Pathogens

Herpes Simplex

• dsDNA virus

- acute phase in epithelium, long-term latent infection in nerve tissue

dsDNA viruses

- largest group

- genome codes for DNA and RNA polymerases, integrases, etc.

- some bacteriophages, herpesviruses

Herpes Zoster/Varicella vius

- dsDNA virus

- first infection: chickenpox

- recurrence: shingles

Cytomegalovirus (CMV)

- dsDNA virus

- infect any cell of the body

- range from asymptomatic to severe inclusion disease

Epstein-Barr virus (EBV)

- dsDNA virus

- acute phase in epithelium, then in B cells

- mononucleosis

Human papilloma virus (HPV)

- dsDNA virus

- genital warts

- high-risk strains for cervical cancer

ssDNA viruses

- some bacteriophages, some parvoviruses

- additional step in DNA replication to make dsDNA, for ex. via rolling circle replication

Parvoviruses

- ssDNA virus

- not common human pathogens

- "fifth disease"

dsRNA viruses

- not very common

- some bacteriophages, rotaviruses

- viral RNA polymerase act in replication and transcription

Rotavirus

- dsRNA virus

- most common cause of pediatric gastroenteritis

ssRNA viruses

- either +RNA or -RNA viruses

- viral RNA polymerase act in replication and transcription

Norovirus

- ssRNA virus

- +RNA

- "winter vomiting bug"

- can cause food-poisoning outbreaks

Coronavirus

- ssRNA virus

- +RNA

- very diverse --> MERS-CoV, SARS-CoV, SARS-CoV-2 causes COVID-19

SARS-CoV-2

- ssRNA virus

- +RNA

- unique configuration of spike protein

- sugar coating against Ig

Influenza (flu) virus

- ssRNA virus

- -RNA

- very contagious

- high variability --> evades immune system

- new vaccines every year

Measles virus

- ssRNA virus

- -RNA

- most contagious, endemic worldwide

- no cure, important cause of child mortality globally

Rabies virus

- ssRNA virus

- -RNA

- zoonotic

Retroviruses

- HIV is the most studied

- genomes do not work as mRNA; ssDNA and dsDNA prior to mRNA

Human Immunodeficiency Virus (HIV)

- retrovirus

- acquired MHC proteins

- binds to CD4+ T cells

- integration of viral genome

Reverse transcribing DNA viruses

- hepatitis B virus is the most studied

- use reverse transcriptase to replicate DNA

Hepatitis B virus (HBV)

- reverse transcribing DNA viruses

- chronic liver degeneration

- can lead to liver cancer

Eukaryotic pathogens

- transmission examples: direct contact (trichomonas), air-borne (aspergillus), food and water-borne (entamoeba, giardia, naegleria), via arthropods (plasmodium, leishmania), zoonotic (toxoplasma)

Fungal pathogens

- fungi are unicellular (yeasts) or multicellular (molds, filamentous fungi)

- multicellular fungi form hyphae, which disperse as asexual spores

- some dimorphic: Y-M shift, change from mold (M) in the environment to yeast (Y) in the host --> virulence

Trichophyton

- fungal pathogen - superficial, cutaneous, or subcutaneous mycoses

- athlete's foot (tinea pedis) and other

- hyphae burrow and release enzymes

- feed on the keratin in dead skin, nails, hair

Histoplasma

- fungal pathogen - systemic mycoses

- spores inhaled form areas with bird and bat droppings

- dimorphic: switches to yeast once in the lung

- causes flu-like disease and sometimes spreads systemically

- endemic in some part of Us

Protozoan pathogens

- pathogenic protozoans have very complex life cycles with more than one host, including humans

Plasmodium

- protozoan pathogen

- transmitted by Anopheles

- causes malaria

- mostly tropical/subtropical

Leishmania

- protozoan pathogen

- transmitted by sandfly

- causes severe cutaneous, mucosa, and visceral lesions

- a "disease of poverty"; developing countries

Trichomonas

- protozoan pathogen

- sexually transmitted

- men asymptomatic; notorious symptoms in women

- worldwide distribution

Entamoeba, Giardia

- protozoan pathogen

- cyst ingestion from fecal traces in food, water, hands, fomites

- cause intestinal disease

- worldwide distribution

Naegleria Acanthamoeba

- protozoan pathogen

- direct contact from water

- "brain-eating" amoeba

- lens-associated keratitis

- worldwide distribution

- extremely deadly

Toxoplasma

- protozoan pathogen

- cyst ingestion from cat/litter manipulation

- generally asymptomatic, but can cause brain disease in fetus that acquires it vertically

- worldwide distribution

Escherichia coli

- bacterial (opportunistic pathogens)

- colony morphology: white/beige, shiny, mucoid

- cell morphology: bacilli (rods)

- lactose fermentation: +

- part of gut microbiome, some virulent strains cause gastroenteritis or other infections

Staphylococcus spp.

- colony morphology: circular, white/yellow pigment

- cell morphology: cocci in clusters

- catalase: +

Streptococcus spp.

- colony morphology: circular, white/gray pigment, mucoid

- cell morphology: cocci in chains

- catalase: -

Botulism

- food-borne and waterborne pathogens

- botox toxin - blocks the synapses of nerve terminals in muscles

- toxin produced anaerobically by Clostridium botulinum

- causes paralysis and death

Cholera

- food-borne and waterborne pathogens

- Vibrio cholerae, a comma-shaped, Gram-negative bacterium

- transmitted by fecal-contaminated food or water

- toxin induces in massive loss of water and electrolytes

- quorum sensing

Salmonellosis

- food-borne and waterborne pathogens

- over 2,000 non-typhi Salmonella serovars

- diarrhea

Chlamydia

- sexually transmitted infections

- Chlamydia trachoma's, an obligate intracellular Gram -

Gonorrhea

- sexually transmitted infections

- Neisseria gonorrhoeae, a facultative intracellular Gram - diplococcus

Syphilis

- sexually transmitted infections

- Treponema pallidum, a spirochete

Hemolysis

- pore forming exotoxin

- staphylococcus, e.coli, streptococci

- lyses erythrocytes, making iron available for microbe

Choleratoxin

- AB exotoxin

- Vibrio cholerae

- affects cAMP (increase), leading to H2O secretion from cells --> cel death

- diarrhea, dehydration

Streptomycin O

- superantigen exotoxin

- s.pyogenes

- causes hemolysis and cytokine-induced shock