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Semester 3 > Infection 7-12 > Flashcards

Infection 7-12 Flashcards

1
Q

What is a surface?

A

Interface between a solid and either a liquid or gas

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2
Q

What are common viruses on the skin?

A

Papilloma

Herpes simplex

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3
Q

What are common bacteria on teh skin?

A

+ Staph aureus
+ Coagulase negative staphylococci
+Corynebactrium
- Enterobacterium

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4
Q

What are common fungi on the skin?

A

Yeasts

Dermatophytes - athletes foot

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5
Q

What are common parasites on the skin?

A

mites

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6
Q

What are microbiota?

A

“Commensals”
Micro-organisms carried on skin and mucosal surfaces
Normally harmless or even beneficial
Transfer to other sites can be harmful

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7
Q

What parts of the body are considered to be external?

A 
Skin
GI tract
Resp tract
Urinary tract
Make contact with external environment
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8
Q

What is a prosthetic surface infection?

A 
Internal infection from external origin
Eg:
- IV lines
- peritoneal dialysis catheters 
- prosthetic joints 
- cardiac valves 
- pacing wires
- endovascular grafts 
- ventriculo-peritoneal shunts
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9
Q

What is native valve endocarditis?

A

viridans Streptococci usually common in mouth, may get into blood stream when gums bleed.
Heart valves damaged by turbulent blood flow become good site for bacteria to colonise as they have similar receptors to those in the mouth.

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10
Q

What bacteria may cause native valve endocarditis?

A 
viridans Streptococci
Enterococcus faecalis
Staph aureus
HACEK group 
Candida (fungi)
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11
Q

What bacteria commonly cause prosthetic valve endocarditis and what other diseases might they cause?

A

coagulase negative staphylococci
Staphylococcus aureus
May also be the cause of prosthetic joint infections or cardiac pacing wire endocarditis

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12
Q

What are the processes in the pathogenesis of infection at surfaces?

A

Adherence to host cells or prosthetic surface
Biofilm formation
Invasion and multiplication
Host response - Pyogenic (neutrophils -> pus)/Granulomatous (fibroblasts, lymphocytes, macrophages -> nodular inflammatory lesions)

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13
Q

What does quorum sensing control?

A

Sporulation
Biofilm formation
Virulence factor secretion

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14
Q

What are the 3 principles of quorum sensing?

A

Signalling molecules - autoinducers (AI)
Cell surface or cytoplasmic receptors
Gene expression - co-perative behaviours and more AI production

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15
Q

How do microorganisms cause disease?

A 
Exposure
Adherence
Invasion
Multiplication
Dissemination
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16
Q

What are the challenges of management of a surface infection?

A

Adherent organisms
Low metabolic state/small colony variants
Poor antibacterial penetration into biofilm micro-organisms
Dangers/difficulties of surgery

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17
Q

What investigations are done to confirm the origin of infection for surface infections?

A

Blood cultures

Tissue/prosthetic material sonication and culture

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18
Q

What is the aim of treatment of a surface infection?

A

Sterilise tissue

Reduce bioburden

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19
Q

What treatment is given for a surface infection?

A

Antibacterials

Surgery - resect infected material

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20
Q

What preventative mechanisms are in place against surface infection?

A 
Natural surface:
- Maintain surface integrity 
- prevent bacterial surface colonisation
- Remove colonising bacteria
Prosthetic surfaces:
- Prevent contamination
- Inhibit surface colonisation
- Remove colonising bacteria
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21
Q

What is a biofilm?

A

combination of the proteoglycans produced by the bacteria and the host immune response (neutrophils and platelets) that surround the bacteria.
Allows the transfer of nutrients to the bacteria and waste away, aswell as protecting the bacteria from host immune response and antibiotics.

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22
Q

What is catheter fever?

A

Transient gram negative septicaemia from catheter removal/ insertion

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23
Q

How can infection from IV lines be prevented?

A

Use silver coated lines - poor adhesion to silver therefore less likely to be infected

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24
Q

What type of infections may not be transferrable from person to person?

A

Food/water - food poisoning organisms
Environmental - Legionella pneumophila
Animals - Rabies

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25
Q

Name some infections which require a vector for transmission.

A

Malaria, dengue - mosquitos
toxoplasmosis - cats
Lyme disease, spotted fever - ticks

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26
Q

What is an endemic disease?

A

A disease which is spreading at the usual background rate

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27
Q

What is an outbreak of disease?

A

Two or more cases linked in time and place

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28
Q

What is an epidemic?

A

A rate of infection greater than the usual background rate.

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29
Q

What is a pandemic?

A

Very high rate of infection spreading across many regions, countries and continents

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30
Q

What is R0 in infection?

A

The average number of cases one case generates over the course of its infectious period in an otherwise uninfected, non-immune population

31
Q

What are the reasons for new outbreaks, epidemics/pandemics?

A 
New pathogen (antigens, virulence factors, antibacterial resistance)
New hosts (non-immunes, healthcare effects)
New practice can cause patient and pathogen to come into contact with each other (social, healthcare)
32
Q

What is an infectious does?

A

Number of micro-organisms required to cause infection. Varies by micro-organism, presentation of micro-organism and immunity of potential host

33
Q

What does an epidemic curve show?

A

Number of people infected at each time interval

Susceptible -> infected -> recovered

34
Q

How can pathogens and vectors be intervened?

A

Reduced/eradicated:

  • antibacterials including disinfectants
  • decontamination
  • sterilisation
  • eliminate vector breeding sites
35
Q

What interventions are used on patients to remove/prevent infection?

A

Improved health - nutrition, medical treatment

Immunity - passive eg maternal antibody, intravenous immunolglobulin. Active - vaccination

36
Q

What interventions occur in practice to prevent infections?

A

Avoidance of pathogen and it’s vector:

  • Geographic
  • Protective clothing, equipment - long sleeves, trousers against mosquito bites, personal protective equipment in hospitals - gowns, gloves, masks
  • Behavioural - safe sex, safe disposal of sharps, food and drink prep.
37
Q

What interventions can be used in everyday life to prevent infection?

A

Safe water
Safe air
Good quality housing
Well designed healthcare facilities

38
Q

What is herd immunity?

A

When vaccination of a sufficient proportion of the population provides immunity for the entire population

39
Q

What are the consequences of control of disease?

A

Good:
- Decreased incidence or elimination of disease/organism e.g. smallpox, polio
Bad:
- Decreased exposure to pathogen -> decreased immune stimulus -> decreased amtibody -> increased susceptibility -> outbreak
- Later average age of exposure -> increased severity e.g.. polio, hep A, chicken pox, congenital rubella syndrome

40
Q

How does immunodeficiency affect infections?

A

Increase in frequency and severity

41
Q

What other diseases is immunodeficiency associated with?

A

Autoimmune diseases

Malignancy

42
Q

What age group are most people who are diagnosed with immunodeficiency?

A

> 50% >18

43
Q

What is an immunocompromised host?

A

State in which the immune system is unable to respond appropriately and effectively to infectious microorganisms

Qualitative or quantitative defect of one or more components of the immune system

44
Q

What are the key components of the innate immune system?

A

Innate barriers
Phagocytes
Complement

45
Q

What are the key components of the adaptive immune system?

A

B cells and antibodies

T cells

46
Q

How are immunodeficiencies recognised and diagnosed?

A

Infections suggesting underlying immune deficiency defined as “SPUR”:

  • S - severe
  • P - persistent
  • U - unusual
  • R - recurrent
47
Q

How are immunodeficiencies classified?

A

Primary - Intrinsic defect - Single-gene disorder/ polygenic/ polymorphism

Secondary - Underlying disease or condition affecting immune components - decreased production/ increased loss or catabolism

48
Q

How can primary immunodeficiencies be further classified?

A

B cell
T cell
Phagocytes
Complement

49
Q

What is the incidence rate of immunodeficiencies?

A

1:400 - 1:400000
Occur in the first month of life
80% patients <20 yrs
70% male

50
Q

What is the most common B cell immunodeficiency disease?

A

Common variable immunodeficiency - Inability of B cells to mature to plasma cells

51
Q

What is impaired B cell development known as?

A

Bruton’s disease (X-linked)

52
Q

What is the presentation of patients with primary antibody deficiencies?

A

Recurrent upper and lower respiratory bacterial infections -> bronchiectasis
GI complications including infections (Giardia)
Arthropathies (including Mycoplasma/Ureaplasma sp)
Increased incidence of autoimmune disease
Increased incidence of lymphoma and gastric carcinoma

53
Q

What is the management of a patient with primary antibody deficiencies?

A

Prompt/prophylactic antibiotics
Immunoglobulin replacement therapy
Management of respiratory function
Avoid unnecessary exposure to radiation

54
Q

What is the presentation of patients with primary phagocyte deficiencies?

A 
Prolonged and recurrent infections:
Skin and mucous membranes
Osteomyelitis
Deep abscesses 
Commonly staphylococcal (catalase +ve) 
Invasive Aspergillosis
Inflammatory problems (granuloma)
55
Q

What is the management of a patient with primary phagocyte deficiencies?

A

Prophylactic antibiotics/anti-fungal gents
Interferon-g (CGD)
Steroids (CGD)
Stem cell transplantation

56
Q

What is Di George syndrome?

A

Lack of thymus - defect in thymus embryogenesis and incomplete development => T cell deficiency

57
Q

What is severe combined immunodeficiency?

A

Absence of functional T-lymphocytes which results in a defective antibody response due to either direct involvement with B-lymphocytes or due to improper activation of the B cells due to non-functional T helper cells.
Most severe form of immunodeficiency. Multiple types depending on gene mutated

58
Q

What are the symptoms of DiGeorge syndrome?

A 
CATCH-22
Cardiac abnormalities
Abnormal facies
Thymic hypoplasia
Cleft Palate
Hypocalcaemia 
22 is the chromosome abnormalities
59
Q

What is the management of DiGeorge syndrome?

A 
Neonatal cardiac surgery
Supplement to correct hypocalcaemia
If <4 cellmicrolitre, prophylaxis with antibiotics
Bone marrow transplantation
Use only X-raddiated and CMV (-) blood
No live vaccines
60
Q

How does SCID present?

A 
Failure to thrive
Protracted diarrhoea
Hepato-splenomegaly
90% of SCID have low lymphocyte count
High susceptibility to fungal and viral infections
61
Q

What viral infections are common in patients with SCID?

A 
Pneumocystis pneumonia
Varicella-zoster virus
Herpes viruses
Cytomegaloviruse
Epstein Barr virus
62
Q

What is the management of a patient with SCID?

A 
Short term:
- no vaccines
- only irradiated CMV-blood products
- aggressive treatment of infections
- prevention of new infections - prophylactic antibiotics and anti-fungals IVIG
Long term:
- bone marrow / stem cell transplantation 
- gene therapy
63
Q

What does a deficiency in C1, 2 or 4 compliment components cause?

A

Immune-complex disease

64
Q

What does C3 complement component deficiency cause?

A

Recurrent bacterial infection

65
Q

What causes recurrent Neisserial infection?

A

C5, 6, 7, 8 or 9 compliment component deficiencies

66
Q

What might cause a secondary immune deficiency?

A 
Malnutrition
Infection
Liver disease
Lymphoproliferative diseases 
Drug-induced neutropenia
Splenectomy
67
Q

What factors might cause neutropenia?

A 
Drugs
Autoimmune
infections
Bone marrow infiltration with malignancy
Aplastic anaemia
Vitamin 12/folate/iron deficiency
Chemotherapy
Exposure to chemical agents
Radiotherapy
68
Q

What is the management of neutropenia?

A

Treat suspected neutropenic sepsis as an acute medical emergency and offer emeperic antibiotic therapy immediately
Assess patient’s risk of septic complications

69
Q

What is an asplenic patient more at risk of?

A

Increased susceptibility to encapsulated bacteria

OPSI (overwhelming post-splenectomy infection) => sepsis and meningitis

70
Q

What is the management of an asplenic patient?

A

Penicillin prophylaxis
Immunisation against encapsulated bacteria (at least 2 weeks after splenectomy if poss)
Patient information; Medic alert bracelet

71
Q

What are the immune functions of the spleen?

A

Blood borne pathogens
Antibody production - acute: IgM, long term: IgG
Splenic macrophages remove opsonized microbes and remove immune complexes

72
Q

What might cause increased loss or catabolism of immune components?

A

Protein-losing conditions - nephropathy, enteropathy

Burns

73
Q

How is the specific type of immunodeficiency recognised and diagnosed?

A 
Age
Sex
Site(s) and frequency of infection(s)
Type of organism(s)
Sensitivity and type of treatment
Family history
74
Q

What are the investigations carried out to diagnose an immunodeficiency?

A

Full blood count and differential
Exclusion of secondary immunodeficiency
Tests of humoral (antibody) immunity
Tests for cell mediated immunity - lymphocytes
Tests for phagocytotic cells - neutrophils
Tests for complement
Definitive tests - molecular testing and gene mutation

Semester 3 (19 decks)

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