors contributing to outbreak development. Inappropriate antibiotic use is not only ineffective for treatment, but may actually drive an epidemic caused by drug-resistant strains and worsen patient outcomes by increasing the bacterial density at the site of infection and inducing toxin production. Surveillance of severe S. pyogenes infection is important because it can complicate concurrent chickenpox and influenza. Concomitant outbreaks of these two latter infections with a highly virulent and drug-resistant S. pyogenes strain can be disastrous.

Molecular analysis of Streptococcus pyogenes strains isolated from Chinese children with pharyngitis

Streptococcus pyogenes is an important gram-positive bacterial pathogen that causes various human diseases, of which streptococcal pharyngitis is the most common. In this work, a total of 185 S. pyogenes isolated from Chinese children with pharyngitis was analyzed by superantigen (SAg) genes, emm genotyping, and pulsed-field gel electrophoresis (PFGE). Fifty-eight (31.4%) isolates were also typed by multilocus sequence typing (MLST). The results indicate that most of the emm1 isolates possessed speA (88.5%) and speJ (83.6%), and few isolates possessed speI gene (13.1%). In contrast, none of the emm12-type isolates possessed speJ; few isolates possessed speA (5.2%); and most of the isolates possessed speI (91.7%). PFGE analysis revealed 25 different clusters, and MLST was performed for 2 predominant emm-type isolates; emm12 isolates belonged to ST36 while emm1 isolates belonged to ST28. As far as this collection is concerned, emm1 and emm12 are the prevalent genotypes among S. pyogenes strains associated with children's pharyngitis in China. Most of the pharyngitis strains can be covered by a 26-valent vaccine. A strong correspondence is found only in the direction of emm type for both SAg profiles and PFGE types but not in the reverse direction.

Susceptibility of bacterial isolates from community-acquired infections in sub-Saharan Africa and Asia to macrolide antibiotics

OBJECTIVE

To review the literature on the susceptibility of common community pathogens in sub-Saharan Africa and Asia to the macrolide antibiotics.

METHODS

Inclusion criteria required that isolates were collected since 2004 to ensure results were of contemporary relevance. The data were aggregated by region, age group and sterility of site of culture sample.

RESULTS

A total of 51 studies were identified, which reported the macrolide antimicrobial susceptibilities of common bacterial pathogens isolated since 2004. In general, there was less macrolide resistance in African than in Asian isolates. Most African studies reported high levels of macrolide susceptibility in Streptococcus pneumoniae, whereas most Chinese studies reported high levels of resistance. There was very little information available for Gram-negative organisms.

CONCLUSIONS

Susceptibility of the pneumococcus to macrolides in SSA remains high in many areas, and good activity of azithromycin has been shown against Salmonellae spp. in Asia. In urban areas where high antibiotic consumption is prevalent, there was evidence of increased resistance to macrolides. However, there is no information on susceptibility from large areas in both continents.

Molecular investigation of macrolide and Tetracycline resistances in oral bacteria isolated from Tunisian children

OBJECTIVE

This study aims to investigate the antibiotic susceptibility of strains isolated from the oral cavity of Tunisian children.

DESIGN

Strains were isolated from the oral cavity of Tunisian children (60 caries-actives and 30 caries-free). Molecular characterization was assessed by PCR assay to detect erythromycin methylase gene (ermB), macrolide efflux (mefI) and tetracycline resistance genes (tetM and tetO).

RESULTS

A total of 21 species were isolated and identified. Antimicrobial susceptibility revealed that the resistance rate to antibiotics was as follow: erythromycin (22%), tetracycline (15.6%), cefotaxim, (7.3%), trimethoprim-sulfamethoxazol (37.6%), nitrofurantoine (2.8%), pristinamycin (17.4%), quinupristin-dalfopristin (15.6%), and rifampicin (3.7%). The majority of mefI positive strains (31.2%) were isolated from the carious children (n=34) in comparison with 8.25% from the control group (n=9). In addition, frequency of strains caring resistance genes were as follow: 12.84% for ermB, 9.17% for tetM and 27.52% for tetO from the carious children in comparison to 0.092%, 3.67% and 3.67% from the caries free group respectively.

CONCLUSION

Multi-resistance strains towards macrolides and tetracycline were recorded. The majority of strains carrying antibiotics resistance genes were isolated from the caries active children. The presence of multi-resistant bacteria in the oral cavity can be the major cause of antibiotic prophylaxis failure in dental practise.

The evolution of Helicobacter pylori antibiotics resistance over 10 years in Beijing, China

OBJECTIVES

To evaluate Helicobacter pylori antibiotics resistance evolution from 2000 to 2009 to amoxicillin, clarithromycin, metronidazole, tetracycline, levofloxacin and moxifloxacin in Beijing, China.

METHODS

A total of 374 H. pylori strains isolated from 374 subjects who had undergone upper gastrointestinal endoscopy from 2000 to 2009 were collected and examined by E-test method for antibiotics susceptibility.

RESULTS

The average antibiotics resistance rates were 0.3% (amoxicillin), 37.2% (clarithromycin), 63.9% (metronidazole), 1.2% (tetracycline), 50.3% (levofloxacin) and 61.9% (moxifloxacin). Overall resistance to clarithromycin, metronidazole, and fluoroquinolone increased annually (from 14.8 to 65.4%, 38.9 to 78.8%, and 27.1 to 63.5%, in 2000 or 2006-2007 to 2009, respectively). The secondary resistance rates were much higher than primary rates to these antibiotics, which also increased annually in recent 10 years.

CONCLUSIONS

The trend of clarithromycin, metronidazole, and fluoroquinolone resistance of H. pylori increased over time and the resistance to amoxicillin and tetracycline was infrequent and stable in Beijing. Clarithromycin, metronidazole, and fluoroquinolone should be used with caution for H. pylori eradication treatment.

Regulation of virulence gene expression in Streptococcus pyogenes: determinants of differential mRNA decay

Differential mRNA stability is an important mechanism for regulation of virulence factors in Streptococcus pyogenes (group A streptococcus, GAS), a serious and prevalent human pathogen. We have described 2 Classes of mRNA in GAS that are distinguishable by 1) stability in the stationary phase of growth, 2) kinetics of decay in exponential phase, and 3) effect of depletion of RNases J1 and J2 and polynucleotide phosphorylase (PNPase) on decay in exponential phase. We discuss features of the structure of an mRNA that appear to be important for determining the Class to which it belongs and present a model to explain differential mRNA decay.