We report for the first time a case of bacteremia caused by Comamonas kerstersii in a 65-year-old patient with sign of diverticulosis. In addition, we review the isolation of Comamonas sp. and related organisms in our hospital over 25 years.
CASE REPORTC omamonas kerstersii is a nonfermenting betaproteobacterium described in 2003 that has long been considered nonpathogenic (1). This organism has recently been associated with intraabdominal infection due to perforation of the digestive tract (2). Here we describe a case of polymicrobial bacteremia due to C. kerstersii and Bacteroides fragilis in a 65-year-old diabetic man who was admitted to the emergency department of a hospital because of the sudden onset of fever and chills. The patient reported episodes of vomiting and diarrhea and mentioned that he had drunk water from a small river. Stool cultures performed after the beginning of antibiotic treatment did not disclose Salmonella, Shigella, Aeromonas, Campylobacter species, or C. kerstersii. The detection of Clostridium difficile toxins A and B and glutamate dehydrogenase antigen with the commercial C. difficile detection kit from Techlab was also negative. Blood samples (two pairs of culture bottles) were drawn from a peripheral vein, and the patient was discharged under treatment with oral ciprofloxacin for gastroenteritis of unknown origin. The blood cultures were processed by a Bactec FX automated blood culture system (Becton, Dickinson, Sparks, MD). A first aerobic blood culture bottle became positive 16 h 8 min after sampling, and Gram staining revealed the presence of long, filamentous, Gram-negative bacilli (Fig. 1). Bacterial identification by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (Bruker Daltonics GmbH, Leipzig, Germany) was performed on the same day by using a protocol that we recently developed on the basis of the analyses of a bacterial pellet preparation from the blood culture bottles (3-5). The strain was identified as C. kerstersii, a Gram-negative nonfermenting bacterium, and prompted the hospitalization of the patient. The patient was afebrile at that time, but palpation of the left lower abdominal quadrant was painful. An abdominal computed tomography (CT) scan revealed diverticulosis without evidence of diverticulitis. The anaerobic blood culture bottles from the same pair of samples became positive for Bacteroides fragilis 24 h 2 min after sample collection. We determined the following MICs (mg/liter) for the C. kerstersii strain by the Etest method