Comparative Analysis of Penicillin-Susceptible and Non-Susceptible Isolates of Group B Streptococci by Multilocus Sequence Typing

An increasing trend of neonatal invasive multidrug-resistant group B streptococcus infections in southern China, 2011-2017

Background

A multidrug-resistant (MDR) RR2 gene cluster was identified by whole-genome sequencing in several highly virulent (ST-17) Group B streptococcus (GBS) isolates, which caused neonatal invasive infections in southern China in 2016. Tracing the transmission and distribution of MDR isolates in this area is important for the effective management of future infections. The aim of this study was to obtain longitudinal data of MDR isolates to monitor epidemiological trends of general common isolates in southern China, and provide evidence for future characterization of antimicrobial resistance mechanisms.

Methods

Clinical information and antimicrobial susceptibility of GBS isolates were acquired from electronic information management system databases of the hospital under study between January 2011 and December 2017. To confirm the presence of intact RR2, the tetO, ant6, lnuB, and ant9 genes located upstream, midstream, and downstream of RR2 were detected by PCR and DNA sequencing.

Results

A total of 149 cases of neonatal invasive GBS infection were identified during the period 2011–2017. Among them, 119 cases (79.9%) were caused by MDR isolates, with a general increasing trend over the past 7 years. Further characterization of 11 isolates showed that six isolates causing late-onset disease (LOD) carry the tetO, ant6, and lnuB genes, which are located on RR2. Moreover, lnuB and ant9 consistently co-occurred in GBS isolates, which suggests their close proximity to one another in the RR2 gene cluster.

Conclusion

The MDR GBS is responsible for a large number of neonatal invasive infections and occurs with increasing frequency over time. Particularly, the MDR GBS isolates that cause LOD are more likely to carry the RR2 gene cluster, compared with those that cause early-onset disease. The rise in number of MDR GBS isolates emphasizes the pressing need for continuous surveillance to monitor their antibiotic susceptibility and epidemiology.

[Series of studies concerning group B streptococci with reduced penicillin susceptibility (PRGBS)]

Group B Streptococcus (GBS, Streptococcus agalactiae) is the cause of neonatal sepsis and meningitides. Moreover, this bacterium causes invasive infections to elderly people and patients suffering from diabetes et al. All clinical isolates of GBS, similar to other β-hemolytic streptococci, have been considered to be uniformly susceptible to β-lactams since 1940s, when penicillin was introduced to clinical setting. However, we analyzed clinical isolates of group B streptococci with reduced penicillin susceptibility (PRGBS), recovered in Japan during 1995-2005, and established their existence. Moreover, we promote series of studies concerning PRGBS. In this review, we describe series of studies concerning PRGBS.