Isolation of Laribacter hongkongensis, a novel bacterium associated with gastroenteritis, from drinking water reservoirs in Hong Kong

Abstract

Aims: Freshwater fish has been found to be the reservoir of Laribacter hongkongensis, a recently discovered bacterium associated with community‐acquired gastroenteritis. However, little is known about the ecology of this bacterium in the aquatic environment. We carried out a surveillance study to investigate the presence of L. hongkongensis in water and freshwater fish from 10 drinking water reservoirs in Hong Kong. Methods and Results: Using membrane filtration, L. hongkongensis was isolated from the waters of six reservoirs, with numbers ranging from 1 to 12 CFU l−1. Higher recovery rates were observed in summer and during days of higher water and ambient temperatures. Of 27 freshwater fish collected from the reservoirs, L. hongkongensis was recovered from the intestines of two fish, a Goldfish and a Nile tilapia. Overall, 35 different pulsed‐field gel electrophoresis patterns are found among the 59 isolates recovered from water and the two isolates from freshwater fish. Conclusions: The present report represents the first to demonstrate the presence of L. hongkongensis in natural water environments. Significance and Impact of the Study: Although it is unlikely that treated, drinking water is an important source of L. hongkongensis‐associated gastroenteritis, one should be aware of the possibility of other contaminated water as a source of human infection.

A novel MLST sequence type discovered in the first fatal case of Laribacter hongkongensis bacteremia clusters with the sequence types of other human isolates

“…7,10 To extract bacterial DNA, 80 µL of 0.05 M NaOH were added to 20 µL of bacterial cells suspended in distilled water, and the mixture was incubated at 60 °C for 45 min, followed by the addition of 6 µL of Tris-HCl (pH 7.0), achieving a final pH of 8.0. The resultant mixture was diluted ×100, and 5 µL of the diluted extract was used for polymerase chain reaction (PCR).…”

“…2,8 This species has also been isolated from drinking water reservoirs, Chinese tiger frogs and little egrets. 9,10,11 Pulsed-field gel electrophoresis and multilocus sequence typing (MLST) demonstrated that the fish and patient isolates fall into separate clusters, suggesting that some clones could be more virulent or adapted to humans. 8,12 The complete genome of L. hongkongensis was recently sequenced, and this bacterium's mechanism of acid resistance was characterized.…”

Gene Amplification and Sequencing for Bacterial Identification

“…As a result of the easy access to clinical specimens, the oral cavity and the gastrointestinal tract are the most important sources for bacterial discovery in humans Woo, Tse, Lau, et al, 2005;Woo, Wong, et al, 2010;Woo et al, 2014;Yuen et al, 2001). The use of 16S rRNA gene sequencing for detection has also facilitated downstream studies of these novel bacteria to help understand their disease associations, pathogenicity, transmission routes and potential reservoir(s) (Couturier, Slechta, Goulston, Fisher, & Hanson, 2012;Curreem et al, 2011;Elsendoorn, Robert, Culos, Roblot, & Burucoa, 2011;Faibis et al, 2008;Kim et al, 2011;Lau, Fan, et al, 2012Lau et al, 2005Lau et al, , 2009Lau, McNabb, et al, 2007;Lau, Wong, Li, Woo, & Yuen, 2008;Lau, Woo, Fan, Lee, et al, 2007;Lau, Woo, Fan, Ma, et al, 2007;Lau, Woo, Hui, et al, 2003;Ni et al, 2007;Smith, Pandey, & Ussher, 2012;Tang et al, 2013;Teng, Huang, et al, 2014;Teng et al, 2005;Uckay et al, 2007;Woo, Kuhnert, et al, 2003;Woo, Lau, Teng, & Yuen, 2005;Woo, Ma, et al, 2005Woo, Tam, et al, 2002;Woo, Teng, Lau, & Yuen, 2006;Woo, Teng, et al, 2004Woo, Wong, et al, 2010;Woo et al, 2014;Xiong et al, 2014;Yuen et al, 2001).…”

Two-dimensional gel electrophoresis in bacterial proteomics

“…L. hongkongensis is a recently discovered β-Proteobacterium that is associated with community-acquired gasteroenteritis and traveler's diarrhea (Yuen et al, 2001;Woo et al, 2004;Woo et al, 2005). It can inhabit in the intestines of freshwater fish, frogs and humans, and can also grow independently in freshwater environments (Woo et al, 2004;Teng et al, 2005;Lau et al, 2007;Ni et al, 2007;Lau et al, 2009). Therefore it needs to cope with varying environmental temperatures in these different growth habitats.…”