Lecture 19 - Opportunistic Infections Flashcards
Frequently encountered opportunistic pathogens 1) 2) 3) 4) 5) 6) 7) 8) 9)
1) E coli
2) Staph aureus
3) Klebsiella pneumoniae
4) Enterococcus
5) Pseudomonas aeruginosa
6) Enterobacter
7) Serratia
8) Proteus
9) Clostridium difficile
Host factors predisposing to opportunistic infection (local) 1) 2) 3) 4) 5)
1) Anatomical defects
2) Surgical, other wounds
3) Burns
4) Catheterisation
5) Foreign bodies
Host factors predisposing to opportunistic infection (systemic) 1) 2) 3) 4) 5) 6) 7) 8) 9)
1) Extremes of age
2) Leukopenia
3) Malignancy
4) Malnutrition
5) Diabetes
6) Liver disease
7) Certain infections
8) Antimicrobial treatment
9) Congenital immune defects
Example of an anatomical defect leading to opportunistic infection
Bladder that won’t empty properly
Leads to stagnation of urine, infection
Bronchial obstruction from a malignancy, smoking
Types of infection 1) 2) 3) 4) 5) 6)
1) Wound infection
2) UTI
3) Intra-abdominal infection
4) Pneumonia
5) Septicaemia
6) Meningitis (especially neonates)
Leukopenia
No white cells
Examples of diseases that immunosuppress
HIV
Acute stage of measles is very immunosuppressive
Type of bacterium that Pseudomonas is
G- rod
Pseudomonas spp 1) 2) 3) 4) 5) 6) 7) 8)
1) G- rod
2) Motile
3) Aerobes or facultative anaerobes
4) Non-fermenting
5) Non-sporing
6) Widespread
7) Low nutritional requirements
8) Pseudomonas aeruginosa produces green pigment
How are Pseudomonas divided into species?
Biochemical tests
How are P aeruginosa normally subtyped for epidemiological studies?
RFLP, MLST (multilocus sequence typing)
Epidemiology of Pseudomonas 1) 2) 3) 4) 5) 6)
1) Widespread in nature, especially in moist environments
2) Transiently colonises skin, GIT, mucous membranes
3) Leading nosocomial pathogen
4) Mostly acquired from the environment
5) Spread in hospitals from hands, fomites
6) Intrinsically resistant to penicillins, readily acquires resistance from other bacteria
Patients most at risk of P aeruginosa infection 1) 2) 3) 4) 5) 6)
1) Burns
2) Febrile neutropenia
3) Pneumonia
4) UTI
5) Sepsis
6) Major problem in CF patients
Superficial P aeruginossa infections
1)
2)
1) Skin: wound infection, otitis externa
2) Eye: Keratitis, corneal ulcer
Deep and systemic P aeruginosa infections
1)
2)
1) Pulmonary: nosocomial pneumonia, chronic infection in CF patients
2) Other: UTI, osteomyelitis, septicaemia, mostly in immunocompromised patients
P aeruginosa properties in biofilms 1) 2) 3) 4) 5) 6) 7)
1) Non-motile
2) Mucoid phenotype - increased capsule
3) More adherent
4) Less invasive
5) Shorter LPS (no O antigen)
6) Slowed growth
7) Increased antimicrobial resistance
P aeruginosa adhesion and invasion 1) 2) 3) 4) 5) 6)
1) Doesn’t invade intact skin unless in very large numbers
2) Adheres weakly to intact epithelium via flagella, lps, pili
3) Neuraminadase assists invasion
4) LPS core binds to CFTR
5) Once adherent, bacteria express biofilm
6) Flagella and LPS bind to TLRs, affect cytokines
What aids the spread of Pseudomonas through the body? 1) 2) 3) 4) 5)
1) Reduced polymorphonucleosites
2) Flagella
3) Exoenzymes
4) Exotoxins
5) LPS-CFTR mediated invasion
Exoenzymes secreted by Pseudomonas 1) 2) 3) 4)
1) Haemolyins
2) Proteases
3) Elastases
4) Phospholipases
Act on pulmonary tissues and surfactant
Extoxins secreted by Pseudomonas
1)
2)
1) Exotoxin A
2) Exoenzyme S and U (ExoS, ExoU)
Effects of CFTR-LPS mediated fusion
Aggravates corneal damage
Agar used to culture Pseudomonas
Cetrimide agar
What is cetrimide agar?
Used to culture P. aeruginosa
Contains cetrimide, a disinfectant
Kills other bacteria, doesn’t worry Pseudomonas
Antimicrobial resistance conferred by biofilm formation
Phenotypic, not genotypic
Why can Pseudomonas and Staph aureus grow in CF lungs?
Not inhibited by high salt content
Bacteria that normally persist in CF lungs
Bacteria with reduced virulence
Why can high salt or sugar inhibit bacterial growth?
Reduces available water content
Most common bacteria in the lungs of young CF patients
Staph aureus and Pseudomonas aeruginosa
Pseudomonas type III secreted proteins
1) Exoenzyme S
2) Exoenzyme T
3) Exoenzyme U
4) Exoenzyme Y
Pseudomonas exoenzyme actions
Act on various host cell targets to interfere with phagocytosis, enhance cytokine produciton
Exotoxin A function
Exactly the same as diphtheriatoxin
Interferes with chain-elongation in ribosomes
Phage-encoded
How does exotoxin A function in exactly the same way as diphtheriatoxin, but doesn’t cause diphtheria?
Same A subunit, different B subunit (binds to different receptors)
LasA, LasB
Proteases in Pseudomonas
Act together as elastases
Effect of Pseudomonas phospholipases
Damages cell membranes, degrades surfactant
