bacterial pathogenicity Flashcards
what is the definition of a pathogen?
an organism capable of causing disease
what is the definition of a commensal?
an organism part of the normal flora
what is the definition of pathogenicity?
the ability to cause disease
what is the definition of virulence?
the ability to cause severe disease
describe the stages in the lifecycle of a parasite
Enter
Attach
Colonise
Evade host immunity
Produce harmful proteins
Disseminate
Release from host
what are microorganisms?
agents of infectious disease
what effect do most microorganisms have on humans?
none, most microorganisms are harmless for humans
what are the divisions of microorganisms?
- bacteria
- fungi
- viruses
- prions
- parasites
what is colonisation?
when microbes find a new host and start to multiply
what is another term for microorganisms?
microbes
what is the normal flora?
a balance developed between colonised microbes and humans
what is the term used if a microbe causes disease?
infection
what is the term used if an infection’s source of microbe is patient’s own flora?
endogenous infection
what is the term used if an infection’s source of microbe is from outside the patient’s body?
exogenous infection
what is a primary pathogen?
microbes that always cause disease in a new susceptible human
what is an opportunistic pathogen?
microbes that cause disease only in immunocompromised patients eg microbes from normal flora
what is the microbes carrier state?
when the microbe remains in the human body for some time after infection
overview of bacterial infections
innate immune system vs normal flora
what is the germ theory of disease?
- The microbe must be present in every case of the disease
- The microbe must be isolated from the diseased host and grown in pure culture
- The disease must be reproduced when a pure culture is introduced into a susceptible host
- The microbe must be recovered from an experimentally infected host
what are roots of microbial entry?
- ingestion
- inhalation
- injection
- across mucous membranes
- into ear
- transplacental
what is an example of microbial entry via ingestion?
salmonella
what is an example of microbial entry via inhalation?
tuberculosis
what is an example of microbial entry via injection?
hep B
what is an example of microbial entry via mucous membranes?
trepomena pallidum
what is an example of microbial entry via the ear?
pseudomonas aeruginosa
what is an example of microbial entry via transplacental?
cytomegalovirus
what are sources of microbial entry?
Person-to-person
- Contaminated blood or other bodily fluids
- Touch
- Saliva
- Air
Fomites (objects)
Insects
Water
Food
describe a prokaryotic cell?
what is the method of attatchement of bacteria?
pili (hairlike)
- proteinaceous
- overcome mechanical forces
- specificity to host and tissue
describe UTIs
urinary tract infection
- very common in women
- colonise from faeces
what is the host protection from uti’s?
- flushing action of urine
how does the bacteria in UTIs persist against urine?
- Bacteria produce specialised adhesive structures to circumvent flushing action
- Adheres to bladder mucosal cells
- E. coli usually isolated
what is incapsulated bacteria?
bacteria covered with a polysaccharide capsule- related to immune response
give an example of a encapsulated infection
meningitis
what is the capsular function?
Mediate adhesion
Immune evasion
Protection from desiccation (drying out)
Reserves of carbohydrate
Encapsulated bacteria give rise to smooth colonies
Capsule material gives rise to ‘capsular antigens’
where are exotoxins produced?
inside most gram- POSITIVE bacteria
where are endotoxins produced?
wall of gram- NEGATIVE bacteria
endotoxin??
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