Contributed by Hannah Kastenbaum, MD and William Pasculle, ScD
A 77 year-old male with a history of atrial fibrillation, hypertension, hyperlipidemia, and gastroesophageal reflux presented to the Emergency Department with complaints of two days of copious watery diarrhea. He admitted to anorexia, but denied abdominal pain or cramping, nausea, fever, and blood or mucus in the stool. He had not recently taken any antibiotics and his maintenance medications included warfarin, metoprolol, hydrochlorothiazide, atorvastatin, and pantoprazole.
The patient had a recent travel history including one week in San Francisco, a weekend visiting family and a grandchild in daycare, and a week of boating in the Chesapeake Bay. During the boat trip the patient and other travelers consumed raw oysters. Approximately 24 hours after returning from the trip, the patient developed symptoms. Of the patient's traveling companions in Chesapeake, some but not all reported similar ailments.
Upon examination, the patient had a temperature of 36.7 C, irregularly irregular pulse of 112 beats per minute, respiratory rate of 16 breaths per minute, and blood pressure of 132/80 mmHg. Mucous membranes were tacky. His abdomen was soft and non- tender, and without rebound, guarding, or flank pain. Initial laboratory evaluation revealed a white blood cell count of 9.1x 10^9 per L with a slight left shift of 83% neutrophils.
The patient's stool was positive for occult blood and negative for Clostridium difficile toxin and ova and parasites. Moderate white blood cells were present. Two different types of colonies grew from the patient's stool culture on a CAMPY blood agar plate (Figure 1).
Organism 1 grew in smooth, creamy, gray-white, beta-hemolytic colonies. Gram stain (Figure 2) showed curved gram negative bacilli. The organism was strongly oxidase positive (Figure 3). Figure 4 shows the Triple Sugar Iron, Citrate, and Indole tube biochemical results. Figure 5 demonstrates growth of the organism in 1% NaCl media. Figure 6 shows results of the arginine, lysine, and ornithine decarboxylase biochemical tests. Figure 7 shows a TCBS (thiosulfate, citrate, bile, sucrose) plate streaked for comparison with Escherichia coli and Klebsiella pneumoniae. Figure 8 shows a TCBS plate with blue-green colonies of Organism 1. Figure 9 shows a confirmatory API-20E biochemical strip. Figure 10 shows the Kirby-Bauer sensitivity testing of Organism 1 on a Mueller-Hinton agar plate.
Organism 2 was identified as small gray, non-hemolytic, flat, and slightly mucoid colonies on Campy agar at 42°C (see Figure 11). Gram stain revealed curved weakly-staining gram-negative rods with a 'gull-wing' shape (Figure 12). Rapid catalase and oxidase tests were positive. The rapid Hippurate test is shown in Figure 13.