Serotype distribution and antimicrobial resistance patterns of Streptococcus pneumoniae isolated from children in China younger than 5 years

This study examined the epidemiology, antibiotic susceptibility, and serotype distribution of Streptococcus pneumoniae associated with invasive and noninvasive pneumococcal disease in children in China. A total of 451 clinical isolates from children (age, <5 years) were collected from 8 cities from January 2005 to December 2006, including 31 isolated from invasive disease. In vitro susceptibility to 14 antimicrobial agents was determined by the agar dilution method. Among all isolates tested, 64.3% were resistant to penicillin, and for invasive isolates, the resistance rate was 55.2%. Isolates from Wuhan and Nanjing showed the highest prevalence of penicillin resistance (89.6% and 85%), followed by those from Shenzhen (72.4%) and Chengdu (56.7%). Multidrug resistance rates to tetracycline, erythromycin, and clindamycin reached 90%. The 6 most common serotypes were 19F, 19A, 14, 6B, 23F, and 15. These accounted for 80.7% of the isolates. Resistance to penicillin varied among the 6 leading serotypes, ranging from 20% in serotype 15 to 87.3% in serotype 19F. Each of the 8 cities had different serotype distribution. The potential coverage by 7-, 10-, and 13-valent pneumococcal conjugate vaccine were 63.6%, 64.8%, and 79.6%, respectively.     

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

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

The prevalence and characteristics of Streptococcus pneumoniae isolates expressing serotypes 6C and 6D in Hong Kong prior to the introduction of the 7-valent pneumococcal conjugate vaccine

A study was conducted to determine the prevalence of the 2 newly described types, 6C and 6D, among pneumococcal isolates collected in Hong Kong before availability of the 7-valent pneumococcal conjugate vaccine. A total of 154 serogroup 6 isolates obtained from nasopharynx (n = 106), blood (n = 22), respiratory (n = 24), and cerebrospinal fluid (CSF) (n = 2) during 1995 to 2001 were analyzed by polymerase chain reaction typing. Five nasopharyngeal and 2 sputum isolates were found to belong to 6C and 6D, respectively. The isolates were genetically diverse, but one 6C and two 6D isolates exhibited some clonal relationship. Phylogenetic analysis of the wchA-wciN(β)-wciO nucleotide sequences showed that the Hong Kong 6C/6D isolates had 2 allelic profiles, which were more closely related to 6C/6D isolates from Fijian and Korea than were those from Brazil and the United States. However, all of the wciP gene sequences for both Hong Kong and non-Hong Kong isolates clustered together: 6C isolates with the wciP-9 allele and 6D isolates with the wciP-5 allele. In conclusion, the prevalence of the 2 newly described serotypes was low before the era of the pneumococcal conjugate vaccine. Nonetheless, results from the molecular studies indicated that the evolution of the capsular genes have involved complex pathways.     

Changes in nasopharyngeal carriage and serotype distribution of antibiotic-resistant Streptococcus pneumoniae before and after the introduction of 7-valent pneumococcal conjugate vaccine in Hong Kong

This study assessed the changes in serotype distribution and antibiotic resistance of Streptococcus pneumoniae isolates in children before and after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7) in Hong Kong. Nasopharyngeal specimens were collected from 1978 and 2211 children (ages, 2 to 6 years) attending day care centers or kindergartens in period 1 (1999-2000) and period 2 (2009-2010), respectively. Carriage of PCV7 serotypes decreased from 12.8% to 8.6% (P < 0.01). The relative contribution of PCV7 serotypes 14 and 18C had decreased, whereas that for non-PCV7 serotypes 19A, 6A, 6C, 23A, and 15B had increased. In period 2, PCV7 penetration rate (at least 1 dose) for children aged 2, 3, 4, and 5 years was 43%, 35.7%, 26.7%, and 20.4%, respectively. In multivariate analysis, PCV7 use was the only independent variable associated with fewer PCV7 serotype carriages (odds ratio 0.5; P = 0.001). In period 2, high rates of dual penicillin/erythromycin nonsusceptibility were found in serotypes 6B (77.3%), 14 (100%), 19F (100%), 23F (78%), 19A (75%), 6A (87.8%), 6C (59.3%), and 23A (78.9%).     

Changes of serotype and genotype in Streptococcus pneumoniae isolates from a Korean hospital in 2007

We investigated the change in clones and serotypes of Streptococcus pneumoniae isolates in a Korean tertiary-care hospital. Serotypes of S. pneumoniae isolates were determined by the capsular quellung method, and in vitro susceptibility testing was performed by broth microdilution method. Multilocus sequence typing was performed to determine the genotypes of the S. pneumoniae isolates. The erm(B) and mef(A) genes in erythromycin-resistant isolates were also detected using the duplex polymerase chain reaction method. During the 2 periods assayed (1998–2000 and 2007), 7-valent pneumococcal conjugate vaccine (PCV7) serotypes decreased significantly from 58.3% to 30.9% (P = 0.001). Especially, serotypes 19F and 23F decreased significantly from 31.7% to 8.5% (P < 0.0001) and from 20.0% to 7.4% (P = 0.021), respectively. In contrast to the other PCV7 serotypes, serotype 14 coupled with CC554 emerged in 2007, which may indicate no effect of PCV7 against serotype 14 isolates from Korea and the possibility of a different subtype. Of the non- PCV7 serotypes, serotype 19A increased from 8.3% to 14.9% (P = 0.227) and serotype 15 increased from 0% to 8.5% (P = 0.023). The increase of serotype 19A was due to the expansion of a preexisting clone with serotype 19A, ST320. However, S. pneumoniae isolates of serotype 15 showed diverse STs. Our data may provide helpful information in local vaccine serotype expansion or replacement in Korea.     

Comparative in vitro activities of carbapenem antimicrobial agents against 264 penicillin-resistant Streptococcus pneumoniae isolates from Korea

We compared in vitro activities of carbapenems against 264 penicillin-resistant Streptococcus pneumoniae (PRSP) isolates. The MIC(50)/MIC(90) (microg/mL) values of imipenem, meropenem, ertapenem, and panipenem were 1/1, 0.25/0.25, 0.25/0.5, and 0.125/0.25, respectively. The susceptibility rates to imipenem, meropenem, and ertapenem were 0%, 85.2%, and 99.6%, respectively. Compared with imipenem and meropenem, ertapenem and panipenem had better in vitro activities against PRSP.     

Pneumococcal Vaccination in Europe: Schedule Adherence

Nonadherence to recommended pneumococcal conjugate vaccine (PCV) schedules may have implications for protection against pneumococcal disease. In this commentary, we have assessed adherence to the recommended dosing schedules (the completion of the primary PCV and booster series) in different European countries. We found that adherence with the PCV schedule was lower than that for diphtheria-tetanus-acellular pertussis (DTaP) and that higher adherence was observed in countries where PCV vaccination is recommended and funded. Adherence with the booster dose is often lower than that with the primary series completion, and it is often given after the recommended age. These data highlight the need to encourage timely vaccination of children with PCV, in line with local immunization schedules. There is no single solution to improve adherence; actions need to be tailored to the context of individual countries through initiatives at the national, regional, and local levels and should target different stakeholders.     

Streptococcus pneumoniae resistance to penicillin and other β-lactam antibiotics from isolates at a university hospital in Taiwan

The in vitro susceptibility to 9 β-lactam antibiotics of 65 clinical strains ofStreptococcus pneumoniae collected from a teaching hospital in Taiwan during the period from 1989 to 1994 were studied. Minimum inhibitory concentrations (MIC) were determined by the agar dilution method with 5% horse blood. Intermediate resistance to penicillin G was found in 24.6% of the strains (MIC, 0.125 to 1 μg/mL) and 7.7% of the strains were fully-resistant to penicillin G (MIC, ≥2 μg/mL). Ten strains (15.4%) were fully-resistant to cefotaxime (MIC, ≥2 μg/mL), whereas 3 strains (4.6%) showed intermediate resistance (MIC 1 μg/mL). The intermediate- and fully-resistant rates for penicillin increased from 12.5% and 0% in the period 1989 to 1991 to 27.3% and 22.7% in 1994, respectively. The rate of strains intermediately- and fully-resistant to cefotaxime increased from 0% in the period 1989 to 1991 to 9.1% and 22.7% in 1994, respectively. There was also a high probability of resistance to cefotaxime in strains that were intermediately- or fully-resistant to penicillin G.     

Pharmacokinetics-pharmacodynamics of quinolones against Streptococcus pneumoniae in patients with community-acquired pneumonia

Exposure-response analyses were performed using data from 89 patients (10 clinical trials) with Streptococcus pneumoniae community-acquired pneumonia who received quinolones. Relationships between the free-drug AUC/MIC ratio and clinical and microbiologic response were identified. Such data may be useful to establish prior expectations for the no-treatment effect when conducting noninferiority clinical trials.     

2000-2009年同济医院肺炎链球菌的耐药性分析

目的 了解肺炎链球菌的耐药情况及变化趋势.方法 收集同济医院2000年1月1日至2009年12月31日分离的753株肺炎链球菌,主要分离自呼吸道标本,其次为血液和脑脊髓液标本.采用E-test法检测分离株对青霉素及头孢曲松的MIC,其余采用纸片扩散法进行抗菌药物敏感性试验.结果 10年来总的非脑膜炎来源PNSSP占23.8%(93/392),儿童PNSSP占26.4%(47/178),成人PNSSP占16.8%(36/214),差异具有统计学意义(χ2=7.642,P＜0.01).10株脑膜炎标本来源肺炎链球菌均为PRSP.莫西沙星、左氧氟沙星对肺炎链球菌仍然保持着良好的敏感性,敏感率分别为96.9%(720/743)和90.5%(672/743),未发现万古霉素和美罗培南耐药菌株.肺炎链球菌对大多数抗菌药物的耐药性均有不同程度升高,尤其是青霉素、红霉素及克林霉素敏感性下降尤为明显.2006年PNSSP仅19%(19/99),2009年上升为30%(35/114);2000年红霉素敏感性为22%(28/125),至2009年仅为3%(3/114);2004年克林霉素的敏感性为40%(13/32),至2009年仅为4%(5/114).结论 2000-2009年同济医院分离的肺炎链球菌对青霉素、红霉素及克林霉素的耐药性呈上升趋势,尤其是儿童对此3种抗菌药物的耐药性明显高于成人分离株.临床应结合药敏试验结果合理选择抗菌药物.

Abstract：

Objective To investigate antibiotic resistance and resistant trend of Streptococcus pneumonia. Methods To investigate 753 Streptococcus pneumoniae isolated from Tongji Hospital in recent 10 years from January 1st 2000 to December 31st 2009, most of them were from respiratory tract specimens,followed by blood and cerebrospinal fluid. The MIC to penicillin & cefatriaxone were determined by E-test,and other antimicrobial susceptibility were tested by Kirby-Bauer method. Results For non-cerebrospinal fluid specimen, the total rate of PNSSP was 23.8%( 93/392 ), it was significant different between the rate of PNSSP from children ( 26. 4%, 47/178 ) and adults ( 16. 8%, 36/214, χ2 = 7. 642, P ＜ 0. 01 ). All of 10 strains isolated from cerebrospinal fluid were PRSP. Most isolates were high-susceptive to moxifloxacin and levofloxacin, and the rate of susceptibility were 96. 9% ( 720/743 ) and 90. 5% ( 672/743 )respectively. None of Streptococcus pneumonia was resistant to vancomycin and meropenam. The resistant rate of most tested antibiotics increased in different degree year by year, especially penicillin, erythromycin and clindamycin. The rate of PNSSP was only 19%( 19/99 )in 2006 ,but in 2009 the rate increased to 30%( 35/114 ). The susceptibility rate of erythromycin was 22% ( 28/125 )in 2000, but only 3% ( 3/114 )in 2009 ;and the susceptibility rate of clindamycin decreased from 40% ( 13/32 ) in 2004 to 4% (5/114) in 2009. Conclusions From 2000 to 2009, Streptococcus pneunoniae was more likely resistant to penicillin,erythromycin and clindamycin year by year, especially those isolates recovered from children. It was suggested that antibiotics should be chosen to use according to antimicrobial susceptibility test results.     

In vitro activity of cefditoren and other comparators against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis causing community-acquired respiratory tract infections in China

The aim of this study was to evaluate the in vitro activity of cefditoren and comparators against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis causing community-acquired respiratory tract infections (CARTIs). A total of 391 Streptococcus pneumoniae, 266 H. influenzae, and 76 M. catarrhalis were isolated from 10 centers located at 6 cities in China from January 2009 to May 2010. The microdilution method was used to determine minimum inhibitory concentrations (MICs). The pneumococci comprised 189 (48.3%) penicillin susceptible, 129 (33.0%) penicillin intermediate, and 73 (18.7%) penicillin resistant. Moxifloxacin and levofloxacin showed the highest activity (99.2% and 97.7%, respectively) against Streptococcus pneumoniae, followed by parenteral penicillin G (95.7%), cefditoren (83.1%) and amoxicillin-clavulanic acid (79.3%). Among the 266 H. influenzae isolates, 26 (9.8%) were ampicillin-resistant β-lactamase-producing strains and 24 (9.0%) were ampicillin-resistant β-lactamase-nonproducing strains (BLNAR). Most of antimicrobial agents demonstrated good activity (>97% susceptibility) against H. influenzae except ampicillin, cefuroxime, and cefaclor, which showed relatively lower activity (81.2%, 88.7%, and 88%, respectively). Cefditoren showed excellent activity with the lowest MIC(50) and MIC(90) (≤0.016/0.064 μg/mL) among all tested drugs, which is independent of β-lactamase production or ampicillin resistance. Cefditoren at a concentration of 0.5 μg/mL inhibited all BLNAR strains. Seventy of 76 isolates of M. catarrhalis produced β-lactamase. Cefditoren also showed excellent activity with MIC(90) of 0.064 μg/mL against β-lactamase-nonproducing strains and 0.5 μg/mL against β-lactamase-producing strains. In conclusion, the excellent intrinsic activity of cefditoren suggests that it may be a good choice for the treatment of CARTIs caused by Streptococcus pneumoniae, H. influenzae, and M. catarrhalis in China, while the activity should be closely monitored.     

Frequency of 1st- and 2nd-step topoisomerase mutations in Streptococcus pneumoniae following levofloxacin and moxifloxacin exposure

Seven Streptococcus pneumoniae isolates were exposed to inhibitory concentrations of levofloxacin and moxifloxacin in antibiotic-containing agar dilution plates. Colony counts were used to calculate the frequency of mutation. DNA was sequenced to detect mutations in the quinolone resistance-determining regions of the gyrA, gyrB, parC, and parE genes. The wild-type S. pneumoniae isolate developed a parC mutation after exposure to levofloxacin more frequently than it developed a gyrA mutation after exposure to moxifloxacin. The 1st-step gyrA mutant developed a 2nd-step gyrA-parC mutation more frequently after exposure to levofloxacin. Conversely, the transformation from a 1st-step parC mutant to a 2nd-step parC-gyrA mutant occurred more frequently following exposure to moxifloxacin. Our data suggest that the occurrence of a 2nd mutation will be contingent on the location of the 1st mutation and the preferential binding site of the fluoroquinolone that drives the transformation from 1st- to 2nd-step mutant.     

Quantitative detection of Streptococcus pneumoniae from sputum samples with real-time quantitative polymerase chain reaction for etiologic diagnosis of community-acquired pneumonia

We assessed the clinical usefulness of a real-time quantitative polymerase chain reaction (RQ-PCR) method applied on sputum samples to identify Streptococcus pneumoniae in 184 consecutive patients admitted to hospital with community-acquired pneumonia. Induced sputum samples were analyzed by culture and RQ-PCR. In total, 70/184 patients (38%) were diagnosed with S. pneumoniae. Cultures from blood and nasopharyngeal secretions were positive in 27/179 (15%) and 42/158 (27%) cases, respectively. Pneumococcal antigen was detected in 33/169 (20%) urine specimens. In sputum samples, culture was significantly positive in 19/128 (15%), whereas a significant concentration of DNA was found by RQ-PCR in 34/127 (27%) cases (P < 0.001). In 28/34 (82%) patients with RQ-PCR-positive sputum samples, S. pneumoniae was also detected with other methods. In the 34 RQ-PCR-positive sputum samples, 17 were negative by sputum culture, out of which 14 were obtained from patients treated with antibiotics prior to sampling. S. pneumoniae may be rapidly diagnosed by analyzing induced sputum samples by RQ-PCR and may be particularly valuable in patients in whom antibiotic therapy has been initiated.     

Macrolide resistance of Streptococcus pneumoniae isolated during long-term macrolide therapy: difference between erythromycin and clarithromycin

Longterm macrolide therapy (LTMT) has been employed as an effective therapy both for diffuse panbronchiolitis in Japan and for cystic fibrosis in European countries. However, effects on antibiotic susceptibility profiles of microorganisms, associated with such long-term administration of antibiotics, are of concern. We retrospectively identified 57 pneumococcal isolates, recovered from the same number of patients receiving either LTMT with 400mg of clarithromycin daily (CAM group; n = 31) or 600mg of erythromycin daily (EM group; n = 26) by reviewing the patients records at Nara Medical University. On analysis, we found that all isolates recovered from the CAM group and 25 of the 26 recovered from the EM group were resistant to EM, showing either an MLSB or an M phenotype. Interestingly, isolates exhibiting the M phenotype were much less frequent in the CAM group (2 of 31; 6.5%) than in the EM group (15 of 26; 57.7%). No increase in the rate of penicillin resistance was observed in either group. The macrolide resistance profiles of microorganisms may be influenced differently according to differences in the kind of macrolide antibiotics used.     

Type distribution of serogroup 6 Streptococcus pneumoniae and molecular epidemiology of newly identified serotypes 6C and 6D in China

The recently determined serotypes 6C and 6D Streptococcus pneumoniae, as well as subtypes 6B-I and 6B-II, were not reported in China. Among the 171 invasive isolates, 19 were identified as serogroup 6. There were equal distribution (42.1%) of 6B-I and 6B-II, 15.8% of 6A and lack of 6C and 6D. Among 1662 noninvasive isolates, 210 were identified as serogroup 6. The rates of types 6A, 6B-I, 6B-II, 6C, and 6D were 42.4%, 21.0%, 29.1%, 4.8%, and 2.9%, respectively. Subtype 6B-II was more resistant to antibiotics than others. The main sequence types (STs) of serotype 6C and 6D isolates were ST2912 and ST982, respectively. These results suggested that all recognized types of serogroup 6 can be found in China and that subtype 6B-II was more drug resistant. The epidemic STs of serotype 6C and 6D did not show genetic association with the STs spreading in other countries.     

Host and microbiologic factors associated with mortality in Taiwanese children with invasive pneumococcal diseases, 2001 to 2006

We concurrently evaluated host- and organism-related factors in determining the outcomes of 160 invasive pneumococcal diseases episodes in 158 Taiwanese children during 2001 and 2006. Most (138/160, 86.2%) episodes occurred at age less than 60 months, and an underlying condition was present in 35 (22.2%) cases. Common disease syndromes included complicated pneumonia (29.4%), uncomplicated pneumonia (29.4%), occult bacteremia (17.5%), and meningitis (14.4%). Mortality (13/160, 8.1%) was associated with age less than 24 months, underlying conditions, meningitis, cytopenia, intensive care, and penicillin MIC ≥2 μg/mL in univariate analysis. Pneumococcal serotypes, genotypes, origin of infections, and discordant therapy did not influence the outcome. Multivariate analysis determined the presence of underlying conditions (adjusted odds ratio [OR], 30.5; 95% confidence interval [CI], 4.8–193.1) and penicillin MIC ≥2 μg/mL (adjusted OR, 8.1; 95% CI, 1.4–47.3), which are the independent predictors for fatality. This finding highlighted the importance of immunization of disadvantaged children, targeting drug-resistant pneumococci.     

Streptococcus pneumoniae in the potential effects of new vaccines on the pattern of antibiotic drug usage in pediatrics

Background:Streptococcus pneumoniae is a common cause of respiratory tract infections and acute otitis media. The main reservoir of S pneumoniae is the nasopharynx. From there, it can spread to cause disease in various foci.Objective: This article reviews studies on the use of vaccines to prevent the spread of S pneumoniae, particularly antibiotic-resistant serotypes.Methods: Published data were identified using a PubMed search of the literature published from 1995 to the present in all languages, using the search terms S pneumoniae, vaccines, and antibiotic resistance. Relevant conference presentations were also included.Results: Most children are colonized during the first years of life. Antibiotic resistance to S pneumoniae is prevalent and increasing, which affects clinical outcomes and antibiotic use. In clinical studies, conjugate pneumococcal vaccines reduced the rates of carriage of those pneumococcal serotypes included in the vaccines. They also appeared to increase the rates of carriage of pneumococcal serotypes not related antigenically to those in the vaccines (a replacement phenomenon). Antibiotic resistance is most prevalent among serotypes included in the conjugate vaccines. Studies have also shown that conjugate pneumococcal vaccines reduced the carriage and spread of antibiotic-resistant S pneumoniae, including among younger siblings of toddlers in day care. The reduction in carriage of antibiotic-resistant S pneumoniae was associated with a reduction in the number of respiratory infections and use of antibiotics in day care centers.Conclusions: Preliminary studies of conjugate pneumococcal vaccines suggest that they may help prevent the spread of antibiotic-resistant serotypes and reduce the need for antibiotic therapy for S pneumoniae infections.     

A real-time polymerase chain reaction for the detection of Streptococcus pneumoniae in blood using a mouse model: a potential new "gold standard"

Better diagnostics for pneumococcal disease are urgently needed. In a murine model, real-time polymerase chain reaction was superior to conventional culture in detecting pneumococcus in blood, particularly in early disease and after antibiotic administration, and could distinguish between commensalism and infection.     

Interpretive categorical accuracy of fluoroquinolone reference broth microdilution MIC results when testing Streptococcus pneumoniae: selection of a surrogate testing agent

The categorical agreement among MIC results for the fluoroquinolones tested (levofloxacin, moxifloxacin, gatifloxacin and gemifloxacin) was high (99.16-99.85%), and error rates were nil or very low when 1 compound was used as a surrogate for predicting susceptibility (not resistance) to another agent in the class. No error was observed when levofloxacin was selected as the group surrogate for pneumococcal testing.     

Pneumococcal carriage in children attending a hospital outpatient clinic in the era of pneumococcal conjugate vaccines in Barcelona

Between April 2004 and March 2006 an oropharyngeal swab was obtained from 502 asymptomatic children, aged 6 months to 6 years, at a tertiary children's hospital outpatient department to assess the pneumococcal colonisation rate, risk factors, serotype distribution and antimicrobial susceptibility. Only 126 (25.3%) children had received ≥ 1 dose of PCV7. The pneumococcal carriage rate was 23.5%. Carrier rates were significantly higher in children aged ≥ 24 months and children attending daycare center. Thirty six (31.0%) of the isolates were contained in PCV7, 39 (33.6%) in PCV10 and 62 (53.4%) in PCV13. Forty-four strains (37.9%) were resistant to penicillin. Vaccine serotype (VT) strains were more likely to be penicillin-nonsusceptible S. pneumoniae than non-PCV7 serotype (NVT) strains (66.7% vs. 21.6%; P < 0.001). In our pediatric population, NVT were predominant among pneumococcal carriers whereas antibiotic resistance was significantly associated with VT. PCV13 can substantially increase the serotype coverage of S.pneumoniae in healthy carriers.