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Preventing Infectious Diseases Flashcards

1
Q

Risk Factors for Infectious Disease - Developing Countries

A
  • Underweight
  • Unsafe sex
  • Unsafe water, sanitation and hygeine
  • Indoor smoke from solid fuels
  • Zinc deficiency
  • Vitamin A deficiency
  • Tobacco
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2
Q

Risk Factors for Infectious Disease - Developed Countries

A
  • Tobacco
  • Illicit drugs
  • Unsafe sex
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3
Q

Foodborne Illness

A
  • Caused by the consumption of food contaminated with organisms or their toxins. • •The ‘big five’ bacteria:
    • Salmonella
    • Campylobacter
    • E coli 0157
    • Listeria monocytogenes
    • Clostridium perfringens
  • Important because they cause a lot of cases of intestinal illness or because they cause severe disease, or both
  • Factors that may influence spread of infection from food chain to humans include:
    • Intensive farming
    • Global distribution
    • Mass production
    • New microbes
    • Antibiotic residues
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4
Q

Hospital Acquired Infections

A
  • Neither present or incubating when patient enters hospital but develop during hospital or are present/incuvating when discharged
  • Affects 8% of hospital admissions
  • Caused by:
    • Breaches in normal body defences:
      • Surgery
      • Invasive devices
    • Underlying illness increasing vulnerability
      • Impaired immune response
      • Diabetic ulcers
    • Exposure to micro-organisms
      • Endogenous human flora
      • Environmental contamination/colonisation
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5
Q

Hospital Acquired Infections - Mechanisms of Spread

A
  • Hands and contaminated equipment
    • MRSA and Group A Streptococcus
  • Faecal/oral spread and contaminated environment
    • Viral gastroenteritis and C.difficile
  • Airborne/droplet
    • Viral gastroenteritis and Group A Streptococcus
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6
Q

Hospital Acquired Infections - Sites

A
  • Urinary tract (23%)
    • Minor severity
    • Risk factors:
      • Urinary catheter use
    • Prevention:
      • Correct management of catheters
  • Lower respiratory tract (23%)
    • Severe
    • Risk factors:
      • Ventilation
      • Post-surgery
      • NG feeding
    • Prevention:
      • Physiotherapy
      • Tracheostomy care
      • NG care
  • Bloodstream
    • Severe
    • Risk factors:
      • Intravascular devices - ITU/renal/haematology
    • Prevention:
      • Correct management of lines
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7
Q

Hospital Acquired Infection - Prevention

A
  • Clean environment
  • Clean reusable equipment between use
  • Hand washing (staff and patient)
  • Source and protective isolation
  • Meticulous aseptic technique during invasive procedures
  • Meticulous care of invasive devices and prompt removal
  • Ward closure during outbreak
  • Antimicrobial stewardship
  • Surveillance
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8
Q

Hospital Acquired Infection - Surveillance

A
  • Mandatory:
    • MRSA
    • C. difficile
    • Glycopeptide resistant enterococci (GRE)
    • E.coli
    • Surgical Site infections
  • Voluntary:
    • Methicillin-sensitive Staphlococcus aureus (MSSA)
    • Pseudomonas/Acinetobacter/Stenotrophomonas
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9
Q

Antibiotic Prophlaxis - Surgical

A
  • Peri-operative antibiotics may be given to prevent Surgical Site Infection (SSI)
    • Responsible for up to 20% of HAI
    • Risk depend on type of surgery and patient:
      • Clean vs. dirty surgery
      • Proceedure complexity
      • Foreign material
      • Injury to wound tissues
      • Severity of illness
      • Host immunocompromise
    • Diagnosis based on clinical signs not lab results
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10
Q

Antibiotic Prophlaxis - Surgical - Grading

A
  • Clean:
    • Non-traumatic
    • No inflammation
    • No break in technique
    • No breach of respiratory, alimentary or genito-urinary tracts
      • No prophylaxis needed (unless metalwork or spinal surgery)
  • Clean-contaminated:
    • Non-traumatic
    • Break in technique or breach of respiratory, alimentary or genito-urinary tracts
    • No significant spillage
      • One dose of antibiotics
  • Contaminated:
    • Major break in technique
    • Gross spillage from a viscus that may contain non-purulent material
    • Dirty traumatic wounds
    • Faecal contamination
    • De-vitalised viscus
    • Pus encountered from any source during surgery
      • Antibiotics for 5-7 days
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11
Q

Antibiotic Prophlyaxis - Susceptible Populations

A
  • Infective endocarditis - NICE guidance does not recommend antibiotic prophylaxis solely to prevent IE in at-risk patients undergoing dental and non-dental proceedures
  • Prevention of invasive pneumococcal disease post-splenectomy
  • Decrease the incidence of urinary tract infections
  • Prevention of opportunistic infections post solid organ and bone marrow transplants
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12
Q

Antibiotic Prophylaxis - Eradicating Carriage

A
  • Aim is to prevent secondary cases in contacts of people with serious invasive diseases:
    • Meningococcal disease
    • H.influenzae type B
    • Tuberculosis
    • Group A Streptococcus
  • Contacts identified through contact tracing by CCDC/HPU
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13
Q

Antibiotic Prophylaxis - Pre/Peri/Post Exposure

A
  • Aim is prevent acquisition and development of an infection in relation to a defined exposure or period of exposure:
    • Influenza
    • HIV
    • Malaria
    • Hepatitis B
    • Perinatal vertical infections:
      • HIV
      • Beta-haemolytic Streptococcus B
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14
Q

Treatment As Prevention

A
  • Important in developing countries
  • Aim to decrease burden of disease and protect whole population:
    • Decreased spread
    • Decreased environmental contamination
  • Examples:
    • TB (respiratory droplet spread, 10% contacts of cases of open TB develop active disease)
    • Trachoma (worldwide major preventable cause of blindness caused by Chlamydia trachomatis)
    • Gut helminths eg. Ascaris (faeces/soil)
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15
Q

Vaccination

A
  • Vaccines induce active immunity and provide immunological memory
    • Enables the immune system to recognise and respond rapidly to exposure to natural infection at a later date ==> prevention or modification of disease course
  • Vaccines can be made from:
    • Attenuated live organisms
    • Inactivated (killed organisms)
    • Important antigens:
      • Inactivated toxoids
      • Surface proteins
      • Capsular polysaccharide
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16
Q

Vaccination - Routine Vaccinations: Dead vs Alive

A
  • Live:
    • Polio (oral)
    • MMR
    • BCG
    • Yellow fever
    • Varicella
  • Dead/inactivated/toxoid
    • Diptheria
    • Tetanus toxoid
    • Pertussis
    • IPV
    • Hib
    • MenC
    • HPV
    • Hepatitis B
    • Hepatitis A
    • Typhoid
    • Influenza
    • Pneumococcus
    • Rabies
17
Q

Vaccinations - Polysaccharide and Conjugate Vaccines

A
  • Polysaccharide vaccines are made of extracted and purified forms of the bacterial outer polysaccharide coat
    • These do not stimulate the immune system as broadly as protein antigens found in tetanus, diptheria or influenza vaccines
      • Protection is not long-lasting
      • Response in children and infants is poor
    • Scome polysaccharide vaccines eg. Hib and MenC have been enhanced by conjugation -
      • This involves attatchment of a carrier protein to a polysaccharide antigen ==> better immune reponse and efficacy including in young children
18
Q

Vaccination - Pneumococcal Vaccination in the UK

A
  • Pneumococcal Conjugate Vaccine (PCV)
    • Given to all children <2 years old as part of childhood routine immunisations
    • Original PCV contained polysaccharide from 7 common capsular types
      • At time of pre-license study covered 89% of invasive pneumococcal infections in the US
    • In 2010 DoH approved newer PCV which protects against 13 capsular types of pneumococcal bacteria
  • Pneumococcal Polysaccharide Vaccine (PPV)
    • Offered to:
      • All adults >65 years of age
      • All children and adults aged 2-64 years who are considered to be at risk
    • PPV provides protection against 23 types of pneumococcus - accounts for 96% of the types of pneumococcus responsible for serious infection in the UK
19
Q

Vaccinations For At Risk Groups

20
Q

Vaccinations - Successful Programmes

A
  • Successes:
    • Measles
      • Coverage fell to <80% in 2005
      • Measles re-established in 2007
      • Mostle attributable to unprotected 10-16 year olds missing vaccination in late 90’s and early 2000s - Due to MMR scare
    • Haemophilus influenzae b
    • Meningococcal C
  • Impact still unclear:
    • BCG
    • Typhoid
21
Q

Meningococcus B Vaccine - Technical Challenges

A
  • Meningococcus B responsible for 60% of meningococcal disease
  • Variable capsule and outer membrane
  • Able to mimic human structures
    • ==> Technically difficult to develop vaccine
22
Q

Meningococcus B Vaccine - Bexsero

A
  • Four component protein based vaccine
  • Routine programmes with and without catch up investigated
  • Incidence of invasive meningococcal disease falling
  • Immune response as part of UK schedule not assessed
  • Efficacy not established
  • Uncertain effects on carriage
  • Not cost-effective to routinely vaccinate

Microbiology (10 decks)

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