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Principles of dizzees > Classification of pathogenic bacteria > Flashcards

Classification of pathogenic bacteria Flashcards

1
Q

What are the 4 types of pathogens we are concerned about?

A

Bacteria
Viruses
Parasites
Fungi

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2
Q

Describe the difference in the peptidoglycan layer in a Gram positive, and gram negative bacterial cell.

A

Positive - thick peptidoglycan layer

Negative - thin

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3
Q

What is another name for peptidoglycan?

A

Murein

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4
Q

What enzyme is present in the cytoplasmic membrane of all bacterial cells?

A

Cell wall synthesising enzymes

penicillin binding proteins

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5
Q

What 2 molecules are projected from the surface of gram positive bacteria?

A

Cell wall - teichoic acid

Membrane - lipoteichoic acid

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6
Q

Aside from the two teichoic acid types, what is found on the surface of gram negative bacteria?

A

Cell surface proteins

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7
Q

What is present on the surface of gram negative bacteria, that is not found on the surface of gram positive?

A

Lipopolysaccharides

Outer membrane proteins

Porins

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8
Q

Where is the ‘O-antigen- found on a gram negative bacterium?

A

On the lipopolysaccharide

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9
Q

What are the main types of Gram positive aerobic cocci?

A

Staphylococci - Clusters

Streptococci + enterococci - Chains

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10
Q

Staphylococcus aureus is a major pathological bacterium.

What are it’s key features?

A

Commensal organism

Carried in nose, axilla & perineum

Diseases from boils/abscesses, soft tissue infection to septicaemia & osteomyelitis

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11
Q

What is a major problem regarding antibiotic resistance by Staph. aureus?

A

Commonly penicillin resistant due to production of penicillinase

Other strains are methicillin resistant - MRSA major infection problem in hospitals

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12
Q

What does ‘staphylo___’ indicate about a bacteria?

A

Forms in clusters

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13
Q

What are the main coagulase negative staphylococci bacteria?

A

S. epidermis
S. haemolyticus
S. saprophyticus
S. lugdunensis

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14
Q

Coagulase negative staphylococci bacterium tend to be commensals where?

A

On the skin

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15
Q

How are Streptococci bacteria further classified?

A

A-haemolytic

B-heamolytic

Non-haemolytic

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16
Q

Describe the test used to differentiate between alpha, beta and non-haemolytic streptococci bacteria

A

Blood agar test

  • Alpha - partial haemolysis - agar turns green
  • Beta - complete haemolysis - agar turns clear
  • Non-H - no haemolysis - no change to the agar
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17
Q

What are the 2 main types of alpha haemolytic streptococci bacteria?

A

Strep. pneumoniae - pneumonia + meningitis

Strep. “Viridans” - endocarditis

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18
Q

What are the groups of beta haemolytic streptococci bacteria?

How are these groups differentiated?

A

Groups A-G

Grouped according to their carbohydrate surface antigen

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19
Q

What are the main features of Group A Strep Bacteria?

A

Group A = Streptococcus pyogenes

“Flesh eating bacteria”

Causes:

  • Pharyngitis
  • Cellulitis
  • Necrotising fasciitis
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20
Q

What are the main features of group B Strep bacteria

A

Group B = Streptococcus agalactiae

Causes:

  • Neonatal sepsis - meningitis, bacteraemia
  • Invasive infections in adults

Commonly carried in genital tract of woman (25%)

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21
Q

What are the main features of group D Strep bacteria

A

Now reclassified as Enterococcus bacteria

Often non-haemolytic

Found as commensal in gut

Cause:

  • UTI
  • Infective endocarditis
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22
Q

Describe the main features of Clostridium difficile

A

Anaerobic Gram positive

Bacilli shaped

Causes:

  • Pseudomembranous colitis
  • Leading to diarrhoea (after antibiotic usage)

Often carried asymptomatically

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23
Q

How would you test someone for infection by Clostridium difficile?

A

ELISA test

Detect antigen & toxin in stool sample

24
Q

What health conditions can be caused by Clostridium perfringens?

A

Gastroenteritis

Gangrene

25
Q

What condition is caused by the toxin, released by Clostridium tetani?

A

Tetanus

26
Q

What are the two main species of Gram negative Cocco bacteria?

A

Neisseria spp

Moraxella spp

27
Q

What health conditions are associated with Neisseria meningitidis?

A

Meningitis - inflammation of the meninges

Septicaemia - basically blood poisoning

28
Q

What is the coagulase test?

A

Test for Staphylococcus aureus bacteria

Positive = aureus

29
Q

What are the health conditions associated with Neisseria gonorrhoeae?

A

Gonorrhoeae

Urethritis in men
Pelvic inflammatory disease in women

30
Q

Moraxella catarrhalis is a causative agent of what?

A

Respiratory tract infections

Especially in those with previous lung pathologies

31
Q

What is a useful preliminary test to identify the type of a gram negative bacteria?

A

Lactose fermentation test

Culture using MacConkey agar (MAC)

Useful for identifying enterobacteria - these ferment lactose

32
Q

Describe the main features of MacConkey agar, and how it is used

A

Contains bile salts + crystal violet to inhibit growth of Gram positive bacteria

Neutral red indicator - If bacteria ferments lactose, then it will turn pink

33
Q

Describe the main features of Escherichia coli

A

Colliform, aerobic
Gram negative
Lactose fermenting

Causes (pathogenic serotypes):

  • UTI
  • Diarrhoea
  • Haemolytic uraemic syndrome (HUS)

Many serotypes exist - some are commensal, some are pathogenic

34
Q

What are the main features of Salmonella enterica

A

Colliform, aerobic
Gram negative
Does not ferment lactose

Causes:

  • Diarrhoea
  • Enterocolitis (inflam of SI & colon)

Many serotypes - all pathogenic

35
Q

What is the most important pathogenic serotype of E.coli?

A

Serotype O157

Associated with haemolytic uraemic syndrome (HUS)

36
Q

What are the main features of Salmonella typhi?

A

Colliform, aerobic
Gram negative
Does not ferment lactose

Causes:

  • Typhoid fever
  • Constipation & fever (early stages)

Can be isolated from blood cultures & faeces for identification

Vaccine avalaible

37
Q

What health conditions are caused by the coliform, Shigella spp?

A

Diarrhoea

Dysentery

38
Q

What health conditions are associated with the colliform, Klebsiella spp?

A

UTI

Hospital acquired pneumonia

39
Q

What health conditions are associated with the colliform, Proteus spp?

A

UTI

Stones

40
Q

What shape does ___bacter imply?

A

Curved bacilli

41
Q

What are the main features of curved bacilli bacteria?

A

Microaerophilic
Gram negative

Two groups based on shape:

  • Spiral
  • Small
42
Q

What are the main features of Campylobacter spp?

A

Gram negative
Microaerophilic
Small curved bacilli

Causes:
- (Bloody) diarrhoea - commonest cause in the UK

Faecal-oral route
Domestic animals & chickens

43
Q

What are the main features of Helicobacter pylori?

A

Gram negative
Microaerophilic
Spiral curved bacilli

Causes:

  • Stomach ulcers
  • Damges mucosa
  • Strong risk factor for gastric adenocarcinoma
44
Q

What are the main features of Haemophilus influenzae?

A

Cocci-bacilli mixed appearance
Gram negative
Aerobic
Small bacilli

Causes:
- Respiratory tract infection

45
Q

What are the main features of Pseudomonas spp, and why are they a problem in hospitals?

A

Gram negative
Aerobic
Bacilli shaped

Hospital acquired source of sepsis: UTI, bacteraemia, pneumonia

Resistant to antibiotics
Can contaminate equipment

46
Q

What are the main types of anaerobic Gram negative bacteria?

A

Bacteroides spp

Prevotella

Porphyromonas

47
Q

What health condition may be caused by Bacteroides?

A

Abdominal abscesses

48
Q

What are the main features of Oral anaerobes?

A

Prevotella
Porphyromonas

Causes/associations:

  • Periodontal disease
  • Polymicrobial dental abscess (part of)
  • Role in aspiration pneumonia
  • Human & animal bite infections
49
Q

Not all bacteria can be classified according to Gram staining, and are miscellaneous.

What important bacteria types are miscellaneous?

A

– Mycobacterium spp

– Spirochaetes.

– Chlamydia / Chlamydophila.

50
Q

What would you use to stain Mycobacterium ?

A

Ziehl-Neelsen (ZN) or Auramine

51
Q

What are the main types of Mycobacterium and their associated health conditions

A

Myco. tuberculosis - tuberculosis

Myco. leprae - leprosy

52
Q

What other health condition is linked to Tuberculosis?

A

HIV

53
Q

What are the main features of spirochaetes?

A

Gram negative

Long, spiral shaped bacteria

Identified using serology

54
Q

What diseases are caused by spirochaetes?

A

Syphilis

Lyme disease

Leptospirosis

55
Q

What are the main features of Chlamydia bacteria

A

Obligate intracellular bacteria
Gram negative

Can not be cultured

Diagnosed by serology

Causes:
- Respiratory tract infections
- Ophthalmic & genital tract infections  
- Trachoma (eye infections) 
- Genital & neonatal infections 
-
56
Q

How would you diagnose someone with Chlamydia trachomatis

A

nucleic acid amplification tests (NAAT) on first void urine or vulval/vaginal swabs

Principles of dizzees (28 decks)

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