(See the article by Lipsitch et al., on pages 1221-7.)Background. Pneumococcal conjugate vaccines (PCVs) prevent vaccine serotype (VT) invasive disease; nonvaccine serotype (NVT) disease increases modestly. The impact of PCV on nasopharyngeal (NP) colonization is essential to understanding disease effects.Methods. We conducted a community-randomized controlled trial with catch-up vaccination through age 2 years investigating the effect of 7-valent PCV (PnCRM7) on NP colonization among American Indian infants and their unvaccinated contacts. Infants receiving blinded vaccine at 2, 4, 6, and 12-15 months of age had NP cultures obtained at age 7, 12, and 18 months. Serotype-specific colonization was detected by immunoblot.Results. We enrolled 566 vaccinated and 286 unvaccinated children from 511 households and collected 5157 specimens, of which 3525 (68.4%) had pneumococcus. PnCRM7 vaccinees were less likely to be colonized with VT (odds ratio [OR], 0.40 [95% confidence interval {CI}, 0.23-0.67]) but were more likely to be colonized with NVT pneumococci (OR, 1.67 [95% CI, 1.02-2.78]). PnCRM7 vaccinees were less densely colonized with VT strains than control vaccinees (OR, 0.61 [95% CI,). Day care-attending unvaccinated children in PnCRM7 communities were less likely to have VT colonization than those in control communities (OR, 0.27 [95% CI, 0.07-1.07]).Conclusions. PnCRM7 reduces the risk of VT acquisition and colonization density but increases the risk of NVT acquisition among vaccinees and their household contacts.
Field studies of Streptococcus pneumoniae (pneumococci) nasopharyngeal (NP) colonization are hampered by the need to directly plate specimens in order to ensure isolate viability. A medium containing skim milk, tryptone, glucose, and glycerin (STGG) has been used to transport and store NP material, but its ability to preserve pneumococci has not been evaluated. Our objective was to qualitatively and semiquantitatively evaluate the ability of STGG to preserve pneumococci in NP secretions. Entwined duplicate calcium alginate NP swab samples were obtained from children. One swab was plated directly onto a gentamicin blood agar plate; the other was placed in STGG. Growth from the directly plated specimen was compared with growth from an STGG aliquot immediately cultured or stored at ؊70°C for 9 weeks, ؊20°C for 9 weeks, or 4°C for 5 days. Of 186 specimens, 96 (52%) were positive for pneumococci from the direct plating; 94 (98%) of these were positive from the fresh STGG specimen. Pneumococci were recovered from all 38 positive specimens frozen at ؊70°C, all 18 positive specimens frozen at ؊20°C, and 18 of 20 positive specimens stored at 4°C. Recovery of pneumococci after storage of NP material in STGG medium at ؊70°C is at least as good as that from direct plating. Storage at ؊20°C is also acceptable. Storage at 4°C for 5 days is not ideal.Streptococcus pneumoniae (pneumococci) is the most important cause of bacterial otitis media, pneumonia, bacteremia, and meningitis among children worldwide (12,15,17). Pneumococci are also important because the rate of nonsusceptibility to various classes of antimicrobial agents, such as penicillins and cephalosporins, is rising throughout the United States and worldwide (4,18,19). Prevention efforts have been hampered by the lack of a vaccine which is immunogenic for important serotypes in children younger than 2 years of age. A seven-valence pneumococcal conjugate vaccine (Prevnar; Wyeth Lederle Vaccines) which is immunogenic and efficacious in this age group recently has been licensed in the United States for use among children through 9 years of age and is recommended routinely for those under 2 years of age (1, 3, 16). The effect of this and other conjugate pneumococcal vaccines on nasopharyngeal (NP) colonization is a subject of intense investigation.It is well known that pneumococci are spread from person to person via the respiratory route. NP colonization studies have shown that people acquire pneumococci at a young age, carry these organisms for various periods of time, may carry more than one serotype at a time, and transmit these organisms to others with whom they are in close contact (2,5,(9)(10)(11)14). Many studies of the dynamics and ecology of pneumococcal NP carriage, particularly in the setting of new conjugate pneumococcal vaccines, will be performed in settings where microbiologic facilities are not readily available.An optimal medium has not been validated for the transport, preservation, and recovery of pneumococci from NP material. One medium, STGG (skim m...
The bioterrorism-associated human anthrax epidemic in the fall of 2001 highlighted the need for a sensitive, reproducible, and specific laboratory test for the confirmatory diagnosis of human anthrax. The Centers for Disease Control and Prevention developed, optimized, and rapidly qualified an enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) antibodies to Bacillus anthracis protective antigen (PA) in human serum. The qualified ELISA had a minimum detection limit of 0.06 µg/mL, a reliable lower limit of detection of 0.09 µg/mL, and a lower limit of quantification in undiluted serum specimens of 3.0 µg/mL anti-PA IgG. The diagnostic sensitivity of the assay was 97.8%, and the diagnostic specificity was 94.2%. A competitive inhibition anti-PA IgG ELISA was also developed to enhance diagnostic specificity to 100%. The anti-PA ELISAs proved valuable for the confirmation of cases of cutaneous and inhalational anthrax and evaluation of patients in whom the diagnosis of anthrax was being considered.
Vaccine-type pneumococcal carriage was lower among adults and unvaccinated children living with a PCV7 vaccinee. This is attributable to reduced exposure and reduced transmission when exposure occurs.
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