Vol. 18, No. 9
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Monday, March 8, 1999
 

1. Provided by Leslie Edwards Reger, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.

4 influenza-like illness outbreaks in nursing homes
1 lab confirmed outbreak of influenza A in a nursing home
1 gastroenteritis/rotavirus outbreak in a hospital
1 foodborne gastroenteritis outbreak reported from a food-service facility
7 total outbreaks reported to DHMH from 3/1 - 3/7

20 ILI outbreaks in nursing homes
3 gastroenteritis outbreaks reported in nursing homes
4 outbreaks of foodborne gastroenteritis associated with food service = facilities
27 total outbreaks reported to DHMH from 2/22 - 2/26
 

Clinical Presentation: A 41 year old Haitian female with a history of HIV (CD4 count 48) and chronic renal insufficiency presented with 2 weeks of progressive weakness, dizziness, postprandial nausea, vomiting, abdominal pain, and persistent watery diarrhea. She described a 40 lb. weight loss over the course of 4 months with a considerably diminished appetite. She also described being amenorrheic for the past 8 months. She immigrated to the United States from Haiti in 1989 and has worked as a housekeeper in a hotel. Admission physical exam was remarkable for a mild fever and normal abdominal examination. Laboratory studies on admission were notable for a white count of 6.9K and a hematocrit of 21.4 percent. A CT of the abdomen was obtained which was suggestive of enteritis. A stool specimen was sent to the laboratory and Isospora belli oocytes were identified.  A diagnosis of Isospora enterocolitis was made and the patient was started on trimethoprim/ sulfamethoxazole. The diarrhea improved and the patient was discharged on trimethoprim/ sulfamethoxazole therapy.

Isospora belli

History: Isospora was first described by Virchow in 1860 but was not named until 1923. Isospora is a member of the Coccidia subclass in the family Eimeria , which also includes other medically important organisms such as Plasmodium species, Toxoplasma gondii, Cryptosporidium species, and Cyclospora species. Isospora belli can be transmitted directly from human to human via fecal contaminated food or water and therefore is not a zoonosis. The organism is known to infect animals and is endemic in certain tropical areas of the Western Hemisphere.

Clinical Presentation: Isospora belli infection is most frequent in the immunocompromised patient and can cause disease in both adults and children. The typical patient is HIV-positive and presents with watery, fowl smelling diarrhea, anorexia, fever, weakness and weight loss. These manifestations can last from days to years with chronicity being directly related to the degree of immunosuppression present in the host. Cryptosporidiosis can have a similar clinical presentation but should be differentiated because Isospora can be effectively treated with antibiotics.

Diagnosis: The diagnosis of Isospora belli is made by examination of the stool and/or biopsy of the duodenum. In the stool Isospora oocyts are recognized as oval and long measuring approximately 15 mm by 26 mm. The oocytes have thin smooth walls and are nonmotile. Immature oocysts contain only one sporocyst; however, the predominant form found in the stool is the mature oocyst which contains two sporocysts. The oocytes can be stained with an acid-fast stain and easily visualized in stool if adequate numbers are present (see image 3). Isospora also takes up the florescent dyes auramine or rhodamine and can be visualized with florescent microscopy (see image 1). The diagnosis can also be established by duodenal biopsy (see image 2). In tissue sections Isospora is an intracellular organism present in the surface enterocytes. It is possible to have a positive tissue biopsy and not recover the organism in the stool due to the small number of organisms shed in certain cases.

Therapy: Trimethoprim-sufamethoxazole is the standard therapy and usually leads to rapid improvement in symptoms. Although a cure can be obtained using antibiotics, severely immunocompromised patients are at increased risk for recurrence and maintenance antibiotics are usually indicated.

References:

1. Koneman EW, Allen SD, Janda WM, Schreckenberger PC and Winn, Jr. WC (eds). Color Atlas and Textbook of Diagnostic Microbiology. pp 1096-97, 5^th ed. Lippincott, New York 1997.
2. Garcia LS and Bruckner DA. Diagnostic Medical Parasitology. Pp 69-72, 3^rd ed. ASM Press, Washington, D.C. 1997.
3. Soave R. Cryptosporidiosis and isosporiasis in patients with AIDS. Infect Dis Clin North Am 1988 Jun;2(2):485-93.
4. Lindsay DS, Dubey JP, Blagburn BL. Biology of Isospora spp. from humans, nonhuman primates, and domestic animals. Clin Microbiol Rev 1997 Jan;10(1):19-34.

Image 2: Small Bowel Biopsy (Isospora belli arrows)

Image 3:  Stool stained with acid-fast stain.

Effective immediately, stool specimens for ova and parasite examination (O&P) collected from patients who have been hospitalized for more than three days will not be accepted by the Parasitology Laboratory. It is imperative that all specimens for ova and parasite examination sent for testing during the first three days of hospitalization.

Some of the reasons for this change are as follows:

There are certain substances and medication that interfere with the detection of intestinal protozoa: antibiotics, mineral oil, bismuth, antimalarial agents and non-absorbable antidiarrheal preparations. After administration of any of these compounds, parasitic organisms may not be recovered for a week to several weeks. Commonly used substances like barium and antibiotics such as tetracycline may modify the GI tract flora and will diminish the number of protozoa since they feed on intestinal bacteria. It is not likely that patients will be infected by parasites during lengthy hospital stays.

However, stool specimens for Cryptosporidium and/or Microsporidium stains and for Giardia ELISA will continue to be accepted when indicated during hospitalization.