Vibrio vulnificus is a curved, gram-negative, free-living bacterium that grows in brackish coastal water and marine environments.  This bacterium is found in greatest concentrations in the summer months, comprising as much as 8% of the total bacteria in some areas.  V vulnificus infections are primarily acquired through the consumption of raw oysters (which concentrate the bacterium) or wound contamination during recreational water activities or the handling of raw seafood.  Most patients who become ill have liver disease (eg, alcohol-associated cirrhosis, viral hepatitis); those with iron overload (eg, hemochromatosis) are at particularly high risk as free iron acts as an exponential growth catalyst for the bacterium.

Healthy patients with V vulnificus wound contamination usually develop a mild cellulitis, but those with iron overload or liver disease are at high risk for rapidly progressive necrotizing fasciitis with hemorrhagic, bullous lesions and septic shock (eg, hypotension, elevated lactic acid level).  In these patients, urgent antibiotics, surgery, and blood pressure support are usually required to prevent death.

(Choice A)  Staphylococcus aureus colonizes the nasopharynx and is a leading cause of skin/soft-tissue abscess.  However, S aureus is a catalase-positive, gram-positive bacterium.

(Choice C)  Leptospira species are highly motile, gram-negative spirochetes that are often transmitted via contaminated rat urine.  Leptospirosis is often mild or asymptomatic but may cause fever, myalgia, headache, multiorgan failure, or death.  This patient who developed symptoms after a sustaining a wound while boating is more likely to have a V vulnificus infection.

(Choice D)  Clostridium tetani is an anaerobic, gram-positive, spore-forming rod-shaped bacterium that can inoculate wounds contaminated with soil.  It elaborates an exotoxin (tetanus toxin) that disinhibits anterior horn cells and results in painful muscle contractions, lock-jaw, and difficulty swallowing.

(Choice E)  Clostridium difficile is most common in individuals who have recently taken broad-spectrum antibiotics, which disrupts gastrointestinal flora and allows the organism to proliferate.  Patients usually develop diarrhea, fever, and abdominal pain.

Educational objective:
Vibrio vulnificus is a curved, gram-negative, free-living bacterium that grows in marine environments.  Transmission primarily occurs due to the consumption of raw seafood (eg, oysters) or wound contamination.  Manifestations are often mild, but individuals with liver disease or iron overload are at very high risk of severe, fulminant infection (eg, sepsis, necrotizing fascitis).