Efficacy of Solithromycin (CEM-101) for Experimental Otitis Media Caused by Nontypeable Haemophilus influenzae and Streptococcus pneumoniae.

Solithromycin (CEM-101) is a "fourth-generation" macrolide, as it has three binding site and is acid stable. The three binding sites confer activity against bacteria resistant to the older macrolides and ketolides, including multidrug-resistant Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi). The objective of this study was to evaluate solithromycin pharmacokinetics (PK), middle ear fluid (MEF) concentrations, and microbiologic efficacy in a chinchilla model of experimental otitis media (EOM) due to strains of S. pneumoniae or NTHi. Plasma PK (maximum concentration of drug in serum [Cmax] and area under the concentration-time curve from 0 to 24 h [AUC0-24]) and middle ear fluid (MEF) concentrations were determined. Isolates with specified antimicrobial susceptibility patterns were inoculated directly into the middle ear (ME). Plasma and MEF were collected for PK and MEF cultures performed to determine efficacy. Solithromycin administered at 150 mg/kg of body weight/day resulted in Cmax and AUC0-24 values of 2.2 µg/ml and 27.4 µg · h/ml in plasma and 1.7 µg/ml and 28.2 µg · h/ml in extracellular MEF on day 1. By day 3, Cmax and AUC0-24 values had increased to 4.5 µg/ml and 54 µg · h/ml in plasma and 4.8 µg/ml and 98.6 µg · h/ml in extracellular MEF. For NTHi EOM, three isolates with MIC/minimal bactericidal concentration (MBC) ratios of 0.5/1 µg/ml (isolate BCH1), 2/2 µg/ml (isolate BMC1247C), and 4/4 µg/ml (isolate BMC1213C) were selected. The MEF of >85% of animals infected with BCH1 and BMC1247C was sterilized. For NTHi BMC1213, >85% of MEF cultures remained positive. For S. pneumoniae EOM, 3 isolates with MIC/MBC ratios of 0.06/0.125 µg/ml (S. pneumoniae 331), 0.125/1 µg/ml (S. pneumoniae CP-645 [MLSB phenotype]), and 0.5/2 µg/ml (CP-712 [mefA subclass mefA resistance]) were selected. Solithromycin sterilized MEF in 100% of animals infected with S. pneumoniae 331 and S. pneumoniae CP-645. ME infection persisted in 60% of animals infected with CP-712. In a model of EOM, solithromycin sterilized MEF in >85% of animals challenged with NTHi with an MIC of ≤2 µg/ml and 100% of ME infected with S. pneumoniae with an MIC of ≤0.125 µg/ml.

Do community-level predictors of pneumococcal carriage continue to play a role in the conjugate vaccine era?

This paper examined whether previously identified community-level factors (high proportion of crowded households and/or persons below the poverty level) remained associated with childhood pneumococcal carriage in the heptavalent pneumococcal conjugate vaccine (PCV7) era. Using logistic regression, individual factors were used to develop base models to which community-level factors were added to evaluate impact on pneumococcal carriage within two paediatric study cohorts from Massachusetts (urban Boston, outside Boston). Six years after introduction of universal childhood PCV7 vaccination, we found no consistent evidence that census tract characteristics (e.g. population size and density, age and race distribution, percent participating in group childcare, parental education, percent lacking in-unit plumbing, poverty, and community stability) affected odds of pneumococcal carriage when added to individual predictors (e.g. younger age, current respiratory tract infections, and attendance in group childcare). How community-level factors influence pneumococcal carriage continues to change in the era of increasing immunization coverage.

Streptococcus pneumoniae serotype 6C: an intra- and interclonal complex comparison.

We report the annotated draft genome sequences of four serotype 6C Streptococcus pneumoniae isolates of differing genetic backgrounds. Serotype 6C isolates are increasing in prevalence and becoming progressively more resistant to antibiotics. As a result, these strains are likely to become more important in the near future.

Functionally inert HIV-specific cytotoxic T lymphocytes do not play a major role in chronically infected adults and children.

The highly sensitive quantitation of virus-specific CD8(+) T cells using major histocompatibility complex-peptide tetramer assays has revealed higher levels of cytotoxic T lymphocytes (CTLs) in acute and chronic virus infections than were recognized previously. However, studies in lymphocytic choriomeningitis virus infection have shown that tetramer assays may include measurement of a substantial number of tetramer-binding cells that are functionally inert. Such phenotypically silent CTLs, which lack cytolytic function and do not produce interferon (IFN)-gamma, have been hypothesized to explain the persistence of virus in the face of a quantitatively large immune response, particularly when CD4 help is impaired. In this study, we examined the role of functionally inert CTLs in chronic HIV infection. Subjects studied included children and adults (n = 42) whose viral loads ranged from <50 to >100,000 RNA copies/ml plasma. Tetramer assays were compared with three functional assays: enzyme-linked immunospot (Elispot), intracellular cytokine staining, and precursor frequency (limiting dilution assay [LDA]) cytotoxicity assays. Strong positive associations were observed between cell numbers derived by the Elispot and the tetramer assay (r = 0.90). An even stronger association between tetramer-derived numbers and intracellular cytokine staining for IFN-gamma was present (r = 0.97). The majority (median 76%) of tetramer-binding cells were consistently detectable via intracellular IFN-gamma cytokine staining. Furthermore, modifications to the LDA, using a low input cell number into each well, enabled LDAs to reach equivalence with the other methods of CTL enumeration. These data together show that functionally inert CTLs do not play a significant role in chronic pediatric or adult HIV infection.

Characterization of antigens from nontypable Haemophilus influenzae recognized by human bactericidal antibodies. Role of Haemophilus outer membrane proteins.

Major outer membrane antigens, proteins, and lipopolysaccharides (LPSs), from nontypable Haemophilus influenzae were characterized and examined as targets for complement-dependent human bactericidal antibodies. Outer membranes from two nontypable H. influenzae isolates that caused otitis media and pneumonia (middle ear and transtracheal aspirates) were prepared by shearing organisms in EDTA. These membranes were compared with membranes prepared independently by spheroplasting and lysozyme treatment of whole cells and found to have: similar sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns of the proteins; identical densities (rho = 1.22 g/cm3); and minimal d-lactose dehydrogenase activity indicating purity from cytoplasmic membranes. Outer membranes were solubilized in an LPS-disaggregating buffer and proteins were separated from LPS by molecular sieve chromatography. The SDS-PAGE patterns of outer membrane proteins (OMPs) from the two strains differed in the major band although other prominent bands appeared similar in molecular weight. LPS prepared by hot phenol water extraction of each of the strains contained 45% (pneumonia isolate) and 60% (otitis isolate) lipid (wt/wt), 49% and 50% carbohydrate (wt/wt), respectively, and less than 1%, 3-deoxy-manno octulosonic acid. Immunoglobulin M (IgM) purified from normal human serum (NHS) plus complement was bactericidal for both strains. Purified immunoglobulin G (IgG) from NHS killed the middle ear isolate and immune convalescent IgM from the serum of the patient with pneumonia killed his isolate. NHS or convalescent serum were absorbed with OMPs and LPS (0.6-110 micrograms) from each of the strains and immune specific inhibition of bactericidal antibody activity by each antigen was determined. OMPs from the pulmonary isolate inhibited bactericidal antibody activity directed against the isolate in both NHS (1.5 microgram of antigen) and immune serum (0.75 microgram of antigen). OMPs (60 micrograms) from the ear isolate also inhibited bactericidal activity in the respective immune serum. LPSs exhibited minimal inhibition (greater than 110 micrograms). Three human sera (two normal, one immune) were selectively depleted of 80% of antibody activity against OMPs (measured by enzyme-linked immunosorbent assay) by affinity chromatography using OMPs from the pulmonary isolate coupled to a solid phase. These OMP antibody-depleted sera also showed an 88% reduction of bactericidal activity against this strain. Immunopurified antibody against OMPs eluted from the solid phase was bactericidal.

Surveillance of pneumococcal colonization and invasive pneumococcal disease reveals shift in prevalent carriage serotypes in Massachusetts' children to relatively low invasiveness.

BACKGROUND: Following the introduction of pneumococcal conjugate vaccines (PCV), overall nasopharyngeal colonization rates have not changed significantly, however a dramatic and sustained decline in invasive pneumococcal disease (IPD) in children was observed in every setting where the PCVs were implemented. We aimed to describe the differences in invasive disease potential of serotypes that are common colonizers in pre- and post-vaccine eras in order to provide further insight in our understanding of dynamic epidemiology of pneumococcal diseases. METHODS: Using data from surveillance of nasopharyngeal carriage and enhanced surveillance for IPD, a serotype specific "invasive capacity (IC)" was computed by dividing the incidence of IPD due to serotype x by the carriage prevalence of that same serotype in children <7years of age in Massachusetts. We have evaluated the serotype specific invasive capacity in two periods; pre-PCV13 (2001/02, 2003/04, 2006/07, 2008/09) and post-PCV13 (2010/11 and 2013/14), and by age groups; <24monthsvs. ≥24months. RESULTS: An approximate 50-fold variation in the point estimate was observed between the serotypes having the highest (7F, 38, 19A, 3, 33F) and the lowest (6C, 35B, 21, 11A, 23B and 23A) computed serotype specific invasive disease potential. In the post-PCV13 era (6C, 35B, 11A, 23B and 23A), 5 of the 7 most common serotypes colonizing the nasopharynx were serotypes with the lowest invasive capacity. Serotype specific invasive capacity trended down in older children for majority of the serotypes, and serotypes 3, 10A and 19A had significantly lower invasive capacity in children older than 24months of age compared to younger children. CONCLUSION: Invasive capacity differs among serotypes and likely by age. Point estimates of IC for most of the common serotypes colonizing children in Massachusetts in post-PCV13 era were low and likely explain the continued reduction in IPD from the pre-PCV era in the absence of specific protection against these serotypes.

Antibody response to measles and rubella vaccine by children with HIV infection.

To determine the immunogenicity of the measles and rubella components of the measles, mumps, and rubella virus (MMR) vaccine in human immunodeficiency virus (HIV)-infected children, we compared their response to that of uninfected controls. Sera were collected from HIV-infected patients and HIV seroreverters followed in our clinic and tested as close to 2 months post-MMR vaccination as possible. Specific IgG to both rubella and measles were measured by enzyme-linked immunosorbent assay. Of 20 children with HIV, 11 responded with adequate levels of antibody to measles. In the seroreverters, 12 of 13 responded. Of the measles responders, the median antibody level was significantly lower in the HIV-infected group than in the seroreverter group. In addition, HIV-infected responders tested at 9-15 months after vaccination demonstrated a significant decline in measles antibody levels. Although there was not a difference between the two cohorts in the proportion of patients who responded to the rubella component of the vaccine, there was a significant difference in the median antibody level of the responders of the two groups. We did not find a statistical difference in CD4 counts between responders and nonresponders. Alternate strategies will need to be established to prevent measles in HIV-infected children.

The incidence of prenatal syphilis at the Boston City Hospital: a comparison across four decades.

OBJECTIVE: To examine the incidence and epidemiologic correlates of congenital syphilis at an inner-city Boston hospital, and draw comparisons with the situation at the same hospital 40 years ago. DESIGN: Chart review and comparison with data collected in 1951. SETTING: Maternity and pediatric services at Boston City Hospital. METHODS: A study conducted in 1951 on the maternity service of Boston City Hospital in which demographic data were collected on all women admitted in labor over a 5-month period was replicated. Serologic testing for syphilis was carried out on these women, and the demographic and medical correlates of positive maternal syphilis serology were examined. This study was repeated exactly 40 years later, using the cord blood screening for syphilis done routinely at delivery and a review of prenatal records. RESULTS: From a group made up largely of married white women in 1951, the study population shifted in 1991 to a group made up mostly of minority women, with 75% unmarried. In 1951, 24 patients were diagnosed with syphilis either before or during the pregnancy, giving a prevalence rate of 2.4%. In 1991, 25 of 647 women were diagnosed with syphilis, for a prevalence rate of 3.9%. The women with positive cord blood serologies had a higher rate of other sexually transmitted diseases and substance abuse. No symptomatic cases of congenital syphilis were seen in 1951 or in 1991, although at least 11 of the 26 infants born to mothers with positive serologies in 1991 received intravenous penicillin therapy. CONCLUSIONS: The continued prevalence of diagnosed syphilis in women at delivery reflects an inner-city epidemic of congenital syphilis that is tied to substance abuse, human immunodeficiency virus, and changing social patterns, as well to older problems of serologic screening, prenatal care, treatment failures, and maternal reinfection. It is essential that screening programs be maintained and improved in this high-risk population, and that infants born to mothers with positive serologies receive full and adequate treatment if there is any doubt at all about their infection status.

New concepts in the pathophysiology and management of middle ear disease in childhood.

Middle ear disease encompasses acute otitis media, recurrent otitis media, and otitis media with effusion. For many children, middle ear disease occurs early in life, is chronic and recurrent and can impair language development and/or school performance. Risk factors for recurrent otitis media include early disease onset, bottle feeding, daycare attendance, exposure to cigarette smoke and immunological defects or immaturity. Antimicrobial therapy in acute otitis media is associated with earlier resolution and a reduction in the frequency of persistent disease and suppurative complications. An antimicrobial agent should be selected according to its activity, tolerability and concentrations achieved in the middle ear. At present, amoxicillin remains the drug of choice for acute otitis media. Antimicrobial prophylaxis is also effective, but only for the duration of therapy. Future challenges for the management of middle ear disease include the treatment of penicillin-resistant Streptococcus pneumoniae, effective prevention of relapses, and the development of a vaccine for S. pneumoniae that has the appropriate serotypes and is immunogenic in young children.

Seroreversion in human immunodeficiency virus-exposed but uninfected infants.

The goal of this study was to describe seroreversion (SR) in a cohort of human immunodeficiency virus-exposed but uninfected infants. Groups of patients who seroreverted very early or late were examined for salient clinical and immunologic characteristics of the mother or infant. The mean time (+/- s.d.) to seroreversion by enzyme-linked immunoabsorbent assay (ELISA) was 50.1 +/- 14.8 weeks, or 11.6 months (n = 84); the range of times to antibody loss by ELISA was 17.9 to 82.0 weeks. The mean time to seroreversion by Western blot was 68.3 +/- 12.6 weeks, or 15.8 months (n = 51), with a range of 44.9 to 94.1 weeks. Initial anti-human immunodeficiency virus titer as measured by cord blood ELISA optical density (OD) was found to relate significantly to mean time to seroreversion. No relationship to time to seroreversion was demonstrated for gestational age, maternal or neonatal serum immunoglobulin concentrations, maternal CD4 cell counts, maternal alcohol consumption, infantile diarrhea or failure to thrive. The lengthy time to seroreversion seen here demonstrates the 1994 revised Centers for Disease Control and Prevention definition of human immunodeficiency virus infection (based on seropositivity by both ELISA and confirmatory tests persisting beyond 18 months of age) to be accurate in our population. We recommend Western blot testing be used as confirmation for positive ELISAs only after 18 months of age.

Otitis media in children born to human immunodeficiency virus-infected mothers.

Acute otitis media (AOM) is thought to occur frequently in children infected with human immunodeficiency virus (HIV). We compared experience with AOM of 28 HIV-infected children with that of 33 children who seroreverted to HIV antibody negative status by age 18 months. The mean number of episodes/year of AOM for children who seroreverted decreased from 1.33 in the first year of life to 0.13 in the third year, whereas the mean number of episodes/year in HIV-infected children increased from 1.89 to 2.40. By age 3 years, all HIV-infected children had experienced 1 or more episodes of AOM, and 80% had experienced 6 or more, whereas 75% of children who seroreverted had experienced 1 or more episodes, and none had had 6 or more. HIV-infected children with normal T4 lymphocyte counts had a mean of 1.18 episodes of AOM in the first year of life compared with 2.35 episodes in HIV-infected children with decreased counts (P = 0.023). HIV-infected children with low counts had a nearly 3-fold increased risk of recurrent AOM (47% vs. 18%).

The immunogenicity of Haemophilus influenzae type b conjugate vaccines in children born to human immunodeficiency virus-infected women. Women and Infants Transmission Study Group.

BACKGROUND: Immunocompromise caused by HIV-1 infection increases the importance of receipt of routine childhood vaccines to prevent infections such as invasive Haemophilus influenzae type B (Hib) disease. The objectives of the study were to evaluate the immunogenicity of Hib conjugate vaccines among HIV-infected children according to clinical and immunologic disease progression as well as viral load. METHODS: The concentration of antibody to polyribosylribitol phosphate (PRP) was measured at approximately 9 and 24 months of age in plasma specimens from children of HIV-infected women enrolled in the Women and Infants Transmission Study. RESULTS: Among 227 children (35 HIV-infected, 192 uninfected) at the 9-month study visit who were known to have received age-appropriate immunization with CRM197 mutant Corynebacterium diphtheriae protein-conjugated Hib vaccine, geometric mean antibody concentrations were lower among HIV-infected children (1.64 microg/ml) than among uninfected children (2.70 microg/ml), although the difference was not statistically significant. Anti-PRP antibody concentrations did not vary significantly among these HIV-infected children with predominantly mild-moderate disease progression according to clinical category, immunologic stage or viral load (P > or = 0.48). The proportion of children with antibody concentrations > or = 1.0 microg/ml did not vary significantly according to HIV infection status (73% uninfected, 74% infected) or, if infected, clinical or immunologic disease progression or viral load. Similar results were obtained among 127 children (17 HIV-infected, 110 uninfected) eligible for analysis at the 24-month study visit. Changes in antibody concentrations over time (between 9 and 24 months of age) did not differ significantly among 10 HIV-infected as compared with 72 uninfected children (P=0.81). CONCLUSIONS: These results suggest that HIV-infected children with predominantly mild-moderate disease progression respond reasonably well in terms of a quantitative antibody response to Hib conjugate vaccines during the first 2 years of life. Research to further characterize the immune response to Hib conjugate vaccines and to further delineate the "durability" of anti-PRP antibody concentrations beyond 2 years of life should be pursued.

Early neurodevelopmental growth in children with vertically transmitted human immunodeficiency virus infection.

OBJECTIVE: To examine mental and motor development in children with vertically transmitted human immunodeficiency virus (HIV) infection in the first 30 months of life. DESIGN: Prospective longitudinal study comparing two groups: children with HIV infection and HIV-exposed but uninfected children. SETTING: Pediatric Immunodeficiency Clinic at Boston (Mass) City Hospital, Boston University Medical Center. STUDY PARTICIPANTS: Twenty-four children with vertically transmitted HIV infection and 27 children who were born to HIV-infected mothers and became HIV negative served as controls. Socioeconomic status, gestational age, and prenatal drug exposure were comparable in the two groups. MEASUREMENTS/RESULTS: Using the Bayley Scales of Infant Development, all children were assessed at least once between 4 and 16 months and again between 17 and 30 months of age. Individual mean mental and motor scores were calculated for the early and later age span. Motor development in the infected group was delayed in comparison to the seroreverter group in both age spans and remained stable in both groups over time. Mental development was comparable in the two groups at 4 to 17 months, but HIV infection was associated with delay in mental development at 17 to 30 months of age. CONCLUSION: Early and persistent delay in motor development and deceleration in mental development in late infancy distinguishes many children who are HIV infected from exposed but uninfected children, but there is significant variability in early neurodevelopmental outcome among children with HIV infection.

Career choice in one general pediatric Title VII--supported residency.

The concern that there are too few generalist physicians and too many specialists is part of the ongoing health care debate. Medical educators have been challenged at the graduate and undergraduate levels to educate more generalists. While some question the actual effect of medical education on the choice of a generalist career, others strongly express the view that a generalist curriculum influences graduates to pursue a career in primary care. Residency training programs are largely based in hospitals, and pediatric practice is largely community based. The terms educational malpractice, educational mismatch, and, most recently, educational dysjunction have been used to describe the difference between the educational and practice experience.

The draining ear. Otitis media and externa.

Otorrhea, or discharge from the ear, may be associated with otitis media or otitis externa. Each episode of otorrhea requires examination of the external ear canal and middle ear to determine the origin and extent of disease, a complete understanding of the pathogenesis, and a therapeutic approach that considers the microbiology and the extent of tissue invasion. This review focuses on infections of the middle ear and external ear commonly associated with otorrhea. The pathogenesis, clinical manifestations, methods of diagnosis, and medical and surgical therapies are presented.

Defining resistance: breakpoints and beyond implications for pediatric respiratory infection.

The emergence of isolates of Streptococcus pneumoniae with reduced susceptibility to penicillins, cephalosporins, trimethoprim-sulfamethoxazole, and macrolide antibiotics requires a re-evaluation of strategies for the treatment of community-acquired respiratory disease. One response has been the consideration of withholding initial antimicrobial therapy for children with acute otitis media (AOM). Review of clinical studies supports a reduction in suppurative complications, and a more rapid resolution of signs and symptoms as well as the course of middle ear disease in children treated with antimicrobial agents. Breakpoints established by the NCCLS for in vitro susceptibility reporting may not reflect clinical efficacy at all sites of disease. Clinical studies of AOM due to penicillin-resistant S. pneumoniae report success with both cefuroxime and amoxicillin-clavulanic acid, however, microbiologic studies suggest an increase in persistent infection in children with disease due to isolates with reduced susceptibility. Successful therapy for AOM due to highly resistant isolates (MIC > or = 2.0 micrograms/ml for penicillin) has been reported with clindamycin, ceftriaxone, and high-dose amoxicillin. The current risk of AOM due to a resistant S. pneumoniae remains low in most U.S. communities. Amoxicillin remains appropriate for most children, ongoing surveillance for resistance and close monitoring of response to therapy is necessary.

Acquired immunodeficiency syndrome: a new population of children at risk.

Cases of AIDS in children have been described since 1982. Diagnosis is more complex in children than in adults owing to the more varied clinical presentations and the difficulty in interpretation of laboratory tests. Our current understanding of HIV infection in children is reviewed, as well as the controversies regarding medical, psychosocial, and public health issues.

Otitis media in the newborn infant.

Otitis media occurs frequently in newborn infants and often is associated with systemic infection. Patients studied at the Boston City Hospital have provided preliminary data on the otoscopic findings, tympanometric patterns and etiologic agents characteristic of otitis in this age group.

Modeling the decline in pneumococcal acute otitis media following the introduction of pneumococcal conjugate vaccines in the US.

We hypothesized that following the introduction of PCV7, the exchange of vaccine serotypes (VST) for non-vaccine serotypes (NVST) in the nasopharynx has resulted in fewer episodes of pneumococcal acute otitis media (AOM) due to the reduced capacity for common NVST strains to cause disease. We modeled the change in the proportion of children colonized with S. pneumoniae who would develop pneumococcal AOM that would occur due to serotype replacement, and projected the future impact of PCV13. Our model is based on observed changes in the nasopharyngeal pneumococcal serotype distribution from the pre- to post-PCV7 era, and an estimated capacity of each serotype to produce pneumococcal AOM given colonization; the latter was derived by dividing serotype-specific disease prevalence by serotype-specific carriage prevalence in the same population. Our results indicate a 12% (95% CI 0.5-26) decline in the number of AOM episodes attributable to S. pneumoniae in children less than 3 years of age between 2000 and 2007 due to the combined effects of PCV7 vaccine efficacy and vaccine-induced serotype replacement, and predicts that PCV13 will further decrease pneumococcal AOM an additional 27% (95% CI 13-40) from 2007 to 2013. Evaluation of changes in VST disease revealed a 91% (95% CI 83-97) decrease in PCV7-VST AOM from 2000 to 2007, and predicted an additional 65% (95% CI 57-74) decrease in PCV13-VST AOM from 2007 to 2013. Our model indicates that following vaccination, nasopharyngeal replacement of VST by NVST has led to a decrease in the amount of pneumococcal AOM despite a consistent rate of S. pneumoniae colonization, and that pneumococcal AOM may continue to decrease as pneumococcal serotypes with greater capacity to cause disease are replaced by less locally invasive serotypes.

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.