DISPATCHES Human Infection Caused by Clostridium hathewayi Sameer Elsayed*† and Kunyan Zhang*† We describe a 27-year-old man with acute cholecysti- tis, hepatic abscess, and bacteremia caused by Clostridium hathewayi, a newly described gram-negative, endospore- forming, rod-shaped bacterium. This report is the first of human infection caused by this microorganism. Tneous group of anaerobic, endospore-forming, rod- he genus Clostridium is a phylogenetically heteroge- shaped bacteria; they are usually gram positive, but some species may stain gram variable or gram negative (1,2). Clostridium strains are widely distributed in the environ- ment and form part of the normal colonic microflora of humans and many animals (1,2). More than 150 species have been described to date, but most are believed to be harmless saprophytes (1). Pathogenic Clostridium spp. may be involved in a wide variety of human infections or illnesses. Such conditions are usually endogenous (e.g., brain abscess, pneumonia, intrabdominal abscess, chole- cystitis, bacteremia) and arise from the host’s own microflora; other illnesses may be exogenous (e.g., food poisoning, pseudomembranous colitis, tetanus, botulism, myonecrosis) (1). The most commonly encountered, clini- cally important clostridia include Clostridium perfringens, C. clostridioforme, C. ramosum, C. butyricum, C. innocu- um, C. septicum, C. tertium, and C. difficile (1). C. hathe- wayi is a newly described species that was first reported by Steer et al. (3). The species was named after Charles L. Hatheway in recognition of his contributions to the C. bot- ulinum group of organisms (3). Case Report Our patient was a 27-year-old, previously healthy Chinese man who immigrated to Canada 10 years previ- ously. The patient sought treatment at the hospital for a 2- week history of intermittent fever and chills that were associated with sharp, nonradiating, right upper quadrant abdominal pain. He did not report nausea, vomiting, diar- rhea, or jaundice. The patient did not use alcohol heavily, use intravenous drugs, or engage in high-risk sexual activ- ity. The patient did not have a history of recent travel out- *University of Calgary, Calgary, Alberta, Canada; and †Calgary Laboratory Services, Calgary, Alberta, Canada side of Canada and was not taking any medications. His medical history and family history were unremarkable. Upon physical examination, the patient appeared mildly ill and had a temperature of 39.8°C, along with sinus tachy- cardia. Other findings were unremarkable except for mild right upper quadrant abdominal discomfort with deep pal- pation. Laboratory testing showed a peripheral leukocyto- sis with a left shift. Abdominal ultrasound and computed tomographic (CT) scans showed gallbladder wall thicken- ing and inflammation, multiple gallstones, and a single large fluid collection in the right lobe of the liver, with multiple adjacent smaller satellite fluid collections. Acute cholecystitis and hepatic abscess were diagnosed. Two sets of BacT/Alert FAN (bioMerieux Inc., Durham, NC) aero- bic and anaerobic blood cultures were drawn, after which the patient received empiric intravenous piperacillin- tazobactam therapy. A large liver abscess was drained by using CT scans as a guide; samples of the liver abscess were submitted for aerobic and anaerobic culture. Gram stain of abscess fluid showed heavy neutrophils and gram-negative rods. After 48 hours of incubation in the BacT/Alert 3D system (bioMerieux, Inc.), the anaerobic bottles from both sets of blood cultures were positive for similar, gram-negative, rod-shaped bacteria. The blood and abscess isolates did not grow aerobically, although anaerobic growth on brucella blood agar media (PML Microbiologicals, Wilsonville, OR) showed identical-looking, nonhemolytic, motile organisms, with colonial and microscopic morphologic features typical of Clostridium spp. However, endospores were not visualized initially, and the organisms persistent- ly stained gram negative. Growth was observed on anaer- obic phenylethyl alcohol agar; attempts to grow the organisms on kanamycin-vancomycin laked blood and bacteroides bile esculin agars (PML Microbiologicals) failed. Both isolates demonstrated sensitivity to van- comycin (5 µ g) and kanamycin (1,000 µ g) and resistance to colistin (10 µ g) special-potency identification discs. Tests for catalase, indole, lecithinase, lipase, and reverse Christie-Atkins-Munch-Peterson were negative. Since routine conventional phenotypic identification algorithms were not successful in identifying organisms, the isolates initially underwent partial 16S ribosomal RNA (rRNA) gene sequencing using MicroSeq 500 kits and an ABI Prism 3100 Genetic Analyzer (Applied Biosystems, Foster City, CA). Full-length sequencing of the 16S rRNA gene was subsequently performed for more definitive identifica- tion. The blood and abscess isolates had identical sequences; a GenBank BLAST (http://www.ncbi.nlm. nih.gov/BLAST/) search showed a 99% match of their full-length 16S rRNA gene profiles with those of a previ- ously characterized strain of C. hathewayi (GenBank accession no. AJ311620). Repeat subculture and Gram 1950 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 10, No. 11, November 2004