Novel type of Streptococcus pneumoniae causing multidrug-resistant acute otitis media in children

A new approach to define the optimal immunization strategy against pneumococcal disease: the example of Canada

New-generation pneumococcal conjugate vaccines (PCVs) are available to replace PCV-13 for childhood and adult immunization. Besides cost-effectiveness evaluations which have highly variable results, the comparative immunogenicity of these new vaccines (PCV15, PCV20, PCV21) and their coverage of invasive pneumococcal disease (IPD) and carriage strains in different age-groups should be regarded as well as the antibody susceptibility, antibiotic resistance, invasiveness and virulence of serotypes included in each vaccine. Based on the Canadian experience, these topics are discussed. The optimal strategy would be a 2+1 PCV20 schedule for children, PCV21 for elderly adults and a dual PCV20+PCV21 schedule for adults at very high IPD risk. Shifting from PCV-13 to PCV-15 for children entails a risk of increased IPD incidence in adults because additional serotypes are of low virulence and could be replaced by more invasive and virulent serotypes. This risk can be reasonably excluded if PCV-20 replaces PCV-13 as the former covers additional serotypes being highly invasive and virulent. It is recognized that off-label use of PCV-20 according to a 2+1 schedule could be problematic for some jurisdictions as this is not authorized in all countries. In Canada, however, the 2+1 PCV20 schedule was authorized based on the same dataset submitted elsewhere.

Capsular typing of Streptococcus pneumoniae isolated from clinical specimens in Gauhati Medical College and hospital, Assam, India

PURPOSE

Streptococcus pneumoniae is an important human respiratory tract pathogen causing pneumococcal diseases in majority of children and adults. The capsule is a significant virulence factor of Pneumococci which determines the bacterial serotype and is the component used for synthesis of pneumococcal vaccines. This cross-sectional study aimed to isolate Streptococcus pneumoniae from clinical samples and determine the occurrence of its circulating serotypes in Assam, North East India.

MATERIALS AND METHODS

A total of 80 clinical samples were collected from June 2019 to May 2020 from patients clinically suspected from pneumococcal infection and also included samples routinely sent to bacteriology laboratory. Isolation and identification of S. pneumoniae was performed using conventional culture and molecular methods. Antibiotic susceptibility patterns were monitored. Capsular serotyping was performed using PCR of cpsA gene followed by DNA sequencing.

RESULTS

Majority of the cases suspected of pneumococcal infection belong to the paediatric group aged less than 5 years. Out of 80 samples, 10 (12.50%) were found to be positive by PCR of recP gene. Culture was positive in 80% (8/10) of the total positives. Co-trimoxazole resistance was seen in 33.33% of the isolate from sputum. Serotypes 6A, 6B, 6C and 19F were detected in our region, out of which 6C is a non-vaccine serotype.

CONCLUSION

Continued surveillance is needed to monitor trends in non-vaccine serotypes that may emerge as highly associated with antibiotic resistance. Also, the need to continuous monitoring of the antibiotic susceptibility of S. pneumoniae in North eastern parts of India is of outmost importance.

Rising Pneumococcal Antibiotic Resistance in the Post-13-Valent Pneumococcal Conjugate Vaccine Era in Pediatric Isolates From a Primary Care Setting

BACKGROUND

Antibiotic-resistant Streptococcus pneumoniae strains may cause infections that fail to respond to antimicrobial therapy. Results reported from hospitalized patients with invasive, bacteremic infections may not be the same as those observed in a primary care setting where young children receive care for noninvasive infections. Young children experience the highest burden of pneumococcal disease. The aim of this study was to determine the antibiotic susceptibility of S. pneumoniae strains isolated from children in a primary care setting in the post-13-valent pneumococcal conjugate vaccine (PCV13) era.

METHODS

This was a prospective collection of 1201 isolates of S. pneumoniae from 2006 through 2016 in a primary care setting. Antibiotic susceptibility testing to 16 different antibiotics of 10 classes was performed. Participants were children aged 6-36 months. Nasopharyngeal swabs were obtained from patients during acute otitis media (AOM) visits and routine healthy visits. Middle ear fluid was obtained by tympanocentesis.

RESULTS

After introduction of PCV13, antibiotic susceptibility of pneumococci, especially to penicillin, initially improved largely due to disappearance of serotype 19A, included in PCV13. However, beginning in 2013, antibiotic susceptibility among pneumococcal strains began decreasing due to new serotypes not included in PCV13. In addition to reduced susceptibility to penicillin, the most recent isolates show reduced susceptibility to third-generation cephalosporins, fluoroquinolones, and carbapenems, antibiotics commonly used to treat life-threatening, invasive pneumococcal diseases.

CONCLUSIONS

In recent years, pneumococcal nasopharyngeal and AOM isolates from children exhibit reduced susceptibility to penicillin, third-generation cephalosporin, fluoroquinolone, and carbapenem antibiotics. The new strains have a different profile of resistance compared to the pre-PCV13 era.

Fluoroquinolone resistance of Streptococcus pneumoniae isolates causing invasive disease: special focus on zabofloxacin

The present study examined the in vitro activity of various antibiotics including zabofloxacin, against isolates responsible for invasive pneumococcal diseases. Between 1997 and 2008, a total of 208 isolates were collected from sterile fluids, including blood (n=196, 94.2%), pleural fluid (n=5, 2.4%), cerebrospinal fluid (n=5, 2.4%), and ascites (n=2, 1.0%). Zabofloxacin showed the lowest MIC50 (0.015μg/mL) and MIC90 (0.025μg/mL) values of all the tested antibiotics. Rates of isolates resistant to penicillin (MIC ≥8μg/mL), ceftriaxone (MIC ≥4μg/mL) and levofloxacin (MIC ≥8μg/mL) were 3.4%, 0.4% and 2.0%, respectively. Four isolates (2.0%) were resistant to levofloxacin, and zabofloxacin showed low MICs (range, 0.025-0.125μg/mL). Zabofloxacin shows potent in vitro activity against S. pneumoniae isolates that caused invasive disease, even strains that are resistant to levofloxacin.

Nonencapsulated Streptococcus pneumoniae as a cause of chronic adenoiditis

Streptococcus pneumoniae is an important human pathogen. To cause disease, it must first colonize the nasopharynx. The widespread use of pneumococcal-conjugate vaccines which target the capsular polysaccharide has led to decreased nasopharyngeal carriage of vaccine serotypes, but a concomitant increase in carriage of non-vaccine serotypes and nonencapsulated S. pneumoniae (NESp). Some NESp express pneumococcal surface protein K (PspK), a virulence factor shown to contribute to nasopharyngeal colonization.

We present the case of a child with chronic adenoiditis caused by a PspK⁺ NESp. We tested the pneumococcal isolate, designated C144.66, for antimicrobial resistance, the presence of the pspK gene and the expression of PspK. Sequence typing and genome sequencing were performed. C144.66 was found to be resistant to erythromycin and displayed intermediate resistance to penicillin and trimethoprim/sulfamethoxazole. C144.66 has the pspK gene in place of the capsule locus. Additionally, PspK expression was confirmed by flow cytometry. NESp are a growing concern as an emerging human pathogen, as current pneumococcal vaccines do not confer immunity against them. An inability to vaccinate against NESp may result in increased carriage and associated pathology.

Otitis-prone Children Have Immunologic Deficiencies in Naturally Acquired Nasopharyngeal Mucosal Antibody Response after Streptococcus pneumoniae Colonization

OBJECTIVES

Acute otitis media (AOM) is the most common pediatric bacterial infection, and stringently defined otitis-prone (sOP) children have immunologic deficiencies. We recently found that nasopharyngeal (NP) colonization by Streptococcus pneumoniae (Spn) elicits a NP mucosal antibody response to vaccine candidate pneumococcal proteins that correlate with protection from AOM in non-sOP (NOP) children. Here, we sought to determine if sOP children experience significantly higher colonization rates with Spn than NOP children, develop lower naturally acquired NP mucosal antibody responses to those same pneumococcal proteins after colonization by Spn, and suffer greater frequency of AOM as a consequence.

METHODS

NP samples were collected from 130 NOP and 45 sOP children during 270 healthy visits and 201 AOM visits between 6 and 24 months of age. Spn were identified by standard culture. NP mucosal IgG and IgA levels to vaccine candidate proteins pneumococcal histidine triad protein D, pneumococcal choline binding protein A (PcpA) and pneumolysin D1 were measured by quantitative enzyme-linked immunosorbent assay.

RESULTS

sOP children had significantly higher colonization frequency by Spn (P < 0.0001) and significantly lower IgG and IgA levels to all 3 vaccine candidate proteins studied compared with NOP children (all P values <0.05) except IgG to Ply D1 (P = 0.31). Spn colonization in NOP children led to 2-fold to 5-fold increase in mucosal IgG and IgA levels to all 3 proteins (all P values <0.01), whereas Spn colonization in sOP children generally failed to elicit antibody responses (all P values >0.05). PcpA was unique in inducing significant increases in mucosal IgA (P = 0.02). When high mucosal IgG levels to all 3 proteins and IgA to PcpA were measured, they correlated with reduced AOM in sOP children.

CONCLUSION

sOP children experience significantly higher colonization rates with Spn, develop lower naturally acquired NP mucosal antibody responses to pneumococcal vaccine candidate proteins pneumococcal histidine triad protein D, PcpA and pneumolysin D1 after colonization by Spn, and suffer greater frequency of AOM if they do not generate high mucosal antibody to the studied proteins.

Ability of Antibiotic-Resistant Nonvaccine-Type Pneumococcal Clones to Cause Otitis Media in an Infant Mouse Model of Pneumococcal-Influenza Virus Coinfection

The introduction of the 7-valent pneumococcal conjugate vaccine in Portugal resulted in reduced carriage in children by vaccine-type strains and an increased carriage of three major antibiotic-resistant clones, ST2191, ST276, and ST63 expressing capsules 6A, 19A, and 15A, respectively. Pneumococcal otitis media (OM), a frequent infection among preschool age children, is often associated with viral coinfection. To evaluate the ability of these three antibiotic-resistant clones to cause disease, we used an infant mouse model of influenza virus pneumococcal coinfection. The 6A and 19A clonal types induced OM, while 15A induced pneumococcal pneumonia and bloodstream infection, suggesting potential for invasive disease.

Panel 5: Microbiology and immunology panel

OBJECTIVE

The objective is to perform a comprehensive review of the literature from January 2007 through June 2011 on the virology, bacteriology, and immunology related to otitis media.

DATA SOURCES

PubMed database of the National Library of Medicine.

REVIEW METHODS

Three subpanels with co-chairs comprising experts in the virology, bacteriology, and immunology of otitis media were formed. Each of the panels reviewed the literature in their respective fields and wrote draft reviews. The reviews were shared with all panel members, and a second draft was created. The entire panel met at the 10th International Symposium on Recent Advances in Otitis Media in June 2011 and discussed the review and refined the content further. A final draft was created, circulated, and approved by the panel.

CONCLUSION

Excellent progress has been made in the past 4 years in advancing an understanding of the microbiology and immunology of otitis media. Advances include laboratory-based basic studies, cell-based assays, work in animal models, and clinical studies.

IMPLICATIONS FOR PRACTICE

The advances of the past 4 years formed the basis of a series of short-term and long-term research goals in an effort to guide the field. Accomplishing these goals will provide opportunities for the development of novel interventions, including new ways to better treat and prevent otitis media.

Pneumococcal serotypes causing acute otitis media among children in Barcelona (1992-2011): emergence of the multiresistant clone ST320 of serotype 19A

BACKGROUND

There is scarce information about changes in serotypes and clonal types of Streptococcus pneumoniae causing acute otitis media (AOM) in recent years, particularly in European countries.

METHODS

Pneumococcal serotypes and clones from S. pneumoniae strains isolated from children with AOM who were attended at Hospital Sant Joan de Déu, Barcelona (1992 to 2011), were studied. Heptavalent pneumococcal conjugate vaccine (PCV7) was introduced in June 2001. We defined 3 periods: prevaccine period 1992 to 2001, early vaccine period 2002 to 2006 and late vaccine period 2007 to 2011.

RESULTS

There were 376 pneumococcal strains causing AOM, and 373 (99.2%) of them were serotyped. AOM caused by PCV7 serotypes declined significantly: 161 of 245 (65.7%) episodes in 1992 to 2001 versus 22 of 67 (32.8%) in 2002 to 2006 versus 8 of 61 (13.1%) in 2007 to 2011 P < 0.001. In the last period (2007 to 2011), the potential serotype coverage for the PCV10 was 16.4% and for the PCV13 was 68.9% (P < 0.001). Serotype 19A increased from 5.7% in 1992 to 2001 to 42.6% in 2007 to 2011 (P < 0.001). Among strains with penicillin minimal inhibitory concentration ≥0.12 μg/mL (n = 241), serotype 19A rose from 2.3% in the first period to 57.9 % in the last period (P < 0.001). The clonal-type ST320 was initially detected in 2005, and in the period 2007 to 2011, the ST320 was found in 72.7% of nonsusceptible serotype 19A isolates.

CONCLUSIONS

Among children with AOM, a rapid expansion of the multiresistant clone ST320 expressing serotype 19A has been observed in Barcelona. The implementation of PCV13, which includes this serotype, may decrease the prevalence of AOM and reduce antimicrobial resistance.

Changes in Streptococcus pneumoniae serotype 19A invasive infections in children from 1993 to 2011

Among 594 Streptococcus pneumoniae serotype 19A invasive pneumococcal disease (IPD) isolates collected from 1993 to 2011, we identified 85 sequence types by multilocus sequence typing. CC320 was associated with multidrug resistance and reduced susceptibility to penicillin and ceftriaxone and still predominated among declining serotype 19A IPD isolates following PCV13 introduction.

Emergence of potential superbug mycobacterium tuberculosis, lessons from new delhi mutant-1 bacterial strains

Recent reports have shown that certain bacterial strains attain the New Delhi Metallo-beta-lactamase-1 (NDM-1) enzyme and become resistant to a broad range of antibiotics. Similarly, more dangerous "superbugs" of multi-drug resistant (MDR) and extensive drug resistant (XDR) Mycobacterium tuberculosis strains are gradually emerging through rapid genetic mutation caused by prescription non-compliance or unsupervised indiscriminate use of anti-tubercular drugs or other antibiotics. Mycobacterium tuberculosis cases have been reported in highly susceptible population groups including the aboriginal communities of US and Canada. In Canada alone, the total number of reported tuberculosis cases has decreased over the past decade. However, there is a steady increase in HIV cases in certain communities including the aboriginal communities. Reintroduction of MDR/XDR strains of tuberculosis is possible in these susceptible communities, which in turn may pose serious public health situation. MDR/XDR strains of tuberculosis are virtually untreatable using current anti-tubercular medication protocols. Thus, MDR/XDR tuberculosis presents a grave global public health threat. The unpredictable genetic mechanism involved in generating MDR/XDR resistant strains of Mycobacterium tuberculosis may pose greater challenges in developing appropriate treatment strategies. In this article, we briefly review potential genetic mechanism of emerging NDM-1 bacterial strains and draw a rationale parallel to the underlying genetic mechanism of MDR/XDR Mycobacterium tuberculosis strain development.

Pharmacotherapy for pneumococcal infections: an update

INTRODUCTION

The management of pneumococcal diseases still places a significant burden on medical and economic resources. The subjects at greatest risk of pneumococcal infections are children.

AREAS COVERED

The aim of this review is to analyse the best current therapeutic approach to pneumococcal resistance, taking into account the level of susceptibility of Streptococcus pneumoniae, and the pharmacokinetics and pharmacodynamics of different antibiotics in the various pneumococcal diseases.

EXPERT OPINION

Antibiotic treatment of a number of pneumococcal diseases remains difficult or impossible due to the presence of strains resistant to commonly used antibiotics. In children the problem is significantly more important than in adults due to the reduced number of licenced drugs for subjects in the first years of life. The new conjugate pneumococcal vaccines containing 10 (PCV10) and 13 serotypes (PCV13), which include most of the recently emerging strains, might reduce the incidence of pneumococcal infections and the circulation of resistant pathogens. However, it is likely that optimal results will only be reached after the development of effective vaccines based on conserved proteins that are capable of preventing all pneumococcal infections, regardless of the serotype of the causative organism.

Pneumococcal vaccines for children: a global public health priority

Pneumococcal conjugated vaccines have been recommended in children for over a decade in many countries worldwide. Here we review the development of pneumococcal vaccines with a focus on the two types currently available for children and their safety record. We discuss also the effect of vaccines, including the 13-valent pneumococcal conjugate vaccine, on invasive pneumococcal diseases in children, particularly bacteraemia, pneumonia and meningitis, as well as on mucosal disease and carriage. In regions where immunization was implemented in young children, the number of invasive pneumococcal diseases decreased significantly, not only in the target age group, but also in younger and much older subjects. Challenges and future perspectives regarding the development of new 'universal' vaccines, which could bypass the current problem of serotype-specific protection in a context of serotype replacement, are also discussed.

Nasal carriage of Streptococcus pneumoniae serotypes and Staphylococcus aureus in Streptococcus pneumoniae-vaccinated and non-vaccinated young children

Since the implementation of Streptococcus pneumoniae (SPn) conjugate vaccination (PCV), non-vaccine types have prevailed in invasive pneumococcal disease (IPD), and an increase in Staphylococcus aureus (SA) burden has been suggested. Here, we assess the epidemiology of SA and SPn nasal carriage in 620 children at day-care centres; 141 of these children had received 1-4 PCV7 doses. A higher vaccine dosage was associated with non-vaccine-type SPn carriage. Of all SPn isolates, 45% were PCV7 types, 1% were additional PCV10 types and 22% were the three additional PCV13 types. SA carriage was inversely associated with vaccine-type SPn carriage. SPn serotype 19A showed higher SA co-carriage rates compared to other SPn serotypes. PCV7 implementation does not prevent children from being part of the IPD-related SPn transmission chain. These results contribute to the monitoring of SA- and SPn-related disease and add to the debate on the current national vaccination policy that recently included a change from PCV7 to PCV10.

Otitis media

Otitis media represents a broad spectrum of disease, which include acute otitis media and otitis media with effusion. As immunization with the pneumococcal conjugate vaccine has become more widespread, the microbiological landscape of otitis media has changed, which affects the treatment options facing clinicians worldwide. This review discusses the diagnosis and medical management of acute and chronic suppurative otitis media, the changes noted over the past decade, and briefly expounds on the surgical management of their severe complications.

Population biology of Gram-positive pathogens: high-risk clones for dissemination of antibiotic resistance

Infections caused by multiresistant Gram-positive bacteria represent a major health burden in the community as well as in hospitalized patients. Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium are well-known pathogens of hospitalized patients, frequently linked with resistance against multiple antibiotics, compromising effective therapy. Streptococcus pneumoniae and Streptococcus pyogenes are important pathogens in the community and S. aureus has recently emerged as an important community-acquired pathogen. Population genetic studies reveal that recombination prevails as a driving force of genetic diversity in E. faecium, E. faecalis, S. pneumoniae and S. pyogenes, and thus, these species are weakly clonal. Although recombination has a relatively modest role driving the genetic variation of the core genome of S. aureus, the horizontal acquisition of resistance and virulence genes plays a key role in the emergence of new clinically relevant clones in this species. In this review, we discuss the population genetics of E. faecium, E. faecalis, S. pneumoniae, S. pyogenes and S. aureus. Knowledge of the population structure of these pathogens is not only highly relevant for (molecular) epidemiological research but also for identifying the genetic variation that underlies changes in clinical behaviour, to improve our understanding of the pathogenic behaviour of particular clones and to identify novel targets for vaccines or immunotherapy.

Phylogenetic relatedness and diversity of non-typable Haemophilus influenzae in the nasopharynx and middle ear fluid of children with acute otitis media

The phylogenetic relationships of non-typable Haemophilus influenzae (NTHi) strains prospectively isolated from healthy children and children with acute otitis media (AOM) were analysed using multilocus sequence typing (MLST). A total of 165 NTHi isolates were collected over a 3.5 year time frame during 2006 through 2009. The strains were tested for β-lactamase production; 28.5% were positive. Seventy different NTHi sequence types (STs) were identified of which 29 (41.4%) were novel. NTHi strains did not show any phylogenetic grouping or clustering among asymptomatic colonizing strains or strains that caused AOM, or based on β-lactamase enzyme production. Evaluation of triplets and other siblings over time demonstrated relatively frequent genetic exchanges in NTHi isolates in vivo in a short time frame and subsequent transfer among children in a family. Comparison of the MLST STs isolated at different time points showed that in ~85% of the nasopharynx (NP) colonizations, NTHi strains cleared from the host within 3 months, that sequential colonization in the same child involved different strains in all cases except one, and that NP and middle ear isolates were identical STs in 84% of cases. In this first study of its type to our knowledge, we could not identify predominant MLST types among strains colonizing the NP versus those causing AOM or expressing a β-lactamase enzyme conferring penicillin resistance in children.

Distribution, dynamics and antibiotic resistance patterns of Streptococcus pneumoniae serotypes causing acute otitis media in children in southern Israel during the 10 year-period before the introduction of the 7-valent pneumococcal conjugate vaccine

OBJECTIVES

To determine the dynamics of serotype prevalence, potential coverage by pneumococcal conjugate vaccines (PCV) and antibiotic resistance patterns of Streptococcus pneumoniae causing acute otitis media (AOM) in children in southern Israel before PCV7 introduction in the routine immunization program in Israel.

METHODS

All S. pneumoniae isolates from middle ear fluid from children with AOM during 1999-2008 were included. Prospectively collected demographic data on S. pneumoniae serotypes and antibiotic resistance patterns were analyzed.

RESULTS

A total of 14,911 tympanocenteses yielded 5281 (35%) S. pneumoniae. Proportion of S. pneumoniae-AOM did not vary significantly (overall 35%; 33% in 2007; 38% in 2002 and 2003). The most frequent serotypes were 19F, 14, 23F and 19A; in both Jewish and Bedouin children; serotypes 6A and 19A contributed 6% and 10%, respectively, of all S. pneumoniae isolates. Serotypes included in PCV7, PCV10 and PCV13 represented 60%, 64%, 85% in Jewish children vs. 49%, 55% and 74%, respectively, in Bedouin children (P < 0.001). Nonsusceptibility to TMP/SMX decreased significantly, in parallel with a significant increase in the nonsusceptibility to erythromycin, clindamycin and in multidrug resistant (MDR) isolates. No changes were recorded in the proportion of S. pneumoniae isolates with penicillin MIC ≥ 1.0 μg/ml. The proportion of penicillin- and erythromycin-nonsusceptible and of MDR serotype 6A and 19A isolates increased significantly in Bedouin children.

CONCLUSIONS

(1) No significant changes were recorded in the yearly proportions of serotypes 23F, 19F, 19A, 14 and 6A in both ethnic populations; (2) Potential coverage of the 3 PCVs was higher in Jewish children than in Bedouin children; (3) The relatively high coverage of macrolides- and multidrug-resistant S. pneumoniae by PCV13 and lack of increase in penicillin, erythromycin and multidrug nonsusceptibility among non-PCV13 isolates is encouraging.

Streptococcus pneumoniae clonal complex 199: genetic diversity and tissue-specific virulence

Streptococcus pneumoniae is an important cause of otitis media and invasive disease. Since introduction of the heptavalent pneumococcal conjugate vaccine, there has been an increase in replacement disease due to serotype 19A clonal complex (CC)199 isolates. The goals of this study were to 1) describe genetic diversity among nineteen CC199 isolates from carriage, middle ear, blood, and cerebrospinal fluid, 2) compare CC199 19A (n = 3) and 15B/C (n = 2) isolates in the chinchilla model for pneumococcal disease, and 3) identify accessory genes associated with tissue-specific disease among a larger collection of S. pneumoniae isolates. CC199 isolates were analyzed by comparative genome hybridization. One hundred and twenty-seven genes were variably present. The CC199 phylogeny split into two main clades, one comprised predominantly of carriage isolates and another of disease isolates. Ability to colonize and cause disease did not differ by serotype in the chinchilla model. However, isolates from the disease clade were associated with faster time to bacteremia compared to carriage clade isolates. One 19A isolate exhibited hypervirulence. Twelve tissue-specific genes/regions were identified by correspondence analysis. After screening a diverse collection of 326 isolates, spr0282 was associated with carriage. Four genes/regions, SP0163, SP0463, SPN05002 and RD8a were associated with middle ear isolates. SPN05002 also associated with blood and CSF, while RD8a associated with blood isolates. The hypervirulent isolate's genome was sequenced using the Solexa paired-end sequencing platform and compared to that of a reference serotype 19A isolate, revealing the presence of a novel 20 kb region with sequence similarity to bacteriophage genes. Genetic factors other than serotype may modulate virulence potential in CC199. These studies have implications for the long-term effectiveness of conjugate vaccines. Ideally, future vaccines would target common proteins to effectively reduce carriage and disease in the vaccinated population.

[Nasopharyngeal carriage, antibiotic susceptibility and serotyping of Streptococcus pneumoniae and Haemophilus influenzae in children attending day care centers]

The aim of this study was to investigate the nasal carriage of Streptococcus pneumoniae (SP) and Haemophilus influenzae (HI) in children.

METHODS

Nasal samples were swabbed from children 3 months to 3 years of age, between December 2006 and April 2007, in 10 day-care centers in Dijon.

RESULTS

Three hundred and eighty-five children, 22.7 ± 8.4 months, were included. All were vaccinated against H1 and 92% had received at least one dose of PCV7 vaccine. HI colonization (55%) was associated with young age and concomitant pneumococcal carriage (52.4% vs. 39%). Amoxicillin/clavulanate and cefotaxime resistance rates were 17% and 0.5%. Pneumococcal carriage (48%) was increased in case of prior hospitalization. The rate of PDSP, 50%, was increased in case of recent infection (91% vs. 81%), previous antibiotherapy (64% vs. 41%), and decreased if PCV7 was completed (40.2% vs. 61,8%). There was no resistance to amoxicillin. The erythromycin resistance rate was 50.5%. 15% of the strains were vaccinal serotypes. Thirty-six and 41% of the strains were related and non-related to vaccine serotypes. Twenty-four and 11.6% of the strains were serotypes 19A and 6A respectively.

CONCLUSION

Over the last 10 years the global antibiotic resistance in children decreased for SP (22.9%) but nasal colonization remained stable due to the increase of some serotypes, such as 19A, most often resistant to antibiotics. The vaccine effectiveness against HI is optimal since no HIb serotypes were detected; resistance to betalactam is currently due equally to enzymatic mechanism and alteration of protein binding penicillin.

Identification of Streptococcus pneumoniae and Haemophilus influenzae in culture-negative middle ear fluids from children with acute otitis media by combination of multiplex PCR and multi-locus sequencing typing

OBJECTIVE

Streptococcus pneumoniae (Spn) and Haemophilus influenzae (Hflu) are major etiologic pathogens for acute otitis media (AOM). However, when Spn and Hflu strains are not identified by traditional culture methods, use of alternative PCR-based diagnosis becomes critical. This study aimed to develop a combined molecular method to accurately detect these otopathogens.

METHODS

Middle ear fluid (MEF) samples were collected by tympanocentesis from children with AOM to isolate Spn and Hflu by standard culture procedures. Multiplex PCR (mPCR) and multi-locus sequence typing (MLST) techniques were used to detect Spn and Hflu in culture-negative MEF samples.

RESULTS

We found 20 Spn or Hflu culture-positive MEF samples that were mPCR-positive and typeable by MLST. The sequences of the housekeeping genes and the MLST allelic profiles obtained from Spn or Hflu culture isolates matched exactly MEF samples that were tested directly without culture isolation. Of 63 MEF samples that were culture-negative for Spn, 38% (24/63) were mPCR-positive for Spn. Of 50 MEF samples that were culture-negative for Hflu, 24% (12/50) were mPCR-positive for Hflu. Among these culture-negative but mPCR-positive MEF samples, 25% (6/24) and 25% (3/12) were typeable by MLST for Spn and Hflu, respectively.

CONCLUSIONS

MEF samples may be analyzed with mPCR and MLST directly without culture isolation and the addition of mPCR and MLST may accurately identify Spn and Hflu in MEF of children with AOM when bacterial culture is negative.

Time-kill activity of the streptogramin NXL 103 against Gram-positive and -negative bacteria

Against 33 Gram-positive and -negative bacteria, NXL 103 MICs were 0.03 to 1 μg/ml. NXL 103 was bactericidal by 12 h at 2 × MIC against all 5 pneumococci and at 2 × MIC after 24 h against all 5 group A and B β-hemolytic streptococci. NXL 103 was bactericidal against all 8 Haemophilus influenzae strains at 2 × MIC and all 5 Moraxella catarrhalis strains at 4 × MIC after 24 h but was mainly bacteriostatic against 5 methicillin-resistant Staphylococcus aureus strains. After the exposure of one strain of each species to NXL 103 for 10 daily subcultures, the MICs remained within ± 1 dilution.

Epidemiology and evolution of invasive pneumococcal disease caused by multidrug resistant serotypes of 19A in the 8 years after implementation of pneumococcal conjugate vaccine immunization in Dallas, Texas

BACKGROUND

The heptavalent pneumococcal conjugate vaccine (PCV7) has significantly reduced vaccine-type invasive pneumococcal disease (IPD) in children. An increasing percentage of IPD cases are now caused by nonvaccine serotypes. The purpose of our observational study was to define the epidemiology of pneumococcal disease in Dallas, TX children for 8 years after implementation of PCV7 immunization.

METHODS

Streptococcus pneumoniae isolates from normally sterile sites were collected at Children's Medical Center of Dallas from January 1, 1999 to December 31, 2008. Incidence of IPD was calculated using inpatient and emergency center admissions to Children's Medical Center of Dallas as the denominator. Isolates were serotyped and penicillin and cefotaxime susceptibilities were determined. Serotype 19A isolates were further characterized by multilocus sequence typing.

RESULTS

Compared with the prevaccine period of 1999-2000, there was a significant reduction in the incidence of IPD from 2002 to 2008 (P < 0.05), although a significant increase in IPD incidence was observed from 2006 to 2008 (P = 0.038). The number of IPD cases caused by serotype 19A increased from 1999 to 2008 (P < 0.001). There were significant increases in penicillin and cefotaxime nonsusceptible 19A isolates during this 10-year period (P < 0.001 and P = 0.004, respectively). The most common sequence type (ST) of the 19A isolates was ST-199 (42.7%). Clonal complex (cc-156) and cc-320 emerged in the period of 2005-2008 as penicillin and cefotaxime resistant 19A strains.

CONCLUSIONS

In Dallas, PCV7 immunization reduced significantly the incidence of IPD caused by vaccine-type strains. A significant increase in IPD caused by serotype 19A was observed. The penicillin and cefotaxime nonsusceptible STs, not previously identified in Dallas, have recently become an important cause of IPD.

The epidemiology of pneumococcal infections--the Swedish experience

Pneumococcal infections are major contributors to morbidity and mortality world-wide and pose a major public health problem. Despite being a devastating pathogen pneumococci are common colonizers of the upper respiratory tract of healthy children. There is a need for more knowledge on the molecular epidemiology, and pathogenesis of pneumococcal infections to be able to find better strategies for prevention and treatment of these common infections. Here we discuss trends in the vaccine era of the epidemiology of pneumococcal carriage, invasive disease and antibiotic resistance development as well as present national epidemiology data from Sweden of invasive pneumococcal infections during 1987-2006.