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Principles of Disease-Megan > Classification of Pathogenic Bacteria > Flashcards

Classification of Pathogenic Bacteria Flashcards

1
Q

How do bacteria reproduce

A

Mainly by binary fission

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2
Q

Is cocci rod shaped or circular

A

Circular

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3
Q

Is bacilli rod shaped or circular

A

Rod shaped

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4
Q

Is staphylococci in clusters or chains

A

Clusters

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5
Q

Is streptococci in clusters or chains

A

Chains

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6
Q

What does a positive coagulase test mean

A

Staphylococcus aureus is present which may indidicate MSSA or MRSA

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7
Q

What is Staphylococcus aureus

A

A major human pathogen carried in the nose, axilla and perineum

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8
Q

What can Staphlyococcus aureus cause

A 
Wide range of diseases
Boils/abscesses
Soft tissue infections
Septicaemia 
Osteomyelitis
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9
Q

What is Staphylococcus aureus commonly resistant to and why

A

Penicillin
Due to the production of penicillinase however using a different mechanism can produce strains which are methicillin resistant

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10
Q

What does a negative coagulase test indicate

A 
Many different species such as:
S. epidemidis 
S. haemolyticus 
S. saprophyticus
S. lugdunenis
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11
Q

What are the categories of Streptococcus

A

α-haemolytic (partial haemolysis) which turns blood agar green
β-haemolytic (complete haemolysis) which turns blood agar clear
non haemolytic

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12
Q

Give an example of an α-haemolytic streptococci and what it can cause

A

Streptococcus pneumoniae which causes pneumonia, meningitis and septicaemia

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13
Q

How can β-haemolytic streptococci be further identified

A

Through carbohydrate surface antigens which are split into groups A-G

The clinically most important groups are A, B, F and D

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14
Q

How are gram positive bacilli able to grow

A

Aerobically

Anaerobically

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15
Q

Give an example of a group A streptococci

A

Streptococcus pyogenes which is a major pathogen causing pharyngitis, cellulitis and necrotising fasciitis (‘flesh eating bug’)

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16
Q

What is an important cause of diarrhoea that is which is associated with toxin production and can be potentially fatal

A

Clostridium difficile which is difficult to culture and asymptomatic when carried in the gut of healthly people

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17
Q

What increases the risk of obtaining Clostridium difficile

A

Antibiotics

Anything which disrupts the normal gut flora

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18
Q

How can Clostridium difficile spread

A

Spores

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19
Q

How is Clostridium difficile detected

A

Using its antigens and toxins in stool samples by ELISA.

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20
Q

Name 2 Gram negative cocci

A

Neisseriac spp.

Moraxella spp.

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21
Q

What is meningitis

A

Inflammation of the meninges and septicaemia

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22
Q

What does Neisseria meningitidis cause and how can it be identified

A

Meningitis which is the inflammation of the meninges and septicaemia.

PCR can be used on EDTA blood

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23
Q

What does Neisseria gonorrhoeae cause and how is it spread

A

Urethritis in men
Pelvic inflammation disease in women
Sexual contact

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24
Q

What does Moraxella catarrhalis act as the causative agent for

A

Respiratory tract infections especially in those with underlying lung pathology.

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25
Q

What are coliforms

A

Organisms which are in the Enterobacteriaceae family

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26
Q

Where are coliforms mainly found

A

Human large intestine

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27
Q

What is a useful test to identify Gram negative bacteria

A

Lactose fermentation is useful as a preliminary test

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28
Q

What are the virulance factors for E. coli

A

Pili
Capsule
Endotoxin
Exotoxins

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29
Q

Where can E. coli be found

A

Human and animal reservoirs

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30
Q

What does E. coli ferment

A

Lactose

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31
Q

How many serotypes of E. coli are there and what are they based on

A

Over 160

Based on O antigen (LPS)

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32
Q

What can E. coli cause

A

UTI’s

33
Q

Name two types of E. coli

A

Enterotoxogenic

Enterohaemorrhagic

34
Q

What can enterohaemorrhagic cause

A

Bloody diarrhoea

Haemolytic uraemic syndrome (HUS) which is associated with E. coli O157

35
Q

What can enterotoxogenic cause

A

A common cause of traveller’s diarrhoea

36
Q

Can the Salmonella spp. ferment lactose

A

No

37
Q

What can the Salmonella spp. cause

A

Self-limiting enterocolitis with or without bloody diarrhoea

It has an incubation period of 12-48 hours

38
Q

Can Salmonella enter the bloodstream

A

Yes

39
Q

What can Salmonella typhi cause and what are its symptoms

A

Typhoid fever
Symtoms include:
Fever
Constipation in the early stages

40
Q

Where can Salmonella typhi be isolated from

A

Blood cultures

Faeces

41
Q

Name 3 coliforms

A

Shigella spp
Klebsiella spp
Proteus spp

42
Q

Is E. coli a coliform

A

Yes

43
Q

How does the Campylobacter spp grow

A

In the presence of low oxygen

44
Q

What is the source of Campylobacter

A

Domestic animals e.g. Chickens

45
Q

How can Campylobacter be transmitted

A

Faecal-oral route (incubation period of 2-5 days)

46
Q

What can Campylobacter cause

A

Foul smelling then bloody diarrhoea

47
Q

What type of bacteria is Campylobacter

A

Curved Gram negative bacilli

48
Q

What type of bacteria is Helicobacter pylori

A

Curved Gram negative bacilli

49
Q

What is Helicobacter pylori’s natural habitat

A

Human stomach

50
Q

What can Helicobacter do

A

Damage mucosa
Cause ulcers
A strong risk factor for gastric adenocarcinoma

51
Q

What does the Haemohilus influenzae virus appear as

A

Cocco-bacilli

52
Q

What can the Haemohilus influenzae virus cause

A

Respiratory tract infections

53
Q

What can the capsulate form (type b) of Haemohilus influenzae cause

A

Meningitis in children

54
Q

Where can Pseudomonas colonise

A

Water and soil

e.g. drains, sinks, mops

55
Q

What type of nosocomial infection can Pseudomonas cause

A

Sepsis (e.g. UTI, bacteramia, pneumonia)

56
Q

How can the Pseudomonas spp be treated

A

Has limited treatment options as it has multi-drug resistance mechanisms

57
Q

What are anaerobes normally a part off

A

Polymicrobial infection

58
Q

Name some anaerobes

A

Bacteriodes spp.
Prevotella
Porphyromonas

59
Q

Describe Bacteroides fragilis

A

Part of normal colonic flora
Can cause intra-abdominal abscess
May spread to other sites

60
Q

What do oral anaerobes have a role in

A

Aspiration pneumonia

Human and animal bite infections

61
Q

Can all bacteria be Gram stained

A

No

62
Q

Give examples of bacteria which cannot be Gram stained

A

Mycobacterium spp.
Spirochaetes.
Chlamydia

63
Q

What is acid and alcohol fast bacilli (AAFB)

A

This type of bacilli are resistant to decolourisation by acid or alcohol once it has been stained with carbol fuchsin

64
Q

How can Mycobacterium be visualised

A

Using Ziehl-Neelsen staining
Auramine staining

This does do help identify the species

65
Q

How can a Mycobacterium species be identified

A

Culture

The new automated liquid culture allows growth to occur within 2-4 weeks.

66
Q

What causes TB

A

Mycobacterium tuberculosis

67
Q

When is rapid diagnostic nucleic acid amplification tests recommended for pulmonary TB diagnosis

A

When TB is suspected in a HIV positive patient
When rapid information about the mycobacterial species would alter a persons care
When a large contact tracing initiative is being explored

68
Q

What can Mycobacterium leprae cause

A

Leprosy

69
Q

Can Mycobacterium leprae be cultured

A

No

70
Q

What are spirochaetes

A

Long, spiral shaped bacteria

71
Q

How can spirochaetes be visualised

A

Not very well with light microscopy but can be seen with immunofluorescence

72
Q

Name some spirochaete diseases

A

Syphilis caused by Treponema pallidum
Lyme disease caused by Borrelia burgdorferi
Leptospirosis caused by Leptospira interrogans

73
Q

What is primary syphilis

A

Non-painful skin lesions (chancre) at the site of infection, usually the skin or mucous membranes

74
Q

What is secondary syphilis

A

Occurs 6-8 weeks after the primary symptoms causing generalised systemic illness and rash

75
Q

What is tertiary syphilis

A

Can occur years after the primary symptoms and affects the CNS

76
Q

How can syphilis be diagnosed

A

Serology

Nucleic acid amplification tests

77
Q

What is Chlamydia

A

An obligate intracellular bacteria that can only be cultured in cell lines

78
Q

What type of chlamydia causes genital tract infections

A

Chlamydia trachomatis

79
Q

How can Chlamydia trachomatis be diagnosed

A

Using NAAT on the first void urine or vulval/vaginal swabs

Principles of Disease-Megan (41 decks)

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