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Infection > Lecture 2.1: Infection and Disease > Flashcards

Lecture 2.1: Infection and Disease Flashcards

1
Q

What is Symbiosis?

A

A close relationship between two different type of organisms in a community

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2
Q

Types of Symbioses (3)

A

Mutualistic
Commensalism
Parasitism

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3
Q

Mutualistic Symbiosis: Effects and Examples

A

Species A and Species B Benefit
E.coli in human intestine

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4
Q

Commensalism Symbiosis: Effects and Examples

A

Species A Benefit and Species B Unaffected
Microbes on Human Skin

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5
Q

Parasitism Symbiosis: Effects and Examples

A

Species A Benefit and Species B Harmed
TB, Fungi, Helminiths

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6
Q

What is Infection?

A

Refers to the presence and growth of microorganism in a host, not including normal flora

An infection may or may not cause a disease

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7
Q

What is a Pathogen?

A

An organism that causes damage to the host

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8
Q

Types of Pathogens (3)

A

• Opportunistic
• Primary
• Zoonotic

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9
Q

Opportunistic Pathogens

A

A group of microorganisms that do not usually infect healthy hosts

But can produce infections in hospitals, to immuno-depressed persons or those patients presenting underlying diseases as cystic fibrosis, which favours infection

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10
Q

Primary Pathogens

A

They can cause disease in a host regardless of the host’s resident microbiota or immune system

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11
Q

Zoonotic Pathogens

A

A zoonosis is an infectious disease that has jumped from a non-human animal to humans

Zoonotic pathogens may be bacterial, viral or parasitic

They may also involve unconventional agents and can spread to humans through direct contact or through food, water or the environment

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12
Q

What is Pathogenicity?

A

The ability of microorganism to cause disease

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13
Q

Phases of Infection (5)

A

• Incubation Stage
• Prodrome Stage
• Illness/ Specific Symptoms
• Recovery
• Health

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14
Q

Phases of Infection: Incubation Stage

A

The time between the acquisition of the pathogen and the onset of symptoms

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15
Q

Phases of Infection: Prodrome Stage

A

Nonspecific symptoms, such as fever or tiredness, occur

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16
Q

Phases of Infection: Disease Specific Symptoms

A

Increase rapidly

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17
Q

Phases of Infection: Recovery

A

As the host immune system and/or treatments effectively reduce the number of pathogens, symptoms decrease

This also called the convalescence stage

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18
Q

Phases of Infection: Health

A

• Ultimately, symptoms disappear and the individual returns to health
• However, some individuals may become chronic carriers of the infectious
agents or develop latent infections that can reoccur

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19
Q

What is a Symptom?

A

Experienced by the individual affected by the disease

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20
Q

What is a Sign?

A

Can be detected by someone other than the individual affected by the disease

21
Q

What is a Portal of Entry?

A

It is a site through which microorganisms enter the susceptible host and cause infection

22
Q

What are some examples Portal of Entry?

A

• Mucous Membranes
• Skin
• Placenta
• Respiratory Tract
• Gastrointestinal Tract

23
Q

What is Virulence?

A

The degree of pathogenicity

24
Q

What is the Virulence Factor?

A

Enable a host to replicate and disseminate within a host in part by subverting or eluding host defences

25
Q

How do Virulence Factors help bacteria?

A

• Invade the host
• Evade host defences
• Cause disease

26
Q

What is included in Virulence Factor? (5)

A
  1. Attachment (via adhesins)
  2. Colonisation (& Enzymes)
  3. Invasiveness
  4. Toxins (& Enzymes)
  5. Inhibition of Phagocytosis
27
Q

Staphylococci Infection

A

• Gram-positive cocci that grow in clumps
• Yellow-ish crust around mouth
• Staph. aureus is one of the most important
pathogen
• Causing a variety of pyogenic infections and
toxin-mediated illnesses
• Antibiotic Resistance

28
Q

Coagulation as a Defence against Microbes

A

• Coagulation is an innate defence mechanism
against microbial pathogens
• It traps and immobilises invading bacteria in a
clot

29
Q

Coagulase as a Virulence Factor

A

• S. aureus secretes two proteins that promote coagulation
• Coagulase (Coa) and von Willebrand factor binding protein (vWbp)
• Promote similar modifications of the coagulation cascade during host infection
• Both of these proteins activate prothrombin nonproteolytically

30
Q

Coagulase Test

A

Fibrinogen Plasma + Coagulase
If Coagulase is present then a Fibrin Visible Clot can be seen

31
Q

What is key about coagulase-negative staphylococci?

A

Coagulase-negative staphylococci are generally considered non-pathogenic
apart from Staph. epidermidis and Staph. saprophyticus

32
Q

Virulence Factor: Invasin

A

• Hyaluronidase enzyme is produced by Staphylococcus aureus
• It is responsible for the spread of then organism during infection
• Hyaluronidase enzyme is capable of degrading hyaluronic acid (HA)
• This is an essential component of the extracellular matrix of human tissues

33
Q

Streptococcus

A

• Gram positive spheres (cocci) like staphylococci
• Streptococci appear in strips (chains) on gram stain not clusters
• 1µm in diameter and usually capsulated
• Facultative anaerobes
• They are catalase negative
• Non-sporing bacteria and non-motile

34
Q

Pharyngitis

A

• A variety of bacteria can cause infection in the pharynx
• A classic infection is strep throat
• Caused by Streptococcus pyogenes
• Contains M proteins which inhibits phagocytosis
• Produces pyrogenic toxins which cause the symptoms seen with pharyngitis
• Group A streptococci can cause abscesses on the tonsils
• S. pyogenes can cause scarlet fever and toxic shock syndrome

35
Q

Virulence Factor: Streptococcus

A

• Secretes a hemolysin that causes haemolysis
• Haemolysis is the breakdown of red blood cells (RBC)
• Beta haemolysis is caused by two haemolysins O and S
• Alpha haemolysis is caused by hydrogen peroxide produced by the
bacterium, oxidising haemoglobin to green methemoglobin

36
Q

Name Post Streptococcal Illnesses (4)

A

• Glomerulonephritis
• Streptococcal Toxic Shock Syndrome
• Scarlet Fever
• Acute Rheumatic Fever

37
Q

Staphylococcus aureus: Gram? Shape? Where do they infect?

A

• Gram Positive
• Cocci
• Bacteria colonise skin and nasopharynx

38
Q

Staphylococcus aureus: How do they evade host defences? (3)

A

• Using Protein A
• Coagulase (forms fibrin clot)
• Haemolysins and Leukocidins (destroy RBC AND WBC)

39
Q

Staphylococcus aureus: How do they carry out deep invasion?

A

• Hyaluronidase (breaks down connective tissue)
• Staphylokinase (lyse clots)
• Lipase (breaks fat)
• Can produce an A-B Toxin (TSS, Scalded Skin Syndrome)

40
Q

Streptococcus pyogenes: Gram? Shape? Where do they infect?

A

• Gram Positive
• Cocci
• Skin

41
Q

Streptococcus pyogenes: What Virulence Factors does it have? (6)

A

• Hyaluronidase (breaks down connective tissue)
• Dnase
• M protein
• Streptokinase (plasminogen -> plasmin ->fibrinolyisn)
• Lipase (breaks fat)
• Can produce an A-B Toxin (TSST, Scalded Skin Syndrome)

42
Q

Streptococcus pyogenes: What can make it change from normal skin flora to pathogenic? (6)

A
  1. Trauma inoculates bacteria into skin
  2. Bacteria colonise
  3. Inflammation
  4. Pustular lesions and honeycomb like crust
  5. Deeper infection
  6. May lead to anti-streptoccal Ab reactions glomerulonephritis
43
Q

Signs & Symptoms of Streptococcal Respiratory Diseases

A

• Sore throat
• Difficulty swallowing
• May progress to scarlet or rheumatic fever

44
Q

How and when are Streptococcal Respiratory Diseases Spread?

A

• Spread via respiratory droplets
• Occurs most often in winter and spring

45
Q

How to treat Streptococcal Respiratory Diseases?

A

• Often confused with viral pharyngitis
• Penicillin is an effective treatment

46
Q

When does Pathogenesis of Streptococcal Respiratory Diseases occur?

A

• When normal microbiota are depleted
• Large inoculum is introduced
• Adaptive immunity is impaired

47
Q

What causes Scarlet Fever?

A

Caused by Group A streptococci

48
Q

Who is most commonly affected with Scarlet Fever?

A

Usually seen in children under age of 18 years

49
Q

What are Symptoms of Scarlet Fever? (8)

A

• Symptoms usually begin with appearance of a rash
• Tiny bumps on the chest and abdomen (can spread to whole body)
• Appears redder in armpits and groin
• Rash lasts 2-5 days
• Very sore throat with yellow or white papules
• Fever of 101˚F/38.3˚C or higher
• Lymphadenopathy in neck
• Headache, body aches, and nausea

Infection (21 decks)

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