Infectious Agent Flashcards: Prokaryotic vs. Eukaryotic Pathogens

Prokaryotic Pathogens

Have DS DNA genomes

Prokaryotic Pathogens

Generally smaller (~1 μm)

Prokaryotic Pathogens

Do not have a nucleus or membrane-bound organelles (this is implied by the definition of eukaryotic)

Eukaryotic Pathogens

Have a dsDNA genome within a nucleus

Eukaryotic Pathogens

Possess membrane bound organelles

Eukaryotic Pathogens

Are generally larger (up to 10x larger than bacteria, ranging from invisible to the naked eye to ~1 foot)

Eukaryotic Pathogens

Can be single or multi-cellular.

parasites compared to viruses, prions, and bacteria?

Are Eukaryotic pathogens2 .... This is a key difference from bacteria (prokaryotic), viruses, and prions (not cellular)

parasites compared to viruses, prions, and bacteria?

Are living things that meet all the criteria for life (consist of one or more cells, capable of homeostasis, make energy, grow, respond to stimuli, reproduce, evolve). Viruses are obligate intracellular, prions are nonliving protein

parasites compared to viruses, prions, and bacteria?

Are generally much larger than bacteria, viruses, and prions, ranging from visible by light microscopy to visible with the naked eye, even up to ~1 foot in length. Bacteria are ~1 μm, viruses are 20-500 nm, and prions are smaller than viruses

parasites compared to viruses, prions, and bacteria?

Can be single or multi-cellular. Bacteria are single-celled, viruses and prions are not cellular.

Protozoa

Are single-celled organisms

Protozoa

Mostly asexually reproduce

Protozoa

Generally exist as obligate intracellular pathogens

Protozoa

Have a single cell membrane, making drying out a risk

Protozoa

Often transmit host to host with no environment in between

Protozoa

Found in humid or wet environments

Protozoa

Use alternating forms: trophozoite & cysts

Protozoa

Employ various forms of locomotion (Pseudopods, Flagella, Tractor-tread gliding motility, Ciliated)

Protozoa

Plasmodium, Toxoplasma, Giardia, Cryptosporidium, Leishmania, & trypanosomes

Helminths

Are multi-cellular animals (worms)

Helminths

Mostly reproduce sexually, requiring male & female worms

Helminths

Usually cause extracellular infections

Helminths

Are relatively large

Helminths

Types include Round worms, Flat worms (Flukes, Tapeworms)

Describe the general features of parasitic life cycles, infections, and host immune responses. Life Cycles & Transmission

Often more complex, requiring many phases of growth and potentially multiple host species

Describe the general features of parasitic life cycles, infections, and host immune responses. Life Cycles & Transmission

Arthropod vectors are required for many, limiting geographical range

Describe the general features of parasitic life cycles, infections, and host immune responses. Life Cycles & Transmission

Humans/animals can be Reservoir species (maintain parasite, may be asymptomatic) or Dead-end hosts (cannot propagate)

Describe the general features of parasitic life cycles, infections, and host immune responses. Life Cycles & Transmission

Common entry routes: fecal-oral, anal-oral, penetration of unbroken skin, or via vector bites

Describe the general features of parasitic life cycles, infections, and host immune responses. Life Cycles & Transmission

Low inoculum doses are often sufficient

Describe the general features of parasitic life cycles, infections, and host immune responses. Life Cycles & Transmission

For Protozoa, inoculum dose does NOT determine damage because one can produce many progeny

Describe the general features of parasitic life cycles, infections, and host immune responses.Life Cycles & Transmission

For Helminths, inoculum dose directly correlates to disease severity (1 egg = 1 worm)

Describe the general features of parasitic life cycles, infections, and host immune responses. Infections & Damage

Damage may be mediated by the parasite, the immune response, or both

Describe the general features of parasitic life cycles, infections, and host immune responses. Infections & Damage

Disease is generally not acute, but often comes later (months or years) due to chronic inflammation

Describe the general features of parasitic life cycles, infections, and host immune responses. Host Defense & Diagnosis

Host defense mechanisms exist, but parasites have ways to evade them

Describe the general features of parasitic life cycles, infections, and host immune responses. Host Defense & Diagnosis

Immune responses may be specific to certain life phases (larval vs adult)

Describe the general features of parasitic life cycles, infections, and host immune responses. Host Defense & Diagnosis

Diagnosis traditionally involves microscopic identification

Describe the general features of parasitic life cycles, infections, and host immune responses. Host Defense & Diagnosis

More recently, antigen detection and/or nucleic acid-based detection are used (mainly for protozoa).

Describe the general features of parasitic life cycles, infections, and host immune responses. Prevention & Treatment

Prevention focuses on drugs, immunization, and administrative control measures

Describe the general features of parasitic life cycles, infections, and host immune responses. Prevention & Treatment

Sanitation is a key administrative control to reduce fecal-oral transmission . Bed nets, insecticides, and shoes can also be effective

Describe the general features of parasitic life cycles, infections, and host immune responses. Prevention & Treatment

Understanding the life cycle is crucial for effective prevention and treatment

Describe the general features of parasitic life cycles, infections, and host immune responses. Prevention & Treatment

Treatments include Antiprotozoal and Anthelminthic drugs

Describe the general features of parasitic life cycles, infections, and host immune responses. Prevention & Treatment

Many antiparasitic drugs are decades old, and resistance develops

Describe the general features of parasitic life cycles, infections, and host immune responses. Prevention & Treatment

Treatments can sometimes be toxic