THE MODERN APPROACH: GROUP B STREPTOCOCCUS AND THE IMPORTANCE OF MICROBIAL WHOLE GENOME SEQUENCING

Background and Objective
Group B streptococcus (GBS) is a common cause of early-onset sepsis and meningitis in neonates, therefore prophylaxis is widely prescribed. However, there are concerns regarding over-treatment. Antibiotic resistance is increasing in GBS and the emerging threat of penicillin resistance has been reported. 
Modern routine microbiology laboratories are beginning to use whole genome sequencing (WGS) to improve diagnosis, typing and antimicrobial treatment of bacterial infections as well as for outbreak management. This review seeks to inform clinicians how WGS could be used to improve GBS detection and treatment.
Methods
The literature since 2000 was reviewed. In Ovid, Embase, PubMed and Google Scholar, the key words used were “group B streptococcus”, “Streptococcus agalactiae”, “molecular”, ”virulence gene”, “antibiotic resistance”, “whole genome sequencing” and “routine microbiology laboratory” and 54 relevant publications were identified.
Learning Points Discussion
-	Whole genome sequencing (WGS) has successfully been used for the identification of GBS directly from clinical samples, but it is not a routine method.
-	Serotyping with WGS is equivalent to established methods.
-	Detection of virulence genes, e.g. for toxins, or their absence might lead to improved understanding of who will benefit from antibiotic prophylaxis.
-	The presence of antibiotic-resistance genes could potentially improve the choice of antibiotics.

-	WGS can improve outbreak management. Where specific genetic traits are identified,   identification of symptomatic cases and improved screening of asymptomatic cases becomes possible.
-	GBS colonises different hosts, e.g. humans, dogs, fish, cattle, which could be the source of outbreaks.

-	Whole genome sequencing has a turn-around time of currently 3-4 days and costs are several times that of bacterial culture; this must improve for it to be used as standard in the modern routine microbiological laboratory.

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