Prevalence, determinants, and molecular epidemiology of Streptococcus pneumoniae isolates colonizing the nasopharynx of healthy children in Rome

Risk factors associated with Streptococcus pneumonia carriage in children under five years old with acute respiratory infection in Niger

Introduction

Streptococcus pneumonia is a leading cause of bacterial pneumonia, meningitis and sepsis in children, and pneumococcal carriage is an important source of horizontal spread of these pathogens within the community.

Methods

A questionnaire was addressed to parents for the collection of sociodemographic and medical information. Nasopharyngeal swabbing was processed using a molecular method. We used logistic regression models to examine independent associations between pneumococcal carriage and potential risk factors. All associations with a p-value of < 0.25 in the bivariate regression analyses were subsequently entered in the multivariate regression model.

Results

A total of 637 children aged 1 to 59 months admitted for acute respiratory infection were included. The rate of respiratory virus carriage was 76%, whereas that of bacteria was 47% and that of bacteria-virus co-colonization was 42%. A bivariate analysis showed that carriage was not related to gender, father's or mother's education level, father's occupation, type of housing or lighting, or passive exposure to cigarette smoking in the house. It was also not linked to complete vaccination with PCV-13 or PPSV-23 and antibiotic treatment prior to hospitalization. A multivariate analysis showed that carriage was related to age greater than 3 months, maternal occupation, house flooring type, and co-colonization of another bacterium and virus.

Conclusion

These results can be helpful to understand the dynamics of pneumococcal nasopharyngeal colonization; they confirm the interest of vaccinating infants before the age of 3 months with appropriate vaccine to prevent spread nasopharyngeal colonization and pneumococcal diseases in children.

Pneumococcal conjugate vaccine use during humanitarian crises

Streptococcus pneumoniae is a common human commensal that causes a sizeable part of the overall childhood mortality in low income settings. Populations affected by humanitarian crises are at especially high risk, because a multitude of risk factors that are enhanced during crises increase pneumococcal transmission and disease severity. Pneumococcal conjugate vaccines (PCVs) provide effective protection and have been introduced into the majority of routine childhood immunisation programmes globally, though several barriers have hitherto limited their uptake during humanitarian crises. When PCV coverage cannot be sustained during crises or when PCV has not been part of routine programmes, mass vaccination campaigns offer a quick acting and programmatically feasible bridging solution until services can be restored. However, we currently face a paucity of evidence on which to base the structure of such campaigns. We believe that, now that PCV can be procured at a substantially reduced price through the Humanitarian Mechanism, this lack of information is a remaining hurdle to PCV use in humanitarian crises. Considering the difficulties in conducting research in crises, we propose an evidence generation pathway consisting of primary data collection in combination with mathematical modelling followed by quasi-experimental evaluation of a PCV intervention, which can inform on optimal vaccination strategies that consider age targeting, dosing regimens and impact duration.

[Antibiotic susceptibility of Staphylococcus aureus and Streptococcus pneumoniae in healthy carrier individuals in primary care in Barcelona area]

Introducción

La información existente sobre la resistencia a los antibióticos se basa habitualmente en muestras de personas hospitalizadas. El objetivo fue evaluar la prevalencia de resistencia antibiótica de cepas de Staphylococcus aureus y Streptococcus pneumoniae de personas portadores nasales atendidas en las consultas de atención primaria según edad y sexo.

Diseño

Estudio transversal.

Emplazamiento

Siete centros de salud del área de Barcelona.

Participantes

Personas portadoras nasales a partir de 4 años de edad, sin signos de enfermedad infecciosa y que no habían tomado antibióticos ni habían estado hospitalizados en los 3 meses anteriores.

Mediciones principales

Se recogieron 3.969 frotis nasales válidos para identificación entre 2010 y 2011 y fueron enviados a un laboratorio central de microbiología para el aislamiento de ambos gérmenes. La resistencia a los antibióticos se estableció según los puntos de corte actuales de la guía del European Committee on Antimicrobial Susceptibility Testing.

Resultados

La prevalencia de S. aureus resistente a meticilina fue del 1,3% (IC 95%: 0,5-2,1%), con porcentajes de resistencia frente a fenoximetilpenicilina del 87,1% y a azitromicina del 11,6%, sin observar diferencias significativas según edad y sexo. Un 2,4% (IC 95%: 0,1-4,7%) de las cepas de neumococo fueron altamente resistentes a fenoximetilpenicilina y macrólidos, mientras que las mayores resistencias se observaron frente a cefaclor (53,3%), tetraciclina (20%) y cefuroxima (12,1%).

Conclusiones

Estos patógenos tienen resistencias más bajas en la comunidad que las que se observan en el medio hospitalario. Es importante que se conozca la resistencia antibiótica actual para poder hacer un uso más prudente de los antibióticos.

Antibiotic resistance of Streptococcus pneumoniae, isolated from nasopharynx of preschool children with acute respiratory tract infection in Lithuania

BACKGROUND

Increasing pneumococcal resistance to commonly used antibiotics and multidrug resistance is a serious public health concern. Data on distribution of resistant Streptococcus pneumoniae (SPn) strains among children in Lithuania are limited. We evaluated the circulation of SPn serotypes and antimicrobial susceptibility among preschool children in Lithuania before the introduction of universal infant pneumococcal vaccination.

METHODS

A prospective study was carried out from February 2012 to March 2013 in five cities of Lithuania. A total of 900 children under six years of age who presented to primary care centre or a hospital emergency department with acute respiratory tract infection were enrolled in the study. Nasopharyngeal swabs were obtained and cultured for SPn. Positive samples (n = 367) were serotyped and tested for antimicrobial susceptibility. Associations of pneumococcal non-susceptibility with study site, season, age, sex, attendance of day care centre and treatment with antimicrobials (between one and six months prior the study) were evaluated.

RESULTS

About a half (56.7 %) of SPn strains were susceptible to all the antibiotics tested. Pneumococcal non-susceptibility to penicillin, erythromycin, clindamycin and trimethoprim-sulphamethoxazole was 15.8, 21.3, 16.9 and 27.3 %, respectively. None of the tested isolates was resistant to norfloxacin or vancomycin. We found a geographical variation of pneumococcal resistance within the cities of the country. Age, sex, the attendance of day care centre and treatment with antimicrobials prior the study was not significantly associated with a carriage of non-susceptible SPn strains. Among non-susceptible SPn serotypes 67.9 %-82.4 % were present in currently available pneumococcal conjugate vaccines.

CONCLUSIONS

The rates of nasopharyngeal SPn susceptibility to penicillin and macrolides are still high among preschool children in Lithuania, however they are lower compared with previous studies. A strict policy with respect to antibiotic prescription together with widespread use of vaccination could potentially reduce the carriage rate of antibiotic-resistant pneumococci in our country.

Streptococcus pneumoniae nasopharyngeal colonisation in children aged under six years with acute respiratory tract infection in Lithuania, February 2012 to March 2013

serotypes among children in Lithuania are limited. A prospective study was carried out from February 2012 to March 2013 to evaluate the circulation of SPn serotypes among young children in five cities of Lithuania before the introduction of universal vaccination with pneumococcal conjugate vaccine (PCV). A total of 900 children under six years of age who presented to primary care centres or a hospital emergency department with acute respiratory tract infection (RTI) were enrolled in the study. The SPn colonisation rate was40.8% (367/900), with a peak at two and three years old(48.8% and 45.4%, respectively). Of the 367 SPn isolates, the most common serotypes were 6B (15.8%,n = 58), 19F (13.9%, n = 51), 23F (13.9%, n = 51), 15(10.1%, n = 37), 14 (9.5%, n = 35), 6A (9.3%, n= 34),11 (4.6%, n = 17), 3 (3.0%, n = 11) and 18C (3.0%, n =11); less frequent were 23 (non-23F) (2.7%, n = 10), 19A(2.2%, n = 8) and 9V (1.6%, n = 6). Serotypes 6A and 11 were more common in children under two years-old;18C was found only in children aged two to five years.The serotypes found might be an important predictor of the likely effectiveness of the PCVs currently available in Lithuania

Risk Factors for Pneumococcal Colonization of the Nasopharynx in Alaska Native Adults and Children

BACKGROUND

Alaska Native children have high invasive pneumococcal disease (IPD) rates, and lack of in-home running water has been shown to have a significant association with infection. Pneumococcal conjugate vaccines reduced IPD; however, this population saw substantial replacement disease and colonization with nonvaccine serotypes. We evaluated risk factors for nasopharyngeal pneumococcal colonization in Alaska Native adults and children.

METHODS

We conducted annual surveys from 2008 through 2011 of residents of all ages in 8 rural Alaskan villages. Interviews were conducted, medical charts were reviewed, and nasopharyngeal swabs were cultured for Streptococcus pneumoniae. Multivariate logistic regression models were developed for 3 age groups (under 10 years, 10-17 years, and 18 years and older) to determine risk factors for colonization.

RESULTS

We obtained 12 535 nasopharyngeal swabs from 4980 participants. Our population lived in severely crowded conditions, and 48% of households lacked in-home running water. In children <10 years, colonization was associated with lack of in-home running water, household crowding, and more children in the home. Pneumococcal vaccination status was not associated with colonization. In older children and adults, increased number of persons in the household was associated with pneumococcal colonization.

CONCLUSIONS

Higher colonization prevalence may partially explain increased IPD rates seen in those lacking in-home water services. Improving availability of sanitation services and reducing household crowding may reduce the burden of IPD in this population.

Serotype distribution and antimicrobial susceptibilities of nasopharyngeal isolates of Streptococcus pneumoniae from healthy children in the 13-valent pneumococcal conjugate vaccine era

Few epidemiological data are available since the introduction of 13-valent pneumococcal vaccine (PCV13) in 2010. We conducted a cross-sectional study to estimate the prevalence of Streptococcus pneumoniae (SP) nasopharyngeal carriage in healthy Italian infants and young children and to evaluate the impact of PCV13 on pneumococcal colonization. In the trimester September-December 2011 nasopharyngeal swabs were collected from healthy children aged 3-59 months presenting for routine well careat 16 primary care pediatricians in Milan. SP carriage isolates were serotyped and tested for antimicrobial resistance using EUCAST breakpoints. Among 1250 enrolled children, 618 had received at least 1 dose of PCV13, 292 at least 1 dose of PCV7, 94 a combination of the two vaccines and 246 were not vaccinated. The prevalence of SP carriage was 27% (95% confidence interval [CI] 25-30). At multivariable analysis, age≥25 months (prevalence ratio [PR]=0.74) and use of antibiotics in the previous 3 months (PR=0.67) were associated with lower SP carriage prevalence. Having siblings (PR=1.79 for 1 sibling and PR=2.23 for ≥2 siblings), day-care attendance (PR=2.27) and respiratory tract infections in the previous 3 months (PR=1.39) were associated with higher SP carriage prevalence. The immunization status for SP was not associated with SP carriage at univariable or at multivariable analysis. The most common carriage isolates were 6C, 19A and 23A. The prevalence of the six additional PCV13 serotypes carriage in children appropriately vaccinated with PCV13 was lower than in children appropriately vaccinated with PCV7 (0 vs. 0.060); the greater reduction in prevalence of carriage was observed for serotype 19A (0 vs. 0.041). Serotype 6C was the most common drug-resistant serotype (17.2%). Further epidemiological studies are needed to assess changes in circulating SP serotypes following the large-scale introduction of PCV13.

Pneumococcal carriage in young children one year after introduction of the 13-valent conjugate vaccine in Italy

BACKGROUND

In mid 2010, the 7-valent pneumococcal conjugate vaccine (PCV7) was replaced by the 13-valent conjugate vaccine (PCV13) for childhood immunization in Italy. Our objective in this study was to obtain a snapshot of pneumococcal carriage frequency, colonizing serotypes, and antibiotic resistance in healthy children in two Italian cities one year after PCV13 was introduced.

METHODS

Nasopharyngeal swabs were obtained from 571 children aged 0-5 years from November 2011-April 2012. Pneumococcal isolates were serotyped and tested for antimicrobial susceptibility. Penicillin and/or erythromycin non-susceptible isolates were analyzed by Multi Locus Sequence Typing (MLST).

RESULTS

Among the children examined, 81.2% had received at least one dose of PCV7 or PCV13 and 74.9% had completed the recommended vaccination schedule for their age. Among the latter, 57.3% of children had received PCV7, 27.1% PCV13, and 15.6% a combination of the two vaccines. The overall carriage rate was 32.9%, with children aged 6-35 months the most prone to pneumococcal colonization (6-23 months OR: 3.75; 95% CI: 2.19-6.43 and 24-35 months OR: 3.15, 95%CI: 2.36-4.22). A total of 184 pneumococcal isolates were serotyped and divided into PCV7 (5.4%), PCV13 (18.0%), and non-PCV13 (82.0%) serotypes. Serotypes 6C, 24F, and 19A were the most prevalent (10.3%, 8.6%, and 8.1%, respectively). The proportion of penicillin non-susceptible (MIC >0.6 mg/L) isolates was 30.9%, while 42.3% were erythromycin resistant. Non-PCV13 serotypes accounted for 75.4% and 70.8% of the penicillin and erythromycin non-susceptible isolates, respectively.

CONCLUSIONS

Our results revealed low rates of PCV7 and PCV13 serotypes in Italian children, potentially due to the effects of vaccination. As the use of PCV13 continues, its potential impact on vaccine serotypes such as 19A and cross-reactive serotypes such as 6C will be assessed, with this study providing a baseline for further analysis of surveillance isolates.

Nasopharyngeal swabs of school children, useful in rapid assessment of community antimicrobial resistance patterns in Streptococcus pneumoniae and Haemophilus influenzae

OBJECTIVES

The present study evaluates the feasibility of rapid surveillance of community antimicrobial resistance (AMR) patterns of Streptococcus pneumoniae and Haemophilus influenzae in India using nasopharyngeal swabs (NPSs) of school children. It compares the AMR data obtained with that of invasive and nasopharyngeal (NP) isolates studied previously. No one has done such surveillance since our study so we decided to publish and more clearly demonstrate the feasibility of the methodology we did.

STUDY DESIGN AND SETTING

This community-based, cross-sectional, cluster sample study had seven centers; each had two sites distant to them. Two hundred sixty school children per center were enrolled. NP swabbing was performed and isolates identified as S. pneumoniae and H. influenzae at each center were sent to reference laboratories.

RESULTS

From January to December 2004, 1,988 NP swabs were processed; 776 S. pneumoniae and 64 H. influenzae were isolated. The AMR patterns for S. pneumoniae to co-trimoxazole varied, with sensitivity as low as 6% in Mumbai, 29% in Chennai and Vellore, and 100% in Delhi and Lucknow. For H. influenzae, sensitivity rates to co-trimoxazole ranged from 22% to 62%. The AMR patterns for both bacteria in the present study with data from invasive and NP isolates studied earlier were similar.

CONCLUSION

The study demonstrates that it is practical and feasible to rapidly assess the AMR patterns of both S. pneumoniae and H. influenzae in NPSs of school children in different geographic locations all over India.

Dynamics of pneumococcal nasopharyngeal carriage in healthy children attending a day care center in northern Spain. Influence of detection techniques on the results

BACKGROUND

Pneumococcal nasopharyngeal carriage precedes invasive infection and is the source for dissemination of the disease. Differences in sampling methodology, isolation or identification techniques, as well as the period (pre -or post-vaccination) when the study was performed, can influence the reported rates of colonization and the distribution of serotypes carried.

OBJECTIVES

To evaluate the prevalence and dynamics of pneumococcal nasopharyngeal colonization in healthy children aged 6-34 months attending a day care center with a high level of hygiene and no overcrowding. The study was performed 3-4 years after the 7-valent pneumococcal vaccine was introduced, using multiple methodologies to detect and characterize the isolates.

METHODS

Over 12 months, 25 children were sampled three times, 53 children twice and 27 children once. Three Streptococcus pneumoniae typing techniques were used: Quellung, Pneumotest-Latex-kit and multiplex-polymerase chain reaction (PCR). The similarity of isolates of the same serotype was established by pulsed field gel electrophoresis (PFGE) and occasionally the multilocus sequence type (ST) was also determined.

RESULTS

Overall pneumococcal carriage and multiple colonization rates were 89.5% (94/105) and 39%, respectively. Among 218 pneumococci detected, 21 different serotypes and 13 non-typeable isolates were found. The most prevalent serotypes were 19A, 16F and 15B. Serotypes 15B, 19A and 21 were mainly found as single carriage; in contrast serotypes 6B, 11A and 20, as well as infrequent serotypes, were isolated mainly as part of multiple carriage. Most 19A isolates were ST193 but most serotypes showed high genetic heterogeneity. Changes in the pneumococci colonizing each child were frequent and the same serotype detected on two occasions frequently showed a different genotype. By multiplex-PCR, 100% of pneumococci could be detected and 94% could be serotyped versus 80.3% by the Quellung reaction and Pneumotest-Latex in combination (p < 0.001).

CONCLUSIONS

Rates of S. pneumoniae carriage and multiple colonization were very high. Prevalent serotypes differed from those found in similar studies in the pre-vaccination period. In the same child, clearance of a pneumococcal strain and acquisition of a new one was frequent in a short period of time. The most effective technique for detecting pneumococcal nasopharyngeal carriers was multiplex-PCR.

Crowding and other strong predictors of upper respiratory tract carriage of otitis media-related bacteria in Australian Aboriginal and non-Aboriginal children

BACKGROUND

Streptococcus pneumoniae, Moraxella catarrhalis, and nontypeable Haemophilus influenzae is associated with otitis media (OM). Data are limited on risk factors for carriage of these pathogens, particularly for Indigenous populations. We investigated predictors of nasopharyngeal carriage in Australian Aboriginal and non-Aboriginal children.

METHODS

Nasopharyngeal aspirates were collected up to 7 times before age 2 years from 100 Aboriginal and 180 non-Aboriginal children. Longitudinal modeling estimated effects of environmental factors and concurrent carriage of other bacteria on the probability of bacterial carriage. We present a novel method combining the effects of number of household members and size of house into an overall crowding model.

RESULTS

Each additional household member increased the risk of carriage of S. pneumoniae (odds ratio [OR] = 1.45 per additional Aboriginal child in a 4-room house, 95% confidence interval [CI]: 1.15-1.84; OR = 2.34 per additional non-Aboriginal child, 95% CI: 1.76-3.10), with similar effect sizes for M. catarrhalis, and nontypeable Haemophilus influenzae. However, living in a larger house attenuated this effect among Aboriginal children. Daycare attendance predicted carriage of the 3 OM-associated bacteria among non-Aboriginal children. Exclusive breast-feeding at 6 to 8 weeks protected against Streptococcus aureus carriage (OR = 0.42, 95% CI: 0.19-0.90 in Aboriginal children and OR = 0.49, 95% CI: 0.25-0.96 in non-Aboriginal children). OM-associated bacteria were more likely to be present if there was concurrent carriage of the other OM-associated species.

CONCLUSIONS

This study highlights the importance of household transmission in carriage of OM bacteria, underscoring the need to reduce the crowding in Aboriginal households.

Prevalence of nasopharyngeal carriage of pneumococcus in preschool children attending day care in London

OBJECTIVE

To estimate the prevalence of nasopharyngeal (NP) carriage of pneumococcus (Streptococcus pneumoniae) and describe the antibiotic resistance patterns and serotypes in young children attending group day care in London.

DESIGN AND SUBJECTS

Cross-sectional survey of attendees at a sample of registered child day care centres (CDCCs) in a London borough.

SETTING

Urban setting with a socially and culturally diverse population.

METHODS AND OUTCOMES

19 CDCCs (13% of total) participated between March and November 2003. A single NP swab was required from each child, and parents completed a questionnaire about their child's health and attendance at day care. WHO methodology for pneumococcal carriage studies was followed.

RESULTS

30% of parents consented. 234 swabs were collected from children aged 6 months to 5 years. 53% were boys and 81% were white. 120 children (51%, 95% CI 45% to 58%) carried pneumococci in their nasopharynx. None of the isolates were resistant to penicillin (upper CL 3%). 21 isolates were resistant to erythromycin (17.5%, 95% CI 11% to 25.5%). 68 isolates (57%) were serotypes included in the 7-valent conjugate vaccine. Non-white children had a lower prevalence of carriage (27% vs 58%).

CONCLUSION

The prevalence of pneumococcal NP carriage was high. The penicillin resistance rate is lower than in many other countries and may reflect a decrease in community antibiotic prescribing in the UK. Monitoring circulating serotypes is important in the context of recent changes to the vaccination policy. Further study is required to explore the association with ethnicity and risk factors for antibiotic resistance.

Increasing penicillin and trimethoprim-sulfamethoxazole resistance in nasopharyngeal Streptococcus pneumoniae isolates from Guatemalan children, 2001--2006

OBJECTIVES

We aimed to determine nasopharyngeal colonization rates and antibiotic resistance patterns of Streptococcus pneumoniae isolated from Guatemalan children, and to determine risk factors for colonization and antibiotic nonsusceptibility.

METHODS

Isolates were obtained from children aged 5 to 60 months attending public and private outpatient clinics and daycare centers during August 2001--June 2002 and outpatient clinics during November 2005--February 2006 in Guatemala City. Minimal inhibitory concentrations of penicillin, trimethoprim-sulfamethoxazole (TMS), cefotaxime, and erythromycin were determined using the E-test.

RESULTS

The overall nasopharyngeal colonization rate for S. pneumoniae was 59.1%. From 2001/2 to 2005/6 TMS nonsusceptibility increased from 42.4% to 60.8% (p<0.05) in public clinics and from 51.4% to 84.0% (p=0.009) in private clinics, and penicillin nonsusceptibility increased from 1.5% to 33.3% in public clinics (p<0.001). Reported antibiotic use was not strictly associated with nonsusceptibility to that same antibiotic. Resistance to three or four antibiotics increased in public clinics from 2001/2 (0%) to 2005/6 (10.7%; p<0.001). Risk factors for nasopharyngeal colonization with penicillin- or TMS-nonsusceptible S. pneumoniae were low family income, daycare center attendance, and recent penicillin use.

CONCLUSIONS

Increasing antibiotic nonsusceptibility rates in nasopharyngeal S. pneumoniae isolates from Guatemalan children reflect worldwide trends. Policies encouraging more judicious use of TMS should be considered.

Antimicrobial susceptibility of Streptococcus pyogenes and Streptococcus pneumoniae: surveillance from 1993 to 2004 in Central Italy

The susceptibility of 1870 Streptococcus pyogenes and 1595 Streptococcus pneumoniae to macrolides and lincosamides has been monitored from 1993 to 2004 in Central Italy. Among S. pyogenes, 30.2% were erythromycin resistant; 18.5% were also resistant to josamycin and clindamycin (MLS phenotype). After an increasing erythromycin resistance rate in 1993-1997 (maximum 53.16%), a definite decrease was observed since 2001 with resistance rates always less than 30%. Thirty six percent of pneumococcal isolates were erythromycin-resistant, with minor temporal fluctuations; the MLS phenotype was the most prevalent overall (32.6%) and in individual years. S. pneumoniae strains were also tested for susceptibility to beta-lactams and other antimicrobial agents: 11.2% were penicillin non-susceptible, with a gradually increasing prevalence after 2001 (maximum rate 17.3% in 2004), 31.15% were resistant to tetracycline, 4.9% to chloramphenicol, 0.74% to rifampin. All pneumococcal isolates were susceptible to teicoplanin and 99.9% to ceftriaxone and ofloxacin.

Zinc metalloproteinase genes in clinical isolates of Streptococcus pneumoniae: association of the full array with a clonal cluster comprising serotypes 8 and 11A

Pneumococci display large zinc metalloproteinases on the surface, including the IgA protease, which cleaves human IgA1 in the hinge region, the ZmpC proteinase, which cleaves human matrix metalloproteinase 9 (MMP-9), and two other proteinases, ZmpB and ZmpD, whose substrates have not yet been identified. Surface metalloproteinases are antigenic and have been linked to virulence. The genes encoding these proteinases reside in three distinct loci: two loci specific for zmpB and zmpC, and a third, the iga locus, containing iga and zmpD. Data obtained by this and other groups have shown that pneumococcal metalloproteinase genes are transcribed and yield mature and enzymatically active proteins. Since the presence of the four proteinase genes is variable in the pneumococcal strains whose genomes have been sequenced, the presence of these genes in a collection of 218 pneumococcal isolates, mostly from invasive disease, was investigated. The data showed that zmpB and iga were present in all the isolates examined, while zmpC and zmpD were present in a variable proportion of the isolates (in 18 and 49 %, respectively). Interestingly, isolates carrying both zmpC and zmpD were found to belong mainly to two serotypes (sts), 8 and 11A. By molecular typing, st 8 and st 11A isolates appeared to belong to the same clonal cluster. The presence of these two additional metalloproteinases could contribute to the fitness of particular pneumococcal clones.

Natural history of drug-resistant clones of Streptococcus pneumoniae colonizing healthy children in Portugal

A total of 3,539 Streptococcus pneumoniae (Pn) were recovered from 4,969 nasopharyngeal samples of children attending 13 day-care centers (DCCs) located in Lisbon, Portugal, during a surveillance study from January, 2001, through March, 2003, integrated in the European intervention project (EURIS, European Resistance Intervention Study). All Pn isolates were tested for anti-biotyping and drug-resistant pneumococci (DRPn) were further tested by serotyping and pulsed-field gel electrophoresis (PFGE). Overall carriage of Pn was very high (71.2%) and 39.9% of the isolates were resistant to antimicrobials (22.5% with decreased susceptibility to penicillin and 17.4% susceptible to penicillin and resistant to other antimicrobials). Serotypes 6B, 14, 23 F, 19F, and 19 A were prevalent among the 1,287 DRPn and 5.8% of the isolates were non-typeable. Eighty PFGE patterns were identified among 1,285 DRPn, and 93.1% of the DRPn belonged to 26 major clonal types that comprised: Pneumococcal Molecular Epidemiology Network (PMEN) clones (76.3%), Portuguese (PT)-DCC clones, previously detected in 1996-1999 (14.3%), and EURIS PT-DCC new clones, identified for the first time in the EURIS study, during 2001-2003 (9.4%). Comparing with previous Portuguese surveillance studies carried out since 1996, we observed that carriage increased from 47% to 71%, but no major changes were detected on the prevalence of pneumococcal serotypes. Moreover, although PMEN clones were predominant in all DCCs, in the present study the majority of them were gradually decreasing in time whereas several PT-DCC and new clones seemed to be increasing.

Assessment of a rapid urinary antigen detection by an immunochromatographic test for diagnosis of pneumococcal infection in children

The aim of the study was to evaluate the Binax Now rapid immunochromatographic test (ICT) for the detection of Streptococcus pneumoniae urinary antigen in children suffering from potentially pneumococcal infections. A total of 287 patients, with a median age of 34.9 months and divided into 3 groups, were studied; the first group of patients with a suspected pneumococcal infection (n = 112), the second group with infectious symptoms nonsuggestive of a pneumococcal infection (n = 54), and the third group was composed of asymptomatic children (n = 121). In group 1, sensitivity of ICT was 100% and specificity was 55.9% (95% confidence interval, 44.1- 67.7). Forty-six (85.1%) patients from the second group were true negatives. Twenty-five (20.7%) patients from the third study group were nasopharyngeal pneumococcal carriers, and the ICT was positive in 13 carriers (10.7%). The high sensitivity level of ICT in our study indicates that a negative test could rule out a pneumococcal infection, contrasted with a poor specificity.

A cross-sectional survey of the prevalence of Streptococcus pneumoniae nasopharyngeal carriage in Belgian infants attending day care centres

Nasopharyngeal carriage is a major factor in the transmission of pneumococcal disease. The aim of this study was to determine the prevalence of asymptomatic nasopharyngeal carriage of Streptococcus pneumoniae and the distribution of serogroups and serotypes in children aged 3-36 months attending day care centres in Belgium. A single nasopharyngeal swab was cultured from 467 children attending 30 different day care centres between December 2000 and March 2001. S. pneumoniae isolates were serotyped and their antibiotic susceptibilities assessed by disk diffusion. The overall nasopharyngeal carriage rate for S. pneumoniae was 21% in the 467 children. None of the commonly accepted risk factors studied was associated significantly with carriage. Capsular serotypes isolated were 19F (27.3%), 6B (20.2%), 23F (19.2%), 19A (10.1%), 6A (7.1%), 14 (5.1%) and others (11.0%). Theoretical coverage by the seven-valent (serotypes 4, 6B, 9V, 14, 18C, 19F and 23F) pneumococcal conjugate vaccine was 73.7%. Fourteen (14.1%) of 99 strains were non-susceptible to penicillin, 48 (48.5%) to tetracycline and 61 (61.6%) to erythromycin. Theoretical coverage by the seven-valent pneumococcal conjugate vaccine was 93% for the penicillin-resistant serotypes, 69% for the tetracycline-resistant serotypes and 75% for the erythromycin-resistant serotypes. Use of the seven-valent pneumococcal conjugate vaccine could potentially reduce nasopharyngeal carriage of the antibiotic-resistant strains.

Tn2009, a Tn916-like element containing mef(E) in Streptococcus pneumoniae

The association between the macrolide efflux gene mef(E) and the tet(M) gene was studied in two clinical strains of Streptococcus pneumoniae that belonged to serotypes 19F and 6A, respectively, and that were resistant to both tetracycline and erythromycin. The mef(E)-carrying element mega (macrolide efflux genetic assembly; 5,511 bp) was found to be inserted into a Tn916-like genetic element present in the chromosomes of the two pneumococcal strains. In both strains, mega was integrated at the same site, an open reading frame identical to orf6 of Tn916. The new composite element, Tn2009, was about 23.5 kb and, with the exception of the tet(M)-coding sequence, appeared to be identical in both strains. By sequencing of the junction fragments of Tn2009 at the site of insertion into the chromosome, it was possible to show that (i) the insertion site was identical in the two clinical strains and (ii) the integration of Tn2009 caused a 9.5 kb-deletion in the pneumococcal chromosome. It was not possible to detect the conjugal transfer of Tn2009 to a recipient pneumococcal strain; however, transfer of the whole element by transformation was shown to occur. It is possible to hypothesize that Tn2009 relies on transformation for its spread among clinical strains of S. pneumoniae.

Streptococcus pneumoniae colonisation: the key to pneumococcal disease

Streptococcus pneumoniae is an important pathogen causing invasive diseases such as sepsis, meningitis, and pneumonia. The burden of disease is highest in the youngest and oldest sections of the population in both more and less developed countries. The treatment of pneumococcal infections is complicated by the worldwide emergence in pneumococci of resistance to penicillin and other antibiotics. Pneumococcal disease is preceded by asymptomatic colonisation, which is especially high in children. The current seven-valent conjugate vaccine is highly effective against invasive disease caused by the vaccine-type strains. However, vaccine coverage is limited, and replacement by non-vaccine serotypes resulting in disease is a serious threat for the near future. Therefore, the search for new vaccine candidates that elicit protection against a broader range of pneumococcal strains is important. Several surface-associated protein vaccines are currently under investigation. Another important issue is whether the aim should be to prevent pneumococcal disease by eradication of nasopharyngeal colonisation, or to prevent bacterial invasion leaving colonisation relatively unaffected and hence preventing the occurrence of replacement colonisation and disease. To illustrate the importance of pneumococcal colonisation in relation to pneumococcal disease and prevention of disease, we discuss the mechanism and epidemiology of colonisation, the complexity of relations within and between species, and the consequences of the different preventive strategies for pneumococcal colonisation.

Phenotypic and genotypic characterization of two penicillin-susceptible serotype 6B Streptococcus pneumoniae clones circulating in Italy

Twenty-nine penicillin-susceptible serotype 6B strains isolated from patients with invasive diseases and from healthy carriers were examined by different genotyping methods. Ten groups were identified on the basis of the pulsed-field gel electrophoresis (PFGE) profiles, and two of these contained multiple isolates and were analyzed further. PFGE group 1 comprised 12 isolates, the majority of which had a multiresistant phenotype (resistance to erythromycin, clindamycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole), corresponding to that of a clone previously described in the Mediterranean area and related to penicillin-resistant clone Spain(6B)-2. The pbp2b, pbp2x, dhf, and pspA genes of the isolates had identical restriction profiles; and the partial sequence of pspA was identical to that of clone Spain(6B)-2. In all isolates the resistance determinants erm(B) and tet(M) were inserted in a Tn1545-like element; 11 isolates carried cat as part of the integrated plasmid pC194. Multilocus sequence typing (MLST) performed with two isolates confirmed that their profiles corresponded to that of the Mediterranean clone. PFGE group 2 comprised nine strains, of which the majority showed no antibiotic resistance. Their pspA profiles were different, and the partial sequences obtained for two representative isolates indicated the presence of PspA proteins of different clades. The MLST profile of one strain was identical to that of a serotype 6B strain from the United Kingdom, while two other isolates were novel one-allele variants. This clone appears to be related (five of seven identical alleles) to two other internationally disseminated clones, Hungary(19A)-6 and Poland(23F)-16, both of which are penicillin resistant. The presence of antibiotic-susceptible isolates of this clone suggests that traits other than antibiotic resistance can make a clone successful.

Macrolide efflux genes mef(A) and mef(E) are carried by different genetic elements in Streptococcus pneumoniae

Susceptibilities to macrolides were evaluated in 267 Streptococcus pneumoniae isolates, of which 182 were from patients with invasive diseases and 85 were from healthy carriers. Of the 98 resistant isolates, 20 strains showed an M phenotype and carried mef. Strains that carried both mef(A) and mef(E) were found: 17 strains carried mef(A) and 3 carried mef(E). The characteristics of the strains carrying the mef genes and the properties of the mef-containing elements were studied. Strains carrying mef(A) belonged to serotype 14, were susceptible to all the antibiotics tested except erythromycin, and appeared to be clonally related by pulsed-field gel electrophoresis (PFGE). The three mef(E) strains belonged to different serotypes, showed different susceptibility profiles, and did not appear to be related by PFGE. The sequences of a fragment of the mef-containing element, which encompassed mef and the msr(A) homolog, were identical among the three mef(E)-positive strains and among the three mef(A)-positive strains, although there were differences between the sequences for the two variants at 168 positions. In all mef(A)-positive strains, the mef element was inserted in celB, which led to impairment of the competence of the strains. In line with insertion of the mef(E) element at a different site, the competence of the mef(E)-positive strains was maintained. Transfer of erythromycin resistance by conjugation was obtained from two of three mef(A) strains but from none of three mef(E) strains. Due to the important different characteristics of the strains carrying mef(A) or mef(E), we suggest that the distinction between the two genes be maintained.