sem 1 - definitions revision lectures 1-7 Flashcards
standard infection control
the same cross infection control procedure must be used for all patients
enrichement media
addition of blood/serum/extract will support growth of fastidious organisms
selective media
presence of a specific substance permits the growth of one substance over the other
differential media
facilitates identification
virulence test
can be critical in pathogenesis eg adhesin and toxin
define Kochs postulates
- micro-organism which is present in only disease
- must be isolated and grown in pure culture
mutualistic
relationship which host and organism gain mutual value
parasitic
live on ir in living creatures creating damage to the host
pathogen
microbe capable of causing host damage
virulence
the capacity of the microbe to cause damage to the host
virulence factor
component of the pathogen that damages the host
list the virulence factors
adhesin invasion impedin agressin and modulin
obligate pathogens
must cause disease for transmission
opportunistic pathogens
do not have to cause disease for transmisssion
accidental pathogens
disease that hinders or prevents transmission
epidemiology
the study of occurrence spread and control of disease
prevalence
proportion of population affected
exogenous
infective material derived from outside patients body
endogenous
bacteria fungi transferred from sterile to non-sterile state
commensal to pathogen
- damage to epithelium
- presence of foreign body
- transfer of bacteria to incorrect site
- immune suppression
- infection by exogenous pathogen
- disruption of microflora by antibiotics
Five Is
- Inhalation
- inocolation
- ingestion
- mother to Infant
- intercourse
HAI infections
6.4% of patients acquire infection during hospital stay
factors which influence disease transmission
Agent
environment
host
Membrane attack complex (MAC)
C3b activates producing C5a and C5b which are cells that bind to kill bacteria and mark cells for phagocytosis
virulence factors from staphylococcu aureus
adhesin - fibrinogen binding protein
kills leukocytes - leukocidin (PVL)
shock, rash desquamtion - TSST-1
superantigen
massive release of cytokines and innapropriate immune response
activates 1 in 5 T cells
Panton Valentine Leukocidin
PVL + alpha toxin linked with CA-MRSA responsible for necrotizing pneumonia and severe skin infections
examples of evasion of host defences
superantigens
protein A - binds to FC portion of IgG antibody
Coagulase
forrms staphylthrombin promotes the conversion of fibrinogen to fibrin and therefore clotting
strep throat
Group A streptococci (GAS)
beta heamolytic S.pyogenes
scarlet fever
severe form of strep throat associated with rash
Acute streptococcal gingivitis
- infective gingivae red/ swollen/ oedematous often follow sore throat
rheumatic fever
1-4 weeks after sore throat/scarlet fever
- delayed reaction due to inadequate recovery from GAS
identification
haemolysis is used to classify streptococci
Lancefield group A
- serotyping of cell wall carbohydrate
- GAS bacitracin sensitive
antibiotic treatment of strep throat and GAS disease
penicillin V course
amoxicillin
