|Gas gangrene may be seen in infections with all the following clostridia EXCEPT:||View Page|
|The Gram stain shown in the image was prepared from a positive anaerobic blood culture bottle after 36 hours incubation. Based on the morphology of the bacterial cells (some with spores, noted by the blue arrows), what the most likely identification?||View Page|
The growth observed on the anaerobic blood agar plate after 48 hours incubation (see upper image), revealed a spreading colony. The spreading nature of the colony is better observed in the lower image. No growth was observed on subcultures incubated aerobically indicating that this isolate is truly an anaerobe (although aerotolerance studies would be needed for confirmation). The spreading nature of the colony and the lack of hemolysis are highly suggestive of Clostridium septicum. However, biochemical confirmation is necessary.
|Clostridium Quad Plate|
Key reactions for the identification of Clostridium septicum are demonstrated in the two quadrant plates shown in the images to the right. Included in the upper image are reactions for milk (casein) proteolysis (12 o'clock quadrant), glucose fermentation, DNAse hydrolysis, and starch hydrolysis respectively reading clockwise. The media in the quadrant plate shown in the lower image include gelatin hydrolysis (2 o'clock quadrant) and fermentation of each of mannitol, lactose, and rhamnose respectively, reading clockwise. Milk (casein) hydrolysis and glucose fermentation are key reactions for the identification in the upper plate, including no proteolysis of milk, fermentation of glucose (yellow red color along the inoculation streak), positive DNAse (reddish clearing around the streak) ,and a negative reaction for starch. Key reactions in the lower plate include hydrolysis of gelatin, fermentation of lactose (yellow pigment), and negative reactions for mannitol and rhamnose (no pigment). Most strains of C. perfringens hydrolyze starch and produce proteolysins of milk, the key reactions that distinguish C. septicum (negative). Reactions to the other tests do not distinguish between the two.
|Clostridium septicum RapID ANA|
The definitive identification of C. septicum can be made using a profile of biochemical reactions, as is contained in the RapID ANA strip seen in the image. The upper set of tubules are reactions before addition of reagents; the bottom set of reactions after reagents are added. The upper set of letter codes is used to read the reactions before addition of reagents; the lower set of labels indicate the tests to read following addition of reagents. Of all the reactions included, only ONPG and NAG in the upper set are positive. The biotype number derived from this profile of reactions, 014000 codes for Clostridium septicum, thus confirming the identification.
|It is important to establish a species identification of C. septicum in blood culture isolates because of its close association with carcinoma of the colon.||View Page|
Lorimer JW. Eidus LB.: Invasive Clostridium septicum infection in association with colorectal carcinoma. Canadian Journal of Surgery. 37:245-9, 1994 The association between invasive Clostridium septicum infection and colorectal carcinoma is examined by the presentation of three cases and a review of the literature. In the first two cases the patients presented with nontraumatic metastatic clostridial gas gangrene. In the third case a patient with chemotherapy-induced myelosuppression from concomitant multiple myeloma had a necrotizing transmural infection of the right colon. The apparent portal of entry of Clostridium septicum was an occult carcinoma of the ascending colon. The increasing evidence for a strong link between this organism and some cases of neutropenic enterocolitis is reviewed.
Citron DM. Appelbaum PC.: How far should a clinical laboratory go in identifying anaerobic isolates, and who should pay? Clinical Infectious Diseases. 16 Suppl 4:S435-8, 1993 Identification of anaerobic bacteria in specimens from sites of infection due to mixed organisms can be time-consuming and expensive. Laboratories should limit anaerobic workups by testing only those specimens that have been properly collected and transported to the laboratory. Use of selective and differential media for initial processing can provide rapid and relevant information to the clinician. Anaerobes isolated from normally sterile sites and sites of serious infection should always be completely identified. Group-or genus-level identifications may suffice in other instances. The Bacteroides fragilis group of organisms should always be identified because of their virulence and resistance to many antimicrobial agents. Some of the other organisms that warrant identification include Clostridium septicum (associated with gastrointestinal malignancy); Clostridium ramosum, Clostridium innocuum, and Clostridium clostridioforme (which are resistant to antibiotics); Clostridium perfringens (a cause of myonecrosis and gas gangrene,potentially serious infection); anaerobic cocci (which may be resistant to metronidazole and clindamycin); and fusobacteria (which may be virulent and resistant to clindamycin and penicillin).
Kornbluth AA. Danzig JB. Bernstein LH.: Clostridium septicum infection and associated malignancy. Report of 2 cases and review of the literature. Medicine. 68(1):30-7, 1989 We report 2 patients with myonecrosis due to Clostridium septicum and associated colon carcinoma and have reviewed the English language literature for all reported cases of atraumatic C. septicum infection. A total of 162 cases of C. septicum infection have been reported. Eighty-one percent of these patients had an associated malignancy. Thirty-four percent of all patients had associated colon carcinoma, while 40% had a hematologic malignancy. Thirty-seven percent of reported patients had an occult malignancy at the time of their infection with C. septicum. In many patients, the portal of entry was found in the large intestine. In a particularly lethal form (79% mortality) of C. septicum infection, known as "distant myonecrosis," infection metastatic from the initial site of infection causes severe myonecrosis, gangrene, and often death within hours of clinical detection. Overall, survival of patients with C. septicum infection is only 35%. Review of all cases of C. septicum infection suggests several conclusions. 1) Patients with malignancy, particularly colonic or hematologic, and patients with cyclic neutropenia who develop signs and symptoms of sepsis, especially with associated findings of abdominal pain or pain in an extremity, should be treated for possible clostridial infection. 2) C. septicum infection does not appear to be a result of a single specific defect in either humoral or cell-mediated immunity. Rather, it may occur in patients who are granulocytopenic and therefore prone to an enterocolitis. 3) Patients in whom an infection with C. septicum is found must undergo a vigorous search for malignancy.
|Match the species of anaerobes and frequently associated conditions.||View Page|
|Each of the following statements is true concerning Clostridium septicum infections EXCEPT:||View Page|
|A Brown and Brenn gram stain was performed on one of the tissue biopsy specimens. Organisms were seen as shown in the image. Based on the history and the appearance of the bacteria, the most likely identification is:||View Page|