Vol

DEPARTMENT OF PATHOLOGY The Johns Hopkins Medical Institutions
Vol. 18, No. 14
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Monday, April 12, 1999

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

Outbreaks reported to DHMH for week 13 and 14 (3/28/99 - 4/12/99): 16 total

5 foodborne gastroenteritis outbreaks associated with food-service facilities/events, including 1 outbreak of confirmed Salmonella, and 2 gastroenteritis outbreaks in nursing homes
1 gastroenteritis in a nursing home
1 Clostridium difficile in a nursing home
4 foodborne gastroenteritis outbreaks associated with food-service facilities
1 pneumonia outbreak in a nursing home
1 influenza-like illness outbreaks reported in a nursing home

The Johns Hopkins Hospital. Information provided by Joseph D Kronz, M.D., Department of Pathology.

Clinical Presentation: This is a 35 year old male with HIV (CD4 count 320, viral load 367,000 copies/ml) who has a chief complaint of chronic diarrhea. The patient has intermittently taken protease inhibitors. The diarrhea has been present for several months and has been controlled with Lomotil moderate success. He was noted to have many Cryptosporidium parvum oocysts, few to moderate Entamoeba coli trophozoites and cysts, many Endolimax nana trophozoites and cysts, many Blastocystis hominis, and few Entamoeba hartmanni trophozoites on stool examination in 12/98 He was treated for the Cryptosporidium with paromomycin 750 mg t.i.d. He has now completed the course of paromomycin and currently has moderate non-bloody diarrhea that is generally well controlled for several days by taking 2-3 tablets of Lomotil per day. He denies exposure to well water. He does not camp and has not been sexually active recently. Stool examination on 4/2/99 revealed Entamoeba histolytica trophozoites and no evidence of Cryptosporidium parvum oocysts. Entamoeba histolytica

Background: Entamoeba histolytica is a common cause of diarrhea in homosexual males. E. histolytica infections are present world-wide but are common in areas with poor sanitation because the organism is spread by the oral-fecal route. Many non-pathogenic amoebae affect HIV positive individuals, these include: Entamoeba coli, Entamoeba hartmanni, Entamoeba gingivalis, Iodamoeba butschlii, and Endolimax nana. In general, only E. histolytica and rarely E. polecki are considered to cause disease in humans. Although E. histolytica has the ability to invade the colon and disseminate this rarely happens in the HIV positive population. Since E. histolytica can be a sexually transmitted disease the possibility of it being a vector for the transmission of HIV has been postulated. At least one study has demonstrated HIV in E. histolytica but the virus was unable to infect human cells after it had been taken up by E. histolytica.

Clinical Presentation: Most infections are intestinal and asymptomatic. When symptoms are present they include diarrhea, constipation, abdominal cramping and weight loss. Rarely dysentery or extraintestinal manifestations of the disease are present.

Diagnosis: The suspected diagnosis can be confirmed by stool examination. The diagnosis is established by the identification of the trophozoite which ranges in size from 10-60 um in diameter (see figure 1). E. histolytica has the ability to phagocytize red blood cells and this characteristic is useful in diagnosis. False negative results are possible due to sampling error therefore multiple stool examinations are occasionally necessary to make the diagnosis.

Therapy: Asymptomatic carriers of E. histolytica can be treated with iodoquinol, diloxanide furoate, or paromomycin. Extraintestinal infections are generally treated with metronidazole.

References:

Koneman EW, Allen SD, Janda WM, Schreckenberger PC and Winn, Jr. WC (eds). Color Atlas and Textbook of Diagnostic Microbiology. p 1082, 5^th ed. Lippincott, New York 1997.
McClatchey, KD ed. Clinical Laboratory Medicine. pp 1408-1412. 1^st ed. Williams and Wilkins, Baltimore 1994.
Chui DW, Owen RL. AIDS and the gut. J Gastroenterol Hepatol 1994 May-Jun;9(3):291-303.
Law CL, Walker J, Qassim MH. Factors associated with the detection of Entamoeba histolytica in homosexual men. Int J STD AIDS 1991 Sep-Oct;2(5):346-50.
Brown M, Reed S, Levy JA, Busch M, McKerrow JH. Detection of HIV-1 in Entamoeba histolytica without evidence of transmission to human cells. AIDS 1991 Jan;5(1):93-6.

Figure 1: Stool specimen formalin-fixed and stained with Trichrome.
Two E. histolytica trophozoites are present one of which has an "ingested"
red blood cell (arrow) indicating that it is the species E. histolytica.

Announcements:

Hepatitis Testing Changes:

Both HBAg and anti-HBs (4702) may now be ordered concurrently. Total anti-HB Core IgM + IgG (4714) is now also available and is performed weekly. 2. Streptococcus pneumoniae Antibody Testing: This low volume test will no longer be performed in-house, but will be referred to the Immunology Laboratory at SUNY (7174)

Questions about these laboratory changes may be referred to Shari Howat, Lead Technologist in the Immunology Laboratory (x5-6570).