Denise - Pseudomonas Flashcards
What are the reservoirs for Pseudomonas
Free-living bacterium
Found in the environment (soil, water, sewage, moist surfaces, hot tubs)
Found on plants and animals
When can pseudomonas cause problems
(3)
Plant pathogens
Food spoilage organisms
Bioremediation - present in water
How would pseudomonas be transmissed
(4)
Direct contact with water - ingestion or bathing
Inhalation of aerosols
Medical Devices rinsed with contaminated water
Indirect contact from contaminated surfaces via the hands of health care workers
How common is pseudomonas in the lab?
(4)
15% of clinical bacterial isolates in the lab
Very common hospital acquired infection
Often multi drug resistance
An ESKAPE Pathogen
What percentage of HCAI are pseudomonas species?
4% of HCAI
Comment on P. aeruginosa and immunocompromised patients
(4)
Pseudomonas increasingly recognised as an opportunistic pathogen
Pseudomonas is common in present in moist environments in hospitals especially in respiratory therapy equipment, Dialysis tubing catheters
It is pathogenic when introduced into areas devoid of normal defences or the immunocompromised
Dysfunctional Immune System
Who is at risk of P. aeruginosa infections due to dysfunctional immune system?
(6)
Neonates
Cystic fibrosis
AIDA
Neutropenia
Complement Deficiency
Hypogammaglobulinemia
Who is at risk of Pseudomonas infections due to disruption of physical barriers?
(5)
Burn injuries
Intravenous IV lines
Urinary catheters
Dialysis catheters
Endotracheal tubes
Pseudomonas infects what areas of the body
Respiratory tract
Ear
GI tract
Urinary tract
Eye
Bones and joints
What infections does Pseudomonas cause in the respiratory tract?
Pneumonia
Cystic fibrosis
What infections does Pseudomonas cause in the ear
Otitis externa
Otitis media
What infections does Pseudomonas cause in the eye
Bacterial keratitis
What infections does Pseudomonas cause in the Bones and joints
Osteomyelitis
What infections does Pseudomonas cause in the GIT?
Diarrhoea, enteritis, enterocolitis
What are the five types of systemic infections that Pseudomonas can cause
Blood stream infections
Secondary pneumonia, bone and joint infections
Endocarditis
CNS
Skin and soft Tissue infections
Comment on the invasiveness of Pseudomonas
(2)
Invasive P.aeruginosa infections are on the increase
MDR strains have fluctuated between 4-9% since 2014
What is the first step in P. aeruginosa infection
Colonisation
Comment on the colonisation of P. aeruginosa
Break in first line defence
Cell associated virulence factors
Comment on the P. aeruginosa in an acute infection
(4)
Virulence factors increased
Protease toxins
Invasion
Tissue damage
Comment on P. aeruginosa in chronic infections
(3)
Persistent pulmonary infection in Cystic Fibrosis
Formation of biofilm
Virulence factors lower
List the cell associated factors that promote colonisation in P. aeruginosa infections
(2)
Pili
Capsule
What virulence factors cause systemic infections in P. aeruginosa?
(2)
Exotoxin A
Endotoxin
What extracellular factors degrade tissue and promote invasion?
(4)
Proteases
Elastases
Phospholipase C
Exotoxin A
Comment on the LPS of P. aeruginosa
There is some structural variability of LPS
It differs between mucoid to nonmucoid transition
What are the two secreted components of P. aeruginosa?
Pyocyanin
Alginate slime
What does pyocyanin do?
(2)
Interferes with the antioxidant defences in the lung
Facilitates oxidative damage to the lung epithelium
What does alginate slime do?
(2)
Matrix of biofilm formation
Impairs cillary function
List the exotoxins and exoenzymes of P. aeruginosa
(4)
Leukocidin
Elastase
Alkaline Protease
Phospholipase C
What does elastase do?
(3)
Destruction of elastin
Cleaves IgG, IgA, Complement
Degrades surfactant proteins A and D
What does alkaline protease do?
Lyses fibrin
What does phospholipase C do?
A class of membrane-associated enzymes that cleave phospholipids
What does leukocidin do?
(2)
A type of cytotoxin or exotoxin
A pore-forming toxin that kills or destroys white blood cells by creating holes in their membranes
Write about exotoxin A
ADP ribosylation
Inactivation of elongation factor 2
Inhibits protein synthesis
Regulated by environmental iron availability
What does exotoxin S do?
It impairs the function of phagocytic cells
What type of secretion system does Pseudomonas aeruginosa employ
The type III secretion system
What four effector proteins make up the type III secretion system of Pseudomonas?
ExoS
ExoT
ExoU
ExoY
What does ExoU do?
Rapid destruction of host cell membranes
Is greater in P. aeruginosa isolated in hospital ICUs and burn units
What does ExoS do
Relevant in patients with CF
Which protein effectors of the type 3 secretion system are mutually exclusive
ExoU and ExoS
What does Pseudomonas produce in chronic infections?
Bacterial biofilms
What biofilm is produced by Pseudomonas
Exopolysaccharide alginate
Produced in vitro and in vivo
What is the function of biofilm
(5)
Its a survival mechanism for bacteria - it’s a form of protection
Protects against:
- host immune cells
- host antibodies
- disinfectant
- antibodies
Describe sessile vs planktonic
(2)
Sessile bacteria grow more slowly and have restricted mobility
Planktonic forms in culture media and have unnatural access to nutrients, they multiply rapidly and are often highly motile
Comment on P. aeruginosa and cystic fibrosis
Infection with P. aeruginosa and development of chronic infection is directly related to the loss of lung fucntion in cystic fibrosis
Comment on biofilms in the health care setting
(3)
Biofilms form on instruments and implants
Equipment (catheters, prosthetic heart valves, prosthetic joints, shunts)
Healthcare setting (water systems and air conditioning units)
How is Pseudomonas infections treated?
(3)
There is increased resistance during therapy
Pseudomonas may acquire resistance during therapy
Dual therapy is recommended to avoid resistance that develops rapidly when single antimicrobials are used
Comment on the dual therapy approach to treating Pseudomonas and give two examples of treatment
(3)
Two agents from different classes should be used
Beta-lactams such as cephalosporin and an aminoglycoside such as tobramycin
Carbapenems such as meropenem with a fluroquinolone such as ciprofloxacin
What mechanisms of antimicrobial resistance does P. aeruginosa have?
(5)
Permeability barrier
Biofilm formation
Resistance plasmids
Efflux pumps
Resistant to disinfectants
Comment on the permeability barrier of the P. aeruginosa
P. aeruginosa is naturally resistant to many antibiotics due to the permeability barrier gram-negative outer membrane
What is the point of biofilm formation
This makes the cells impervious to therapeutic concentrations antibiotics
What is the main method of antimicrobial resistance in P. aeruginosa?
Porins -> pump out the antibiotic
What specimens can be put up for Pseudomonas
Urine
Sputum
Blood
Pus
Psueomonas is usually put up on what media
(5)
Blood agar
Chocolate agar
Moderately selective media - MacConkey media
Selective agar - Cetramide agar
Incubate aerobically at 37 degrees Celsius for 24-48 hours
How does Pseudomonas look on blood agar
(2)
Metallic sheen
Sweet odour
How does Pseudomonas look on MacConkey agar?
Non lactose Fermenter (yellow colonies)
How does Pseudomonas look on cetrimide agar?
Enhanced pigment of pseudomonas aeruginosa => bright green colour produced
How does cetrimide agar work
It enhances the production of Pseudomonas pigments such as pyocyanin and pyoverdine which show a characteristic blue-green and yellow-green colour
How can you classify Pseudomonas aeruginosa based on colonial morphology
Non-mucoid to mucoid transition
What are the results of P. aeruginosa basic characteristic tests
(3)
GNBs
Oxidase positive
Weak catalase positive
+ distinctive morphology e.g. metallic sheen and mucoid colonies
How would you identify Pseudomonas in the lab
(4)
Growth on selective media
Growth at 42 degrees Celsius
Failure to grow at 4 degrees Celsius
Biochemical Identification
Can the Maldi/Vitek be used to identify Pseudomonas?
No as there are issues with the Maldi/Vitek especially for the mucoid strains
