Nanocomposite films as electrochemical sensors for detection of catalase activity.

Cross-linked hydrogel substrates have garnered attention as they simultaneously enable oxidoreductase reactions in a control volume extended to adsorption of redox capacitors for amplification of electrochemical signals. In this study, the effect of catalase immobilization in mold-casted alginate-based thin films (1 mm × 6 mm × 10 mm) containing multi walled carbon nanotubes (MWCNT) coated with chitosan has been studied via amperometry. The amperometric response was measured as a function of peroxide concentration, at a fixed potential of -0.4 V vs. SPCE in phosphate-buffered saline (pH = 7.4). Results indicate substrate detection is not diffusion-limited by the 100 µm thick chitosan layer, if the cationic polyelectrolyte is in contact with the sensing carbon electrode, and the linear detection of the enzyme absent in solution is enabled by immobilization (R 2 = 0.9615). The ferricyanide-mediated biosensor exhibited a sensitivity of 4.55 µA/mM for the optimal formulation at room temperature comparable to other nanomaterial hybrid sensing solution namely amine-functionalized graphene with an average response time of 5 s for the optimal formulation. The suitability of the optimized chitosan-coated alginate slabs nano-environment for co-encapsulation of catalase and carbon nanotubes was confirmed by cyclic voltammetry.

Prospective Longitudinal Analysis of Immune Responses in Pediatric Subjects After Pharyngeal Acquisition of Group A Streptococci.

BACKGROUND.: Despite the significant burden of disease associated with infection by group A streptococcus (GAS), little is known about the human immune response to GAS antigens after natural infection. METHODS.: We evaluated 195 serum samples obtained prospectively over a consecutive 24-month period from 41 pediatric subjects who experienced a new pharyngeal GAS acquisition. An enzyme-linked immunoassay was used to determine the kinetics and antigen specificity of antibodies against 13 shared GAS antigens and 18 type-specific M peptides. The majority of the antigens tested are currently being considered as vaccine candidates. RESULTS.: Twelve M types of GAS were recovered from 41 subjects who experienced 51 new GAS acquisitions that elicited antibody responses against at least 1 of the 31 antigens tested (immunologically significant new GAS acquisitions). The immune responses to the 13 shared antigens were highly variable. Increases in antibody levels were detected against a mean of 3.5 shared antigens (range, 1-8). Antibody responses to the homologous M peptide were observed in 32 (63%) of the 51 episodes. Seven subjects acquired more than 1 M type of GAS. There were no new immunologically significant acquisitions of an M type against which the subject had preexisting antibodies to the homologous M peptide. Of the subjects with new GAS acquisition, 65% were asymptomatic, yet immune responses were detected against 1 or more GAS antigens. Immune responses to streptolysin O and/or deoxyribonuclease B were observed after 67% of the new GAS acquisitions. Persistently positive (>12 weeks) throat culture results were returned for 20% of the 41 subjects despite immune responses to homologous M peptides and/or shared antigens. CONCLUSIONS.: The availability of throat culture results, GAS isolates, and serial serum samples collected prospectively over a 2-year period of observation provided a unique opportunity for us to assess the serologic status of pediatric subjects before and after new pharyngeal acquisitions of GAS. With the exception of antibody responses to the homologous M peptides, no clear pattern of immune responses against the remaining GAS antigens was seen. There were no new immunologically significant acquisitions of emm types of GAS against which the subjects had preexisting elevated levels of antibodies against the homologous M peptide. The observation that 65% of new GAS acquisitions caused no symptoms yet were immunologically significant suggests that the majority of infections are not detected, which would result in missed opportunities for primary prevention of rheumatic fever and rheumatic heart disease with appropriate antimicrobial therapy.

Clinical Perineal Streptococcal Infection in Children: Epidemiologic Features, Low Symptomatic Recurrence Rate after Treatment, and Risk Factors for Recurrence.

OBJECTIVES: To evaluate the epidemiology of perineal streptococcal infection and recurrence rates following amoxicillin treatment. STUDY DESIGN: We used laboratory logs in a single pediatric practice to identify patients 0-18 years of age with perineal cultures positive for group A Streptococcus (GAS) and reviewed their medical charts. We described epidemiologic features, determined recurrence rates following antibiotic treatment, and performed a case-control study to identify possible risk factors for recurrence in patients treated with amoxicillin. RESULTS: We found a perineal streptococcal infection rate of 4.6 per 10,000 patient encounters and a recurrence rate in 157 patients with perineal streptococcal infection of 12.4% after amoxicillin. In male patients, the predominant site of involvement was the perianal region (86%), and for female patients, the perivaginal area (62%). Nearly 80% of patients were 2-7 years of age (range 18 days-12.5 years). Perineal streptococcal infection and GAS pharyngitis followed a similar seasonal pattern of occurrence with 65% of perineal streptococcal infection occurring October through March. In patients with perineal streptococcal infection, 95% had a concomitant pharyngeal culture positive for GAS. Best predictive factors for recurrence after amoxicillin were longer duration of symptoms prior to diagnosis and having a sibling with perineal streptococcal infection at some time before or after the initial episode. CONCLUSIONS: Following treatment with amoxicillin, we found a low recurrence rate of 12.4%. Amoxicillin can be expected to be reliable first-line therapy for perineal streptococcal infection.

Tracing the evolutionary history of the pandemic group A streptococcal M1T1 clone.

The past 50 years has witnessed the emergence of new viral and bacterial pathogens with global effect on human health. The hyperinvasive group A Streptococcus (GAS) M1T1 clone, first detected in the mid-1980s in the United States, has since disseminated worldwide and remains a major cause of severe invasive human infections. Although much is understood regarding the capacity of this pathogen to cause disease, much less is known of the precise evolutionary events selecting for its emergence. We used high-throughput technologies to sequence a World Health Organization strain collection of serotype M1 GAS and reconstructed its phylogeny based on the analysis of core genome single-nucleotide polymorphisms. We demonstrate that acquisition of a 36-kb genome segment from serotype M12 GAS and the bacteriophage-encoded DNase Sda1 led to increased virulence of the M1T1 precursor and occurred relatively early in the molecular evolutionary history of this strain. The more recent acquisition of the phage-encoded superantigen SpeA is likely to have provided selection advantage for the global dissemination of the M1T1 clone. This study provides an exemplar for the evolution and emergence of virulent clones from microbial populations existing commensally or causing only superficial infection.

Streptococcal upper respiratory tract infections and exacerbations of tic and obsessive-compulsive symptoms: a prospective longitudinal study.

OBJECTIVE: The objective of this blinded, prospective, longitudinal study was to determine whether new group A ß hemolytic streptococcal (GABHS) infections are temporally associated with exacerbations of tic or obsessive-compulsive (OC) symptoms in children who met published criteria for pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS). A group of children with Tourette syndrome and/or OC disorder without a PANDAS history served as the comparison (non-PANDAS) group. METHOD: Consecutive clinical ratings of tic and OC symptom severity were obtained for 31 PANDAS subjects and 53 non-PANDAS subjects. Clinical symptoms and laboratory values (throat cultures and streptococcal antibody titers) were evaluated at regular intervals during a 25-month period. Additional testing occurred at the time of any tic or OC symptom exacerbation. New GABHS infections were established by throat swab cultures and/or recent significant rise in streptococcal antibodies. Laboratory personnel were blinded to case or control status, clinical (exacerbation or not) condition, and clinical evaluators were blinded to the laboratory results. RESULTS: No group differences were observed in the number of clinical exacerbations or the number of newly diagnosed GABHS infections. On only six occasions of a total of 51 (12%), a newly diagnosed GABHS infection was followed, within 2 months, by an exacerbation of tic and/or OC symptoms. In every instance, this association occurred in the non-PANDAS group. CONCLUSIONS: This study provides no evidence for a temporal association between GABHS infections and tic/OC symptom exacerbations in children who meet the published PANDAS diagnostic criteria.

The human immune response to streptococcal extracellular antigens: clinical, diagnostic, and potential pathogenetic implications.

BACKGROUND: Determination of an immune response to group A Streptococcus (GAS) antigens, frequently anti-streptolysin O and anti-DNase B, is crucial for documentation of bona fide GAS infection. Although the importance of immunologic confirmation of infection is widely accepted, the immediate and long-term immunokinetics of the human antibody response are incompletely documented and poorly understood. METHODS: Pediatric study participants (n = 160) were followed during a 2-year study with monthly throat cultures (n = 3491) and blood samples (n = 1679) obtained every 13 weeks. Recovered GAS were characterized; serum anti-streptolysin O and anti-DNase B antibody titers were determined. Antibody titers and GAS culture results were temporally correlated and analyzed. RESULTS: The analyses clearly document, in some instances for the first time, that an increase in antibody titer more accurately defines infection than does an absolute titer (eg, "upper limit of normal"), that antibody titers can remain elevated for many months even without GAS, and that some individuals may harbor GAS continuously for months or years without symptoms of infection and without an associated immune response. Measuring 2 different antibodies is more accurate in defining infection. CONCLUSIONS: Single time-point cultures and single antibody titers are often misleading. Sequential samples more accurately define infection, allowing correlation of titer increases with temporal confirmation of GAS acquisition. Understanding kinetics of the immune response(s) to GAS infection is necessary in formulating accurate clinical diagnostic conclusions, to appropriate design of clinical and epidemiological studies examining the association of GAS with subsequent sequelae, and to providing insight into pathogenetic mechanisms associated with this important human pathogen.

Streptococcal upper respiratory tract infections and psychosocial stress predict future tic and obsessive-compulsive symptom severity in children and adolescents with Tourette syndrome and obsessive-compulsive disorder.

BACKGROUND: One goal of this prospective longitudinal study was to identify new group A beta-hemolytic streptococcal infections (GABHS) in children and adolescents with Tourette syndrome (TS) and/or obsessive-compulsive disorder (OCD) compared with healthy control subjects. We then examined the power of GABHS infections and measures of psychosocial stress to predict future tic, obsessive-compulsive (OC), and depressive symptom severity. METHODS: Consecutive ratings of tic, OC, and depressive symptom severity were obtained for 45 cases and 41 matched control subjects over a 2-year period. Clinical raters were blinded to the results of laboratory tests. Laboratory personnel were blinded to case or control status and clinical ratings. Structural equation modeling for unbalanced repeated measures was used to assess the sequence of new GABHS infections and psychosocial stress and their impact on future symptom severity. RESULTS: Increases in tic and OC symptom severity did not occur after every new GABHS infection. However, the structural equation model found that these newly diagnosed infections were predictive of modest increases in future tic and OC symptom severity but did not predict future depressive symptom severity. In addition, the inclusion of new infections in the model greatly enhanced, by a factor of three, the power of psychosocial stress in predicting future tic and OC symptom severity. CONCLUSIONS: Our data suggest that a minority of children with TS and early-onset OCD were sensitive to antecedent GABHS infections. These infections also enhanced the predictive power of current psychosocial stress on future tic and OC symptom severity.

Determination of group a streptococcal anti-M type-specific antibody in sera of rheumatic fever patients after 45 years.

Group A streptococcal M type--specific protective antibodies-especially their persistence in humans--are incompletely understood. Such information is essential for understanding the epidemiology and pathogenesis of these infections and their sequelae and is equally crucial for producing a group A streptococcal vaccine. We studied 2 adults for type-specific antibody 45 years after they experienced documented rheumatic fever.

Cellular effects of enamel matrix derivative are associated with different molecular weight fractions following separation by size-exclusion chromatography.

BACKGROUND: Enamel matrix derivative (EMD) was shown to enhance soft tissue healing and regeneration of the periodontium; however, the mechanisms of this action are unknown. It is assumed that amelogenin, the most abundant protein in EMD, is the protein primarily responsible for the effects of EMD. The purpose of this study was to fractionate EMD and associate its specific cellular effects with different molecular weight fractions following size-exclusion chromatography. METHODS: Freshly dissolved EMD was fractionated by gel filtration, and forty-five 7-ml fractions were collected, desalted, lyophilized, and resuspended. These fractions were analyzed for their effects on the differentiation of osteoprogenitor cells (C2C12) and the proliferation and differentiation of human microvascular endothelial cells (HMVECs). Alkaline phosphatase activity (C2C12) was measured as a marker for osteogenic differentiation before and after preincubation of the fractions with the bone morphogenetic protein (BMP) decoy receptor, noggin. Angiogenesis (HMVEC) was evaluated as a marker for endothelial cell differentiation. Enzymographic assays used polyacrylamide gels copolymerized with denatured type I collagen to determine gelatinolytic activities in each fraction. RESULTS: EMD fractionated into three major protein peaks following size exclusion chromatography with cross-linked dextran particle matrix. Peak I was associated with the column void volume, whereas peak III eluted near the salt volume. Peak II eluted between these two peaks. Proliferation and angiogenic activities were associated with peaks II and III for the microvascular cells. The differentiation of osteoprogenitor cells, indicated by alkaline phosphatase activity, was induced by EMD components present in peak I and the leading edge of peak II. The additional observation that this differentiation was inhibited by prior treatment of the fractions with noggin suggested the activity was induced by BMP rather than amelogenin or other unknown proteins. Gelatinolytic activities were detected in the early fractions of peaks I and II of gel-fractionated EMD. CONCLUSIONS: The cellular activities stimulated by EMD are not associated with a single molecular weight species. The fact that noggin abolishes C2C12 alkaline phosphatase activity suggests that effects on osteoprogenitor cell differentiation are the result of a BMP-like protein(s), whereas effects on proliferation and angiogenesis are associated with lower molecular weight species present in peaks II and III. Finally, unheated EMD displays gelatinolytic activities that are also detectable following size-exclusion separation of its constituents. The masses of these activities were consistent with those reported for latent and active matrix metalloproteinase-20.

Increased prevalence and mortality in undiagnosed celiac disease.

BACKGROUND & AIMS: The historical prevalence and long-term outcome of undiagnosed celiac disease (CD) are unknown. We investigated the long-term outcome of undiagnosed CD and whether the prevalence of undiagnosed CD has changed during the past 50 years. METHODS: This study included 9133 healthy young adults at Warren Air Force Base (sera were collected between 1948 and 1954) and 12,768 gender-matched subjects from 2 recent cohorts from Olmsted County, Minnesota, with either similar years of birth (n = 5558) or age at sampling (n = 7210) to that of the Air Force cohort. Sera were tested for tissue transglutaminase and, if abnormal, for endomysial antibodies. Survival was measured during a follow-up period of 45 years in the Air Force cohort. The prevalence of undiagnosed CD between the Air Force cohort and recent cohorts was compared. RESULTS: Of 9133 persons from the Air Force cohort, 14 (0.2%) had undiagnosed CD. In this cohort, during 45 years of follow-up, all-cause mortality was greater in persons with undiagnosed CD than among those who were seronegative (hazard ratio = 3.9; 95% confidence interval, 2.0-7.5; P < .001). Undiagnosed CD was found in 68 (0.9%) persons with similar age at sampling and 46 (0.8%) persons with similar years of birth. The rate of undiagnosed CD was 4.5-fold and 4-fold greater in the recent cohorts, respectively, than in the Air Force cohort (both P < or = .0001). CONCLUSIONS: During 45 years of follow-up, undiagnosed CD was associated with a nearly 4-fold increased risk of death. The prevalence of undiagnosed CD seems to have increased dramatically in the United States during the past 50 years.

A school-based program for control of group a streptococcal upper respiratory tract infections: a controlled trial in Southern China.

A prospective, school-based study included daily monitoring for incidence of symptomatic streptococcal-associated pharyngitis and monthly determinations of group A streptococcal prevalence. A treatment group received penicillin/erythromycin therapy at school for positive throat cultures; the control group sought medical care from their regular provider. Prevalence and incidence of group A streptococcal pharyngitis were significantly lower among the treatment group than in the controls.

Streptococcal infection and exacerbations of childhood tics and obsessive-compulsive symptoms: a prospective blinded cohort study.

OBJECTIVE: If pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections is a unique clinical entity, we hypothesized that children meeting diagnostic criteria would have more clinical exacerbations temporally linked to bona fide group A beta-hemolytic streptococcus infection than matched control subjects (chronic tic and/or obsessive-compulsive disorder with no known temporal relationship to group A beta-hemolytic streptococcus infection). PATIENTS AND METHODS: Subjects included 40 matched pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections case-control pairs who were prospectively evaluated with intensive laboratory testing for group A beta-hemolytic streptococcus and clinical measures for an average of 2 years. Additional testing occurred at the time of any clinical exacerbations or illness. Laboratory personnel were blinded to case or control status and clinical (exacerbation or not) condition. Clinical raters were blinded to the results of laboratory tests. RESULTS: The cases had a higher clinical exacerbation rate and a higher bona fide group A beta-hemolytic streptococcus infection rate than the control group. Only 5 of 64 exacerbations were temporally associated (within 4 weeks) with a group A beta-hemolytic streptococcus infection, and all occurred in cases. The number (5.0) was significantly higher than the number that would be expected by chance alone (1.6). Yet, >/=75% of the clinical exacerbations in cases had no observable temporal relationship to group A beta-hemolytic streptococcus infection. CONCLUSIONS: Patients who fit published criteria for pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections seem to represent a subgroup of those with chronic tic disorders and obsessive-compulsive disorder who may be vulnerable to group A beta-hemolytic streptococcus infection as a precipitant of neuropsychiatric symptom exacerbations. Group A beta-hemolytic streptococcus infection is not the only or even the most common antecedent event associated with exacerbations for these patients. Additional intensive studies are needed to determine whether there is clinical or scientific evidence to support separating out subgroups of tic disorder and/or obsessive-compulsive disorder patients based on specific symptom precipitants.

Unexpected individual clinical site variation in eradication rates of group a streptococci by penicillin in multisite clinical trials.

BACKGROUND: Previously, we reported an unexpectedly large percentage of failures by penicillin to eradicate group A streptococci (GAS) from the upper respiratory tract. Because penicillin has been the recommended therapy for the treatment of GAS pharyngitis, our report prompted controversy. Data from clinical trials in which our laboratory has participated demonstrated marked variation in GAS eradication rates among clinical sites. The reasons for such variation have never been adequately examined. We performed statistical analyses of site variation in eradication rates to assess the potential effect on reported reduced penicillin efficacy. METHODS: Penicillin GAS eradication rates were compared using data from 4 large multisite pharyngitis treatment trials (75 clinical sites; 1158 subjects). Variation in eradication rates among clinical sites was statistically evaluated [chi(2) tests and generalized estimating equation (GEE) regression models]. RESULTS: There was significant site-to-site variation in GAS eradication rates in each of the trials (range, 17-100%; P < 0.005) as well as between separate trials (mean range, 58-69%; P < 0.033). GEE modeling indicated that GAS eradication rates were significantly higher for clinical sites participating in more than one clinical trial. CONCLUSIONS: The statistically significant site-to-site variation in penicillin eradication rates was related to factors (dependencies) at individual sites. Such factors may affect assessment of therapeutic efficacy and indicate a necessity for considering clinical site variation before reporting pooled efficacy data from multiple sites; combined data may result in misleading clinical implications. This is the first report documenting significant variation resulting from individual clinical site-related factors and offers a possible explanation for reduced penicillin eradication.

Group A streptococcal isolates temporally associated with acute rheumatic fever in Hawaii: differences from the continental United States.

BACKGROUND: The annual incidence of acute rheumatic fever (ARF) in Hawaii has remained several times higher than that in the continental United States, particularly among ethnic Polynesians. The emm types of Streptococcus pyogenes that are associated with this nonsuppurative complication have, to our knowledge, not been previously reported in Hawaii. METHODS: Patients with ARF were identified through an active surveillance system at Kapiolani Medical Center (Honolulu, HI), the only pediatric tertiary care referral hospital in Hawaii. Specimens were obtained by throat culture from patients who met the Jones criteria for ARF at the time of presentation (63 patients), prior to penicillin treatment, and from consenting family contacts (10 individuals). Eight patients and 2 close family contacts with positive throat culture results were identified from February 2000 through December 2005. Group A streptococci isolates were characterized by emm sequence typing. RESULTS: Unusual emm types were temporally associated with the onset of ARF. Emm types 65/69 (from 2 patients), 71, 92, 93, 98, 103, and 122 were isolated from the 8 patients with ARF, and emm types 52 and 101 were isolated from the 2 household contacts. CONCLUSIONS: So-called rheumatogenic emm types and/or serotypes, which were previously associated with ARF in the continental United States, were not found in this study. Instead, emm types that are not commonly included among group A streptococci isolates in the continental United States and that are seldom, if ever, temporally associated with ARF were identified. These findings suggest that unusual group A streptococci emm types play a significant role in the epidemiology of ARF in Hawaii.

International quality assurance study for characterization of Streptococcus pyogenes.

Surveillance of group A streptococcal (GAS) infections was undertaken as a major component of the European Commission-funded project on severe GAS disease in Europe (strep-EURO). One aim of strep-EURO was to improve the quality of GAS characterization by standardization of methods. An external quality assurance study (EQA) was therefore carried out to evaluate current global performance. Eleven strep-EURO and seven other streptococcal reference centers received a panel of 20 coded GAS isolates for typing. Conventional phenotypic typing (based on cell surface T and M protein antigens and opacity factor [OF] production) and molecular methods (emm gene typing) were used either as single or combined approaches to GAS typing. T typing was performed by 16 centers; 12 centers found one or more of the 20 strains nontypeable (typeability, 89%), and 11 centers reported at least one incorrect result (concordance, 93%). The 10 centers that tested for OF production achieved 96% concordance. Limited availability of antisera resulted in poor typeability values from the four centers that performed phenotypic M typing (41%), three of which also performed anti-OF typing (typeability, 63%); however, concordance was high for both M (100%) and anti-OF (94%) typing. In contrast, the 15 centers that performed emm gene sequencing achieved excellent typeability (97%) and concordance (98%), although comparison of the performance between centers yielded typeability rates from 65 to 100% and concordance values from 83 to 100%. With the rapid expansion and use of molecular genotypic methods to characterize GAS, continuation of EQA is essential in order to achieve international standardization and comparison of type distributions.

Treatment of streptococcal pharyngitis with once-daily compared with twice-daily amoxicillin: a noninferiority trial.

BACKGROUND: Two relatively small previous studies comparing once-daily amoxicillin with conventional therapy for group A streptococcal (GAS) pharyngitis reported similar rates of bacteriologic success for each treatment group. The purpose of this study was to further evaluate once-daily amoxicillin for GAS pharyngitis in a larger study. METHODS: In a single pediatric practice, from October through May for 2 consecutive years (2001-2003), we recruited children 3 to 18 years of age who had symptoms and signs suggestive of GAS pharyngitis. Patients with a positive rapid test for GAS were stratified by weight (<40 kg or >or=40 kg) and then randomly assigned to receive once-daily (750 mg or 1000 mg) or twice-daily (2 doses of 375 mg or 500 mg) amoxicillin for 10 days. We determined bacteriologic failure rates for GAS in the pharynx from subsequent swabs taken at 14 to 21 (visit 2) and 28 to 35 (visit 3) days after treatment initiation. We conducted a randomized, controlled, investigator-blinded, noninferiority trial to evaluate whether amoxicillin given once daily would have a bacteriologic failure rate no worse than that of amoxicillin given twice daily within a prespecified margin of 10%. GAS isolates were characterized to distinguish bacteriologic failures from new acquisitions. Adverse events were described and adherence was evaluated by review of returned daily logs and dosage bottles. RESULTS: Of 2139 potential study patients during the 2-year period, we enrolled 652 patients, 326 into each treatment group. Children in the 2 groups were comparable with respect to all demographic and clinical characteristics except that children <40 kg more often presented with rash in each treatment group. At visit 2, failure rates were 20.1% (59 of 294) for the once-daily group and 15.5% (46 of 296) for the twice-daily group (difference, 4.53%; 90% confidence interval [CI], -0.6 to 9.7). At visit 3, failure rates were 2.8% (6 of 216) for the once-daily group and 7.1% (16 of 225) for the twice-daily group (difference, -4.33; 90% CI, -7.7 to -1.0). Gastrointestinal and other adverse events occurred in the once-daily treatment group with a frequency comparable to that in the twice-daily treatment group. Presumed allergic reactions occurred in 0.9% (6 of 635). More than 95% (516 of 541) of patients complied with 10 days of therapy with no significant differences between groups. CONCLUSIONS: We conclude that amoxicillin given once daily is not inferior to amoxicillin given twice daily. Gastrointestinal and other events did not occur significantly more often in the once-daily treatment group. From the data in this large, investigator-blinded, controlled study, once-daily amoxicillin appears to be a suitable regimen for treatment of GAS pharyngitis.

Characterization of group A streptococci (Streptococcus pyogenes): correlation of M-protein and emm-gene type with T-protein agglutination pattern and serum opacity factor.

Strain characterization of group A streptococci (GAS) has traditionally been based on serological identification of M protein. Additional tests to determine T-protein serotype and production of streptococcal serum opacity factor (SOF) provide important information both to aid in and to supplement M-protein serotyping. Advances in DNA-sequencing technology in the late twentieth century resulted in the development of a method for determining the M type of GAS from the sequence of the gene encoding M protein, the emm gene. Although emm-sequence typing has largely replaced M typing in many laboratories, information provided by T typing and SOF determination continues to provide valuable supplementary information for strain characterization. A comprehensive summary of the correlation of T pattern and SOF production with M type was last published in 1993, several years before emm typing became widely available. Since then, the ease of M-type identification afforded by emm typing has resulted in an increase in the number of confirmed M/emm types of more than 50 %. However, comprehensive information about T-protein serotype and the correlation of SOF production with these new M/emm types is not widely available. This report presents a comprehensive summary of this information, not only for newly described types, but also updated information for previously described types. This information was extracted from combined records from streptococcal reference laboratories at the University of Minnesota and at the Centers for Disease Control and Prevention in Atlanta. Data from more than 40,000 strains (representing uncomplicated GAS infections, systemic invasive infections and strains associated with non-suppurative sequelae, collected from the US and diverse locations worldwide) were analysed.

Erythromycin-resistant group a streptococcal isolates collected between 2000 and 2005 in Oahu, Hawaii, and their emm types.

We examined erythromycin and clindamycin susceptibilities with Etest methodology among 546 group A streptococcal isolates collected in Hawaii between February 2000 and November 2004. Erythromycin resistance was low (3.1%). No isolate was clindamycin resistant. The prevalence of erythromycin resistance in group A streptococci remains low in Hawaii.

Intrinsic reduced susceptibility of serotype 6 Streptococcus pyogenes to fluoroquinolone antibiotics.

BACKGROUND: Fluoroquinolone resistance is common in Staphylococcus aureus, is increasing in Streptococcus pneumoniae, and is reported in Streptococcus pyogenes. METHODS: We surveyed 384 clinical isolates of S. pyogenes, isolated during 2002-2003, for susceptibility to ciprofloxacin. We performed nucleotide sequencing of the parC and gyrA genes and determined the M/emm type for selected isolates. Additionally, we analyzed M/emm type 6 S. pyogenes isolated during 1918-2003 from diverse locations. RESULTS: Of the survey isolates, 10.9% had reduced zones of inhibition to ciprofloxacin in the disk-diffusion test and had elevated minimum inhibitory concentrations to other fluoroquinolones, compared with those of fully susceptible isolates. Of the resistant isolates, 90.5% were M/emm type 6, and all sequenced M/emm type 6 isolates contained a serine-to-alanine substitution at position 79 in parC. Strikingly, the same findings were also present in macrolide-resistant isolates from a recent outbreak of S. pyogenes infection in Pittsburgh and in the Lancefield reference strain of M type 6, which was isolated in 1918, decades before the development of fluoroquinolone antibiotics. CONCLUSION: M/emm type 6 S. pyogenes has intrinsic reduced susceptibility to fluoroquinolones, as a result of a polymorphism in parC. This finding was also demonstrated in erythromycin-resistant M/emm type 6 S. pyogenes, which raises concern for the emergence of multidrug-resistant S. pyogenes.

Invasive group A streptococcal infection in high school football players, New York City, 2003.

After being notified that 2 high school football teammates from New York City were hospitalized with confirmed or suspected invasive group A streptococcal infections, we conducted an investigation of possible spread among other team members. This investigation highlights a need for guidelines on management of streptococcal and other infectious disease outbreaks in team sport settings.