Characterization of invasive isolates of Streptococcus pneumoniae among Taiwanese children

Genomic analysis of penicillin-binding proteins and recombination events in an emerging amoxicillin- and meropenem-resistant PMEN3 (Spain9V-3, ST156) variant in Taiwan and comparison with global descendants of this lineage

From 2008 to 2020, the Taiwan National Notifiable Disease Surveillance System database demonstrated that the incidence of non-vaccine serotype 23A invasive pneumococcal disease (IPD) approximately doubled. In this study, 276 non-repetitive pneumococcal clinical isolates were collected from two medical centers in Taiwan between 2019 and 2021. Of these 267 pneumococci, 60 were serotype 23A. Among them, 50 (83%) of serotype 23A isolates belonged to the sequence type (ST) 166 variant of the Spain9V-3 clone. Pneumococcal 23A-ST166 isolates were collected to assess their evolutionary relationships using whole-genome sequencing. All 23A-ST166 isolates were resistant to amoxicillin and meropenem, and 96% harbored a novel combination of penicillin-binding proteins (PBPs) (1a:2b:2x):15:11:299, the newly identified PBP2x-299 in Taiwan. Transformation of the pbp1a, pbp2b, and pbp2x alleles into the β-lactam-susceptible R6 strain revealed that PBP2x-299 and PBP2b-11 increased the MIC of ceftriaxone and meropenem by 16-fold, respectively. Prediction analysis of recombination sites in PMEN3 descendants (23A-ST166 in Taiwan, 35B-ST156 in the United States, and 11A-ST838/ST6521 in Europe) showed that adaptive evolution involved repeated, selectively favored convergent recombination in the capsular polysaccharide synthesis region, PBPs, murM, and folP genome sites. In the late 13-valent pneumococcal conjugate vaccine era, PMEN3 continuously displayed an evolutionary capacity for global dissemination and persistence, increasing IPD incidence, leading to an offset in the decrease of pneumococcal conjugate vaccine serotype-related diseases, and contributing to high antibiotic resistance. A clonal shift with a highly β-lactam-resistant non-vaccine serotype 23A, from ST338 to ST166, increased in Taiwan. ST166 is a single-locus variant of the Spain9V-3 clone, which is also called the PMEN3 lineage. All 23A-ST166 isolates, in this study, were resistant to amoxicillin and meropenem, and 96% harbored a novel combination of penicillin-binding proteins (PBPs) (1a:2b:2x):15:11:299. PBP2x-299 and PBP2b-11 contributed to the increasing MIC of ceftriaxone and meropenem, respectively. Prediction analysis of recombination sites in PMEN3 descendants showed that adaptive evolution involved repeated, selectively favored convergent recombination in the capsular polysaccharide synthesis region, PBPs, murM, and folP genome sites. In the late 13-valent pneumococcal conjugate vaccine era, PMEN3 continuously displays the evolutionary capacity for dissemination, leading to an offset in the decrease of pneumococcal conjugate vaccine serotype-related diseases and contributing to high antibiotic resistance.

Longitudinal investigation of pathogenic bacterial colonization in early childhood: Emphasis on the determinants of Moraxella catarrhalis colonization

BACKGROUND

Moraxella catarrhalis is a common, potential pathogen colonizing the respiratory tract in children. However, there is little information regarding the determinants of M. catarrhalis colonization and disease development.

METHODS

A population-based cohort study was conducted to collect nasopharyngeal swabs from children aged 1, 2, 4, 6, 12, 18, 24, 36, and 60 months for the detection of four common respiratory tract pathogens, including Staphylococcus aureus, M. catarrhalis, Streptococcus pneumoniae, and Haemophilus influenzae. Questionnaires on breastfeeding status were administered during each visit.

RESULTS

A total of 921 children were enrolled between 2012 and 2018. S.aureus was the most common pathogen, although the rates declined during the initial 18 months of life; in contrast, the other three pathogens increased during the first 5 years of life. M. catarrhalis was the second most common colonizing pathogen in all age groups, with prevalence ranging from 0.8% (7/842) at one month to 20.4% (33/162) at 60 months of age. Breastfed children (odds ratio [OR]: 0.56; 95% confidence interval [CI]: 0.35-0.92; P = 0.02) had a lower potential for M. catarrhalis carriage; however, infants with a longer duration of exclusive breastfeeding (OR: 1.12; 95% CI: 1.01-1.25; P = 0.04), especially >12 months of age, had a higher rate of M. catarrhalis carriage.

CONCLUSION

Breastfeeding should be promoted because it may be correlated with a lower risk of M. catarrhalis carriage. However, an extended period of exclusive breastfeeding may be positively associated with M. catarrhalis colonization.

Genomic Insight into the Spread of Meropenem-Resistant Streptococcus pneumoniae Spain23F-ST81, Taiwan

Incidence of invasive pneumococcal disease caused by antimicrobial-resistant Streptococcus pneumoniae types not included in pneumococcal conjugate vaccines has increased, including a penicillin- and meropenem-resistant serotype 15A-ST63 clone in Japan. During 2013-2017, we collected 206 invasive pneumococcal isolates in Taiwan for penicillin and meropenem susceptibility testing. We found serotypes 15B/C-ST83 and 15A-ST63 were the most prevalent penicillin- and meropenem-resistant clones. A transformation study confirmed that penicillin-binding protein (PBP) 2b was the primary meropenem resistance determinant, and PBP1a was essential for high-level resistance. The rate of serotype 15B/C-ST83 increased during the study. All 15B/C-ST83 isolates showed an ermB macrolide resistance genotype. Prediction analysis of recombination sites revealed 12 recombination regions in 15B/C-ST83 compared with the S. pneumoniae Spain^23F-ST81 genome. Pneumococcal clones rapidly recombine to acquire survival advantages and undergo local expansion under the selective pressure exerted by vaccines and antimicrobial drugs. The spread of 15B/C-ST83 is alarming for countries with high antimicrobial pressure.

Molecular epidemiology of Streptococcus pneumoniae isolated from pediatric community-acquired pneumonia in pre-conjugate vaccine era in Western China

BACKGROUND

Streptococcus pneumoniae (S. pneumoniae) is one of the most common pathogens which can cause morbidity and mortality in pediatric infections worldwide. This study aimed to describe the phenotypic and molecular characteristics of community-acquired pneumonia (CAP)-causing S. pneumoniae recovered from children in Western China.

METHODS

We retrospectively enrolled pediatric patients younger than 5 years diagnosed with CAP. All 419 S. pneumoniae isolates were tested for antibiotic susceptibility, serotypes, virulence genes, resistance genes, and sequence types. The potential relationships between molecular characteristics were tested by correspondence analysis.

RESULTS

Most of S. pneumoniae isolates were resistant to erythromycin, tetracycline, clindamycin and trimethoprim-sulfamethoxazole, with 93.8% isolates classified as multidrug resistant. The dominant STs were ST271 (30.8%) and ST320 (12.2%), while the prevailing serotypes were 19F (46.8%), 6B (11.5%), 23F (9.5%) and 19A (9.3%). The coverage rates of PCV-7 and PCV-13 were 73.03% and 86.16%, while the coverage rates of PCV13 among children aged < 1 year and 1-2 years were high in 93.18% and 93.62%. We also observed that CC271 expressed more of mef (A/E), lytA, rlrA and sipA than non-CC271 isolates. Moreover, there were strong corresponding relationships between molecular characteristics.

CONCLUSIONS

The high coverage rate of PCV13 suggests the necessity of introducing the PCV13 vaccine in Western China. Our findings underscore the value of monitoring multiple molecular characteristics to provide new guidance for developing future pneumococcal vaccines.

Serotype Distribution and Antimicrobial Susceptibility of Streptococcus pneumoniae in Pre- and Post- PCV7/13 Eras, Taiwan, 2002-2018

In Taiwan, the 7-valent pneumococcal conjugate vaccine (PCV7) was introduced in 2006 and a PCV13 national childhood catchup program was implemented in 2013. To delineate the trend of serotype distribution and antimicrobial susceptibility following vaccination programs, we investigated a total of 1845 Streptococcus pneumoniae isolates collected biennially between 2002 and 2018 over a 3-month period from 25 hospitals. The number of isolates collected over the years decreased significantly in all age groups, from a total of 320 isolates in 2002 (pre-PCV), to 196 in 2010 (post-PCV7/pre-PCV13), to 89 in 2018 (post-PCV13). Overall, PCV7/PCV13 serotypes comprised 66.9%/76.3%, 53.1%/78.1%, and 15.7%/31.5% of isolates in 2002, 2010, and 2018, respectively. The leading serotypes in the pre-PCV era were 23F, 19F, 6B, and 14, while serotype 19A predominated in the post-PCV7/pre-PCV13 era, but non-vaccine serotypes (NVT) 15A (18.0%) and 23A (15.7%) surpassed 19A (10.1%) to become the top two leading serotypes in 2018. All the major serotypes, including the emergent serotypes 15A and 23A, were multidrug-resistant with high rates of non-susceptibility to β-lactam (except serotype 3) and several non-β-lactam agents. PFGE and MLST revealed that while meropenem-susceptible serotype 15A-ST3058 isolates and a serotype 23A-ST338 clone existed in earlier years, rise and spread of meropenem-non-susceptible serotype 15A-ST63 and serotype 23A-ST166 clones occurred in recent years. We conclude that successive implementation of PCVs has led to a marked decrease in pneumococcal isolate burden, but the replacement by meropenem-non-susceptible NVT 15A and 23A highlights the need for continued local surveillance to track pneumococcal evolution in each region to help vaccine polyvalency decisions.

Longitudinal investigation of nasopharyngeal pneumococcal carriage in early childhood: The PATCH birth cohort study

Streptococcus pneumoniae is a common cause of infectious diseases such as pneumonia and sepsis. Its colonization is thought to be the first step in the development of invasive pneumococcal diseases. This study aimed to investigate pneumococcal colonization patterns in early childhood. A longitudinal birth cohort study was conducted for investigating nasopharyngeal colonized pneumococci at 1, 6, 12, 18, 24, and 36 months of age, particularly focusing on the serotype distribution and antimicrobial susceptibilities. Pneumococcal conjugate vaccine (PCV) effect on nasopharyngeal colonization was also assessed. During 2013-2017, 855 infants were enrolled and a total of 107 isolates were recovered from 95 infants during the first three years of life. In this period, the prevalence of pneumococcal colonization increased, with values ranging from 0.2% (2/834) at 1 month of age to 5.9% (19/323) at 36 months of age. The investigation of serotype revealed that 81.1% (73/90) belonged to the non-PCV13 serotypes-23A, 15A, 15C, and 15B. Moreover, PCV13 serotypes significantly decreased during 2014-2015, when routine PCV13 vaccination was initiated in Taiwan. PCV13 introduction may lead to the reduction in the rates of pneumococcal isolates resistant (R) to penicillin. Under conditional PCV13 vaccination, pneumococcal isolates primarily belonged to non-PCV13 serotypes. This non-PCV13 serotype replacement exhibited lower rates of penicillin R isolates, suggesting that PCV13 administration may reduce the antibiotic-nonsusceptible pneumococcal disease burden and antibiotic use.

Predictive value of Thomsen-Friedenreich antigen activation for Streptococcus pneumoniae infection and severity in pediatric lobar pneumonia

BACKGROUND

Most cases of complicated pneumonia in children are caused by pneumococcal infections. Thomsen-Friedenreich antigen (TA) is present on erythrocytes, platelets and glomeruli, and it can be activated during pneumococcal infection. The aim of this study was to investigate the predictive value of TA activation for pneumococcal infection and association with the severity of complicated pneumonia.

MATERIALS AND METHODS

Patients with lobar pneumonia were routinely tested for TA at the Department of Pediatrics, Mackay Memorial Hospital from January 2010 to December 2015. We retrospectively reviewed and analyzed their charts and data including age, sex, etiology of infection, chest tube insertion or video-assisted thoracoscopic surgery, length of hospital stay, TA activation, white blood cell count and level of C reactive protein.

RESULTS

A total of 142 children with lobar pneumonia were enrolled, including 35 with empyema, 31 with effusion, 11 with necrotizing pneumonia and four with lung abscess. Streptococcus pneumoniae was the most commonly identified pathogen. Twenty-two patients (15.4%) had activated TA, all of whom were infected with S. pneumoniae. TA activation had 100% specificity and 100% positive predictive value for pneumococcal infection. In the multivariate analysis in lobar pneumonia, TA activation (OR, 15.8; 95% CI, 3.0-83.5; p = 0.001), duration of fever before admission (OR, 1.2; 95% CI, 1.1-1.5; p = 0.013) and initial CRP level (OR, 1.1; 95% CI, 1.0-1.1; p = 0.004) were independent predictors of empyema.

CONCLUSIONS

TA activation is a specific marker for pneumococcal pneumonia and might indicate higher risk for complicated pneumonia.

Pneumococcal vaccination and efficacy in patients with heterotaxy syndrome

BackgroundPneumococcal vaccines, including pneumococcal polysaccharide vaccine (PPV) and pneumococcal conjugated vaccine (PCV), are crucial in preventing invasive pneumococcal diseases. We analyzed the pneumococcal vaccination rate, efficacy, and durability in patients with heterotaxy.MethodsAll patients with heterotaxy and CCHD who were followed up at our institution between 2010 and 2015 were included. Pneumococcal vaccine status and geometric mean concentration (GMC) of serotypes 6B, 14, 19F, and 23F were analyzed. Splenic function was considered abnormal when the percentage of IgM memory B cell was less than 1%.ResultsThe GMCs of the four serotypes did not differ significantly between patients with heterotaxy and those with CCHD; the GMCs were also not affected by abnormal splenic function. Most patients had GMCs >0.35 μg/ml (protection level) 4-5 years after either PPV or PCV injection; however, it may decay gradually in some serotypes. In addition, 21.4% of 42 patients with heterotaxy did not receive pneumococcal vaccine, and none completely adhered to the vaccine guidelines.ConclusionsVaccine efficacy was acceptable, even in patients with abnormal splenic function. In some patients, the durability of PPV and PCV decreased with time, highlighting the importance of booster doses. Vaccination rate in patients with heterotaxy is unsatisfactory.

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.

Community-Acquired Pneumonia in the Asia-Pacific Region

Community-acquired pneumonia (CAP) is an important cause of mortality and morbidity worldwide. Aging population, dense urbanization, and poor access to health care make the Asia-Pacific region vulnerable to CAP. The high incidence of CAP poses a significant health and economic burden in this region. Common etiologic agents in other global regions including Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Chlamydophila pneumoniae, Staphylococcus aureus, and respiratory viruses are also the most prevalent pathogens in the Asia-Pacific region. But the higher incidence of Klebsiella pneumoniae and the presence of Burkholderia pseudomallei are unique to the region. The high prevalence of antimicrobial resistance in S. pneumoniae and M. pneumoniae has been raising the need for more prudent use of antibiotics. Emergence and spread of community-acquired methicillin-resistant S. aureus deserve attention, while the risk has not reached significant level yet in cases of CAP. Given a clinical and socioeconomic importance of CAP, further effort to better understand the epidemiology and impact of CAP is warranted in the Asia-Pacific region.

Clinical and microbiological characterization of serotype 6D pneumococcal infections in South Korea

BACKGROUND

The prevalence of Serotype 6D Streptococcus pneumoniae was reported relatively high in South Korea. Since the introduction of 7-valent pneumococcal conjugate vaccine (PCV7), serotype replacement was observed. This study was designed to better clarify genetic diversity of pneumococcal serotype 6D and its clinical characteristics after introduction of PCV7 in 2000.

METHODS

We performed serotyping analysis with 1298 pneumococcal isolates from clinical specimens in South Korea from 2004 to 2011. Multilocus sequence typing was performed, and minimal inhibitory concentration was determined for the available serotype 6D and nontypeable (NT) pneumococcal isolates during the 2006-2007 period.

RESULTS

The proportion of serotype 6D pneumococci increased from 0.8% (2004-2007) to 2.9% (2008-2011) of all clinical pneumococcal isolates, accounting for 14.9% of serogroup 6 pneumococci in South Korea. NT pneumococci markedly increased to 13.3% during 2006-2007 in advance of the increase in serotype 6D. Among the 26 available serotype 6D pneumococcal isolates, ST282 was predominant (23 isolates, 88.5%). The STs of NT pneumococci (26 isolates) were diverse, but clonal complex 271 was the dominant clone. The oral penicillin non-susceptibility rate was 92.3% (24 among 26 isolates) for both serotype 6D and NT pneumococci. The ceftriaxone non-susceptibility rates of serotype 6D and NT pneumococci were 7.7% and 3.8%, respectively.

CONCLUSION

ST228(6D) strain expanded, particularly among old adults with comorbidities in South Korea. Both antibiotic and PCV7 pressure might have contributed to the selective increase of NT and serotype 6D pneumococci.

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.

Low immunoglobulin M memory B-cell percentage in patients with heterotaxy syndrome correlates with the risk of severe bacterial infection

BACKGROUND

Patients with heterotaxy syndrome, commonly associated with complex congenital heart disease (CHD), exhibit a higher risk of severe bacterial infection (SBI). We sought to define the change of a novel immunologic marker, the immunoglobulin M (IgM) memory B-cell percentage, and its association with SBI.

METHODS

We enrolled 46 (M/F 29/17) heterotaxy syndrome patients (42 right atrial isomerism (RAI) and 4 left atrial isomerism (LAI)) aged > 1 y during the period 2010-2012 in a tertiary care center. We analyzed IgM(+)CD27(+) memory B-cell percentages. Patients with simple and complex CHD served as controls.

RESULTS

The mean IgM memory B-cell percentages were the lowest in the heterotaxy syndrome group, compared with those in complex and simple CHD groups (1.8 ± 2.1 vs. 3.9 ± 3.2 vs. 5.1 ± 4.7, P < 0.001). In the heterotaxy syndrome group, 41.3% had low IgM memory B-cell percentages (<1% of B cells). Seven had a history of community-acquired SBI and 85.7% of these had low IgM memory B-cell percentages, which was the only significant factors related to community-acquired SBI (P = 0.028).

CONCLUSION

The memory B cell and IgM memory B-cell percentages are low in patients with heterotaxy syndrome, and the presence of IgM memory B-cell percentage < 1% correlates with community-acquired SBI.

Evolving pneumococcal serotypes and sequence types in relation to high antibiotic stress and conditional pneumococcal immunization

In Taiwan, beginning in 2013, the 13-valent pneumococcal conjugate vaccine (PCV13) was provided free of charge to children 2–5 years of age. In 2014, this was extended to children 1–5 years old. During 2012–2014, 953 cases of culture-confirmed pneumococcal disease (CCPD), including 104 invasive pneumococcal disease (IPD), were prospectively identified and analyzed at a 3,700-bed hospital in Taiwan. From 2012 to 2014, the incidence per 10,000 admissions decreased from 26.7 to 20.4 for CCPD (P < 0.001) and from 3.2 to 1.9 for IPD (P < 0.05). Significant reduction of PCV13 serotypes was firstly noted in children in 2013 and extended to both paediatric and adult populations in 2014. Simultaneously, the incidence per 10,000 admissions of non-PCV13 serotypes increased from 6.1 in 2012 to 9.3 in 2014 (P < 0.005). The most prevalent non-PCV13 serotypes were 15A, 15B, and 23A, each containing a predominant clone, ST63^15A, ST83^15B, and ST338^23A. From 2012 to 2014, isolates with penicillin minimum inhibitory concentrations >2 mg/L decreased from 27.8% to 8.1% (P < 0.001) among all isolates. PCV13 immunization in young children demonstrated an early protective effect in all ages. However, in the elderly, the effect was compromised by an emergence of non-PCV13 serotypes.

Pneumococcal disease and use of pneumococcal vaccines in Taiwan

The use of pneumococcal vaccine plays an important role for prevention of invasive pneumococcal disease (IPD). However, introducing the pneumococcal vaccine into the national immunization program (NIP) is complex and costly. The strategy of progressively integrating the pneumococcal conjugate vaccine (PCV) into the NIP in Taiwan provides valuable experience for policy makers. The 7-valent PCV (PCV7) was first available in Taiwan in late 2005. PCV7 was first provided free to children with underlying diseases, those in vulnerable socioeconomic status, and those with inadequate health care resources. The catch-up immunization program with the 13-valent PCV was launched in 2013 and the national pneumococcal immunization program was implemented in 2015. Children aged 2-5 years had the highest incidence of IPD among pediatric population in Taiwan. Although the incidence of IPD caused by PCV7 serotypes has declined, the overall incidence of IPD remained high in the context of PCV7 use in the private sector. A surge of IPD caused by serotype 19A occurred, accounting for 53.6% of IPD cases among children aged ≤ 5 years in 2011-2012. After the implementation of the national pneumococcal immunization program, serogroup 15 has become the leading serogroup for IPD in children. Continued surveillance is necessary to monitor the serotype epidemiology in Taiwan.

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.

Serotype and genotype distribution among invasive Streptococcus pneumoniae isolates in Colombia, 2005-2010

In Colombia, a laboratory-based surveillance of invasive Streptococcus pneumoniae isolates as part of SIREVA II PAHO has been conducted since 1994. This study describes the serotype distribution, antimicrobial resistance, and genetic relationships of pneumococcal isolates recovered in Colombia from 2005 to 2010. In this study, demographic data of invasive S. pneumoniae isolates were analyzed, and antimicrobial susceptibility patterns were determined. Pulse field gel electrophoresis (n = 629) and multilocus sequence typing (n = 10) were used to determine genetic relationship of isolates with minimal inhibitory concentration to penicillin ≥0.125 µg/mL. A total of 1775 isolates of S. pneumoniae were obtained. Fifteen serotypes accounted for 80.7% of isolates. Serotype 14 (23.1%) was the most frequent in the general population. Penicillin resistance was 30.7% in meningitis and 9.0% in non-meningitis. Clones Spain^6BST90, Spain^9VST156, Spain^23FST81, and Colombia^23FST338 were associated to isolates. Additionally, serotype 6A isolates were associated with ST460 and ST473, and 19A isolates with ST276, ST320, and ST1118. In conclusion, the surveillance program provided updated information of trends in serotype distribution, antimicrobial resistance and the circulation of clones in invasive pneumococcal diseases. These results could be helpful to understand the epidemiology of S. pneumoniae in Colombia, and provide a baseline to measure the impact of vaccine introduction.

Expansion and evolution of Streptococcus pneumoniae serotype 19A ST320 clone as compared to its ancestral clone, Taiwan19F-14 (ST236)

BACKGROUND

The Streptococcus pneumoniae serotype 19A sequence type (ST) 320 clone, derived from an international Taiwan(19F)-14 (ST236) clone, has become prevalent in many countries.

METHODS

The dynamics of invasive pneumococcal disease (IPD) were determined using the database of the National Notifiable Disease Surveillance System in Taiwan. The virulence of 19A ST320 and Taiwan(19F)-14 (ST236) were assessed in mice. By constructing an isogenic serotype 19F variant of the 19A ST320 strain (19F ST320), we analyzed the role of capsular type and genetic background on the difference in virulence between 19A ST320 and Taiwan(19F)-14 (ST236).

RESULTS

Between 2008 and 2011, IPD due to serotype 19A increased from 2.1 to 10.2 cases per 100 000 population (P < .001); IPD due to any serotype also significantly increased (P = .01). Most serotype 19A isolates belonged to ST320. Using competition experiments in a murine model of colonization, we demonstrated that 19A ST320 outcompeted Taiwan(19F)-14 (ST236; competitive index, 20.3; P = .001). 19F ST320 was 2-fold less competitive than the 19A ST320 parent (competitive index, 0.47; P = .04) but remained 14-fold more competitive than Taiwan(19F)-14 (ST236; competitive index, 14.7; P < .001).

CONCLUSIONS

Genetic evolution of pneumococcal clones from Taiwan(19F)-14 (ST236) to 19A ST320 has made this pneumococcus better able to colonize of the nasopharynx. This evolution reflects not only a switch in capsular serotype but also changes in other loci.

Genotype replacement within serotype 23FStreptococcus pneumoniaein Beijing, China: characterization of serotype 23F

We investigated the genetic structure of 99 isolates of serotype 23FStreptococcus pneumoniaefrom children with acute respiratory infections collected over two periods from 1997 to 2006, and 2010. All isolates were susceptible to vancomycin and amoxicillin–clavulanic acid; 97 were resistant to erythromycin, 95 of which carried theermBgene and two carried bothmefA/EandermBgenes. Multidrug resistance to three or more classes of antibiotics was exhibited by 90 isolates. Sequence types ST342 and ST81 were the most frequent in 1997–2006 and 2010, respectively. All CC81 isolates were non-susceptible to β-lactam antibiotics and had higher minimum inhibitory concentration values for penicillin than other clone complexes and sequence types. The increased β-lactam antibiotic resistance may have resulted from the replacement of multidrug-resistant clones related to ST81. Long-term studies onS. pneumoniaeserotype 23F, especially the ST81 clone, should be conducted to better understand the epidemiological picture of this pathogen in China.

Comparison of invasive pneumococcal disease caused by serotype 19A and non-19A pneumococci in children: more empyema in serotype 19A invasive pneumococcal disease

OBJECTIVE

To delineate whether serotype 19A invasive pneumococcal disease (IPD) comprised significantly more necrotizing pneumonia and empyema in children, we compared the clinical characteristics between serotype 19A and non-19A IPD.

METHODS

Between January 2007 and December 2011, cases of children with IPD who were treated at the National Taiwan University Hospital were reviewed. Patients were assigned to the 19A group or the non-19A group based on the serotype. Their demographic data, clinical course, laboratory results, diagnosis, complications, and sequelae were collected and analyzed.

RESULTS

Overall, 27 patients were included in the 19A group and 29 patients in the non-19A group. Compared with non-19A group, serotype 19A tended to cause IPD in patients without major underlying diseases (p = 0.015). Bacteremia without pneumonia or meningitis was found more frequently in the non-19A group (45% vs. 11%, p = 0.01), and pneumonia with or without empyema occurred significantly more frequently in the 19A group (89% vs. 52%, p = 0.006). Patients in the19A group had longer duration of fever (12 vs. 3 days, p = 0.01), and required more intensive care (78% vs. 41%, p = 0.01) and more video-assisted thoracoscopic surgery (74% vs. 28%, p = 0.001).

CONCLUSION

In comparison with the other serotypes, serotype 19A IPD has significantly more empyema which required more video-assisted thoracoscopic surgery and more intensive care.

Necrotizing pneumonia caused by nanC-carrying serotypes is associated with pneumococcal haemolytic uraemic syndrome in children

Streptococcus pneumoniae infection is a leading cause of morbidity and mortality worldwide. One of the most severe complications of invasive pneumococcal disease (IPD) is haemolytic uraemic syndrome (HUS). This study was undertaken to determine the risk factors and role of pneumococcal neuraminidases in HUS in children with IPD. Eighteen cases of HUS and 54 patients with IPD without HUS were identified. The controls were patients with culture-confirmed IPD without HUS. Clinical and laboratory characteristics of the two groups of patients were compared. Bacterial isolates from both groups were serotyped, sequence typed and examined for their carriage of three neuraminidase genes. Necrotizing pneumonia and serotype 3 infection were significantly associated with HUS in children with IPD, suggesting that a severe pulmonary suppurating disease increase the risk of HUS. Serotype 14 was associated with necrotizing pneumonia but not HUS. Children with HUS were more likely to require surgery and had a longer duration of hospitalization. The study identified a significantly higher carriage of a neuraminidase gene, nanC, in the causative pneumococcal isolates from patients with HUS (89% versus 41%, p 0.001). The sensitivity and specificity of nanC to predict HUS were 89% and 59%, respectively. In conclusion, necrotizing pneumonia, serotype 3 infection and neuraminidase gene nanC were associated with HUS in children with IPD. The result suggests that NanC could provide an additive effect to NanA and NanB in the overall activity of pneumococcal neuraminidases to expose Thomsen-Friedenreich antigen on various cells in patients with HUS.

Nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, and Alloiococcus otitidis in young children in the era of pneumococcal immunization, Taiwan

We applied a multiplex polymerase chain reaction (PCR) and culture to detect Streptococcus pneumoniae and detected 3 other respiratory pathogens--Haemophilus influenzae, Moraxella catarrhalis, and Alloiococcus otitidis--simultaneously by PCR, in the nasopharynx of 386 children aged under 5 y. S. pneumoniae was the most common pathogen carried by children in all age groups, with the rate ranging from 15.8% in children aged 3-4 y to 28.6% in children aged 2-3 y. H. influenzae and M. catarrhalis showed similar carriage rates across all the age groups. Only 2 young children (0.5%) carried A. otitidis. Higher carriage of S. pneumoniae was found in children who had not received the heptavalent pneumococcal conjugate vaccine (PCV7). Cefotaxime non-susceptibility was high (51.4%) in S. pneumoniae nasopharyngeal isolates. Serotype 6B was the most common in fully immunized carriers and also in those who received catch-up immunization. Due to low PCV7 coverage in Taiwan, the carriage of vaccine and non-vaccine serotypes of S. pneumoniae in children remains common.

Necrotizing pneumococcal pneumonia with bronchopleural fistula among children in Taiwan

BACKGROUND

Severe necrotizing pneumococcal pneumonia may progress to the development of bronchopleural fistula (BPF). The purpose of this study was to describe the clinical courses and identify risk factors for the development of bronchopleural fistula in children with pneumococcal pneumonia. Histopathologic features of children receiving surgical resections of the lung because of BPF were analyzed to explore the pathogenesis of destructive lung disease caused by Streptococcus pneumoniae.

METHODS

A total of 112 cases of culture-proven pneumococcal pneumonia were identified between January 2001 and March 2010 at Chang Gung Children's Hospital. The medical charts of all cases of culture-proven pneumococcal pneumonia were reviewed.

RESULTS

Pneumococcal pneumonia in 18 children (18/112, 16.1%) was complicated by BPF. As compared with children without BPF, children with BPF had significantly lower white blood cell counts at admission (P = 0.03) and significantly longer durations of fever and hospitalization (P < 0.001). Multivariate analysis revealed that acute respiratory failure (odds ratio = 8.9; 95% confidence interval = 2.6-30.9; P = 0.001) and serotype 19A infection (odds ratio = 5.0; 95% confidence interval = 1.2-22.1; P = 0.03) were risk factors for the development of BPF. Histopathologic analyses were available for 12 children who underwent surgical resections of the lung. Coagulative necrosis with pulmonary infarction was found in 11 of the 12 cases.

CONCLUSIONS

Serotype 19A was strongly associated with BPF. Vaccines containing this serotype will be important for prevention.

Nasopharyngeal carriage of Streptococcus pneumoniae in Taiwan before and after the introduction of a conjugate vaccine

BACKGROUND

The heptavalent pneumococcal conjugate vaccine was introduced in Taiwan in October 2005. To evaluate the effect of the vaccination, we conducted an active, prospective, large-scale, long-term, and multicenter study to assess the prevalence of nasopharyngeal Streptococcus pneumoniae carriage in Taiwanese children.

METHODS

This study was performed at three tertiary teaching hospitals in northern, central, and southern Taiwan. Questionnaires provided demographic, family/household, and medical history data. Pneumococcal isolates were tested for their susceptibility to various antimicrobial agents and serotypes. In addition, influenza virus and Staphylococcus aureus were recovered from nasopharyngeal and nasal swabs, respectively.

RESULTS

Between July 2005 and July 2008, 857 pneumococcal strains were recovered from a total of 6057 children aged >2 months to 5 years (carriage rate, 14.1%). Carriage rates differed geographically and varied with subject age. In a multivariate analysis, having at least one sibling, attendance at day-care centers, a history of otitis media, and history of upper respiratory tract infection in the previous 2 weeks were each associated with a higher risk of pneumococcal colonization of the nasopharynx. Staphylococcus aureus nasal colonization was inversely associated with nasopharyngeal carriage of pneumococcus (p=0.000; odds ratio [OR]: 0.48; 95% CI: 0.39-0.58). Daycare attendance was the only risk factor for carriage of penicillin non-susceptible S. pneumoniae (OR: 2.37; 95% CI: 1.22-4.88). Although vaccination rates rose from 2005 to 2008, no concomitant decrease in S. pneumoniae carriage occurred. The rate of penicillin resistance among S. pneumoniae isolates was 92.8% (using the meningitis criteria). The prevalence of cefotaxime resistance (21.6%) was higher than that of penicillin (6.9%; non-meningitis criteria). Slightly more than half (57.4%) of the isolates belonged to strains covered by the heptavalent pneumococcal conjugate vaccine when both vaccine and vaccine-related serotypes were included.

CONCLUSIONS

Although vaccination rates rose from 2005 to 2008, no concomitant decrease occurred in S. pneumoniae carriage. Interaction between S. aureus and S. pneumoniae may influence vaccination efficacy. These findings provide baseline data to further compare pneumococcal carriage rates and antibiotic resistance patterns in Taiwanese children as vaccination rates continue to increase.

Sequence types and antimicrobial susceptibility of invasive streptococcus pneumoniae isolates from a region with high antibiotic selective pressure and suboptimal vaccine coverage

Multilocus sequence typing was carried out on 95 invasive pneumococcal isolates belonging to the most common 7 serotypes currently circulating in Taiwan. The study confirmed continued prevalence in Taiwan of a few global clones and sequence types (STs) since the mid-1990s and identified the recent emergence of ST320 (19A) and ST902 (6A). Antimicrobial nonsusceptibility was common in the predominant STs of serotypes 14, 19A, 19F, and 23F.

The epidemiology of hospitalized children with pneumococcal/lobar pneumonia and empyema from 1997 to 2004 in Taiwan

Pneumococcal/lobar pneumonia and empyema have an important impact on the health of children worldwide. There has been no epidemiological study of pneumococcal/lobar pneumonia and empyema in Taiwan, a middle-income Asian population. Using Taiwan's National Health Insurance database, we collected and analyzed data obtain from medical care claims related to pneumococcal/lobar pneumonia and empyema for children below the 18 years old from 1997 to 2004. We found the annual population-based incidence to have significant year to year increases and the average annual incidences of pneumococcal/lobar pneumonia and empyema in children under five to be 44.9 and 10.5 episodes per 100,000 children-year, respectively. About 64% of children with pneumococcal/lobar pneumonia and empyema were under 5 years old. Children 4 to 5 years old had the highest incidences of both pneumococcal/lobar pneumonia and empyema. Incidence was the highest each spring. The odds ratio of the case fatality among pneumococcal/lobar pneumonia patients complicated with empyema to those without was 118 (95% confidence interval 28-492). In conclusion, the population-based incidences of pneumococcal/lobar pneumonia and empyema among children under five in Taiwan were 44.9 and 10.5 episodes per 100,000 children-year, respectively, and 4- to 5-year-old children had the highest incidences of both pneumococcal/lobar pneumonia and empyema. This population might benefit from a universal pneumococcal vaccination program which might cover about 70% of invasive pneumococcal diseases in Taiwanese children under 5 years old.