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Clinical Pathology > Theme 1: Lecture 1- Bacterial pathogens > Flashcards

Theme 1: Lecture 1- Bacterial pathogens Flashcards

1
Q

Which bacteria have thicker walls - gram +ve or -ve?

A

+ve

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2
Q

What colour do gram +ve cells turn following a gram stain and why?

A

blue/ purple

thicker wall allows colour to be retained

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3
Q

What colour do gram -ve cells turn following a gram stain and why?

A

red/pink

thin outer membrane does not retain the blue colouring

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4
Q

What factors allow certain bacteria to cause infections?

A
  1. Host factors - devices, immune system
  2. Opportunity - exposure, normal flora
  3. Bacterial factors - virulence, resistance, environmental survival
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5
Q

Why is E.coli the most common cause of UTIs?

A
  • able to adhere to uroepithelial cells/ urinary catheter materials
  • triggers host inflammatory response
  • able to develop resistance to antibiotics
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6
Q

How would S.aureus cause skin infections?

A
  • nasal carriage in up to 50% of people
  • able to adhere to damaged skin
  • produces exoenzymes and toxins that can damage tissues and provoke host response e.g pus formation
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7
Q

Is staphylococcus aureus gram +ve or -ve?

A

+ve

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8
Q

What infections can S.aureus cause?

A
  1. skin/soft tissue infections - commonest
  2. more severe infections - bacteraemia, septicaemia
  3. osteomyelitis/ septic arthritis
  4. rarely- endocarditis, pneumonia, UTI and meningitis
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9
Q

What are opportunistic pathogens?

A

microorganisms that do not usually infect healthy hosts but produce infections in hospitals, to immunosuppressed persons or those patients presenting underlying diseases

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10
Q

What is staphylococcus epidermis?

A
  • gram +ve
  • opportunistic pathogen
  • most people carry on skin
  • causes infection in association with ‘foreign bodies’ e.g catheters, prosthetics
  • adheres to plastics/metals using glycocalyx (‘slime’)
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11
Q

What is the commonest cause of bacterial sore throat?

A

streptococcus pyogenes

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12
Q

What is another word for streptococcus progenies and what conditions can it cause

A
  • group A strep

- scarlet fever, necrotising fasciitis, other SSTIs, pneumonia, puerperal sepsis, glomerulonephritis

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13
Q

what is puerperal sepsis?

A

infections in lower reproductive tract after women has given birth

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14
Q

Which bacteria is responsible for causing ‘strawberry tougue’ presentation in scarlet fever?

A

streptococcus pyogenes

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15
Q

How can you tell apart staph infections from strep infections under a microscope?

A 
"staphylo" = 'bunch of grapes'
"strepto" = 'chain'
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16
Q

What is the commonest cause of bacterial pneumonia and bacterial meningitis?

A

streptococcus pneumonia

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17
Q

What is the commonest cause of bacterial meningitis and sepsis in neonates?

A

streptococcus agalactiae a.k.a ‘group B strep’

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18
Q

Which gram +ve species of pus-forming streptococci is associated with abscesses? (dental, lung, liver, brain etc)

A

streptococcus milleri complex

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19
Q

What is viridans streptococci?

A
  • gram +ve
  • collective name for number of α-haemolytic streptococci that inhabit the upper respiratory tract e.g S.oralis, S.mitis
  • classic caușe of sub-acute bacterial endocarditis
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20
Q

What condition is S.mitis associated with?

A

rotting teeth/dental care

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21
Q

What is streptococcus gallolyticus? a.k.a streptococcus bovis

A
  • a type of α- haemolytic streptococcus that forms part of bowel flora
  • bacteraemia with this organism can be associated with colonic malignancies
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22
Q

What is zoonosis?

A

diseases that can be passed from animals to humans

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23
Q

What is listeria monocytogenes?

A
  • gram +ve bacillus

- rare but significant cause of sepsis and meningitis in pregnancy, neonates and immunosuppressed patients

24
Q

Which gram +ve bacteria is associated with consuming cheese made from unpasteurised milk and other foodstuffs?

A

listeria monocytogenes

25
Q

Which gram +ve bacteria is a classic cause of diphtheria?

A

corynebacterium species - cornyebacterium diptherisae

26
Q

are corynebacterium species gram +ve or -ve? what shape are they?

A

gram +ve bacilli

27
Q

What is propionibacterium acnes?

A
  • gram +ve bacillus
  • cutibacterium acnes
  • associated with acne
28
Q

What are enterobacteriaceae?

A

collective term for species of gram -ve bacilli found in bowel flora
includes E.coli, klebsiella pneumonia, enterobacter cloacae

29
Q

What gram -ve bacteria is the commonest cause of UTI and bacteraemia?

A

E.Coli

30
Q

What is a nosocomial infection?

A

hospital acquired infection

31
Q

What is the most common strain of E.coli and what is it associated with?

A

O157

  • associated with severe diarrhoea and haemolytic uraemia syndrome
  • associated with farm work and unpasteurised dairy products
32
Q

What is pseudomonas aeruginosa?

A
  • multi resistant gram -ve bacillus
  • opportunistic pathogen
  • can cause respiratory infections, UTI, SST’s in vulnerable patients
33
Q

Which gram -ve bacterial infection often produces a characteristic green pigment?

A

pseudomonas aeruginosa

34
Q

what is neisseria meningitidis?

A

gram -ve diplococcus

-causes meningococcal sepsis and/or meningitis

35
Q

What is the classic presentation of neisseria meningitidis?

A

purpuric non-blanching rash

when you press against the rash, the rash lesions don’t disappear

36
Q

What bacteria causes gonorrhoea?

A

neisseria gonorrhoea

-gram -ve diplococcus

37
Q

What condition is seen in neonates infected with neisseria gonorrhoea?

A

ophthalmia neonatorum

38
Q

What is haemophilus influenzae and what infections can it cause?

A
  • gram -ve bacillus
  • forms part of normal respiratory tract flora
  • can cause respiratory tract infections e.g pneumonia, COPD
  • capsulated types e.g type b - associated with meningitis and epiglottis
39
Q

What are anaerobes?

A

organisms that grow in the absence of oxygen

40
Q

What are clostridium species?

A

anaerobes / often spore-forming (spore forming allows them to survive better in environments, especially hospital environments)

41
Q

What is C.difficile infection?

A

antibiotic associated diarrhoea/colitis

-anaerobe

42
Q

Which anaerobe is the classic cause of gas gangrene?

A

C.perfringens

43
Q

Which anaerobe is the cause of tetanus?

A

C.tetani

44
Q

Which anaerobe is the cause of botulism?

A

C.botulinum

45
Q

What is another word for mycobacterium species and how do they react using conventional gram staining?

A
  • acid fast bacilli (AFBs)

- do not stain using conventional gram staining

46
Q

What is the cause of TB?

A

Mycobacterium tuberculosso

47
Q

Give 4 bacteria that do not have a conventional cell wall

A
  • chlamydia species
  • C.trachomatis
  • mycoplasma species
  • M.pneumoniae
48
Q

What bacteria is the commonest cause of STI?

A

C.Trachomatis

49
Q

Which bacteria is the commonest cause of respiratory tract infection?

A

M.pneumoniae

50
Q

Which spirochetes causes syphillis?

A

treponema pallidum

51
Q

What infections, other than syphilis, can spirochetes cause?

A
  • leptospirosis - associated to rats and sewage work

- Lyme disease - tick bites

52
Q

What is the commonest cause of skin infection?

A

staphylococcus aureus

53
Q

Which bacteria is the most common ST?

A

Chlamydia trachoma’s

54
Q

Name the 6 types of bacteria that can cause meningitis?

A
  1. Neisseria meningitidis
  2. Streptococcus pneumoniae
  3. Listeria monoctogenes
  4. Streptococcus agalactiae
  5. Haemophilus influenzae
  6. Staphylococcus aureus
55
Q

What is the leading cause of preventable blindness in developing countries?

A

chalmydia trochomatis

Clinical Pathology (57 decks)

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