Molecular characterization of Latin American invasive Streptococcus pneumoniae serotype 19A isolates

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide, especially among children and the elderly. S. pneumoniae serotype 19A has emerged as a major cause of invasive disease in many countries, regardless of whether pneumococcal conjugate vaccines are used. The aim of this study was molecular characterization of invasive S. pneumoniae serotype 19A isolates recovered between 2000 and 2015 from 13 National Laboratories through the laboratory-based surveillance of invasive S. pneumoniae program SIREVA II in Latin American countries. The isolates were submitted with antimicrobial susceptibility tests and were genotyped by a combination of pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Of the 185 isolates assayed, notable rates of resistance to penicillin (MIC ≥ 0.125 µg/mL; 68.6%), tetracycline (63.7%), trimethoprim-sulfamethoxazole (63.2%), and erythromycin (43.2%) were observed, while 44.3% of isolates were multidrug resistant. The most frequently observed sequence types (ST) were ST320 (32.4%), ST199 (14.1%), ST172 (10.8%) and ST5204 (7.1%). The distribution of STs indicated regional differences in the epidemiology of the clonal groups. The present study showed a diverse genetic background of the pneumococcal population in Latin American countries. Continuous surveillance of the pneumococcal serotype 19A population in the region will be necessary to obtain information about geographical differences and changes in the spread and the establishment of particular clones.     

Spread of Streptococcus pneumoniae Serotype 8-ST63 Multidrug-Resistant Recombinant Clone,Spain

Since 2004, a total of 131 isolates of Streptococcus pneumoniae multidrug-resistant invasive serotype 8 have been detected in Spain. These isolates showed resistance to erythromycin, clindamycin, tetracycline, and ciprofloxacin. All isolates were obtained from adult patients and shared a common genotype (sequence type [ST]63; penicillin-binding protein 1a [pbp1a], pbp2b, and pbp2x gene profiles; ermB and tetM genes; and a ParC-S79F change). Sixty-eight isolates that required a ciprofloxacin MIC ≥16 μg/mL had additional gyrA gene changes. Serotype 8-ST63 pbp2x sequences were identical with those of antimicrobial drug–susceptible serotype 8-ST53 isolates. Serotype 8-ST63 pbp2b sequences were identical with those of the multidrug-resistant Sweden 15A-ST63 clone. Recombination between the capsular locus and flanking regions of an ST53 isolate (donor) and an ST63 pneumococcus (recipient) generated the novel 15A-ST63 clone. One recombination point was upstream of pbp2x and another was within pbp1a. A serotype 8-ST63 clone was identified as a cause of invasive disease in Spain.     

The changing phenotypes and genotypes of invasive pneumococcal isolates from children in Shenzhen during 2013–2017

BackgroundThe phenotypes and genotypes of Streptococcus pneumoniae isolated from invasive pneumococcal diseases (IPDs) were changing all the time. To monitor these changes of phenotypes and genotypes of S. pneumoniae isolates from children, we examined antibiotic susceptibility, serotype distribution and sequence types (STs) of S. pneumoniae, which were isolated before the 13-valent pneumococcal conjugate vaccine (PCV13) introduced into China.MethodsStrains were isolated from children less than 14 years old between January 2013 and May 2017 from Shenzhen Children’s Hospital. Serotypes, antibiotic resistance, and genotypes of these isolates were determined using capsular swelling, E-test, and multi-locus sequence typing, respectively.ResultsA total of 94 S. pneumoniae strains were isolated, which belonged to 15 serotypes. The five most prevalent serotypes were 19F (25.5%), 19A (19%), 14 (17%), 23F (7.5%), and 6B (9.6%). We found 42 STs for these isolates. The most abundant STs were ST271 (24.4%), ST876 (17%), and ST320 (10.6%), mainly related to 19F, 14, and 19A, respectively. The potential coverage of PCV13 was 87.2%. Among non-meningitis isolates, the resistance rates to penicillin and ceftriaxone were 0% and 2%. However, the meningitis isolates showed high resistance to penicillin (80%) and ceftriaxone (20%). Most of these isolates (95.7%) were resistant to erythromycin, and 66 (70.2%) strains carried the ermB gene and 24 (25.5%) strains carried both the ermB and mefA/E genes. Serotype 19A showed the highest mean minimum inhibitory concentration (MIC) for penicillin (MIC = 1.486) than the other serotypes, but no significant difference in penicillin MIC among the three main STs (ST271, ST320, and ST876).ConclusionsThe phenotypes and genotypes of invasive pneumococcal isolates from Shenzhen Children’s Hospital have changed with the passage of time. Compared with PCV7, PCV13 can more effectively protect Chinese children from IPDs. To some extent, these changes are possibly related to the usage of antibiotics and vaccines.     

Clonal and clinical profile of Streptococcus pneumoniae serotype 19A causing pediatric invasive infections: a 2-year (2007-2009) laboratory-based surveillance in Madrid

Studies of clonality and clinical profile of serotype 19A invasive pneumococcal disease in children (IPD-19A) are worthy after PCV7 introduction. A prospective, hospital-based surveillance of IPD-19A, culture and/or PCR confirmed, was performed in 2007-2009 in Madrid (all 22 hospitals with pediatric departments). Sixty-two cases were found: 90.3% in children <5 years, 87.1% in <36 months, and 74.2% in ≤18 months. Clinical presentations: meningitis (22.6%), primary bacteremia (19.4%), secondary bacteremia to otic foci (SBOF; 17.7%), bacteremic pneumonia (17.7%), pediatric parapneumonic empyema (PPE; 17.7%) and others (4.8%). Presentations by age: meningitis (35.7%), SBOF (28.6%) and primary bacteremia (21.4%) in children <12 months, bacteremic pneumonia, PPE and primary bacteremia (26.3% each) in 12-23 months, and bacteremic pneumonia (33.3%) and PPE (26.6%) in ≥24 months. Sequence types ST276 and ST320 represented 83.0% isolates, all oral-penicillin/erythromycin non-susceptible. In nonmeningeal isolates, non-susceptibility to parenteral penicillin/cefotaxime was 0%/17.6% (ST276) and 93.8%/75.0% (ST320). Non-susceptibility in ST276 and ST320, prevalence of these STs among 19A isolates, and serotype 19A prevalence among IPDs, indicate the importance of 19A inclusion in PCV13 for IPD-19A prevention and for reducing 19A nasopharyngeal carriage, thus preventing 19A otitis (one-third of 19A bacteremia in this study were from otic origin).     

Dynamic of pneumococcal nasopharyngeal carriage in children with acute otitis media following PCV7 introduction in France

To determine whether the use of seven valent pneumococcal conjugate vaccine (PCV7) caused a shift in the Streptococcus pneumoniae serotypes distribution and whether it modified the resistance to antibiotics, 3291 nasopharyngeal swabs were obtained between 2001 and 2006, from children aged 6–24 months with acute otitis media. Following the implementation of PCV7, we observed a slight reduction in the overall pneumococcal carriage, a marked decrease of vaccine serotypes, an increase in non-vaccine serotypes carriage and a reduction in the carriage of penicillin non-susceptible strains. Most of the serotype 19A replacement was related to the clonal expansion of ST276 which was found to be the predominant ST among penicillin non-susceptible isolates.     

Pneumococcal serotype distribution and antimicrobial resistance in Chinese children hospitalized for pneumonia

A prospective study was performed to determine serotype distribution and antimicrobial resistance in Streptococcus pneumoniae (S. pneumoniae) from Chinese children <5 years old meeting pneumonia criteria. A total of 3865 children were enrolled and 338 S. pneumoniae isolates were obtained. The most frequent serotypes were 19F (55.6%), 19A (13.9%), 23F (10.1%), 6B (4.7%), and 14 (3.6%). The 7-, 10- and 13-valent conjugate vaccines, respectively, covered 76.3%, 76.9%, and 92.3% of isolates. Out of the isolates, six (1.8%) were penicillin resistant. All except 1 of the isolates were resistant to erythromycin. Serotype 19A showed the highest drug resistance. The use of PCV7 has the potential to prevent a substantial number of pneumococcal infections. However, PCV13 is likely to prevent more episodes of pneumococcal disease in China because of the high rates of 19A.     

Characteristics of Streptococcus pneumoniae serotype 19A isolates from children in the pre and post Conjugate Vaccine Era. Single center experience 1986–2015

BackgroundThe present study assessed the prevalence and characteristics of S. pneumoniae serotype 19A isolates from children with pneumococcal disease (PD), before and since introduction of pneumococcal conjugate vaccines (PCVs) in Greece.MethodsS. pneumoniae isolates collected at one large pediatric hospital between 1986 and 2015 were serotyped by the Quellung reaction and MICs determined by Etest. Alterations of pbp genes and the presence of mefA, mefE, ermB genes were detected by polymerase chain reaction. Genotypes were assessed by multilocus sequence typing (MLST).ResultsAmong 1875 isolates, 210 (11.2%) belonged to serotype 19A. The prevalence of PD caused by serotype 19A increased from 4.6% in the pre-PCV7 years (1986–2005) to 19.6% in the post-PCV7 years (2006–2010), peaking at 27% in 2009 (p < 0.001, 95% CI; 2.0, 18.2) with a significant upward trend (p = 0.04, 95% CI; 1.02, 12.66). Following the introduction of PCV13 in 2010, the rate decreased from 22% in 2011 to 11.4% in 2015 (p = 0.08, 95% CI; 0.92, 5.1) with a downward trend of borderline significance (p = 0.05, 95% CI; −6.8, 0.04). The multidrug resistant (MDR) serotype 19A isolates increased from 10.6% in 1986–2005 to 21.2% in 2006–2010 and to 71.8% in 2011–2015 (P < 0.001). Alterations in pbp genes were detected in all penicillin non-susceptible isolates. Of 110 erythromycin resistant isolates, 21 contained the mefE gene, 36 the ermB and 53 both the mefE and ermB genes. MLST analysis of 142 isolates revealed four dominant clonal complexes (CC); CC320, CC172, CC276 and CC199. The majority of CC320 and CC276 isolates displayed MDR phenotypes.ConclusionPD caused by serotype 19A increased significantly after the introduction of PCV7 followed by a decline after PCV13 use. The vast majority of persisting 19A isolates was MDR. Surveillance studies are necessary to monitor the changes in the pneumococcal population.     

Phenotypic and molecular characterization of Streptococcus pneumoniae in pre-conjugate vaccine era: A Chinese hospital-based retrospective study

BackgroundStreptococcus pneumoniae (S. pneumoniae) is an important pathogen in causing global morbidity and mortality among children. This study aimed to determine phenotypic and molecular characteristics of S. pneumoniae causing infections in children under five years in China.MethodsA hospital-based retrospective study was conducted. All 537 S. pneumoniae isolates were tested for antimicrobial susceptibility by E-test method, molecular characteristics including resistance genes, virulence genes and serotypes by multiplex polymerase chain reaction (PCR) method, and sequence types (STs) by sequencing seven housekeeping genes. Minimum spanning tree and correspondence analysis were used to reveal the potential relationship between serotypes and STs.ResultsMost of S. pneumoniae isolates were resistant to erythromycin (93.9%) and tetracycline (86.4%), with the predominant resistance genes being erm(B) (92.6%) and tet(M) (95.5%). The prevalent serotypes were 19F, 6B, 19A, 23F and 14, the coverage rate of PCV13 was high in 85.8%, and the predominant STs were ST271, ST320, ST3173, ST81 and ST876. A significant correlation existed between STs and serotypes, with ST271/19F and ST320/19A as the most prevalent clones. Notably, ST271/19F and ST320/19A isolates were associated with resistance to specific antibiotics and carrying of mef(A/E), rlrA and sipA genes.ConclusionsOur findings suggest the introduction of PCV13 vaccine to Chinese children, and underscore the value of monitoring multiple characteristics to detect new epidemiologic trends and provide implications for the formulation of multivalent pneumococcal vaccines.     

Changes in Fluoroquinolone-Resistant Streptococcus pneumonia after 7-Valent Conjugate Vaccination, Spain

Among 4,215 Streptococcus pneumoniae isolates obtained in Spain during 2006, 98 (2.3%) were ciprofloxacin resistant (3.6% from adults and 0.14% from children). In comparison with findings from a 2002 study, global resistance remained stable. Low-level resistance (30 isolates with MIC 4–8 μg/mL) was caused by a reserpine-sensitive efflux phenotype (n = 4) or single topoisomerase IV (parC [n = 24] or parE [n = 1]) changes. One isolate did not show reserpine-sensitive efflux or mutations. High-level resistance (68 isolates with MIC ≥16 μg/mL) was caused by changes in gyrase (gyrA) and parC or parE. New changes in parC (S80P) and gyrA (S81V, E85G) were shown to be involved in resistance by genetic transformation. Although 49 genotypes were observed, clones Spain^9V-ST156 and Sweden^15A-ST63 accounted for 34.7% of drug-resistant isolates. In comparison with findings from the 2002 study, clones Spain¹⁴-ST17, Spain^23F-ST81, and ST88^19F decreased and 4 new genotypes (ST97^10A, ST570¹⁶, ST433²², and ST717³³) appeared in 2006.     

Serotype distribution and antibiotic resistance of 140 pneumococcal isolates from pediatric patients with upper respiratory infections in Beijing, 2010

In the present study, the serotype distribution and antibiotic resistance of S. pneumoniae from pediatric patients with upper respiratory infections in Beijing, 2010 were described. 140 pneumococcal isolates were obtained, and the prevailing five serotypes were 19F (18.6%), 23F (9.3%), 14 (9.3%), 15 (9.3%), and 6A (7.1%). The vaccine coverage of PCV7, PCV10, and PCV13 were 43.6%, 43.6%, and 60.0%, respectively. According to the CLSI 2010 criteria, 99.3% of the S. pneumoniae isolates were susceptible to penicillin. The resistance rates to erythromycin and azithromycin were 96.4% and 97.1%, respectively. Meanwhile, 64.3% (90/140) of all pneumococcal isolates were multidrug-resistant S. pneumoniae (MDRSP). PCV13 covered 68.9% (62/90) of MDRSP strains, whereas it was 47.8% (43/90) for PCV7. ErmB was the dominant macrolide-resistance gene, whereas 30.4% pneumococcal isolates expressed both ermB and mefA. No isolate expressed ermTR. The potential coverage of PCV13 is higher than PCV7 and PCV10 because high rates of serotypes 6A and 19A, and the conjugate vaccines could prevent the spread of MDRSP. S. pneumoniae is still sensitive to penicillin. The resistance rate of S. pneumoniae to macrolides is high and ermB is the dominant macrolide-resistance gene in China, so continued surveillance of the antimicrobial susceptibility of S. pneumoniae may be necessary.     

Whole genome characterization of Streptococcus pneumoniae from respiratory and blood cultures collected from Canadian hospitals before and after PCV-13 implementation in Canada: Focus on serotypes 22F and 33F from CANWARD 2007–2018

The population of pneumococci circulating in Canada is constantly shifting under the pressures of antimicrobial and conjugate vaccine use. A new 15-valent pneumococcal conjugate vaccine (PCV), containing PCV-13 serotypes plus additional serotypes 22F and 33F, is currently undergoing clinical trials. The purpose of this study was to utilize whole genome sequencing to characterize invasive and respiratory Streptococcus pneumoniae isolates collected from Canadian hospitals pre- (2007–2011) and post-PCV-13 implementation (2012–2018) in Canada, particularly serotypes 22F and 33F. Isolates were obtained from the CANWARD 2007 to 2018 study. Overall, 597 S. pneumoniae isolates were sequenced using the Illumina MiSeq platform: 180 (101 respiratory, 79 blood) isolates of serotype 22F, 74 (41 respiratory, 33 blood) isolates of serotype 33F and 343 isolates randomly selected to broadly encompass pneumococci in Canada. Genomes were clustered using PopPUNK v2.0.2 and assigned to a Global Pneumococcal Sequencing Cluster (GPSC) and MLST sequence type (ST), and visualized using Cytoscape v3.8.0. Acquired resistance genes were identified using ResFinder 2.1, and genes with chromosomal mutations conferring resistance were extracted and compared to standard reference genome R6. PopPUNK clustering suggests that a clone of S. pneumoniae serotype 22F/ST433/GPSC19 demonstrating mefA-mediated macrolide resistance is emerging in Canada post-PCV-13 introduction, collected from both invasive and respiratory sources. Similarly, there is evidence to support a post-PCV-13 shift towards macrolide- and trimethoprim/sulfamethoxazole-resistant serotype 33F/ST100/GPSC3, including a cluster associated with invasive isolates. While some lineages containing vaccine serotypes were predominantly identified pre-PCV-13 implementation (serotype 5/GPSC8, serotype 7F/GPSC15), others (serotype 19A/GPSC1 and 4, serotype 3/GPSC12) continue to maintain a significant presence over time despite inclusion in PCV-13. Further genomic surveillance is necessary to determine additional trends over time in these upcoming vaccine serotypes, as well as the overall pneumococcal population in Canada.     

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.     

Changes in the incidence of Streptococcus pneumoniae bacteremia and its serotypes over 10 years in one hospital in South Korea

Here, we examined the distribution of pneumococcal serotypes and the antibiotic susceptibility of Streptococcus pneumoniae in clinical blood isolates. The serotypes of 91 S. pneumoniae blood isolates, collected from January 2003 to March 2014, were identified by multiplex PCR and sequencing. The most common serotypes were 19F, 19A, 3, 4, and 14, accounting for 53.8% of the total. The serotype coverage rates of pneumococcal conjugated vaccine (PCV) 7, PCV10, and PCV13 were different during three test periods: 38.7%, 70.9%, and 93.5% in period I (2003–2005), 46.8%, 50.0%, and 75.0% in period II (2006–2008), and 28.5%, 32.1%, and 64.2% in period III (2009–2014), respectively. By contrast, the number of non-PCV13 serotypes increased from 6.4% in period I to 25% and 35.7% in periods II and III, respectively. The susceptibility of non-PCV13 serotypes to antimicrobial agents (penicillin, erythromycin, cefotaxime, and meropenem) was higher than that of PCV serotypes. In particular, non-PCV13 serotypes showed 100% and 95% susceptibility to penicillin and cefotaxime, respectively. Serotypes 19A and 19F showed high prevalence (79.1%) among 24 multi-drug resistant (MDR) isolates. Notably, all serotype 19A isolates were MDR. From January 2003 to March 2014, the proportion of non-PCV13 serotype pneumococci in blood isolates increased whereas the coverage rate of PCV13 decreased. Effective pneumococcal vaccines are required to protect against MDR serotype 19A isolates and the increasing number of non-PCV13 serotypes.     

One cross-sectional investigation revealed that non-vaccine serotypes of Streptococcus pneumoniae could be identified more frequently in elderly Chinese people

ObjectiveTo analyze the serotype distribution and drug resistance of Streptococcus pneumoniae isolated from hospitalized patients of all ages in Zhongjiang county, Sichuan province, where the young children have just begun to vaccinate the PCV13 in private sector.MethodsSerotypes were determined for 387 isolates of S. pneumoniae by Quellung reaction. Antibiotic susceptibility was tested with the E-test or disc diffusion method.ResultsThe most common serotypes were type 19F and confirmed for 88 isolates (22.7%), followed by 19A (15.0%), 6B (7.8%), 16F (7.8%), 23F (7.0%) and 15A (4.4%). The coverage rates of PCV13 and PPSV23 were 63.3% and 65.1%. With the increase of age, the proportion of PCV13 types decreased significantly, from 71.3% (<2 years old) to 41.9% (≥60 years old). The intermediate rate and resistance rate of the isolates to oral penicillin were 48.6% and 45.2%, respectively. The resistance rate of erythromycin was high (94.4%). The PCV13 isolates was more resistant to penicillin than the non-PCV13 ones.ConclusionThe PCV13 coverage rate in pediatric isolates was higher than those in adult isolates. The adults, especially the elderly, may be the reservoir of non-PCV13 types. It is necessary to investigate the serotype distribution of S. pneumoniae based on all age population to assess potential epidemics of non-vaccine serotype associated with PCVs administration.     

New Sequence Types and Antimicrobial Drug–Resistant Strains of Streptococcus suis in Diseased Pigs,Italy, 2017–2019

Streptococcus suis is a pathogen associated with severe diseases in pigs and humans. Human infections have a zoonotic origin in pigs. To assess circulating strains, we characterized the serotypes, sequence types, and antimicrobial susceptibility of 78 S. suis isolates from diseased farmed pigs in Italy during 2017–2019. Almost 60% of infections were caused by serotypes 1/2 and 9. All but 1 of the serotype 2 and 1/2 isolates were confined to a single cluster, and serotype 9 isolates were distributed along the phylogenetic tree. Besides sequence type (ST) 1, the serotype 2 cluster included ST7, which caused severe human infections in China in 1998 and 2005. A large proportion of serotype 9 isolates, assigned to ST123, were resistant to penicillin. The emergence of this clone threatens the successful treatment of S. suis infection. Characterizing S. suis isolates from pigs will promote earlier detection of emerging clones.     

Clonal replacement among 19A Streptococcus pneumoniae in Massachusetts, prior to 13 valent conjugate vaccination

As part of an ongoing study of the response of the Streptococcus pneumoniae population to conjugate vaccination, we applied multi-locus sequence typing (MLST) to 291 isolates sampled from nasopharyngeal carriage in Massachusetts children. We found 94 distinct sequence types (STs), including 19 that had not been previously recorded, and a xpt allele containing a large insertion. Comparison with a similar sample collected in 2007 revealed no significant overall difference in the ST composition (p = 0.51) suggesting that the population has reached a new equilibrium following the introduction of 7 valent vaccination in 2000. Within serotypes, a large and statistically significant increase (p = 0.014 Fisher's Exact test) was noted in the prevalence of the major multiresistant clone ST 320, which is apparently outcompeting ST 199 among serotype 19A strains. This sample will be used as a baseline to study the future evolution of the pneumococcal population in Massachusetts following introduction of vaccines with higher valency.     

Streptococcus pneumoniae serotypes isolated from the middle ear fluid of Costa Rican children following introduction of the heptavalent pneumococcal conjugate vaccine into a limited population

Background

The heptavalent pneumococcal conjugate vaccine (PCV-7) was introduced in high risk children and into the private market in Costa Rica in 2004 (<5% annual birth cohort). The aim of this study was to compare the Streptococcus pneumoniae serotype (ST) distribution, antibiotic resistance patterns and potential coverage before and after partial introduction of PCV-7.

Methods

A comparison between the S. pneumoniae isolates obtained and serotyped from the middle ear fluid (MEF) of Costa Rican children with otitis media between years 1999 and 2003 (before PCV-7 usage) and those isolates obtained from 2004 to 2008.

Results

A total of 145 and 218 MEF S. pneumoniae were serotyped between years 1999 and 2003 and 2004 and 2008, respectively. Considering a 19F outbreak observed between years 1999 and 2003, the following statistically significant changes in serotype distribution were detected between1999 and 2003 and 2004 and 2008: ST 3: 4.8–12.8% (P = 0.01); ST 11A: 0–4.1% (P = 0.01); ST 14: 3.5–21.1% (P < 0.001) and ST 19F: 52.4–18.3% (P < 0.05). Comparison of the two study periods demonstrated that during 2004 and 2008 a statistically significant decrease in penicillin non-susceptible serotypes (36.2–20.4% [P = 0.003]) and a statistically significant increase in trimethoprim-sulfametoxazole resistant serotypes (54.9–68.5%, respectively [P = 0.03]) was observed. Potential pneumococcal vaccines coverage between 1999 and 2003 and between 2004 and 2008 were: for PCV-7: 77.2–60.5%, respectively (P = 0.001); for the 10-valent conjugated vaccine (PCV-10): 78.6–61.4%, respectively (P = 0.0008) and for the 13-valent conjugated vaccine (PCV-13): 84.8–79.3%, respectively (P = 0.2).

Conclusions

Changes in the serotype distribution and antimicrobial susceptibility of MEF S. pneumoniae have been observed in Costa Rican children with OM. Because of the limited use of PCV-7 during the study period, these changes probably cannot be attributed to PCV-7 use. Between 2004 and 2008, PCV-13 offered the highest potential vaccine coverage.     

Prevalence of antimicrobial resistant Streptococcus pneumoniae serotype 11A isolates in Korea,during 2004–2013, due to the increase of multidrug-resistant clone,CC166

Since the introduction of the pneumococcal conjugate vaccine (PCV7) in Korea in 2003, the proportion of non-vaccine serotypes has increased. Among non-vaccine serotypes, serotype 11A is highly prevalent in Korea. We investigated the prevalence and characteristics of Streptococcus pneumoniae serotype 11A isolates in a Korean tertiary-care hospital, during 2004–2013. A total of 1579 non-duplicate clinical S. pneumoniae isolates, collected from 2004 to 2013, were included in this study. Serotype was 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. We identified 90 serotype 11A isolates (5.7%). During this period, the proportion of serotype 11A has increased from 3.2% up to 13.2% (in 2012). Among the serotype 11A isolates, two main clonal complexes (CCs), CC166 and CC99, were identified. The increase of serotype 11A was mainly due to the increase of CC166 isolates, which have high antimicrobial resistance rates. In addition, we identified that 14 isolates, belonging to ST8279, ST9875, and ST3598 of CC166, were non-susceptible to all antimicrobial agents tested in this study. We identified the increase of S. pneumoniae serotype 11A in Korea, which mainly due to the expansion of a resistant clonal group, CC166.     

Increase in Pilus Islet 2�Cencoded Pili among Streptococcus pneumoniae Isolates, Atlanta, Georgia, USA

To define the prevalence of pilus islet 2 (PI-2)–encoded pili in Streptococcus pneumoniae in a geographically defined area, we examined 590 S. pneumoniae isolates from population-based surveillance of invasive pneumococcal disease in Atlanta, Georgia, USA, 1994–2006. In 2006, PI-2 was present in 21% of all invasive isolates, including serotypes 1 (100%), 7F (89%), 11A (21%), 19A (40%), and 19F (75%). Only serotype 19F is included in the 7-valent pneumococcal conjugate vaccine that is in use worldwide. In 1999, PI-2-containing isolates were of the same serotypes but accounted for only 3.6% of all invasive isolates. The increase of PI-2 in 2006 resulted predominantly from the emergence of serotype 19A isolates of sequence type 320 and the expansion of serotype 7F isolates. The increase in PI-2-containing isolates and the finding that isolates of all identified serotypes expressed highly conserved PI-2 pili supports their potential as a vaccine candidate.     

Capacity of serotype 19A and 15B/C Streptococcus pneumoniae isolates for experimental otitis media: Implications for the conjugate vaccine

Non-vaccine Streptococcus pneumoniae serotypes are increasingly associated with disease. We evaluated isolates of the same sequence type (ST199) but different serotypes (15B/C, 19A) for growth in vitro, and pathogenic potential in a chinchilla otitis media model. We also developed a quantitative PCR (qPCR) assay to quantitatively assess each isolate, circumventing the need for selectable markers. In vitro studies showed faster growth of serotype 19A over 15B/C. Both were equally capable of colonization and middle ear infection in this model. Serotype 19A is included in new conjugate vaccine formulations while serotype 15B/C is not. Non-capsular vaccine targets will be important in disease prevention efforts.