Pseudomonas

Question 1

What is a pseudomonas?

Answer 1

A genus of gram-negative bacteria
Aerobic
Rod-shaped
Thrives in diverse environments

Question 2

Why is pseudomonas aeruginosa most clinically significant?

Answer 2

Due to its opportunistic pathogenicity and intrinsic resistance to multiple antibiotics

Question 3

What are the key features of the structure of pseudomonas?

Answer 3

Outer membrane consisting of lipopolysaccharide (LPS) contributes to structural integrity and a thin peptidoglycan layer
Flagellum for cell motility
Pilus - short hair-like projections that help with attachment to surfaces and formation of biofilm
Capsule/slime layer - protective barrier from antibiotics and phagocytosis, also has a role in biofilm formation

Question 4

What is biofilm?

Answer 4

Communities of bacteria encased in a self-produced matrix.
Provides protection against environmental stresses, the immune system and antimicrobial treatments.

Question 5

How long do biofilms survive on surfaces?

Answer 5

For extended periods, even months!

Question 6

Why do biofilms survive on surfaces for so long?

Answer 6

Due to their ability to form biofilms and tolerate desiccation

Question 7

What is the biofilm matrix composed of?

Answer 7

Extracellular polymeric substances (EPS)

Question 8

What does the biofilm matrix do?

Answer 8

Acts as a shield
Provides a physical barrier against immune cells
Helps the bacteria withstand extreme temperatures, pH fluctuations, presence of toxins
Regulates the internal environment of the biofilm

Question 9

The biomatrix shield achieves what?

Answer 9

It makes the bacteria within the biofilm more resistant to antibiotics and other antimicrobial agents

Question 10

The physical barrier of the biofilm does what?

Answer 10

Prevent immune cells from reaching and eliminating the bacteria

Question 11

The regulation of the internal environment of the biofilm does what?

Answer 11

Creates a more stable and protective habitat

Question 12

Why does P. aeruginosa exhibit significant antimicrobial resistance?

Answer 12

Due to its advances defence mechanism

Question 13

What are the three defence mechanisms?

Answer 13

Multidrug Efflux Pumps
Beta-Lactamases
Aminoglycoside-Modifying Enzymes

Question 14

What do multidrug efflux pumps do?

Answer 14

Efficiently expel antibiotics from the bacterial cell, contributing to resistance against a wide range of antimicrobials

Question 15

What do beta-lactamases do?

Answer 15

Enzymes that degrade beta-lactam antibiotics, rendering them ineffective

Question 16

What do aminoglycoside-modifying enzymes do?

Answer 16

Chemically alter aminoglycoside antibiotics, nullifying their antibacterial effects

Question 17

What is a virulence factor?

Answer 17

A molecule produced by a pathogen that enable it to cause disease in a host organism

Question 18

P. aeruginosa employs a variety of virulence factors and toxins to enhance its ability to do what?

Answer 18

Invade host cells
Evade immune responses
Establish infections

Question 19

What are the structural virulence factors?

Answer 19

Pilus - attach to host cells and biofilm formation
Flagella - triggers immune response
Lipopolysaccharide (LPS) - contributes to inflammation and immune evasion
Alginate - component of biofilm, protects against antibiotics and phagocytosis

Question 20

What toxins and enzymes does it secrete?

Answer 20

Exotoxin A
Elastases
Alkaline protease
Procyanin
Pyoverdine

Question 21

What does exotoxin A do?

Answer 21

Inhibit protein synthesis, causing cell death

Question 22

What do elastases do?

Answer 22

Degrade immunoglobulins and proteins

Question 23

What does alkaline protease do?

Answer 23

Break down phospholipids, leading to cell death and tissue damage

Question 24

What are immunoglobulins?

Answer 24

Antibodies
Molecules produced by the body to help defend against infection

Question 25

What does procyanin do?

Answer 25

Blue/green coloured pigment Generates reactive oxygen species (ROS), causing damage to host cells

Question 26

What is reactive oxygen species?

Answer 26

A group of unstable, highly reactive molecules containing oxygen that readily react with other molecules in the cell

Question 27

What can excessive ROS production lead to?

Answer 27

Oxidative stress, causing damage to lipids, proteins and DNA

Question 28

What does pyoverdine do?

Answer 28

A green, iron-chelating (binds to iron) compound Bind to iron in the environment and transports it into bacterial cells, supporting bacterial growth and survival

Question 29

What are the environmental sources of pseudomonas?

Answer 29

Soil Water (natural and artificial sources) Wet surfaces (sinks, showers, humidifiers, air conditioning)

Question 30

What are the healthcare settings sources of pseudomonas?

Answer 30

Ventilators and respiratory equipment Catheters Dialysis equipment Contaminated dressings or medical devices

Question 31

Though an uncommon source, what in the human flora can cause pseudomonas?

Answer 31

Colonisation of skin, throat, lungs or gut. Mainly happens within hospitalised or immunocompromised patients

Question 32

What lung infection happen due to pseudomonas?

Answer 32

Pneumonia - especially in cystic fibrosis, bronchiectasis, ventilator-associated

Question 33

What are risk factors of developing a lung infection due to pseudomonas?

Answer 33

Chronic lung disease with structural changes Admission to ICU

Question 34

What urinary tract infection happen due to pseudomonas?

Answer 34

UTI

Question 35

What is the risk factor of developing a UTI due to pseudomonas?

Answer 35

Catheter use

Question 36

What blood stream infection happen due to pseudomonas?

Answer 36

Bacteraemia/sepsis

Question 37

What is the risk factor of developing a blood stream infection due to pseudomonas?

Answer 37

Being immunocompromised

Question 38

What skin and soft tissue infections happen due to pseudomonas?

Answer 38

Wound infections, particularly burns Diabetic foot infection

Question 39

What is the risk factor of developing a skin and soft tissue infection due to pseudomonas?

Answer 39

Having diabetes

Question 40

What ear infections happen due to pseudomonas?

Answer 40

Otitis externa Malignant otitis externa

Question 41

What are risk factors of developing an ear infection due to pseudomonas?

Answer 41

Being diabetes Older age

Question 42

What is the clinical presentation in diagnosing pseudomonas causing a respiratory infection?

Answer 42

Cough Green sputum production Fever Dyspnoea - difficult/laboured breathing

Question 43

What is the clinical presentation in diagnosing pseudomonas causing a urinary infection?

Answer 43

Dysuria - sensation of pain, burning, stinging or itching in urethra Increased urinary frequency Foul-smelling urine

Question 43

What is the clinical presentation in diagnosing pseudomonas causing a wound/burn infection?

Answer 43

Green-coloured discharge Fruity odour Delayed healing

Question 44

What is the clinical presentation in diagnosing pseudomonas causing an ear infection?

Answer 44

Discharge Pain

Question 45

What is p. aeruginosa famously associated with?

Answer 45

A distinctive smell Grape-like Fruity Not always present

Question 46

What creates the distinctive smell?

Answer 46

The production of a volatile organic compound (VOC) called 2-aminoacetophenone

Question 47

The presence and intensity of the odour depend on what?

Answer 47

The specific strain of pseudomonas aeruginosa The growth conditions Individual olfactory receptor

Question 47

How is patient history important when it comes to diagnosis of pseudomonas?

Answer 47

Infections due to pseudomonas are uncommon in patients without risk factors

Question 48

What are the risk factors of getting a pseudomonas infection?

Answer 48

Hospitalisation - especially ICU Immunosuppression Prolonged antibiotic use Devices - catheters, ventilators, lines Cystic fibrosis or structural lung disease

Question 49

How is microbiological testing used in diagnosing pseudomonas?

Answer 49

It discovers if a microorganism is present and what can shows which antibiotics can be used to fight the infection

Question 50

Information included in microbiological testing

Answer 50

Source type - sputum, urine etc Body site - where sample was taken from Additional information - what was identified

Question 51

What do the numbers mean next to the microorganism type on a culture sample?

Answer 51

How much of the microorganism grew The bigger the number, the more growth

Question 52

Why is it a challenge to treat p. aeruginosa?

Answer 52

Due to its intrinsic and acquired antibiotic resistance

Question 53

The choice of antibiotic for pseudomonas infection depends on what?

Answer 53

Site and severity or infection Local resistance patterns Patient factors - renal function, allergies Culture and susceptibility results

Question 54

What should be considered upon suspicion/identification of pseudomonas?

Answer 54

IV options Antipseudomonal beta-lactams - piperacillin with tazobactam (Tazocin), ceftazidime, cefepime Meropenem

Question 55

In addition to IV antibiotics, what might also be considered in severe infection?

Answer 55

Aminoglycosides - amikacin, gentamicin or tobramycin Due to their synergistic benefit - the combined effect of two antibiotics is greater than the sum of their individual effects

Question 56

What are the two steps of pseudomonas treatment?

Answer 56

1. Empiric therapy 2. Targeted therapy

Question 57

When pseudomonas aeruginosa is confirmed by culture and its antibiotic susceptibility profile (MIC) is available, what should be initiated?

Answer 57

Targeted therapy - replacing empiric broad-spectrum antibiotics with the narrowest effective agent

Question 58

Examples of targeted therapy given in pseudomonas infection

Answer 58

Fluoroquinolones - ciprofloxacin/levofloxacin (the only oral antibiotic options for treatment) Monobactam - Aztreonam

Question 59

The MIC (antibiotic susceptibility profile) determines what?

Answer 59

If the bacteria is: Susceptible Susceptible-increased exposure Resistant

Question 60

Describe susceptible bacteria

Answer 60

Standard dosing regimen High likelihood of therapeutic success using standard dosing regimen of the agent

Question 61

Describe susceptible-increased exposure

Answer 61

High likelihood of therapeutic success because exposure to the agent is increased by adjusting the dosing regimen or by its concentration at the site of infection

Question 61

Describe resistant bacteria

Answer 61

High likelihood of therapeutic failure even when there is increased exposure

Question 62

What is the dosing regime for susceptible and susceptible-increased exposure for piperacillin/tazobactam (Tazocin)?

Answer 62

IV 4.5g 8 hourly IV 4.5g 6 hourly

Question 63

What is the dosing regime for susceptible and susceptible-increased exposure for meropenem?

Answer 63

IV 1g 8 hourly IV 2g 8 hourly

Question 64

What is the dosing regime for susceptible and susceptible-increased exposure for ciprofloxacin?

Answer 64

IV 400mg 12 hourly OR orally 500mg 12 hourly IV 400mg 8 hourly OR orally 750mg 12 hourly

Question 65

What is the dosing regime for susceptible and susceptible-increased exposure for levofloxacin?

Answer 65

IV/oral 500mg 12 hourly IV/oral 750mg 12 hourly

Question 66

What infection control measures can prevent pseudomonas infection?

Answer 66

Strict hand hygiene and environmental cleaning - alcohol-based hand rub or soap after, before and between patient contact PPE - gloves, apron Isolation of patients with multidrug-resistant pseudomonas Proper sterilisation of medical equipment