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Microbiology > M4- Sources of microorganisms > Flashcards

M4- Sources of microorganisms Flashcards

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Biology 101 flashcards
1
Q

Describe how pathogenesis occurs?

A
  • reservoir of pathogens
  • adhere/colonize and invade
  • evade host defences
  • multiply/complete its life cycle
  • exit host (host is damaged)
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2
Q

Name some reservoirs in humans

A
  • hep A and B
  • influenza
  • measles
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3
Q

is animals source or reservoir?

A
  • Zoonoses or Zoonotic diseases
  • Accidental infection of man
  • May involve vector, rat to tick to man
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4
Q

is the environment source or reservoir?

A

• Soil & Water
• Contaminated with sewage, or naturally
contain animal excreta
• include opportunistic pathogens that can infect immuno-suppressed

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5
Q

Describe a source.

A
  • animate/inanimate (animal or environment )
  • (human) period of infectivity
  • Casual (hours), acute (days), Transient(weeks) , chronic (months +)
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6
Q

what are signs of active carrier state?

A

overt clinical presentation

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7
Q

what are signs of convalescent carrier state?

A

recovering but still carrier

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8
Q

what are signs of a healthy carrier state?

A

no overt signs of illness

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9
Q

what are signs of a incubator carrier state?

A

maintaining large numbers of pathogens prior to illness

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10
Q

what is a natural way to exit a host?

A

sneezing, shedding

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11
Q

what is the artificial way to exit a host?

A

blood, salvia,aerosols (drill)

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12
Q

Describe the direct spread/contact of disease

A
  • from one person to another
  • horizontal= between each other
  • vertical= mother to child
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13
Q

Describe indirect spread.

A

formite - dental instruments

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14
Q

Describe air-borne spread.

A

droplets/aerosols

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15
Q

Describe vector-borne spread.

A

insects i.e flea

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16
Q

How do microbes escape from the body?

A
  • tears
  • salvia
  • nasal secretions
  • semen
  • urine
17
Q

what can vary during the course of a disease?

A

reservoirs

18
Q

what is exogenous?

A

Infective material derived from outside patients body

19
Q

Describe an endogenous infection?

A

– Bacteria/Fungi part of natural microbiota (commensal)

– Misplaced, transfer from non-sterile to normally sterile site : S. sanguinis mouth to blood to heart & endocarditis

– Change in natural flora
: e.g. antibiotic therapy
C.albicans or C.difficile

20
Q

Name some infections by exogenous bacteria.

A
  • tuberculosis (humans)
  • pneumoniA (soil/water)
  • tetanus (soil)
21
Q

how does it go from commensal(mutualistic) to pathogen?

A
  • damage to epithelium (burns or wounds)
  • presence of forge in body (prosthesis, catheters, absence of shedding surface and formation of biofilms)
  • transfer of bacteria to incorrect site (mouth to lower respiratory tract)
  • suppression of immune system (cancer therapy)
  • infection by exogenous pathogen
  • disruption of microflora by antibiotics
22
Q

Describe biofilms.

A
  • Organism behaving as part of multi-cellular community.
  • 3 dimensional structure
  • Contains interfaces
  • Spatial heterogeneity
  • Permeated by water channels
  • Organisms resistant to antimicrobial agents & host defenses
23
Q

Describe an oral biofilm.

A
  • dental plaque
  • multi species biofilm (no single biofilm)
  • can be tightly or loosely packed on the top of the tooth
  • complicated
24
Q

How do you establish disease?

A
  • dose of infective agent
  • virulence of organisms
  • susceptibility/resistance of host
25
Q

Describe the stages of development of infectious disease (pathogenesis).

A
  • source of the microbe
  • escape from the source
  • spread to a new host
  • entry into the host
  • infection of the host
  • damage to the host
26
Q

what is good dental practise?

A
  • primary sources- secretions, salvia , blood :gloves, mask,gown, aspiration
  • secondary source- surgery equipment e.g. drill :cleaning disinfection sterilisation
27
Q

what challenges faced by pathogenic bacteria in water?

A
  • low temperature
  • low nutrient and osmotic strength
  • pH near neutral
  • O2 available• respiratory metabolism
  • free iron available
  • adhesins to stick to rocks
28
Q

what challenges faced by pathogenic bacteria in human?

A
  • higher temperature (37oC)
  • higher osmotic strength, C and energy sources abundant
  • low pH then higher pH
  • low or no O2
  • fermentative metabolism
  • iron bound to haem
  • adhesins to stick to cells
  • exposure to bile salts
29
Q

what microbes are more likely to poise a threat?

A

endogenous microbe adapted to host and adhere

30
Q

what does infection control requires knowledge of?

A 
–  Source of infection 
–  Transmission
–  Exogenous
–  Endogenous
–  Commensal/Microflora threat

Microbiology (30 decks)

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