Pathogenesis Flashcards
(31 cards)
What is putrefaction?
The decomposition of proteins by putrefying bacteria (anaerobic) resulting in the formation of polyamines with a putrid odour
What is gnotobiology?`
Raising mammals under germ-free environments, or conditions with controlled spectra and numbers of microorganisms
What is tetanus?
A disease caused by bacterium clostridium tetani
What is pathogenesis?
A set of mechanisms by which an etiological factor (primary reason for a disease) causes a disease, pathos=disease, genesis=development
What is epidemiology?
The study of the occurrence, distribution and control of diseases in populations
What are the primary causal factors of diseases?
Genetic, physiological and environmental
What are the three types of interactions between organisms? and give examples of each
Parasitic - measles, typhoid and Tb
Commensal - normal flora
Symbiotic - microflora that produces vitamins like B12
What is the difference between true and opportunistic pathogens?
A true pathogen overcomes the host’s defences and causes disease easily while opportunistic pathogens cause disease in hosts with a reduced defensive capacity. Opportunistic pathogens are usually commensal organisms
Are protozoa highly virulent?
The majority aren’t and are not able to replicate in the host, the extent of the disease is usually related to the infecting dose. They are often chronic
What is virulence?
The extent of pathogenicity expressed by a pathogen can be expressed as a number of the pathogens cells sufficient for a pathogenic response. The smaller being the more virulent
What is ID50 and LD50?
ID50 - The number of pathogen cells required for 50% of the host population to show signs of infection
LD50 - The number of pathogen cells required to kill 50% of a host population
What are the transmission routes and what is meant by vehicles and vectors?
Respiratory tract, faecal-oral route, urogenital tract and mechanical transmission. Vehicle transmission is a means of transmission that involves riding along supposedly clean components such as food, water drugs etc. Vectors are arthropods that transmit pathogens, such as fleas, mosquitoes, ticks and lice
What is the progression of a typical disease?
Infection, incubation period, acute period, decline period and convalescent period (or death in some cases)
What are two ways of pathogenicity?
Toxicity - causing disease by different toxins that inhibit or kill host cells
Invasiveness - a pathogen that grows in a tissue to such amounts of cells that inhibit host functions and cause disease
What are 3 factors that affect pathogenesis?
Pathogen factors, Host factors and environmental factors
How can pathogens overcome host defenses?
They can overcome them through either passive defence, which is based on the structural components of the pathogen cell (cell wall) or by active defence, which is interfering with the host defences (toxins)
What is the main passive defence that inhibits phagocytosis by host cells?
A bacterial capsule
What material is present in cell walls of mycobacterium species?
A waxy material called mycolic acid, it inhibits the process if phagocytosis and the access of antibiotics into the cells
What are exotoxins and what are the three sub-groups of them?
Exotoxins are toxic extracellular proteins secreted by gram +ve and -ve bacteria. The three groups are cytolytic toxins, A-B toxins and superantigen toxins
What are the differences between the three sub-group exotoxins?
Cytolytic toxins - lyse host cells by enzymatic degrading cellular components (mostly membrane)
A-B toxins - consist of two covalently bonded subunits A(ctive) and B(inding). B subunit usually binds a cellular surface receptor that allows transferring A subunits through the membrane to the cell and damaging it
Superantigen toxins - stimulate large amounts of immune response cells that leads to massive inflammatory reactions
What are enterotoxins?
Exotoxins that affect the host’s small intestines. They are often cytotoxic and kill epithelial cells in the intestinal wall by altering their permeability by forming pores in the cell membranes
What are endotoxins?
Lipopolysaccharides produced in the outer layer of cell envelope of gram -ve bacteria, produced when they are dying
What are factors that contribute to host innate resistance?
Nose and mouth
Ciliated epithelial cells of mucosal surfaces upward bacteria into mucous to be expectorated or swallowed and killed in the stomach
Stomach
Lumen of kidney and eyes that produce lysozyme
Blood that contains bacteriocidal beta-lysins that bind and disrupt bacterial cytoplasmic membranes
How does killing host cells benefit the bacterium?
It allows the bacterium to use cellular products as nutrients and to release a space for further spreading into the tissue
