title: Epidemiology of pneumococcal serotype 6A and 6C among invasive and carriage isolates from Alaska, 1986-2009.
abstract: We investigated serotype 6A/6C invasive pneumococcal disease (IPD) incidence, genetic diversity, and carriage before and after 7-valent pneumococcal conjugate vaccine (PCV7) introduction in Alaska. IPD cases (1986-2009) were identified through population-based laboratory surveillance. Isolates were initially serotyped by conventional methods, and 6C isolates were differentiated from 6A by polymerase chain reaction. Among invasive and carriage isolates initially typed as 6A, 35% and 50% were identified as 6C, respectively. IPD rates caused by serotype 6A or 6C among children <5 years did not change from the pre- to post-PCV7 period (P = 0.71 and P = 0.09, respectively). Multilocus sequence typing of IPD isolates revealed 28 sequence types. The proportion of serotype 6A carriage isolates decreased from 7.4% pre-PCV7 to 1.8% (P < 0.001) during 2008-2009; the proportion of serotype 6C carriage isolates increased from 3.0% to 8.4% (P = 0.004) among children <5 years. Continued surveillance is warranted to monitor changes in serotype distribution and prevalence.
authors.affiliation: Arctic Investigations Program, Centers for Disease Control and Prevention, Anchorage, AK 99508, USA.
authors.forename: Karen
authors.initials: K
authors.lastname: Rudolph
authors.forename: Michael
authors.initials: M
authors.lastname: Bruce
authors.forename: Dana
authors.initials: D
authors.lastname: Bruden
authors.forename: Tammy
authors.initials: T
authors.lastname: Zulz
authors.forename: Jay
authors.initials: J
authors.lastname: Wenger
authors.forename: Alisa
authors.initials: A
authors.lastname: Reasonover
authors.forename: Marcella
authors.initials: M
authors.lastname: Harker-Jones
authors.forename: Debby
authors.initials: D
authors.lastname: Hurlburt
authors.forename: Thomas
authors.initials: T
authors.lastname: Hennessy
mesh_terms: D000413:Alaska / Q000453:epidemiology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002353:Carrier State / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D014644:Genetic Variation; D005838:Genotype; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D015994:Incidence; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D010406:Penicillins / Q000494:pharmacology; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control; D022242:Pneumococcal Vaccines / Q000008:administration & dosage; D012424:Rural Population; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D010406:Penicillins; D022242:Pneumococcal Vaccines