Group B Streptococcus (Singapore) Update 4, 2015
It has been a while since I last updated on the local Group B Streptococcus (GBS) outbreak in Singapore that is linked to the consumption of raw bighead carp.
The good news is that there has been a dramatic fall in the number of cases of severe GBS after the National Environment Agency (NEA) recommended licensed food stalls to stop selling raw bighead carp and toman fish. From an average of 20 cases a week since the start of the year, it has now fallen back to the weekly baseline of 3 cases a week. Pretty conclusive if indirect implication of the raw bighead carp as the source of the GBS outbreak.
There has been a further step forward on the research front with the sequencing of the outbreak GBS genome. The data and annotations are available publicly on Genbank here. The isolate was obtained from the blood of a patient with bacteraemia and meningitis, and he had consumed raw bighead carp approximately 10 days before the onset of his infection. It was processed by the Singapore General Hospital’s Diagnostic Bacteriology Laboratory, and sequenced by Dr. Swaine Chen and his team at the Genome Institute of Singapore within two weeks. There has been press releases, which one can view here and also at the Straits Times site. I think it is quite amazing how far technology has progressed, enabling us to determine the full genetic code of the outbreak pathogen within a matter of weeks. There is a nice diagram comparing the genome of this outbreak ST283 GBS with other GBS genomes obtained from humans, fish and other animals, which was created by Dr. Matthew Holden from St. Andrew’s University in Scotland. Unfortunately, this is part of a manuscript and can only be shown after it has been published.
Hopefully, this will be the last local outbreak caused by this GBS strain, especially if NEA and the Ministry of Health persist with the advisory (or outright ban) of selling raw bighead carp for consumption. We still do not understand how it got into the carp, and therefore whether this particular strain of GBS can eventually spread to other fish. Sporadic ST283 GBS infections are still occasionally seen in Hong Kong, according to a source in Hong Kong. Nonetheless, perhaps more rapid diagnostic tests for both food products and patients can be made now that the genome sequence is available.