Background: This is the first report of Laribacter hongkongensis that was isolated from the Rajavithi microbiology section at Rajavithi Hospital. L. hongkongensis is an emerging pathogen that causes bacteremia, community-acquired gastroenteritis and travel’s diarrhea. L. hongkongensis is a gram-negative with seagull- or S-shaped rod, facultative anaerobic, non-fermentative bacillus. The distribution of L. hongkongensis had been described worldwide, but because of limitation of methods for accurate identification of L. hongkongensis, data reports about of them were few.

Objective: To present the phenotypic characteristics and antimicrobial susceptibilities of L. hongkongensis (LHRJ) strain.

Materials and Methods: L. hongkongensis had isolated from hemoculture of a Rajavithi’s patient. Using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) method for L. hongkongensis identification, phenotypic characterization were described. The antimicrobial susceptibility of L. hongkongensis was determined.

Results: L. hongkongensis, Rajavithi (LHRJ) strain is motile, positive to urease, arginine dihydrolase, catalase, oxidase tests and reduce nitrate. The LHRJ strain was susceptible to most of antimicrobial agents, except ampicillin, cefotaxime, ceftriaxone, and ceftazidime.

Conclusion: L. hongkongensis is difficult to accurate identification by conventional biochemical method. Using the MALDI-TOF MS, which these bacteria database, has been identified accurately. However, some important characteristics of this bacterium have been reminded to microbiologists. The microbiology laboratory must be aware of accurate identification and antimicrobial susceptibility in the testing of L. hongkongensis isolates, especially in immuno-compromised patients, for appropriate treatment.

Keywords: Laribacter hongkongensis, MALDI-TOF MS, Antimicrobial susceptibility