Molecular characteristics and antimicrobial resistance in invasive and noninvasive Group B Streptococcus between 2008 and 2015 in China

Group B streptococcus (GBS) is an increasing pathogen threat to newborns and adults with immunodepressive diseases. Here, a total of 193 GBS, including 51 invasive and 142 noninvasive isolates, were collected from the patients with infections in 7 tertiary hospitals from 5 cities in China during the year 2008 to 2015. The strains of GBS were characterized by classical and molecular techniques for capsular polysaccharide serotyping, genes for pilus island (PI) and et-like protein (alp), and antibiotic resistance profiling. Of 193 isolates, the predominant serotypes were III (45.6%) and Ia (18.7%). All strains carried at least 1 PI gene. The combination of PI-2b and PI-1 was present in 46.1% isolates, followed by PI-2a alone (80, 41.5%) and PI-2b alone (23, 11.9%). The most prevalent alp gene was rib (87, 45.1%), followed by alpha-C (47, 24.4%), epsilon (33, 17.1%), alp2/3 (7, 3.6%) and alp4 (2,1.0%), respectively. The clonal relationships between strains were investigated using multilocus sequence typing. The strains were distinguished into 26 individual sequence typing, and further clustered into 6 clonal complexes. A significant association was noted between the distributions of alp genes, serotyping and PI profiles, such as serotype III-rib-PI + PI-2a, Ib-alpha-C, and Ia-epsilon-PI-2a. No penicillin-resistant strains were detected, and 74.1%, 64.2%, and 68.9% were resistant to erythromycin, clindamycin, and tetracycline, respectively. The infective GBS isolates in China demonstrated epidemical features. (C) 2016 Elsevier Inc. All rights reserved.