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immunology and microbiology > Infectious diseases and the diversity of bacterial pathogens L8 > Flashcards

Infectious diseases and the diversity of bacterial pathogens L8 Flashcards

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Biology 101 flashcards
1
Q

how do pathogenic microbes cause disease

A

Pathogenic microbes cause infection by gaining a foothold in a particular niche

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2
Q

define
1. colonisation
2. pathogenicity
3. virulence

A
  1. growth of a microbe after gaining access to host tissue
  2. ability of a pathogen to inflict host damage
  3. the degree of pathogenicity of an infecting pathogen
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3
Q

what are the mechanisms of microbial pathogenesis

A

person is EXPOSED, and microbe ADHERSE and INVADES. microbe then COLONISES and GROWS (producing virulence factors)
results in TOXCITY or further INVASIVNESS resulting in TISSUE DAMAGE and DISEASE

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4
Q

what are 3 features of infections

A
  1. Infections can be invasive but this is not exclusive (e.g. Salmonella and E. coli gut infection)
  2. Infections can be symptomatic or asymptomatic
  3. Infections can be highly acute or chronic causing long term complications
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5
Q

give 4 types of infections

A
  1. respiratory
  2. gastroenteritis (gut)
  3. UTI and bloodstream infections
  4. skin infections
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6
Q

describe microbiome of respiratory tract
and give two pathogens that can result in infection

A

Upper respiratory tract has an abundant microbiome (often asymptomatic carriage due to colonisation resistance)
Lower respiratory tract typically devoid of microbes
1. Mycobacterium tuberculosis
2. Legionella pneumophila

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7
Q

describe mycobacterium tuberculosis

A

Transmission risk due to respiratory expulsion (>40,000 aerosol droplets per sneeze; low infectious dose)
Survives within immune cells- microbacteria can survive in macrophages by stopping acidficiation, kill macrophage and use cell to replicate
Drug resistance rising,
Multiple mechanisms such as cell wall structure and efflux (getting something from inside cell to outside) - resistance

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8
Q

describe Legionella pneumophila

A

Grows in stagnant water
Can cause pneumonia, leading to high mortality (elderly and immunocompromised)
Survives inside immune cells by generating a protective vacuole
Amino acid auxotroph - promotes proteasomal degradation to gain nutrients
Use macrophage to produce amino acids

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9
Q

what are the causes of gut infections and give the two types the infection can be

A

Bacterial: usually ingestion, faecal-oral, contamination
Viral: winter vomiting bugs
Parasitic: less frequent, water-borne

Acute – rapid content ejection, typically self limiting after 48 hours
Chronic – long lasting illness

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10
Q

give 4 common pathogens of the gut

A
  1. E.coli
  2. intestinal pathogenic E.coli
  3. Vibrio cholerae
  4. Helicobacter pylori
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11
Q

describe E.coli

A
  • gram negative
  • rod bacterium
  • 2 pathotypes
    Intestinal pathogenic E. coli (InPEC)

Extraintestinal pathogenic E. coli (ExPEC)

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12
Q

give examples of InPEC

A

Enterohaemorrhagic E. coli (EHEC)*
Enteropathogenic E. coli (EPEC)
Enteroaggregative E. coli (EAEC)
Enteroinvasive E. coli (EIEC)
Enterotoxigenic E. coli (ETEC)
Diffusely adherant E. coli (DAEC)

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13
Q

give examples of ExPEC

A

Uropathogenic E. coli (UPEC)
Neonatal meningitis E. coli (NMEC)

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14
Q

describe Enterohaemorrhagic E. coli
InPEC

A

O157:H7 is the most common serotype EHEC
replicates in beef or leafy green reservoir
Encodes a Shiga Toxin – causes HUS, massive health and economical burden
constantly evolving to form different strains
- O104:H4 outbreak

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15
Q

describe Vibrio cholerae

A
  • gram negative motile
  • associated with aquatic reservoirs
  • causes constant activation of adenylate cyclase by B subunit resulting in Loss of ions into ECF causing large fluid loss
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16
Q

describe Helicobacter pylori

A
  • gram negative
  • mainly asymptomatic but can cause stomach pain
  • causes gastric and peptic ulcers in stomach
17
Q

what are UTIs caused by

A

wide range of pathogens from the gut- asymptomatic in the gut
they may get out of gut and into bladder
causes inflam response and neutrophil infiltration
form reservoirs, biofilms or subcellular communities
UTIs can be recurrent and commonly drug resistant
can enter blood stream causing sepsis

18
Q

describe skin infections

A

normally caused by opportunistic pathogens
- An organism that causes disease in the absence of normal host resistance
- Can cause skin lesions and inflammation but also disseminate to infection of throat, middle ear, blood, lungs
- Often caused by Gram positive cocci such as Staphylococcus and Streptococcus sp.

19
Q

what are the two types of immunity

A

innate and adaptive

20
Q

what is inflamation

A

A nonspecific reaction driven by neutrophil accumulation

21
Q

give signs of acute infection

A
  1. rubor: redness
  2. calor: heat
  3. tumor/ swelling
  4. dalor: pain
  5. change in function: reduced motility
22
Q

give methods of adaptive immunity

A

1.specifc and memory
2. humoral
3. cellular
4. ADCC: Antibody dependent Cell mediated cytotoxicity

23
Q

describe immune response to S. enterica

A

0: Ingest contaminated food
15 min: Invasion of epithelial cells
1 h: Neutrophils appear, increased vascular permeability
3 h: Neutrophil induced tissue damage and inflammatory induced fluid accumulation
8 h: Massive effusion of Neutrophils and fluid in intestinal lumen
24 - 48 h: Evident tissue damage, diarrhoea, more fluid accumulation

24
Q

define
1.Bacteraemia
2. sepsis
3. systematic shock

A
  1. the presence of bacteria in the bloodstream
    - Leads to mass organ dissemination
  2. extreme, system-wide inflammatory response to blood poisoning
  3. systemic drop in blood pressure leading to mass organ failure
25
Q

give 3 examples of pathogenic reservoirs

A

Environmental = V. cholerae
Zoonotic = EHEC
Human = UPEC

26
Q

describe the human reservoir

A

UPEC reside harmlessly in the gut
They can get in bladder and evolve to be pathogenic in bladder
cause UTI

27
Q

Why do we need to identify the cause of an infection in the clinic

A

To provide accurate information about the presence or absence of microorganisms (bacteria) in a specimen that may be involved in a patient’s disease process

28
Q

What is the pathway to diagnosis

A
  1. doctors- treatments
  2. disease surveillance centres- outbreak monitoring, evaluate disease control, data processing
  3. lab- further investigation
29
Q

describe patient to diagnosis pathway

A

specimen taken
- antibody or other essays
rapid testing on sample or it is cultured and identified using sterology

30
Q

give 4 types of diagnostic media

A
  1. general purpose
    - non-selective established growth
  2. enrichment
    - select for certain species
  3. selective
    - grows only certain bacteria
  4. differential
    - selects between two bacteria species
31
Q

describe general purpose media

A

uses LB agar generally (Luria-Bertani) contains Yeast extract, salts, water and agar

Grows both fastidious (fussy/ with needs) and non-fastidious bacteria (and yeast/fungi)

Often a starting point to look for unexpected organisms

32
Q

describe enrichment media

A

Dependent on the symptoms and sample site

For fastidious bacteria, often supplement media with sheep’s blood (blood agar)

In a mixed sample this allows the causative organism to grow faster

33
Q

describe selective media

A

Mixed bacterial population sample taken
- put on blood based agar containing antimicrobials
Incubated at 42°C in microaerobic (low O2) conditions
- Inhibits growth of most enteric bacteria and Allows growth of Campylobacter
Uses not only media but growth conditions as selection
-Once isolated can use other serological tests or May use antibiotic selection

34
Q

describe differential media

A

General purpose media with chromogenic substrate additives
Tests for the presence/absence of enzymes = diagnosis
E.coli has B galactosidase- goes pink if present on agar
E.facalis has B glucosidase which goes blue on agar
p. mirabillis has niether so stays colourless on agar

immunology and microbiology (12 decks)

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