Vaccine Serotypes of Streptococcus pneumoniae with High-level Antibiotic Resistance Isolated More Frequently Seven Years After the Licensure of PCV7 in Beijing.

Background: Streptococcus pneumoniae 7-valent conjugate vaccine (PCV7) was made available in China in the private sector in September 2008.

Methods: This study investigated the serotype distribution, antibiotic resistance, and molecular characteristics of S. pneumoniae in hospitalized pediatric patients. Pneumococcal isolates were collected from hospitalized children younger than 14 years. Their serotypes were determined using Quellung reactions with antisera; antibiotic resistance against 13 antimicrobials was tested using the E-test method or disc diffusion. The sequence types (STs) were analyzed with multilocus sequence typing.

Results: A total of 187 pneumococcal specimens were collected, including 21 invasive and 166 noninvasive isolates. The prevailing serotypes were 19F (31.6%), 19A (19.8%), 23F (11.2%), 6A (9.1%), 14 (9.1%) and 15B (5.9%). The coverage rates of PCV7, PCV10 and PCV13 were 56.2% (105/187), 56.7% (106/187) and 86.1% (161/187), respectively. The overall nonsusceptibility rate against penicillin was 8.0%; however, this rate would have been 91.5% if based on an oral breakpoint. All but one of the isolates were highly resistant to erythromycin. Multidrug resistance was exhibited by 177 (94.7%) isolates. The 5 predominant multilocus sequence typings for all pneumococci were ST271 (24.1%), ST320 (18.2%), ST81 (7.5%), ST876 (7%) and ST3397 (5.3%), which were primarily related to serotypes 19F, 19A, 23F, 14 and 15B, respectively. CC271 was the most frequent antibiotic-resistant complex clone.

Conclusions: The coverage rates of PCVs were high, and the antibiotic resistance rates were of serious concern among hospitalized children. Universal immunization using PCVs would likely prevent episodes of S. pneumoniae diseases and the spread of antibiotic resistance in Beijing.