Ecoepidemiology of Laribacter hongkongensis , a Novel Bacterium Associated with Gastroenteritis

Abstract

In a territory-wide surveillance study, Laribacter hongkongensis was isolated solely from freshwater fish (60% of grass carps, 53% of bighead carps, and 25% of mud carps). Comparing the pulsed-field gel electrophoresis patterns of fish and patient isolates revealed that most patient isolates were clustered together, suggesting that some clones could be more virulent.Laribacter hongkongensis was first discovered in Hong Kong from the blood and empyema pus of a 54-year-old Chinese man with alcoholic cirrhosis (5). Subsequently, L. hongkongensis was discovered in three of our patients and three patients in Switzerland with community-acquired gastroenteritis (3). In a multicenter prospective study, we confirmed that L. hongkongensis is associated with community-acquired gastroenteritis and traveler's diarrhea (4). Freshwater fish were shown to be a reservoir of L. hongkongensis (4). The isolation of L. hongkongensis from patients who resided in or have recently traveled to Asia, Europe, America, and Africa implied that the bacterium is likely to be of global importance.In this study, in order to determine the prevalence of L. hongkongensis in different animals commonly used for cooking in our locality, we carried out an ecoepidemiology study in Hong Kong. Furthermore, to determine the genetic diversity of L. hongkongensis, all L. hongkongensis isolates were typed by pulsed-field gel electrophoresis (PFGE). The PFGE patterns were compared to those of L. hongkongensis strains isolated from patients with gastroenteritis.Fecal swabs were obtained from 350 pigs and 80 cows, and cloacal swabs were obtained from 400 chickens, 50 ducks, and 50 geese from slaughter houses and poultry farms in Hong Kong with assistance from Veterinary Public Health Section of the Food and Environmental Hygiene Department. Three hundred and sixty freshwater fish (mostly farmed) of six different species and 360 marine fish of six different species commonly purchased for cooking in Hong Kong were obtained from 10 retail food markets (six fish per species per market) located in different districts of Hong Kong. Samples were obtained from the midguts and hindguts of the fish by using sterile cotton wool swabs. All samples were plated onto cefoperazone MacConkey agar and incubated under aerobic conditions at 37°C for 48 h (1). All suspected isolates were identified phenotypically by standard conventional biochemical methods (2). Isolates suspected to be L. hongkongensis were subjected to 16S rRNA gene sequencing (3, 4). All L. hongkongensis isolates were subjected to PFGE (3, 4). Digital images were stored electronically as TIFF files and analyzed visually and with GelCompar II (version 3.0; Applied Maths, Kortrijk, Belgium) by using the Dice coefficient and represented by the unweighted pair-group method using average linkages with 1% tolerance and 0.5% optimization settings.L. hongkongensis was isolated from the midguts and hindguts of 86 (24%) of 360 freshwater fish, including 36 (60%) grass carps, 32 (53%) bighead carps, 15 (25%) mud carps, and...

Plasmid profile and construction of a small shuttle vector in Laribacter hongkongensis

“…In a prospective study using cefoperazone/MacConkey agar as the selective medium (Lau et al 2003), we confirmed that L. hongkongensis is associated with communityacquired gastroenteritis and traveller's diarrhea (Woo et al 2004). Freshwater fish was confirmed to be a reservoir of it (Woo et al 2004;Teng et al 2005;Lau et al 2007). Pulsed-field gel electrophoresis (PFGE) of fish and patient isolates showed that most patient isolates were clustered together, suggesting that some clones could be more virulent than others (Teng et al 2005).…”

“…Freshwater fish was confirmed to be a reservoir of it (Woo et al 2004;Teng et al 2005;Lau et al 2007). Pulsed-field gel electrophoresis (PFGE) of fish and patient isolates showed that most patient isolates were clustered together, suggesting that some clones could be more virulent than others (Teng et al 2005). Isolation of L. hongkongensis from patients in or have recently travelled to Asia, Europe, America, and Africa implied that the bacterium is probably of global importance (Woo et al , 2005a.…”

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.…”