Lecture 2.1, EXAM 3

Question 1

What is HBsAg?

Answer 1

(Hepatitis B surface antigen) - A “positive” or “reactive” HBsAg test result means that the person is infected with hepatitis B. This test can detect the actual presence of the hepatitis B virus (called the “surface antigen”) in your blood. If a person tests “positive,” then further testing is needed to determine if this is a new “acute” infection or a “chronic” hepatitis B infection. A positive HBsAg test result means that you are infected and can spread the hepatitis B virus to others through your blood.

Question 2

What is anti-HBs or HBsAbs?

Answer 2

(Hepatitis B surface antibody) - A “positive” or “reactive” anti-HBs (or HBsAb) test result indicates that a person is protected against the hepatitis B virus. This protection can be the result of receiving the hepatitis B vaccine or successfully recovering from a past hepatitis B infection. This test is not routinely included in blood bank screenings. A positive anti-HBs (or HBsAb) test result means you are “immune” and protected against the hepatitis B virus and cannot be infected. You are not infected and cannot spread hepatitis B to others

Question 3

What is anti-HBc or HBcAb?

Answer 3

(Hepatitis B core antibody) - A “positive” or “reactive” anti-HBc (or HBcAb) test result indicates a past or current hepatitis B infection. The core antibody does not provide any protection against the hepatitis B virus (unlike the surface antibody described above). This test can only be fully understood by knowing the results of the first two tests (HBsAg and anti-HBs). A positive anti-HBc (or HBcAb) test result requires talking to your health care provider for a complete explanation of your hepatitis B status.

Question 4

Parasite:
* What type of organism?
* Gets food from what?
* Causes what?
* What are the three classes?

Answer 4

• An organism that lives on or in a host organism
• Gets its food from or at the expense of its host
• Cause tremendous burden of disease in tropics/subtropics
• Three main classes of parasites that can cause disease in humans: Protozoa, Helminths, Ectoparasites

Question 5

Ectoparasites:
* used to refer to what?
* More broadly can include what?
* Important as what?

Answer 5

• Used to refer to organisms such as ticks, fleas, lice, and mites
• More broadly can include blood sucking arthropods such as mosquitos
• Important as vectors, transmitters of many different pathogens

Question 6

Helminths:
* What type of organism?
* Can be either what?
* What are the 3 main groups?

Answer 6

Large multicellular organisms that are generally visible to the naked eye in their adult stage

Helminths can be either free-living or parasitic in nature

3 main groups
* Flatworms- flukes and tapeworms
* Thorny-headed worms
* Round worms

Question 7

Answer 7

Question 8

Protoza:
* What type of organism?
* What can it do that controbutes to their survival rate
* Can be transmitted via what?
* Can be classifed how?

Answer 8

• Microscopic, one celled organisms that can be free living or parasitic in nature
• Can multiply in humans which contributes to their survival and permits serious infection
• Protozoa can be transmitted via an arthropod vector such as mosquito
• Protozoa that are infectious to humans can be classified into four groups based on their mode of movement

Question 9

Protozoa that are infectious to humans can be classified into four groups based on their mode of movement, list them

Answer 9

• Sarcodina – the ameba
• Mastigophora – the flagellates
• Ciliophora – the ciliates
• Sporozoa – organisms whose adult stage is not motile

Question 10

Giardia:
* Caused by what?
* Infected animals excrete what?
* What causes human infection?
* Cysts undergo excystation within what? What do they release?
* Protozoa disrupt what?

Answer 10

• Caused by the protozoa Giardia duodenalis
• Infected animals excrete cysts into freshwater, where they are immediately infective and can exist for weeks to months
• Ingesting cysts through contaminated water or person-to-person direct contact causes human infection
• Cysts undergo excystation within the intestinal system and subsequently release trophozoites
• Protozoa disrupt small intestine epithelial cell junctions as well as brush border enzymes

Question 11

Giardia:
* What plays a role in transmission?
* Most common what?
* Half of infected ppl are what?
* Symptomatic?
* Typical scenario?

Answer 11

• Inadequate hygiene and sanitation play a vital role in transmission
• Most common enteric protozoal infection worldwide
• Nearly half of infected individuals are asymptomatic
• Symptomatic: onset is typically 1-2 weeks after infection- abdominal pain, nausea, flatulence, and large volume watery, foul- smelling, greasy stools
• Typical scenario: international travelers, wilderness travelers, daycare workers

Question 12

Trichomonas Vaginalis:
* Motile organism with what?
* Releases what?
* Common cause of what?
* T. Vaginitis rates in the US are what?

Answer 12

• Motile organism with at least 4 flagella that provide motility
• Releases cytotoxic proteins that destroy the epithelial lining
• Common cause of symptomatic vaginitis in women
• T. Vaginitis rates in the US are higher than combining Neisseria gonorrhoeae and Chlamydia trachomatis infection rates

Question 13

Trichomoniasis:
* What type of organism? Where does it live?
* Men vs women?
* Trich increases the risk of what?
* How is it transmitted?

Answer 13

Question 14

Trypanosoma cruzi:
* What type of disease? What does it cause?
* How does it spread?

Answer 14

A zoonotic disease caused by the parasite Trypanosoma cruzi – causes Chagas disease

Vector-borne illness spread by the triatomine bug
* Transmitted through contact with contaminated feces/urine of the reduviid bug
* The bug carries the parasite
* Other ways: blood transfusion, consumption of infected food or drink

Question 15

Trypanosoma cruzi:
* Most commonly seen where?
* Female bug takes blood to do what?
* As it takes its meal or after, the bug does what?
* The parasite then enters through what?

Answer 15

Question 16

What is romana sign? What is it associated with?

Answer 16

• Romaña sign, also known as the periorbital swelling syndrome, refers to periorbital swelling, palpebral edema and conjunctivitis seen 1-2 weeks following infection with Trypanosoma cruzi(causative agent in Chagas disease). When present it is diagnostic of acute Chagas disease.
• Romaña sign is associated with ipsilateral regional lymphadenopathy.

Question 17

Entamoeba histolytica:
* protozoan that causes what?
* Transmitted by what?
* Countries with high infection rate?

Answer 17

• Protozoan that causes intestinal amebiasis
• Transmitted by the ingestion of amebic cysts through fecal-oral contact, usually through contaminated food or water sources
• Countries with high infection rate: India, Africa, Mexico, Central and South America

Question 18

Entamoeba histolytica:
* The pathogenesis of infection by trophozoites is due to what?
* These cytokines and inflammatory mediators subsequently attract what and cause?
* The pathological range includes what?
* Extra-intestinal complication?

Answer 18

Question 19

Plasmodium:
* What does it cause? How is it transmitted?
* How many people contract malaria annually?
* Malaria is caused by what?
* Gold standard for malaria diagnosis is what?

Answer 19

• Malaria is a parasitic infection transmitted by the Anopheles mosquito that leads to acute life threatening disease
• 2 billion people contract malaria annually
• Caused by the Plasmodium parasite (different species for different regions) – has multi stage life-cycle which creates the classic “malarial paroxysm” – rigors, fevers, diaphoresis for 48 hours and then a drop to normal body temperature – cyclical
• Gold standard for malaria diagnosis is a microscopic evaluation of Giemsa- stained thin smear of venous blood

Question 20

Plasmodium:
How does the infection happen in the body?

Answer 20

Question 21

Toxoplasmosis:
* Caused by what?
* Can infect who?
* Members of what are the definitive hosts?
* What is needed to control acute or chronic infections?
* Low CD4 counts in AIDS causes what?
* Presents with what?
* What stain do you use?

Answer 21

Question 22

Toxoplasmosis:
* How does it have complex life cycle?
* How does it occur through?
* What should pregnany women not be doing?

Answer 22

Has complex life cycle requiring a definitive host and an intermediate host to complete sexual and asexual cycles

Occurs through:
* ingestion of tissue cysts via improperly cooked/raw meat
* ingestion of oocysts via contaminated with feline feces in food and water
* Vertical transmission – infected mother causes congenital infection through the placenta

Pregnant women should not change cat litter

Question 23

Cryptosporidiosis:
* Protozoan infection with what?
* The two main strains that causes disease are what?
* How does it transfer? What are common way?

Answer 23

Protozoan infection with the coccidian parasites

The two main strains that causes disease are Cryptosporidium hominis (more urban areas) and Cryptosporidium parvum (more rural areas)

Contaminated water sources or fecal-oral transfer frequently spread the organism
* Outbreaks in the US have been associated with contamination of recreational or municipal water supplies
* Daycares – kids are gross!

Question 24

Cryptosporidiosis:
* Once ingested the oocyst (how it lives in the environment) travels where and does what?
* What does it infect?
* What does it present as?

Answer 24

• Once ingested the oocyst (how it lives in the environment) travels to the small intestine and undergoes asexual multiplication.
• Infect the brush border of the intestinal epithelium as opposed to deeper tissue
• Presents as profuse watery diarrhea and wasting due to malabsorption

Question 25

What is the Second major cause of moderate to severe diarrhea in children younger than 2

Answer 25

Cryptosporidiosis

Question 26

Answer 26

Question 27

Answer 27

Question 28

Fungus?

Answer 28

Eukaryotic organisms found in the form of yeasts, molds, or dimorphic fungi

Question 29

Fungus:
* What type of organism?
* Found where?
* Fungi are subdivided based on what?

Answer 29

• Single celled or very complex multicellular organism
• Found in just about any habitat but most live on the land, mainly in the soil or on plant material
• Fungi are subdivided on the basis of their life cycles, the presence or structure of their fruiting body and the arrangement of and type of spores they produce

Question 30

3 major groups of fungi are:

Answer 30

• Multicellular filamentous molds
• Macroscopic filamentous fungi the form large fruiting bodies (ex. Mushrooms)
• Single celled microscopic yeasts

Question 31

Histoplasmosis:
* What type of fungi? Present where?
* How is it a soil based fungus?
* What happens when the soil is disturbed?
* At body temperature it is what? BUT at 25 degrees C it is what?
* The lung tissue response to the invasion is what?
* Granulomatous inflammation results in what?

Answer 31

Question 32

Aspergillosis:
* What type of fungi? What does it cause?
* How many species that causes human disease?
* Should be thought of as what?
* Overwhelmingly affects what community?

Answer 32

• Filamentous fungus that primarily causes infection in immunocompromised hosts and individuals with underlying pulmonary disease – higher in areas with disturbed soil
• 24 species of capable of causing human disease
• Should be thought of as a spectrum of processes that vary widely depending on the host’s immune system
• Overwhelmingly affects the immunocompromised population (ex. AIDS) – invasive pulmonary aspergillosis can be life threatening

Question 33

Aspergillosis:
* Transmission is via what?
* In immunocompetent person they what?
* What cell is the most important immune cell in response against Aspergillus species

Answer 33

• Transmission is via aspiration of conidia – but most people who inhaled conidia won’t contract aspergillosis due to immune response
• In immunocompetent person they inhale conidia and are taken up by phagocytes in the lungs
• Neutrophils are the most important immune cell in response against Aspergillus species

Question 34

3 major types of bronchopulmonary aspergillosis?

Answer 34

Question 35

Candidiasis:
* a form of what?
* Occurs most commonly as what?
* Many forms of candida species including what?

Answer 35

• A form of yeast that causes an opportunistic infection
• Occurs most commonly as a secondary infection in immunocompromised individuals
• Many forms of Candida species including: C. albicans

Question 36

Candidiasis:
* Vaginal colonization increases in what?
* Oral candidiasis is very closely associated with who?
* Infants get thrush initially- this becomes less common as what?

Answer 36

• Vaginal colonization increases in diabetes mellitus, pregnancy, and the use of oral contraceptives
• Oral candidiasis is very closely associated with HIV patients – more than 90% of patients with HIV present with candidiasis
• Infants get thrush initially- this becomes less common as the acquisition of normal microbiota prevents the overgrowth of yeast

Question 37

Candidiasis:
* Common inhabitants in what?
* Oral candidiatis?
* Chronic hyperplastic candidiatis?
* Vaginal candidiasis?

Answer 37

Common inhabitants in the oral cavity, gastrointestinal tract, vagina, or penis
* Oral candidiasis – called thrush, causes white patches on the tongue, throat, and other mouth areas- when wiped away has underlying erythematous area
* Chronic hyperplastic candidiasis AKA candida leukoplakia presents with firm white persistent plaques on lips, tongue, and buccal mucosa
* Vaginal candidiasis – genital itching, burning, and a white ”cottage cheese-like” discharge. Penis less commonly affected by yeast infection

Question 38

Candidiasis:
* Vaginal colonization increases in who?
* Candida albicans is normally found in where? But usually does not what?

Answer 38

• Vaginal colonization increases in diabetes mellitus, pregnancy, and the use of oral contraceptives
• Candida albicans is normally found in the vagina but does not usually cause disease because the acidic pH created by the lactobacilli prevents their overgrowth

Question 39

Cryptococcus:
* What type of fungi?
* Commonly found where?
* Infection occurs through what?

Answer 39

• An invasive fungus that causes Cryptococcosis
• Commonly found in soil contaminated by bird droppings and in decaying wood and in tree hollows
• Infection occurs through the inhalation of spores from the environment

Question 40

Cryptococcus:
* What is the most common clinical manifestation of the infection?
* Cryptococcus is commonly associated with what?
* What are two common species?
* Patients experience what?

Answer 40

• Despite lung being the common site where the pathogen enters the body, meningoencephalitis is the most common clinical manifestation of the infection
• Cryptococcus is commonly associated with immunosuppressive individuals while being rate in healthy individuals
• 2 common species: Cryptococcus neoformans (infection in immunosuppressive patients) and Cryptococcus gatti (immunocompetent patients)
• Patients experience fever, headache, malaise, photophobia, and neck stiffness

Question 41

Pneumocystis jiroveci:
* Was initially thought to be a member of what?
* Fungal infection that most commonly affect who?
* Symptoms?

Answer 41

• Was initially thought to be a member of the protozoan class, but reclassified as a fungus in 1988
• Fungal infection that most commonly affect the immunocompromised person
• At risk: HIV, cancer, transplant, immunosuppressive medications
• Symptoms: fever, cough, dyspnea, and in severe cases respiratory failure

Question 42

Pneumocystis jiroveci:
* Tranmitted via?
* Has a preference for what?
* The hosts inflammatory response causes what?
* The most common and serious opportunistic infection in patients with what?

Answer 42

• Transmitted person to person via airborne route
• Has preference for infecting the lung of at-risk individuals – attaches to the Type I alveolar epithelium
• The hosts inflammatory response causes significant lung injury and impaired gas exchange, leading to respiratory failure
• The most common and serious opportunistic infection in patients with AIDS u AIDS defining illness