Ch 12 Micro – Flashcards

Yeast is unicellular, while mold is multicellular.

Place the sample in a clear container filled with media containing no sugars, and leave it in a sunny window. After a few weeks, look for growth of the organism.

a chemical that inhibits the formation of cell walls

Apicomplexa Apicomplexa contains many species that cause disease, including the Plasmodium species that cause Malaria.

Taenia saginata; tapeworm

Plasmodium species The life cycle of Plasmodium species requires two hosts, one of which is a mosquito.

cutaneous mycoses Dermatophytes (Greek for "skin plants") is a common label for a group of three types of fungi that cause skin disease in humans and other animals.

gastrointestinal route.

have highly developed digestive and nervous systems.

are multicellular animals. can be divided into flukes and tapeworms. are dorsoventrally flattened. are hermaphroditic.

cysticercus.

adult

intestinal contents

can tolerate low-moisture conditions.

dimorphic fungus.

fungus.

Candida albicans.

eliminate Anopheles

Cryptosporidium

humans are the intermediate host and mosquitoes are both the definitive host and the vector.

houseflies

mosquito - Pneumocystis

a single oral dose of fluconazole a topical over-the-counter ointment, such as clotrimazole or miconazole

fulminating disease oral thrush

Fungal cells and human cells have a nucleus, multiple organelles, and 80S ribosomes for protein synthesis.

One of the key similarities between a fungus and its human host is that both are eukaryotic. This makes it difficult to develop antifungal drugs, because therapeutic agents that target certain properties of the fungus (e.g., ergosterol in the membrane, DNA replication, protein synthesis) also have the potential to target the host cells. One of the keys to antimicrobial therapy is selective toxicity, which means that the agent will hinder/kill the pathogen without doing much damage to the host. The more similar the agent is to its host, the harder it is to achieve selective toxicity.

Blastoconidia and chlamydoconidia are spore structures produced by budding in yeasts, whereas bacterial endospores are produced by bacteria under extreme conditions. Blastoconidia and chlamydoconidia are asexual spores used for reproduction. Blastoconidia and chlamydoconidia produce cells that are identical to the parent cells, whereas sexual spores produce offspring that have characteristics of both parents. Endospores are produced by bacteria during harsh conditions.

Yeasts use pseudohyphae to invade host tissue, whereas filamentous fungi use their vegetative hyphae for obtaining nutrients. Yeasts use the pseudohyphae as a virulence factor to better penetrate the host's tissues and also to evade phagocytosis. Filamentous fungi use their vegetative hyphae as a means to absorb nutrients from their environment. In optimal conditions, the vegetative hyphae will grow into a substrate to obtain food and will then support the growth of aerial hyphae, which project above the surface of the medium. These aerial hyphae are responsible for producing the reproductive spores of the fungus.

He will have the laboratory prepare the samples for an ova and parasite (O&P) exam. Fresh or preserved stool samples can be observed microscopically for the presence of parasites or their eggs/cysts. Tapeworms are pathogens of the gastrointestinal tract; as a natural progression of digestion some of the tapeworm pieces will be expelled along with fecal matter. Investigation of stool samples is an important diagnostic tool for physicians and other medical personnel. The stool is prepared in such a way that any parasite eggs or proglottids remain in the sample. After processing, the sample is placed on a microscope slide for observation. Staining can be performed, but is not always necessary. Morphological examination of any specimen found in the stool will help with identification.

Foodborne - Eating undercooked, unwashed, or otherwise contaminated food that contained parasitic propagules The most likely mode of transmission in Michael's case was through the undercooked pork that he ate in his stir-fry. Humans are a definitive host for the pork tapeworm and are infected when they ingest larval cysts embedded in the muscle tissue of the pig. This transmission cycle is common in Africa, Asia, and Latin America. Interestingly, pigs in the United States are virtually parasite-free, and pork tapeworm infections are transmitted person-to-person via the fecal-oral route. Eggs from infected people with poor hygiene can be ingested by others, which allows the life cycle to continue without the pigs as an intermediate host.

Taenia solium T. solium is the tapeworm associated with eating undercooked pork. Eggs and proglottids from the adult tapeworm are released in the intestines and can be observed in fecal samples with a light microscope. Diagnosis is based on these findings.

Tapeworms utilize diffusion to absorb nutrients from the host's digestive system. The tapeworm's high surface-area-to-volume ratio is an adaptation to utilize diffusion in the nutrient-rich environment of the host's intestine. These worms lack digestive structures and must rely on the host to completely digest food before it is absorbed by the worm via its outer layer called a cuticle. Roundworms have a more complex digestive system and are capable of digesting food that has only been partially digested by the host. This decreases the need for a high surface-area-to-volume ratio because diffusion of nutrients is no longer an issue.

The adult worm produces thousands of eggs in the human host. These eggs leave the digestive tract via the feces. When pigs eat grass contaminated with, or fertilized by, human feces they become infected with T. solium. The tapeworm eggs mature into larvae that encyst themselves in the muscle tissue of the pig. When humans eat pork that has not been cooked to high enough temperatures, they become infected with the tapeworm.

IgE is the class of antibodies involved in hypersensitivities such as allergies and parasitic infections. IgE is typically found in very low amounts in the blood serum. It increases in response to allergic reactions and parasitic infections. There is also a correlation with an increase in IgE amounts and the increase of eosinophils in a blood smear. Eosinophils are white blood cells that release peroxide ions to destroy the parasite from the outside.

Praziquantel or albendazole, drugs that target eukaryotic parasites with minimal side effects in the host. Praziquantel and albendazole are both anti-helminthic drugs. Praziquantel is effective against tapeworms because it changes the permeability of the cuticle and blocks nutrient uptake. During this process the drug also uncovers surface antigens that stimulate an immune response. Albendazole is a broad-spectrum anti-helminthic drug that also blocks nutrient uptake by inhibiting microtubule formation in the cytoplasm. It is used commonly to treat livestock as well.

When tapeworm larvae escape the stomach, they can travel to other parts of the body such as muscles, the liver, the eye, and even the brain to form cysticerci. The presence of T. solium in the brain can result in neurocysticercosis, a serious condition which has symptoms resembling those of brain tumors or epilepsy. Tapeworms in the intestinal tract are usually asymptomatic. Humans are the definitive host and support the growth of adult tapeworms. Pigs are intermediate hosts that continue the life cycle of T. solium. Occasionally, the human host can become an intermediate host. Larvae escape the stomach and migrate to other tissues in the body. Once in other tissues, the larvae form cysts called cysticerci. These cysts can cause problems, especially in the eye and in the brain.

cystycerci of Taenia saginata in undercooked meat.

it is most commonly transmitted by cysts in water.

outer skin; keratin

True

miconazole

It is a severe illness in adults.

mefloquine

It is caused by a roundworm.

Rocky Mountain spotted fever (RMSF) is a tickborne disease caused by Rickettsia rickettsii. In the United States, there are two primary tick vectors: Dermacentor andersoni (in the western United States) and Dermacentor variablis (in the eastern United States).

the Appalachian region (North Carolina, Kentucky) In the early 1900s, settlers in the Bitterroot Valley were victim to what they called the "black measles." The infection seemed concentrated on the west side of the Bitterroot River and was fatal in four out of five cases. In 1928, the Rocky Mountain Laboratory (RML) was established in Hamilton, Montana (very near to where Paul and Ron went backpacking) to study RMSF. Residents of the area were terrified that ticks would be able to escape the facility and spread disease. Therefore, a small moat was built around the facility to help contain the ticks!

Like viruses, R. rickettsii requires a eukaryotic host in order to carry out its life cycle. In order to cause RMSF, R. rickettsii must enter host cells During infection, R. rickettsii is able to survive and replicate within eukaryotic cells.

As an obligate intracellular organism, R. rickettsii must carry out its entire life cycle within a eukaryotic cell. In order for R. rickettsii to invade cells, it has to adhere to host cells and enter. This does not require cells to multiply; remember that R. rickettsii is unable to multiply in the external environment. This means that to be grown for study in the laboratory, R. rickettsii has to be grown within host cells. During infection, R. rickettsii carries out its life cycle in host cells; in fact, it spreads from cell to cell without ever leaving the cell. It induces the formation of projections from one cell to another, allowing it to spread without ever leaving the protective environment of the host cell.

R. rickettsii is transmitted to the human host during a bite, when tick saliva enters the wound. R. rickettsii resides within the salivary glands of the Dermacentor tick. It exists in a "dormant" state until the tick feeds for an extended period of time. While the tick is biting the human, the R. rickettsii bacteria are transmitted to the human and released into the circulatory system. The transmission of R. rickettsii from the tick to the host requires at least 6 to 10 hours from the moment the tick attaches to the host.

Once introduced into the bloodstream from a tick bite, R. rickettsii will spread throughout the body via the blood/lymph system. R. rickettsii invades endothelial cells that line the vessels and remains protected from the immune system. The subsequent spread from cell to cell results in significant endothelial cell damage and increased vascular permeability. This increased permeability leads to leakage of blood from the vessels, which manifests as the macular rash. In very severe cases, the extensive damage can cause occlusion of the small vessels, leading to gangrene and possible amputation or debridement of necrotic tissue.

The symptoms of RMSF are similar to those of several other infections, making definitive diagnosis difficult. A delay in treatment can lead to complications that include respiratory, cardiac, and renal failure. Without prompt treatment, RMSF can have a mortality rate as high as 20%. Most tests that can definitively identify R. rickettsii are not very effective early in infection. Tetracyclines (particularly doxycycline) are effective in treating RMSF. It is important to treat patients suspected of RMSF immediately, because a delay in treatment may lead to serious complications from the disease, including severe neurological, ophthalmological, respiratory, gastrointestinal, and renal complications. It may also cause cardiac problems; RMSF is the only tickborne disease that can cause congestive heart failure. Prior to antibiotic treatments, mortality from RMSF was approximately 30%; today, that rate is 3% to 5%. Of the 111 cases studied in the Bitterroot Valley in the early 1900s, 69% were fatal.

Indirect FA uses an antibody that reacts with any human antibody. Indirect FA is rapid, sensitive, and specific. Indirect FA will detect R. rickettsii-specific antibodies present in the patient's serum. Indirect FA is more sensitive than direct immunofluorescent testing.

During the indirect FA assay, patient serum is mixed with a sample of R. rickettsii antigens. If the patient's serum contains R. rickettsii-specific antibodies (indicative of infection), they will bind to the antigens. These antigen-antibody complexes are then detected with a fluorescently labeled antibody specific for human immunoglobulin. Therefore, fluorescence indicates the presence of the antigen-antibody interactions. This approach is more sensitive than the direct approach (which detects the presence of antigens in the serum) for a couple of reasons. First, the level of antigens in the sample (particularly serum from RMSF patients) may be too low to detect. In addition, each step involving antibody binding represents an "amplification" of the signal as multiple antibody molecules can bind to each target. When indirect FA is used in RMSF diagnosis, samples are typically taken early in the infection and then later (2 to 4 weeks later). The early samples will usually have low levels of antibodies; however, the later samples usually show a significant increase in antibody levels.

Atlantic coast

Burkitt's lymphoma

Ascaris lumbricoides

their cells are structurally and functionally similar to human cells.

bacteria.