Lecture 11 - Legionella, Pseudomonas Flashcards
explain the structure of legionella pneumophilia
is it gram positive or negative?
slender, pleomorphic rods
gram NEGATIVE
what are the requirements for the growth of legionella pneumophila
OBLIGATE aerobe
also needs L-cysteine and ferric ions to grow
where is legionella pneumophila found?
ubiquitous (everywhere) in water and soil
legionella pneumophila has a strong tissue tropism for….
the LUNGS (specifically alveolar macrophages)
how does legionella pneumophila establish an infection
INTRACELLULAR macrophage infection
what is unique about legionella pneumophila
-LPS is less toxic than the LPS from other gram negative bacteria
-recruits ribosomes, mitochondria, and ER components into a phagosomal compartment
as mentioned, legionella pneumophila is unique in that it can recruit ribosomes, mitochondria, and ER components into a phagosomal compartment
what is the term for this compartment
LCV — legionella containing vacuole
how does legionella pneumophila produce this LCV (legionella containing vacuole)
it inhibits phagolysosome fusion and REMAINS in vacuoles where it replicates and produces proteolytic enzymes
does legionella pneumophila have a secretion system?
yes – type IV secretion system (nanosyringe) that delivers over 200 proteins, many of which are unknown
at later stages of infection, what does legionella pneumophila do?
produces pore-forming toxins to escape the LCV (vacuole) and the macrophage
what disease does legionella pneumophila cause?
causes destructive pneumonia
Legionnaires disease — severe form of pneumonia
-necrotizing multifocal pneumonia
does legionella pneumophila spread easily?
no – it rarely spreads outside of the lungs
what is very unique about pseudomonas aeruginosa
it produces colorful pigments
explain the structure of pseudomonas aeruginosa.
is it gram positive or negative?
gram negative
slightly curved, MOTILE rods. usually in PAIRS
explain the requirements needed for pseudomonas aeruginosa growth
aerobic
minimal requirements for its growth
what distinguishes psuedomonas aeruginosa from enterobacteriaceae?
it is cytochrome oxidase POSITIVE
what population does pseudomonas aeruginosa primarily infect? where is it found?
it is primarily opportunistic
infects burn victims
found in moist environments, UBIQUITOUS in nature and hospitals
is pseudomonas aeruginosa encapsulated?
some produce a mucoid capsule – especially in cystic fibrosis
pseudomonas aeruginosa primarily gets in through ______ but it can get in very slightly through _____
mainly through burns and wounds, but very slightly through lungs and eyes
name the adhesins of pseudomonas aeruginosa
flagella, pili, LPS
the mucoid capsule of pseudomonas aeruginosa is primarily composed of what?
alginate
the expression of the mucoid capsule is under what kind of regulation?
gene regulation
name 2 enzymes of pseudomonas aeruginosa and theur functions
elastases and phospholipases
elastases – degrade elastin, complement proteins, IgG and IgA. inhibits neutrophils
phospholipases – degradation of cell membranes
what is the most important virulence factor of pseudomonas aeruginosa?
it has the same mechanism as what other toxin
Exotoxin A (exoA)
diphtheria toxin
name a virulence factor (exclusive to pseudomonas aeruginosa) AND its function
Pyocyanin – induces the formation of toxic oxygen species and stimulates the release of CXCL8
what bacteria has the virulence factor Exoenzyme S? what is itts function?
pseudomonas aeruginosa
acts on actin cytoskeleton and other signaling pathways. induces apoptosis of the host cell
delivered by a TYPE III SECRETION system
explain how pseudomonas aeruginosa can evade the immune system
has elastases that degrade complement proteins, IgA, and IgG, inhibit neutrophils
explain ExoA mechanism of pseudomonas aeruginosa
A subunit inhibits protein synthesis by binding to the ribosome
true or false
most of the time, the immune system can handle a pseudomonas aeruginosa invasion
true
does the actual pseudomonas aeruginosa bacteria get into the cell?
yes – the protective layer is gone in the case of burn victims. also, exoenzyme A and elastases degrade the cell so that the bacteria can then enter
can pseudomonas aeruginosa cause bacteremia?
yes
name another unusal thing about pseudomonas aeruginosa that makes it a clinical concern
it is inherently resistant to multiple antibiotics
what antibiotics are pseudomonas aeruginosa resistant to?
beta lactams (penicillin), cephalosporins, and carbapenems
explain how pseudomonas aeruginosa is resistant to beta lactams
prolific mutations increase their resistance (usually a PORIN PROTEIN mutation)
this mutant porin can block the antibiotic from entering the cell altogether
OR
it also contains beta lactamases that can inactivate beta lactams if they do get in
pseudomonas aeruginosa are opportunistis. thus, when do they present themselves
-in burn victims
-following antibiotic treatment
what kind of clinical diseases can P. aeruginosa cause (name 5 things)
LEADING COMPLICATION IN CYSTIC FIBROSIS
pulmonary infections
skin and soft tissue infections
bacteremia
endocarditis
what does HAP stand for?
what bacteria is this an issue?
hospital acquired pneumonia
p. aeruginosa
commonly the source is respiratory equipment. patients with lung disease are highly susceptible
the pulmonary infections caused by P. aeruginosa are primarily infecting the ____ respiratory tract and can range from ____ to _____
lower
asymptomatic to necrotizing bronchopneumonia
name 3 skin and soft tissue infections caused by p. aeruginosa
wounds (burns)
ear and eye infections (contacts)
UTIs – catheters
explain in detail how P. aeruginosa complicates things in cystic fibrosis patients
the bacteria adsorbs to the substratum of the lungs. some come off but most stay bound there. through quorum sensing, they begin alginate and exopolymer production to form MUCUS. this coats the lungs and O2 cannot get through.
the bacteria continue replicating in this mucus. the patient coughs up very thick amounts of this mucus
