ProjectIn

Microbiology

Submitted to:Yolanda Ilagan Ph. D

Submitted by:Irish Jane B. Cubillo

BSN 2-2

A. Protozoa 1. Intestinal Protozoa

1.a Entamoeba Histolytica

Cysts and trophozoites are passed in feces. Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool. Infection by Entamoeba histolytica occurs by ingestion of mature cysts in fecal contaminated food, water, or hands. Excystation occurs in the small intestine and trophozoites are released, which migrate to the large intestine. The trophozoites multiply by binary fission and produce cysts, and both stages are passed in the feces.

1.b Giardia Lamblia

Cysts may remain viable for several months in cool, moist conditions, and have been detected in natural surface waters. Infection occurs after cysts are ingested. After ingestion, mature cysts in the small intestine release trophozoites through a process called excystation. Trophozoites colonize the small intestine, attaching to the mucosa of the bowel using a ventral sucking disk. The trophozoites then multiply by longitudinal binary fission.

1.c Balantidium coli

The cyst stage begins right when the trophozoite is released in feces. Encytation is the process of becoming enclosed in a cyst. This process takes place in the rectum. After the release of trophozoites in the feces starts to dehydrates right away. When a stool sample if first observed, the cysts may still have cilia, but after encystation the cilia disappear. The macronucleus and the micronucleus can still be seen in stained specimens. Because cysts exists in fecal matter, this is when contamination comes into play. Feces can contaminate water or food. Once the contaminated food or water has entered the host’s digestive system, cysts can start infecting. This allows them to pass through the digestive system without being destroyed. Once in the large intestine excystation occurs. This is when trophozoites are produced from cysts.

1.d Crytosporidium parvum

Transmission of Cryptosporidium parvum and C. hominis occurs mainly through contact with contaminated water (e.g., drinking or recreational water). Occasionally food sources, such as chicken salad, may serve as vehicles for transmission. Many outbreaks in the United States have occurred in waterparks, community swimming pools, and day care centers. Zoonotic and anthroponotic transmission of C. parvum and anthroponotic transmission of C. hominis occur through exposure to infected animals or exposure to water contaminated by feces of infected animals. Following ingestion (and possibly inhalation) by a suitable host, excystation occurs.

2. Tissue and Blood Protozoa

2.a Trypanosoma Cruzi

Trypanosoma cruzi life cycle starts in an animal reservoir. These reservoirs are usually mammals, wild or domestic, and include humans. A reduviid bug serves as the vector. While taking a blood meal it ingests T. cruzi. In the reduviid bug, they go into the epimastigote stage. This makes it possible to reproduce. After reproducing through mitosis, the epimastigotes move onto the rectal cell wall. There, they become infectious. Infectious T. cruzi are called trypomastigotes. Then, while the reduviid bug is taking a blood meal from a human, it defecates. The trypomastigotes are in the feces. The trypomastigotes enter the human host through the bite wound or by crossing mucous membranes. When they enter a human cell, they become amastigotes. This is another reproductive stage. After reproducing through mitosis until a large amount of amastigotes are in a cell, pseudocysts are formed in infected cells. The amastigotes then turn back into trypomastigotes, and the cell bursts. The trypomastigotes swim along to either infect other cells or get sucked up by other reduviid bugs.

2.b Leishmania Donovani

Leishmania donovani major parasites are transmitted into skin by the bite of a sandfly. Promastigotes, the infectious stage of L. major, are then rapidly taken up by resident skin macrophages (MΦ), but not dendritic cells (DC). Within MΦ, promastigotes transform into obligate intracellular amastigotes and replicate. Free amastigotes are released from lysed MΦ, which can then infect DC. Infected DC are activated, migrate to draining lymph nodes and activate T cells to become Th1 cells (via IL-12). IFNγ released from Th1 cells induces MΦ to upregulate iNOS and eliminate intracellular organisms. The life cycle is completed upon re-infection of sand flies after feeding at infected skin sites.

2.c Trypanosoma Brucei gambiense and T. rhodesiense

(a) Development in the peripheral blood of humans (b) Development in tsetse flies (Glossina) (c) Development in the peripheral blood of the reservoir host is similar to human host.

2.d Plasmodium sp.

2.e Toxoplasma gondii

3. Luminal Protozoa

3.a Trichomonas vaginalis

B. Helminthes 1. Nematodes

1.a Enterobius vermicularis

Humans get infected by accidentally swallowing or inhaling microscopic pinworm eggs. Once inside the first part of the small intestine, duodenum, pinworm larvae hatch from the eggs. The larvae are only about 0.15 mm long but grow very fast. They migrate towards the ending of the small intestine as they mature into adults. Adults are white, thin worms. The males usually die after the pinworms have mated in the last part of the small intestine, ileum. The gravid (pregnant) female resides at the beginning of the large intestine, colon, eating what ever food passes through the intestinal tract. Female pinworm reaches fertility within four weeks.

1.b Trichuris trichiuria

Whipworm's life cycle starts, when the female lays eggs in the large intestine of an infected human. The eggs are carried out in the feces landing on soil. If landed on warm moist soil, after 2–3 weeks the eggs have embryonated and are infective ready to be ingested. The eggs get inside you, if you eat contaminated unwashed and uncooked vegetables, rice or beans. Larvae hatch in the small intestine and invade the intestinal villi and start growing. After a while they move to the large intestine where they penetrate the mucosa and develop into adults. Only the head part, the anterior of the worm is threaded into the intestinal wall. The posterior end is hanging loose, ready to mate, if another whipworm of the opposite sex passes by. The life cycle completes, when females and males mate and eggs are produced at the rate of 2000–10000 eggs per day. The cycle from egg to mature adult takes a few months. Adult females live about five years.

1.c Ascaris Lumbricoides

Adult worms live in the lumen of the small intestine. A female may produce up to 240,000 eggs per day, which are passed with the feces. Fertile eggs embryonate and become infective after 18 days to several weeks 3, depending on the environmental conditions optimum: moist, warm, shaded soil). After infective eggs are swallowed, the larvae hatch, invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs. The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed. Upon reaching the small intestine, they develop into adult worms.

Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years.

1.d Capillaria Philippinensis

Typically, unembryonated eggs are passed in the human stool and become embryonated in the external environment; after ingestion by freshwater fish, larvae hatch, penetrate the intestine, and migrate to the tissues. Ingestion of raw or undercooked fish results in infection of the human host. The adults of Capillaria philippinensis (males: 2.3 to 3.2 mm; females: 2.5 to 4.3

mm) reside in the human small intestine, where they burrow in the mucosa. The females deposit unembryonated eggs. Some of these become embryonated in the intestine, and release larvae that can cause autoinfection. This leads to hyperinfection (a massive number of adult worms). Capillaria philippinesis is currently considered a parasite of fish eating birds, which seem to be the natural definitive host.

1.e Hookworm

2.e1 Necator Americanus and Ancylostoma duodenales

Eggs are passed in the stool, and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days. The released rhabditiform larvae grow in the feces and/or the soil, and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective. These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend

the bronchial tree to the pharynx, and are swallowed. The larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host. Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years.

1.f Trichinella Spiralis

The typical life cycle for T. spiralis involves humans, pigs, and rodents. Pigs become infected when they eat infectious cysts in raw meat, often pork or rats (sylvatic cycle). Humans become infected when they eat raw or undercooked infected pork (domestic cycle). After humans ingest the cysts from infected undercooked meat, pepsin and hydrochloric acid help free the larvae in the cysts in the stomach. The larvae then migrate to the small intestine, where they molt four times before becoming adults.Thirty to 34 hours after the cysts were originally ingested, the

adults mate, and within five days produce larvae.The worms can only reproduce for a limited time because the immune system will eventually expel them from the small intestine.The larvae then use their piercing mouthpart, called the “stylet”, to pass through the intestinal mucosa and enter the lymphatic vessels, and then enter the bloodstream.The larvae travel by capillaries to various organs, such as the retina, myocardium, or lymph nodes; however, only larvae that migrate to skeletal muscle cells survive and encyst. The larval host cell becomes a nurse cell in which the larvae will encapsulate. The development of a capillary network around the nurse cell completes encystation of the larvae.

1.g Filarial Nematodes

Microfilariae enter the host during a blood meal when the vector, a mosquito, punctures the skin. The infective larvae enter through the wound and migrate to the peripheral lymphatics where they grow to mature male and female worms. They can live there for several years. After mating,

the gravid females release sheathed microfilariae into the peripheral blood where they can be detected 8-12 months after the initial infected bite.

2. Platyhelmenthes2.a Cestodes

2.a1 Diphyllobothrium latum

The life cycle of Diphyllobothrium latum starts, when immature eggs are passed in the feces of an infected human. The eggs mature in water within three weeks and form oncospheres. Larvae called coracidia hatch and get eaten by freshwater crustaceans such as copepod. After ingestion coracidia develop into procercoid larvae. If the copepod is eaten by a small fish (second intermediate host), the procercoid larvae penetrate the gut and migrate to muscle tissue where they develop into plerocercoid larvae (sparganum), the infective stage for

humans. Usually a third intermediate host is needed because humans do not usually eat raw fish this small. If a trout, walleyed pike or perch eats the smaller fish, the plerocercoid larvae once again penetrate the gut and migrate to fish flesh. If a human eats the infected fish raw or undercooked the plerocercoid larvae develop into adults in the small intestine.

2.a2 Taenia Saginata

2.a3 Taenia Solium

2.a4 Echinococcus granulosus

Dogs feed on infected sheep meat and in turn shed eggs in their faeces which are ingested by sheep. Humans become infected by ingesting food or water contaminated with faecal material containing tapeworm eggs passed from infected carnivores, or when they handle or pet infected dogs.

2.b Trematodes2.b1 Schistosoma sp.

Eggs are eliminated with feces or urine. Under optimal conditions the eggs hatch and release miracidia, which swim and penetrate specific snail intermediate hosts. The stages in the snail include 2 generations of sporocysts and the production of cercariae. Upon release from the snail, the infective cercariae swim, penetrate the skin of the human host, and shed their forked tail, becoming schistosomulae. The schistosomulae migrate through several tissues and stages

to their residence in the veins. Adult worms in humans reside in the mesenteric venules in various locations, which at times seem to be specific for each species.

2.b2 Chlonorchis sinensis

2.b3 Fasciola hepatica

2.b4 Paragonimus westermani

2.b5 Fasciola buski

Immature eggs are discharged into the intestine and stool. Eggs become embryonated in water, eggs release miracidia, which invade a suitable snail intermediate host. In the snail the parasites undergo several developmental stages (sporocysts, rediae, and cercariae). The cercariae are released from the snail and encyst as metacercariae on aquatic plants. The mammalian hosts become infected by ingesting metacercariae on the aquatic plants. After ingestion, the metacercariae excyst in the duodenum and attach to the intestinal wall. There

they develop into adult flukes (20 to 75 mm by 8 to 20 mm) in approximately 3 months, attached to the intestinal wall of the mammalian hosts (humans and pigs). The adults have a life span of about one year.