MICR_041213 Gramneg Flashcards
When does an opportunistic infection present itself?
immunocompromised patients
What is characteristic of the pathogens that cause opportunistic infections? (2)
1) many carry antibiotic resistance genes, 2) many form biofilm
What is a nosocomial infection?
hospital-acquired infection
What is biofilm?
dense microbial communities surrounded by an extracellular matrix
T/F biofilm bacteria have increased resistance to anti-microbial agents compared to others.
True.
What is quorum sensing?
mechanism by which bacteria coordinate certain behaviors (ie induction of virulence factors) based on the local density of the bacterial population; occurs via signaling molecules
What type of infections/diseases can E. coli cause? (4) Which of these are caused by commensal e. coli? Specialized e. coli?
SPECIALIZED STRAINS: GI infections, COMMENSAL STRAINS: UTI, bacteremia, meningitis
What is UPEC?
uropathogenic e. coli
What does UPEC cause?
95% of all non-hospital acquired UTIs
What two infections does UPEC cause?
cystitis and pyelonephritis
What is cystitis?
inflammation of the bladder; caused by UPEC
What are some symptoms of cystitis?
dysuria (burning during urination), frequency, urgency, suprapubic tenderness
What is pylenophritis?
UTI that has spread to the kidneys; caused by UPEC
What are some symptoms of pylenonephritis?
dysuria (burning during urination), frequency, urgency, flank pain/tenderness, fever
What is the virulence factors of UPEC? (6)
1) adhesins (pili/fimbral vs non-fimbrial), 2) biofilm, 3) LPS, 4) capsule, 5) exotoxins (hemolysins), 6) motility
What type of virulence factors of UPEC cause cystitis?
FIMBRIAL/PILI: P, Prs, Type I, S. NONFIMBRIAL ADHESIN: Dr.
What type of virulence factors of UPEC cause pylenonephritis?
P pili and F adhesin
How can you determine if an organism expresses a mannose sensitive pili?
Use a hemagglutination test
What does it mean to be a mannose sensitive UPEC?
adhesion of UPEC is BLOCKED by mannosides on uroepithelial cells.
What does it mean to be a mannose resistant UPEC?
adhesion of UPEC is NOT BLOCKED by mannosides on uroepithelial cells.
What are the normal routes of entry that enable e. coli to cause bacteremia?
UTI (when urinary flow is obstructed), catheters, intestinal infections (less frequent)
What are the virulence factors involved in e. coli-induced bacteremia?
K1 capsule, endotoxin (LPS)
How does the K1 capsule confer pathogenicity in e. coli?
it convers anti-phagocytic properties and serum resistance (allows it to evade phagocytosis)
What is serum resistance? What e. coli properties confer this type of resistance?
because e. coli are often surrounded by capsules, they are not recognized by our immune system and can therefore proliferate in the blood, causing bacteremia. This is due to K1 capsule.
What is neonatal meningitis? What causes it? How is it contracted?
caused by K1 capsule - the e. coli colonizes newborns within hours via VERTICAL TRANSMISSION from mother/nursery staff to baby
What are the virulence factors involved in e. coli-induced neonatal meningitis?
K1 capsule, siderophores, hemolysin
What is pseudomonas aeruginosa frequently associated with?
burns, catheters, implanted devices, eye wounds, immunocompromised patients, cystic fibrosis, COPD
What is the biochemical profile of pseudomonas aeruginosa?
obligate aerobe (in lab only)
What happens if a patient with cystic fibrosis acquires a pseudomonas aeruginosa infection?
chronic pseudomonas aeruginosa infection that can not be cleared by any anti-microbial therapies due to biofilm
What are some virulence factors of pseudomonas aeruginosa?
biofilm, endotoxin (LPS), exotoxins (elastase, phospholipase, ExoA, pyocyanin), T3SS system
What is pyocyanin?
exotoxin/virulence factor secreted by pseudomonas aeruginosa, which generates ROS
What is exoA?
exotoxin/virulence factor secreted by pseudomonas aeruginosa, which BLOCKS PROTEIN SYNTHESIS
What is exoS/T?
exotoxin/virulence factor secreted by pseudomonas aeruginosa, which modifies host cell regulatory proteins
What is exoU?
exotoxin/virulence factor secreted by pseudomonas aeruginosa, which has phospholipase activity inside the cell
What does klebsiella pneumoniae cause?
1˚ pneumonia (when there is an underlying problem alcoholism, diabetes, lung dz), UTIs, wound infections, bacteremia, meningitis, diarrhea
What are the virulence factors of klebsiella pneumoniae?
capsule - which reduces phagocytosis and complement susceptiblity
What is the morphology of the colony of the klebsiella pneumoniae?
mucoid colony morphology; due to capsule
Where is enterobacter cloacae normally found?
gut - it’s part of the normal flora (part of the enterobacteriaceae family)
Infections with enterobacter cloacae are associated with these injuries:
burns, wounds, respiratory infections, urinary infections, use of antibiotics
What is the bacterium that is frequently accounts for many hospital-acquired infections?
enterobacter cloacae
What is serratia marcesens normally found?
in the environment (part of the enterobacteriaceae family)
What is unique about serratia marcesens? (think physical characteristics)
it produces prodigiosins, which gives it its characteristic red color
Infections with serratia marcesens are associated with these injuries:
use of broad-spectrum antibiotics, instrumentation (tracheostomy, respirator), heroin addicts, septic arthritis
What are the virulence factors of serratia marcesens?
fimbriae, proteases, siderophores, flagella (“swarming” motility)
Where does serratia marcesens usually colonize?
Respiratory and Urinary Tract; less likely to colonize GI tract
What is proteus vulgaris/proteus mirabilis?
frequent cause of UTIs
What are the virulence determinants of proteus vulgaris/proteus mirabilis? (2)
flagella (“swarming” motility) and urease
Why is urease production importance in the pathogenicity of proteus vulgaris/proteus mirabilis?
it converts urea into ammonia, which increases the pH/alkalinity of the urine, leading to an increase in chronic UTI
Where is acinetobacteria normally found?
opportunistic infection in hospitalized patients, often associated with use of indwelling medical devices (IVs, grafts)
What are the virulence factors of acinetobacteria?
capsule, adhesins, proteolytic and lipolytic enzymes
What is characteristic of acinetobacteria that cause opportunistic infections?
multi-drug resistant strains are increasing
How can you diagnose gram (-) pathogens? (3)
colony morphology, selective medium, and biochemical tests.
Which gram (-) pathogens are facultative anaerobes?
1) proteus mirabilis, 2) e. coli, 3) enterobacter cloacae, 4) klebsiella pneumonia, 3) serratia marcesens (THINK: facultative anaerobe PEEKS out every once in a while for air)
Which two gram (-) pathogens are aerobes?
1) acinetobacteria, 2) pseudomonas aeruginosa (THINK: aerobes Prefer Air)
Which 3 gram (-) pathogens are lactose fermenters?
1) e. coli, 2) klebsiella pneumonia, 3) enterobacter cloacae
