chapter 5 microbiology Flashcards
whats a pathogen?
microorganism capable of causing disease
what does opportunistic mean?
cause disease only in compormised individuals
LD 50
“lethal dose” number of organisms needed to kill half the hosts cells
ID 50
Infectious dose, number of organisms needed to infect half the hosts
Communicable disease
spread from host to host. When a disease is highly communicable it is considered contagious
Endemic
constanly present at a low level in a specific population
Epidemic
occurs more frequently than usual
pandemic
worldwide distribution
stages of infectious diseases are….
incubation period, prodomal period, acute specific illness, recovery period.
incubation period
time between acquisition of organism or toxin and the commencement of symptoms
prodomal period
non specific symptoms like fever and malaise, loss of appetite
acute specific illness
specific symptoms start occurring
recovery period
illness stops and returns to normal
what are the determinates of pathogenicity?
transmission, adherence, invasiveness and toxigenicity
How are pathogens transmitted?
inhalation, ingestion, inoculation
name the 4 important portals of entry for pathogens
skin, respiratory tract, gastrointestinal tract, genitourinary tract
what are biofilms?
aggregates of interactive bacteria attached to a solid surface( including prosthesis). Up to 65% of human infections are associated with biofilms
what is a quorum in biofilms?
sensing molecules- biofilms secrete this which tend to repulse incoming bacteria or activate the communal bacteria to seek new bodies
sessile organisms in biofilms
harder to eradicate when sessile
planktonic biofilm organisms
easier to eradicate
what does collagenase and hyaluronidase to for bacteria
degrade intercellular substances allowing easy spread of bacteria through tissue
what does coagulase do for bacteria?
accelerates formation of fibrin clot which helps protect the organisms from phagocytes
what does immunoglobulin A protease do for bacteria?
kills IgA on mucosal layers
leukocidins role for bacteria is …
kills neutrophilic leukocytes and macrophages
what is pyogenic inflammation?
pus producing
what is granulomatous inflammation?
granuloma forming
Name some contributing factors fo toxigenicity
endotoxins, fever, hypotension, activation of cascade pathway for inflammation, increased phagocytic activity, increased antibody production
Endotoxins
they are the cell wall of lipopolysacharides of gram negative bacteria and are not actively released from the cell. These cause fever, shock, and other general symptoms. Some biological effects are below
fever
due to release of IL-1 ( interleukin 1). They act on the hypothalamic temperature regulatory centre and reset it to a higher temperature
hypotension-
from release of bradykinin which decrease peripheral resistance
exotoxins
highly toxic but have good antigens and induce the synthesis of protective antibodies called antitoxins
what are exotoxins categorized into?
neurotoxins, enterotoxins, and miscellaneous exotoxins
Name some neurotoxins and what they do
tetanus toxin-blocks the release of inhibitory transmitter which leads to sustained contractions of voluntary muscles
diptheria toxin- inhibits protein synthesis in all eukaryotic cells
botulinum toxin-blocks release of acetylcholine at the synapse , producing paralysis of both voluntary and involuntary muscles
what do enterotoxins do?
increase cAMP which promotes cellular chloride ion excretion and inhibition of sodium ion absorption which leads to diarrhoea
natural defeses of the oropharynx and intestinal tract
Continuous desquamation of epithelium, presence of saliva, mucous in intestine, gastric acid, bile and proteolytic enzymes, movements of tonuge and cheek and peristalsis, immune mechanisms
Defense mechanisms of respiratory tract
mucous from golblet cells and mucociliary escalator, IgA in respiratory secretions, alveolar phagoytes
Defense of genitourinary tract
natural mucosal desquamation, vaginal secretions and cervical mucous, flushing of urine action
What is viraemia?
entry of the virus into the blood
permissive infection
virus enters host and synthesizes its componets and assembles and are released. Cell usually dies
non- permissive infection
transforms the host cell and integrates its DNA into the hosts genome. Cell remains alive
