CASE REPORT Infectious Diseases, Microbiology & Parasitology DOI: 10.3346/jkms.2011.26.5.679 • J Korean Med Sci 2011; 26: 679-681 Bacteremia Caused by Laribacter hongkongensis Misidentified as Acinetobacter lwoffii: Report of the First Case in Korea Dae Sik Kim1, Yu Mi Wi1, Ji Young Choi2, Laribacter hongkongensis is an emerging pathogen in patients with community-acquired Kyong Ran Peck3, Jae-Hoon Song3,4, gastroenteritis and traveler’s diarrhea. We herein report a case of L. hongkongensis and Kwan Soo Ko2,4 infection in a 24-yr-old male with liver cirrhosis complicated by Wilson’s disease. He was admitted to a hospital with only abdominal distension. On day 6 following admission, he 1Department of Internal Medicine, Samsung Changwon Hospital, Sungkyunkwan University complained of abdominal pain and his body temperature reached 38.6°C. The results of School of Medicine, Changwon; 2Department of peritoneal fluid evaluation revealed a leukocyte count of 1,180/µL (polymorphonuclear Molecular Cell Biology, Samsung Biomedical leukocyte 74%). Growth on blood culture was identified as a gram-negative bacillus. The Research Institute, Sungkyunkwan University School isolate was initially identified asAcinetobacter lwoffiiby conventional identification of Medicine, Suwon; 3Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University methods in the clinical microbiology laboratory, but was later identified asL. hongkongensis School of Medicine, Seoul; 4Asia Pacific Foundation on the basis of molecular identification. The patient was successfully treated with for Infectious Diseases (APFID), Seoul, Korea cefotaxime. To the best of our knowledge, this case is the first report of hospital-acquired L. hongkongensis bacteremia with neutrophilic ascites. Received: 11 October 2010 Accepted: 25 February 2011 Key Words: Laribacter hongkongensis; Neutrophilic Ascites; Bacteremia Address for Correspondence: Kwan Soo Ko, PhD Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Korea Tel: +82.31-299-6223, Fax: +82.31-299-6229 E-mail: [email protected] INTRODUCTION CASE DESCRIPTION Laribacter hongkongensis is a facultative anaerobic, motile, non- A 24-yr-old male was admitted to a hospital, on August 16, 2007, sporulating gram-negative bacillus. It belongs to the family Neis- with a 15-day history of abdominal distension. The patient had seriaceae of the β subclass of Proteobacteria (1). Since the first been diagnosed with Wilson’s disease at 17-yr-of-age and had description of L. hongkongensis from the blood and empyema since undergone treatment for liver cirrhosis complicated by pus of a patient with alcoholic liver cirrhosis in 2001, the bacte- Wilson’s disease. The patient had no history of overseas travel rium has subsequently been associated with community-ac- and had no recall of ingesting undercooked freshwater fish for quired gastroenteritis (1, 2). However, accurate identification of at least the previous year. On physical examination, blood pres- L. hongkongensis is impossible using commercially-available sure was 98/49 mmHg, pulse rate was 96 beats per min, and phenotypic identification systems. Thus, the prevalence, patho- body temperature (36.5°C). All measurements were within the genic potential, and epidemiology of L. hongkongensis are un- normal range. Abdominal examination revealed a diffusely dis- clear. The identification based on a molecular approach could tended abdomen, diminished bowel sound, and splenomegaly. permit more accurate determinations of incidence and evalua- Laboratory tests revealed a hemoglobin concentration of 8.3 g/ tion of clinical relevance. dL, leukocyte count of 6,248/μL, platelet count of 42,000/μL, se- Although L. hongkongensis has been reported in Hong Kong, rum creatinine level of 0.94 mg/dL, serum bilirubin level of 6.7 China, and Hungary (3), it has not hitherto been identified in mg/dL, and serum albumin level of 1.6 g/dL. The analysis of peri- Korea. Recently, we experienced a case of L. hongkongensis bac- toneal fluid demonstrated an albumin level of 202 mg/dL and teremia with neutrophilic ascites. The bacterium was originally leukocyte count of 130/μL (poly 15%). Dose adjustment of diuret- misidentified asAcinetobacter lwoffii. Proper identification was ics was done to control ascites. The patient’s subsequent hospi- achieved using a molecular approach. tal course was uneventful. But, on day 6 following admission, fever developed, with a body temperature reaching 38.6°C. Ex- © 2011 The Korean Academy of Medical Sciences. pISSN 1011-8934 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. eISSN 1598-6357 Kim DS, et al. • Laribacter hongkongensis Bacteremia Microvirgula aerodenitrificans Sgly2T Table 1. Minimum inhibitory concentrations (MICs) of the isolate 07AC-292 in the antimicrobial susceptibility testing Aquaspirillum serpens IAM 13944T Antimicrobial agent MIC (mg/L) Resistance* Ampicillin/sulbactam 4/2 S 07AC-291 Cefepime 8 S 100 Laribacter hongkongensis HKU1T 85 Ceftriaxone 32 I Ceftazidime 8 S 98 Vogesella perlucida DS-28T Amikacin 8 S 95 Cefoperazone-sulbactam 8/4 - 94 93 Gulbenkiania mobilis E4FC31T Imipenem 0.06 S 100 Meropenem 0.06 S T Chromobacterium subtsugae RRAA4-1 Doripenem 0.06 S Chromobacterium pseudoviolaceum LMG3953T Pseudogulbenkiania subflava BP-5T Tetracycline 0.06 S Aquitalea denitrificans 5YN1-3T Ciprofloxacin 0.06 S 0.01 Rifampin 2 S Piperacillin-tazobactam > 256/4 R Fig. 1. Phylogenetic relationships of 07AC-292 and other species of the most similar sequences, retrieved from GenBank, based on partial 16S rRNA gene sequences. This Colistin 4 S unrooted tree was constructed by method of neighbor-joining. Numbers at branching Polymyxin B 2 S nodes are percentages of 1,000 bootstrap replications. Tigecycline 0.06 S *Since no validated interpretative criteria are available for L. hongkongnsis, the CLSI amination showed diffuse tenderness of the entire abdomen. breakpoints for Acinetobacter spp. were used to determine susceptibilities (6). R, The results of peritoneal fluid evaluation revealed a leukocyte resistant; I, intermediate; S, susceptible. count of 1,180/μL (poly 74%). Empirical treatment with cefotax- ime (2 g every 8 hr) was commenced with a presumptive diagno- Institute (CLSI) protocol (6). Minimum inhibitory concentration sis of spontaneous bacterial peritonitis. Two days later, growth breakpoints and quality-control protocols were used according on blood culture was identified as a gram-negative bacillus us- to non-fermenting gram-negative organism guidelines estab- ing the BacT ALERT 3D culture system. The isolate was desig- lished by the CLSI. Isolate 07AC-292 was resistant to piperacil- nated 07AC-292. However, no organism was identified in the lin, intermediate resistant to ceftriaxon, and susceptible to the peritoneal fluid. The patient responded to cefotaxime and was other tested antibiotics (Table 1). discharged on post-admission day 12. To identify isolate 07AC-292, biochemical characterization DISCUSSION by VITEK2 with an ID-GNB card was performed in accordance with the manufacturer’s instructions. The isolate was identified L. hongkongensis was first isolated from a 54-yr-old Chinese male as A. lwoffii at a confidence level of 94%. However, an Acineto- with alcoholic cirrhosis and thoracic bacateremic empyema (1, bacter differentiation method using therpoB gene (4) indicated 2). Subsequently, the bacterium has been isolated from patients that the isolate did not belong to the genus Acinetobacter. Thus, in other parts of the world. The isolation of L. hongkongensis we tried to identify isolate 07AC-292 accurately using a molecu- from patients who are residents in, or recent travelers to, Asia, lar method. The DNA of the isolate was extracted and a portion Europe, America, and Africa imply the global importance of the of the 16S rRNA gene was amplified and sequenced using the bacterium (7). Most reported cases were associated with recent primer set as previously described (5). A 1,346-bp sequence was travel and eating fish and symptoms are similar to salmonella obtained. The determined sequences were compared with the and campylobacter gastroenteritis (2). Although freshwater fish GenBank public database using the BLASTn program (http:// is probably a major reservoir of L. hongkongensis, differences blast.ncbi.nlm.nih.gov/Blast.cgi). The 16S rRNA sequence of the exist between isolates obtained from humans and fish using isolate 07AC-292 showed complete identity with several L. hon- pulsed-field gel electrophoresis, suggesting that not all environ- gkongensis strains in the database. Thus, isolate 07AC-292 was mental clones are virulent (8). definitively identified as L. hongkongensis. A phylogenetic tree The presently-reported patient, who had underlying liver cir- constructed based on 16S rRNA gene sequences also supported rhosis associated with Wilson’s disease, was suffering from neu- the identity of isolate 07AC-292 as L. hongkongensis (Fig. 1). trophilic ascites caused by L. hongkongensis. In contrast to pre- Antibiotic susceptibility testing (ampicillin-sulbactam, ce- vious described cases, the patient denied a history of ingestion fepime, ceftriaxone, ceftazidime, amikacin, cefoperazone-sul- of undercooked