Fungal and Parasitic Infections - PathoPharm Exam 3

Fungi

-diverse, eukaryotic organisms that include molds, yeasts, and mushrooms that cause infection through spores or yeast budding

-non-pathogenic but can become opportunistic pathogens.

Superficial infections

Athlete's foot, ringworm, and oral thrush

Systemic infections

Candidiasis, Aspergillosis, Cryptococcosis.

Endemic mycoses

Histoplasmosis, Coccidioidomycosis

Allylamines

inhibit squalene epoxidase → block

ergosterol synthesis → disrupt fungal cell membrane.

• Terbinafine (dermatophytes)

Azoles

inhibit ergosterol synthesis → disrupt fungal membranes

• Fluconazole, Itraconazole, Clotrimazole, Ketoconazole

Polyenes

bind ergosterol → membrane pores → fungal cell death

• Amphotericin B (systemic)

• Nystatin (topical / mucosal)

Echinocandins

inhibit β-1,3-D-glucan → block fungal cell

wall synthesis

• Caspofungin, Micafungin, Anidulafungin

Risk factors of fungal infections

Immunocompromised state → HIV/AIDS, chemotherapy, transplant, long-term corticosteroids

• Chronic disease → diabetes, cancer, malnutrition

• Healthcare exposure → central lines, ICU stay, prolonged hospitalization

• Disruption of normal flora → broad-spectrum antibiotic use

Healthy vs. Immunocompromised in fungal infections

Healthy immune systems → infections usually localized and mild (skin, nails, mucosa)

• Immunocompromised patients → infections more frequent, severe, and invasive

Clinical impact of fungal infections

Opportunistic fungi may spread from lungs → bloodstream → CNS or organs

• Systemic fungal infections can progress rapidly and may be fatal without treatment

Major categories of fungal infections

Dermatophytes, Endemic mycoses, Opportunistic fungi, Invasive/systemic infections

Dermatophyte Infections

• Causes: fungi that infect keratinized tissues (skin, hair, nails)

• usually occur in healthy individuals and remain superficial

• Common Infections

1. Tinea pedis: athlete’s foot; itching, scaling between toes

2. Tinea corporis: ringworm; circular rash on skin

3. Tinea capitis: scalp infection; hair loss, scaling

4. Tinea cruris: “jock itch”; groin infection

5. Tinea unguium: onychomycosis → fungal infection of nails

• Transmission:

• Direct contact with infected person, animals, or contaminated

surfaces (e.g., locker rooms, towels)

• Treatment:

• Topical antifungals (terbinafine, clotrimazole, miconazole)

• Oral antifungals for severe or nail infections (terbinafine,

itraconazole)

Endemic Mycoses

Cause: Environmental fungi in specific geographic regions → infection via inhaled spores

• Common Infections (Most → Least Prevalent)

• Histoplasmosis – Histoplasma capsulatum

• Bird or bat droppings (US river valleys)

• Coccidioidomycosis– Coccidioides

• Soil dust (SW U.S.)

• Blastomycosis – Blastomyces dermatitidis

• Moist soil, decaying organic matter (Great Lakes–MW–SE U.S.)

• Transmission

• Inhalation of environmental spores

• Treatment

• Itraconazole • Fluconazole • Amphotericin B

Opportunistic Fungal Infections

• Causes: fungi that normally cause little disease but lead to serious infections in immunocompromised patients

• Common Infections (Highest to Lowest Prevalence):

• Candidiasis: (normal flora overgrowth) mucosal infections (oral thrush, vaginal), may become invasive

• Aspergillosis: (soil/dust/decaying plants) lung infection that may become invasive

• Cryptococcosis: (bird droppings) lung infection that may spread to CNS causing meningitis

• Pneumocystis pneumonia (PCP): airborne organism severe pneumonia in HIV/AIDS

• Transmission: Environmental exposure to spores or overgrowth of normal flora when immunity is weak

• Treatment:

• Nystatin → mucocutaneous Candida (oral thrush)

• Fluconazole → invasive Candida, Cryptococcus

• Echinocandins (e.g., caspofungin) → invasive candidiasis

• Amphotericin B → severe systemic infections

• TMP-SMX → Pneumocystis pneumonia

Invasive/Systemic Fungal Infections

Causes: fungi that invade deep tissues or organs and spread through the

bloodstream

• Common Infections (Highest to Lowest Prevalence):

• Invasive candidiasis: bloodstream infection affecting multiple organs

• Invasive aspergillosis: severe pulmonary infection with possible dissemination

• Disseminated cryptococcosis: CNS infection causing meningitis

• Disseminated histoplasmosis: widespread infection affecting multiple organs

• Transmission:

• Usually begins with inhalation of spores or bloodstream spread from another

infection site

• Treatment:

• Aggressive systemic antifungal therapy (amphotericin B, echinocandins, azoles

such as voriconazole or itraconazole)

Terbinafine

Therapeutic Class: Antifungal

• Pharmacologic Class: Allylamine antifungal

• MOA: Inhibits squalene epoxidase → blocks ergosterol

synthesis in fungal cell membranes → toxic squalene

accumulation → fungal cell death.

• Indications: Dermatophyte infections (tinea pedis, tinea

corporis, tinea cruris), onychomycosis (fungal nail infections),

tinea capitis.

• ADR: GI effects: nausea, diarrhea, abdominal pain, Headache,

Skin reactions: rash, pruritus

• Contraindications: Liver disease, hypersensitivity

• Nursing Considerations:

• Monitor liver function tests, especially with oral therapy.

• Oral therapy often required for onychomycosis (several

weeks to months).

• Advise patients to report taste disturbances or signs of

liver injury (dark urine, jaundice, fatigue).

• Preparations: PO (oral) and Topical (cream, gel, spray)

Fluconazole

Therapeutic Class: Antifungal

• Pharmacologic Class: Azole antifungal.

• MOA: Inhibits synthesis of ergosterol in fungal cell membranes.

• Indications: candidiasis, invasive candidiasis, cryptococcosis,

coccidioidomycosis

• ADR: N/V/D, headache, SJS/TENS, QT prolongation, hepatotoxicity,

nephrotoxicity, thrombocytopenia, leukopenia, anaphylaxis, strongly

inhibits CYP 450 = DDI

• Contraindications: liver disease, low potassium, pregnancy

• Nursing Considerations:

• Assess for rash or severe skin reactions (Stevens-Johnson

syndrome)

• Monitor ECG in patients at risk for QT prolongation

• Review drug interactions (strong CYP450 inhibitor → many

medication interactions)

• Monitor electrolytes, especially potassium

• Assess for signs of hepatotoxicity (jaundice, dark urine, abdominal

pain)

• Administration IV or PO

Nystatin

Therapeutic Class: Antifungal (local)

• Pharmacologic Class: Polyene

• MOA: Binds to ergosterol in fungal cell membranes and

causes leakage of cellular contents.

• Indications: oral, vaginal, cutaneous, and GI candidiasis,

• ADR: Generally mild, including skin irritation or mild GI upset.

• Nursing Considerations:

• Oral:

• Administer after meals to reduce GI upset.

• Swish liquid in mouth for several seconds, then swallow.

• Avoid eating/drinking for 30 minutes after use.

• Topical:

• Creams, powders and ointments

• Clean and dry affected area before applying.

• Apply a thin layer to the affected area 2-3 times daily.

• Monitor over skin irritation.

Amphotericin B

Therapeutic Class: Antifungal (Systemic)

• Pharmacologic Class: Polyene

• MOA: Binds to ergosterol in fungal cell membranes, creating pores

that lead to cell death.

• Indications: invasive (systemic) candidiasis, aspergillosis,

cryptococcosis, histoplasmosis, coccidiomycosis, blastomycosis

• ADR: Fever, chills, nausea, vomiting, rigors, hypotension = infusion

reactions!

• Nephrotoxicity: Kidney injury, hypokalemia, hypomagnesemia

• Cardiotoxicity: Arrhythmias, electrolyte disturbances

• Hepatotoxicity: Elevated liver enzymes (rare)

• Hematologic toxicity: Anemia, leukopenia, thrombocytopenia

• Neurotoxicity: Headache, dizziness, seizures (rare)

• Hypersensitivity: Anaphylaxis, rash

• Contraindications: Nephrotoxicity, hypokalemia

• Nursing Considerations:

• Monitor renal function (BUN, creatinine) → high risk of

nephrotoxicity

• Monitor electrolytes, especially potassium and magnesium

• Assess for infusion reactions (fever, chills, hypotension, headache)

• Premedication may be required (acetaminophen, antihistamines,

corticosteroids) to reduce infusion reactions

• PO or IV - Monitor IV site → risk of phlebitis

• Ensure adequate hydration to reduce kidney toxicity

Caspofungin

Therapeutic Class: Antifungal (Systemic)

• Pharmacologic Class: Echinocandin

• MOA: Inhibits β-1,3-D-glucan synthesis in the fungal

cell wall → disrupting fungal cell wall synthesis→

fungal cell death.

• Indications: Invasive candidiasis, candidemia,

esophageal candidiasis, salvage therapy for invasive

aspergillosis.

• ADR: Infusion reactions: fever/chills, hypotension,

flushing, rash, Hepatotoxicity, N/V/D, Phlebitis at

infusion site (rare)

• Contraindications: caution in hepatic impairment.

• Nursing Considerations:

• Monitor liver function tests.

• Observe for infusion-related reactions.

• Administer IV slowly to reduce histamine-mediated reactions.

Protozoa

Single-celled eukaryotic parasites

• Infect the intestines, blood, or tissues

• Transmitted through contaminated food/water, vectors,

or sexual contact

Common Infections

Intestinal infections

• (Entamoeba histolytica)

• Giardiasis (Giardia lamblia)

• Cryptosporidiosis (Cryptosporidium)

• Genitourinary infection

• Trichomoniasis (Trichomonas vaginalis)

• Blood infection

• Malaria (Plasmodium species)

• Tissue infection

• Toxoplasmosis (Toxoplasma gondii)

Intestinal Protozoal Infections

Common Features

• Transmission → fecal–oral (contaminated water or food)

• Diagnosis → stool O&P, antigen testing, or PCR

• GI illness → diarrhea, abdominal cramps, nausea, dehydration

• Major Infections

• Amebiasis – Entamoeba histolytica

• Bloody diarrhea, invasive disease

• May cause liver abscess

• Treatment → metronidazole/tinidazole → then luminal agent (iodoquinol or paromomycin)

• Giardiasis – Giardia lamblia

• Malabsorption, bloating, foul-smelling greasy stools

• Often associated with contaminated water or camping exposure

• Treatment → metronidazole, tinidazole, or nitazoxanide

• Cryptosporidiosis – Cryptosporidium

• Profuse watery diarrhea

• Severe disease in immunocompromised patients (e.g., HIV)

• Treatment → nitazoxanide + hydration

Trichomoniasis

Cause → Trichomonas vaginalis (protozoan parasite)

• Transmission → sexual contact

• Symptoms

• vaginal discharge (frothy, yellow-green)

• vaginal irritation or dysuria

• many infections asymptomatic

• Diagnosis → microscopy or NAAT testing

• Treatment → metronidazole or tinidazole

• Important → treat sexual partners to prevent reinfection

Malaria

Cause → Plasmodium parasites transmitted by female Anopheles mosquito

→ species: P. falciparum (most severe), P. vivax, P. ovale, P. malariae, P. knowlesi

• Pathophysiology → parasites infect liver → then red blood cells → RBC rupture → cyclic fever, chills, anemia, splenomegaly

• Symptoms → fever, chills, sweats, headache, fatigue

• Severe disease (P. falciparum) → cerebral malaria, anemia, organ failure

• Diagnosis → blood smear (gold standard) → rapid diagnostic tests or PCR

• Treatment → P. falciparum → artemisinin-based combination therapy (ACT) → chloroquine-sensitive species → chloroquine

• Prevention → mosquito control and traveler prophylaxis

Chloroquine

Therapeutic Class: Antimalarial drug

• Pharmacologic Class: Heme complexing drug

• MOA: Prevents the parasite from converting toxic heme (a

byproduct of hemoglobin digestion in red blood cells) into a

harmless form → toxic heme accumulates → parasite dies.

• ADR: Nausea, diarrhea

• CNS and cardiac toxicity at high doses

• Ocular toxicity (retinal damage, vision changes with prolonged

use)

• Contraindications: Allergy, CKD, Liver/blood diseases, Alcohol use

disorder, G6PD deficiency (increased risk of hemolysis)

• Nursing Considerations:

• Monitor ECG for arrhythmias

• Check liver and kidney function

• Monitor for vision changes (ocular toxicity)

• Educate patients to take with food to reduce GI upset

• Monitor for hemolysis in G6PD deficiency

• Complete the full prescribed course of therapy

• Avoid antacids and be cautious with drug interactions (e.g.,

digoxin)

Toxoplasmosis

Cause: Toxoplasma gondii (intracellular protozoan parasite)

• Transmission

• ingestion of oocysts from contaminated food/water or cat feces; undercooked meat (tissue cysts);

congenital transmission during pregnancy and disease in immunocompromised persons

• Pathophysiology

• parasite invades host cells and forms intracellular cysts

• spreads via blood to brain, muscle, and retina

• inflammation & tissue necrosis

→ encephalitis & ocular disease

• Birth defects!

• Signs/Symptoms

• often asymptomatic or mild flu-like illness

• immunocompromised: encephalitis, seizures, confusion

• congenital infection: neurologic damage and vision loss

• Diagnosis

• serology (IgG, IgM)

• PCR in severe or congenital infection

• Treatment: pyrimethamine + sulfadiazine + folinic acid

• Prevention

• avoid undercooked meat

• avoid cat litter exposure during pregnancy

Pyrimethamine

Therapeutic Class: Antiprotozoal

Pharmacologic Class: Folic acid antagonist

• MOA: Inhibits protozoal folic acid synthesis →

blocks DNA synthesis → inhibits parasite replication.

• Uses: Toxoplasmosis (most common) & Malaria (in

combination regimens)

• ADR: Nausea, rash, elevated liver enzymes

• Bone marrow suppression (anemia, leukopenia,

thrombocytopenia)

• Contraindications: Folate deficiency/megaloblastic

anemia, Pregnancy (teratogenic risk)

• Nursing Considerations:

→ Monitor CBC for bone marrow suppression

→ Give leucovorin to reduce folate toxicity

→ Monitor liver function (LFTs)

Helminths

• Parasitic worms transmitted through contaminated soil, food, or water → infect intestines or tissues

• Major Groups

1. Roundworms (Nematodes) → cylindrical worms in the intestine or migrating through tissues

Examples: Ascaris, hookworms, Enterobius (pinworms), Strongyloides,

2. Tapeworms (Cestodes) → flat segmented intestinal worms that absorb nutrients

Examples: Taenia solium, Taenia saginat a

3. Flukes (Trematodes) → flat leaf-shaped worms infecting blood vessels or organs

Example: Schistosoma

Helminth Infections

Pathophysiology

• Larvae enter via contaminated soil, food, or water

• Mature worms colonize intestines or migrate through tissues (lungs, liver, blood)

• Nutrient theft, blood loss, and immune inflammation → tissue damage and anemia

→ Major global burden in low-resource regions with poor sanitation

• Common Symptoms

• abdominal pain, bloating, diarrhea, weight loss

• cough or allergic symptoms during larval lung migration

• Physical Findings

• anemia, malnutrition, hepatosplenomegaly, eosinophilia

• Diagnosis: Stool O&P; serology; CT/MRI for tissue infections

• Treatment (key drugs)

• Albendazole / Mebendazole → most intestinal roundworms

• Ivermectin → Strongyloides

• Praziquantel → tapeworms & flukes (Taenia, Schistosoma)

• Supportive care → treat anemia and malnutrition

Mebendazole

Therapeutic Class: Anti-helminthic

• Pharmacologic Class: Microtubule inhibitor

• MOA: Blocks glucose uptake and energy

production in the parasite → parasite is starved

of energy and dies.

• ADR: Abdominal pain, distension, diarrhea.

• Rare: seizures, agranulocytosis.

• Contraindications: Hypersensitivity, serious

hepatic impairment.

• Nursing Considerations:

• Instruct patient to chew tablet for maximum

effect

• Monitor for side effects.

Ectoparasites

organisms that live on the external surface of their hosts, feeding on blood or skin.

• They can cause irritation, itching, and sometimes infections.

• Common Ectoparasitic Infections:

• Scabies: Caused by the Sarcoptes scabiei mite, leading to intense itching and skin rashes.

• Lice: Small, blood-feeding insects, including head lice, body lice, and pubic lice, causing itching and irritation.

Scabies

Caused by the Sarcoptes scabiei mite, leading to intense itching and skin rashes.

Lice

Small, blood-feeding insects,

including head lice, body lice, and pubic

lice, causing itching and irritation.

Ectoparasitic Infections

Pathophysiology

• parasites live on or burrow into skin → feed on blood/skin debris → immune

hypersensitivity reaction → intense itching and skin inflammation

• Symptoms

• severe itching (often worse at night)

• rash, sores, or blisters

• Physical Findings

• erythematous, excoriated skin

• mites, burrows, or lice eggs (nits) on hair shafts or skin folds

• Diagnostic Tests: skin scraping for mites (scabies

• visual identification of lice or nits

• Treatment

• Scabies: permethrin cream or oral ivermectin

• Lice: permethrin or pyrethrin pediculicides

• treat secondary bacterial infection if present

Ivermectin

Therapeutic Class: Antiparasitic

• Pharmacologic Class: Avermectin

• MOA: Binds parasite glutamate-gated chloride

channels → paralysis and death of parasites

• Indications:, Scabies (oral option when topical therapy

fails); Head lice; Strongyloidiasis, Onchocerciasis

• ADR: Dizziness, headache, Nausea, diarrhea, Rash or

itching

• Rare: hypotension, neurologic effects

• Contraindications: Pregnancy; Caution in severe liver

disease

• Nursing Considerations:

• Single oral dose ~ 200 mcg/kg, may repeat in 1–2

weeks

• Monitor for neurologic symptoms and skin

reactions

Permethrin

Therapeutic Class: Antiparasitic

• Pharmacologic Class: Pyrethroid pediculicide

• MOA: Disrupts parasite sodium channels → paralysis and death of mites and lice

• Indications: Scabies and Head lice (pediculosis)

• ADR: Mild burning or stinging, Itching or skin irritation, Rash (rare)

• Contraindications: Hypersensitivity

• Nursing Considerations:

• Apply topically to affected areas

• Scabies: apply to entire body (neck down), wash off after 8–14 hours

• Lice: apply to scalp/hair, repeat in 7–10 days if needed

• Treat close contacts and wash bedding/clothing in hot water

Tinea pedis

athlete’s foot; itching, scaling between toes

Tinea coporis

ringwork; circular rash on skin

Tinea capitis

scalp infection; hair loss, scaling

Tinea cruris

“jock itch”; groin infection

Tinea unguium

onychomycosis, fungal infection of nails

Histoplasmosis

-Histoplasma capsulatum

-Bird or bat droppings (US river valleys)

Coccidioidomycosis

-Coccidioides

-Soil dust ( SW U.S.)

Blastomycosis

-Blastomyces dermatitidis

-Moist soil, decaying organic matter (Great Lakes-MW-SE U.S.)

Amebiasis - Entamoeba histolytica

Bloody diarrhea, invasive disease

• May cause liver abscess

• Treatment → metronidazole/tinidazole → then luminal agent (iodoquinol or paromomycin)

Giardiasis - Giardia lamblia

Malabsorption, bloating, foul-smelling greasy stools

• Often associated with contaminated water or camping exposure

• Treatment → metronidazole, tinidazole, or nitazoxanide

Cryptosporidiosis - Cryptosporidium

Profuse watery diarrhea

• Severe disease in immunocompromised patients (e.g., HIV)

• Treatment → nitazoxanide + hydration

Roundworms (Nematodes)

cylindrical worms in the intestine or migrating through tissues

Examples: Ascaris, hookworms,

Enterobius (pinworms), Strongyloides

Tapeworms (Cestodes)

flat segmented intestinal worms that absorb nutrients

Examples: Taenia solium, Taenia saginat a

Flukes (Trematodes)

flat leaf-shaped worms infecting blood vessels or organs

Example: Schistosoma