Asymptomatic Pharyngeal Carriage Research Articles

Prevalence of group A streptococcal carriage in school children from Cape Town: A cross- sectional study and systematic review


 
 
 
 Background. Asymptomatic children can be a major reservoir of pharyngeal group A streptococcus (GAS). The role of GAS carriage causing subsequent infections resulting in the manifestation of clinical symptoms, or being associated with transmission to uninfected individuals, is not entirely clear. Furthermore, data on GAS carriage from countries in Africa remain scant with only a few studies reporting carriage.
 Objectives. We performed a cross-sectional study to determine the prevalence of asymptomatic pharyngeal carriage of group A streptococci in school children in Cape Town. We considered our results in the context of a meta-analysis of data of GAS carriage in Africa.
 Methods. We conducted a school-based cross-sectional study from 2009 to 2011 in two Cape Town peri-urban communities, enrolling 950 healthy learners. Pharyngeal swabs were obtained from learners and processed at the National Health Laboratory Service (NHLS) microbiology laboratory at Groote Schuur Hospital, Cape Town. Thereafter, we conducted a systematic review through a comprehensive literature search among several sources. Prevalence estimates with 95% confidence intervals (CIs) were determined using a random-effects meta-analysis model.
 Results. GAS was isolated from 31 participants corresponding to a carrier rate of 3% (95% CI 2% - 4%). Combining our results with 18 other studies revealed a pooled prevalence of 9% (95% CI 6% - 11%). Regional pooled rates were similar across southern, eastern and northern Africa, of between 9% (95% CI 6% - 11%) and 11% (95% CI 4% - 21%) while countries within Central Africa had a pooled estimate of 7% (95% CI 5% - 9%). Western Africa had the lowest pooled estimate of 2% (95% CI 1% - 2%).
 Conclusion. There was a relatively low rate of carriage of GAS in asymptomatic school children residing in South Africa. Pooled prevalence rates revealed regional differences across the African continent as regards the rate of GAS carriage, with the western and northern African regions having rates of GAS carriage that were lower and higher respectively than those of East, Central and southern African countries, which demonstrated similar rates of carriage.
 
 
 

1332. Population structure and genomic analysis of pediatric Streptococcus pyogenes clinical isolates in the United States, 2020 – 2022

Abstract Background Streptococcus pyogenes (GAS) is the major cause of bacterial pharyngitis in children. GAS can cause conditions ranging from asymptomatic pharyngeal carriage to invasive infection. We compared the genomic characteristics of GAS pharyngeal and invasive isolates from U.S. children. Methods We cultured GAS from throat swabs collected from children aged 3–18 years with acute GAS pharyngitis, diagnosed by rapid antigen or molecular test, and from a convenience sample of asymptomatic children during 1/2020 to 3/2022 in Chicago, IL; Atlanta, GA; Portland, OR; Phoenix, AZ. We collected invasive isolates in Chicago. Whole-genome sequencing (WGS) was performed on the Illumina MiSeq for species confirmation, isolate typing, and virulence and antimicrobial gene identification. Reference-based read alignment was used for whole genome phylogenetic analysis. Results Of 1144 collected throat swabs, 684 were from children with pharyngitis and 460 from asymptomatic children. 13 invasive GAS isolates were collected. GAS were cultured from 359 pharyngitis and 20 asymptomatic swabs. Of these, 371 GAS isolates could be recovered and underwent WGS. Thirty isolates (8%) were either low-quality sequences and/or identified as species other than S. pyogenes and were excluded. Whole-genome phylogenetic analysis of 341 GAS (215 pharyngitis, 13 asymptomatic, 13 invasive) identified 25 related clusters and 8 singletons (Figure 1). Virulence gene complements within given emm types were generally concordant with recently published CDC strain data. The most frequently identified resistance genes were tetM and ermB. 281 isolates (82%) carried no antibiotic resistance genes. Some clusters were significantly more represented at certain sites within apparent geographically defined clusters of nearly indistinguishable isolates (Figure 1): cluster 1 in Chicago, emm type 3; cluster 14 in Phoenix and Portland, emm 28, 12; and cluster 15 in Atlanta, emm 89. No major genomic factors were significantly associated with asymptomatic vs pharyngitis vs invasive presentation. Figure 1:Whole genome phylogenetic tree of pediatric GAS isolates Maximum likelihood phylogenetic analysis based on whole-genome alignment of 371 Group A Streptococcus isolates. Tip colors represent cluster assignments based on genetic similarity. Inner ring represents geographic location of GAS isolation. Outer ring represents patient presentation: asymptomatic colonization, symptomatic pharyngitis, or invasive infection. Conclusion Pharyngeal and invasive GAS in children within individual clonal complexes are co-included in closely related clusters, with evidence of close transmission within individual sites Disclosures All Authors: No reported disclosures.

Asymptomatic Pharyngeal Carriage of Kingella kingae Among Young Children in Vancouver, British Columbia, Canada.

Kingella kingae has emerged as a significant cause of osteoarticular infections in young children. Pharyngeal colonization is considered a prerequisite for invasive K. kingae infection. We conducted a prospective study to estimate the prevalence of pharyngeal carriage of K. kingae among healthy young children in Vancouver. From March 2016 to May 2017, children between 6 and 48 months of age visiting British Columbia Children's Hospital outpatient clinics for noninfectious causes were included in the study. Another set of participants was enrolled from a day-care center located at British Columbia Children's Hospital. A single-throat swab was collected after obtaining consent from parent/guardian. The samples were stored at -70°C and tested using an in-house developed real-time polymerase chain reaction assay. Epidemiologic characteristics and risk factors for K. kingae colonization were collected via a study questionnaire. A total of 179 children were enrolled in the study, but only 174 samples were eligible for testing. Of the 174 samples, 5 had indeterminate results and the remaining 169 samples were negative by K. kingae polymerase chain reaction. The median age of participants was 23 months. About 36% of children were attending day care and had another sibling <5 years of age. Previous history of cold symptoms and antibiotic use was reported in 42% and 12%, respectively. The results of our study showed no prevalence of asymptomatic pharyngeal carriage of K. kingae in young children in Vancouver. Additional multicenter studies may help to understand the differences in pharyngeal carriage rate among healthy children.

Group A Streptococcus pharyngitis and pharyngeal carriage: A meta-analysis.

ObjectiveAntibiotic treatment of Group A Streptococcus (GAS) pharyngitis is important in acute rheumatic fever (ARF) prevention, however clinical guidelines for prescription vary. GAS carriers with acute viral infections may receive antibiotics unnecessarily. This review assessed the prevalence of GAS pharyngitis and carriage in different settings.MethodsA random-effects meta-analysis was performed. Prevalence estimates for GAS+ve pharyngitis, serologically-confirmed GAS pharyngitis and asymptomatic pharyngeal carriage were generated. Findings were stratified by age group, recruitment method and country income level. Medline and EMBASE databases were searched for relevant literature published between 1 January 1946 and 7 April 2017. Studies reporting prevalence data on GAS+ve or serologically-confirmed GAS pharyngitis that stated participants exhibited symptoms of pharyngitis or upper respiratory tract infection (URTI) were included. Included studies reporting the prevalence of asymptomatic GAS carriage needed to state participants were asymptomatic.Results285 eligible studies were identified. The prevalence of GAS+ve pharyngitis was 24.1% (95% CI: 22.6–25.6%) in clinical settings (which used ‘passive recruitment’ methods), but less in sore throat management programmes (which used ‘active recruitment’, 10.0%, 8.1–12.4%). GAS+ve pharyngitis was more prevalent in high-income countries (24.3%, 22.6–26.1%) compared with low/middle-income countries (17.6%, 14.9–20.7%). In clinical settings, approximately 10% of children swabbed with a sore throat have serologically-confirmed GAS pharyngitis, but this increases to around 50–60% when the child is GAS culture-positive. The prevalence of serologically-confirmed GAS pharyngitis was 10.3% (6.6–15.7%) in children from high-income countries and their asymptomatic GAS carriage prevalence was 10.5% (8.4–12.9%). A lower carriage prevalence was detected in children from low/middle income countries (5.9%, 4.3–8.1%).ConclusionsIn active sore throat management programmes, if the prevalence of GAS detection approaches the asymptomatic carriage rate (around 6–11%), there may be little benefit from antibiotic treatment as the majority of culture-positive patients are likely carriers.

Use of sodC versus ctrA for real-time polymerase chain reaction-based detection of Neisseria meningitidis in sterile body fluids

We evaluated the use of a newly described sodC-based real-time-polymerase chain reaction (RT-PCR) assay for detecting Neisseria meningitidis in normally sterile sites, such as cerebrospinal fluid and serum. The sodC-based RT-PCR assay has an advantage over ctrA for detecting nongroupable N. meningitidis isolates, which are commonly present in asymptomatic pharyngeal carriage. However, in our study, sodC-based RT-PCR was 7.5% less sensitive than ctrA. Given the public health impact of possible false-negative results due to the use of the sodC target gene alone, sodC-based RT-PCR for the diagnosis of meningococcal meningitis should be used with caution.

Pharyngeal Colonization Dynamics of Haemophilus influenzae and Haemophilus haemolyticus in Healthy Adult Carriers

Haemophilus influenzae is an important cause of respiratory infections, including acute otitis media, sinusitis, and chronic bronchitis, which are preceded by asymptomatic H. influenzae colonization of the human pharynx. The aim of this study was to describe the dynamics of pharyngeal colonization by H. influenzae and an intimately related species, Haemophilus haemolyticus, in healthy adults. Throat specimens from four healthy adult carriers were screened for Haemophilus species; 860 isolates were identified as H. influenzae or H. haemolyticus based on the porphyrin test and on dependence on hemin and NAD for growth. Based on tests for hemolysis, for the presence of the 7F3 epitope of the P6 protein, and for the presence of iga in 412 of the isolates, 346 (84%) were H. influenzae, 47 (11%) were H. haemolyticus, 18 (4%) were nonhemolytic H. haemolyticus, and 1 was a variant strain. Carriers A and B were predominantly colonized with nontypeable H. influenzae, carrier C predominantly with b(-) H. influenzae mutants, and carrier D with H. haemolyticus. A total of 358 H. influenzae and H. haemolyticus isolates were genotyped by pulsed-field gel electrophoresis (PFGE) following SmaI or EagI digestion of their DNA, and the carriers displayed the following: carrier A had 11 unique PFGE genotypes, carrier B had 15, carrier C had 7, and carrier D had 10. Thus, adult H. influenzae and H. haemolyticus carriers are colonized with multiple unique genotypes, the colonizing strains exhibit genetic diversity, and we observed day-to-day and week-to-week variability of the genotypes. These results appear to reflect both evolutionary processes that occur among H. influenzae isolates during asymptomatic pharyngeal carriage and sample-to-sample collection bias from a large, variable population of colonizing bacteria.

Asymptomatic pharyngeal carriage of beta-haemolytic streptococci and streptococcal pharyngitis among patients at an urban hospital in Croatia

In a one-year study at the University Hospital of Infectious Diseases in Zagreb, Croatia the rate of asymptomatic throat carriage of beta-haemolytic streptococci was investigated. Throat carriage was investigated in 1796 patients, none of whom had a sore throat nor signs and/or symptoms of a respiratory tract infection. The carrier rate of beta-haemolytic streptococci was 8.3%, for group A streptococci 6%, group B 1.3%, group C 0.3% and group F 0.1%. The highest rate was observed in the 6 to 14 year age group: 13.8% for all streptococcal groups, 11.7% for group A alone. The proportion of non-A streptococci was higher in older age groups. Tonsillectomised individuals were less frequently carriers. No sex or season-dependent variations were observed. In a four-month study of 629 patients with pharyngitis the throat cultures yielded: group A streptococci in 44.7%, group B in 1.7%, group C in 0.8%, and group G in 0.6% of the patients. Group A streptococci in 44.7%, group B in 1.7%, group C in 0.8%, and group G in 0.6% of the patients. Group A streptococcal rates in carriers compared to rates in patients with pharyngitis suggest that approximately one fourth of the schoolchildren with culture-positive pharyngitis actually are not truly infected, but only carriers currently having a sore throat of non-streptococcal etiology. Antibiotics were administrated to 605 (96.2%) patients with pharyngitis; in 571 (94.4%) of the cases before culture results became available. After culture-negative results were obtained the therapy was discontinued in only 28.5% of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Group G Streptococcal Infections

The role of group G β-hemolytic streptococci (GGS) as significant human pathogens has been firmly established during the past 15 years. These organisms are normal inhabitants of the skin, oropharynx, and gastrointestinal and female genital tracts. Although cutaneous infections and pharyngitis are encountered most often, a wide variety of infections—including potentially life-threatening ones, such as septicemia, endocarditis, meningitis, peritonitis, pneumonitis, empyema, and septic arthritis—have been described.1 Asymptomatic pharyngeal carriage of GGS occurs in up to 23% of humans.2Symptoms of pharyngitis range from a mild upper respiratory tract infection with coryza to exudative pharyngitis accompanied by fever and lymphadenopathy. The illness is indistinguishable from that produced by group A streptococci, and there is no evidence that antimicrobial therapy modifies either the severity or the duration of symptoms.3Acute rheumatic fever following GGS pharyngitis has not been described. Type 12 M protein antigen, identical to the nephritogenic antigen

Methods for estimating the duration of bacterial carriage.

In two cohort studies on asymptomatic pharyngeal carriage of meningococci and of streptococci among schoolchildren, four methods are used to estimate the duration of bacterial carriage. A first estimate of the mean duration is given by the quotient of prevalence by incidence rate. A second method is based on the estimation of the actual length of truncated observations. A third estimate is given by the analysis of carriage survivorship according to a life table. A fourth method is the fitting of a negative exponential model to the carriage survival curve. For meningococci, the estimates of the median duration of carriage range from 7.7 up to 10.2 months, and from 11.1 up to 14.5 months for the mean. For streptococci, the median values vary from 1.9 up to 2.1 months, and from 2.3 up to 4.4 months for the mean duration. The validity and the consistency of the different estimates are discussed.