The patient in this vignette presents with drainage from a diabetic foot ulcer suggestive of acute osteomyelitis. A common cause of acute osteomyelitis in patients with severe diabetes is Pseudomonas aeruginosa, which is also associated with external otitis.
Acute osteomyelitis is characterized by inflammatory destruction of bone and classically presents with pain, fever, drainage, erythema, and edema. The bacterial causes of acute osteomyelitis vary depending on the source of the initial infection and the patient’s comorbidities. Pseudomonas aeruginosa causes osteomyelitis in puncture wounds to the foot, in diabetic patients, and in IV drug users. It is a gram-negative, oxidase-positive, non-lactose fermenting rod. Pseudomonas aeruginosa is also associated with endocarditis (particularly in IV drug users), pneumonia (in immunocompromised patients and patients with cystic fibrosis), sepsis, ecthyma gangrenosum, external otitis (swimmer’s ear), catheter-associated urinary tract infections, corneal infections in contact lens users, and hot tub folliculitis.
Answer 2: Members of the Salmonella genus are the most common cause of osteomyelitis in patients with sickle cell disease. The second most common cause of osteomyelitis in this population is E. coli. Salmonella is a gram-negative rod that is most commonly associated with gastroenteritis.
Answer 3: Neisseria species are gram-negative diplococci that are known to cause Waterhouse-Friedrichsen syndrome, a form of fulminant meningococcemia leading to bilateral adrenal hemorrhage and widespread organ failure. Though Neisseria can also cause osteomyelitis, septic arthritis is a more common musculoskeletal manifestation, especially for Neisseria gonorrhoeae. Moreover, Neisseria are lactose-fermenting unlike Pseudomonas.
Answer 4: Streptococcus pyogenes is the second most common cause of hematogenous osteomyelitis after Staphylococcus aureus. It is also associated with pharyngitis, cellulitis, impetigo, rheumatic fever, and scarlet fever. As a gram positive cocci, it is not consistent with the findings in this case.
Answer 5: Staphylococcus aureus is the most common cause of hematogenous osteomyelitis. It is also associated with osteomyelitis in neonates and in patients with prostheses. In addition to causing osteomyelitis, S. aureus can cause toxic shock syndrome, gastroenteritis, infective endocarditis, abscesses, impetigo, staph scalded skin syndrome, pneumonia, and cellulitis. As a gram-positive cocci, it is not consistent with the findings in this case.
Pseudomonas aeruginosa is a gram-negative, oxidase-positive, non-lactose fermenting rod that causes osteomyelitis in patients with poorly controlled diabetes, IV drug users, and in puncture wounds to the foot.