The Emerging Problem of Aeromonas Infection in HIV Patients
Case Study
Note: The following case report, by Ted Louie, MD, and Richard Schwalbe, PhD, is a discussion of an emerging pathogen in the HIV-positive population. It serves to alert clinicians to the changing nature of opportunistic infections in HIV disease.jfj
A 38-year-old black male prisoner with diag-nosis of HIV infection (CD4+ count of 330/mm3) and a history of cirrhosis secondary to hepatitis C presented with a several-day history of acute onset diffuse, intermittent abdominal pain, watery diarrhea up to six episodes per day, and fever. He had no prior history of gastrointestinal disease and had not recently traveled. He was a former intravenous drug user.
Physical examination revealed a temperature of 102.6°F, blood pressure of 120/60 mmHg and a pulse of 110/min. He appeared moderately ill and was mildly jaundiced. His abdominal examination revealed decreased bowel sounds and left lower quadrant tenderness with guarding. A stool guaiac was negative.
Laboratory data revealed a white blood count of 7600/mm3 with 30% segmented neutrophils and 60% bands. The hematocrit was 31%, and the platelet count was 31,000/mm3. Chemistries were remarkable for an SGOT of 265 U/L, SGPT 109 U/L, alkaline phosphates 402 U/L, and total bilirubin 4.1 mg/dL. A chest X-ray was unremarkable, and abdominal flat and upright revealed a normal bowel gas pattern. The patient was placed on ampicillin, metronidazole, and gentamicin.
CT scan of the abdomen revealed thickening of the colonic wall consistent with colitis. Flexible sigmoidoscopy revealed edematous, erythematous distal colon and rectum. Blood cultures grew Aeromonas hydrophila. Antimicrobial susceptibilities performed by microbroth dilution (Sceptor, Becton Dickinson, Cockeysville, MD) showed the Aeromonas isolate to be susceptible to ticarcillin/clavulanic acid, imipenem/cilastatin, aztreonam, ciprofloxacin, piperacillin, cefoxitin, amikacin, ceftazidime, and trimethoprim/ sulfamethoxazole. The isolate was resistant to ampicillin and tetracycline.
Over the next three days, the patient developed progressive respiratory distress and was intubated. The antibiotics were changed to ciprofloxacin and ticarcillin-clavulanate. Bilateral infiltrates were found on his chest X-ray consistent with ARDS. He died 12 days into his hospital course.
COMMENT BY TED LOUIE, MD, and RICHARD SCHWALBE, PhD
Aeromonas species are gram-negative bacilli found in both freshwater and saltwater. They may be found in fish tanks, swimming pools, tap water, and well water. There are four species of Aeromonas, including salmonicida, sobria, caviae, and hydrophila, the last species being the most important for humans. The genus Aeromonas is facultatively anaerobic, oxidase positive, and does not form spores. They grow well on blood agar and MacConkey agar, with variable growth on the thiosulfate citrate bile sucrose medium. They ferment carbohydrates with acid and gas production. Recognition in mixed stool culture can be facilitated by the use of blood agar containing ampicillin, which inhibits other organisms. Aeromonas hydrophila is catalase-positive, motile, converts nitrate to nitrite, and is urease-negative.
Aeromonas species cause a wide breadth of disease including soft tissue infection, gastroenteritis, and bacteremia.1 These infections are more often seen in patients with malignancy, hematologic disorders, and, like our patient, liver disease. Immunocompromised patients often have no recent exposure to freshwater or saltwater. In vitro susceptibility testing of Aeromonas isolates usually reveals sensitivity patterns similar to those of the current isolate. However, mortality rates are high in the aforementioned groups even amongst those treated with appropriate antibiotics.2-6
In the USPHS/IDSA "Guidelines for the Prevention of Opportunistic Infections in Persons Infected with Human Immunodeficiency Virus: Introduction,"6 Aeromonas is mentioned as one of the bacteria that cause disease with increased frequency and/or increased severity in HIV-infected persons. We found six other reported cases of Aeromonas-related disease in HIV patients in English-language journals,7-9 our case being the second reported case of bacteremia.
Rolston et al reviewed 28 cases of Aeromonas infections, of which four were in HIV patients. All four of those patients had gastroenteritis, while one was bacteremic as well. The bacteremic patient did not have malignancy, hematologic disorder, or liver disease. CD4 counts were not included in the report. Rolston et al. reported that their HIV patients did well with antimicrobial therapy.7
Roberts described one case of an HIV-positive male with a CD4 count of 324/mm3 with acute colitis, whose stool cultures yielded Aeromonas hydrophila, and was treated successfully with trimethoprim-sulfamethoxazole.8 Subsequently, Liao described one case of an HIV patient with a CD4 count of 327/mm3 who presented with fevers and bloody diarrhea and subsequently improved on oral ciprofloxacin.9
In HIV patients, Aeromonas is a rare, potentially fatal, but often treatable cause of gastroenteritis and septicemias in the HIV population. Of the seven cases of Aeromonas disease in HIV patients, all seven had severe gastroenteritis. Two were bacteremic as well. CD4 counts were available on three patients, and all had CD4 counts greater than 300. All patients but one improved on antibiotics, while our patient was the only death. (Ted Louie, MD, is Clinical Assistant Professor of Medicine, Robert Wood Johnson Medical School, New Brunswick, NJ; Richard Schwalbe, PhD, is Director, Clinical Microbiology Laboratory, University of Maryland School of Medicine, Baltimore, MD.)
COMMENT BY JOSEPH F. JOHN, MD
Aeromonas species has historically been associated with infections in immunocompromised patients and more lately with a protracted diarrheal illness. Soft tissue infection often follows trauma with objects containing contaminated water. With the rise in the use of medicinal leeches, a new mode of infection was discovered: Aeromonas hydrophila resides normally in the foregut of the leech. The ideal choice of antimicrobial therapy remains at issue, since, as in this patient, bacteremic disease often proceeds unabated. It would have been interesting in this case to determine if the isolate produced an inducible beta-lactamase.
References
1. von Graevenitz A, Altwegg, M. Aeromonas and Pleisomonas. in: Balows A, et al. eds. Manual of Clinical Microbiology, 5th ed. Washington, DC: American Society for Microbiology; 1991:396-401.
2. Davis WA, et al. Medicine 1978;57:267-277.
3. Harris RL, et al. Rev Infect Dis 1985;7:314-320.
4. Gold WL, Salit IE. Clin Infect Dis 1993;16:69-74.
5. Cordingley FT, Rajanayagam A. Med J Aust 1981; 1:364-365.
6. Kaplan JE, et al. Clin Infect Dis 1995;21(suppl 1):S1-11.
7. Rolston KVI, et al. Experientia 1991;47:437-439.
8. Roberts IM, et al. Arch Intern Med 1987;147:1502-1503.
9. Liao EC, Cappell MS. J Clin Gastroenterol 1989; 11:552-554.
Recommended Reading
Fass RJ. Antimicrob Agents Chemother 1980;18:483-486.
Overman TL. Antimicrob Agents Chemother 1980;17: 612-614.
Fass RJ, Barnishan J. Antimicrob Agents Chemother 1981;19:357-358.
Fainstein V, et al. Antimicrob Agents Chemother 1982;22:513-514.
Gowan JE, Steinberg JP. Other gram-negative bacilli. In: Mandell GL, Bennett JE, Dolin R (eds). Principles and Practice of Infectious Diseases, 4th edition. New York: Churchill Livingstone; 1995:2107-2111.
Wolff RL, et al. Am J Med 1980;68:238-242.
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