Lecture 4 Flashcards
Features of enterobacteria?
Enterobacteria are gram-negative, rod-shaped, facultative anaerobic bacteria that ferment glucose, are catalase-positive, and oxidase-negative. They have a layer of LPS on their outer membrane which is made up of O antigen and lipid A.
Examples of enterobacteria
Examples of Enterobacteria include E.coli, salmonella, shigella, and klebsiella
What is the significance of the O antigen in Enterobacteria?
The O-antigen extends out of the membrane surface, and the body forms an immune response against the O-antigen. Enterobacteria have a capsule with a K antigen, flagella with an H antigen, and fimbriae with type 1 protein and p-type protein
What is the significance of lipid A in Enterobacteria?
Lipid A is highly toxic, and cells need to be treated carefully so more lipid A is not released upon cell lysis. Antibiotics have to be chemically modified to penetrate the hydrophilic membrane of Enterobacteria.
What diseases are associated with Enterobacteria?
Enterobacteria are associated with UTI, gastroenteritis, and neonatal meningitis.
What is the most common bacteria that causes UTI?
uropathogenic E.coli.
What are the two major syndromes of the clinical presentation of UTI?
The two major syndromes of the clinical presentation of UTI are: lower urinary tract infected -Cystitis, pain, frequency of urination, painful urination, very rarely fever, turbid urine.
Kidney infected/ pyelonephritis- Back pain, fever, much more serious.
How is UTI diagnosed?
UTI diagnosis is based on examination and culture of a urine sample (urinalysis). Establishing bacteriuria involves examining the urine sample for cloudiness, pus, blood, direct microscopic examination, and quantitative loop method.
Culture media for UTI is blood agar or MacConkey.
Chemical tests using dip sticks coated with specific chemicals and/or substrates can test for UTI.
Why is urine taken mid stream for a sample?
A sample is taken from mid-stream urine because the initial voided urine usually contains organisms present around the urethra.
What is recommended for UTI patients and why (not drug)?
Cranberry is recommended to UTI patients because it contains a lot of mannose and will bind to the urinary tract and prevent the E.coli binding.
What is the pathogenesis of E.coli?
The pathogenesis of E.coli involves:
Periurethral area contamination with a uropathogen from the gut
Bacteria colonization of the urethra and migration to the bladder
Bacteria colonization and invasion of the bladder mediated by pili and adhesin
Neutrophils are infiltrated and bacterial multiplication occurs
Biofilm formation occurs, making bacteria more resistant to host defenses and antibiotics, Epithelial damage occurs by bacterial toxins and proteases
Infection ascends to the kidneys, causing pyelonephritis.
What is the main virulence factor of Klebsiella?
The capsule is the main virulence factor of Klebsiella.
What are the characteristics of Pseudomonas?
Pseudomonas are gram-negative thin bacilli that do not ferment glucose. They produce green/blue pigments and are fluorescent under UV light, pyocyanin (blue), and Pyoverdin (fluorescent).
How are UTIs caused by Pseudomonas aeruginosa acquired?
UTIs caused by Pseudomonas aeruginosa are usually hospital-acquired and related to urinary tract catheterization, instrumentation, or surgery.
