Nonserotypeable Pneumococcus: Phenotypic Dynamics in the Era of Anticapsular Vaccines

• Published in: Journal of Clinical Microbiology 2010-03, Vol.48 (3), p.831-835
• Main Authors: Marsh, R, Smith-Vaughan, H, Hare, K.M, Binks, M, Kong, F, Warning, J, Gilbert, G.L, Morris, P, Leach, A.J
• Format: Article
• Language: English
• Subjects: Applied microbiology; Australia - epidemiology; Bacterial Capsules - biosynthesis; Bacterial Capsules - genetics; Bacterial Proteins - genetics; Bacterial Typing Techniques; Bacteriology; Biological and medical sciences; Carrier Proteins - genetics; Carrier State - epidemiology; Carrier State - microbiology; Child; Child, Preschool; DNA Fingerprinting; Fundamental and applied biological sciences. Psychology; Genotype; Heptavalent Pneumococcal Conjugate Vaccine; Humans; INDEL Mutation; Infant; Infant, Newborn; Microbiology; Miscellaneous; Molecular Epidemiology; Penicillin Resistance; Pneumococcal Infections - epidemiology; Pneumococcal Infections - microbiology; Pneumococcal Vaccines - immunology; Population Groups; Serotyping; Streptococcus pneumoniae; Streptococcus pneumoniae - classification; Streptococcus pneumoniae - genetics; Streptococcus pneumoniae - isolation & purification; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects)
• ISSN: 0095-1137; 1098-660X
• DOI: 10.1128/JCM.01701-09

Nonserotypeable pneumococci (NSP) are commonly carried by Australian Indigenous children in remote communities. The purpose of this study was to characterize carriage isolates of NSP from Indigenous children vaccinated with the seven-valent pneumococcal conjugate vaccine (PCV7) and to use these data to guide decisions on reporting of NSP. A total of 182 NSP were characterized by BOX typing, antibiogram analysis, and multilocus sequence typing (MLST) of common BOX types. NSP positive for the wzg capsule gene were analyzed by a multiplex PCR-based reverse line blot hybridization assay (mPCR/RLB-H) targeting capsule genes to determine the serotype. Among 182 NSP, 49 BOX types were identified. MLST of 10 representative isolates found 7 STs, including ST448 (which accounted for 11% of NSP). Non-penicillin susceptibility was evident in 51% of the isolates. Pneumococcal wzg sequences were detected in only 23 (13%) NSP, including 10 that contained an ~1.2-kb insert in the region. mPCR/RLB-H identified serotype 14 wzy sequences in all 10 NSP, and 1 also contained a serotype 3-specific wze sequence. Among the remaining 13 wzg-positive NSP, few belonged to the serotypes represented in PCV7. It appears that most NSP identified in Australian Indigenous children are from a true nonencapsulated lineage. Few NSP represented serotypes in PCV7 that suppress capsular expression. High rates of carriage and penicillin resistance and the occasional presence of capsule genes suggest a role for NSP in the maintenance and survival of capsulated pneumococci. To avoid the inflation of pneumococcal carriage and antibiotic resistance rates, in clinical trials, we recommend separate reporting of rates of capsular strains and NSP and the exclusion of data for NSP from primary analyses.