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Principles of Disease > Infection > Flashcards

Infection Flashcards

1
Q

List the 5 categories of micro-organisms that cause infection.

A

Bacteria, virus, fungi, parasites, prions

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2
Q

List 4 sterile sites.

A

Blood, CSF, lung, bladder

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3
Q

List 4 non-sterile sites

A

skin, nasopharynx, urethra, gut

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4
Q

list 4 methods for collection of bacteria

A

mid-stream urine, sputum, throat swab, wound swab, faeces, blood culture, CSF

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5
Q

Describe tests used for diagnosis of bacterial infections.

A

gram staining and microscopy, culture (non-selective or selective)

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6
Q

Name a type of non-selective media.

A

Blood agar (show yellow staph aureus) and chocolate agar (i.e enriched medias)

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7
Q

Name a type of selective media.

A

MacConkey’s (grow gram negative and inhibit gram positive)

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8
Q

Name a sensitive test for the diagnosis of bacterial infection.

A

Culture (microscopy is not sensitive)

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9
Q

What is ZN stain/auramine used for?

A

Mycobacteria

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10
Q

What are the 4 main methods used to identify a virus?

A
  1. Molecular methods (e.g real-time PCR)
  2. Antigen detection
  3. Serology
  4. Electron microscopy (rarely used now)
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11
Q

What are the diagnostic principles in parasitology?

A
  1. Microscopy (parasite, cysts or ova in faeces or blood films for malaria)
  2. Serology sometimes useful e.g when parasite in deep tissue
  3. Culture rarely possible
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12
Q

What colour is a gram positive stain?

A

Purple

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13
Q

What colour is a gram negative stain?

A

Pink

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14
Q

What shape are cocci?

A

Spherical

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15
Q

Which bacterial cell wall contains more peptidoglycan?

A

Gram positive bacteria

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16
Q

Which bacterial cell wall contains lipopolysaccharides?

A

Gram negative bacteria

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17
Q

What is the function of penicillin binding proteins?

A

Essential for cell wall synthesis by forming cross-links and also illicit a strong immune response.

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18
Q

How many chromosomes does a typical bacterial cell have?

A

One single chromosome (no nucleus)

Plasmid = extra chromosomal entities, involved in gene transfer (conjugation).

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19
Q

Describe the capsule.

A

A virulence factor which helps bacteria to survive the host environment by preventing phagocytosis and desiccation.

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20
Q

What is the function of flagella and describe the 4 different types?

A

Motility of bacteria.

Monotrichous, Amphitrichous, Lophotricous, Peritrichous

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21
Q

Describe a bacteriophage.

A

Virus that infects and replicates within a bacterium.

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22
Q

When are spores formed?

A

When no nutrients are available and adverse environmental conditions exist (ensuring survival of bacterium through periods of stress)

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23
Q

What is the genus and species of Staphylococcus aureus?

A 
Staphylococcus = genus
Aureus = species
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24
Q

Describe how bacteria replicate and create genetic variation.

A

Binary fission (asexual reproduction) - transformation, transduction and conjugation. Produces identical progeny.

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25
Q

Name the three main groups of parasites.

A
  1. Protozoa
  2. Helminths
  3. Arthropods
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26
Q

Give an example of a protozoa.

A

Malaria (human and arthropod phases)

- mosquito - sporozoite - liver to mature - merozite - invade RBC - take up by mosquito

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27
Q

Give two extra examples of protozoa.

A
  1. Amoebae ( amoebic dysentery)

2. Flagellates

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28
Q

Name the three main types of helminths and provide an example of each.

A
  1. Nermatodes (round worms) e.g Ascaris Lumbricoides
  2. Cestodes (tapeworms) e.g Echinococcus
  3. Termatodes (flat worms) e.g schistosomiasis
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29
Q

Give examples of Arthropods

A
  1. Lice
  2. Ticks
  3. Mice
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30
Q

Describe the common diseases caused by enteric parasites.

A

Helminth infections (Ascaris Lumbricoides, Echinococcus, Schistosomiasis)

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31
Q

Describe the common blood-borne/vector-borne parasites.

A

Protozoa infections (Malaria, Chagas, Leishmanaiasis, Toxoplasmosis, Trypanosomiasis)

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32
Q

Define parasite.

A

An organism that lives within another organism and gets food at the expense of the host. Simple organisms however, more complex than bacteria.

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33
Q

Explain the structure of fungi.

A
  1. Lacks chlorophyl
  2. Forms spores
  3. Cell wall contains polysaccharides (chitin or glycan)
  4. Membrane contains ergosterol
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34
Q

Describe the 3 major types of fungi.

A
  1. Moulds - Zygomycetes e.g Aspergillus
  2. Yeasts - Astromycetes e.g Candida
  3. Mushrooms - Basidomycetes e.g Cryptococcus
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35
Q

Name three fatal systemic diseases caused by fungi acting as opportunistic pathogens.

A
  1. Candida (infect deep organs e.g after surgery or burns)
  2. Aspergillus (infect deep organs and strongly angioinvasive e.g after chemo)
  3. Cryptococcosis (pulmonary cryptococcosis or meningitis)
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36
Q

Give examples of dermatophytic fungal infections (non-fatal)

A

E.g by microsporum, tricophytob causing athletes foot, thrush, pityriasis versicolour

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37
Q

Describe host factors that contribute to pathogenicity of fungal infections.

A
  1. Warm and moist micro-environments.
  2. Broad-spectrum antibacterial agents
  3. Immunosuppression by iatrogenic causes, disease processes OR a combination of both.
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38
Q

Describe the diagnostic methods for detecting fungi.

A
  1. Direct detection (histopathology, high-res CT)
  2. Direct smear
  3. Growth on selective media
  4. Serology
  5. Fungal antigen detection
  6. PCR
  7. Culture for normal sterile sites
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39
Q

What is the route of administration for anti-fungal drugs?

A

IV, topical or oral (static or cidal)

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40
Q

What is the function of Polyenes?

A

Anti-fungals - target membrane

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41
Q

Give two example of a polyenes.

A

Amphotericin B and Nystatin

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42
Q

What is the function of Azoles?

A

Anti-fungal - targets sterols

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43
Q

Give an example of an azalea.

A

fluconazole, clotrimazole

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44
Q

What is the function of Echinocandins?

A

Anti-fungal - targets cell wall e.g anidulafungin

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45
Q

Name the 3 main anti-fungal agents.

A

Polyenes, Azoles, Echinocandins

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46
Q

What is the function of Flucytosine?

A

Anti-fungal - targets DNA synthesis (used in combination with one of the three main anti-fungals)

47
Q

How are viruses classified?

A

According to: vision shape, presence/absence of envelope, genome structure, mode of replication

48
Q

Describe the characterisation of viruses.

A

Small, non-cellular, icosahedral, obligate intracellular pathogens, tissue tropism

49
Q

List 5 of the main viruses.

A
  1. Hepatitis B and C - chronic infection, hepatocellular carcinoma, blood-borne, sexual or vertical transmission.
  2. HIV - chronic infection, blood-borne, sexual or vertical transmission, causes lymphadenopathy
  3. Measles - long-term immunity, airborne, respiratory conditions
  4. HPV - transformation , cervical, anal and oesophageal cancers.
  5. Herpes simplex - viral latency, oncogenic potential e.g Herpes simplex 8 causes Kaposi’s sarcoma, close-contact transmission.
50
Q

What does a virus use to reproduce?

A

Virion associated polymerase

51
Q

Describe the 4 steps of virus replication.

A
  1. Entry
  2. Replication
  3. Latency
  4. Shedding
52
Q

What can cause recombination and generation of a new strain?

A

Transmission of novel virus to humans or co-infection of humans and animal/bird strains in one organsim.

53
Q

What is the pro for having a virus that only replicates in humans?

A

Easier to eradicate

54
Q

Describe the 4 consequences of viral infection.

A

Clearance, Chronic Infection, latent infection, transformation

55
Q

Explain viral latency.

A

Following primary infection, some viruses lie dormant and full viral genome retained in host with expression restricted. Reactivation may occur (risk in immunocompromised)

56
Q

Describe how virus have oncogenic potential.

A
  1. Increase cell proliferation
  2. Prevent apoptosis
  3. ROS mediated damage
57
Q

What cancer can EBV cause?

A

Burkitt’s lymphoma

58
Q

What cancer can Herpes 8 cause?

A

Kaposi’s sarcoma

59
Q

What cancer can HPV cause?

A

Cervical cancer

60
Q

What cancer can Hep B and C cause?

A

Hepatocellular carcinoma

61
Q

How do anti-virals function?

A

Virtuistic and not virucidal (stop viral replication)

62
Q

What are the indications for anti-virals?

A

Prophylaxis, pre-emptive therapy, overt disease, suppressive therapy

63
Q

How do you prevent viral infections?

A

immunisation, anti-natal screening, blood/tissue/organ screening, infection prevention and control procedures, prophylactic treatment post-exposure.

64
Q

Define pathogen.

A

An organism which CAUSES disease.

65
Q

Define commensal.

A

An organism which is part of the NORMAL FLORA.

66
Q

Describe features of viral pathogenesis.

A

Cell destruction e.g death of CD4 cells by HIV, virus-induced changes to cellular gene expression

67
Q

List the cells involved in the innate immune system.

A

Natural killer cells, macrophages and polymorphs (eosinophil, neutrophil, basophil)

68
Q

List the cells involved in acquired immunity.

A

Humoral (antibodies - mostly bacterial infections) or cell mediated (T cells - mostly viral infections), B lymphocytes differentiate to plasma cells.

69
Q

Define colonisation.

A

Bacteria grow on body sites without causing infection.

70
Q

Define latent.

A

The ability of pathogenic virus to lie dormant.

71
Q

Define asymptomatic disease.

A

Carrier of disease infection, no symptoms. Also known as ‘sub-clinical infection’.

72
Q

Define the features of clinical infection.

A

Inflammation, pain, pyrexia, tachycardia, riggers, high WBC count, high CRP.

73
Q

Define pathogenicity.

A

The CAPACITY of an organism to cause infection.

74
Q

Define infectivity.

A

Ability to become established.

75
Q

Define virulence.

A

Ability to cause harmful effects once established.

76
Q

Describe exotoxins and give an example.

A

Released extracellularly by micro-organisms e.g tetanus

77
Q

Describe enterotoxins and give an example.

A

Exotoxin which act on GI tract e.g cholera.

78
Q

Describe endotoxin.

A

Part of gram negative cell wall - lipopolysaccharide e.g Neisseria meningitides.

79
Q

Describe the sites of viral entry.

A

Skin, conjunctiva, respiratory tract, urogenital tract, alimentary tract, capillary, arthropod.

80
Q

Describe features of acute inflammation.

A

Localised to specific site, development of viraemia with widespread infection of tissue e.g influenza A, enterovirus.

81
Q

Define antigenic drift.

A

Minor changes over time to generate antigenic variants.

82
Q

Define antigenic shift.

A

Abrupt major changes, non-human hosts play a key role.

83
Q

Name the two main types of gram positive cocci and describe shape.

A

Staphylococci (clusters) & Streptococci (chains)

84
Q

Name the gram positive, anaerobic, spore-forming bacilli.

A

Clostridium species

85
Q

What test is used to distinguish between staphylococci?

A

Coagulase test (positive = staph aureus, negative = staph epidermis)

86
Q

What test is used to distinguish between streptococci?

A

Haemolysis (alpha/partial = strep pneumonia, GREEN and beta/complete = step progenies)

87
Q

Name two gram positive bacteria used in biological warfare.

A

Clostridium botulinum and bacillus anthrax.

88
Q

Name a gram negative cocci.

A

N.gonorrhoea and N.meningitidis

89
Q

Name the gram negative cocco-bacilli.

A

Haemophilus influenza.

90
Q

Name a curved gram negative bacilli

A

Campylobacter, vibrio and helicobacter species.

91
Q

What distinguishes gram negative aerobic bacilli?

A

Lactose fermenters (E.coli) or non-lactose fermenters (pseudomonas and salmonella spp)

92
Q

Name a gram negative anaerobic bacilli.

A

Bacteriodes (part of normal colonic flora, causes intra-abdominal abscess which needs draining)

93
Q

Give two examples of an acid and alcohol fast bacilli.

A

Mycobacterium Tuberculosis and Mycobacterium Leprae

94
Q

Give an example of a spirochaetes.

A

Treponema (syphillis), borrelia and leptospirosis.

95
Q

Give an example of miscellaneous.

A

Chlamydia

96
Q

Describe the principles of active immunisation.

A

Natural (exposure/infection) and artificial (vaccine - antigen stimulates response, with memory and specificity)

97
Q

Describe the principles of passive immunisation.

A

Natural (using neonatal Fc receptor) and artificial (snake/spider bites etc, hypogammaglobulinaemia infusion of gamma globulins to decrease infection, specificity but no memory)

98
Q

Name the three types of vaccines available.

A
  1. Conventional (killed whole e.g polio or attenuated e.g BCG)
  2. Subunit (purified Ag e.g HPV)
  3. Toxoid (modified toxin e.g Tetanus)
99
Q

Define vaccination.

A

The administration of antigenic material to stimulate an individual’s immune response to develop adaptive immunity to a pathogen.

100
Q

Describe temporary contra-indications to vaccine.

A

Febrile illness and pregnancy

101
Q

Describe permanent contra-indications to vaccine.

A

Allergy and immunocompromised

102
Q

Describe herd immunity.

A

Decreased risk to unvaccinated individuals due to vaccination schedules where the majority of people are vaccinated and less likely to carry the infection.

103
Q

At what age does the childhood vaccination schedule begin?

A

2 months (DTP, polio, haemophilia influenza B, strep pneumonia and rotavirus)

104
Q

What are the non-routine vaccinations at birth?

A

BCG and Hep B.

105
Q

List 5 vaccines that may need to be given to travellers.

A

Hep A, typhoid cholera, yellow fever, Japanese encephalitis, rabies

106
Q

What can an ELISA be used for?

A

Measure antigen or antibody in serum.

107
Q

What type of organisms are resistant to phagocytosis?

A

Capsulated organisms e.g pneumococcus.

108
Q

Name an organism which is resistant to chlorination.

A

Cryptosporidium parvum (filtration needs to be carried out).

109
Q

What are the outcomes of colonisation and clinical infection determined by?

A

Host immune system and virulence factors.

110
Q

Does the differing ribosomes of mammalian and bacterial cells allow selective toxicity?

A

Yes.

111
Q

Do third generation cephalosporins (eg, ceftazidime) have better anti-staphylococcal activity than the earlier cephalosporins?

A

No. First generation do.

112
Q

Does piperacillin have an extended spectrum and active against Pseudomonas species?

A

Yes

113
Q

Do bacterial exotoxins act as virulence factors?

A

Yes

114
Q

What are microglial cells?

A

Specialised macrophages occurring in the brain.

Principles of Disease (9 decks)

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