A 35-year-old man is admitted to the hospital after he fell off a moving tractor and caught his right leg underneath the vehicle. The patient has no past medical history. Over the next few hours, he develops worsening severe pain and rapidly increasing swelling in the injured right leg. Crepitus is present on physical examination. Emergent radiographic imaging reveals gas in the tissues. Surgical evaluation is performed. The microorganism most likely responsible for this patient's condition is also commonly associated with which of the following conditions?

Question

A 35-year-old man is admitted to the hospital after he fell off a moving tractor and caught his right leg underneath the vehicle.  The patient has no past medical history.  Over the next few hours, he develops worsening severe pain and rapidly increasing swelling in the injured right leg.  Crepitus is present on physical examination.  Emergent radiographic imaging reveals gas in the tissues.  Surgical evaluation is performed.  The microorganism most likely responsible for this patient's condition is also commonly associated with which of the following conditions?

Quizplus · Accepted Answer

Spores of Clostridium perfringens, a gram-positive bacillus responsible for ~95% of cases of gas gangrene (clostridial myonecrosis), are abundant in soil and can inoculate penetrating injury sites. On entering the host, the spores germinate in the anaerobic environment into vegetative cells, which produce a phospholipase toxin that attacks cell membranes. Extensive tissue damage, necrosis, and reduced blood supply to the affected area result, with the disease spreading in the enlarging anaerobic environment. The organism rapidly metabolizes carbohydrates, producing gas that can sometimes be felt on examination (crepitus) and may often be visualized on radiographs (helping to distinguish gas gangrene from other necrotizing infections). Treatment involves antibiotics and emergent debridement. However, prognosis is poor even with prompt therapy, and tissue loss is often considerable. C perfringens can also cause late-onset food poisoning that is characterized by transient watery diarrhea. This gastroenteritis is caused by a toxin formed when large quantities of clostridial spores are ingested. The spores germinate in the digestive tract and then begin to elaborate toxin, which explains the disease's delayed onset. This is in contrast to early-onset food poisoning caused by the preformed toxins of Staphylococcus aureus and Bacillus cereus. (Choices A and B) C perfringens does not cause cough. It is also an extremely rare cause of endocarditis and valve abscess. (Choice C) Relentless headaches and nausea can be caused by any organism that causes meningitis. Subacute or chronic infections causing these illnesses include Mycobacterium tuberculosis, Acanthamoeba, and Cryptococcus neoformans. (Choice E) Urinary frequency and burning are caused by urethritis/cystitis. The urethritis of urinary tract infections is usually due to Escherichia coli, whereas sexually transmitted types of urethritis can be due to gonorrhea, chlamydia, and Ureaplasma urealyticum. C perfringens does not cause dysuria. Educational objective: Clostridium perfringens causes late-onset food poisoning and clostridial myonecrosis (gas gangrene). The food poisoning is toxin-mediated, late-onset, and causes transient watery diarrhea.

A 35-Year-Old Man Is Admitted to the Hospital After He