An interesting feature peculiar to some of the Yersinia bacteria is the ability not only to survive, but also to proliferate at temperatures as low as 1-4 degrees Celsius (e.g., on cut salads and other food products in a refrigerator). Yersinia representatives also reveal relatively high heat resistantance, some of them being able to survive 50-60 degrees Celsius temperature for up to 20-30 minutes and (arguably, might be due to misreading of information like the first external link below) surviving standard pasteurization process (15 seconds at 72 degrees Celsius) in milk. Yersinia bacteria are relatively quickly inactivated by oxidizing agents such as hydrogen peroxide and potassium permanganate solutions.
Y. enterocolitica is a relatively infrequent cause of diarrhea and abdominal pain. Infection is most often acquired by eating contaminated food, especially raw or undercooked pork products, as well as ice-cream and milk. Common symptoms are fever, abdominal pain, and diarrhea, which is often bloody.
Yersinia pseudotuberculosis: An infectious disease caused by a bacterium called Yersinia pseudotuberculosis which is transmitted from direct and indirect contact with infected animals. Human to human transmission may also occur through fecal-oral contact.
[ edit ] Pathogenesis
E.histolytica is an invasive protozoal organism capable of causing life-threatening intestinal and extra-intestinal disease. E.histolytica can invade the liver, lung and other bodily sites by penetrating the intestinal mucosal barrier.
It has a worldwide distribution and is the third leading cause of death by parasitic infection. It was first documented in 1875 and is estimated to cause between 50,000 and 100,000 deaths every year. Ninety percent of those infected have no symptoms.
Symptoms range from mild diarrhoea to hemorrhagic dysentery.
Cases of mild diarrhoea caused by E.histo. are often misdiagnosed as Irritable Bowel Syndrome.
Many infected individuals are asymptomatic but can infect others via intermittent shedding of cysts in the stool.
Symptoms may include:
Fever (in approx. 10-30% of patients)
Tenesmus (straining to pass stool, a feeling of imco mplete evacuation)
Abdo. pain, including tenderness.
Stools which are loose, watery.
Passing of blood, mucous
including necrotising (fulminant) colitis (approx. 0.5% of patients) which has a mortality rate of 40%. Nectrotising colitis can occur in the malnourished, during corticosteroid use (steroids used to suppress inflammatory response), in young children & during pregnancy.
Upper quadrant abdo. pain and fever.
A prior history of dysentery
Individuals with liver abscess may not excrete the organism in the stool, in these cases stool antigen tests may not be suitable for the diagnoses of amoebic liver abscess.
Although blood tests for antibodies against E histolytica are approx. 80% accurate, the detection rate drops dramatically after treatment with metrondazole. In one study of 75 patients all positive for amoebic liver abscess, only 15% tested positive after treatment with metronidazole (Flagyl). ( J Clin Microbiol. 2000;38:3235-3239) .
"Genital amebiasis is a rare complication of infection with Entamoeba histolytica, even in areas where the pathogen is endemic. We describe a patient who apparently contracted intestinal amebiasis on a trip to Mexico and who presented with ulcerative vulvovaginitis 2 months later. Her condition rapidly progressed to severe necrotizing vulvovaginitis that required a radical vulvectomy. Histopathologic examination of the surgical specimen revealed the presence of E. histolytica trophozoites. The patient recovered after surgery and antiamebic therapy."
Clin Infect Dis 1995 Mar;20(3):700-2
Severe vaginal infection with Entamoeba histolytica in a woman who recently returned from Mexico: case report and review.
Citronberg RJ, Semel JD. Section of Infectious Disease,
Rush Medical College, Chicago, Illinois, USA.
Exposure to E.histolytica cysts is simialr to that of D.fragilis and B.hominis:
Contaminated water and food - spread by direct contact with an infected person's hands or with contaminated surfaces.
Consuming food grown in feces-contaminated soil, fertilizer, or water.
E.histolytica cysts can survive for weeks under moist conditions.
Swimming pools are a possible source of contamination because E.histo. survives chlorine levels sufficient to kill bacteria.
Examination of a single stool specimen is approx. 33% accurate.
Because the cysts of E.histolytica shed intermittently in the stool and may not be present at the time of testing. At least three to six stool examinations are recommended (read individual experiences here .
" Over the years I've tested positive for Giardia, B. Hominis, E. Nana, many different species of yeast and bacteria. On my last test, E. Histolytica turned up. I've had no fewer than ten stool tests by very reputable labs (Diagnos-Techs, Great Smokies) and this is the first time E. Histolytica has shown up."
C. April 2003
The following may interfere with the recovery of the parasite and should be avoided for 3 weeks prior to submitting samples for testing. Discuss with your doctor before stopping any medications.
Tetracyclines, sulfonamides, antiprotozoal agents, laxatives, antacids, castor oil, magnesium hydroxide, barium sulphate, bismuth kaolin compounds and hypertonic salts, anti-parasitic herbs, certain laxatives & mineral compounds, antibiotics, antacids, antidiarrheals.
STOOL TESTING BY ELISA (Enzyme-Linked Immunosorbent Assay):
Parasites are composed of cell surface molecules called lectins, which enable the parasite to adhere to the bowel. ELISA detects the lectins specific to E.histolytica and is performed on fresh, unfixed samples.
The labs on the "Where to find help/labs " section of this site use ELISA & other antibody tests to detect E.histolytica.
"The appearance of amebic colitis may resemble that of inflammatory bowel disease, with a friable and diffusely ulcerated mucosa. In addition, an ameboma may be present in the form of an annular lesion, which usually occurs in the cecum and ascending colon and often is visually indistinguishable from colonic carcinoma". (Robert Swords, MD. Feb 2002)
"In a small pilot study the parasite cure rate (PCR) of non-invasive amoebiasis was compared after treatment with metronidazole 800 mg three times daily or tinidazole 600 mg twice daily for five days. Both treatment regimens were found to be highly unfavourable with PCRs of 44 and nil respectively, in contrast to previous published results showing PCR over 80%".
Treatment of non-invasive amoebiasis--a comparison between tinidazole and metronidazole.
Pehrson P, Bengtsson E. Ann Trop Med Parasitol 1984 Oct;78(5):505-8
One hundred and fifteen persons with asymptomatic Entamoeba histolytica or E. hartmanni infection, or both, were given metronidazole (750 mg three times daily for 5 days), tinidazole (1 g twice daily on 2 consecutive days), or a starch placebo. Three post-treatment stools were examined in the 2 weeks following initiation of treatment. Cysts of E. histolytica reappeared in the stools of 37% of 30 given metronidazole, 62% of 34 given tinidazole, and 70% of 31 given placebo. Cysts of E. hartmanni reappeared in the stools of 46% of 24 given metronidazole, 69% of 16 given tinidazole, and 90% of 10 given placebo. Rapid absorption and short duration of treatment make both drugs ineffective for the treatment of ameba carriers.
Double-blind test of metronidazole and tinidazole in the treatment of asymptomatic Entamoeba histolytica and Entamoeba hartmanni carriers. Spillmann R, AyalaSC, Sanchez CE. Am J Trop Med Hyg. 1976 Jul;25(4):549-51.
Unique in that it is effective both in the bowel lumen and in tissues, metronidazole has been reported to eradicate only up to 50% of luminal** infections. This statement has support from a study of 36 patients with amoebic liver abscess for whom the hepatic lesions were cleared; but 20 were recolonized in the intestine, 16 asymptomatically. This was ascribed to the pharmacokinetics of metronidazole cycling in the liver and the action of metronidazole against trophozoites but not invariable eradication of cysts, creating E. histolytica carrier states.
Current recommendations suggest the use of metronidazole or tinidazole PLUS the luminal amoebicide diloxanide furoate or iodoquinol, with other combinations (including paromomycin, tetracycline, and chloroquine) depending on the severity of the infection and site, i.e., whether it is intraluminal, invasive, or abscessed .
Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa
Peter Upcroft* and Jacqueline A. Upcroft
Queensland Institute of Medical Research and The Tropical Health Program, Australia
Some therapeutic failures with metronidazole in patients with invader amebiasis and some reports of resistance to it.
In vitro sensitivity of Entamoeba histolytica to metronidazole. Aguirre-Cruz ML, Valadez-Salazar A, Munoz O.
Arch Invest Med (Mex). 1990;21 Suppl 1:23-6
Nitazoxanide was more toxic than
metronidazole and albendazole against E. histolytica
In vitro effect of nitazoxanide against Entamoeba histolytica , Giardia intestinalis and Trichomonas vaginalis trophozoites.
J Eukaryot Microbiol 2002 May-Jun;49(3):201-8
Cedillo-Rivera R, Chavez B, Gonzalez-Robles A, Tapia A, Yepez-Mulia L.
Thirty-eight (81%) of 47 patients in the nitazoxanide treatment group resolved diarrhea within 7 days (median, 3 days) after initiation of treatment, versus 17 (40%) of 42 in the placebo group (P=.0002).
Treatment of diarrhea caused by Giardia intestinalis and Entamoeba histolytica or E. dispar: a randomized, double-blind, placebo-controlled study of nitazoxanide.
Rossignol JF, Ayoub A, Ayers MS.. J Infect Dis 2001 Aug 1;184(3):381-4,
More inforomation about symptoms & treatment is available at the Merck Manual site.
An study in Africa compared four amoebicide drugs treatments on 300 symptomatic patients over a 5 month period. Seventy-six percent submitted 3 follow up stool samples.
The results were:
Metronidazole + Oxytetracycline (tetracycline) - 10.9% continued to excrete E.histo. cysts.
Di-iodohydroxyquinoline ( an older, more toxic version of Iodoquinol/Yodoxin ) and Oxytetracycline : 25.5% continued to excrete E.histo. cysts.
This figure fell to 20% when * Dehydroemetine was added.
Clioquinol and Oxytetracycline - 27.5% continued to excrete the parasite.
*Dehydroemetin is a drug which can cause serious side effects and is usually reserved for dangerously ill patients
Therapeutic trial of four amoebicide regimes in rural Zaire. Masters DK, Hopkins AD. A prospective comparative trial of four amoebicide regimes was carried out with protozoological control using 300 patients presenting with symptomatic intestinal amoebiasis at a tropical rural hospital during a five month period.
J Trop Med Hyg 1979 May;82(5):99-101
The experiences of people infected with E. histolytica who have contacted this site:
Garey endured symptoms typical of a bowel infection for four years before being diagnosed with E. histolytica. He was diagnosed on two occasions with E.histolytica - once after submitting stool samples which were tested by ELISA (antigen) and once by antibody testing. Despite undergoing testing a number of times stool samples a number of times, for tests which included standard ova and parasite stool testing; stool antibody testing (ELISA); and salivary antigen and blood antibody test he tested positive only twice - once by salivary antigen testing, and once by stool antigen testing.
Because the negative results outweighed the positive, Garey's attempts to find a doctor who believed that E.histolytica was causing his symptoms, proved a challange. He consulted more than 10 doctors over four years. He was only offered Flagyl, and despite a number treatments with this drug, his symptoms remained.
He tried to gain the attention of a medical specialist:
"We have a fairly sophisticated infectious disease clinic at the medical school complex here in Portland. At one point I tried to make an appointment about my infection via a naturopathic doctor based on a positive lab test through Great Smokies Diag. I was refused to be seen. The reason given was that I was not thought to be sick enough to require the services of a specialist".
After four years of searching Garey found a specialist endocrinologist interested in treating parasites. To Garey's relief he was a dr "who thinks outside the square" because he was willing to take into consideration the two positive results for E.histolytica and treat him with something other than Flagyl.
Under the guidance of this doctor Garey completely recovered after taking a combination of Humatin and Nitazoxinide.
After his recovery Garey wrote to his first primary care physician outlining the extent of his search for a treatment, enduring misdiagnoses and inadequate treatment for four years until he finally finding a dr who did not dismiss his 2 positive results for E.histolytica. The doctor replied, by registered mail, to inform Garey that "he would no longer be willing to see me for any reason".
Garey wrote: "I can corroborate about the lack of knowledge doctors often have about parasites, symptoms, testing and treatment. I have heard many times that Eh is not pathological. I saw about 10 different doctors. It is remarkable the ignorance of this very serious infection."
This is what Garey was prescribed:
Nitazoxanide 600mg 4 x daily for four days
Paromomycin 250mg 3 x daily for five days .
If this treatment helps you please drop me a line . Your experience will help others make an informed decision about their own treatment .
P. was diagnosed with both E.histolytica and B. hominis and dspite two treatments with Flagyl his symptoms remained unchanged. Two lots of post treatment tests were negative for E.histolytica. Apart from a hiatus hernia, other tests, including a colonoscopy and barium meal x-ray were normal. P. broached with his clinician whether he could still be infected. The clinician advised that "the amoebic dysentry could not be still be around in my gut". Full story here
In 2001 S. became unwell after a food poisoning incident. She was diagnosed by biopsy, after a negative ELISA, and only by chance because a rheumotologist recognised her symptoms as similar to his wife's who had been recently diagnosed with E.histolytica:
"My symptoms were severe, excrutiating pain at times, in my back. A constant lower back pain, which eventually became debilitating. I could barely walk, and could not lift my son. I also had extremely heavy period, later becoming irregular. Fatique, sleeplessness, frequent urination, skin rashes, as well as extreme itching of my skin. Alternating bouts of diarrhea and constipation. Constant feeling of bloating and gas. My husband, after the inital "food poisoining" incident, had the extreme back
pain and was misdiagnosed with sciatica. He was given pain medication for
approximately three months until the symptoms subsided.
Every doctor we saw, always quickly dismissed our suspicions of acquiring a
parasite from shrimp we had from Ecuador, as impossible. Finally, one doctor
decided to test for it by ELISA but the test was negative.
Finally, a rheumatologist who I went too, talked to me for 45 minutes and
recognized my symptoms as being the same as his wifes. She recently had been
diagnosed with an amoeba.(Little did he know we were infected with the exact
same bug.) He sent me to a parasitologist on fith avenue in NYC., NY.
Within two days, after biopsy, he had a diagnosis! The medicine, humatin and
doxycyline, had to be shipped from the city, but three months later we are
negative and on the road to recovery!
received from S, 3 Sept 02
D. had been ill for 6 years after returning from Mexico with symptoms of chronic fatigue, and digestive symptoms severe enough to interfere with D's ability to work. He had never been tested for parasites, despite visiting a high risk country and suffering digestive problems and chronic fatigue. Three samples tested by a specialist lab revealed E.histolytica - a parasite endemic to Mexico:
"Good news - in a way, anyway. I just found out that my stool tested positive for entamoeba histolytica! Probably from a trip to Mexico almost 6 years ago." Feb 02
"I have been researching parasites today and came across your web site. For the last 2 months I have been suffering from nausea and just feeling ill. I have had so many test done the doctors are running out of options.( CT scan, ultrasound, Upper and lower GI, chest exams, blood test, stool test- negative. I recently went to a alternative medical doctor who ordered a more detailed stool analyst. The test also checked saliva. The saliva test came back positive for Ameba histolytica , and Toxoplasma."
S. August 2002
"My symptoms are upper bloating, reflux, heartburn, bad taste in mouth, and sinus trouble. I have been to many docs and have tried many meds. I even had surgery for the reflux which did not work. I have been dealing with this for 4 years. I probably burp 100 times a day. Well last week I decided to see a tropical disease expert in NYC. He did a sigmoinoscopy ( I think that is what it is called). He called me today to tell me that he found mucous, inflamation, and charcoal crystals**??? He says that these are signs of parasitic infection and he is 99% sure I have an ameba called Histelica? He wants to treat me with a 2 week dose of flagyl. I think I may go back for another sig, to see if he can find the bug for sure. Any opinions or advice is greatly appreciated.
P. 13 March 02
Further investigation by sigmoidoscopy confirmed infection with E.histolytica.
**Charcot-Leyden crystals are formed from the breakdown of eosinophils and may be seen in the stool or sputum of patients with parasitic diseases.
Entamoeba histolytica Schaudinn, 1903 and Entamoeba dispar Brumpt, 1925: differences in their cell surfaces and in the bacteria-containing vacuoles.
J Eukaryot Microbiol 2002 May-Jun;49(3):209-19.
Pimenta PF, Diamond LS, Mirelman D.
Amebiasis , Robert Swords, MD.
eMedicine Journal, February 22 2002, Volume 3, Number 2 on-line
Molecular cloning of a 30-kilodalton lysine-rich surface antigen from a nonpathogenic Entamoeba histolytica strain and its expression in a pathogenic strain.
Infect. Immun. 63: 917-925.
Bracha, R., Nuchamowitz, Y. and Mirelman, D. (1995)