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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
What condition is caused by the toxin, released by Clostridium tetani?
Tetanus
26
What are the two main species of Gram negative Cocco bacteria?
Neisseria spp Moraxella spp
27
What health conditions are associated with Neisseria meningitidis?
Meningitis - inflammation of the meninges | Septicaemia - basically blood poisoning
28
What is the coagulase test?
Test for Staphylococcus aureus bacteria Positive = aureus
29
What are the health conditions associated with Neisseria gonorrhoeae?
Gonorrhoeae Urethritis in men Pelvic inflammatory disease in women
30
Moraxella catarrhalis is a causative agent of what?
Respiratory tract infections Especially in those with previous lung pathologies
31
What is a useful preliminary test to identify the type of a gram negative bacteria?
Lactose fermentation test Culture using MacConkey agar (MAC) Useful for identifying enterobacteria - these ferment lactose
32
Describe the main features of MacConkey agar, and how it is used
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
Describe the main features of Escherichia coli
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
What are the main features of Salmonella enterica
Colliform, aerobic Gram negative Does not ferment lactose Causes: - Diarrhoea - Enterocolitis (inflam of SI & colon) Many serotypes - all pathogenic
35
What is the most important pathogenic serotype of E.coli?
Serotype O157 Associated with haemolytic uraemic syndrome (HUS)
36
What are the main features of Salmonella typhi?
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
What health conditions are caused by the coliform, Shigella spp?
Diarrhoea Dysentery
38
What health conditions are associated with the colliform, Klebsiella spp?
UTI Hospital acquired pneumonia
39
What health conditions are associated with the colliform, Proteus spp?
UTI Stones
40
What shape does ___bacter imply?
Curved bacilli
41
What are the main features of curved bacilli bacteria?
Microaerophilic Gram negative Two groups based on shape: - Spiral - Small
42
What are the main features of Campylobacter spp?
Gram negative Microaerophilic Small curved bacilli Causes: - (Bloody) diarrhoea - commonest cause in the UK Faecal-oral route Domestic animals & chickens
43
What are the main features of Helicobacter pylori?
Gram negative Microaerophilic Spiral curved bacilli Causes: - Stomach ulcers - Damges mucosa - Strong risk factor for gastric adenocarcinoma
44
What are the main features of Haemophilus influenzae?
Cocci-bacilli mixed appearance Gram negative Aerobic Small bacilli Causes: - Respiratory tract infection
45
What are the main features of Pseudomonas spp, and why are they a problem in hospitals?
Gram negative Aerobic Bacilli shaped Hospital acquired source of sepsis: UTI, bacteraemia, pneumonia Resistant to antibiotics Can contaminate equipment
46
What are the main types of anaerobic Gram negative bacteria?
Bacteroides spp Prevotella Porphyromonas
47
What health condition may be caused by Bacteroides?
Abdominal abscesses
48
What are the main features of Oral anaerobes?
Prevotella Porphyromonas Causes/associations: - Periodontal disease - Polymicrobial dental abscess (part of) - Role in aspiration pneumonia - Human & animal bite infections
49
Not all bacteria can be classified according to Gram staining, and are miscellaneous. What important bacteria types are miscellaneous?
– Mycobacterium spp – Spirochaetes. – Chlamydia / Chlamydophila.
50
What would you use to stain Mycobacterium ?
Ziehl-Neelsen (ZN) or Auramine
51
What are the main types of Mycobacterium and their associated health conditions
Myco. tuberculosis - tuberculosis Myco. leprae - leprosy
52
What other health condition is linked to Tuberculosis?
HIV
53
What are the main features of spirochaetes?
Gram negative Long, spiral shaped bacteria Identified using serology
54
What diseases are caused by spirochaetes?
Syphilis Lyme disease Leptospirosis
55
What are the main features of Chlamydia bacteria
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
How would you diagnose someone with Chlamydia trachomatis
nucleic acid amplification tests (NAAT) on first void urine or vulval/vaginal swabs

Principles of dizzees (28 decks)

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