Bacillus cereus is a Gram-positive, facultative anaerobic, spore- and toxin-forming bacterium that causes acute, self-limited food-borne gastroenteritis. However, in immunocompromised patients it may behave as a virulent pathogen, causing bacteremia, pneumonia and, more rarely, necrotizing fasciitis, meningitis, endocarditis, endophthalmitis, and peritonitis.

A 59-year-old male patient with hypertension, liver transplant in 2017 due to hemangioendothelioma, evolved with cirrhosis of the graft and required retransplantation (MELD-Na 37). On mycophenolate mofetil and prednisone, he was admitted due to decompensated cirrhosis with encephalopathy and jaundice, progressing with severe liver dysfunction, symptomatic acute hyponatremia and hyperkalemia. On the 11th day of hospitalization, he developed nausea, anorexia, diarrhea, and low back pain. Subsequently, he presented with intense pain, warmth, edema and erythema in the right upper limb, along with a large hemorrhagic blister on its medial surface. There was no history of recent local trauma. Aspirative puncture of the blister, blood cultures and paracentesis were performed, with samples sent for culture for common germs and fungi. Rapidly and progressively, he evolved with hemodynamic instability refractory to fluid resuscitation and requiring vasopressors, metabolic acidosis, worsening inflammatory parameters and renal function. Invasive ventilatory support was required due to decreased level of consciousness and respiratory failure. Empirical meropenem and vancomycin were started, with suspension of immunosuppressants. Blood cultures, ascitic fluid and blister cultures showed Gram-positive rods, isolating Bacillus cereus sensitive to vancomycin. The patient died 48 hours after starting treatment.

B. cereus is considered a saprophytic microorganism of the gastrointestinal tract of healthy individuals and traditionally regarded as of low virulence. Invasive disease is associated with immunocompromised patients, and spontaneous bacterial peritonitis and necrotizing fasciitis are rare manifestations. Patients with liver cirrhosis are particularly susceptible to this agent, which should be included among possible etiologic agents when Gram-positive bacilli are identified in clinical specimens.