Exam 2 Lecture 16 Flashcards
Pseudomonas gram stain/morphology
Gram negative, rods, frequently flagellated w/ 1 or more polar flagella
Where can you find Pseudomonas?
huge range of environments and climates:
- water, soil, air
- most common organism in clouds/sky
True or false: Pseudomonas includes plant pathogens and commensals as well as soil bugs
True
Pseudomonas are largely _____ ____ and usually do not cause disease in healthy individuals.
opportunistic pathogens
Pseudomonas are frequently encountered as ______ in a clinical laboratory
contaminants
Normally, Pseudomonas are _____ or ______.
commensal or not found in microbiota
In what types of people can Pseudomonas cause infections?
people with weakened immune system (sick, cancer, etc.) or altered microbiota
P. aeruginosa general appearance
long, narrow, Gram negative rods
P. aeruginosa are _____- positive and grow well at __ºC
oxidase; 42
Why is it important to know that P. aeruginosa are oxidase positive?
Allows us to differentiate from Enterobacteriaceae
Which of these factors are uniquely identifying in P. aeruginosa? A. smell B. non-spore forming C. metallic sheen on blood agar D. oxidase-positive E. catalase-positive F. none of these
A, B, C, D
P. aeruginosa smell can be characterized as:
musty grape; corn chips
The metallic sheen produced by P. aeruginosa colonies on blood agar is a result of _____ _____, namely _____.
pigment production; pyocyanin
Why does Pseudomonas produce pyocyanin?
It is a virulence factor - serves as siderophore for iron binding/transport
True or false: pyocyanin fluoresces under UV light
True
P. aeruginosa is known as a “___ ___” because it is found in various locations, such as:
ubiquitous organism; water, soil, plants, animals, sewage, human skin
What are 2 classic diseases in healthy individuals caused by P. aeruginosa?
- Hot tub folliculitis
2. Swimmer’s ear
Hot tub folliculitis characterizations (2)
- superficial infection of hair follicle root
2. inoculation from contaminated water (namely, hot tubs or swimming pools)
True or false: hot tub folliculitis rarely clears on its own and must be treated with IV antibiotics
False (!!)
- usually clears on its own
- can treat with topical antibiotics
Swimmer’s ear characterizations
- aka otitis externa
- superficial infection of external ear canal skin
- inoculation from contaminated water
P. aeruginosa can cause more serious diseases in these types of people: (6)
- sick
- elderly
- immunocompromised
- burn patients
- uncontrolled diabetes
- those with cystic fibrosis
Cystic Fibrosis (CF) is a ____ disease caused by a ____ in ____.
genetic; mutation; CFTR
What is the role of the CFTR protein?
modulates flow of water and chloride ions out of cells into secretions
A mutation in CFTR results in:
inefficient pumping, causing thick, mucinous secretions
Major symptoms of cystic fibrosis
chronic pulmonary infections
CF occurs in about ____ of live births in the ____ population
1/25,000; caucasian
Pathophysiology of CF
thick mucus builds up in airway, colonized by bacteria, chronic infections result, causes progressive lung function decline
CF treatments
- chronic antibiotic therapy to keep bacterial burdens in check
- pulmonary hygiene (exercises + inhalations to loosen mucus so it can be coughed up)
The predominant lung pathogen in CF is _____.
P. aeruginosa
True or false: typically the same infecting P. aeruginosa strain persists in the lung for years or decades and changes over time to become better suited to CF lung environment
True
When organisms are spatially isolated, they can undergo ____ ____ and _____
genetic diversification; specialization
The human lung consists of physically discrete ____
lobes
What did researchers find during their study of P. aeruginosa population structure in CF lungs?
cultured out ~200 P. aeruginosa isolates per geographical region of the lung (~1200 per patient)
True or false: lineages of P. aeruginosa from different regions of the lung generally have the same metabolic profiles and similar antibiotic resistance
False (!!!)
Up to ___ the amount of yearly genetic divergence seen at baseline for P. aerugonisa
600 times
P. aeruginosa virulence factors (5)
- iron sequestration
- exotoxins
- proteases
- biofilm formation *
- mucoid phenotype *
What is a biofilm?
multicellular collection of bacteria which form 3D structure on a surface
What are biofilms held together by, and what is it composed of?
Extracellular matrix; made from secreted polysaccharides > proteins > bacteria debris
What is the predominant form of bacteria in the environment?
biofilm: either mono- or multi-species
True or false: once a biofilm has formed, it’s generally easy to get rid of them
false
Competitive advantages of biofilm (4)
- increased antibiotic resistance
- increased resistance to host mediated killing
- enhanced adherence
- favorable for bacterial persistence
Biofilms are inherently ___ ____
antibiotic resistance
Mechanisms of antibiotic resistance in biofilms
- profound changes in gene expression, can influence metabolism/antibiotic resistance directly
- center core of biofilms are nutrient limited, thus metabolically inactive
Center core of biofilms provides these two things:
- reservoir of dormant cells
2. can re-seed and repopulate the biofilm
Mucoid phenotype virulence factor is caused by:
overproduction of alginate (polysaccharide), makes capsule around bacteria
True or false: persistent P. aeruginosa infections in CF do not usually progress to a mucoid phenotype
false (nearly always)
Why is the alginate capsule a virulence factor? (4)
- structural support for mature biofilms
- enables “micro-metastasis” for biofilms, gives them a head start
- binds some antibiotics
- protects against host response by inhibiting complement/opsonization; decreases phagocytosis and killing
The P.aeruginosa contains ___ of genes, contributing to its ____ and ____ ____ ____.
lots (5500); flexibility; antibiotic resistance potential
genetic differences known as ___ among bacterial strains are ___ than differences among humans
SNPs; greater
True or false: entire genes can be variably present or absent in different bacterial strains from the same species
true
pan-genome definition
comprises both the core and entire accessory genome for the entire species
genes that are always found in that organism are known as:
core genome
genes that are variably found in that organism are known as:
accessory genome
true or false: the pan-genome is not much larger than the genomic content of any single strain
false: much larger
What makes up a big fraction of the P. aeruginosa accessory genome?
antibiotic resistance gemes, metabolic genes, virulence islands
P. aeruginosa is known as an ___ pan-genome
open
