Filamentous Fungi, Yeasts, and Pathogenic Fungi: Key Concepts and Pathogens

What are Filamentous Fungi (AKA MOLD)

mass of hyphae called mycelium

Chiten

Acrylated amino-polysaccharide, cell wall of fungi

Filamentous fungi trait

Expand by asexual division

Gametes

reproductive cells of mold, produce spores, fuzzy

Fungi are

Opportunistic pathogens

Single cell yeast advantage

Rapid growth, better in aqueous environment

Candida albicans (yeast)

Causes oral thrush/yeast infections from disrupted microflora - antibiotics

Saccharomyces cerevisiae (yeast)

Bakers and brewers yeast

Candidozyma auris problems (yeast)

Global temp, agriculture and farming make it more prevalent in populated areas (infectious)

Saprophytic fungi

break down, recycle organic material

Cryptococcus neoformans causes

Lung infection, meningitis in immunocompromised individuals

Pnemocystis jirovecii

yeast like fungus, Inhalation leads to serious pneumonia in immunocompromised hosts, picked up from dust, dirt, respiratory droplets - can be asymptomatic

Dimorphic fungi

Form both as mold and yeasts

Dimorphic fungi cause

Immunocompromised people at highest risk and sometimes pets. Rarely healthy people usually requires they inhale a large number of spores.

Histoplasma species aka Histo, Blastomyces species aka Blasto, Coccidioides species

Histoplasmosis comes from 

Soil, infected feces from bats, or birds, and can cause respiratory issues.

Coccidioides causes

Valley fever

Blastomycosis infection

Inhaled spores from environment

Amebas are 

Voracious predators - consume protists and bacteria, can reach several mm in size

Two groups of amebas

Lobed - large pseudopods

Filamentous - needlelike pseudopods

Entamoeba histolytica

Serous intestinal illness in developing world, create cysts viable for many weeks, excyst into trophozoites in intestines, eat RBCs and proteins, transmit fecal-oral route

Ameba cysts

Spore like

Intestinal amebas

Severe cases invade lungs, Liver and other organs

Wheatley’s trichrome stain

Revels parasites among human cells and fecal matter

Amebic Dysentery 

Repeat infection leads to malabsorption - Entamoeba histolytica 

Naegleria Fowleri is

Meningoencephalitis - Brain eating amoeba

Acanthamoeba

Corneal infections - Keratitis

Legionella pneumophila 

causes legionellosis

Apicomplexans

Major group of parasites that infection humans and animals, Apical complex facilitates entry into host cell - Alveoli, pores, microtubules

Malaria

Plasmodium falciparum and plasmodium

Toxoplasmosis 

Toxoplasma gondii - manipulates fear response in mice

Malaria life cycle

Mosquito - liver - red blood cells - mosquito

Malaria cyclic fevers cause

Changes antibodies, WBCS eradicate first strain, second strain emerges - Antigenic Variation

Trypanosomes 

elongated cell, with flageum 

African sleeping sickness (Trypanosoma brucei)

Trapanaznol parasite cause by tsetse fly, changes surface protein to remain undetected

African sleeping sickness life cycle

Tsetse fly - animal blood stream - fly picks up parasite - transmits to other humans and animals

Chagas disease (Trypanosoma cruzi) 

American, Spread by kissing bug, fever swelling at bite, usually in face

Metamonads

Flagellated parasite

Giardia lamblia causes

Intestinal giardiasis, from water streams - day care carriers 

Helminths cause

Global health burden, parasitic worms

Pinworms

Small white nematode, may cause malabsorption or anerexioa to host immune response

Hookworms

Larva grow in soil, infect feet, travel through blood to lungs, coughed into throat and ingested, attach to intestines, exit through host feces

Ascaris lumbricoides

Roundworm, Grow large in humans, cause by ingestion of eggs through soil, may invade lung or other organs, may obstruct intestinal tract. 

Flukes

Require mollusks as primary host, each species prefers different organs

Schistosomiasis (schistomas)

Type of fluke, ascites, muscle atrophy, anemia, hemorrhage in GI

Cercarial dermatitis (swimmers itch)

From shistoma that infects waterfowl

Cestodes (Tapeworm)

Segment that look like tape (eggs) Common in Asia and south America, muti feet in length

Tissue tropism

Only like certain tissues to replicate

Viral genomes are only

DNA and RNA

Capsid protein

Encloses genetic material

Viral transmission depends on

1. Host recognition and attachment

2. genome entry

3. Assembly of progeny visions

4. Exit and retransmission 

Lytic phages

Infect and kill host to reproduce

Lysogenic phages

Integrate genome after infection, kill host by lysing when host becomes stressed to reproduce

Lysogenic phages on human health

alter genome to cause host to release toxins, affect human health. Shiga toxin, cholera toxin. Diphtheria, main effect on humans

Viruses capable of lysogeny exit

can occur at random

Herpes Viruses are

DNA viruses, enveloped, have long latency times

Chicken pox

Herpes virus, travels to dorsal ganglion, leads to shingles

Pain from shingles caused by

Replication in neurons

80%

Percentage of adults have HPV

Gardasil

Vaccine for HPV strains which would lead to genital cancer, Protects against 9 strains

How does Gardasil work

Mimicking capsid proteins that would form outside, no genetic material

P53 

Cellular anti-cancer protein

E6

Destroys P53

E7

Allows cells to divide fast

What does HPV do during viral takeover

Integrates into host genome, Uses E6 to block P53 cellular apoptotic protein, E7 allows for faster cellular division

Flu virus structure

RNA virus, enveloped with outer lipid layer

Flu viruses can 

can swap genome segments if 2 or more infect host cell, creating new strains, RNA replicate in host cytoplasm

Genetic Drift

Small mutations in genome code, HA NA subtypes of flu lead to new vaccines every year 

Genetic Shift

Large changes, Two different virus enter host cell. Avian flu and Human flu infect swine to produce new strain of flu, can be more virulent 

Neuraminidase (NA)

Cut bond from Hemagglutinin to release virion from host cell surface

How does tamiflu work

Inhibits neuraminidase from cutting the Hemagglutinin bond on host cell surface (neuraminidase inhibitor)

H5N1

Avian to cattle, can be deadly to humans

HIV is what type of virus 

RNA retrovirus

HIV

Has long latency, infect helper T-cells, is enveloped

CD4 and CCR5

Receptors on cells allow access into helper T-cells, blocked by antivirals - spike protein of HIV cannot bind

HIV RNA transcribes with

Reverse transcriptase with host nucleotides, and randomly integrated with host DNA

HIV antiviral drugs

1. Block CD4 and CCR5- entry inhibitors

2. Reverse transcriptase inhibitors – block HIV from taking it’s RNA and making DNA.

3. Integrase inhibitors – block HIV DNA from being inserted into human genome.

4. Protease inhibitors – Block maturation of HIV proteins by blocking the activity of HIV protease to separate HIV polyprotein into separate active protein. 

Coronaviruses

RNA virus, contains spike proteins, enveloped

Remdesivir 

Covid antiviral, Adenosine Analog, Blocks Transcriptase 

Paxolovid

Covid antiviral, Blocks protease

IGG Antibody block covid by

Providing immunity for short time, when viral load increases the immune system recognizes infection and quickly takes care of it.

Whole virus vaccines take

Years to develop 

2 whole virus vaccines

Inactivated (heated), Live attenuated (virus has been weakened)

MRNA vaccines

Mimic native viral infection, envelope taken in by cell, Uses RNA to transcribe antibodies

Old vaccines help protect against

New variants of covid, old antibodies may partially bind to spike proteins