Microbial Infection Flashcards Preview

MD2001 > Microbial Infection > Flashcards

Flashcards in Microbial Infection Deck (56):
1

What are Koch's Postulates?

+ 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

2

What does the innate immune system consist of?

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

3

What are features of normal microbiota?

+ 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

4

What are the physical barriers of the body?

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

5

What are the features of skin as a physical barrier?

+ Secretes sebum and fatty acids to inhibit growth

+ Microbes have evolved mechanisms to penetrate skin

6

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

+ Particles settle on sticky mucus of respiratory epithelium

+ Debris transported by cilia to oropharynx where it is swallowed

7

What are some of the chemical barriers within the body?

+ Mucus

+ Antimicrobial proteins
-lysozyme
- lacroferrin
- defensins

+ Gastric acid

+ Plasma proteins
- complement
- C-reactive protein
- Mannise-binding lectin (MBL)
- transferrin

8

Name different types of phagocytes

+ Macrophages
+ Neutrophils
+ Monocytes
+ Dendritic cells
+ Mast cells

9

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

+ Invading host tissues
+ Exerting effects from mucosal surfaces

10

What is a commensal?

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

11

What is a pathogen?

A micro-organism capable of causing an infection

12

What is pathogenicity?

The capacity to cause disease

13

What is virulence?

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

14

What are the different types of pathogens?

+ Obligate
+ Conditional
+ Opportunistic

15

What is an obligate pathogen?

+ Almost always associated with disease

+ E.g HIV

16

What is a conditional pathogen?

+ May cause disease of certain conditions are met

+ E.g Bacteroides fragilis, Staphylococcus aureus

17

What is an opportunistic pathogen?

+ Usually only infects immunocompromised hosts

+ E.g Pneumocystis jiroveci

18

What are the steps of infection?

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

19

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

+ 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

20

What is tissue tropism?

+ 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

21

What are factors that may influence tissue tropism?

+ Presence of cell receptors
+ Transcription factors
+ Local temperature
+ Physical barriers
+ pH

22

What microbe targets nerve cells?

Varicella zoster virus (VZV)

23

What microbe targets the upper respiratory tract?

Rhinovirus

24

What microbe targets the liver cells?

Hepatitis B virus (HBV)

25

What microbe targets the gastric mucosa?

Helicobacter pylori

26

Wha microbe targets the intestinal epithelium?

Campylobacter jejuni

27

What microbe targets B lymphocyte cells?

Epstein Barr virus (EBV)

28

What microbe targets T lymphocyte cells?

Human Immunodeficiency virus (HIV)

29

What microbe targets urethral epithelium?

Neisseria gonorrhoeae

30

What microbe targets nasopharyngeal epithelium?

Neisseria meningitidis

31

What microbe targets intestinal epithelium?

Vibrio cholerae

32

Name virulence factors

+ 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

What are the two types of bacterial toxins?

+ Endotoxins
+ Exotoxins

34

What are features of endotoxins?

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

35

What are features of exotoxins?

+ 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

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

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

37

What are some important examples of antibiotic resistance?

+ Methicillin-resistant Staphylococcus aureus (MRSA)

+ Vancomycin-resistant Staphylococcus aureus (VRSA)

+ Multi-resistant Mycobacterium tuberculosis

+ HIV

+ Malaria

38

Upon what factors does transmission depend?

+ 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

What is horizontal transmission?

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

What is vertical transmission?

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

41

What are examples of diseases transmitted via the respiratory route?

+ TB
+ Influenza
+ Common cold

42

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

+ Cholera
+ Shigellosis

43

What are examples of diseases transmitted via the venereal route?

+ Chlamydia
+ HIV
+ Human papilloma virus (HPV)

44

What are examples of diseases transmitted via the skin?

+ Ringworm
+ S. aureus

45

What are examples of diseases transmitted via the perinatal route?

+ HIV
+ Meningitis
+ Conjunctivitis

46

What are examples of diseases transmitted via the semen?

+ HIV
+ Hepatitis B
+ Cytomegalovirus

47

What are examples of diseases transmitted via the blood?

+ HIV
+ Hepatitis B
+ Malaria


48

What are examples of diseases transmitted via the breast milk

+ HIV

49

What are examples of diseases transmitted via the saliva?

+ EBV
+ Herpes simplex virus (HSV)

50

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

+ Invertebrate
+ Vertebrate

51

What are examples of invertebrate vectors?

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

+ Shellfish: e.g hepatitis A, cholera

52

What are examples of vertebrate vectors?

+ Mammals: e.g rabies, leptospirosis, tapeworm

+ Birds: e.g psittacosis, salmonella

53

What are fomites?

Objects or materials which are likely to carry infections

54

What are some examples of fomite transmission?

+ Door handles
+ Cutlery
+ Computer keyboards
+ Clothing
+ Phones
+ Pens

55

What are nosocomial infections?

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

+ Major public health concern

56

What are examples of nosocomial antibiotic resistance?

+ Clostridium difficile
+ Staphylococcus aureus