Bacteremia caused by Clostridium tertium in a neutropenic patient with acute myeloid leukemia: Case report and review

Abstract

The isolation of Clostridium species from a blood specimen frequently presents a dilemma to clinicians and microbiologists. This is particularly true for C. tertium that have generally been assumed to be nonpathogenic in immunocompetent hosts. However, this non histotoxic, lipolytic, or toxin-producing organism may cause severe infections in immunocompromised patients. Until now, 75 cases of bacteremia caused by C. tertium have been reported, especially in patients with acute leukemia. Although clostridial bacteremia should be suspected in cancer patients who present with high fever, rapid hemolysis, rapidly advancing tissue necrosis, and septic shock, fever of unknown origin is the most common clinical presentation of C. tertium bacteremia. Gastrointestinal tract is a very possible source of infection, especially in patients being neutropenic as a result of recent chemotherapy. Additionally, in half of the reported cases there is evidence of local infection, such as perianal cellulitis, diarrhea, or rectal abscess. A history of exposure to third generation cephalosporins, antibiotics in which the organism is resistant, is a factor associated with C. tertium bacteremia. Mortality related to C. tertium bacteremia is 9.2%. Neutropenia and polymicrobial sepsis, especially when microbes from enteric flora are present, are probably the most important risk factors for a fatal outcome. C. tertium can be misidentified as either a poorly growing Bacillus species or even one of the other two aerotolerant Clostridium species. It is easily decolorized in gram-stained smears and can be mistaken for a Gram-negative organism. Such misidentification could have serious consequences. Although penicillin and clindamycin show excellent activity against most of the Clostridium species, resistance may occur for C. tertium. In view of this unusual susceptibility pattern, an accurate diagnosis of infection with this organism is important for the choice of an appropriate antimicrobial treatment. Vancomycin, teicoplanin, metronidazole, ciprofloxacin and imipenem appear to be efficacious. In this study we present a patient with acute myeloid leukemia who developed C. tertium bacteremia while neutropenic. Fever of unknown origin was the unique clinical feature of the infection. Mucosal ulcers, caused by chemotherapy, may be the portal of entry for C. tertium to the blood. Two sets (3 bottles per set) of blood cultures yielded C. tertium. Teicoplanin was added to the regimen and the fever resolved a few days later.