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2021-22 Clinical microbiology > W1 Infection, normal flora, infectious agents > Flashcards

W1 Infection, normal flora, infectious agents Flashcards

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1
Q

True or False:
Most microorganisms in nature and pathogenic

A

False!
Few microorganisms in nature are pathogenic.

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2
Q

Name 4 main types of pathogenic microorganisms

A

(a) Saprophytes
(b) Commensals
(c) Opportunistic pathogens
(d) True pathogens

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3
Q

Give examples of commensals (normal flora)

A
  • Staphylococcus epidermidis
  • Candida albicans
  • Escherichia coli
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4
Q

Where on the body is staphylococcus epidermidis found?

A

Skin

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5
Q

Where on the body is Candida albicans found?

A

Upper respiratory tract

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6
Q

Where on the body is Escherichia coli found?

A

Large intestine

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7
Q

Give examples of opportunistic pathogens

A
  • Staphylococcus epidermidis (device related infections)
  • Candida albicans ( can cause oral thrush) overgrows when broad spectrum antibiotics are used (e.g. amoxicillin)
  • E.Coli (UTI)
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8
Q

Give examples of true pathogens

A
  • Staphylococcus aureus
  • Neisseria Gonorrhoeae
  • COVID-19
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9
Q

What is an infection?

A

A process of microbial invasion

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10
Q

Give examples of infections

A
  • Common cold
  • Tonsillitis
  • Urinary tract infection
  • Infected leg ulcer
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11
Q

What is an infectious disease?

Give examples

A

Communicable diseases. They are readily transmitted from person to person e.g. respiratory infections- TB, common cold, COIVD-19, gastrointestinal infections, Sexually transmitted infections (STI’s)

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12
Q

Infection in the 21st Century: Infectious diseases cause what percentage of all deaths?

A

Infectious diseases cause 25% of all deaths

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13
Q

Name some infections of concern in the developed world

A

-Pneumonia: HAP / CAP: UK deaths 30,000/PA

-Tuberculosis (10 million new cases) and drug-resistant TB (560,000 new cases) globally
UK 2018: 4,672

  • Gastrointestinal infections (norovirus, campylobacter; Clostridium difficile (2018:13,286)
  • Device-related infections (catheters, prosthetic joints)

-Healthcare associated infections (MRSA,
C. difficile, carbapenemase-producing Gram negative rods)

-Sexually transmitted infections (chlamydia, gonorrhoea, syphilis, herpes, genital warts, HIV)

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14
Q

What factors are facilitating the spread of infection in the 21st century?

A
  • Ease of travel; ‘shrinking world-easy to travel’
  • Medical interventions (ageing population; increased surgery)
  • Overuse of antibiotics (antibiotic resistance; HAI)
  • Contraceptive pill (STIs)
  • Social: (alcohol, drugs, MSM, social networks: internet chat, geosocial networking apps - Grindr +Blendr – linked with increase in STIs)
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15
Q

Infection in the 21st Century: Developing Nations

Name some infections of concern in the developing world

A

Asia and Sub-Saharan Africa

  • HIV: 70% the world’s HIV burden; 70% of all new HIV infections
  • AIDS: 80% of AIDS related deaths
  • Malaria: 90% of the global malarial burden
  • TB: 40% of all new cases of TB
  • Diarrhoeal disease (parasitic, bacterial, viral)
  • Ebola
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16
Q

What factors are influencing the spread of infection in the 21st century? (developing nations)

A
  • Poverty / overcrowding / malnutrition
  • Weakened resources, infection control procedures and medical interventions (treatment, drugs, vaccination)
  • Increased HIV incidence (secondary infections)
  • Climate change; flooding
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17
Q

How do we classify infectious agents in clinical practice?

A
  • Bacteria
  • Parasites (helminths and protozoa)
  • Fungi Fungi (moulds, yeasts)
  • Viruses (DNA, RNA)
  • Arthropods (direct / indirect causes of infection)
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18
Q

How are bacteria categorised in clinical practice?

A
  • True bacteria
  • Filamentous
  • Spirochaetes
  • Mycoplasmas
  • Ricketssiae and Chalmydiae
19
Q

How are true bacteria classified?

A
  • Gram stain reaction (positive, negative)
  • Shape (cocci, bacilli)
  • Growth requirements (O2, ANO2)
20
Q

Give some examples of Gram-positive cocci

A
  • Staphylococcus eg. S. aureus, MRSA, S.epidermidis
  • Streptococcus eg. S.pyogenes, S. pneumoniae,
21
Q

Give examples of Gram-positive Bacilli

A
  • Clostridium (anaerobic) eg. C. difficile
  • Bacillus (aerobic) eg. B. anthracis
22
Q

Give examples of gram negative cocci

A

Neisseria (N. gonorrhoeae)

23
Q

Give examples of gram negative aerobic bacilli

A
  • Enterobacteria eg. Escherichia coli
  • Pseudomonads eg. Pseudomonas aeruginosa
  • Parvobacteria (Small, Gram negative rods) eg. Haemophilus influenzae
  • Vibrios (curved/spiral) eg. Campylobacter jejuni
24
Q

Give an example of a gram negative anaerobic bacilli

A

Bacteroides sp

25
Q

Give an example of a filamentous bacteria

A

Myobacterium
e.g. Myobacterium tuberculosis (high GC content in DNA)

26
Q

Give an example of a spirochaete

A

Treponema
e.g. treponema pallidum

27
Q

Give an example of a mycoplasma

A

Mycoplasma pneumoniae (causes atypical pneumonia)

No cell wall- can’t use beta lactam antiotics against them

28
Q

Give an example of Ricketssia and Chlamydiae

A

Chlamydia and trachomatis (needs host cell to survive and growth)

29
Q

PARASITES
What are the main characteristics of protozoa?

A
  • Unicellular / Eukaryotic
  • May exist as trophozoites or cysts eg. Giardia intestinalis
30
Q

PARASITES
What are the main characteristics of helminths?

A

‘Worms’
-Multicellular / Eukaryotic eg. Ascaris lumbricoides (roundworm)

31
Q

Parasites may be subdivided into:

A

Gastrointestinal (eg. Ascaris, Giardia)
Blood / tissue (eg. Plasmodium sp)

32
Q

FUNGI
What are the main characteristics of moulds?

A
  • Branching filaments (hyphae)
  • Reproduce by forming spores
33
Q

Give an example of a mould

A

Aspergillus fumigatus

34
Q

FUNGI
What are the main characteristics of yeasts?

A
  • Ovoid / Spherical
  • Reproduce by budding
35
Q

Give an example of a fungi

A

Candida albicans

36
Q

What are viruses?

A
  • Obligate intracellular parasites
  • Strand of DNA or RNA encapsulated in a protein shell (capsid)
37
Q

Give examples of RNA viruses

A
  • Reoviruses (rotavirus)
  • Retroviruses (HIV)
38
Q

Give examples of DNA viruse

A
  • Herpesviruses (Herpes simplex)
  • Papovaviruses (Human papillomavirus)
39
Q

What are arthropods?

A

Arguably the largest most successful single group of animals in the animal kingdom eg. louse, ticks, mites

40
Q

How do arthropods cause disease directly?

A

By feeding on human blood/tissue eg. Phthirus pubis (crab louse: pubic lice, ‘crabs’)

41
Q

How do arthropods cause disease indirectly?

A

By transmission of viruses/parasites to humans eg. Mosquitoes (malaria)

42
Q

Why do we study infectious disease?

A
  • Infectious disease in 21st century is common in developed and developing countries and is associated with significant morbidity and mortality
  • Many factors facilitate the spread of infectious disease
  • Commensal bacteria are widespread over many parts of the body and help to keep infectious disease at bay; may act as ‘opportunistic’ pathogens and cause disease; considered as ‘friend and foe’
43
Q

Infectious agents can be conveniently categorised into 5 major groups:

A
  1. Bacteria
  2. Parasites
  3. Fungi
  4. Viruses
  5. Arthropods
44
Q

Give examples of sterile parts of the body

A

Blood, muscle tissue and bladder

2021-22 Clinical microbiology (10 decks)

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