Microbiology 15 - Toxoplasma PDF

Microbiology Parasitology Toxoplasma & Balantidium Microbiology| Toxoplasma Contents : Toxoplasma gondii 3 Balantidium coli 19 Microbiology| Toxoplasma Toxoplasma gondii (Tissue Sporozoa) : Phylum: Apicomplexa. Class: Coccidea. worldwide distribution, infecting a wide range of animals and birds. def...

Microbiology Parasitology Toxoplasma & Balantidium Microbiology| Toxoplasma Contents : Toxoplasma gondii 3 Balantidium coli 19 Microbiology| Toxoplasma Toxoplasma gondii (Tissue Sporozoa) : Phylum: Apicomplexa. Class: Coccidea. worldwide distribution, infecting a wide range of animals and birds. definitive hosts: Members of the cat family (Felidae). intermediate hosts: many mammals and birds. Transmission: Congenitally. through the consumption of undercooked infected meat or ingestion of food or drinks contaminated with cat’s feces. Microbiology| Toxoplasma Cats acquire Toxoplasma infection by ingesting any of three infectious stages of the organism: the rapidly multiplying forms called tachyzoites (acute phase of infection). the quiescent bradyzoites (chronic phase of infection) from tissue cysts in the flesh of other animals (mostly rodents). Sporozoites from oocysts (formed during sexual reproduction) shed in cat feces. Microbiology| Toxoplasma Life cycle : 1- Enteric cycle cat ingests meat containing tissue cysts. the cyst wall is dissolved by the proteolytic enzymes in the stomach and small intestine, releasing the bradyzoites. The bradyzoites, which are a slow multiplying stage, penetrate the epithelial cells of the small intestine lead the formation of numerous asexual generations before the sexual cycle (gametogony, the production of gametes) begins. Microbiology| Toxoplasma In sexual cycle and After the fertilization, two walls are laid down around the fertilized zygote to form the oocyst. Oocyst excreted in the feces in an unsporulated stage. Sporulation occurs outside the body, and the oocyst becomes infectious 1 to 5 days after excretion. Microbiology| Toxoplasma Each sporulated oocyst contains two sporocysts. each sporocyst contains four sporozoites. Sporulated oocysts can survive in soil for several months. When oocysts are ingested by the cat, the parasites repeat their asexual and sexual cycle. Microbiology| Toxoplasma 2- Exoenteric cycle If oocysts are ingested by nonfeline intermediate hosts, such as certain birds, rodents, or mammals, including humans, the parasites can establish an infection but reproduce only asexually in extraintestinal cycle. Microbiology| Toxoplasma In human or animals the oocyst opens in duodenum and releases the sporozoites. sporozoites pass through the gut wall, circulate in the body, and invade various cells, especially macrophages, where they form trophozoites. Trophozoites multiply, break out, and spread the infection to lymph nodes and other organs. Microbiology| Toxoplasma These rapidly multiplying crescentic cells (tachyzoites) initiate the acute stage of disease. Within a few hours of infection, tachyzoites may disseminate to extraintestinal tissues through the lymph and blood. Tachyzoites can enter almost any type of host cell and multiply until the host cell is filled with parasites and dies. The released tachyzoites enter new host cells and multiply. Microbiology| Toxoplasma The host usually overcomes this phase of infection, and the parasite then enters the “resting” stage in which bradyzoites are isolated in tissue cysts. Tissue cysts are formed most commonly in the brain, liver, and muscles initiating the chronic stage of disease. Tissue cysts usually cause no host reaction and may remain for the life of the host. The tissue cysts (formerly called pseudocysts) are infective when ingested by cats (resulting in the intestinal sexual stage and oocyst production). when they are eaten by other animals, more tissue cysts are produced (asexually). Microbiology| Toxoplasma Pathogenesis : in humans produces either congenital or postnatal toxoplasmosis. Congenital infection, which develops only when nonimmune mothers are infected during pregnancy, is usually of great severity. postnatal toxoplasmosis is usually much less severe. Most human infections are asymptomatic. In immunosuppressed individuals (as in AIDS patients), resulting in retinitis or chorioretinitis, encephalitis, pneumonitis. Microbiology| Toxoplasma The tachyzoite directly destroys cells. Bradyzoites may cause a local hypersensitivity reaction and inflammation, blockage of blood vessels, and cell death. Congenital infection leads to stillbirths, chorioretinitis, intracerebral calcifications, and hydrocephaly or microcephaly. Microbiology| Toxoplasma Prenatal toxoplasmosis is a major cause of blindness and other congenital defects. Infection during the first trimester results in stillbirth or major CNS anomalies. Second- and third-trimester infections induce less severe neurologic damage. Neurologic problems or learning difficulties may be caused by the long-delayed effects of late prenatal toxoplasmosis Microbiology| Toxoplasma Epidemiology and prevention : Avoidance of human contact with cat feces is clearly important in control. Pregnant women should avoid all contact with cats. Freezing meat at –20°C for 48 hours or heating to 50°C for 4–6 minutes will provide sterilization. Periodic serologic screening for IgG and IgM antibodies to Toxoplasma is recommended. Microbiology| Toxoplasma Diagnosis : T. gondii infection can be identified with serologic testing, amniocentesis (prenatal diagnosis of chromosomal abnormalities and fetal infections). PCR, or by the presence of abnormal ultrasound findings. Microbiology| Toxoplasma Treatment : Toxoplasma infection in healthy immunocompetent individuals is hardly detected and or treated. The commonly used Pyrimethamine (Daraprim), Sulfonamides, Spiramycin and may use combination drugs. No killed vaccine is currently available. Balantidium Microbiology| Balantidium Balantidium coli : Phylum: Ciliophora. Class: Litotstomatea. Balantidium is the only ciliated protozoan known to infect humans. Disease: Balantidiasis is a zoonotic disease and is acquired by humans via the fecooral route from the normal host, the pig (or rodents), where it is asymptomatic. Transmission: Contaminated water. Morphology trophozoite stage (two nuclei are visible). cyst stage. Microbiology| Balantidium The macronucleus is long and the spherical micronucleus is next to it, often hidden by the macronucleus. The opening, known as the peristome, at the pointed anterior end leads to the cytostome, or the mouth. Cysts are smaller than trophozoites and are round and have a tough, heavy cyst wall made of one or two layers. Microbiology| Balantidium Life cycle : Infection: by consumption of contaminated water or food. Infective stage: cyst. cyst passes through the host’s digestive system reaches the small intestine, trophozoites are produced. The trophozoites then colonize the large intestine, where they live in the lumen and feed on the intestinal flora. Microbiology| Balantidium Some trophozoites invade the wall of the colon using proteolytic enzymes and multiply, and some of them return to the lumen. In the lumen trophozoites may undergo encystation in the distal large intestine, but may also occur outside of the host in feces. When, mature cyst form, cysts are released into the environment and infect a new host. Microbiology| Balantidium Pathogenesis : Most infections with B. coli apparently harmless. However, the trophozoites invade the mucosa and submucosa of large intestine and produce ulcers. If left untreated, Balantidiasis can become chronic. Persistent diarrhea can lead to high fluid loss and dehydration. diarrhea, alternating with constipation, is the most common clinical manifestation. Abdominal bleeding can lead to death. Extraintestinal involvement such as liver, peritonea and lung may occur. Microbiology| Balantidium Diagnosis : Balantidiasis is diagnosed by microscopic examination of a patient’s feces (wet mount). Trophozoites can also be detected in tissue. In order to collect a tissue specimen from the large intestine, a sigmoidoscopy procedure is used. Treatment: Tetracyclines, Metronidazole, Iodoquinol.