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Flashcards in Classification of pathogenic bacteria Deck (56):
1

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

Bacteria
Viruses
Parasites
Fungi

2

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

Positive - thick peptidoglycan layer

Negative - thin

3

What is another name for peptidoglycan?

Murein

4

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

Cell wall synthesising enzymes

(penicillin binding proteins)

5

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

Cell wall - teichoic acid

Membrane - lipoteichoic acid

6

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

Cell surface proteins

7

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

Lipopolysaccharides

Outer membrane proteins

Porins

8

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

On the lipopolysaccharide

9

What are the main types of Gram positive aerobic cocci?

Staphylococci - Clusters

Streptococci + enterococci - Chains

10

Staphylococcus aureus is a major pathological bacterium.

What are it's key features?

Commensal organism

Carried in nose, axilla & perineum

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

11

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

Commonly penicillin resistant due to production of penicillinase

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

12

What does 'staphylo___' indicate about a bacteria?

Forms in clusters

13

What are the main coagulase negative staphylococci bacteria?

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

14

Coagulase negative staphylococci bacterium tend to be commensals where?

On the skin

15

How are Streptococci bacteria further classified?

A-haemolytic

B-heamolytic

Non-haemolytic

16

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

Blood agar test

- Alpha - partial haemolysis - agar turns green

- Beta - complete haemolysis - agar turns clear

- Non-H - no haemolysis - no change to the agar

17

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

Strep. pneumoniae - pneumonia + meningitis

Strep. "Viridans" - endocarditis

18

What are the groups of beta haemolytic streptococci bacteria?

How are these groups differentiated?

Groups A-G

Grouped according to their carbohydrate surface antigen

19

What are the main features of Group A Strep Bacteria?

Group A = Streptococcus pyogenes

"Flesh eating bacteria"

Causes:
- Pharyngitis
- Cellulitis
- Necrotising fasciitis

20

What are the main features of group B Strep bacteria

Group B = Streptococcus agalactiae

Causes:
- Neonatal sepsis - meningitis, bacteraemia
- Invasive infections in adults

Commonly carried in genital tract of woman (25%)

21

What are the main features of group D Strep bacteria

Now reclassified as Enterococcus bacteria

Often non-haemolytic

Found as commensal in gut

Cause:
- UTI
- Infective endocarditis

22

Describe the main features of Clostridium difficile

Anaerobic Gram positive

Bacilli shaped

Causes:
- Pseudomembranous colitis
- Leading to diarrhoea (after antibiotic usage)

Often carried asymptomatically

23

How would you test someone for infection by Clostridium difficile?

ELISA test

Detect antigen & toxin in stool sample

24

What health conditions can be caused by Clostridium perfringens?

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