A fishmonger with a thumb and thyroid abscess (swollen area with pus); healthy adults coming down with GBS bacteraemia and meningitis - these were the initial pieces of a puzzle that kicked off an island-wide investigation to solve the baffling GBS infections that struck down perfectly healthy adults in Singapore last year.

 

Prior to this, a rise in the number of patients with GBS meningitis in various hospitals earlier in the year intrigued Prof Koh Tse Hsien, Senior Consultant at SGH Department Pathology. He said, “I knew that fish could be a source of GBS. But it was an outrageous idea without precedent that perfectly healthy, young people can get seriously ill with brain and blood stream infections from eating raw fish.”

 

He got in touch with fellow clinicians who also watched the scenes unfold. Conversations between them and the close-knit community of microbiologists across the island led to the culprit.

 

Over at the Saw Swee Hock School of Public Health, National University of Singapore, data was analysed and it revealed that public sector hospitals across Singapore were all seeing an increase in GBS infection.

 

Tan Tock Seng Hospital had the technology to identify the type of GBS isolated from patients, which resulted in the identification of the particular strain of the bacteria ST283 that is associated with fish.

 

A further piece of the puzzle was unveiled when the SGH Infectious Disease (ID) physicians, through conversations with their patients, associated the infections with the eating of raw fish porridge. Armed with the information, Dr Koh’s team went to porridge stalls and fishmongers to buy samples of fish to investigate but were unable to isolate GBS. 
 
An aquatic animal veterinarian then suggested detecting the presence of GBS by polymerase chain reaction (PCR), which proved successful. 

 

“This episode is remarkable. The initial increase in cases may have been undetected if not for the constant communication between the microbiologists in the different hospitals,” said Prof Koh.

 

 

The other remarkable thing is that the lab, clinicians, different hospitals, public and private sector, universities and research institutes, government agencies, human, environmental, and animal health all worked together to achieve a successful conclusion in a relatively short space of time.

 

By the end of the year, there were 360 cases of GBS infection and some 150 were linked to the consumption of raw fish. The outbreak, caused by the Type III GBS ST283 strain, was the largest of its kind in the world. It was curbed after NEA and AVA’s advice against the sale of raw big head carp and giant snakehead for consumption.
 
A spirit of curiosity and the willingness to connect the dots led the clinicians to solve this microbial problem. The case they solved provides some evidence for the first time that serious GBS infection can be acquired from food.

 

“Textbooks on human infections never mention fish as a source of GBS infection. It helps to be very curious and be open to acquiring facts from different sources,” said Prof Koh.

 

He added, “Our lab work may seem routine, but behind every result is a patient.”