Amoebas
A team led by microbiologist Sharon Berk, of Tennessee Technological University in Cookeville, fed lab-grown bacterial
pathogens to protozoa found on grocery store produce. Her team did not find the pathogenic
bacteria on the supermarket veggies. When Berk's team then examined the protozoa, they discovered the bacteria
alive and well in their stomachs.
Apparently the pathogens upset the protozoa's digestion, though. A day after mixing E. coli O157:H7 and Salmonella
with protozoa, the team noticed that many of the bacteria had been "vomited" up into round clumps.
22. Entamoeba histolyca, ---------------------------- Amebic dysentery
enteric amebiasis, amebic colitis, amebic liver abscess, hepatic amebiasis, pleuropulmonary amebiasis, cerebral
amebiasis, Entamoeba histolytica, E histolytica
Amebiasis is an infection caused by the protozoal organism Entamoeba histolytica and includes amebic colitis and liver
abscess.
the parasite does not kill the host cell but rather induces its self-destruction.
E histolytica probably is second only to malaria as a protozoal cause of death. The prevalence of amebic colitis and liver
abscess is estimated at 40-50 million cases annually worldwide, resulting in 40,000-110,000 deaths.
Asymptomatic intestinal infection occurs in 90-99% of infected individuals. Most infected individuals eliminate the
parasite from the gut within 12 months; however, colonization with E histolytica carries a low but definite risk of
developing into invasive amebiasis.
Uncommon manifestations include ameboma, fulminant colitis, and rectovaginal fistulas.
Case fatality rates of amebic colitis range from 1.9-9.1%. Amebic colitis is complicated by fulminant or necrotizing colitis
in approximately 0.5% of cases, with a resultant mortality rate of greater than 40%.
Amebic liver abscess is complicated by intraperitoneal rupture in 2-7% of patients, with sudden perforation causing a
high mortality rate.
Young children appear to be at higher risk for fulminant invasive disease, resulting in a higher mortality rate.
Pleuropulmonary amebiasis
This condition is a rare but serious complication of amebic liver abscess, usually caused by rupture of a superior right
upper lobe abscess with erosion through the diaphragm.
Patients with this complication present with cough, pleuritic chest pain, dyspnea, and, occasionally, necrotic sputum.
Intraperitoneal rupture of amebic liver abscess occurs in 2-7% of patients. These patients can present with a rigid
abdomen that may be diagnosed erroneously as a perforated viscus.
Cerebral amebiasis is a rare cause of brain abscess and is characterized by an abrupt onset of mental status change
and/or focal neurologic deficits. Progression to death occurs over 12-72 hours without adequate therapy.
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