Increased nasopharyngeal carriage of serotypes 6A, 6C, and 6D Streptococcus pneumoniae after introduction of childhood pneumococcal vaccination in Hong Kong

Pneumococcal colonization among healthy and hospitalized vaccine-naive Sri Lankan children

BACKGROUND

Streptococcus pneumoniae continues to cause mortality and morbidity despite availability of effective vaccines. Pneumococcal colonization is considered a pre-requisite for disease. Identifying the serotypes circulating in a given locale is important for surveillance purposes as well as for assessing the need for vaccination. Aim of the present study was to identify nasopharyngeal pneumococcal colonization rates in healthy children and children with respiratory tract infections in central Sri Lanka.

METHOD

A total of 450 nasopharyngeal swabs (NPS) of children aged between 2 months and 2 years were collected from two groups; healthy children and children hospitalized with respiratory symptoms. NPS samples were processed using conventional laboratory techniques to isolate S. pneumoniae. Antibiotic susceptibility patterns of pneumococcal isolates were identified using CLSI disc diffusion method and minimum inhibitory concentration (MIC) was determined by micro-broth dilution method.

RESULTS

Pneumococcal colonization rate among healthy children was 31.8% (143/450) it was 39.8% (179/450) in children hospitalized with respiratory symptoms. MIC for penicillin and cefotaxime ranged between 0.015 to 4 µg/ml and <0.015 to 16 µg/ml respectively. All isolates were susceptible to levofloxacin, vancomycin, linezolid and rifampicin. Erythromycin and tetracycline non-susceptibility rates were >50% in both groups. The predominant serotypes identified were 19F (n = 66, 20.5%), 6B (n = 43, 13.4%), 6A (n = 30, 9.3%), 23F (n = 28, 8.7%) and 14 (n = 20, 6.2%). Among healthy children, presence of school going children at home and the number of household members were significantly associated with pneumococcal colonization while in hospitalized children, pneumococcal colonization was significantly associated with presence of school going children at home.

CONCLUSION

Pneumococcal colonization rates were considerably higher in both study cohorts and the commonest serotypes were 19F, 6B, 6A, 23F and 14. Antibiotic resistance rates were also relatively higher among the pneumococcal isolates.

Substantial reduction of antibiotic-non-susceptible pneumococcal otitis media following PCV7/PCV13 sequential introduction

BACKGROUND

In the pre-pneumococcal conjugated vaccines (PCVs) era, serotypes included in the 7/13-valent PCVs (PCV7/PCV13) caused most pneumococcal otitis media (OM) and antibiotic-non-susceptible pneumococcal OM (ANSP-OM) episodes. In southern Israel, sequential PCV7/PCV13 introduction resulted in >90% reduction of vaccine-serotype OM.

OBJECTIVES

We assessed the dynamics of ANSP-OM necessitating middle ear fluid culture following PCV7/PCV13 sequential introduction in young children.

METHODS

This was a prospective, population-based, active surveillance. All episodes in children <3 years old, during 2004-16, were included. Two subperiods were defined: (i) pre-PCV: 2004-08; and (ii) PCV13: 2014-16. ANSP was defined for the following antibiotics: penicillin (MIC ≥0.1 mg/L and ≥1.0 mg/L), macrolide, tetracycline, clindamycin, ceftriaxone, trimethoprim/sulfamethoxazole and chloramphenicol. MDR was defined as ANSP for ≥3 classes.

RESULTS

Overall, 2270 pneumococcal OM episodes were identified. Annual overall pneumococcal, PCV13 and non-PCV13 serotype OM incidence declined by 86%, 97% and 33%, respectively, comparing pre-PCV with the PCV13 period. During 2004-08, 95% of ANSP was observed in vaccine serotypes. Incidence of penicillin (MIC ≥0.1 mg/L and ≥1.0 mg/L), macrolide, tetracycline, clindamycin, ceftriaxone and multidrug ANSP-OM declined by >90% in the PCV13 period. Rates of trimethoprim/sulfamethoxazole and chloramphenicol ANSP-OM declined by 85% and 79%, respectively. The proportions of ANSP of all pneumococcal isolates declined by ∼70% for penicillin, ceftriaxone and erythromycin; 53% for tetracycline; and 55% for MDR, versus no significant reductions observed for chloramphenicol, trimethoprim/sulfamethoxazole and clindamycin.

CONCLUSIONS

PCV7/PCV13 sequential introduction resulted in rapid and substantial ANSP-OM reduction, in parallel with the near disappearance of PCV13-serotype OM and no increase in replacement disease.

Molecular capsular typing and multi locus sequence typing of invasive, non-invasive and commensal Streptococcus pneumoniae isolates from North India

Purpose

The purpose of this study is to determine the antimicrobial susceptibility pattern, serotype distribution and sequence type (ST) of Streptococcus pneumoniae isolates from invasive and non-invasive infection and correlate it with isolates from commensal nasopharyngeal flora to ascertain their role in infection.

Materials and Methods

S. pneumoniae isolates from blood, cerebrospinal fluid, pleural fluid and respiratory secretions (sputum, bronchoalveolar lavage and nasopharyngeal swab/throat swab) were analysed to determine ST, serotype and antimicrobial susceptibility pattern. Serotyping was performed by multiplex polymerase chain reactions as well as by quellung reaction. Antimicrobial susceptibility testing was determined using Kirby Bauer's disc diffusion method as per the Clinical Laboratory Standards Institute guidelines. Minimum inhibitory concentration was determined using E-test for penicillin. Multilocus sequence typing (MLST) was done to understand genetic relatedness and evolutionary relationship among strains.

Results

A total of 125 S. pneumoniae isolates were collected, including 25 from invasive pneumococcal disease, 25 from non-invasive and 75 from nasopharyngeal swab of healthy children (Commensal). Resistance to penicillin, erythromycin, and co-trimoxazole was observed in 14.4%, 12% and 81.6% of the isolates, respectively, by KirbyBauer's disc diffusion method. Serotype 14 was found to be the most prevalent in invasive and non-invasive isolates, while serotype 6 was the most common in commensal isolates. New STs were found among invasive (ST13826, ST13827), non-invasive (ST13823, ST13824, and ST13961) and commensal (ST13825) isolates.

Conclusion

MLST sequence analysis shows that invasive isolates were found to be clustered with non-invasive and commensal isolates. Analysis of MLST suggests the possibility of genetic relatedness and exchange of genetic material between invasive, non-invasive and commensal isolates.

Epidemiology of culture-confirmed infections of Streptococcus pneumoniae (2012-2015) and nasopharyngeal carriage in children and households in Taiwan (2014-2015)

PURPOSE

An observational study was performed to investigate the carriage rate and serotypes of Streptococcus pneumoniae in the 13-valent pneumococcal conjugate vaccine (PCV13) era in Taiwan.

METHODOLOGY

From March 2014 to March 2015 a total of 500 healthy children and their households (631 adults) were enrolled from two large medical centres for nasopharyngeal carriage survey. Clinical isolates were prospectively collected from June 2012 to May 2015 at Chang Gung Memorial Hospital. We applied a multiplex polymerase chain reaction in addition to culture to detect S. pneumoniae.

RESULTS

S. pneumoniae was isolated from 12.0 % of the children and 3.6 % of the households. In the children's cohort only 23.3 % of the isolates could be assigned to PCV13 serotypes; non-vaccine serotypes were predominant (76.6 %) and the most frequently detected non-vaccine serotypes were 15A/F and 15B/C (both 13.3 %), followed by 23A (6.7 %). In the household cohort, 21.7 % belonged to PCV13 serotypes, and 78.3 % to non-vaccine serotypes. Clinical analysis of culture-confirmed pneumococcal infection showed that infection caused by PCV13 serotypes decreased by 47 % from 83 % in 2012-2013 to 44 % in 2014-2015, while infection caused by non-PCV13 serotypes increased from 17 to 56 %. Among the carriage isolates a significantly higher percentage belonged to serogroup 15 compared to serogroup 19 (26.6 vs 6.66 %, 2014-2015; P=0.003). Therefore, clinical isolates belonging to serogroup 15 were more prevalent than those belonging to serogroup 19 (44.1 vs 32.3 %, 2014-2015; P=0.318).

CONCLUSION

The isolation of non-vaccine serotypes and unknown serotypes after the introduction of PCV13 in children highlights the importance of continued surveillance for emerging serotypes.

Serotype 6B from a pneumococcal polysaccharide vaccine induces cross-functional antibody responses in adults to serotypes 6A, 6C, and 6D

Cross-reactivity of pneumococcal capsular polysaccharides is a key element for formulating pneumococcal vaccines and evaluating vaccine efficacy. This study examined whether 23-valent pneumococcal polysaccharide vaccine (PPSV23), which only contains 6B, can elicit cross-functional immune responses against recently discovered serotypes (6C and 6D), as well as against 6A, in 2 adult age groups.Young adults (25-51 years; N = 28) and elderly subjects (over 65 years; N = 60) were immunized with PPSV23. Functional antibody responses were determined in pre- and postimmune sera via multiplexed opsonophagocytic killing assay against serotypes 6A/B/C/D.At postimmunization, the geometric mean opsonic indices (OIs) for 6B and nonvaccine serotypes (6A, 6C, and 6D) significantly increased in both age groups. The geometric fold increases of OIs for 6B/A/C/D significantly differed (18.2, 24.8, 3.1, and 7.1, respectively). Proportions of subjects with 4-fold increases in OIs for 6B/A/C/D were 73%, 70%, 31%, and 49%, respectively. Correlations of fold increases in OIs were highest between 6B and 6A, followed by 6B and 6D, then by 6B and 6C. Comparisons of young adults and the elderly revealed that most immunogenicity variables were higher in the former group.Our data demonstrated that 6B in PPSV23 induced cross-functional immune responses against serotypes 6A, 6C, and 6D, according to the degree of similarity in their capsular polysaccharide structures. In addition, we found significant age-related differences in PPSV23-induced cross-reactivity.

Streptococcus pneumoniae Serotype Distribution and Pneumococcal Conjugate Vaccine Serotype Coverage among Pediatric Patients in East and Southeast Asia, 2000-2014: a Pooled Data Analysis

Pneumococcal infection is one of the leading causes of death worldwide, especially in children of developing and underdeveloped countries. Capsular polysaccharide-based vaccines are available for the prevention of this disease. A 7-valent pneumococcal conjugate vaccine (PCV7) was licensed in 2000 for use in children less than two years of age. Subsequently, to broaden the protection, 10-valent (PCV10) and 13-valent (PCV13) vaccines were licensed in 2009 and 2010, respectively. All of these conjugate vaccines elicit an immune response that only provides protection against the infection of S. pneumoniae serotypes included in the formulation. Profiles of S. pneumoniae serotype distribution and serotype coverage for both PCV7 and PCV13 have been reported in some Asian countries/territories. But the published results cannot provide conclusive information due to the difference in studied population and geographic areas. The goals of this review are to obtain an accurate estimate of serotype coverage for PCV7, PCV10, and PCV13 and examine the change in the S. pneumoniae serotype distribution after PCV7 use among pediatric patients in East and Southeast Asia through the analysis of pooled data that were published in the English literature between 2000 and 2014.

Draft Genome Sequences of Two Streptococcus pneumoniae Serotype 19F Sequence Type 271 Clinical Isolates with Low- and High-Level Cefotaxime Resistance

We report here the draft genomes of two pneumococcal isolates in Hong Kong, CU_SPNE1_05 and CU_SPNE32_06. Strain CU_SPNE1_05 had a cefotaxime MIC of 1 µg/ml, and CU_SPNE32_06 had an MIC of 32 µg/ml. Both strains belong to the multidrug-resistant serogroup 19, sequence type 271 (clonal complex 3200/271).

Genetic analyses of penicillin binding protein determinants in multidrug-resistant Streptococcus pneumoniae serogroup 19 CC320/271 clone with high-level resistance to third-generation cephalosporins

We describe the dissemination of a multidrug-resistant (MDR) serogroup 19 pneumococcal clone of representative multilocus sequence type 271 (ST271) with high-level resistance to cefotaxime in Hong Kong and penicillin binding protein (pbp) genes and its relationships to Taiwan(19F)-14 and the prevalent multidrug-resistant 19A clone (MDR19A-ST320). A total of 472 nonduplicate isolates from 2006 and 2011 were analyzed. Significant increases in the rates of nonsusceptibility to penicillin (PEN) (MIC ≥ 4.0 μg/ml; 9.9 versus 23.3%; P = 0.0005), cefotaxime (CTX) (MIC ≥ 2.0 μg/ml; 12.2 versus 30.3%; P < 0.0001 [meningitis MIC ≥ 1.0 μg/ml; 30.2 versus 48.7%; P = 0.0001]), and erythromycin (ERY) (69.2 versus 84.0%; P = 0.0003) were noted when rates from 2006 and 2011 were compared. The CTX-resistant isolates with MICs of 8 μg/ml in 2011 were of serotype 19F, belonging to ST271. Analyses of the penicillin binding protein 2x (PBP2x) amino acid sequences in relation to the corresponding sequences of the R6 strain revealed M339F, E378A, M400T, and Y595F substitutions found within the ST271 clone but not present in Taiwan(19F)-14 or MDR19A. In addition, PBP2bs of ST271 strains and that of the Taiwan(19F)-14 clone were characterized by a unique amino acid substitution, E369D, while ST320 possessed the unique amino acid substitution K366N, as does that of MDR19A in the United States. We hypothesize that ST271 originated from the Taiwan(19F)-14 lineage, which had disseminated in Hong Kong in the early 2000s, and conferred higher-level β-lactam and cefotaxime resistance through acquisitions of 19 additional amino acid substitutions in PBP2b (amino acid [aa] positions 538 to 641) and altered PBP2x via recombination events. The serogroup 19 MDR CC320/271 clone warrants close monitoring to evaluate its effect after the switch to expanded conjugate vaccines.

Emergence of serogroup 15 Streptococcus pneumoniae of diverse genetic backgrounds following the introduction of pneumococcal conjugate vaccines in Hong Kong

Serogroup 15 pneumococcal isolates from nasopharyngeal carriage of hospitalized children admitted to a teaching hospital in Hong Kong from April 2009 to September 2013 were characterized by pulse-field gel electrophoresis (PFGE), multilocus sequence typing, and antimicrobial non-susceptibility testing. The overall proportion of serogroup 15 isolates in the pre-PCV7 and post-PCV13 periods rose from 5.7% to 20.0%. The increase in trend for serotype 15B/C was statistically significant among children presented with pneumonia; bronchiolitis; upper respiratory tract infection; and febrile, non-respiratory diseases and for serotype 15A/F, among children with bronchiolitis and febrile, non-respiratory diseases. The predominant PFGE cluster of serotype 15B/C belonged to sequence type (ST) 199. Replacement of this more susceptible cluster (Ery and Tet non-susceptibilities of 32.2% and 25.4%) with the non-susceptible cluster, ST8859 (Ery and Tet non-susceptibilities of 91.7% and 87.5%) was noted. ST63 was the predominant serotype 15A cluster (Ery and Tet non-susceptibilities of 97.4% and 92.3%). Serogroup 15 subtypes have emerged in the post-PCV13 era, and these non-susceptible clusters warrant closer monitoring as candidates for incorporation to future pneumococcal vaccines.

Direct detection and prediction of all pneumococcal serogroups by target enrichment-based next-generation sequencing

Despite the availability of standard methods for pneumococcal serotyping, there is room for improvement in the available methods, in terms of throughput, multiplexing capacity, and the number of serotypes identified. We describe a target enrichment-based next-generation sequencing method applied to nasopharyngeal samples for direct detection and serogroup prediction of all known serotypes of Streptococcus pneumoniae, 32 to the serotype level and the rest to the closely related serogroup level. The method was applied to detect and to predict the serogroups of pneumococci directly in clinical samples and from sweeps of primary culture DNA, with increased detection rates versus culture-based identification and agreement with the serotypes/serogroups determined by conventional serotyping methods. We propose this method, in conjunction with traditional serotyping methods, as an alternative to rapid detection and serotyping of pneumococci.

Cardiopulmonary morbidity of streptococcal infections in a PICU

AIM

The streptococci are important bacteria that cause serious childhood infections. We investigated cardiopulmonary morbidity associated with streptococcal infection and pediatric intensive care unit (PICU) admission.

METHODS

A retrospective study between 2002 and 2013 of all children with a laboratory isolation of streptococcus.

RESULTS

There were 40 (2.3%) PICU patients with streptococcal isolations including Streptococcus pyogenes (Group A streptococcus, GAS, n = 7), Streptococcus agalactiae (Group B streptococcus, GBS, n = 5), Streptococcus pneumoniae (SP, n = 20), alpha-hemolytic (n = 4), beta-hemolytic (n = 2) and gama-hemolytic (n = 2) streptococci. Comparing among GAS, GBS and SP, respiratory isolates were more likely positive for GAS or SP (P = 0.033), whereas cerebrospinal fluid was more likely positive for GBS (P = 0.002). All GAS and GBS, and the majority of SP (90%) were sensitive to penicillin. All SP specimens were sensitive to cefotaxime and vancomycin. These infections were associated with high PICU mortality of 43%, 20% and 25%, respectively. Isolation of streptococci was associated with a 30% mortality and high rates of need for mechanical ventilatory and inotropic supports. Patients with GAS, SP or any streptococcal isolation had relative risks [95% confidence interval (CI), P value] of PICU deaths of 7.5 (CI 3.1-18.1, P < 0.0001), 4.5 (CI 2.0-9.8, P < 0.0002) and 5.7 (CI 3.4-9.5, P < 0.0001), respectively. In SP, older children had significantly higher prevalence of premorbid conditions such as malignancy, mental retardation/cerebral palsy ± seizure disorders, chromosomal or genetic disorders (P = 0.003) than children <5 years of age. Serotypes were available for some of these specimens that included 19A, 6B, 3 and 6C. There were four SP deaths with multiorgan system failure and hemolytic uremic syndrome (two 19A and two serotype 3).

CONCLUSIONS

Severe streptococcal infections are associated with significant morbidity and mortality despite treatment with systemic antibiotics and intensive care unit support. GAS and SP affect the lungs of children, whereas GBS more likely causes meningitis in infants. The expanded coverage of newer polyvalent pneumococcal vaccines can probably prevent infections by serotypes 19A, 19F, 6B and 3.

Field evaluation of culture plus latex sweep serotyping for detection of multiple pneumococcal serotype colonisation in infants and young children

Background

Nasopharyngeal swab (NPS) culture by World Health Organisation (WHO) methodology underestimates multiple pneumococcal serotype colonisation compared to a simple culture and latex sweep method. The impacts of this on descriptions of pneumococcal serotype distributions and colonisation dynamics in infancy are not clear.

Methods

8,736 NPS collected from infants enrolled into a longitudinal study were processed to evaluate the field utility of the latex sweep method. 1,107 had previously been cultured by WHO methodology. Additionally, colonisation results were compared in 100 matched pairs of infants, where swabs from an individual were cultured either by WHO or latex sweep method.

Results

In 1,107 swabs cultured by both methods, the latex sweep method was three times more likely to detect colonisation with multiple pneumococcal serotypes than the WHO method (p<0.001). At least one common serotype was identified in 91.2% of swabs from which typeable pneumococci were detected by both methods. Agreement improved with increasing colonisation density (p = 0.03). Estimates of age at first pneumococcal acquisition and colonisation duration were not affected by culture/serotyping method. However, a greater number of serotype carriage episodes were detected in infants cultured by latex sweep (p = 0.03). The overall rate of non-vaccine type pneumococcal acquisition was also greater in infants cultured by latex sweep (p = 0.04).

Conclusions

Latex sweep serotyping was feasible to perform on a large specimen collection. Multiple serotype colonisation detection was significantly improved compared with WHO methodology. However, use of the latex sweep method is unlikely to significantly alter colonisation study serotype distribution or colonisation dynamics results.