Gram negative opportunistic infections Flashcards
What are nosocomial infections?
Hospital acquired opportunistic infections
Which pathogens are innately resistant to antimicrobials?
Pseudonomas and acinetobacter baumanii
What can E coli cause?
- GI infections (Only specialized pathogenic strains)
- UTIs (commensal E coli)
- Bacteremia (commensal E. Coli)
- Meningitis (commensal E.Coli)
What concentration is indicative of a bacteriurial infection?
10^5 bacteria/ml
What is cystitis?
inflammation of the bladder causing dysuria
What is acute pylenophritis?
urinary tract infection that has reached the kidney. Results in flank pain, fever, and dysuria
What is the important adhesin in E Coli?
P Pili, which can cause pyelonephritis
What is the most common cause of nonhospital acquired UTIs?
E coli
What do P pili bind to?
Gal Gal moiety on human P blood group
If individuals have P1 vs. P2 blood groups, what are they predisposed to developing?
P1 individuals are more likely to develop E Coli UTIs and pyelonephritis
Significance of mannosides in uropathogenic E Coli?
UTI E Coli can bind mannosides on uroepithlial cells. This binding is blocked by mannose.
What does mannose sensitive hemagglutination tell you?
Whether organism expresses mannose sensitive pili. If they do, they will be sensitive to inhibition by mannose and will NOT agglutinate
What is the major cause of bacteremia?
E. Coli
How does E Coli protect itself from serum when causing bacteremia?
Produces K1 capsule, with polysialic acid. This prevents complement binding.
How can E Coli cause meningitis?
During delivery, can be transferred to neonates. Crosses blood brain barrier and survive in the CSF.
What is the most important antigen in the pathogenesis of E Coli meningitis?
Siderophores
What are the acute infections caused by pseudomonas?
burns, eye, wounds, catheters, implants, pneumonia, bacteremia in compromised patients
What is associated with chronic infections of CF patients?
Pseudomonas
What is produced in chronic Pseudomonas infections?
Alginate slime capsule
What toxins Pseudomonas produce?
LPS
elastases, phospholipases
T3SS exotoxins
Name the T3SS exotoxins secreted by pseudomonas and what each does.
ExoA: inhibits protein synthesis
ExoS and ExoT: Exoenzymes that modify host cell regulatory proteins
ExoU: Phospholipase activity within host cell
What characteristic pigment-producing toxin does pseudomonas produce?
Pyocyanin: generates reactive oxygen species
In what metabolic category is pseudomonas?
Obligate aerobe. Although it can also use other substances as electron acceptors to perform metabolic respiration.
What can klebsiella pneumoniae cause?
Primary pneumonia
Red current jelly sputum
UTI
BACTEREMIA AND MENINGITIS
What is the main virulence factor in Klebsiella?
Capsule
Which opportunistic gram negative pathogens are part of the normal gut flora?
Enterobacter cloacae and E Coli and Klebsiella pneumoniae
What can enterobacter cloacae infect?
Pneumonia, UTI
What is characteristic of the serratia marcesens?
bright red/orange color. Often found on shower heads
What are the virulence determinants of seratia marcesens?
proteases, siderophores, flagellar motility
What do Proteus vulgaris and proteus mirabilis cause, pathologically?
UTIs
What are the virulence determinants of proteus’?
flagella, urease production, which converts urea back to ammonia and an alkaline urine
What is acinetobacterbaumanii cause, pathologically?
infection of medical devices, wounds, lungs
Does acinetobacter baumanii ferment?
no
Name the gram negative opportunistic pathogens
E Coli, P aeruginosa, Klebsiella pneumoniae, enterobacter cloacae, serratia marcesens, proteus vulgaris and mirabilis, acinetobacter spp
Which of the gram negative opportunistics are facultative anaerobes?
E coli, Klebsiella pneumonia, serratia marcescens, enterobacter cloacae, proteus mirabilis
Which of the gram negative opportunistics is a nonfermenter?
acinetobacter baumanii and pseudomonas
Which of the gram negative opportunistics are lactose fermenting?
E coli, Klebsiella pneumonia, enterobacter cloacae
Explain what it means if the butt of the kliegler slant turns yellow and what it means if the slant of the kliegler slant turns yellow
If the butt turns yellow, it means that the bug is a glucose fermenter. If the slant turns yellow, it means that the bug is a lactose fermenter
You run a klieger slant and get the following results:
- Butt is yellow
- Slant is red
- No gas
- No H2S production
What pathogen do you suspect?
Shigella or serratia. Because it is a glucose fermenter, does not produce gas OR H2S.
The results of a kliegler slant shows the following:
- butt yellow
- slant is red
- gas is produced
- H2S is produced
What pathogens would you suspect?
Salmonella or proteus
You observe the following kliegler slant:
- Yellow butt
- yellow slant
- Gas production
- No H2S production
Which pathogens would you suspect?
E. Coli, Enterobacter, Klebsiella
You observe a kliegler slant with the following:
- Red butt
- Red slant
- No gas
- No H2S
pseudomonas