Lecture 2 Flashcards
infectious disease definition
disease resulting from infection
infectivity
ability of pathogen to recognise cell receptors, invade, multiply and spread inside of a hostc
communicable disease
transmitted from 1 individual to another
contagious disease
communicable disease spread by direct contact
infectious disease that are easily transmitted by contact with an ill animal or their secretions
opportunistic infection
pathogens can cause infectious disease in a host with depressed resistance or if they have unusual access into he body
recurrent infection
infections that are too great in number, too severe, or too long-lasting
reinfection
additional infection with the same microorganism, occurring after the first infection has resolvede
relapse
2nd episode of disease due to re-emergence of the original infection
superinfection
additional infection witht eh same microorganism, occurring during the course of an existing infection
autoinfection
infection with bacteria or viruses that persist on or in the body
nosocomial
infection acquired in a hospital
stages of infection
- exposure (contact)
- adhesion (colonisation)
- invasion
- multiplication
- exit
koch’s postulates
to identify the causative agent of an infectious disease
4 criteria
1. pathogens are only found in diseases, not in healthy
2. causative agent must be isolated from the disease organism
3. culture agent must cause the sam disease when inoculated into a healthy susceptible organism
4. same causative agent must then be reisolated from the inculcated diseases
pathogenicity defintion
ability of an organism to cause disease
virulence definition
degree of pathology cause by the organism
virulence factors
- refer to the properties that enable a microorganism to establish on or within host
- they help to: invade host, evade host defences, multiply, exit, cause disease
bacterial virulence factors
- adherence components (attachment)
- use fimbriae to adhere - capsules (evasion)
- surrounded by capsules to protect them - entry into host
- some produce enzymees to invade cells and go deeper (hyaluronidase, collagenases, coagulase etc) - toxins
- produce toxins and damage host cells
- exotoxins = into cell surroundings (cytolytic exotoxins, super antigens and A-B toxins)
- endotoxins - less toxic than exotoxins
viral virulence factors
- viral replication
- adherence
- tropism
- modify the host defence mechanism
