1203. Expansion of Multidrug-Resistant ST 320 Strains of Streptococcus pneumoniae Serotype 19A in Korea
Session: Poster Abstract Session: Other Bacterial Infections in Children
Saturday, October 22, 2011
Room: Poster Hall B1
Background: Multidrug-resistant Streptococcus pneumoniae serotype 19A has been increased even before the introduction of 7-valent pneumococcal conjugate vaccine (PCV7) in Korea. This study was performed to investigate the trend in the prevalence of serotype 19A, sequence types (ST), and antimicrobial susceptibilities of pneumococci isolated from infants and children after introduction of PCV7 in Korea.

Methods: A total of 146 pneumococcal isolates were obtained from children who visited Seoul National University Children's Hospital between 2007 and 2010. All 146 isolates were serotyped by Quellung reaction using antiserum. Minimal inhibitory concentrations (MICs) of 119 pneumococcal isolates were determined for 8 different antimicrobial drugs by E-test. Multilocus sequence typing (MLST) was performed for all serotype 19A isolates (n=43). Clinical data were reviewed retrospectively.

Results: Among 146 pneumococcal isolates, there were 39 invasive isolates (26 blood, 8 CSF, 3 pleural fluid, 1 ascites, and 1 joint fluid) and 107 non-invasive isolates (60 nasopharyngeal aspirate, 15 ear, 13 sputum, 9 endotracheal aspirate, 8 throat swab, and 2 wound swab). Overall, the most common serotypes were 19A (43, 29.5%), 19F (26, 17.8%), and 6B (18, 12.3%). PCV7 serotypes accounted for 41.1%. Serotype 19A was most common in both invasive (35.9%) and non-invasive (27.1%) isolates. Among 119 isolates tested for MIC, 101 (84.9%) isolates showed multidrug resistance (MDR) to at least three different classes of antimicrobials. MLST analysis of 43 serotype 19A strains revealed 5 STs: ST320 (39 isolates, 91%), and 4 other single variants of ST320; ST6398 (1), ST6399 (1), ST6400 (1), and ST6401 (1). Serotype 19A was most common serotype (38, 37.6%) among MDR strains, 95% of total 19A isolates showed MDR.

Conclusion: This study demonstrates that serotype 19A is still the most common serotype among pediatric isolates of pneumococci after introduction of PCV7. In addition, MDR ST320 strain is responsible for the expansion of serotype 19A. Further studies will be required to evaluate the impact of extended-valency pneumococcal conjugate vaccines on change in distribution of serotype and sequence type among pneumococci.

Subject Category: P. Pediatric and perinatal infections

Byung Ok Kwak, MD, Eun Young Cho, MD, Eun Hwa Choi, MD and Hoan Jong Lee, MD, Pediatrics, Seoul National University Children's Hospital, Seoul, South Korea


B. O. Kwak, None

E. Y. Cho, None

E. H. Choi, None

H. J. Lee, None

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