Phenotypic and genotypic characteristic of invasive pneumococcal isolates from both children and adult patients from a multicenter surveillance in China 2005-2011

Abstract

Streptococcus pneumoniae is an important pathogen in both children and the elderly, but previous studies in China have provided limited information about invasive pneumococcal disease (IPD). A total of 240 IPD S. pneumoniae strains (from 105 children and 135 adults) were collected from 12 cities in China in 2005-2011. Their phenotypes and genetic characteristics were analyzed. Streptococcus pneumoniae remained highly resistant to macrolides, tetracycline, and cotrimoxazole each year. Serotypes were assigned to the 240 isolates, and 19A (22.1%), 19F (21.7%), 14 (7.5%), 3 (7.1%), and 23F (5.4%) were the most prevalent, accounting for 63.8% of all strains. Serogroup 19 strains were significantly more common among children than among adults (58.7% vs 32.4%, respectively; P < 0.001). Serotypes 19F and 19A demonstrated higher resistance to β-lactams and cephalosporins than the other serotypes. The coverage of PCV13 was superior to that calculated for PCV7 and PCV10 (77.9% vs 40.8% and 47.1%, respectively), and coverage was higher in children than in adults (85.6% vs 72.1%, respectively; P = 0.012). A multilocus sequence typing analysis revealed great diversity, with nine clonal complexes and 83 singletons among all the strains. Specifically, CC271 was more common in children, whereas singletons were more prevalent in adults. Among the serogroup 19 strains, 84.7% were ST271, ST320, or ST236, belonging to CC271. The homogeneous genetic background of 19F and 19A, together with the high resistance of these strains, suggests that clonal spread is responsible for the high prevalence of serogroup 19 in IPD. This is the first large study to investigate IPD strains in both children and adults in China.

Figure 1. The proportion of PCV-7 and clinical important serotypes in the year 2005-2011.

Figure 2. Population snapshot of 157 invasive pneumococcal isolates revealed by an eBURST analysis.

The size of the dot indicates the number of strains in each sequence type. Blue dot: Founding ST. Black dot with single linkage: Single locus variant (SLV). Black dot with two linkages: Double locus variant (DLV). Black dot without linkage: Singleton.