Urinary Tract Infections Flashcards
UTIs are common among otherwise healthy women, and 75-95% are caused by ______
uropathogenic E. coli (UPEC)
What is pyuria?
the presence of white blood cells (or pus) in urine
What is dysuria?
painful urination
What virulence factors do UPEC have that promote infection?
- UPEC possess type 1 pili that allow attachment to the urethral mucosa and epithelia of the bladder
- LPS
- Alpha-hemolysin (molysins or haemolysins are lipids and proteins that cause lysis of red blood cells by destroying their cell membrane)
What virulence factors promote kidney infection by UPEC?
Some UPEC possess a P pilus which allows attachment to kidney cells (70% of pyelonephritic UPEC express P pili)
Type I pili are subject to phase variation, and the on-off expression is coordinated with flagella-mediated swimming up the ureter to the kidney
Uncomplicated cystitis occurs in otherwise healthy women. What things promote complicated cystitis?
Traditionally thought to only form in males
- Pregnant women (suppressed immune system)
- Diabetics (High urine glucose content and defective host immune factors predispose to infection. Hyperglycemia causes neutrophil dysfunction by increasing intracellular calcium levels and interfering with actin and, thus, diapedesis and phagocytosis)
- Hospital-acquired
- Individuals with neurologic (neurogenic bladder) or anatomic problems
-Indwelling catheter
- Immunosuppression
- Multi-drug resistant microbe
When is cystitis more common in men?
Overall, cystitis is far more common in females than males (exception: uncircumcised newborn males up to 3 months of age)
It is known that there is bacterial colonization of the foreskin during the first 6 months of life that may be an important risk factor for the development of UTIs. Colonization decreases after the first 6 months of life, probably because the foreskin often becomes retractable around that age.
Why is diabetes associated with complicated cystitis?
Advanced glycation end products (AGEs) accumulate in diabetics over time. In a mouse model, AGEs enhance the binding of UPEC isolates to the bladder urothelium.
Also, diabetes-associated autonomic neuropathy may develop urinary retention and stasis
What are the symptoms of cystitis?
- Dysuria
- Frequent, urgent urination
- Suprapubic tenderness
- Hematuria
Any one symptom predicts 50% of cases
Dysuria and frequency without vaginal discharge or irritation predicts 90%
Is cystitis associated with fever?
NO (fever indicates pyelonephritis)
What would be the differential with a cystitis like presentation?
Vaginitis (see discharge)
Urethritis
Structural abnormality
Painful bladder syndrome
What is ‘recurrent’ cystitis defined as?
Two or more infections within six months or three or more in one year
What is ‘relapsed’ cystitis defined as?
Considered relapse if it is the SAME microbe and within 2 weeks
How do probiotics deter cystitis?
steric hindrance,
hydrogen peroxide production,
lower pH, and
induce anti-inflammatory cytokines
What microbes are associated with UNcomplicated cystitis?
- E. Coli (GNR)
- Staph saprophyticus (G+)
- Klebsiella, Proteus (GNR)
What microbes are associated with complicated cystitis?
- E. Coli (GNR)
- Ps. aeruginosa (GNR)
- Enterobacter (G+)- Often more common in recurrent b/c they are multi-drug resistant
How is cystitis confirmed by urine microscopy?
Elevated WBCs (>10/uL) – absence predicts something other than UTI
Presence of RBCs (hematuria rare in urethritis or vaginitis)
How is cystitis confirmed by urine dipstick?
- Leukocyte esterase
- Nitrate to nitrite
Interpreting urine dipstick
Pos leukocyte esterase = bacterial
Pos nitrite = GNR
Interpreting dipstick urease results
Pos urease = Proteus or Klebsiella
Neg urease = E coli, Enterococcus
T or F. Urine cultures are always needed to diagnose cystitis?
Only needed for complicated presentation or when resistance is possible
What numbers in a urine culture would be needed to diagnose cystitis?
> 1 x 10^5 CFU/mL from clean catch for females;
> 1 x 10^4 CFU/mL for males
> 1 x 10^2 CFU/ml from catheterization
Rules for urine culture
Urine is sterile, but will become contaminated as it is released
Capture first morning, clean-catch midstream
Start cultures within 1 hr or refrigerate to avoid growth
Culture must be quantitative to confirm infection
Use a 0.001mL calibrated loop to streak a BAP and EMB plate
What if no colonies grow on the EMB plate?
Not a Gram negative infection
If colonies on both plates, likely Gram negative (metallic green= E. Coli)
Count colonies to determine concentration
