L18: UTI Flashcards
3 things that are a UTI
Pyelonephritis (kidneys and ureters)
Urethritis
Cystitis
In whom are UTIs most common?
Female adults
What causes UTIs in children?
Poor hygiene
Partial blockage
Signs of upper UTI (pyelonephritis)
HIGHER FEVER >101 F
Flank pain
Shaking, chills
N/V
Signs of UTI in a newborn
Fever or hypothermia
Poor feeding
Jaundice
Signs of UTI in an infant
V/D
Poor feeding
Signs of UTI in children
Irritability Eating poorly *Unexplained fever* Loss of bowel control/loose stools Change in urination patterns
URI-cult CLED/EMB
paddles used to make a presumptive identification of the pathogen
EMB
contains bile salts that kill G+
Selective for G-
CLED
allows growth of both G+ and G-
determines ability to ferment lactose
Hallmark UTI pathogens
are G- and ferment lactose
Why are CFU used in diagnosis of UTI?
Many of the pathogens are normal flora, so we need a threshold to indicate overgrowth/infection
Who usually gets urine cultures?
Men and children
A positive urine culture is
5 x 10^4 CFU
A positive urine microscopy is
2-5+ WBCs
15 bacteria
per high powered field in centrifuged urine sample
What else to do for a UTI in men?
prostate exam
Who gets imaging (US/CT/fluoroscope)?
Children
Adults with recurrent infections
Blood in urine
Why do we image children?
50% of infants with UTI have an anatomic abnormality
Most common causative agent of UTI
E Coli
How do you get a candida UTI?
catheterization
What can an adenovirus UTI cause? (rare causative agent)
Hemorrhagic cystitis
E coli morphology
G-
Flagellated
E coli associated with meningitis
Encapsulated K1 stains
Why would you get meningitis from E coli?
It’s rare: following neurosurgical trauma
Which E coli strain causes UTIs?
UPEC: Uropathogenic E coli
UPEC virulence factors
P fimbriae (Pili)
Dr adhesions
alpha and beta hemolysins
+- K (capsular) antigen (biofilms)
Dr adhesions
UPEC
binds to uroepithelial cells and erythrocytes.
form complex structures surrounding bacteria
Why does UPEC cause blood in urine?
alpha and beta hemolysins
when are UPEC more likely to produce K (capsular) antigen?
Upper UTI
Chronic UTI
Cause biofilms
2 Proteus species
P mirabilis
P vulgaris
Proteus which infects the immunocompromised
Proteus vulgaris
Proteus which is community acquired
Proteus mirabilis
“Swarming” on agar
proteus species
when don’t proteus swarm
CLED test inhibits it so you can actually count colonies
Proteus usually are found in
normal flora (intestin) long term care facilities hospitals
Proteus virulence factors
fimbriae promote attachment to uroepithelial cells
induce apoptosis
If proteus spreads
sepsis
Urease
proteus
makes urine alkaline by hydrolyzing urea to ammonia
Increased pH, as caused by urease from proteus
formation of struvite stones (magnesium ammonium phosphate)
proteus gram stain
G-
Staph saprophyticus characteristics
G+ Coagulase negative Novobiocin resistant Lactosamine (adhesin) Not that virulent, normal flora,
Second leading cause of UTI
Staph saprophyticus
Staph saprophyticus usually infects
Female 17-27, sexually active
Honeymoon cystitis
Staph saprophyticus
Why is Staph saprophyticus difficult to diagnose?
Low bacterial numbers, less than 10^5
No exotoxins
Staph saprophyticus
Group B strep (GBS) aka
Strep agalactiae
Gray-white colonies with a narrow zone of beta hemolysis
Strep agalactiae (group B strep)
where is Strep agalactiae (group B strep) normally found?
Vagina
GI tract
Upper respiratory tract
Makes prevention difficult
If a mother has Strep agalactiae (group B strep) colonizaiton of her vagina, will her neonate get it?
50% will
but only 1-2% actually get infected
So who gets Strep agalactiae (group B strep)
Immunodeficient
Strep agalactiae (group B strep) virulence factors
Capsular polysaccharide
Hyaluronidase
Collaginase
Hemolysin
CAMP factor
test for Strep agalactiae (group B strep)
Accentuation of hemolysis due to interaction with staph beta-lysin (s aureus?)
Presumptive tests for diagnosis of Strep agalactiae (group B strep)
DNA probe
group CHO identification is insensitive
