The Uninvited Guest: Aeromonas Diarrhea

Abstract

Case: A 74-year-old woman from rural Pennsylvania with rheumatoid arthritis on leflunomide and latent tuberculosis infection on isoniazid presented after experiencing 1 week of extreme fatigue, confusion, fever, and watery diarrhea. Patient was ill-appearing, septic, and hypotensive on presentation. Urinalysis and chest x-ray did not reveal a source of infection. Testing for Clostridium difficile was negative. Despite treatment with ceftriaxone and azithromycin, she continued to have diarrhea, leukocytosis, and fever. On day five of hospitalization, stool cultures revealed Aeromonas hydrophila (A. hydrophila). The patient was started on levofloxacin and she started to clinically improve over the next 2 days. Evidence: The relative frequency of A. hydrophila in the United States causing diarrhea is unknown. While A. hydrophila has been known to cause intestinal and extraintestinal infections, it is still not universally accepted as a cause of gastroenteritis. Reasons for Presentation: The presence of A. hydrophila in stools of individuals with diarrhea, in the absence of other pathogens, supports its role in gastroenteritis. Most microbiology laboratories do not include A. hydrophila as part of the standard protocol for identifying stool pathogens. This presentation highlights the importance of seeking less common causes of diarrhea. Conclusions: While A. hydrophila is mainly a non-inflammatory agent of diarrhea in healthy patients, more cases of invasive disease in immunocompromised patients are being reported. Microbiology laboratories must be advised to look for the organism when more common causes of diarrhea are ruled out. With increasing resistance to Aeromonas species, antimicrobial susceptibility testing is needed to insure adequate treatment. The uniqueness of this case illustrates the fact that maintaining the suspicion for rare diseases may assist in the diagnosis and treatment of complex patients.