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MCD Microbiology > Community acquired bacterial infections > Flashcards

Community acquired bacterial infections Flashcards

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Biology 101 flashcards
1
Q

Name some examples of cocci bacteria

A

Staphylococci, streptococci, sarcina and tetrad

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2
Q

Name some examples of bacilli bacteria?

A

Coccobacillus, bacillus, diplobacilli, palisades, streptobacili

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3
Q

Name the common virulence factors

A 
Secretion systems
Flagella
Pili
Capsule
Endospores - resistant to heat, cold, desiccation and chemical resistant 
Exotoxins
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4
Q

What are the different types of exotoxins?

A

Neurotoxins- Act on nerves or motor endplates to cause paralysis e.g. tetanus and botulinum toxin
Enterotoxins- GI tract to cause diarrhoea- inhibit NaCl resorption, activate NaCl secretion or kill intestinal epithelial cells- commune end result is osmotic pull of fluid into the intestine which causes diarrhoea
Pyrogenic exotoxins- stimulate release of cytokines and can cause rash, fever and toxic shock syndrome
Tissue invasive exotoxin
Miscellaneous exotoxin

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5
Q

How does infectious diarrhoea occur?

A

Bacteria colonise and bind to the GI tract, continuously releasing their enterotoxin locally. Diarrhoea will continue until bacteria are destroyed by the immune system or antibiotics

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6
Q

Give some examples of infectious diarrhoea diseases?

A

Vibro cholera
Escherichia coli
Campylobacter jejuni
Shigella dysenteriae

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7
Q

Describe the process of food poisoning?

A

Bacteria grow in food and release enterotoxin into the food. The enterotoxin is ingested resulting in diarrhoea and vomiting for less than 24 hours

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8
Q

Give some examples of food poisoning bacteria?

A

Staphylococcus aureus and bacillus cereus

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9
Q

What are endotoxins?

A

Lipid A part of LPS, component of gram negative bacterium

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10
Q

What is septic shock?

A

Sepsis that results in dangerous drops in blood pressure and organ dysfunction

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11
Q

What is septic shock also known as?

A

Endotoxin shock because endotoxin often triggers the immune response that results in sepsis and shock (but adverse effects in gram-positive bacteria or even fungi can trigger adverse immune response)

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12
Q

What is an outbreak?

A

A greater than normal or greater than expected number of individuals infected or diagnosed with a particular infection in a given period of time or a particular place or both

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13
Q

How can an outbreak be identified?

A

Surveillance systems provide an opportunity to identify outbreaks- report to a central system to identify the spread
Good and timely reporting systems are instrumental

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14
Q

What was the E coli outbreak in Germany 2011 caused by?

A

Entero-aggregative shiga-toxin producing e coli

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15
Q

What did the E.coli outbreak lead to?

A

Gastroenteritis and haemolytic-uremic syndrome

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16
Q

What was the e.coli outbreak spread by?

A

Consumption of sprouts

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17
Q

What is haemolytic-uremic syndrome?

A

Acute renal failure, haemolytic anaemia and thrombocytopenia

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18
Q

Who is HUS normally found in?

A

Children

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19
Q

What is the normal reservoir for HUS?

A

Cattle

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20
Q

How does infection occur of HUS in humans?

A

Inadvertent ingestion of decal matter and secondary through contact with infected humans- very rare in adults

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21
Q

What do you need to define an outbreak?

A

Cause, characteristics, scale, time-frame, source, illness, involvement of different strains, symptoms to look for etc

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22
Q

What can you do once you know the genome of the bacteria to detect the outbreak strain?

A

Do PCR in stool samples etc

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23
Q

What is the structure of shiga/vero toxin?

A

Subunit a (StxA) is non covalently associated with a pentamer of protein B (StxV)

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24
Q

What is the role of StxA?

A

Enzymatically active domain- it is an enzyme that cleaves the 28S ribosomal RNA in eukaryotic cells leads to inhibition of protein synthesis

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25
Q

What is the StxB pentamer responsible for?

A

Binding to host cell receptors

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26
Q

What are bacterial ribosomes a substrate for and what is the effect?

A

StxA and it will result in decreased proliferation of susceptible bacteria which might affect the commensal microflora in the gut

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27
Q

What are shiga toxins encoded on?

A

A bacteriophage (highly mobile genetic element which contributes to horizontal gene transfer

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28
Q

What caused the outbreak in Germany?

A

Horizontal gene transfer of shiga toxin from EHEC strain to EAEC strain of coli, which also has a virulence factor- aggregative adherence fimbriae (AAF) which is required for adhesion to to enterocytes in gut. It also stimulates a strong IL-8 response which allows biofilm formation and additional virulence factors.

29
Q

What are the different types of communicable disease in Europe?

A

Respiratory tract infections
Sexually transmitted infections, including HIV and blood-borne viruses
Food and waterborne diseases and zoonoses
Emerging and vector borne diseases
Vaccine preventable diseases
Antimicrobial resistance and healthcare associated infections

30
Q

Give examples of respiratory tract infections?

A

Influenza (human, avian and animal)
Legionnaire’s disease
Tuberculosis

31
Q

What type of bacteria is legionella pneumophila?

A

Gram-negative bacterium

32
Q

Where is legionella pneumophila?

A

Lives in amoeba in ponds, lakes, air conditioning units, whirlpools etc

33
Q

What is the infection route of legionella pneumophila?

A

Inhalation of contaminated aerosols

34
Q

What does L. pneumophila affect in humans?

A

It will infect and grow in alveolar macrophages

35
Q

What is the important virulence factor in l.pneumophila?

A

Type IV secretion system which allows secretion of effector proteins to cytoplasm of host cells which allows legionella to replicate in a legionella containing vacuole within the host cell

36
Q

What sort of bacteria are mycobacterium tuberculosis?

A

It groups with gram positive but are structurally very different as they have a cell wall with an extra lipid layer. This makes treatment more difficult

37
Q

What is the latent state of TB?

A

Evidence of infection by immunological tests but no clinical signs and symptoms of active disease

38
Q

What makes treatment of TB difficult?

A

There is often a mixture of active and latent so it is difficult to treat bacteria in different states

39
Q

What is the treatment success rate of TB (for 1st and then second infection)?

A

It is 78% and decreases to 53% for 2nd infection as well as further decreasing to 32% in multi drug resistant TB

40
Q

Give examples of sexually transmitted infections?

A 
Chlamydia trachomatis infection
Gonorrhoea
Hepatitis B
Hepatitis C
HIV/AIDS
Syphilis
41
Q

What type of bacteria is chlamydia trachomatis and what does this mean?

A

It is an obligate intracellular gram negative pathogen so can’t culture it outside host cell

42
Q

What is the most frequent STI in europe?

A

Chlamydia 350,000 cases/year

43
Q

How is the infection rate of chlamydia changing?

A

Increasing

44
Q

What percentage of the worlds blindness is chlamydia responsible for?

A

More than 3%

45
Q

What type of bacteria is neisseria gonorrhoeae?

A

Gram negative diplococcus

46
Q

How does neisseria gonorrhoeae establish infection?

A

It establishes infection in urogenital tract by interacting with non-ciliated epithelial cells

47
Q

What is the important virulence factor for gonorrhoea?

A

Pili

48
Q

Give some examples of food and waterborne diseases and zoonoses?

A 
Campylobacter sp
Salmonella sp
Bacillus anthracis
Vibro cholera
Listeria monocytogenes
49
Q

What is the most commonly reported GI infectious disease in the EU?

A

Campylobacteriosis (sporadic cases not outbreaks)

50
Q

What is the highest risk group of campylobacter?

A

Children aged 0-4 years

51
Q

What is infection of campylobacter most likely from?

A

Undercooked poultry

52
Q

What is the virulence factor involved in campylobacter?

A

Adhesion and invasion factors, flagella motility, type IV secretion system, toxin

53
Q

What is salmonella sp. caused by?

A

Undercooked poultry

54
Q

What is the most at risk group of salmonella infection?

A

Small children aged 0-4

55
Q

What is the important virulence factor involved in salmonella?

A

Type III secretion systems (encoded on pathogenicity islands= SPI)- two islands:
SPI1 is required for invasion
SPI2 is for intracellular accumulation

56
Q

How is bacillus anthraces usually transmitted?

A

It is very rare and usually transmission to humans from animals e.g. sheep and cattle
Outbreak in 2009 in UK- IV drug users

57
Q

How does bacillus anthraces cause infection?

A

Infectious particles endospores (high mortality if untreated)

58
Q

What virulence factors are involved in bacillus anthracis?

A

Toxin and capsule (encoded on plasmids)

59
Q

What is cholera?

A

Acute, severe diarrheal disease

60
Q

What can happen without prompt rehydration in cholera?

A

Death can occur within hours of onset of symptoms

61
Q

What is the important virulence factor in cholera?

A 
Type IV fimbria
Cholera toxin (carried on phages)
62
Q

What else does type IV fimbria (TCP phage) serve as apart from a colonisation factor?

A

A receptor for CTX phage encoding cholera toxin- Both bacteriophages can integrate into bacterial genome and form episomal replication intermediates and this is dependent on secretin

63
Q

What does the cholera toxin do?

A

Makes the cell produce cyclic AMP which activates transporters leading to efflux of chloride ions with water movement following

64
Q

What is the risk group for listeria monocytogenes?

A

Immunocompromised, elderly, pregnant and their fetus

65
Q

Why is listeria a big problem?

A

It can cross three tight barriers- intestinal, blood/brain and materno/fetal

66
Q

What has studying listeria allowed understanding of?

A

Actin-based cell mobility

67
Q

What emerging and vector borne diseases are there?

A

Plague (yersinia pestis, gram negative)
Q fever (coxiella burnetti, gram negative)
Smallpox (eradicated)

68
Q

What do vaccine preventable diseases include?

A 
Diphtheria
Invasive haemophillus influenza disease
Invasive meningococcal disease
Invasive pneumococcal disease
Pertussis
Tetanus

MCD Microbiology (6 decks)

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