Transmissions of Infections Flashcards
what are the steps of the chain of infection?
- infectious agent
- reservoirs
- portal of exit
- means of transmission
- portal of entry
- susceptible host
what is meant by virulence?
the ability of the microbe to cause disease
what is meant by dose?
• the number of microbes entering the body
what is dose normally expressed as?
infectious dose 50 (ID50)
how do you know if a microbe is MORE infectious?
a LOW ID50
what are exotoxins?
a toxin released by bacteria into the external environment
what is an endotoxin?
a toxin that is released from GRAM NEGATIVE bacterial cell walls
what is an example of a periodontal pathogen?
P. gingivalis
what is a leukocidin?
a white cell toxin
what is an enterotoxin?
a toxin produced in/affecting the intestines
give examples of reservoirs:
- humans
- animals
- environment
- contaminated surfaces
give an example of an environmental pathogen?
CLOSTRIDIUM TETANI spores in soil
what are the different phases of an infection?
- patients in acute phase
- patients in the prodromal phase
- healthy carriers
what is meant by the incubation period of a pathogen?
the time between contamination and the development of symptoms
what do long incubation periods permit?
- longer time periods when the infecting microbe may be spread to others
- greater spread of the disease due to more human contact
what is an infected person that shows no clinical evidence the disease called?
asymptomatic carrier
what is meant by colonisation?
the presence of the microorganism in/on a host with growth and multiplication but without overt clinical expression (infection)
when is meant by an endogenous infection?
infection caused by members of the normal flora
give an example of an endogenous infection:
periodontal disease
what is meant by an exogenous infection?
infection caused by microbes from external sources
give an example of an exogenous disease:
influenza virus
modes of escape from the source can be?
- natural
* artificial
example of a natural mode of exit?
• coughing/sneezing
example of an artificial mode of exit?
blood donation/dental hand piece aerosols
what are the 4 hazard groups that human pathogens are classified into?
- ability to cause infection
- severity of the disease that may result
- vaccine & treatment availability
- risk of population spread
what is meant by the “R” number?
the number of cases one case generates on average over the course of its infectious period
what factors affect the “R” number?
- duration of infectivity
- infectiousness
- number of susceptible people
why are aerosols problematic in reverence to infection?
aerosols can aid in transmission
how can aerosols in dentistry be mitigated in an attempt to slow down/prevent transmission?
- use of rubber dams
- high/low volume aspiration
- surgery ventilation
how long does Influenza A&B survive on steel and plastic?
24-48 hours
how long does Influenza A&B survive on cloth, paper & tissues?
8-12 hours
what are the 5 moments for hand hygiene within the practise?
- before touching a patient
- before clean/aseptic procedure
- after body fluid exposure
- after touching patient
- after touching patient surroundings
give examples of human portals of entry:
- respiratory tract
- gastro-intestinal tract
- open/surgical wounds
- medical devices/sharps injuries
- sexual contact
why are susceptible hosts more at risk of infection?
- underdeveloped immune system
- declining immune system (elderly)
- breaks in the skin
- medical devices
