Microbiology | Fungal and Protozoan Diseases

color key: skin diseases (aqua), nervous system diseases (blue), cardiovascular and lymphatic diseases (purple), respiratory diseases (light pink), digestive system diseases (darker pink), reproductive system diseases (magenta)

Ringworm (Tinea infections)

1) What are Tinea corporis, Tinea cruris, Tinea capitis, Tinea unguium, and Tinea pedis?

2) How is ringworm transmitted?

3) What’s the main symptom of ringworm?

4) How is ringworm treated?

5) What is it about Tinea pedis that may make people more prone to a secondary bacterial infection?

1) Tinea corporis (ringworm of body), Tinea cruris (jock itch), Tinea capitis (ringworm of scalp), Tinea unguium (fungal nail infection), and Tinea pedis (athlete’s foot)

2) direct contact (person-to-person or animal-to-person) and indirect contact with fomites (contaminated inanimate surfaces)

3) circular lesion with white edges

4) antifungal drugs

5) intact skin (skin barrier) is damaged which makes people more prone to secondary infection

Candida albicans

1) What is Candida albicans?

2) How is it transmitted?

3) What can it cause?

4) Is it considered opportunistic?

1) Candida albicans is a yeast that’s part of the normal flora of the mouth, GI tract, and vagina; it forms pseudohyphae (chains of elongated yeast cells that remain attached after budding)

2) not transmissible, it’s an endogenous infection

3) oral thrush, cutaneous (if skin is wet all the time) or vulvovaginal candidiasis (if factors disrupt normal vaginal microbiota), vaginalis; most common cause of nosocomial fungal infections; systemic infection in immunocompromised people (like AIDS patients) which can also lead to candidiasis

4) yes

Candida auris

1) What is Candida auris?

2) How is it transmitted?

3) Are treatment and diagnosis simple?

4) Is it considered opportunistic?

1) Candida auris is a yeast that is an emerging fungal pathogen; when one comes into contact with it, it’s initially present on the skin and won’t further affect someone if they’re immunocompetent, but if they’re immunocompromised or hospitalized, they may have open wounds or medical devices contaminated with the yeast, which can enter the bloodstream and spread throughout the body

• also forms pseudohyphae

2) direct contact with infected people or surfaces, often in healthcare settings

3) not really - Candida auris is resistant to many classes of antifungals, and special methods like PCR are needed for diagnosis

4) yes

Cryptococcosis

1) What yeasts cause it?

2) How is it transmitted?

3) What can it cause?

1) Cryptococcus neoformans (most common cause; it’s an encapsulated yeast), also C. gattii and C. grubii

2) breathing in airborne spores and desiccated yeast cells (usually found in soil contaminated w/ bird droppings - the budding yeast is carried by birds)

3) lung infection (when breathed in); can disseminate through blood to CNS and cause cryptococcal meningitis; may lead to systemic infection

African Trypanosomiasis (African Sleeping Sickness)

1) What protozoa cause it?

2) How is it transmitted? What is the vector?

3) What can it cause? What happens if it’s left untreated?

4) Is there a vaccine?

1) flagellated protozoa in the genus Trypanosoma - human disease is caused by T. brucei rhodesiense or T. brucei gambiense

2) the bite of an infected tsetse fly (vector) → protozoa enters blood via bite and spreads to lymph

3) can infect all organs of the body since it spreads through blood and lymph; if untreated, deterioration of CNS occurs which can lead to coma or death

4) no vaccine - it’s difficult to make one because protozoan evades immunity via antigenic variation of surface glycoproteins (even though the body can produce antibodies, existing ones won’t be effective in combatting different strains/variations)

Visceral Leishmaniasis (Kala-azar)

1) What protozoan causes it?

2) How is it transmitted? What is the vector?

3) What does it cause?

4) Where is this disease endemic?

5) Is it considered opportunistic?

1) protozoa of genus Leishmania, mainly Leishmania donovani

• other Leishmania species can cause cutaneous leishmaniasis

2) transmitted via bite of sand fly (vector)

3) infects viscera; systemic infection (due to protozoa being taken up by macrophages, where they can multiply and circulate throughout the body); fever, anemia, swelling abdomen due to enlargement of spleen and liver; death can result if left untreated

4) tropical and subtropical regions

5) it’s considered opportunistic in HIV patients, otherwise it’s not

Malaria

1) What protozoa cause it? Which species causes the most severe disease?

2) How is it transmitted? What is the vector?

3) What does it cause?

4) How is it treated? Is there a vaccine available?

5) Is resistance an issue?

6) Where is the disease endemic? What can travelers to these regions do to protect themselves, and what future initiatives are in development?

1) protozoa of genus Plasmodium - P. falciparum causes the most severe disease because it can obstruct blood vessels

2) bite of infected female Anopheles mosquito, which carries the sporozoite stage of the protozoan that enters the bloodstream

3) characteristic fever and chills

4) artemisinin-based combination therapies (ACTs) for P. falciparum; there is a Mosquirix vaccine which offers limited protection for children, but vaccine development is challenging due to antigenic variation

5) widespread chloroquine resistance is an issue, which is why ACTs are used for treatment now

6) endemic in tropical areas - travelers should take chemoprophylaxis and vector control measures to protect themselves; a future control initiative involves genetically modifying mosquitoes to reduce transmission

Malaria

Describe the life cycle of malaria.

1) infected mosquito carrying sporozoites bites human → sporozoites enter blood through bite, then migrate to the liver via the bloodstream

2) in liver cells, sporozoites undergo schizogony (asexual reproduction) and produce merozoites (which are a type of trophozoite—trophozoites are in the actively feeding and multiplying stage of the life cycle)

3) merozoites are released from the liver (they rupture liver cells) into the blood, where they may infect red blood cells (in which they multiply)

4) in the red blood cell, the merozoite develops into the ring stage (more growth and division occur to produce more merozoites)

5) infected red blood cells rupture, releasing merozoites into the blood → some will go on to infect more red blood cells, while others will develop into male or female gametocytes

6) another mosquito bites the infected human and ingests gametocytes, which unite to form a zygote in the mosquito’s GI tract

7) sporozoites result from the zygote and travel to the mosquito’s salivary glands → they get passed on to the next human the mosquito bites and the cycle continues

Chagas disease (American Trypanosomiasis)

1) What protozoan causes it?

2) How is it transmitted? What is the vector?

3) What does it cause?

1) Trypanosoma cruzi, which is mainly found in Latin America and sporadically in the southern US

2) contaminated feces enter mucous membranes or a reduviid bug’s (kissing bug; vector) bite site; if mother is chronically infected, she can pass it on to the fetus (causing congenital effects)

3) fever, swollen glands, local swelling at bite site initially; may progress to chronic form of disease (harder to treat), which can cause damage to nerves in various organs (heart, skeletal muscles, colon)

Toxoplasmosis

1) What protozoan causes it?

2) How is it transmitted?

3) What can it cause?

1) Toxoplasma gondii

2) ingestion of oocysts from cat feces (handling cat litter) or tissue cysts in undercooked meat; can also be transmitted from mother to fetus by crossing placenta (if mother experiences her first infection during pregnancy)

3) most healthy individuals are asymptomatic or have mild lymphadenopathy (enlarged lymph nodes); immunocompromised patients may experience reactivation of tissue cysts, putting them at risk for Toxoplasmic Encephalitis; if protozoa crosses placenta and infects fetus, miscarriage or congenital defects may result

Toxoplasmosis

Describe the life cycle of toxoplasmosis.

1) immature oocyst is shed by cat in feces

2) during sporogyny, mature oocysts develop (containing 2 sporocysts, each with 4 infective sporozoites)

3) if ingested, these oocysts can infect mice, domestic animals, and humans

4) in host, sporozoites either develop into bradyzoites (divide slowly, remain dormant in body tissues for life, won’t cause immediate illness) or tachyzoites (divide quickly, obtain nutrients from environment, cause acute infection)

5) bradyzoites contain the tissue cyst form of the protozoan; these are usually ingested by cats eating mice, then the oocysts are shed in cat feces

Coccidioidomycosis (aka Valley Fever or San Joaquin Fever)

1) What fungi cause it?

2) How is it transmitted?

3) What does it cause?

4) Is it opportunistic?

5) Where is it endemic to?

1) Coccidioides immitis or C. posadasii, which are dimorphic fungi

2) inhalation of soil spores

3) mild flu-like symptoms (or no symptoms) initially; in tissues, the fungus forms a thick-walled spherule filled with spores (used for diagnosis); immunocompromised individuals are at risk for disseminated disease (can involve meninges, bones, or other organs)

4) yes

5) endemic to arid regions in southwestern US

Histoplasmosis

1) What fungus causes it?

2) How is it transmitted?

3) What does it cause?

4) Is it opportunistic?

5) Where is it endemic to?

1) Histoplasma capsulatum, a dimorphic fungus

2) inhalation of fungal spores from soil (bats can carry and excrete spores in feces) → when inhaled, they can survive and replicate inside macrophages

3) usually remains mild and localized within lungs; in immunocompromised patients, it can disseminate to spleen, liver, lymph nodes, and other organs or may cause pneumonia or other severe disease

4) yes

5) endemic to central and eastern US

Pneumocystis Pneumonia (PCP)

1) What fungus causes it?

2) How is it transmitted?

3) What does it cause?

4) Is it opportunistic?

5) How is it treated?

1) Pneumocystis jirovecii

2) airborne; fungus attaches to alveolar cells

3) asymptomatic in healthy individuals (they’re carriers); inflammation in immunocompromised individuals; death if untreated (high fatality rate)

4) yes

5) it has a unique structure so traditional antifungals aren’t effective → needs to be treated w/ specific antimicrobial agents, like TMP-SMX (trimethoprimasulfamethoxazole) or folic acid synthesis inhibitors

Blastomycosis

1) What fungus causes it?

2) How is it transmitted?

3) What does it cause?

4) Is it opportunistic?

1) Blastomyces dermatidis, a dimorphic fungus

2) breathing spores (found in moist soil rich with organic matter) into lungs, or direct inoculation into a wound (rare)

3) pneumonia (spores mature into yeast cells in lungs); systemic blastomycosis (if yeast cells spread through blood and disseminate to other organs, like skin, bone, and genitourinary tract) can lead to extensive tissue damage

4) no

Aspergillosis

1) What fungus causes it?

2) How is it transmitted?

3) What does it cause?

4) Is it opportunistic?

1) Aspergillus fumigatus and other Aspergillus species

2) inhalation of spores (found in compost piles and decaying vegetation)

3) allergic reactions in people with pre-existing respiratory conditions (asthma, cystic fibrosis, etc.); invasive aspergillosis occurs when inhaled spores infect lungs (mainly in immunocompromised individuals)

4) yes

Pulmonary cryptococcosis

1) Which fungi cause it?

2) How is it transmitted?

3) What does it cause?

4) Is it opportunistic?

1) Cryptococcus neoformans or C. gattii

2) inhalation of microscopic fungal spores from environment (soil, bird droppings, tree debris)

3) may manifest as pneumonia; in healthy individuals, it’s mild or asymptomatic; in immunocompromised individuals (or if the initial lung infection isn’t contained), fungus can disseminate via blood stream and infect nervous system, causing meningitis

4) yes

Giardiasis

1) Which protozoan causes it?

2) How is it transmitted?

3) What does it cause?

4) Is it resistant to chlorination?

1) Giardia duodenalis (aka G. intestinalis or G. lamblia)

2) fecal-oral; cysts of organisms ingested via contaminated water, food, or hands

3) severe, foul, and greasy diarrhea (in small intestine, cysts transform into trophozoites; these then adhere to the bowel wall and resist getting flushed out with regular bowel movements); interrupts normal absorption (especially of lipids)

4) yes, cysts are resistant to standard chlorination so special decontamination measures need to be implemented for effective prevention (boiling, filtration, good hygiene)

Cryptosporidiosis

1) Which protozoa cause it?

2) How is it transmitted?

3) What does it cause?

4) Is it resistant to chlorination?

1) protozoa of genus Cryptosporidium, primarily C. hominis and C. parvum

2) fecal-oral; ingestion of oocysts (that mature into sporozoites in small intestine)

3) mild, self-limited, profuse diarrhea in immunocompetent individuals; chronic, severe, or life-threatening diarrhea in immunocompromised individuals

4) yes, oocysts are highly resistant to chlorine (and are leading cause of recreational waterborne disease outbreaks in US)

Amebiasis (Amoebic Dysentery)

1) Which protozoan causes it?

2) How is it transmitted?

3) What does it cause?

4) Is it resistant to chlorination?

1) Entamoeba histolytica, an amoeba that can lyse blood cells in tissues

2) fecal-oral; ingestion of cysts (that develop into trophozoites in colon) via contaminated food or water

3) dysentery and abdominal pain (trophozoites in colon can invade intestinal mucosa); in severe cases, trophozoites may enter peritoneal cavity or bloodstream, leading to peritonitis or dissemination; people can be asymptomatic carriers but still transmit the parasite and are at risk of developing clinical disease

4) yes, cysts are resistant to standard chlorination

Cyclosporiasis

1) Which protozoa causes it?

2) How is it transmitted?

3) What does it cause?

4) Is it resistant to chlorination?

1) Cyclospora cayetanensis, which is found in tropical or subtropical regions

2) fecal-oral; oocytes (may be found in imported fresh produce, like cilantro, basil, raspberries, and leafy greens) are ingested

3) watery diarrhea

4) yes, oocytes are highly resistant to standard water chlorination

Vulvovaginal Candidiasis

1) What yeast causes it?

2) What factors contribute to it?

3) Is it an opportunistic infection?

1) Candida albicans (overgrowth of it; it’s endogenous)

2) factors disrupting vaginal microbiota/immunity → uncontrolled diabetes, altered vaginal pH, hormonal changes, prolonged antibiotic therapy

3) yes, it’s an endogenous infection caused by the overgrowth of a yeast normally present in the body

Trichomoniasis

1) What protozoan causes it?

2) How is it transmitted?

3) What does it cause?

1) Trichomonas vaginalis

2) sexually transmitted

3) infection of urogenital tract surface in all who are infected; men are usually asymptomatic; women usually experience irritation and profuse, frothy, greenish-yellow, foul odor discharge

Which of the following diseases is transmitted to humans via the bite of an infected tsetse fly?

A) Visceral Leishmaniasis

B) Malaria

C) Chagas Disease

D) African Trypanosomiasis

D) African Trypanosomiasis

A patient with AIDS develops a severe pneumonia that is unresponsive to standard antifungal drugs. The nurse anticipates treatment with Trimethoprim-sulfamethoxazole (TMP-SMX) based on the likely diagnosis of:

A) Blastomycosis

B) Coccidioidomycosis

C) Pneumocystis Pneumonia

D) Invasive Aspergillosis

C) Pneumocystis Pneumonia (PCP)

A hospitalized, immunocompromised patient contracts a systemic fungal infection that is causing widespread concern due to its known resistance to multiple drug classes. This highly resistant emerging pathogen is:

A) Blastomycosis dermatitidis

B) Trichomonas vaginalis

C) Cryptococcus neoformans

D) Candida auris

D) Candida auris

The nurse is counseling a pregnant patient who frequently gardens and has several cats. To prevent infection with the pathogen that can cross the placenta and cause congenital defects, the patient must be educated primarily on avoiding exposure to:

A) Tsetse flies

B) Reduviid bugs

C) Aspergillus spores in compost

D) Oocysts from cat feces

D) Oocysts from cat feces

Which protozoan infection(s) pose(s) a risk for vertical (congenital) transmission from a chronically infected mother to her fetus?

A) Giardia duodenalis

B) Leishmania donovani

C) Trypanosoma cruzi

D) Toxoplasma gondii

E) Cryptosporidium hominis

C) Trypanosoma cruzi & D) Toxoplasma gondii

The widespread development of resistance to which antimicrobial drug is the primary reason why Artemisinin-based Combination Therapies (ACTs) are now the standard treatment for Plasmodium falciparum malaria?

A) Metronidazole

B) Fluconazole

C) Chloroquine

D) Trimethoprim-sulfamethoxazole

C) Chloroquine

Vaccine development for African Trypanosomiasis and Malaria has been particularly challenging due to the ability of the parasites to evade the host immune system through:

A) A protective capsule

B) Intracellular replication

C) Cyst/oocyst formation

D) Antigenic variation of surface glycoproteins

D) Antigenic variation of surface glycoproteins

A patient who recently traveled to a tropical region presents with periodic fevers and chills that occur simultaneously with the rupture of infected red blood cells (RBCs). This classic symptom triad is diagnostic for:

A) African Trypanosomiasis (Sleeping Sickness)

B) Giardiasis

C) Coccidioidomycosis (Valley Fever)

D) Malaria

D) Malaria

During assessment, the nurse notes that a female patient's discharge is profuse, frothy, greenish-yellow, and foul-smelling. This symptom is most characteristic of which sexually transmitted protozoan infection?

A) Trichomoniasis

B) Vulvovaginal Candidiasis

C) Amebiasis

D) Chagas disease

A) Trichomoniasis

A patient with Malaria begins to experience the characteristic cycles of high fever and chills. This clinical manifestation is directly caused by which stage of the Plasmodium life cycle, as it ruptures host cells?

A) Oocyst stage multiplying on the gut wall of the mosquito.

B) Trophozoite stage multiplying inside the red blood cell (RBC).

C) Cyst stage found in the environment and ingested via contaminated water.

D) Gametocyte stage being taken up by a biting mosquito.

B) Trophozoite stage multiplying inside the red blood cell (RBC).

Match the following terms to the best possible definitions:

Terms:

Zygote
Oocyst
Cyst
Trophozoite

Definitions:

1) A hardy, spore-like stage containing zygotes, often shed into the environment
2) The active, motile, feeding stage inside the host, often responsible for causing disease symptoms
3) A dormant, protective stage that allows some protozoa to survive harsh conditions and transmit between hosts
4) The fertilized cell formed after sexual reproduction in protozoa

Zygote — The fertilized cell formed after sexual reproduction in protozoa

Oocyst — A hardy, spore-like stage containing zygotes, often shed into the environment

Cyst — A dormant, protective stage that allows some protozoa to survive harsh conditions and transmit between hosts

Trophozoite — The active, motile, feeding stage inside the host, often responsible for causing disease symptoms

Match the following terms to the best possible definitions:

Terms:

Merozoite
Trophozoite (“The Ring Form”)
Gametocyte
Sporozoite

Definitions:

1) Inside RBCs, which is the sexual stage of the parasite that can be ingested by a mosquito to continue the life cycle
2) Released from RBCs, triggers the inflammatory response, causing the classic cyclical fever, chills, and sweats
3) The infective stage for the human, which is injected by the mosquito and travels to the liver
4) Inside RBCs, which is an immature, feeding stage; most common form seen on a blood smear for diagnosis (microscopy)

Merozoite — Released from RBCs, triggers the inflammatory response, causing the classic cyclical fever, chills, and sweats

Trophozoite — Inside RBCs, which is an immature, feeding stage; most common form seen on a blood smear for diagnosis (microscopy)

Gametocyte — Inside RBCs, which is the sexual stage of the parasite that can be ingested by a mosquito to continue the life cycle

Sporozoite — The infective stage for the human, which is injected by the mosquito and travels to the liver

Match the following terms to the best possible definitions:

Terms:

Yeast
Mold
Dimorphic fungus
Dermatophytes

Definitions:

1) Mold in environment (25º C), yeast in host (37º C)
2) Unicellular (oval/spherical), seen in environment and human tissue
3) Multicellular (thread-like hyphae), mostly seen in environment (lower temperature)
4) A group of specialized molds (filamentous fungi) that cause common superficial fungal infections of the skin, hair, and nails

Yeast — Unicellular (oval/spherical), seen in environment and human tissue

Mold — Multicellular (thread-like hyphae), mostly seen in environment (lower temperature)

Dimorphic fungus — Mold in environment (25º C), yeast in host (37º C)

Dermatophytes — A group of specialized molds (filamentous fungi) that cause common superficial fungal infections of the skin, hair, and nails

Giardiasis and Cryptosporidiosis are the two most common intestinal parasitic infections and leading causes of waterborne disease outbreaks in the United States.

Which symptoms are associated with Giardia duodenalis, and which are associated with Cryptosporidium parvum/C. hominis?

1) Fatty, foul-smelling, loose stools; can lead to malabsorption and weight loss if untreated
2) Profuse, watery diarrhea; can lead to significant dehydration

Giardiasis (G. duodenalis) → Fatty, foul-smelling, loose stools; can lead to malabsorption and weight loss if untreated

Cryptosporidiosis (C. parvum, C. hominis) → Profuse, watery diarrhea; can lead to significant dehydration