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Session 6 Flashcards

(116 cards)

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1
Q

What is the most common congenital cardiac defect?

A

Bicuspid aortic valve

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2
Q

Bicuspid aortic valve is associated with which infection?

A

Infective endocarditis

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3
Q

Why is bicuspid aortic valve associated with infective endocarditis?

A

The structural abnormality and abnormal tissue provide a surface for bacteria to stick and form a colony

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4
Q

Other than infective endocarditis, name two consequences of bicuspid aortic valve

A

Aortic stenosis

Aortic incompetence

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5
Q

In adulthood, bicuspid aortic valve can present with…

A

Heart failure

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6
Q

Why does the endocardium normally resits bacterial seeding and infection?

A

It is non-sticky

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7
Q

Most cases of infective endocarditis relate to ___________ defects.

Give another risk factor for endocarditis

A

Structural

Injectable drug use

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8
Q

In infective endocarditis, a _____________ is formed that binds to valves or the endocardium

A

Vegetation

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9
Q

What forms the basis of the vegetation that begins infective endocarditis?

What can cause this vegetation to be more likely to form?

A

Collection of fibrin, platelets and inflammatory cells

Abnormal blood flow

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10
Q

How does infective endocarditis progress once a vegetation has been formed?

A

Microorganisms bind to the vegetation and cause local infection - further platelets, fibrin, inflammatory cells and bacteria invade resulting in an infection cascade.

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11
Q

How do microorganisms enter the heart to cause infective endocarditis? Where can these microorganisms come from?

A

Through the blood stream

Skin, mouth

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12
Q

Why is infective endocarditis difficult to eradicate?

Why is it hard to treat infective endocarditis with antibiotics?

A

Micro colonies of bacteria deep in the vegetation are dormant (hard to eradicate)

Hard for the antibiotics to penetrate the vegetation

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13
Q

What is often the treatment given for infective endocarditis?

A

Surgery to remove the valve and replace it with an artificial valve

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14
Q

Give an example of a commensal on the skin that has low virulence but can cause infection if travels in the blood and sticks to artificial surfaces

A

Staphylococcus epidermis

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15
Q

What does staphylococcus epidermis do at an artificial surface (e.g. Prosthetic joint) too cause infection?

A

Produces slime which contributes to the development of a biofilm that is hard to get rid of

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16
Q

What is a biofilm?

A

A thin but robust layer of mucilage adhering to a solid surface containing a community of microorganisms (bacteria)

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17
Q

How does the biofilm produced in the infection of prosthetic joints with staphylococcus epidermis protect the bacteria?

A

The extracellular matrix protects the bacteria from exposure to innate immune defences (opsonisation/phagocytosis) and antibiotic treatment

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18
Q

Define a surface

A

Interface between a solid and either a liquid or gas

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19
Q

Give three examples of mucosal surfaces in the body

A

Gastrointestinal
Respiratory
Genitourinary
Conjunctival

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20
Q

Are viruses generally found as commensals on the skin?

Give two examples of viruses that affect the skin

A

No - usually all cause infection

HPV
Herpes Simplex

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21
Q

Is Staph aureus gram positive or gram negative?

A

Gram positive

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22
Q

Is coagulase negative staphylococci, gram positive or gram negative?

A

Gram positive

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23
Q

Is corynebacterium, gram-positive or gram-negative?

A

Gram positive

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24
Q

Is enterobacteriaceae, gram positive or gram negative?

A

Gram negative

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25
Name two types of fungi that can affect the skin Name a parasite that can affect the skin
Yeasts Dermatophytes Mites
26
Name a normal flora of the eye
Coagulase negative staphylococci
27
Name a normal flora of the nares (nostrils)
Staphylococcus aureus
28
Name two normal flora of the nasopharynx
Haemophilus influenzae Neisseria meningitidis Streptococcus pneumoniae
29
Name a normal flora of the mouth
Viridans streptococci
30
Name two normal flora of the stomach
Helicobacter bacteria Streptococci bacteria Lactobacilli bacteria Staphylococci bacteria
31
Name a normal flora of the intestine
Lactobacillus bacteria
32
Name a normal flora of the urethra
Enterobacteriaceae
33
Name a normal flora of the vagina
Lactobacilli bacteria
34
What is another name for the microbiota? What is the microbiota?
Commensals Microorganisms that are carried on the skin and mucosal surfaces
35
Give two examples of external natural surface infections
Cellulitis Conjunctivitis UTI Pharyngitis
36
Give two examples of internal 'natural' surface infections
Endocarditis | Septic arthritis
37
Give 4 examples of prosthetic surfaces that can be sites for infections in humans
``` Intravascular lines Prosthetic joints Cardiac valves Peritoneal dialysis catheters Pacing wires ```
38
The causative organism for valve infective endocarditis depends on... (2)
Whether it is an artificial or native valve | Time since prosthetic valve surgery
39
Does a wider range of causative organisms cause valve endocarditis in native valve endocarditis or prosthetic valve endocarditis?
Native valve endocarditis (and post prosthetic valve surgery over a year)
40
Most bacteria/fungi can cause endocarditis in native valves Name two microorganisms that could be the cause of endocarditis in native valves/>1 yr post prosthetic valve surgery
Viridans streptococci Staph aureus Candida albicans
41
What bacteria most commonly causes prosthetic valve endocarditis under a year post-operation?
Coagulase negative staphylococci
42
Name two common causative organisms for prosthetic joint infections
Coagulase negative staphylococci | Staph aureus
43
Name two common causative organisms for cardiac pacing wire endocarditis
Coagulase negative staphylococci | Staph aureus
44
Name the 4 steps involved in the pathogenesis of surface infections
Adherence to host cells/prosthetic surface Biofilm formation Invasion and multiplication Host response
45
How do bacteria adhere to host cells/prosthetic surfaces in surface infections
Through pili or fimbriae to the host cell membrane/prosthetic surface
46
What is a biofilm?
A thin but robust layer of mucilage adhering to a solid surface containing a community of microorganisms (bacteria)
47
What is the colloquial name for a biofilm
Slime
48
The recruitment of neutrophils in the host response of surface infections results in the production of...
Pus
49
The recruitment of fibroblasts, lymphocytes and macrophages in the host response of surface infections results in the production of...
Nodular inflammatory lesions
50
What is quorum sensing? How do bacteria use it?
A system of stimuli and response correlated to population density To coordinate gene expression according to the density of their local population
51
What molecules are produced by bacteria to control the production of biofilm in bacteria depending on the local population density?
Autoinducers
52
What role do autoinducers play in bacteria in a surface infection?
Bind to cell surface/cytoplasmic receptors on the bacterial cell ---> switches on gene expression ---> increased biofilm/autoinducer production
53
State two challenges posed in trying to identify an infecting organism and its antimicrobial susceptibilities in surface infections
Adherent organisms - hard to remove | Low metabolic state bacteria - hard to culture
54
Name two ways of diagnosing the infecting organism and its antimicrobial susceptibilities in surface infections
Blood cultures | Tissue/prosthetic material sonication and culture
55
What happens in tissue/prosthetic material sonication?
Bacteria is agitated with rapid 'shaking'
56
What is meant by bioburden?
The number of bacteria living on a non-sterilised surface
57
Why are antibacterials not very effective in the treatment of surface infections?
Due to the barrier created by the biofilm
58
Name three ways surface infections are measured
Antibacterials Removal of prosthetic material Surgery - removal of infected material
59
What are two challenges posed by the management/treatment of surface infections
There is poor antibacterial penetration into the biofilm | There is low metabolic activity of biofilm microorganisms
60
Describe the metabolic activity of biofilm microorganisms
Low metabolic activity
61
Why does the low metabolic activity of bacteria pose challenges in the treatment of surface infections with antibacterials
Antibiotics usually only work when bacteria is metabolically active
62
What protects the bacteria from host/antibacterial attack in surface infections
Biofilms
63
What type of bacteria are Streptococci?
Gram positive cocci
64
What colour will streptococci appear in a gram stain?
Purple (gram +ve)
65
What is the arrangement of streptococci?
Cocci chain shaped
66
How are Streptococci classified?
By haemolysis - how they affect (haemolyse) RBCs
67
Name three categories of Streptococci based on haemolysis
Alpha haemolytic Beta haemolytic Gamma haemolytic
68
How do alpha haemolytic Streptococci affect RBCs?
Partially lyse RBCs
69
How do beta-haemolytic Streptococci affect RBCs?
Completely lyse RBCs
70
How do gamma haemolytic Streptococci affect RBCs?
Don't lyse RBCs
71
How do alpha haemolytic Streptocci appear in a blood agar plate? Give an example
Green appearance Streptococcus pneumoniae
72
How do beta haemolytic bacteria appear in a blood agar plate? Give an example
Halo 'white' appearance Streptococcus pyogenes
73
Give an example of a gamma haemolytic Streptococci
Enterococcus faecalis
74
The alpha haemolytic Streptococci are collectively known as the ____________ streptococci Why?
Viridans Green appearance in blood agar plate
75
How can different species of Streptococci be classified apart from by haemolysis? (3)
Based on their cell wall antigens - Lancefield antigen classification Sherman classification 16S ribosomal RNA sequences
76
How does the Lancefield antigen classification classify Streptococci?
Based on their cell wall antigens
77
Which groups does the Sherman classification of Streptococci divide the bacteria into? Which of these groups is not common in humans?
Pyogenic Viridans Enterococcal Lactic streptococci (not common in humans)
78
How can the 16S ribosomal RNA sequences of Streptococci be used to classify them?
The sequences are species specific and can therefore be used to classify the Streptococci
79
Name a type of 'Group A Strep' in the Lancefield antigen classification
Streptococcus pyogenes
80
Give an example of a 'Group B Strep' in the Lancefield antigen classification
Streptococcus agalactiae
81
What is S agalactiae a common cause of? In which group of the Lancefield antigen classification does it belong? In which part of the body is it found as normal flora?
Neonatal sepsis Group B Vagina
82
What category of the Lancefield antigen classification does Strep pyogenes belong? What category does it belong to by haemolysis?
Group A Beta-haemolytic
83
Name 3 virulence factors of Strep pyogenes
M protein Streptokinase Streptococcal pyrogenic exotoxins ``` DNAases Hyaluronic acid capsule Streptolysins Adhesins Hyaluronidase ```
84
How does the hyaluronic acid capsule of Strep pyogenes aid its survival?
Inhibits phagocytosis by neutrophils/macrophages
85
Why is the hyaluronic acid capsule of Strep pyogenes a poor immunogen?
It is similar to human connective tissue hyaluronic acid
86
What are M proteins in Strep pyogenes?
Long chain proteins sticking out from Strep pyogenes
87
How do M proteins on Strep pyogenes aid in its survival?
Act as resistance to phagocytosis
88
How do M proteins provide Strep pyogenes with resistance to phagocytosis?
They inhibit activation of the alternative complement pathway on bacteria cell surface
89
Do all Strep pyogenes have the same M proteins?
No, there are many antigenically different serotypes of M proteins
90
What role do Streptolysins (O and S) play in Strep pyogenes?
Lysis of erythrocytes, neutrophils and platelets
91
What role does hyaluronidase play in Strep pyogenes?
Degrades hyaluronic acid in connective tissue
92
What role does streptokinase play in Strep pyogenes?
Dissolves clots by converting plasminogen to plasmin
93
What role do streptococcal pyogenic exotoxins play in Strep pyogenes?
Cleaves IgG bound to Strep pyogenes (group A strep)
94
What is another name for Streptococcal pharyngitis?
Strep Sore Throat
95
What is the common cause of Streptococcal pharyngitis?
Strep pyogenes
96
Streptococcal pharyngitis is common in which group of people?
Children
97
How is Streptococcal pharyngitis spread?
By droplet spread
98
Name three common clinical features of Streptococcal pharyngitis
Abrupt, onset sore throat Fever Headache
99
Is streptococcal pharyngitis commonly treated with antibiotics?
No
100
Why is it common to not treat streptococcal pharyngitis with antibiotics?
Untreated patients develop M protein specific antibody
101
Name 4 complications of streptococcal pharyngitis
Scarlet fever Suppurative conditions Acute rheumatic fever Acute post-streptococcal glomerulonephritis
102
When does scarlet fever develop from streptococcal pharyngitis?
When infection is by a particular strain of Strep with particular exotoxins
103
Name some clinical features of scarlet fever?
``` Rash High fever Sepsis Arthritis Jaundice ```
104
What are suppurative complications?
Pus-forming complications - e.g. Abscess
105
Acute rheumatic fever involves inflammation of...
Heart, joints and CNS
106
Name 4 Streptococcus pyogenes skin infections
Impetigo Erysipelas Cellulitis Necrotising fasciitis
107
Impetigo usually affects which groups of people?
Children
108
What is the most common cause of glomerulonephritis?
Impetigo
109
What does impetigo involve? (What layers does it affect?)
Initial skin colonisation by Strep pyogenes followed by superficial intradermal infection
110
What is erysipelas? (What layers does it affect?) What is it commonly preceded by?
Dermis infection with lymphatic involvement Pharyngitis
111
What is cellulitis (what layers does it affect)?
Skin and subcutaneous tissue infection
112
Give two risk factors of cellulitis
Injection drug use | Impaired lymphatic drainage
113
What is necrotising fasciitis? (What layers does it affect?)
Infection of deeper subcutaneous tissues and fascia. Rapid and extensive necrosis occurs.
114
Name three clinical features of necrotising fasciitis
High fever Severe pain High mortality
115
Necrotising fasciitis is usually secondary to...
Skin break
116
What is streptococcal toxic shock syndrome? What does it result in? (3)
When there is deep tissue infection with Strep pyogenes and entry of Strep into deeper tissues and the bloodstreams Bacteraemia, Vascular Collapse, Organ Failure

Infection (10 decks)

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