Micro HW
Dermatophytes are fungi that can infect the __________ because they can grow on/in __________.
oil glands; sebum mouth; saliva x outer skin; keratin vagina; mucosal secretions
Scabies is a skin disease caused by a
protozoan. prion. x mite. bacterium. slow virus.
Infants may acquire a serious form of conjunctivitis during birth if they are born to a mother infected with __________.
Acanthamoeba species Chlamydia trachomatis Haemophilus influenzae x Neisseria gonorrhoeae
Which statement concerning viral structure is true?
Animal viruses usually contain tail sheaths and spikes. x Spikes are found on some viruses. They are very consistent in structure and can be used for identification. The proteins in the envelope are capsomeres. All viruses contain an envelope, which is made of lipid, carbohydrate, and protein. Some enveloped viruses have spikes, and they can be used for identification, such as the H and N spikes on the influenza virus.
In which of the following North American locations would you expect to find the highest incidence of infection with Borrelia burgdorferi?
Colorado x Atlantic coast Pacific coast Gulf of Mexico The northern part of the East Coast has the highest incidence of Lyme disease.
What is the correct sequence of events for the replication of a DNA virus?
Correct! Viruses depend on host cells for replication. The herpes zoster virus is a DNA virus. It enters the host cell by attaching to host cell receptors. Once inside, the virion is uncoated to release the DNA into the nucleus of the host cell. "Early" genes, typically used for viral replication, are transcribed using the host's RNA polymerase. Viral DNA is then replicated to produce multiple copies of the DNA. The remaining components of a virion are the produced via transcription and translation of "late" genes. Capsid proteins then migrate to the nucleus of the host cell. Maturation occurs when the capsid proteins and viral DNA combine to form a complete virus. The virions are then released from the host cell to go and infect new host cells. Image C diagrams the replication of papovavirus, a DNA virus similar to herpesvirus.
Why is vaccination for rubella recommended?
Health care workers have a high incidence of infection. x There is a high incidence of congenital infections and birth defects. Death from secondary infections is common. It is no longer recommended; rubella has been eradicated. It has a high mortality rate in school-age children.
An indirect immunofluorescence assay is described as the CDC "gold standard serological test" for RMSF. Keeping in mind the principles behind indirect fluorescent-antibody (indirect FA) testing, which of the following characteristics contributes to its choice as the gold standard?
Indirect FA will detect antigens present in the patient's serum. x Indirect FA is rapid, sensitive, and specific. Indirect FA requires an antibody that is specific for R. rickettsii. x Indirect FA will detect R. rickettsii-specific antibodies present in the patient's serum. x Indirect FA uses an antibody that reacts with any human antibody. x 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. It may seem counterintuitive, but the indirect method is typically more sensitive than the direct assay. The direct method is based on the presence of R. rickettsii antigens in the serum; these levels are usually very low. In contrast, the level of antibodies increases during the infection, making them more likely to be detected.
RMSF results from the interactions that occur between the R. rickettsii pathogen and the host. The infection results from a coordinated series of events that ultimately result in diseas
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.
Thrush and vaginitis are caused by
Staphylococcus aureus. herpesvirus. Chlamydia trachomatis. Streptococcus pyogenes. x Candida albicans.
A 17-year-old boy has pus-filled cysts on his face and upper back. Microscopic examination reveals gram-positive rods. This infection is caused by
Staphylococcus aureus. x Propionibacterium acnes. herpes simplex virus. Acanthamoeba. Streptococcus pyogenes.
How are viruses different from cells?
They do not contain genetic material. They do not contain enzymes. x They require a host in order to reproduce. They do not contain protein.
What is the function of the structural elements of a virus?
To use all of the cell proteins To provide a source of energy for the virus x To package and protect the viral genome
Which of the following is true regarding cultivation and isolation of animal viruses?
Viruses can be easily grown in liquid culture without any other organisms present. Mouse models are available for virtually all human viral infections and can be routinely used for vaccine development. The preferred and widely used method of viral isolation and growth is via growth in an embryonated egg. x Diploid cell culture lines, developed from human embryos, are widely used for culturing viruses that require a human host. Cell culture produces the most reproducible results.
Which of the following statements concerning viruses is true?
Viruses possess enzymes for protein synthesis and ATP generation. Viruses contain both DNA and RNA, and they undergo binary fusion. Viruses are usually about the same size as bacteria. x The "host range" for a virus is determined by the presence or absence of particular components on the surface of a host cell that are required for the virus to attach. Attachment of the virus to the host cell (the first step in the viral life cycle) requires binding of complementary molecules on the virus and host cell.
A patient has a skin ulcer from which a gram-negative bacillus is cultured. This patient has regional lymph nodes that are enlarged and filled with pockets of pus. He reports keeping pet rabbits. Which of the following is a possible diagnosis? A patient has a skin ulcer from which a gram-negative bacillus is cultured. This patient has regional lymph nodes that are enlarged and filled with pockets of pus. He reports keeping pet rabbits. Which of the following is a possible diagnosis?
anthrax relapsing fever x tularemia puerperal sepsis This disease is also known as "rabbit fever."
Which disease, resulting in damage to the heart muscle or the nerves controlling peristalsis in the gastrointestinal tract, is transmitted by the reduviid bug?
babesiosis malaria x Chagas' disease leishmaniasis This disease is caused by Trypanosoma cruzi.
What disease does the human herpesvirus-1 cause?
canker sores chancres x cold sores or fever blisters infectious mononucleosis Correct! Cold sores or fever blisters are the painful, short-lived vesicles that form near the outer margins of the lips. It is transmitted via oral and respiratory routes. In the United States, a large percentage of the population is infected with this virus during infancy, when the virus is passed via respiratory droplets from family members. (Who can resist kissing a baby?)
Which virus is NOT associated with cancer?
human papillomavirus (HPV) Epstein-Barr virus (EBV) hepatitis B virus (HBV) x coronavirus Coronaviruses are not known to cause cancer. They are one cause of the common cold.
The development of which disease is promoted by mosquito-borne malarial infections?
infectious mononucleosis ("mono") Hodgkin's disease cytomegalovirus (CMV) infection x Burkitt's lymphoma This disease is common in areas with endemic malaria and is transmitted by the Epstein-Barr virus.
Koplik spots are a diagnostic indicator of
smallpox. x measles. fifth disease. chickenpox. rubella.
Staphylococcus aureus is responsible for all of the following EXCEPT
sties. carbuncles. boils. pimples. x acne.
A possible complication of chickenpox is
subacute sclerosing panencephalitis. fever blisters. congenital rubella syndrome. x encephalitis. macular rash.
What part of the United States is endemic for RMSF?
the Northeast region, particularly along the Atlantic Coast the Rocky Mountain region, including Montana, Wyoming, and Colorado the Gulf Coast region (i.e., states that border the Gulf of Mexico) x 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!
All of the following are protective factors of the skin and its secretions EXCEPT
tightly packed cells. lysozyme production. salt. keratin. x pyocyanin production.
Which of the following cell populations become plasma cells?
x B cells buboes fixed macrophages T cells
Warts are caused by
x papillomavirus. herpesvirus. poxvirus. Staphylococcus aureus. parvovirus.
Cats have been identified as an essential part of the life cycle for the protozoan that causes which disease?
x toxoplasmosis babesiosis Chagas' disease malaria Toxoplasmosis is caused by Toxoplasma gondii.
Which of the following statements correctly describes the disease schistosomiasis?
x It can cause a variety of different problems, including urinary, intestinal, and neurological symptoms, depending on the particular species. This disease causes illness, but it is usually self-limiting and not fatal. Soil is the reservoir. There is no treatment. Schistosomiasis is a debilitating disease caused by a small fluke.
Which of the following is true of viroids?
x Viroids are short pieces of naked RNA. Viroids are typically extremely long and contain numerous genes. Viroid is the term for a virus that infects plants. There are similarities between the base sequences of viroids and exons, resulting in the hypothesis that viroids evolved from exons. Viroids are infectious particles consisting of only a short piece of "naked" RNA.
Rickettsia rickettsii is a gram-negative, obligate intracellular pathogen. Which of the following statements about the R. rickettsii life cycle is FALSE?
During infection, R. rickettsii is able to survive and replicate within eukaryotic cells. 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. x After entering a host, R. rickettsii multiplies to levels high enough to successfully invade cells and establish an infection. 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.
Which region of the skin supports the largest bacterial population?
forearms x armpits feet scalp All of these support similarly sized bacterial populations.
Which of the following is a characteristic of biological transmission from Dermacentor to a human host?
x R. rickettsii is transmitted to the human host during a bite, when tick saliva enters the wound. The human host is infected after drinking water contaminated with Dermacentor eggs. R. rickettsii is transmitted to the human host after the human consumes food that the tick has contacted. R. rickettsii is transmitted to the human after the human drinks water that has been contaminated by feces from an animal infected with Dermacentor spp. 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.
The IV regimen administered by Ron's doctors is consistent with the CDC's recommendation that doxycycline be administered when RMSF is suspected. Apply your knowledge of RMSF to choose the most likely reasons behind this recommendation.
x The symptoms of RMSF are similar to those of several other infections, making definitive diagnosis difficult. x A delay in treatment can lead to complications that include respiratory, cardiac, and renal failure. x Without prompt treatment, RMSF can have a mortality rate as high as 20%. At the very least, treatment with doxycycline will slow the progress of the infection and allow the physicians adequate time to make a definitive diagnosis. Doxycycline is an effective treatment for most infections transmitted by vectors. x 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.
The greatest single cause of blindness in the world is
x trachoma. inclusion conjunctivitis. neonatal gonorrheal ophthalmia. keratoconjunctivitis. pinkeye.