UTIs Flashcards
Major defenses of urinary tract:
- Chemistry of urine- pH, lysosyme, lactoferrin
- Flushing action of voiding- sloughing epithelial cells
- IgA against mucosal bacteria
- Surface protein characteristics of UG tract (differ from GI tract)
Major threats to UG system
- GI tract- most organisms from here
- Hematogenous spread from other organisms
- Abnormal urethra/system: i.e. blockage, congenital abnormality; causing decreased flow
Most common organisms of bacterial UTIs:
- UPEC (80%)
- Staph saprophyticus (especially in sexually active younger women) (10%)
- Klebsiella, Citrobacter, and proteus mirabilis
Most common cause of nosocomial infection?
Catheter-related infections
Most common associations with pyelonephritis and papillary necrosis?
S-Sickle cell anemia
O- obstructive pyelonephritis
D- diabetes mellitus
A- analgesia abuse
What type of scarring is involved in chronic pyelonephritis? How is this diagnostic?
Uneven scarring (equal scarring would not be present in this but other syndromes such as chronic glomerulonephritis)
What are the serotypes of UPEC?
O- polysaccharide sugars in the outer membrane
K- capsule
H- repeating H segments in flagella
Major virulence of UPEC?
- Varies with serotype (O,K, H)
- adherence- P fimbriae, Type 1 fimbriae
- genes associated with resistance to serum bactericidal activity
- increased K antigen production
- toxins/other
How do P fimbriae work?
Bind epithelial cell receptors with P blood antigen (globoseries)
Trigger LPS to increase TLR4 signaling
How do Type 1 fimbriae work?
bind mannose containing host epithelial receptors (uroplakin I and II)
since it is competitive binding, this is inhibited in presence of mannose
Treatment for carbapenem resistant strains?
polymixin B
Treatment for vanco resistant strains?
linezolid
Dx requirements for uncomplicated UTI?
Pyuria (>=10 neutrophils per high power field)
Bacteruria (>10^5 CFU/mL via midstream catch)
Staph vs strep test?
catalase- determine if break H2O2 into H2O and O2
Staph is catalase positive
Differentiating between staph species test?
Coagulase- does it clump?
Aureus is coagulase positive, others are negative
Saprophyticus vs epidermidis test?
Novobiocin- test for resistance (would inhibit bacterial gyrase)
Saprophyticus is resistant, epidermidis is sensitive
E.coli IMViC results:
indole positive and methyl-red positive
Citrobacter IMViC results:
variable indole
MR and citrate positive
Negative VP
Klebsiella IMViC results:
variable MR
Positive: VP and citrate
negative indole
Proteus Mirabolis IMVic results
negative: indole
Positive: MR, citrate
variable VP
Level of regional resistance that TMP-SMX can be used at?
<20% and no previous UTI treatment with TMP-SMX in last three months
Nitrofurantoin MOA
inhibit bacterical acetyl-CoA to interfere with carbohydrate metabolism
excreted renally- contraindicated in renal dz
Is nitrofurantoin safe during pregnancy?
Yes- BUT not during the last 4 weeks (it will cross the placenta and get into breast milk)
TMP-SMX MOA:
blocks folic acid pathway
Quinolone MOA:
inhibit topoisomerase II and IV to promote bacterial DNA cleavage
cannot take with antacids-will chelate drug
