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MD2001 > Microbial Infection > Flashcards

Microbial Infection Flashcards

1
Q

What are Koch’s Postulates?

A

+ The bacteria must be present in every case of disease
+ The bacteria must be isolated from the host with the disease and grown in pure culture
+ The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host
+ The bacteria must be recoverable from the experimentally infected host

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2
Q

What does the innate immune system consist of?

A

+ Normal macrobiota
+ Physical barriers
+ Chemical barriers
+ Phagocytic Cells

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3
Q

What are features of normal microbiota?

A

+ More prokaryotic cells than human cells in the body
+ Offers protection by competing with pathogens for colonisation sites
+ Produce antibiotic substances suppressing growth of competing organisms (bacteriocins)
+ May produce toxic metabolic products to inhibit other micro-organisms
+ May alter pH e.g Lactobacilli
+ Suppressed by antibiotics

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4
Q

What are the physical barriers of the body?

A

+ Skin
+ Mucomuciliary clearance
+ Flushing (urinary tract)
+ Peristalsis (GI tract)

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5
Q

What are the features of skin as a physical barrier?

A

+ Secretes sebum and fatty acids to inhibit growth

+ Microbes have evolved mechanisms to penetrate skin

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6
Q

What are the features of mucomuciliary clearance as a physical barrier?

A

+ Particles settle on sticky mucus of respiratory epithelium

+ Debris transported by cilia to oropharynx where it is swallowed

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7
Q

What are some of the chemical barriers within the body?

A

+ Mucus

+ Antimicrobial proteins

  • lysozyme
  • lacroferrin
  • defensins

+ Gastric acid

+ Plasma proteins

  • complement
  • C-reactive protein
  • Mannise-binding lectin (MBL)
  • transferrin
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8
Q

Name different types of phagocytes

A 
\+ Macrophages 
\+ Neutrophils 
\+ Monocytes 
\+ Dendritic cells
\+ Mast cells
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9
Q

What are the two ways that a micro-organism can an cause infection by causing ill-health?

A

+ Invading host tissues

+ Exerting effects from mucosal surfaces

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10
Q

What is a commensal?

A

A micro-organism which forms part of the normal host microbiota

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11
Q

What is a pathogen?

A

A micro-organism capable of causing an infection

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12
Q

What is pathogenicity?

A

The capacity to cause disease

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13
Q

What is virulence?

A

Measure of the capacity to cause disease i.e degree of pathogenicity

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14
Q

What are the different types of pathogens?

A

+ Obligate
+ Conditional
+ Opportunistic

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15
Q

What is an obligate pathogen?

A

+ Almost always associated with disease

+ E.g HIV

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16
Q

What is a conditional pathogen?

A

+ May cause disease of certain conditions are met

+ E.g Bacteroides fragilis, Staphylococcus aureus

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17
Q

What is an opportunistic pathogen?

A

+ Usually only infects immunocompromised hosts

+ E.g Pneumocystis jiroveci

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18
Q

What are the steps of infection?

A 
> Recognition
> Attachment & entry
> Multiplication
> Evasion of host defences
> Shedding
> Damage
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19
Q

What are ways that infection can be established in normally healthy hosts?

A

+ Microbes with specific mechanisms for attachment and penetration of host’s body surfaces

+ Microbes introduced into host by biting arthropods

+ Microbes introduced into host via skin wounds or animal bites

+ Microbes able to infect only when host defences are impaired

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20
Q

What is tissue tropism?

A

+ Affinity for a specific tissue

+ Defines the cells and tissues of a host which support the growth of a particular microbe

+ Some microbes have a broad tissue tropism, infecting many types of cells and tissues

+ Others may primarily infect a single tissue

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21
Q

What are factors that may influence tissue tropism?

A 
\+ Presence of cell receptors
\+ Transcription factors
\+ Local temperature
\+ Physical barriers
\+ pH
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22
Q

What microbe targets nerve cells?

A

Varicella zoster virus (VZV)

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23
Q

What microbe targets the upper respiratory tract?

A

Rhinovirus

24
Q

What microbe targets the liver cells?

A

Hepatitis B virus (HBV)

25
Q

What microbe targets the gastric mucosa?

A

Helicobacter pylori

26
Q

Wha microbe targets the intestinal epithelium?

A

Campylobacter jejuni

27
Q

What microbe targets B lymphocyte cells?

A

Epstein Barr virus (EBV)

28
Q

What microbe targets T lymphocyte cells?

A

Human Immunodeficiency virus (HIV)

29
Q

What microbe targets urethral epithelium?

A

Neisseria gonorrhoeae

30
Q

What microbe targets nasopharyngeal epithelium?

A

Neisseria meningitidis

31
Q

What microbe targets intestinal epithelium?

A

Vibrio cholerae

32
Q

Name virulence factors

A

+ Toxin secretion (toxigenesis)
- produced by bacteria and fungi

\+ Antibiotic resistance
\+ Pilus formation
\+ Capsule
\+ Iron transport systems
\+ Adhesion factors (adhesins)

+ Enzymes
- e.g proteases, DNAses, lipases

33
Q

What are the two types of bacterial toxins?

A

+ Endotoxins

+ Exotoxins

34
Q

What are features of endotoxins?

A

+ Low toxicity
+ Part of the cell wall of Gram negative bacteria
+ Lipopolysaccharide
+ Low specificity

35
Q

What are features of exotoxins?

A

+ Highly toxic
+ Secreted from bacterial cells
+ Produced by both Gram positive and negative bacteria
+ Can be converted into toxoids for vaccine use
+ E.g tetanus toxin, cholera toxin, botulinum toxin

36
Q

What are the features of microbes/bacteria with antibiotic resistance?

A 
\+ Resistance genes on plasmids
\+ Production of enzymes e.g β-lactamase
\+ Impermeability
\+ Efflux mechanisms
\+ Alteration of target site
37
Q

What are some important examples of antibiotic resistance?

A

+ Methicillin-resistant Staphylococcus aureus (MRSA)

+ Vancomycin-resistant Staphylococcus aureus (VRSA)

+ Multi-resistant Mycobacterium tuberculosis

+ HIV

+ Malaria

38
Q

Upon what factors does transmission depend?

A

+ The number of micro-organisms shed

+ The number of micro-organisms required to infect a fresh host (the efficiency of the infection)

+ The micro-organism’s stability in the environment

39
Q

What is horizontal transmission?

A

Transmission of an infectious agent, such as bacterial, fungal, or viral infection between members of the same species that are not in a parent-child relationship

40
Q

What is vertical transmission?

A

Passage of a disease-causing agent (pathogen) from mother to baby (during the period immediately before and after birth)

41
Q

What are examples of diseases transmitted via the respiratory route?

A

+ TB
+ Influenza
+ Common cold

42
Q

What are examples of diseases transmitted via the faeco-oral route?

A

+ Cholera

+ Shigellosis

43
Q

What are examples of diseases transmitted via the venereal route?

A

+ Chlamydia
+ HIV
+ Human papilloma virus (HPV)

44
Q

What are examples of diseases transmitted via the skin?

A

+ Ringworm

+ S. aureus

45
Q

What are examples of diseases transmitted via the perinatal route?

A

+ HIV
+ Meningitis
+ Conjunctivitis

46
Q

What are examples of diseases transmitted via the semen?

A

+ HIV
+ Hepatitis B
+ Cytomegalovirus

47
Q

What are examples of diseases transmitted via the blood?

A

+ HIV
+ Hepatitis B
+ Malaria

48
Q

What are examples of diseases transmitted via the breast milk

A

+ HIV

49
Q

What are examples of diseases transmitted via the saliva?

A

+ EBV

+ Herpes simplex virus (HSV)

50
Q

What are the different vector categories for animal - human transmission (zoonoses)?

A

+ Invertebrate

+ Vertebrate

51
Q

What are examples of invertebrate vectors?

A

+ Arthropods: e.g malaria, sleeping sickness, yellow fever

+ Shellfish: e.g hepatitis A, cholera

52
Q

What are examples of vertebrate vectors?

A

+ Mammals: e.g rabies, leptospirosis, tapeworm

+ Birds: e.g psittacosis, salmonella

53
Q

What are fomites?

A

Objects or materials which are likely to carry infections

54
Q

What are some examples of fomite transmission?

A 
\+ Door handles
\+ Cutlery
\+ Computer keyboards
\+ Clothing
\+ Phones
\+ Pens
55
Q

What are nosocomial infections?

A

+ Infections acquired during a hospital stay/originating in a hospital

+ Major public health concern

56
Q

What are examples of nosocomial antibiotic resistance?

A

+ Clostridium difficile

+ Staphylococcus aureus

MD2001 (52 decks)

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