| Case History A 63 year old man was seen in the emergency room with the complaints of sudden onset of fever, chills, and abdominal pain, accompanied by mild diarrhea. The blood pressure was 140/84, the pulse rate 82/minute, and the body temperature 39.8C. A blood sample was drawn for a complete blood count, and a blood culture.A second blood culture was drawn from the opposite arm, with 10 ml of blood being placed into each an aerobic and an anaerobic bottle, following customary practice.The complete blood count revealed a hemoglobin of 15.8 mg/dl, a hematocrit of 45%, and a white blood count of 4.2/L. The neutrophils were 39%, lymphocytes 45%, monocytes 10%, eosinophils 4% and basophils 2%. The platelet count was 255/L. The patient was admitted to the hospital for further work-up and empiric antibiotic therapy.Within 24 hours after admission, the body temperature had decreased to 38.2C, although the mild diarrhea persisted.A stool toxin test for Clostridium difficile was negative and neither enteric pathogens nor Campylobacter species were recovered in stool culture after 24 hours incubation. Fecal neutrophils were not seen on direct examination.
The anaerobic blood culture became positive 36 hours after inoculation. | View Page |
| Colony Morphology The growth observed on the anaerobic blood agar plate after 48 hours incubation (see upper photograph), revealed a spreading colony. The spreading nature of the colony is better observed in the close-in photograph (lower). 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. | View Page |
| Review 2 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, 1993Identification 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). | View Page |
| Review 2 Griego RD. Rosen T. Orengo IF. Wolf JE.:
Dog, cat, and human bites: a review.
Journal of the American Academy of Dermatology. 33:1019-29, 1995It is estimated that half of all Americans will be bitten by an animal or another human being during their lifetimes. The vast majority of the estimated 2 million annual mammalian bite wounds are minor, and the victims never seek medical attention. Nonetheless, bite wounds account for approximately 1% of all emergency department visits and more than $30 million in annual health care costs.Infection is the most common bite-associated complication; the relative risk is determined by the species of the inflicting animal, bite location, host factors, and local wound care. Most infections caused by mammalian bites are polymicrobial, with mixed aerobic and anaerobic species.The clinical presentation and appropriate treatment of infected bite wounds vary according to the causative organisms. Human bite wounds have long had a bad reputation for severe infection and frequent complication. However, recent data demonstrate that human bites occurring anywhere other than the hand present no more of a risk for infection than any other type of mammalian bite.The increased incidence of serious infections and complications associated with human bites to the hand warrants their consideration and management in three different categories: occlusional/simple, clenched fist injuries, and occlusional bites to the hand. This article reviews dogs, cat, and human bite wounds, risk factors for complications, evaluation components, bacteriology, antimicrobial susceptibility patterns, and recommended treatments. Epidemiology, clinical presentation, and treatment of infections caused by Pasteurella multocida, Capnocytophaga canimorsus, Eikenella corrodens, and rhabdovirus (rabies only) receive particular emphasis.
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