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Infection > Lecture 11 - Infections On Surfaces > Flashcards

Lecture 11 - Infections On Surfaces Flashcards

1
Q

What is a surface?

A

Interface between a solid and either a liquid or gas

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2
Q

What virus can cause warts?

A

Papilloma

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3
Q

What virus causes cold sores?

A

Herpes simplex

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4
Q

What are some very Gram positive bacteria on the skin?

A

Staphylococcus aureus
Coagulase negative staphylococci (Staphylococcus which are not S.aureus)

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5
Q

What are some gram negative bacteria present on the skin?

A

Enterobacteriaceae

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6
Q

Where are gram negative bacteria like Enterobacteriaceae more commonly found on the skin?

A

Below the waist

Due to exiting the large bowel

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7
Q

What are Dermatophytes?

A

Skin fungi which are moulds (NOT yeasts)

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8
Q

What diseases do dermatophytes cause?

A

Athletes foot
Ring worm

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9
Q

What can happen if normal flora is displaced from its normal location?

A

Can cause disease

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10
Q

What are Coagulase negative staphylococci?

A

Staphylococcus species that are not staphylococcus aureus

They do not produce the enzyme Coagulase

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11
Q

What is the importance of Lactobacilli in the vagina?

A

Produce lactic acid maintaining low pH

Low pH prevents opportunistic infections like Candida Albicans

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12
Q

What are Coliforms?

A

Microorganism found in the digestive tract

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13
Q

What can happen if you get an infection from Helicobacter pylori in the stomach? (It is normal flora there)

A

Can lead to inflammation of stomach lining (Gastritis) and can cause stomach ulcers

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14
Q

What are commensals/ our microbiota?

A

Our normal flora of microorganisms that are found on the skin and mucosal surfaces

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15
Q

What can happen if Microbiota/commensals are transferred to other sites?

A

Can be harmful an d cause disease/infection

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16
Q

How can people get infections from their own commensals or Microbiota?

A

Invasion
Migration
Inoculation
Haematogenous

They have been displaced

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17
Q

What is an example of Invasion of commensals causing a disease and what is the causative organism?

A

Pharyngitis

Streptococcus pyogenes

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18
Q

What is an example of Migration of commensals causing a disease and what is the causative organism?

A

Urinary Tract Infection (UTIs)

Escherichia coli

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19
Q

What is an example of Innoculation of commensals causing a disease and what is the causative organism?

A

Prosthetic joint infection

Coagulase-negative Staphylococcus

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20
Q

What is an example of Haematogenous infection of commensals causing a disease and what is the causative organism?

A

Infective endocarditis

Viridans streptococcus

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21
Q

What are some external natural (not prosthetic) surface infections?

A

Cellulitis
Pharyngitis
Conjunctivitis
Gastroenteritis
UTIs
Pneumonia

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22
Q

What are some internal natural (not prosthetic) surface infections?

A

Endocarditis
Septic arthritis
Osteomyelitis
Emphysema

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23
Q

What is gastroenteritis?

A

Inflammation of large bowel mucosa

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24
Q

What is endocarditis?

A

Infection of heart valve

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25
Q

What is septic arthritis?

A

Infection in joint that then spreads through the blood stream

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26
Q

What is Osteomyelitis?

A

Surface infection in cancellous spongy bone

27
Q

What is Empyema?

A

Infection of plural space around the lungs

28
Q

What is the danger with inserting objects into the body?

A

Anything inserted can act as a source of infection

29
Q

What are some example so prosthetic surface infections?

A

IV Lines
Prosthetic joints
Peritoneal dialysis catheters
Cardiac valves
Pacing wires
Endovascular grafts
Ventricular-peritoneal shunts

30
Q

What is a ventriculo-peritoneal shunt?

A

Shunt / tubing that allows the build up of CSF in the brain to drain into the peritoneal cavity where it can then be reabsorbed, helps treat the hydrocephalus

31
Q

What is a Bicuspid aortic valve?

A

Congenital cardiac defect where 2 of the 3 cusps of the aortic valve fuse
This produces a smaller fused cusp and a normal single cusp

32
Q

Why are people with a Bicuspid aortic valve at an increased risk of Endocarditis?

A

Blood flows abnormally over the abnormal valve, the microbes can then stick to the valves as a result and produce a biofilm

33
Q

What helps determine the route of infection for Prosthetic valve endocarditis?

A

The time that somebody develops Prosthetic Valve endocarditis POST OPERATION helps determine the route of infection

34
Q

What is the normal causative organism for Prosthetic valves endocarditis if they had their surgery less than a year ago?

A

Coagulase negative staphylococci

Like Staphylococcus epidermidis

35
Q

What is the mechanism of infection if someone develops Prosthetic Valve Endocarditis within less than a year of the operation?

A

Coagulase negative staphylococci during the surgery invade from the skin or are already on the prosthetic heart valve

36
Q

What are the normal causative organisms for Prosthetic valve endocarditis if they had their surgery more than a year ago?

A

Viridans streptococci
Enterococcus faecalis
Staphylococcus aureus
Gram negative bacteria from the HACEK group
Candida albicans

37
Q

How can viridans streptococci cause prosthetic valves endocarditis?

A

Viridans streptococci normally found in mouth + around teeth
Haematogenous infection, gums get abrased, dental issues like gum disease, viridans streptococci enter blood and get stuck/adhere to the prosthetic valve

38
Q

Why are organisms like viridans streptococci able to adhere to the prosthetic heart valve?

A

Flow over this valve more turbulent than a natural valve
More likely to adhere to the valve and form a biofilm

39
Q

What gut organism can cause prosthetic valve endocarditis that’s is normally found in the gut?

A

Enterococcus faecalis

40
Q

Why do you need to do bowel investigations if a patient has Enterococcus endocarditis?

A

Likely issues there if a gut organism has ended up in the blood and at the heart

41
Q

Endocarditis associated with which microorganism is very likely with IV drug use?

A

Staphylococcus aureus

42
Q

What are the 2 main causative organisms for Prosthetic joint infections?

A

Coagulase negative staphylococci
Staphylococcus aureus

43
Q

What are the risk factors of getting prosthetic joint infections?

A

Joint replacement surgery:

-Obesity
-Diabetes Mellitus
-Rheumatoid arthritis

44
Q

How do you treat a prosthetic joint infection?

A

Remove the prosthetic to sterilise the joint

45
Q

Why can you not just give antibiotics to target the causative organisms of the prosthetic joint infection?

A

They produce a biofilm which antibiotics struggle to penetrate due to bacteria reducing and having a low metabolic rate in the biofilm

46
Q

When inserting a pacing wire (pacemaker) which vein is commonly used?

A

Subclavian vein

47
Q

What are the common organisms which cause cardiac pacing wire endocarditis and where do they come from?

A

Coagulase negative staphylococci
Staphylococcus aureus

Usually picked up by the wire on insertion from the skin

48
Q

What are the 3 steps in the pathogenesis of infection at surfaces?

A

1.) Adherence/sticking to host cells or prosthetic surface

2.) Biofilm formation

3.) Invasion and multiplication

49
Q

What structures allow adherence of microbes to host cells?

A

Pilli
Fimbriae

50
Q

What is a Biofilm?

A

Microbial communities attached to surfaces and encased in an extracellular matrix produced by the microbes

51
Q

How does a Biofilm form in 3 simple steps?

A

1.) Surface attachment (forms monolayer along surface)

2.). Start producing ECM so Micro colonies form since the bacteria stick together which starts maturing the biofilm

3.) 3 Dimensional structure forms (Macro-colonies), bacteria can detach or whole colonies can detach to go onto to other sites of infection

52
Q

What is the host response to infection at surfaces?

A

Pyogenic (neutrophils, later die and form pus)

Granulomatous (fibroblasts, lymphocytes and macrophages) forms Nodular inflammatory lesions

53
Q

What is Quorum sensing?

A

The ability to detect and respond to the cell population density by gene regulation

54
Q

What substance is produced by bacteria in a biofilm which allows for Quorum sensing?

A

Autoinducers

55
Q

What is the advantage of bacteria in a biofilm producing autoinducers allowing for Quorum sensing?

A

Induce all bacteria in the biofilm to express certain genes which confer some type of advantage (e.g multi drug resistance)

56
Q

Why are bacteria in biofilms resistant to many antibiotics?

A

ECM of biofilm restricts penetration of antibiotics

Quorum sensing may stimulate all bacteria do reduce their metabolic rate to avoid being targeted by antibiotics

57
Q

What are the 3 steps to quorum sensing ?

A

Autoinducers produced (Signalling molecules)

Bacteria in biofilm detect Autoinducers on receptors

Gene expression changed

58
Q

What is the general aim in managing infections at surfaces/biofilms?

A

Identify infecting organism and its anti microbial susceptibilities

Sterilise tissue
Reduce bio burden

59
Q

Why is a biofilm good for bacteria?

A

Protects from antibiotics
Protects from phagocytes
Helps preserve nutrients in times of low resources

60
Q

How can you prevent biofilm formation on natural surfaces?

A

Maintain surface integrity
Prevent bacterial surface colonisation
Remove colonising bacteria

61
Q

How can you prevent biofilm formation on prosthetic surfaces?

A

Prevent contamination
Inhibit surface colonisation
Remove colonising bacteria

62
Q

How can a biofilm forming on a heart valve lead to problems?

A

Vegetation formed by the bacterial biofilm
Vegetation can lead to perforation of the walls of the valves

63
Q

What are some common symptoms of infective Endocarditis?

A

Splinter haemorrhages
Oslers nodes
Janeway lesions
Petechiae

Infection (21 decks)

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