Chapter 3: The Amoebas PDF

CHAPTER 3 Phylum Sarcomastigaphora (Amoeba & Flagellates ) JEROME U. TAMAYAO, MST  Phylum Sarcomastigophora Amoeboid and flagellated parasite Amoeba Sub phylum Sarcodina Presence of foot like projection in the cytoplasm (pseudopodia) flagellates Sub phylum mastigophora...

CHAPTER 3 Phylum Sarcomastigaphora (Amoeba & Flagellates ) JEROME U. TAMAYAO, MST  Phylum Sarcomastigophora Amoeboid and flagellated parasite Amoeba Sub phylum Sarcodina Presence of foot like projection in the cytoplasm (pseudopodia) flagellates Sub phylum mastigophora Presence of whiplike flagella Amoeba Ameboid characteristics Cortical zone of undifferentiated ectoplasm Presence of pseudopodia Human: Entamoeba naegleria Acanthamoeba Six species of entamoeba: (commensal) E. coli E. hartmanni E. dispar E. moshkovskii E. gingivalis E. histolutica (pathogenic) E. polecki (zoonotic protozoa of pig) The genus Entamoeba Affect both invertebrates and vertebrates Vesicular nucleus with small karyosome Peripheral chromatin attached to the nuclear membrane Distinguished: E. histolytica, e. dispar, e. moshkovskii, E. Morphologically similar and can only differentiated by isoenzyme analysis, Polymerase chain reaction, monoclonal antibodies Generalities: All entamoeba are lumen-dwelling protozoan except E. gingivalis All are non pathogenic except E. histolytica  MORPHOLOGY AND LIFE CYCLE NOTES Structure The trophozoite is 10 to 60 µm in diameter, ameboid, actively motile, and often erythrophagocytic. In stained specimens, the nucleus has a central karyosome with finely beaded peripheral chromatin. The cyst form is rounded, 10 to 20 µm in diameter, with one to four nuclei showing the characteristic appearance. A chromatoidal bar with rounded or square ends may be seen. amoebas LABORATORY DIAGNOSIS PATHOGENESIS AND CLINICAL Proper determination of organism size, using the SYMPTOMS ocular micrometer. A number of patients infected with intestinal The presence of other amebic structures and amebas are asymptomatic. characteristics, such as cytoplasmic inclusions and Amebas are often discovered, however, in patients motility, also aids in the identification of the suffering from diarrhea without an apparent cause. amebas. Standard microscopic procedures include Diagnosis of nonpathogenic amebas is important examination of specimens for amebas using saline because this finding suggests that the ingestion of wet preparations, iodine wet preparations, and contaminated food or drink may have occurred. permanent stains. The presence of pathogenic amebas in addition to nonpathogenic amebas is also possible because the transmission route of both amebic groups is identical. Thorough screening of such samples is crucial to ensure proper identification of all parasites Pathogenesis The colon may be colonized without invasion of mucosa. The critical factor determining colonization is the ability of the ameba to adhere to colonic mucosal lining cells. Invasion of the mucosa produces ulcers that sometimes progress by direct extension or by metastasis. Metastatic infection first involves the liver. Extension or metastasis from the liver may involve the lung, brain, or other viscera. Host Defenses Gastric acid and rapid intestinal transit are nonspecific defenses. Humoral antibody and cell-mediated immunity play limited roles in preventing dissemination. Epidemiology Fecal-oral transmission of cysts involves contaminated food or water. Amoebas can be transmitted directly by sexual contact involving the anus. Diagnosis Acute diarrhea is the usual presentation of symptomatic disease. Ulceration is associated with occult or gross blood in stool and/or with a visceral abscess. The condition may be confirmed by identification of E histolytica in the stool or in abscess aspirates. The ameba in abscesses line the wall of the abscess cavity and thus will be found in the last material aspirated from the abscess. Ameba can be cultured. Positive serologic tests, particularly tests showing rising antibody levels, may provide indirect evidence of infection. CLASSIFICATION-Entamoeba histolytica  E. histolytica E. Histolytica tropozoite E. histolytica Cyst PARAMETER DESCRIPTION Size range 8-65 um 8-22 um Motility Progressive, finger like Shape: spherical to round pseudopodia Number of nuclei 1 1-4 Karyosome Small and central Small and central Peripheral Fine and evenly distributed Fine and evenly distributed chromatin Cytoplasm Finely granular Finely granular Cytoplasmic Ingested rbc Chromatoid bars, rounded ends inclusion in young cysts Diffuse glycogen mass in young cysts Common associated disease or condition names: Intestinal amebiasis, amebic colitis, amebic dysentery, extraintestinal amebiasis. Laboratory Diagnosis The diagnosis of E. histolytica infection may be Clinical symptoms depends on two major factors: (1) the location(s) of the parasite in the host; and accomplished by standard and alternative (2) the extent of tissue invasion. methods. Asymptomatic Carrier State. Three factors, acting separately or in traditional wet preparation and permanent combination, are responsible for the asymptomatic carrier state of staining techniques material collected from a patient infected with E. histolytica: a sigmoidoscopy procedure, as well as (1) the parasite is a low-virulence strain; hepatic abscess material, may be (2) the inoculation into the host is low; and processed and examined in the same (3) the patient’s immune system is intact. In these manner. cases, amebas may reproduce but the infected patient shows no clinical symptoms. immunologically based procedures, Symptomatic Intestinal Amebiasis. Patients infected with E. Methods currently available include histolytica who exhibit symptoms often suffer from amebic colitis, antigen tests, enzyme-linked defined as an intestinal infection caused by the presence of immunosorbent assay (ELISA), amebas exhibiting symptoms. In some cases, these patients may indirect hemagglutination (IHA), transition from amebic colitis into a condition characterized by gel diffusion precipitin (GDP), and blood and mucus in the stool known as amebic dysentery. indirect immunofluorescence (IIF). Individuals with amebic colitis may exhibit nondescript abdominal Serologic tests designed to detect E. symptoms or may complain of more specific symptoms, including diarrhea, abdominal pain and cramping, chronic weight loss, histolytica are available and are typically anorexia, chronic fatigue, and flatulence. Secondary bacterial only helpful in cases of extraintestinal infections may develop after infections Treatment : asymptomatic individuals: Paromomycin diloxanide furoate (Furamide), or metronidazole (Flagyl). Patients showing symptomatic intestinal amebiasis typically respond well to: iodoquinol, paromomycin, or diloxanide furoate. Metronidazole or tinidazole, in combination with a symptomatic intestinal amebiasis treatment, is recommended for patients who have progressed to extraintestinal amebiasis Prevention and Control Several steps may be taken to prevent E. histolytica infections. Uncontaminated water is essential; this may be accomplished by boiling or treating with iodine crystals. It is interesting to note that the infective (quadrinucleated) cyst is resistant to routine chlorination. A water treatment regimen that includes filtration and chemical treatment is necessary to ensure a safe water supply. Properly washing food products, avoiding the use of human feces as fertilizer, good personal hygiene and sanitation practices, protection of food from flies and cockroaches, avoidance of unprotected sexual practices serve as a means to break the transmission cycle Entamoeba hartmanni E. Hartmanni tropozoite E. Hartmanni Cyst PARAMETER DESCRIPTION Size range 5-15 um 5-12 um Motility Non progressive, finger like Shape: spherical pseudopods Number of nuclei 1 1-4 Karyosome Small and central Small and central Peripheral Fine and evenly distributed Fine and evenly distributed chromatin Cytoplasm Finely granular Finely granular Cytoplasmic Ingested bacteria may be Chromatoid bars, rounded ends inclusion present in young cyst diffuse glycogen mass in young cyst E. Hartmanni Cyst E. Hartmanni trophozoite Laboratory Diagnosis Laboratory diagnosis is accomplished by examining stool for E. hartmanni trophozoites and cysts. It is important to note that the size ranges of E. histolytica and E. hartmanni overlap. For example, trophozoites that measure 12 µm and cysts that measure 10 µm are within the size range of both parasites. Specific identification based only on size in such cases is impossible. Proper use of the ocular micrometer is therefore essential to obtain correct measurements of suspected organisms. Clinical Symptoms Infections with E. hartmanni are typically asymptomatic. Treatment E. hartmanni, it is generally considered a nonpathogen and treatment is usually not indicated. Prevention and Control Good sanitation and personal hygiene practices, protection of food from flies and cockroaches  Entamoeba coli E. coli tropozoite E. coli Cyst PARAMETER DESCRIPTION Size range 12-55 um 8-35 um Motility Non-progessive, blunt Shape: round and spherical pseudopods Number of nuclei 1 1-8 Karyosome Large, irregular shape, eccentric Large, irregular shape, eccentric Peripheral Unevenly distributed Unevenly distributed chromatin Cytoplasm Coarse and granulated Coarse and granulated Cytoplasmic Vacoules containing bacteria Diffuse glycogen mass present inclusion often visible in young cysts; may displace nuclei (often seen in cysts with two nuclei) to opposite ends of Common associated disease or condition names: Intestinal the cyst amebiasis, amebic colitis, amebic dysentery, extraintestinal amebiasis. E. coli cyst E. coli trophozoite Laboratory Diagnosis Stool examination is the method of choice for the recovery of E. coli trophozoites and cysts. Clinical Symptoms Asymptomatic Treatment E. coli is considered a nonpathogen. Treatment, therefore, is usually not indicated. Prevention and Control The adequate disposal of human feces proper personal hygiene practices, Protection of food and drink from flies and cockroaches Entamoeba polecki E. polecki tropozoite E. polecki Cyst PARAMETER DESCRIPTION Size range 8-25 um 10-20 um Motility (normal stool)- sluggish, Shape: spherical and oval (diarrheal stool)-progressive Number of nuclei 1 1 Karyosome Small and central Small and central Peripheral Fine and evenly distributed Fine and evenly distributed chromatin Cytoplasm Granular and vacuolated Granular Cytoplasmic Ingested bacteria other food Chromatoid bars, angular or inclusion particles pointed ends in young cyst E. polecki cyst E. polecki trophozoite Laboratory Diagnosis The trophozoites and cysts of E. polecki may be diagnosed by examining stool samples Clinical Symptoms Most patients with E. polecki are asymptomatic. The only documented discomfort associated with symptomatic patients is diarrhea. Treatment A combination of metronidazole (Flagyl) and diloxanide furoate (Furamide) Prevention and Control E. polecki may be prevented by improving personal hygiene and sanitation practices. Education programs regarding the routes of transmitting E. polecki infection are also essential. Endolimax nana E. nana tropozoite E. nana Cyst PARAMETER DESCRIPTION Size range 5-12 um 4-12 um Motility Sluggish, non progressive, blunt Shape: spherical, ovoid, pseudopods ellipsoid Number of nuclei 1 1-4 Karyosome Large, irregular, blotlike Large, blotlike, usually central Peripheral Absent Absent chromatin Cytoplasm Granular and vacuolated Granular and vacuolated Cytoplasmic bacteria Nondescript small mass diffuse inclusion glycogen mass in young cyst E. nana cyst E. nana trophozoite Laboratory Diagnosis stool examination Clinical Symptoms E. nana infections are usually asymptomatic. Treatment E. nana is considered a nonpathogen. Treatment is generally not indicated. Prevention and Control protection of food and drink from flies and cockroaches good sanitation and personal hygiene practices Iodamoeba bütschlii I. butschlii tropozoite I. butschlii Cyst PARAMETER DESCRIPTION Size range 8-22 um 5-22 um Motility Sluggish, usually progressive Shape: ovoid, ellipsoid, triangular, other shape Number of nuclei 1 1 Karyosome Large, central, refractive Large, eccentric. Achromatic achromatic granules may or not granules on one side may be be present present Peripheral Absent Absent chromatin Cytoplasm Coarsely granular and Coarsely granular and vacuolated vacuolated Cytoplasmic Bacteria, yeast cell and other Well define glycogen mass inclusion debris granules may be present I. butschlii cyst I. butschlii trophozoite Laboratory Diagnosis Iodine wet preparation Clinical Symptoms I.bütschlii is a nonpathogenic intestinal ameba that usually does not produce clinical symptoms. Treatment treatment is usually not indicate Prevention and Control personal hygiene and sanitation practices in substandard areas. Entamoeba gingivalis E. gingivalis tropozoite E. gingivalis Cyst PARAMETER DESCRIPTION Size range 8-20 um n/a Motility Active, varying pseudopods n/a appearance Number of nuclei 1 n/a Karyosome Centrally located n/a Peripheral Fine and evenly distributed n/a chromatin Cytoplasm Finely granular n/a Cytoplasmic Leukocytes, epithelial cells n/a inclusion bacteria E. Gingivalis trophozoite E. Gingivalis life cycle Laboratory Diagnosis An accurate diagnosis of E. gingivalis trophozoites may best be made by examining mouth scrapings (see Chapter 2), particularly from the gingival area. Material from the tonsillar crypts and pulmonary abscess, as well as sputum, may also be examined. Vaginal and cervical material may be examined to diagnose E. gingivalis in the vaginal and cervical areas. Clinical Symptoms Infections of E. gingivalis occurring in the mouth and in the genital tract typically produce no symptoms. Nonpathogenic E. gingivalis trophozoites are frequently recovered in patients suffering from pyorrhea alveolaris. It appears that the trophozoites thrive under disease conditions but do not produce symptoms of their own. Treatment Treatment of E. gingivalis is typically not indicated because the organism is generally considered a nonpathogen. Prevention and Control Improved oral hygiene accomplished by the proper care of the teeth and gums is necessary to prevent the spread of oral E. gingivalis infections. Prompt removal of IUDs in infected patients spontaneously removes E. gingivalis from the genital tract. Naegleria fowleri N. fowleri tropozoite N. fowleri Cyst PARAMETER DESCRIPTION Size range 8-22 um 9-12 um Motility Sluglike, blunt pseudopods Shape: round and have thick cell Number of nuclei 1 1 Karyosome Large and usually central Large centrally located located Peripheral Absent Absent chromatin Common associated Cytoplasm Granular, usually vacuolated Granular and often contain disease or condition vacuoles name: Primary amebic Cytoplasmic n/a n/a inclusion meningoencephalitis (PAM) N. Fowleri cyst N. Fowleri trophozoite N. fowleri life cycle Laboratory Diagnosis Microscopic examination of cerebrospinal fluid (CSF) is the method of choice for the recovery of N. fowleri ameboid trophozoites. Preparing and scanning saline and iodine wet preparations of the CSF are recommended. Samples of tissues and nasal discharge may also be examined. Clinical specimens may be cultured. N. fowleri ameboid trophozoites show a characteristic trailing effect when placed on agar plates that have been previously inoculated with gram-negative bacilli. Clinical Symptoms Asymptomatic. Patients who contract N. fowleri resulting in colonization of the nasal passages are usually asymptomatic. Primary amebic meningoencephalitis. Primary amebic meningoencephalitis (PAM) occurs when the ameboid trophozoites of N. fowleri invade the brain, causing rapid tissue destruction. Patients may initially complain of fever, headache, sore throat, nausea, and vomiting. Symptoms of meningitis rapidly follow, including stiff neck and seizures. In addition, the patient will often experience smell and taste alterations, blocked nose, and Kernig’s sign (defined as a diagnostic sign for meningitis, where the patient is unable to fully straighten his or her leg when the hip is flexed at 90 degrees because of hamstring stiffness). In untreated patients, death usually occurs 3 to 6 days after onset. Postmortem brain tissue samples of these patients reveal the typical ameboid trophozoites of N. fowleri Treatment amphotericin B may be of benefit to patients suffering from infections with N. fowleri, despite its known toxicity. In rare cases, amphotericin B in combination with rifampin or miconazole has also proved to be an effective treatment. Amphotericin B and miconazole damage the cell wall of Naegleria, inhibiting the biosynthesis of ergosterol and resulting in increased membrane permeability, which causes nutrients to leak out of the cells. Rifampicin inhibits RNA synthesis in the amoeba by binding to beta subunits of DNAdependent RNA polymerase, which in turn blocks RNA transcription. A person can survive if signs are recognized early but, if not, PAM almost always results in death. Prevention and Control Water contamination Acanthamoeba species Acanthamoeba species Acanthamoeba species cyst tropozoite PARAMETER DESCRIPTION Size range 12-45 um 8-25 um Motility Sluggish, spinelike, pseudopods Shape: roundish with ragged edges Number of nuclei 1 1 Karyosome Large Large and central Peripheral Absent Absent chromatin Cytoplasm Granular and vacuolated Disorganized Common associated disease or Cytoplasmic n/a Others: double cell wall condition names: Granulomatous amebic encephalitis (GAE), inclusion Acanthamoeba keratiti Acanthmoeba species cyst Acanthmoeba species trophozoite Acanthmoeba species life cycle Laboratory Diagnosis Brain tissue may also be examined. Corneal scrapings are the specimen of choice for recovery of Acanthamoeba infections of the eye. Suspected corneal scrapings may be cultured on non-nutrient agar plates seeded with gram- negative bacteria (specifically, a viable strain of E. coli). Clinical Symptoms Granulomatous amebic encephalitis. CNS infections with Acanthamoeba are also known as granulomatous amebic encephalitis (GAE). Symptoms of this condition develop slowly over time and include headaches, seizures, stiff neck, nausea, and vomiting. Granulomatous lesions of the brain are characteristic and may contain both Acanthamoeba trophozoites and cysts. On occasion, Acanthamoeba spp. invade other areas of the body, including the kidneys, pancreas, prostate, and uterus, and form similar granulomatous lesions. Acanthamoeba keratitis. Acanthamoeba infections of the cornea of the eye are known as amebic keratitis. Common symptoms include severe ocular pain and vision problems. The infected tissue of the cornea may contain Acanthamoeba trophozoites and cysts. Perforation of the cornea may result, as well as subsequent loss of vision Treatment sulfamethazine might be a suitable treatment. several medications that include itraconazole, ketoconazole, miconazole, propamidine isethianate, and rifampin. Of all these agents, propamidine appears to have the best documented success record. Prevention and Control Strategies designed to keep individuals from contracting Acanthamoeba CNS infections are difficult to determine because the life cycle of this ameba is poorly understood. However, eye infections with Acanthamoeba may be prevented primarily by following all manufacturer-established protocols associated with the use of contact lenses. One of the most important protocols for contact lens wearers is to avoid using homemade nonsterile saline solutions.