Carriage Of Streptococcus Research Articles

Invasive disease and paediatric carriage of Streptococcus pneumoniae in Ghana

This study was carried out primarily to evaluate the public health burden related to Streptococcus pneumoniae in Ghana and to provide related preliminary molecular epidemiological data on the organism. Invasive and nasopharyngeal specimens were screened for S. pneumoniae, and isolates were subjected to serotyping, multilocus sequence typing (MLST) and antibiotic susceptibility testing. Overall, the prevalence of S. pneumoniae in cerebrospinal fluid (CSF) was 1.7%, in blood was 0.2%, and in nasopharyngeal specimens was 15.3%. The prevalence of multiple drug resistance among the isolates was 48.6%, while the percentage resistance to various drugs was in the range of 11.1-84.0%. Serotyping of the S. pneumoniae isolates showed 7 different serotypes (3, 6B, 9, 10, 14, 16 and 23F). The extent of coverage of serotypes by the 7-valent pneumococcal conjugate vaccine was 57.1%, for the 10-valent vaccine was 57.1%, and for the 13-valent vaccine was 71.4%. MLST of 7 housekeeping genes of the organism showed a high level of genetic diversity among the isolates. S. pneumoniae appears to be an important organism in invasive infections in Ghana, being the most prevalent organism in CSF in this study. The high multiple drug resistance of the organism observed heightens the public health burden, which may be controlled by pneumococcal conjugate vaccines to a large extent.

Pneumococcal carriage is more common in asthmatic than in non‐asthmatic young men

The aim was to investigate the prevalence of oropharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Neisseria meningitidis and beta-haemolytic streptococci among asthmatic and non-asthmatic young Finnish men and to identify putative risk factors. A total of 224 asthmatics and 668 non-asthmatic men (mean age 19.6 years) from two intakes of conscripts to the Kainuu Brigade, Finland in July 2004 and January 2005 were enrolled upon entering military service. Oropharyngeal specimens were examined for bacteria by routine culture methods. All the participants filled in questionnaires concerning risk factors for asthma and respiratory infections. S. pneumoniae (48 cases, 5.4%), Group A streptococci (16, 1.8%), H. influenzae (45, 5.0%), M. catarrhalis (24, 2.7%) and N. meningitidis (20, 2.2%) were isolated from the 892 participants. Ten putative risk factors for oropharyngeal colonization (asthma, atopy, allergic rhinitis, smoking, current use of asthma medication, history of adeno/tonsillectomy, level of highly sensitive C-reactive protein, peak expiratory flow, results of a 12-min running test and body mass index) were evaluated. The only significant risk factor for S. pneumoniae carriage was asthma (OR, 2.04; 95% CI 1.12 to 3.72). Pneumococcal carriage is more common in asthmatic than in non-asthmatic young men.

Nasopharyngeal Carriage of Streptococcus pneumoniae in Gambian Children who Participated in a 9-valent Pneumococcal Conjugate Vaccine Trial and in Their Younger Siblings

Nasopharyngeal carriage of Streptococcus pneumoniae is extremely prevalent in The Gambia. We studied the effects of vaccination with pneumococcal conjugate vaccines on the carriage of individual serotypes and on antimicrobial resistance in vaccinated children and their younger siblings. A longitudinal study of a subsample of children (n=2342) who participated in a randomized, placebo controlled trial of a 9-valent pneumococcal conjugate vaccines (PCV-9) in The Gambia, and a cross-sectional study of non-PCV-9-vaccinated younger siblings (n=675). Recipients of PCV-9 were less likely to carry vaccine serotypes 4, 6B, 9V, 14, 19F, and 23F but more likely to carry vaccine-associated 19A and 9 nonvaccine serotypes at approximately 6 months postvaccination (age, 12 months) than were controls (each P<0.05). At approximately 16 months postvaccination, carriage of vaccine-associated-serotype 6A was also significantly reduced (P<0.01) while 3 other nonvaccine serotypes were more prevalent in the PCV-9 recipients (each P<0.05). At 16 months, but not 6 months, postvaccination PCV-9 recipients had lower rate of carrying isolates resistant to tetracycline and trimethoprim-sulfamethoxazole (TMP-SMZ) than controls (risk ratio: 0.90 and 0.95, respectively; each P<0.05). There was no difference in patterns of carriage of pneumococci in younger siblings of PCV-9 or placebo recipients. The effects of 9-valent pneumococcal conjugate vaccines on carriage of pneumococci persisted for at least 16 months postvaccination in Gambian children. Vaccination had no indirect effect on carriage in younger siblings and there was limited impact on antibiotic resistance.

Effect of vaccination with pneumococcal capsular polysaccharides conjugated to Haemophilus influenzae-derived protein D on nasopharyngeal carriage of Streptococcus pneumoniae and H. influenzae in children under 2 years of age

Following primary and booster vaccination with an 11-valent pneumococcall protein D conjugate vaccine there was a 42.8% (95% CI: −16.7 to 71.9, ns) reduction in the carriage of Streptococcus pneumoniae vaccine serotypes and a 42.6% (95% CI: 1.3–66.6) reduction in the carriage of Haemophilus influenzae identified by standard microbiological techniques. When PCR and immunoblot assays were used to further improve specificity of non-typeable H. influenzae strain identification, carriage of H. influenzae was still reduced with 38.6% (95% CI: −6.3 to 64.6, ns). Reduction of acute otitis media (AOM) episodes preceded the impact on carriage. These data provide further support of the functional role of the protein D immunity.

Risk factors for nasopharyngeal carriage of drug-resistant Streptococcus pneumoniae: data from a nation-wide surveillance study in Greece

BackgroundA nation-wide surveillance study was conducted in Greece in order to provide a representative depiction of pneumococcal carriage in the pre-vaccination era and to evaluate potential risk factors for carriage of resistant strains in healthy preschool children attending daycare centers.MethodsA study group was organized with the responsibility to collect nasopharyngeal samples from children. Questionnaires provided demographic data, data on antibiotic consumption, family and household data, and medical history data. Pneumococcal isolates were tested for their susceptibility to various antimicrobial agents and resistant strains were serotyped.ResultsBetween February and May 2004, from a total population of 2536 healthy children, a yield of 746 pneumococci was isolated (carriage rate 29.41%). Resistance rates differed among geographic regions. Recent antibiotic use in the last month was strongly associated with the isolation of resistant pneumococci to a single or multiple antibiotics. Serotypes 19F, 14, 9V, 23F and 6B formed 70.6% of the total number of resistant strains serotyped.ConclusionRecent antibiotic use is a significant risk factor for the colonization of otherwise healthy children's nasopharynx by resistant strains of S pneumoniae. The heptavalent pneumococcal conjugate vaccine could provide coverage for a significant proportion of resistant strains in the Greek community. A combined strategy of vaccination and prudent antibiotic use could provide a means for combating pneumococcal resistance.

Effect of Reduced-Dose Schedules With 7-Valent Pneumococcal Conjugate Vaccine on Nasopharyngeal Pneumococcal Carriage in Children

The effects of reduced-dose schedules of 7-valent pneumococcal conjugate vaccine (PCV-7) on pneumococcal carriage in children are largely unknown, although highly relevant in the context of subsequent herd effects. To examine the effects of a 2-dose and 2 + 1-dose PCV-7 schedule on nasopharyngeal pneumococcal carriage in young children compared with controls. A randomized controlled trial of nasopharyngeal carriage of Streptococcus pneumoniae enrolling 1003 healthy newborns and 1 of their parents in a general community in The Netherlands, with follow-up to age 24 months and conducted between July 7, 2005, and February 14, 2008. Infants were randomly assigned to receive 2 doses of PCV-7 at 2 and 4 months; 2 + 1 doses of PCV-7 at 2, 4, and 11 months; or no dosage (control group). Vaccine serotype pneumococcal carriage rates in infants in the second year of life. At 12 months, vaccine serotype pneumococcal carriage was significantly decreased after both PCV-7 schedules, with vaccine serotype pneumococcal carriage rates of 25% (95% confidence interval [CI], 20%-30%) and 20% (95% CI, 16%-25%) in the 2-dose and 2 + 1-dose schedule groups, respectively, vs 38% (95% CI, 33%-44%) in the control group (both P < .001). At 18 months, in the 2 + 1-dose schedule group, vaccine serotype pneumococcal carriage had further decreased to 16% (95% CI, 12%-20%) and, at 24 months, to 14% (95% CI, 11%-18%; both P < .001); whereas in the 2-dose schedule group, vaccine serotype pneumococcal carriage had remained stable at 18 months (24%; 95% CI, 20%-29%), but at 24 months had further decreased to 15% (95% CI, 11%-19%; both P < .001). In the control group, vaccine serotype pneumococcal carriage remained around 36% to 38% until 24 months. Compared with no pneumococcal vaccination, a 2 + 1-dose and 2-dose schedule of PCV-7 resulted in significant reductions of vaccine serotype pneumococcal carriage in the second year of life. clinicaltrials.gov Identifier: NCT00189020.

Transmission-dynamic model to capture the indirect effects of infant vaccination with Prevnar (7-valent pneumococcal conjugate vaccine (PCV7)) in older populations

We developed an age-structured, transmission-dynamic, mathematical model to quantify the direct and indirect benefits of infant PCV7 vaccination. The model simulates the acquisition of asymptomatic carriage of Streptococcus pneumoniae and the development of fatal and non-fatal invasive pneumococcal disease (IPD) among vaccinated and unvaccinated individuals aged <2, 2–4, 5–17, 18–49, 50–64, and ≥65 years old. The model was parameterized using published US surveillance data, supplemented with data from published literature. The model predicts the observed incidence of IPD with good agreement and may be used to predict the impact of various vaccination strategies in the US or other populations yet to introduce PCV7.

Estimation of vaccine efficacy against acquisition of pneumococcal carriage

Evaluation of the effect of new conjugate vaccines on nasopharyngeal carriage of Streptococcus pneumoniae (pneumococcus) has been based on simple comparisons of the prevalence of carriage in vaccinees and controls. However, the definition and measurement of vaccine efficacy should be based on knowledge of the actual mechanism of the vaccine's effect. According to current knowledge, conjugate vaccines affect acquisition. We propose a simple-to-use method to measure vaccine efficacy against serotype-specific acquisition that needs only cross-sectional measurements of carriage. We demonstrate the use of the method by application to a data set where it is also possible to estimate efficacy against acquisition from longitudinal measurements.

Editorial Commentary:Reduction of Carriage and Transmission ofStreptococcus pneumoniae:The Beneficial “Side Effect” of Pneumococcal Conjugate Vaccine

<i>Editorial Commentary:</i>Reduction of Carriage and Transmission of<i>Streptococcus pneumoniae:</i>The Beneficial “Side Effect” of Pneumococcal Conjugate Vaccine

Use of antibiotics and risk factors for carriage ofStreptococcus pneumoniae: a longitudinal household study in the United Kingdom

This study aimed to identify risk factors and assess the impact of coincidental antibiotic therapy on carriage of Streptococcus pneumoniae. Index children from birth to 3 years and their households were recruited from primary health-care registers in four UK general practices. Nasopharyngeal swabs were taken monthly from study participants ten times between October 2001 and July 2002. Multilevel random-effect models were used to adjust for statistical dependence between repeated measurements and family clustering of carriage. Carriage results were available for 3753 swabs from 489 individuals in 121 families. Crude prevalence of carriage was 25%. On multivariable analysis, risk of carriage was reduced by antibiotic use the previous month [odds ratio (OR) 0.34, 95% confidence interval (CI) 0.22-0.52], but increased if a child attended day care for >20 h per week (OR 2.52, 95% CI 1.41-4.52). Taking antibiotics significantly reduces the risk of carriage the following month in a setting with a low prevalence of pneumococcal antimicrobial resistance.

Epidemiologic Evidence for Serotype‐Specific Acquired Immunity to Pneumococcal Carriage

Nasopharyngeal carriage of Streptococcus pneumoniae is required for transmission of the bacteria and for invasive disease. There have been conflicting reports as to whether protection against carriage is serotype specific and which immune mechanisms drive carriage. Analyzing longitudinal carriage data from Israeli toddlers in day care, we found a lower risk of colonization with types 6A, 14, and 23F after previous exposure to the homologous type. Nonsignificant trends suggesting possible protection derived from prior exposure were found for types 19A and 23A. Furthermore, we found that, for types 14 and 23F, this specific protection correlated with increased serotype-specific antibody concentration. We found no evidence of specific protection for type 6B, group 15, or type 19F. Our findings imply that at least some serotypes generate anti-capsular antibodies that can reduce the risk of carriage in unimmunized toddlers.

Nasopharyngeal carriage of Streptococcus pneumoniae in healthy Turkish infants

The aims of this study were to determine nasopharyngeal carriage rates, serotype distribution and antimicrobial resistance patterns of Streptococcus pneumoniae in healthy 0 to 2 year-old infants who live within a rural or urban locale and not attending daycare centers. In order to evaluate the possible impact of pneumococcal conjugate vaccine in this population, coverage of the isolated serotypes by the vaccine was also calculated. The study was conducted on 564 healthy infants attending 2 different well child clinics, one of which is located in an urban region and the other in a rural region. Specimens were collected with nasopharyngeal swabs. Serotyping was performed with standard antisera. Penicillin susceptibility was determined with E-test. Chi-square tests and logistic regression were used for data analysis. The pneumococcal carriage rate was 22.5%. Age (>2 months age) [2.98 (1.41-6.29) p=0.004] and presence of another child within the house who attends school [1.72 (1.13-2.62) p=0.01] increased the carriage rate. The most frequently isolated serotypes were 11 (11.8%), 23 (7.9%), 19F (7.1%), 22 (6.3%), 9 (5.5%), 19 (5.5%) and 23B (5.5%). The total coverage of vaccine and vaccine-related serotypes by 7, 11 and 13 valent pneumococcal conjugate vaccines were 51.2, 59.0 and 59.0%, respectively. Of the isolated pneumococci, 10 (8.5%) were intermediately resistant and 8 (6.8%) were highly resistant to penicillin. This study provides data about the local carriage rate and serotype distribution of S. pneumoniae strains in Turkish children, which is important in predicting the possible effects of different valent pneumococcal conjugate vaccines in this population.

Nasopharyngeal Carriage of Streptococcus pneumoniae in Gambian Infants: A Longitudinal Study

To prepare for national introduction of a pneumococcal conjugate vaccine of restricted valency, we studied nasopharyngeal carriage of Streptococcus pneumoniae in Gambian infants. We studied 236 infants in 21 villages. We collected nasopharyngeal swab samples at birth, twice per month for 6 months, and every second month until 1 year of age. We studied time to acquisition and duration of pneumococcal carriage according to serotype. All infants carried S. pneumoniae at some point. Sixty-five serotypes were found, and the 5 most common serotypes (6B, 19F, 6A, 14, and 23F) accounted for 51% of isolates. The mean age at first acquisition of carriage was 33 days (95% confidence interval, 29-36 days). There were no significant differences in acquisition rates between the 6 most common serotypes (P = .067) or between vaccine serotypes, vaccine-related serotypes, or nonvaccine serotypes (P = .317). However, the duration of carriage differed significantly between the 6 most common serotypes (P = .004). The rate of reacquisition of carriage and the duration of carriage did not differ significantly between the 6 most common serotypes (P = .229 and P = .669 respectively). However, nonvaccine types were acquired faster (P = .004) and were carried for a shorter duration (P < .001) than were vaccine serotypes. A previous episode of serotype 14 carriage was associated with delayed reacquisition of this serotype (P = .005) and longer duration of carriage (P = .017). The data provided in this study regarding time to acquisition and duration of pneumococcal carriage in Gambian infants provide an important baseline for evaluating the impact of the introduction of a pneumococcal conjugate vaccine in The Gambia and elsewhere in Africa.

Prevalence and risk factors for nasopharyngeal carriage of Streptococcus pneumoniae among adolescents

Data on the prevalence of pneumococcal nasopharyngeal carriage and its risk factors among adolescents are scarce. The aim of this study was to provide such information. A cross-sectional, population-based prospective study was conducted. Participants were 1013 adolescents (age range 10-19 years) randomly recruited in 22 public schools. Those schools were randomly chosen among 307 public schools from 11 Sanitary Districts of Salvador, Brazil. Nasopharyngeal samples were assessed by standard procedures to recover and identify Streptococcus pneumoniae. Data on potential risk factors were gathered by confidential interview based on a standardized questionnaire. Pneumococci were recovered from 8.2 % [83/1013, 95 % confidence interval (CI) 6.6-10.0]. By stepwise logistic regression, pneumococcal colonization was independently associated with younger age [odds ratio (OR) 0.85, 95 % CI 0.77-0.94, P=0.001], being male (OR 1.78, 95 % CI 1.11-2.85, P=0.02), exposure to passive smoke in the household (OR 1.76, 95 % CI 1.10-2.79, P=0.02), having an upper respiratory infection during recruitment (OR 2.67, 95 % CI 1.67-4.28, P<0.001) and having a history involving an episode of acute asthma during the last year (OR 2.89, 95 % CI 1.18-7.08, P=0.03). The estimated probability of pneumococcal colonization decreased with age (chi(2) for trend=8.52, P=0.003). These findings provide tools for increasing the use of prevention strategies for pneumococcal diseases, such as pneumococcal vaccination among asthmatic patients and public health measures to stop smoking.

Pneumococcal Conjugate Vaccine Does Not Influence Staphylococcus aureus Carriage in Young Children with Acute Otitis Media

We investigated nasopharyngeal carriage of Streptococcus pneumoniae and Staphylococcus aureus among infants and young children with acute otitis media in a country where use of 7-valent pneumococcal conjugate vaccine (PCV7) has been progressively implemented. Among 1783 children enrolled, 60.8% carried S. pneumoniae, and 9% carried S. aureus. Among S. pneumoniae carriers, the rate of S. aureus carriage was 8.4%, compared with 9.9% among S. pneumoniae noncarriers. The rate of S. pneumoniae carriage in the PCV7-vaccinated population was lower (59.8%) than that observed in the nonvaccinated population (66.2%; P<.04). In contrast, in young children (age, <2 years) with acute otitis media, our study suggests that the S. aureus carriage rate is not affected by PCV7 immunization (9.0% in vaccinated children vs. 8.7% in nonvaccinated children). Furthermore, in children aged >1 year, the booster dose induces a sharp reduction in the carriage of vaccine serotypes of S. pneumoniae, without any change in S. aureus carriage.

The Challenge of Recalcitrant Acute Otitis Media

Recalcitrant acute otitis media (AOM), including 2 well-defined and sometimes related entities (persistent AOM and recurrent AOM), is a common pediatric problem. Episodes of AOM in children with either persistent or recurrent AOM were shown to be associated with recovery of middle ear fluid bacterial pathogens (particularly Streptococcus pneumoniae) with higher resistance to antibiotics compared with children with AOM not recently treated with antibiotics. The relationships between nasopharyngeal carriage of Streptococcus pneumoniae and persistence of middle ear fluid pathogens despite clinical improvement or cure and subsequent recurrence are discussed in depth. The findings emphasize the importance of bacteriologic eradication in the prevention of recurrent AOM episodes.

Nasal carriage of Streptococcus pneumoniae in healthy children and adults in northern Taiwan

A total of 427 subjects were surveyed for the carriage of Streptococcus pneumoniae before the introduction of pneumococcal conjugate vaccine in northern Taiwan. Positive results were identified in 27% of 94 children attending 6 classes in a child care center (CCC), 14% of 122 pupils attending 4 classes in 2 elementary schools, and 1.4% of 74 adolescents attending 3 classes in a junior middle school. None of 137 health care workers working in neonatal intensive care units of a university-affiliated hospital was colonized with S. pneumoniae. Three (12%) of 25 isolates from the children attending the CCC were susceptible to penicillin (MIC <0.1 μg/mL), whereas 8 (44%) of 18 isolates from the pupils and adolescents were susceptible ( P = 0.0312). Of the 43 isolates, 11 serotypes were identified and serotypes/serogroups 6 (13 isolates), 23 (10 isolates), and 19 (7 isolates) were the 3 most common serotypes/serogroups. The genotypes of the 43 isolates were diverse, but it was not infrequently seen that several isolates from the subjects in a single class shared a common genotype. Conclusively, the carriage rate of S. pneumoniae is inversely correlated with the age of the subjects. The isolates from the children attending the CCC had a significantly higher penicillin-nonsusceptible rate than those from the pupils and adolescents. Transmission of the same clone in a single class may have frequently occurred.

Streptococcus pneumoniae isolates in healthy children attending day-care centers in 12 states in Mexico

The aim of this study was to determine the prevalence of asymptomatic nasopharyngeal carriage of Streptococcus pneumoniae, which is a major factor in the transmission of this bacterium. Nasopharyngeal cultures were performed on children attending 32 day-care centers in 12 states in Mexico. Streptococcus pneumoniae was isolated from the nasopharynx of 829 out of 2,777(29.9%) subjects aged two months to six years. All children lived in urban areas and 80% spent more than six hours daily in a day-care center. Streptococcus pneumoniae serotypes most frequently identified were: 19F (23%), 6B (15.6%), 23F (11.2%) and 6A (14.9%). Thirty-six percent of the isolates were susceptible to penicillin. Serotype distribution suggests the possible benefits that could be obtained from the heptavalent pneumococcal conjugate vaccine.

Nasopharyngeal Carriage of Streptococcus pneumoniae in the elderly: a comparative assessment of detection methods

Nasopharyngeal Carriage of Streptococcus pneumoniae in the elderly: a comparative assessment of detection methods

Emergence of 19A as Virulent and Multidrug Resistant Pneumococcus in Massachusetts Following Universal Immunization of Infants With Pneumococcal Conjugate Vaccine

The long-term effects of selective pressure from conjugate pneumococcal vaccine on the serotype distribution and antimicrobial resistance of carriage and invasive isolates of Streptococcus pneumoniae are unknown. Early changes demonstrate a reduction in vaccine serotypes and an increase in nonvaccine serotypes (NVT) among both carriage and invasive isolates. Ongoing surveillance is necessary to identify emerging invasive serotypes and antimicrobial susceptibilities. Enhanced surveillance of invasive pneumococcal disease in Massachusetts began in October 2001 and remains ongoing. Isolates from children less than 5 are sent to the Massachusetts Department of Public Health and subsequently to the Maxwell Finland laboratory for serotyping and determination of antimicrobial susceptibility. Annual incidence rates for vaccine serotype and NVT disease are calculated using 2000 census data. NVT caused 72%-91% of invasive pneumococcal disease annually in children less than 5 years of age between 2002 and 2005. Serotype 19A has emerged as the most frequent cause of IPD in Massachusetts. A multidrug-resistant clone (ceftriaxone, amoxicillin, azithromycin and trimethoprim-sulfamethoxazole) (MLST 320) was first identified in Massachusetts in 2005. Three years after the introduction of pneumococcal conjugate vaccine for universal administration to children less than 2 in Massachusetts, a significant increase in invasive disease due to serotype 19A was observed. Although MLST 199 remains the most frequent sequence type among invasive isolates (of 19A), a multidrug-resistant sequence type, not previously identified in Massachusetts, has become an important cause of invasive disease. Further surveillance of the changing ecology of S. pneumoniae is necessary as a 4-year time period is not sufficient to fully evaluate the impact of PCV of pneumococcal infections.