Current status and future directions for Laribacter hongkongensis, a novel bacterium associated with gastroenteritis and traveller's diarrhoea

Purpose of review: Despite extensive investigations, a microbiological cause cannot be found in about half of the patients with infectious disease. Throughout the years, scientists have spent tremendous efforts in looking for microorganisms associated with these 'unexplained infectious disease syndromes'. Recently, a novel bacterium, Laribacter hongkongensis, was discovered and shown to be associated with gastroenteritis and traveller's diarrhoea. This review summarizes the current status, and shares with the readers the authors' experience in the microbiology, classification, epidemiology, clinical disease, laboratory diagnosis, antibiotic resistance and treatment of L. hongkongensis. It also discusses the importance and perspective of describing novel pathogenic bacterial species. Recent findings: L. hongkongensis was shown to be associated with gastroenteritis and traveller's diarrhoea. Consumption of fish was associated with recovery of L. hongkongensis. Freshwater fish was a reservoir of L. hongkongensis. Genotypic typing revealed the possibility of virulent clones of L. hongkongensis. The class C β-lactamase of L. hongkongensis has been cloned and characterized. Summary: In 2001, L. hongkongensis, a novel genus and species, was first discovered in Hong Kong from the blood and empyema pus of a patient with alcoholic cirrhosis. Subsequently, it was isolated from patients in other parts of the world. Recently, this bacterium was found to be associated with community-acquired gastroenteritis and traveller's diarrhoea using cefoperazone MacConkey agar as the selective medium. Further studies, including setting up of animal and tissue culture models and characterization of virulence factors, should be performed. For pathogenic microbes, even one strain of a novel species should be described, so that global concerted efforts can be drawn to look for more cases associated with such a pathogen.