Serotype 19F Research Articles

Prophage Excision in Streptococcus pneumoniae Serotype 19A ST320 Promote Colonization: Insight Into Its Evolution From the Ancestral Clone Taiwan 19F-14 (ST236).

Streptococcus pneumoniae 19A ST320, a multidrug-resistant strain with high disease severity that notoriously spread before the use of expanded pneumococcal conjugate vaccines, was derived from a capsular switching event between an international strain Taiwan 19F-14 (ST236) and a serotype 19A strain. However, the molecular mechanisms underlying the adaptive evolution of 19F ST236 to 19A ST320 are unknown. In this study, we compared 19A ST320 to its ancestral clone, 19F ST236, in terms of adherence to respiratory epithelial cells, whole transcriptome, and ability to colonize a young mouse model. Serotype 19A ST320 showed five-fold higher adherence to A549 cells than serotype 19F ST236. High-throughput mRNA sequencing identified a prophage region located between dnaN and ychF in both strains; however, the genes in this region were expressed at significantly higher levels in 19A ST320 than in 19F ST236. Analysis by polymerase chain reaction (PCR) showed that the prophage is able to spontaneously excise from the chromosome and form a circular episome in 19A ST320, but not in 19F ST236. Deletion of the integrase in the prophage of 19A ST320 decreased spontaneous excision and cell adherence, which were restored by complementation. Competition experiments in mice showed that the integrase mutant was six-fold less competitive than the 19A ST320 parent (competitive index [CI]: 0.16; p = 0.02). The 19A ST320 prophage-deleted strain did not change cell adherence capacity, whereas prophage integration strains (integrase mutant and 19F) had decreased expression of the down-stream ychF gene compared to that of 19A ST320. Further deletion of ychF significantly reduced cell adherence. In conclusions, these findings suggest that spontaneous prophage induction confers a competitive advantage to virulent pneumococci.

Population genomics of pneumococcal carriage in Massachusetts children following introduction of PCV-13.

The 13-valent pneumococcal conjugate vaccine (PCV-13) was introduced in the United States in 2010. Using a large paediatric carriage sample collected from shortly after the introduction of PCV-7 to several years after the introduction of PCV-13, we investigate alterations in the composition of the pneumococcal population following the introduction of PCV-13, evaluating the extent to which the post-vaccination non-vaccine type (NVT) population mirrors that from prior to vaccine introduction and the effect of PCV-13 on vaccine type lineages. Draft genome assemblies from 736 newly sequenced and 616 previously published pneumococcal carriage isolates from children in Massachusetts between 2001 and 2014 were analysed. Isolates were classified into one of 22 sequence clusters (SCs) on the basis of their core genome sequence. We calculated the SC diversity for each sampling period as the probability that any two randomly drawn isolates from that period belong to different SCs. The sampling period immediately after the introduction of PCV-13 (2011) was found to have higher diversity than preceding (2007) or subsequent (2014) sampling periods {Simpson’s D 2007: 0.915 [95 % confidence interval (CI) 0.901, 0.929]; 2011: 0.935 [0.927, 0.942]; 2014 : 0.912 [0.901, 0.923]}. Amongst NVT isolates, we found the distribution of SCs in 2011 to be significantly different from that in 2007 or 2014 (Fisher’s exact test P=0.018, 0.0078), but did not find a difference comparing 2007 to 2014 (Fisher’s exact test P=0.24), indicating greater similarity between samples separated by a longer time period than between samples from closer time periods. We also found changes in the accessory gene content of the NVT population between 2007 and 2011 to have been reduced by 2014. Amongst the new serotypes targeted by PCV-13, four were present in our sample. The proportion of our sample composed of PCV-13-only vaccine serotypes 19A, 6C and 7F decreased between 2007 and 2014, but no such reduction was seen for serotype 3. We did, however, observe differences in the genetic composition of the pre- and post-PCV-13 serotype 3 population. Our isolates were collected during discrete sampling periods from a small geographical area, which may limit the generalizability of our findings. Pneumococcal diversity increased immediately following the introduction of PCV-13, but subsequently returned to pre-vaccination levels. This is reflected in the distribution of NVT lineages, and, to a lesser extent, their accessory gene frequencies. As such, there may be a period during which the population is particularly disrupted by vaccination before returning to a more stable distribution. The persistence and shifting genetic composition of serotype 3 is a concern and warrants further investigation.

Pneumococcal Colonization in Healthy Adult Research Participants in the Conjugate Vaccine Era, United Kingdom, 2010-2017.

Pneumococcal colonization is rarely studied in adults, except as part of family surveys. We report the outcomes of colonization screening in healthy adults (all were nonsmokers without major comorbidities or contact with children aged <5 years) who had volunteered to take part in clinical research. Using nasal wash culture, we detected colonization in 6.5% of volunteers (52 of 795). Serotype 3 was the commonest serotype (10 of 52 isolates). The majority of the remaining serotypes (35 of 52 isolates) were nonvaccine serotypes, but we also identified persistent circulation of serotypes 19A and 19F. Resistance to at least 1 of 6 antibiotics tested was found in 8 of 52 isolates.

Safety and immunogenicity of 15-valent pneumococcal conjugate vaccine (PCV-15) compared to PCV-13 in healthy older adults

ABSTRACTBackground: Pneumococcal disease remains a public health priority in adults. Safety and immunogenicity of 2 different formulations of 15-valent pneumococcal conjugate vaccine (PCV15) containing 13 serotypes included in 13-valent pneumococcal conjugate vaccine (PCV13) plus 2 additional serotypes (22F and 33F) were evaluated in adults ≥ 50 years (V114-006; NCT02547649).Methods: A total of 690 subjects (230/arm) received a single dose of either PCV15 Formulation A, PCV15 Formulation B, or PCV13 and were followed for safety for 14 days postvaccination. Serotype-specific opsonophagocytic activity (OPA) geometric mean titers (GMTs) and Immunoglobulin G (IgG) geometric mean concentrations (GMCs) were measured immediately prior and 30 days postvaccination.Results: Both PCV15 formulations had generally comparable safety profiles to PCV13. Baseline IgG GMCs and OPA GMTs were comparable across vaccination groups. At 30 days postvaccination, both PCV15 formulations induced serotype specific antibodies to all 15 serotypes in the vaccine. IgG GMCs and OPA GMTs in recipients of either PCV15 formulation were non-inferior (≤ 2-fold margin) to those measured in recipients of PCV13 for shared serotypes and superior (> 1.0-fold difference) for serotypes unique to PCV15. Formulation B generally induced higher immune responses than Formulation A.Conclusion: In healthy adults ≥ 50 years of age, both new formulations of PCV15 displayed acceptable safety profiles and induced serotype-specific immune responses comparable to PCV13.

Capacity To Utilize Raffinose Dictates Pneumococcal Disease Phenotype.

Streptococcus pneumoniae is commonly carried asymptomatically in the human nasopharynx, but it also causes serious and invasive diseases such as pneumonia, bacteremia, and meningitis, as well as less serious but highly prevalent infections such as otitis media. We have previously shown that closely related pneumococci (of the same capsular serotype and multilocus sequence type [ST]) can display distinct pathogenic profiles in mice that correlate with clinical isolation site (e.g., blood versus ear), suggesting stable niche adaptation within a clonal lineage. This has provided an opportunity to identify determinants of disease tropism. Genomic analysis identified 17 and 27 single nucleotide polymorphisms (SNPs) or insertions/deletions in protein coding sequences between blood and ear isolates of serotype 14 ST15 and serotype 3 ST180, respectively. SNPs in raffinose uptake and utilization genes (rafR or rafK) were detected in both serotypes/lineages. Ear isolates were consistently defective in growth in media containing raffinose as the sole carbon source, as well as in expression of raffinose pathway genes aga, rafG, and rafK, relative to their serotype/ST-matched blood isolates. Similar differences were also seen between serotype 23F ST81 blood and ear isolates. Analysis of rafR allelic exchange mutants of the serotype 14 ST15 blood and ear isolates demonstrated that the SNP in rafR was entirely responsible for their distinct in vitro phenotypes and was also the determinant of differential tropism for the lungs versus ear and brain in a mouse intranasal challenge model. These data suggest that the ability of pneumococci to utilize raffinose determines the nature of disease.IMPORTANCES. pneumoniae is a component of the commensal nasopharyngeal microflora of humans, but from this reservoir, it can progress to localized or invasive disease with a frequency that translates into massive global morbidity and mortality. However, the factors that govern the switch from commensal to pathogen, as well as those that determine disease tropism, are poorly understood. Here we show that capacity to utilize raffinose can determine the nature of the disease caused by a given pneumococcal strain. Moreover, our findings provide an interesting example of convergent evolution, whereby pneumococci belonging to two unrelated serotypes/lineages exhibit SNPs in separate genes affecting raffinose uptake and utilization that correlate with distinct pathogenic profiles in vivo This further underscores the critical role of differential carbohydrate metabolism in the pathogenesis of localized versus invasive pneumococcal disease.

Biofilm production by Haemophilus influenzae and Streptococcus pneumoniae isolated from the nasopharynx of children with acute otitis media

BackgroundBiofilm production by Haemophilus influenzae and Streptococcus pneumoniae has been implicated in the pathogenesis of otitis media, mainly in chronic and recurrent cases. We studied the “in vitro” biofilm production by these 2 species isolated alone or together from the nasopharynx of children with acute otitis media.MethodsThe studied strains were from 3 pneumococcal conjugate vaccine (PCV) periods: pre-PCV7, post-PCV7/pre-PCV13 and post-PCV13. A modified microtiter plate assay with crystal violet stain was used to study the biofilm production of 182 H. influenzae and 191 S. pneumoniae strains.ResultsOverall, 117/181 (64.6%) H. influenzae and 128/191 (66.8%) S. pneumoniae strains produced biofilm. The proportion of biofilm-producing H. influenzae strains was greater with than without the isolation of S. pneumoniae in the same sample (75.5% vs 52.3%, p = 0.001). Conversely, the proportion of biofilm-producing S. pneumoniae strains was not affected by the presence or not of H. influenzae (66.3% vs 67.4%). S. pneumoniae serotypes 6B, 15B/C, 19A, 35F and 35B were the better biofilm producers (80%). Serotypes 11A, 14, 15A, 19F and 19A were more associated with H. influenzae biofilm-producing strains. Overall, 89/94 (94.6%) of cases with combined isolation showed biofilm production by S. pneumoniae or H. influenzae.ConclusionThis study emphasizes the high proportion of biofilm production by H. influenzae and S. pneumoniae strains isolated from the nasopharynx of children with acute otitis media, which reinforces the results of studies suggesting the importance of biofilm in the pathogenesis of acute otitis media.

Streptococcus infantis, Streptococcus mitis, and Streptococcus oralis Strains With Highly Similar cps5 Loci and Antigenic Relatedness to Serotype 5 Pneumococci.

Streptococcus pneumoniae is a highly impactful bacterial pathogen on a global scale. The principal pneumococcal virulence factor and target of effective vaccines is its polysaccharide capsule, of which there are many structurally distinct forms. Here, we describe four distinct strains of three Mitis group commensal species (Streptococcus infantis, Streptococcus mitis, and Streptococcus oralis) recovered from upper respiratory tract specimens from adults in Kenya and the United States that were PCR-positive for the pneumococcal serotype 5 specific gene, wzy5. For each of the four strains, the 15 genes comprising the capsular polysaccharide biosynthetic gene cluster (cps5) shared the same order found in serotype 5 pneumococci, and each of the serotype 5-specific genes from the serotype 5 pneumococcal reference strain shared 76–99% sequence identity with the non-pneumococcal counterparts. Double-diffusion experiments demonstrated specific reactivity of the non-pneumococcal strains with pneumococcal serotype 5 typing sera. Antiserum raised against S. mitis strain KE67013 specifically reacted with serotype 5 pneumococci for a positive Quellung reaction and stimulated serotype 5 specific opsonophagocytic killing of pneumococci. Four additional commensal strains, identified using PCR serotyping assays on pharyngeal specimens, revealed loci highly homologous to those of pneumococci of serotypes 12F, 15A, 18C, and 33F. These data, in particular the species and strain diversity shown for serotype 5, highlight the existence of a broad non-pneumococcal species reservoir in the upper respiratory tract for the expression of capsular polysaccharides that are structurally related or identical to those corresponding to epidemiologically significant serotypes. Very little is known about the genetic and antigenic capsular diversity among the vast array of commensal streptococcal strains that represent multiple diverse species. The discovery of serotype 5 strains within three different commensal species suggests that extensive capsular serologic overlap exists between pneumococci and other members of the diverse Mitis group. These findings may have implications for our current understanding of naturally acquired immunity to S. pneumoniae and pneumococcal serotype distributions in different global regions. Further characterization of commensal strains carrying homologs of serotype-specific genes previously thought to be specific for pneumococci of known serotypes may shed light on the evolution of these important loci.

Early-Onset Neonatal Pneumococcal Sepsis and Meningitis

Streptococcus pneumoniae invasive neonatal infection usually occurs during the second or third week of life and is infrequent in developed countries. Diagnosis remains challenging since clinical features of pneumococcal neonatal sepsis are indistinguishable to those produced by Streptococcus agalactiae (GBS) sepsis. Here we report a case of early-onset S. pneumoniae sepsis and meningitis by serotype 23F, included in the 13-valent vaccine (PVC13).

Biochemical studies of a β-1,4-rhamnoslytransferase from Streptococcus pneumonia serotype 23F.

A new β-rhamnoslytransferase Cps23FT from Streptococcus pneumonia serotype 23F was expressed and characterized. Its enzymatic activity and function were confirmed for the first time by utilizing enzymatically prepared dTDP-Rha and chemically synthesized Glcα-PP-(CH2)11-OPh as substrates. This reaction gave the desired disaccharide Rhaβ-1,4-Glcα-PP-(CH2)11-OPh in a good isolated yield (67%), suggesting the potential of Cps23FT as a tool enzyme for the synthesis of complex oligosaccharides containing difficult β-rhamnosyl linkages. Furthermore, site-directed mutagenesis of Cps23FT disclosed that its 271DKD273 motif was critical for the enzymatic activity and most likely the binding site for the required divalent metal cation.

Changes in the serotype distribution of Streptococcus pneumoniae causing otitis media after PCV13 introduction in Spain.

One of the beneficial effects of pneumococcal conjugate vaccines (PCVs) has been a decrease in the incidence of non-invasive infections, such as otitis media (OM) caused by vaccine serotypes. In this study, we analyzed the epidemiology of pneumococcal OM before and after PCV13 introduction in 2010. Between 2008 and 2016, the middle ear exudates from 2653 children under 14 years of age with OM were studied in two Spanish provinces (Gipuzkoa and Barcelona), and S. pneumoniae was isolated in 235 (8.9%) of cases. The 204 available isolates were serotyped and distributed in three 3-year periods: one before and two after PCV13 introduction (early and late post-PCV13). A significant decrease in the rate of OM caused by S. pneumoniae was observed mainly due to a decrease in infections caused by all PCV13 serotypes, although exceptions were observed including the persistence of serotype 3 in Gipuzkoa and a weak re-emergence of serotype 19F in both regions. The rate and diversity of non-PCV13 serotypes increased in both regions and an emerging clone causing OM was detected in each region: serotype 23B ST2372 in Gipuzkoa and serotype 11A ST838/ST6521 in Barcelona. The introduction of PCV13 has been followed by a change in the epidemiology of pneumococcal OM, with a decrease in the rate of vaccine serotypes accompanied by an increase in the diversity of non-vaccine serotype and the clonal spreading of different single clones in each region.

Innate Anti-microbial and Anti-chemotaxis Properties of Progranulin in an Acute Otitis Media Mouse Model.

Acute otitis media (AOM) is one of the most common infectious diseases primarily caused by Streptococcus pneumoniae (S.pn) among children. Progranulin (PGRN) is a multifunctional growth factor widely expressed in various tissues and cells. Studies have confirmed that PGRN is involved in the development of a variety of inflammatory diseases. We found that the expression of PGRN increased significantly in the middle ear of wild mice with AOM. However, its physiological functions in AOM still remain unknown. To examine the role of PGRN during AOM, we established an acute otitis media model in both C57BL/6 wild mice and PGRN-deficient (PGRN−/−) mice via transbullar injection with S.pn clinical strain serotype 19F. Interestingly, we observed dual results: on one hand, macrophage recruitment notably increased in PGRN−/− mice compared with WT mice; on the other hand, the overall bacterial clearance was surprisingly dampened in PGRN−/− mice. The enhanced recruitment of macrophages was associated with increased production of chemokine (C-C motif) ligand 2 (CCL2), while the decreased bacterial clearance was associated with impaired endocytosis capacity of macrophages. The scavenging ability of bacteria in PGRN−/− mice was recovered with administration of recombinant PGRN. These results suggested a novel dual role of PGRN in affecting the activities of macrophages.

Serotype distribution, antibiotic resistance pattern, and multilocus sequence types of invasive Streptococcus pneumoniae isolates in two tertiary pediatric hospitals in Beijing prior to PCV13 availability

ABSTRACT Background: Invasive pneumococcal disease (IPD) is a serious threat to children worldwide. This study reported the serotype distribution, antibiotic resistance pattern, and multilocus sequence types of 111 IPD strains isolated from children less than 14 years old in two tertiary pediatric centers in Beijing during the years 2012–2017. Methods: Serotypes were determined using Quellung reaction. Antibiotic resistance was tested using the E-test or disc diffusion method. Sequence types (STs) were assigned via multilocus sequence typing. Results: The most common serotypes of the IPD isolates were 19F, 19A, 14, 23F, and 6B, and the PCV13 coverage rate was 90.1%. For the meningitis isolates, the resistance rate to penicillin was 95.7%, and the non-susceptibility rate to ceftriaxone was 65.2%. All of the non-meningitis isolates were susceptible to penicillin, and the susceptibility rate to ceftriaxone was 89.8%. All but one of the isolates were highly resistant to erythromycin. The multidrug resistance rate of all isolates was 89.2%. The most common STs were ST320, ST271, ST876, and ST81, which belonged to serotype 19A, 19F, 14, and 23F, respectively. Conclusion: Given the high coverage rate of PCV13 and the worrisome non-susceptibility rate of IPD isolates to antibiotics, PCV13 use would be beneficial for Chinese children.

1441. Doses of 13-Valent Conjugated Pneumococcal Vaccine (PCV13) for Patients With Multiple Myeloma (MM)

BackgroundPatients with MM are vulnerable to bacterial infection, especially invasive pneumococcal diseases. Vaccination with one-dose PCV13 is recommended, but their poor immunogenicity was observed. We aimed to assess whether two-dose PCV13 might help.MethodsPatients with MM were randomized to receive one- or two- dose PCV13. The two doses were given 1 month apart. Measurements of antibody to the four most common serotypes 6B, 14, 19F, and 23F pre-vaccination, 1, 3, 6, 9, and 12 months after the last dose of PCV13 were performed. Achievement of significant antibody response was defined as greater than equal to twofold increase in the IgG level.ResultsFrom January 2016 to December 2017, a total of 72 patients were randomized to receive one (n = 35) or two doses (n = 37) PCV13. Of all, 31 patients (43%), including one dose in 14 and two doses in 17, had completed 12-month follow-up with a median age of 62 years old (IQR 54–66). Sequential changes of significant antibody responses to serotype 6B, 14, 19F, and 23F during 1-year follow-up in one and two does groups are presented in Figure 1. The proportions of significant antibody responses to serotype 6B, 14, 19F, and 23F after 1-year follow-up were 33.3, 25.0, 41.7, and 41.7% in one dose group and 11.8, 35.3, 29.4, and 23.5% in two-dose group, respectively.ConclusionTwo-dose PCV13 did not provide better immunogenicity to patients with MM. Innovative strategies to improve the immunogenicity of PCV13 in patients with MM are needed.Figure 1: Sequential changes of significant antibody responses to serotype 6B, 14, 19F, and 23F during 1-year follow-up in one- and two-dose groups. Disclosures All authors: No reported disclosures.

1430. Evolving Impact of 13-Valent Pneumococcal Conjugate Vaccine on Invasive Pneumococcal Disease

BackgroundThe 13-valent pneumococcal conjugate vaccine (PCV13) replaced PCV7 in the childhood immunization schedule in Massachusetts (MA) beginning in April, 2010. We describe the current epidemiology of invasive pneumococcal disease (IPD) in Massachusetts (MA) children after introduction of PCV13.MethodsCases of invasive pneumococcal disease (IPD) in children <18 years of age were detected through an enhanced surveillance system in MA since 2001. All cases in children and Streptococcus pneumoniae (SP) isolates, when available, are submitted to Department of Public Health (MDPH) and parents/physicians are interviewed for confirmation of demographic and clinical data. All available isolates are confirmed as SP, serotyped by Quellung reaction.ResultsThere were 351 IPD cases in MA children from April 1, 2010 to September 31, 2017, and 36 (10.3%) were in infants <6 months; 42 (12.0%) in children between 6 and 12 months; 63 (18.0%) in toddlers 12–24 months; 102 (29.1%) in children aged 2–5 years, and 108 (30.8%) were in children aged ≥5 years. Incidence of IPD declined to 6.8/105 children (95% CI 2.6–11.1) in 2015/2016 period which represents a 72.1% decline compared with 2010/2011 (24.4/105, 95% CI 16.3–32.5) (figure). However, in 2016/2017, IPD incidence increased to 10.4/105 children (95% CI 5.2–15.7). The most common clinical presentation was bacteremia (62.9%), followed by pneumonia (30.5%) and CNS disease (6.6%). Among, 103 (32.6%) children with ≥1 comorbidity, asthma (13.2%), hematologic malignancy (12.1%), prematurity (9.9%) and sickle cell disease (9.9%) were the most common comorbidities. He overall mortality rate was 5.1%. Isolates from 308 (89.3%) were available for serotyping; vaccine serotypes (VST) were identified in 106 (33.3%) IPD cases [19A (46.2%), 7F (19.9%), 3 (17.9%), 19F (10.4%), 6A (2.8%), 14, 18C, 5 (0.9% each). Serotypes 15BC (13.7%), 22F (12.6%) and 33F (11.8%) were the most common nonvaccine serotypes (NVST).ConclusionInvasive pneumococcal disease identified in the post-PCV13-era is primarily caused by NVSTs, specifically serotypes 15BC, 33F and 22F; and disproportionately observed in children with comorbid conditions. Continued surveillance is necessary to determine the impact of PCV13, as well as track potential changes in disease incidence and character due to NVST. Disclosures All authors: No reported disclosures.

2338. Change in Genetic Structure of Streptococcus pneumoniae Isolates From Invasive Diseases After National Immunization Program of Extended-Valency Pnuemococcal Conjugate Vaccines in Korea

BackgroundThis study investigated the genetic structure of Streptococcus pneumoniae isolates from invasive pneumococcal disease (IPD) in Korean children after national immunization program (NIP) of extended-valency pneumococcal conjugate vaccines (PCVs) in Korea from 2014 to 2017.MethodsInvasive isolates were collected from 23 hospitals throughout Korea. IPD cases were identified by isolating pneumococci from normally sterile sites. Each isolate was analyzed using standard microbiological techniques, Quellung reaction, multilocus sequence typing, and antimicrobial susceptibility testing. eBURST v3 software was used to estimate the relationships among the isolates and to assign the strains to a clonal complex (CC).ResultsNinety-two pneumococcal isolates were analyzed. The source of isolates were blood (77), cerebrospinal fluid (7), pleural fluid (2), joint fluid (2), deep tissue abscess (2), and peritoneal fluid (2). A total of 38 STs and 17 singletons were assigned. Ten clonal complexes were identified: CC320, CC81, CC166, CC439, CC558, CC880, CC3280, CC9395, CC180, and CC310. New STs were assigned: ST13552, ST13553, ST13554, and ST13602. The serotypes were mostly non-vaccine type (NVTs) (82.6%). The most prevalent STs were ST11189 (17.4%, n = 16, all serotype 10A), ST6945 (10.9%, n = 10, all serotype 12F), ST166 (9.8%, n = 9, serotype 11A [22.2%, n = 2], 13 [22.2%, n = 2], 15B/C [22.2%, n = 2], and 23A [33.3%, n = 3]), and ST320 (6.5%, n = 6, all serotype 19A). Major CCs identified were CC166 (11.9%), CC320 (10.9%), and CC81 (10.9%). Serotypes constituting CC81 and CC166 were all NVTs except 6A (n = 1) and 23F (n = 1) in CC81. CC320 consisted of 19A (n = 9) and 19F (n = 1). The relative proportion of NVTs was 61.3% in major CCs. All major three CCs showed multi-drug resistance. Nonsusceptibility to penicillin (80%) and cefotaxime (100%) was the highest in CC320 (serotype 19A [n = 9, 90.0%] and 19F [n = 1, 10.0%]).ConclusionThe introduction of extended-valency PCVs has resulted in the change of genetic structure of isolates from IPD of Korean children. In particular, two common CCs (CC81 and CC166), which previously contained vaccine types, were replaced with the NVTs, while CC320 remains unchanged.Disclosures All authors: No reported disclosures.

651. Non-encapsulation of Pneumococci as a Potential Evasion Mechanism From Vaccines

BackgroundOur group has been continuously performing epidemiological analyses on capsular types of pneumococci since 2007. Pneumococcal conjugate vaccine decreased the proportion of nonvaccine capsular types. Furthermore, null-capsule isolates that produced PspK were also identified in our analysis. In this study, we analyzed the genetic background of null-capsule pneumococci and the mechanism of nonencapsulation.MethodsTwenty-seven null-capsule isolates from 430 pneumococci that were isolated between 2010 and 2014 were used for this study. The capsular type was identified by DNA sequence-based methods, and genetic backgrounds were compared by multilocus sequence typing. Among the null-capsule isolates, the SP2852 strain was employed for non-encapsulation analysis. The pspK gene of this strain was replaced with ermB by homologous recombination (SP2852 ΔpspK::ermB). Then, genomic DNA from SP2852 ΔpspK::ermB was transformed into encapsulated isolates via natural transformation. Clindamycin-resistant isolates were further analyzed by sequence.ResultsThe proportion of null-capsule isolates tended to increase from 5% in 2010–2011 to 12.3% in 2014. These null-capsule isolates were classified into 14 STs that included STs previously identified as capsule-positive isolates. To assess non-encapsulation via natural transformation, two encapsulated strains (serotype 19F and 14) were cultured with genomic DNA from SP2852 ΔpspK::ermB. Subsequently, clindamycin-resistant null-capsule isolates were detected with high frequency (2.5 × 10–4–8.7 × 10–5). Sequence analysis showed capsular coding regions of these null-capsule isolates were replaced with that of ΔpspK::ermB. Furthermore, these isolates grew significant faster than their parent strains.ConclusionNull-capsule isolates with various genetic backgrounds were revealed gradually after introduction of vaccine. Moreover, encapsulated strains could take up genomic DNA of null-capsule isolates more easily and become a null-capsule strain by homologous recombination, suggesting that non-encapsulation and acquiring PspK resulted in the emergence of null-capsule strains by natural transformation. Furthermore, non-encapsulation could be beneficial for pneumococci as an evasion mechanism from vaccines.Disclosures All authors: No reported disclosures.

1468. PCV13 Serotype Trends Over Time in Pneumococcal Community Acquired Pneumonia: Which Method(s) Work Best?

BackgroundRecent studies have shown that a 13-valent pneumococcal conjugate vaccine (PCV13) was effective at preventing vaccine-type pneumococcal community acquired pneumonia (CAPSpn) in healthy adults. With the anticipated herd immunity from routine infant immunization with PCV13 used since 2010, the benefits of adult immunization in Canada were unclear and surveillance for CAPSpn with serotype distributions was needed. This study aimed to compare PCV13 serotype trends in CAPSpn from 2010 to 2015 using various laboratory methods.MethodsActive surveillance for CAP was performed from 2010 to 2015 in adult hospitals across five Canadian provinces. Bacteremic CAPSpn cases were identified using blood culture, and nonbacteremic CAPSpn cases by sputum culture or using a PCV13-specific urine antigen detection (UADPCV13). Serotype was assigned using Quellung reaction, PCR, or UADPCV13. CAPSpn cases were categorized by laboratory test(s), age, or disease (bacteremic or nonbacteremic CAPSpn).ResultsA diagnostic test for S. pneumoniae was performed on 6,687 CAP cases. S. pneumoniae positivity decreased from 2011 to 2014, and increased again in 2015. PCV13 serotypes followed a similar trend, where the decline in PCV13 serotypes attributed to serotypes 7F and 19A was noted, and the proportion of serotype 3 increased over time. Similar trends were seen regardless of whether data were categorized by laboratory test(s), age, or disease.ConclusionOur data suggest that all methods showed similar trends in PCV13 serotype distribution over 2010 to 2015. Herd immunity through childhood immunization with PCV13 was evident, but insufficient to afford complete protection to hospitalized adults. CAPSpn remained a significant cause of morbidity and mortality in hospitalized adult, and serotype 3 seems to be persisting despite herd immunity seen with other serotypes. Ongoing surveillance is required.Disclosures T. Hatchette, GSK: Grant Investigator, Research grant; Pfizer: Grant Investigator, Research grant; Abbvie: Consultant, Speaker honorarium. M. K. Andrew, GSK: Grant Investigator, Research grant; Pfizer: Grant Investigator, Research grant; Sanofi Pasteur: Grant Investigator, Research grant. A. McGeer, GSK: Grant Investigator, Research grant; Hoffman La Roche: Grant Investigator, Research grant; Sanofi Pasteur: Grant Investigator, Research grant. M. Semret, GSK: Grant Investigator, Research grant; Pfizer: Grant Investigator, Research grant. S. Trottier, CIHR: Grant Investigator, Research grant. S. A. McNeil, GSK: Grant Investigator, Research grant; Pfizer: Grant Investigator, Research grant; Merck: Collaborator and Consultant, Contract clinical trials and Speaker honorarium; Novartis: Collaborator, Contract clinical trials; Sanofi Pasteur: Collaborator, Contract clinical trials.

Vaccine-driven serotype-rearrangement is seen with latency in clinical isolates: Comparison of carried and clinical pneumococcal isolates from the same time period in Hungary

Young children – the main asymptomatic carriers of pneumococcus – are often the source of pneumococcal infections. PCV13 replaced PCV7 in 2010 in Hungary and it became a mandatory vaccine in 2014. In this work we surveyed the effect of vaccination in three groups: in healthy children under 7 years; in children of the same age but infected with pneumococcus (P1); in older patients (P2) who were very likely not vaccinated.Nasal swabs were taken from 522 healthy children to screen pneumococcal carriage between March 2015 and May 2016. In the same time period, 146 clinical isolates were collected, mainly from mucosal infections. Serotypes, antibiotic susceptibility and clonality of the isolates was determined and compared.The carriage rate was 39.1%. Regarding carriage, the serotype distribution showed the total disappearance of serotypes 3 and 6A compared to former Hungarian studies. The prevalence of PCV13 serotypes was only 5.8% represented by three serotypes (19F, 19A, 9V). Of note, serotype 19A (a very resistant and invasive type) also decreased significantly. In the patient groups, PCV13 prevalence was higher: 17.5% (P1) and 32.6% (P2). Although serotype 3 was present in P1 (7.9%), the leading serotype was 23B (22.2%), a non-vaccine type (NVT). P2 showed the most diverse serotype distribution, but serotype 3 was predominant here (15.7%). Pneumococcal isolates from the patients were more resistant towards the tested antibiotics compared to those from carriers.PCV13 seems to be highly successful in reducing the prevalence of vaccine serotypes. The serotype-rearrangement can be seen also among clinical isolates, albeit somewhat later in time. Fortunately, the replacing serotypes are less invasive and less resistant, but, most worrisome, serotype 19F can be found again with increased frequency among carriage isolates and mucosal infections. Further surveillance is needed to carefully monitor such successful, antibiotic resistant “refugees”.

A Population-Based Descriptive Atlas of Invasive Pneumococcal Strains Recovered Within the U.S. During 2015-2016.

Invasive pneumococcal disease (IPD) has greatly decreased since implementation in the U.S. of the 7 valent conjugate vaccine (PCV7) in 2000 and 13 valent conjugate vaccine (PCV13) in 2010. We used whole genome sequencing (WGS) to predict phenotypic traits (serotypes, antimicrobial phenotypes, and pilus determinants) and determine multilocus genotypes from 5334 isolates (~90% of cases) recovered during 2015–2016 through Active Bacterial Core surveillance. We identified 44 serotypes; 26 accounted for 98% of the isolates. PCV13 serotypes (inclusive of serotype 6C) accounted for 1503 (28.2%) isolates, with serotype 3 most common (657/5334, 12.3%), while serotypes 1 and 5 were undetected. Of 305 isolates from children <5 yrs, 60 (19.7%) were of PCV13 serotypes 19A, 19F, 3, 6B, and 23F (58/60 were 19A, 19F, or 3). We quantitated MLST-based lineages first detected during the post-PCV era (since 2002) that potentially arose through serotype-switching. The 7 predominant emergent post-PCV strain complexes included 23B/CC338, 15BC/CC3280, 19A/CC244, 4/CC439, 15A/CC156, 35B/CC156, and 15BC/CC156. These strains accounted for 332 isolates (6.2% of total) and were more frequently observed in children <5 yrs (17.7%; 54/305). Fifty-seven categories of recently emerged (in the post PCV7 period) putative serotype-switch variants were identified, accounting for 402 isolates. Many of these putative switch variants represented newly emerged resistant strains. Penicillin-nonsusceptibility (MICs > 0.12 μg/ml) was found among 22.4% (1193/5334) isolates, with higher penicillin MICs (2–8 μg/ml) found in 8.0% (425/5334) of isolates that were primarily (372/425, 87.5%) serotypes 35B and 19A. Most (792/1193, 66.4%) penicillin-nonsusceptible isolates were macrolide-resistant, 410 (34.4%) of which were erm gene positive and clindamycin-resistant. The proportion of macrolide-resistant isolates increased with increasing penicillin MICs; even isolates with reduced penicillin susceptibility (MIC = 0.06 μg/ml) were much more likely to be macrolide-resistant than basally penicillin-susceptible isolates (MIC < 0.03 μg/ml). The contribution of recombination to strain diversification was assessed through quantitating 35B/CC558-specific bioinformatic pipeline features among non-CC558 CCs and determining the sizes of gene replacements. Although IPD has decreased greatly and stabilized in the post-PCV13 era, the species continually generates recombinants that adapt to selective pressures exerted by vaccines and antimicrobials. These data serve as a baseline for monitoring future changes within each invasive serotype.

Serotypes and genotypes of S. pneumoniae isolates from adult invasive disease in Spain: A 5-year prospective surveillance after pediatric PCV13 licensure. The ODIN study

Serotypes/genotypes causing invasive pneumococcal disease (IPD) in adults are determined by vaccination strategies. The aim of this study was to assess the epidemiology of IPD in adults (≥18 years) after PCV13 introduction for children: serotypes, clonal complexes, antibiotic non-susceptibility and clinical presentations.We performed a prospective, clinical surveillance of hospitalized culture-confirmed IPDs in adults in nine Spanish hospitals (August 2010–June 2015). A total of 1087 culture-confirmed IPD episodes were included, of which 772 (71.0%) had bacteremic pneumonia (401 complicated/371 uncomplicated pneumonia), 122 (11.2%) meningitis, 102 (9.4%) non-focal bacteremia, 34 (3.1%) peritonitis and 57 (5.3%) others. The most common serotypes were: 3 (12.7%), 19A (8.5%), 8 (7.7%), 7F (6.3%), 1 (4.2%), 6C (4.2%), 11A (4.2%), 22F (4.2%) and 14 (4.0%). Vaccine types (PCV13 + 6C) caused 49.8% of IPD episodes, with a significant decrease over the 5-year period, and significant decreases in serotypes 6C and 7F. The most common genotypes were: CC180 (8.4%), CC191 (6.0%), and CC53 (5.0%).Vaccine types caused 53.9% (414/768) pneumonia episodes and 58.9% (235/399) complicated pneumonia, 53.4% IPD in adults <50 years (143/268), and 54.7% IPD in immunocompetent patients (337/616). Overall non-susceptibility was 25.9% to penicillin (1.1% for parenteral criteria), 24.9% to erythromycin and 2.7% to levofloxacin. ConclusionsAlthough the percentage of vaccine-types causing IPDs in adults significantly decreased, it remained high. Associations of vaccine types with pneumonia (with complicated pneumonia for specific serotypes), and immunocompetent patients point to the burden of IPD caused by PCV13 serotypes.