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Flashcards in Germ Warfare Deck (29)
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1

What is an infection?

A disease caused by a pathogen

2

Define the term pathogenicity.

The ability to cause disease

3

What is a pathogen?

A micro-organism that can invade the body and cause disease

4

Define the term virulence.

A pathogen's power to cause severe disease

5

What is an endogenous infection?

A disease arising from a pathogen already present in the body but previously asymptomatic. 

6

What is an exogenous infection?

A disease arising from a pathogen not normally present in the body which came from the environment. 

7

What is zoonosis?

An animal disease that can spread to humans

8

Describe the properties of bacillus anthracis.

  • Gram positive bacterium
  • Causative agent of anthrax
  • Infects wild and domestic animals 
  • Produces spores tht can survive in the soil for long periods of time
  • Category 3 pathogen 

9

What are the characteristics of a category 3 pathogen?

  • Humans are rarely infected
  • There are multiple forms of th disease
  • High mortality in some forms of the disease

10

What are the types of anthrax?

  • Cutaneous anthrax
  • Inhalation anthrax
  • Gastrointestinal anthrax
  • Injection anthrax

11

Describe the characteristics of cutaneous anthrax.

  • >95% of cases
  • Usually acquired by direct contact with infected animals or animal products.
  • Incubation period is 1-12 days.
  • The initial puritic papule gradually becomes a vesicular or bullous lesion, surrounded by extensive non-pitting oedema.
  • The central part becomes necrotic and haemorrhagic. 
  • Finally there is classic black eschar - falls off in 1-2 weeks. 

12

Describe the characteristics of inhalation anthrax.

  • Very rare.
  • Occurs after inhalation of spores.
  • Incubation period is less than one week.
  • It presents as flu-like illness with non-productive cough, leading to pneumonia bacteraemia. 
  • High mortality rates (45-85%).

13

What are the options for treatment of anthrax?

  • Antibiotics
    • Cutaneous anthrax
      • Ciprofloxacin or doxycycline
      • 7-10 days
    • Systemic anthrax
      • Ciprifloxacin with either linezolid or dindamycin
  • Monoclonal antibody preparations (antitoxin)
  • Vaccination

14

What is the relationship between pathogenicity and virulence?

  • The capacity of an organism or agent to cause disease reflects its relative pathogenicity. 
  • Virulence is the measure of the pathogenicity of an organism or agent to cause disease despite host resistance mechanisms.
  • It is affected by numerous variables:
    • Number of infecting organisms or agents (infectivity)
    • Route of entry into the body
    • Specific and non-specific host defence mechanisms
    • Intracellular growth replication 
    • Virulence factors of the organism or agent

15

What is an obligate pathogen?

  • Almost always associated with disease 
  • Examples:
    • Bacillus anthracis
    • HIV

16

What is a conditional pathogen?

  • May cause disease if certain conditions are met
  • Example:
    • Staphylococcus aureus

17

What is an opportunistic pathogen?

  • Usually only infects immuno-compromised host
  • Example
    • Cryptococcus neoformans

18

What are the characteristics of successful pathogens?

  • Survival and transmission in the environment 
  • Attachment to the surface of the host 
  • Overcoming the body defences against infection 
  • Ability to damage the host, e.g. by toxin production

19

What are the steps of infection?

  • Recognition
  • Attachment and entry
  • Multiplication
  • Evasion of host defence
  • Shedding 
  • Damage 

20

What are the virulence factors of a pathogen?

  • Toxin secretion (toxigenesis)
  • Pilus formation 
  • Capsule 
  • Iron transport systems 
  • Adhesion factors (adhesins)
  • Enzymes
  • Antibiotic resistance

21

Describe the properties of Staphylococcus aureus.

  • Widespread gram positive bacteria
    • Natural microbiota of the skin 
    • ~40% carriage
  • Versatile pathogen associated with wide range of diseases
    • Minor skin infections 
    • Food poisoning 
    • Toxic shock syndrome 
    • Endocarditis 
    • Haemolytic pneumonia
  • Complex pathology

22

Describe the properties of a virus.

  • Virus architecture is unique and bears no resemblance to any other living cell.
  • Only contains the parts needed to enter and control a host cell.
  • Essentially a nucleic acid (DNA or RNA) enclosed in a protein shell.
  • Small (nm). 

23

What are protozoa?

Single celled eukaryotes

24

What are the classifications of protozoa?

  • Sporozoa - intracellular parasites
  • Flagellates - possess tail-like structures for motility 
  • Amoeba - use temporary cell body projections (pseudopods)
  • Ciliates - move by beating multiple hair-like structures (cilia)

25

Describe the characteristics of fungi.

  • Eukaryotic
  • Multinucleate or multicellular organisms
  • Yeasts are single-celled
  • Thick carbohydrate wall containing chitin and glucans 
  • Part of normal microbiota as well as being pathogens
  • Fungal infections = 'mycoses'

26

Describe the common fungal infection, cryptococcosis.

  • Cryptococcus neoformans
  • Encapsulated yeast
  • Lab diagnosed by india ink 
  • Mainly treated with amphotericin B
  • Affects lungs or meninges

27

What is the term used for all parasitic worms?

Helminths

28

What are the 3 main groups of helminths important in humans?

  • Cestoda - tapeworms
  • Trematoda - flukes
  • Nematoda - roundworms
  • Infections are most common in tropical/subtropical climates

29

What kind of infections are caused by flukes?

  • Urinary 
  • Intestinal