Infectious Disease Transmission Flashcards
Describe prions
Protein particles without a genome. Infectious and capable of producing disease. Ex: Creutzfeldt-Jakob disease, Kuru and “mad cow” dz. Slow neurodegenerating diseases
Describe viruses
Intracellular pathogen/incapable of replication outside a living cell. Consist of a protein coat (capsid), surrounding either RNA or DNA. Viruses MUST penetrate a susceptible living cell & use the biosynthetic machinery of the cell to produce viral progeny (Latency). ONCOGENIC: HPV, Epstein-Barr
Describe bacteria
Autonomously replicating unicellular organism (prokaryotes). contain no organized intracellular organelles. Genome consists of a single chromosome of DNA and RNA. Most produce asexually by cellular division. Gram-positive—PURPLE. Gram-negative—RED
Describe fungi
Free-living, eukaryotic saprophytes found in every habitat on earth. serious fungal infections are rare. Reproduction is sexual or asexual (Involves production of spores). separated into two groups: yeasts and molds
What are the differences between yeasts and molds?
Yeasts: Single-celled organisms, Reproduce by a budding process, Colonies are smooth with a waxy or creamy texture. Molds: Produce long, hollow, branching filaments—hyphae. Some produce cross walls which segregate the hyphae. Produce cottony or powdery colonies of mats of hyphae–mycelium
What are arthropods?
parasitic vectors such as ticks, mosquitoes, biting flies.
What are ectoparasites?
Infest external body surfaces and cause localized tissue damage or inflammation secondary to the bit or burrowing action (Mites (scabies), Chiggers, Lice, Fleas)
What are protozoa?
Unicellular parasites with eukaryotic machinery**. Reproduction may be sexual or asexual. Most are saprophytes, but some can cause disease in the human. Ex: amebic dysentery, malaria, and giardiasis
What are helminths?
Collection of wormlike parasites: nematodes (roundworms), cestodes (tapeworms), & trematodes (flukes). Often an intermediate host is required for development & maturation of the offspring and then humans are infected and sexual reproduction occurs in the human host. Helminth infections often involve multiple organ systems
What is the difference between incidence and prevalence?
Incidence—number of new cases. Prevalence—number of active cases at any given time
What are exotoxins?
Proteins released from the bacterial cell DURING growth. Enzymatically inactivate or modify cellular constituents, leading to cell death or dysfxn (diptheria, botulism, toxic shock syndrome). produce vomiting/diarrhea—enterotoxins (E. coli 0157:H7)
What are endotoxins?
molecules composed of lipid & polysaccharides found in the cell wall of gram-negative bacteria. NOT actively released during growth of the bacteria & have no enzymatic activity. They are potent activators of regulatory systems (induce clotting, hypotension, fever). Can induce endotoxic shock
Describe how pathogens use adhesion factors
Site to which a microorganisms adheres to is called a RECEPTOR where there is a LIGAND or ADHESIN. After initial attachment, a number of bacterial agents embed into a gelatinous matrix of polysaccharides (flu, mumps, measles)
Describe how pathogens use evasive factors
Polysaccharides (capsules, slime, & mucous layers) discourage engulfment & killing by the phagocytic WBCs. Some organisms secrete toxins that deplete the hosts WBCs. Some pathogens can survive INSIDE the ingestion by the WBC.
What are some specific examples of pathogens using evasive factors?
S. aureus secretes coagulase that causes blood to clot around the pathogen & protects it from phagocytosis. H. pylori produces urease that converts gastric urea into ammonia which neutralizes the acidity of the stomach allowing the pathogen to survive. H. influenzae & N. gonorrhoeae secrete enzymes that inactivate IgA
