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Opportunistic Infections Flashcards

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1
Q

When does a bacterium not need to be as virulent to cause infection?

A

When host resistance is reduced

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2
Q

What are the frequently encountered opportunistic pathogens?

A

E. coli

Staph. aureus

Klebsiella pneumoniae

Enterococcus spp.

Pseudomonas aeruginosa

Enterobacter spp.

Serratia spp.

Proteus spp.

Clostridium difficile

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3
Q

What kind of epidemic can many of the opportunistic pathogens cause?

A

Nosocomial epidemics

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4
Q

Which of the opportunistic pathogens can’t cause nosocomial epidemics?

A

E. coli

Proteus spp.

Clostridium difficile

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5
Q

What do opportunistic infections in a patient often indicate?

A

That there is something else wrong with the patient because the host must be altered in some way for pathogens to take hold.

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6
Q

Which local defects in a patient can lead to opportunistic infections?

A

Anatomical defects

Surgical and other wounds

Burns

Catheterisation

Foreign bodies in general

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7
Q

Why does a foreign body in the patient often lead to opportunistic infections?

A

Because the pathogen can find refuge in the foreign body

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8
Q

What type of anatomical defects can lead to opportunistic infections?

A

Short urethra in women can lead to UTIs

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9
Q

How can surgery lead to an opportunistic infection?

A

Breaking of the skin means it is more likely to become infected.

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10
Q

Which systemic defects in a patient can lead to opportunistic infections?

A

Extremes of age

Leukopaenia

Malignancy

Malnutrition

Diabetes

Liver disease

Immunocompromising infections

Antimicrobial treatment

Immunodeficiencies

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11
Q

What is candadiasis one of the first indications of?

A

Diabetes

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12
Q

Which infections can lead to an increased likelihood of opportunistic infections?

A

HIV

Measles

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13
Q

What are the different types of opportunistic infection?

A

Wound infection

UTI

Intra-abdominal infection

Septicemia (sepsis)

Meningitis

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14
Q

Which group of people are particularly susceptible to meningitis?

A

Neonates

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15
Q

What are the two sources of opportunistic infections?

A

Endogenous (own microbiota) and exogenous

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16
Q

What are the different types of specimens that can be cultured?

A

Wound swab

Pus

Urine

Sputum

Blood

CSF

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17
Q

What does treatment of opportunistic infections depend on?

A

Antibiotic susceptibility

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18
Q

True or false: nosocomial strains are often multi-resistant.

A

True

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19
Q

What is used to treat multi-resistant nosocomial strains of opportunistic pathogens?

A

More potent bactericidal agents

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20
Q

What are the 2 ways of preventing opportunistic nosomial pathogens?

A

Aseptic technique (esp. hand hygiene)

Education

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21
Q

Is pseudomonas G- or G+?

A

Gram negative

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22
Q

What morphology is pseudomonas?

A

Rod

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23
Q

Is pseudomonas motile?

A

Yes

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24
Q

What is pseudomonas’ relationship with oxygen?

A

It’s an aerobe or facultative anaerobe

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25
Is pseudomonas fermenting or non-fermenting?
Non-fermenting
26
Is pseudomonas sporing or non-sporing?
Non-sporing
27
What would the results for catalase and oxidase be for pseudomonas?
Catalase and oxidase positive
28
What do some species of pseudomonas, e.g. pseud. aeruginosa, produce?
Pigments - e.g. pyocyanin in ps. aeruginosa.
29
Why can pseudomonas survive almost anywhere?
Because it has low nutritional requirements
30
How is pseudomonas divided into species?
According to biochemical tests
31
What is pseudomonas aeruginosa subtyped according to?
Serotype and biotype
32
How is pseudomonas aeruginosa subtyped in epidemiological studies?
Using RFLP or MLST (multilocus sequence typing)
33
In which patients is ps. aerugonisa an important opportunistic pathogen?
Patients with cystic fibrosis
34
Which species of pseudomonas is a ubiquitous saprophyte?
Pseudomonas aeruginosa
35
What are the 4 species of of pseudomonas that colonise the respiratory tract of patients with cystic fibrosis?
Ps. aeruginosa Burkholderia cepacia Stenotrophomonas maltophilia Burkholderia pseudomallei
36
Which species of genera of Burkholdia causes melioidosis?
Burkholderia pseudomallei
37
What type of environments is ps. aeruginosa particularly found in?
Moist environments
38
What does ps. aeruginosa transiently colonise?
Skin Mucous membranes GIT
39
Which diseases is ps. aeruginosa mostly associated with as a nosocomial pathogen?
Pneumonia UTI Sepsis
40
Where are most ps. aeruginosa infections acquired from?
Environment
41
How are ps. aeruginosa inspections spread in hospitals?
On hands and fomites
42
What are all pseudomonas strains inherently resistant to?
Many antibiotics and weak disinfectants
43
Which 2 areas can ps. aeruginosa cause superficial infections?
Skin and eye
44
Which superficial infections of the skin can ps. aeruginosa cause?
Wound infection Otitis externa Folliculitis
45
Which superficial infections of the eye can ps. aeruginosa cause?
Keratitis Corneal ulcer
46
Which two types of deep and systemic infections can ps. aeruginosa cause?
Pulmonary Other
47
Which pulmonary deep infections can ps. aeruginosa cause?
Nosocomial pneuomina Chronic infections in patients with cystic fibrosis
48
Which other deep and systemic infections can ps. aeruginosa cause?
UTI Endocarditis Osteomyelitis Septicaemia In immunocompromised patients
49
When will ps. aeruginosa invade the skin?
When in very high numbers
50
What does ps. aeruginosa adhere to weakly?
Intact epithelium
51
What does ps. aeruginosa use to adhere to the intact epithelium?
Flagella Pili LPS
52
What components of ps. aeruginosa bind to toll-like receptors?
LPS and flagellin
53
What effect does binding to toll-like receptors have?
Cytokine production
54
What does the LPS core of ps. aeruginosa bind to?
CFTR | CF transmembrane conductance region
55
What does ps. aeruginosa do once it has adhered?
Produces a biofilm
56
What assists adherence and biofilm formation?
Capsule
57
What are the properties of ps. aeruginosa biofilms that are different to individual ps. aeruginosa?
More capsule material - mucoid phenotype More adherent Less invasive Shorter LPS (no O-antigen) Slowed growth Increased resistance to antibiotics
58
What is the advantage of the ps. aeruginosa biofilm?
Increased resistance to antibiotics
59
What are many of the biofilm properties of ps. aeruginosa due to?
Activation of genes that are regulated by quorum sensing
60
What is quorum sensing?
Regulatory cell process of signalling between bacteria that ensures there is sufficient cell density before a gene product is made, allowing bacteria to increase in numbers before secreting a product, e.g. virulence protein.
61
What facilitates ps. aeruginosa's spread through body tissues?
Reduced PMNs Flagella Exoenzymes Exotoxins LPS-CFTR-mediated invasion
62
Which exoenzymes does ps. aeruginosa use to spread through body tissues?
Proteases Haemolysins Phospholipases Elastase
63
Which exotoxins does ps. aeruginosa use to spread through body tissues?
Exotoxin A Exoenzymes S and U These inhibit phagocytosis
64
What effect does LPS-CFTR-mediated invasion by ps. aeruginosa have?
Aggravates corneal damage
65
What happens in patients with a defect in CFTR?
Abnormal ion transport Thickened mucus Impaired mucociliary function
66
Are pseudomonas and staph. inhibited by high salt concentrations?
No
67
What do bacteria in biofilms resist?
Mechanical removal
68
Are bacteria in biofilms more or less visible to the innate immune system?
Less
69
What happens when DNA is secreted from the bacteria and dying cells in a biofilm?
Leads to thickened mucous
70
Which bacterial variants will persist?
Those with reduced virulence
71
What effect do the type III secreted proteins from ps. aeruginosa have?
Exoenzymes S, T, U and Y (=ExoS, ExoT, ExoU, ExoY) act on host cell targets to interfere with phagocytosis and enhance cytokine production
72
What does exotoxin A released from ps. aeruginosa do?
Blocks protein synthesis (same as diphtheria toxin)
73
What do LasA and LasB proteases released from ps. aeruginosa do?
Act together as elastase
74
What do phospholipases released from ps. aeruginosa do?
Damages cell membranes Degrades surfactant
75
Can pseudomonas be eradicated from the environment?
No
76
How can ps. aeruginosa be controlled?
Reduce risk of susceptible patients by suitable management of burns, neutropenia, catheters, ventilators Be on alert for infection and treat early Practice high levels of hand hygiene Use contact lenses and solutions appropriately Lifelong monitoring and treatment of CF patients
77
What allows ps. aeruginosa to occupy many different environments?
Its low nutritional requirements and genetic versatility
78
What is the leading cause of hospital-acquired infections?
Ps. aeruginosa
79
What does ps. aeruginosa have a preference for in humans?
Situations where innate immunity is reduced
80
What is the key to controlling pseudomonas infections?
Prevention

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