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
T or F. Nitrofurantoin and B-lactams do not reach reliable concentrations in men
T. Not the best for cystitis
What things predispose toward pyelonephritis?
Kidney stones. Conversely, Urease-positive bacteria can also lead to production of struvite stones
Recurrent pts should be evaluated for stones
What are some causes of complicated pyelonephritis?
Abscesses, emphysematous pyelonephritis, papillary necrosis
What is emphysematous pyelonephritis (EPN)?
A severe infection of the renal parenchyma that causes gas accumulation in the tissues.
often has a fulminating course, and can be fatal if not recognized and treated promptly.
Patient pop for EPN?
Common in persons with diabetes (in one study, 80% of pts were diabetics),
What are the symptoms of pyelonephritis?
May or may not include symptoms of cystitis
Fever (>38C), Chills
Flank pain
Costovertebral angle tenderness
Nausea/vomiting
DDx for pyelonephritis like presentation?
- Pelvic inflammatory disease
- Kidney stones
Pyelonephritis that presents with hematuria is most likely caused by what?
Staph aureus
How is pyelonephritis diagnosed?
Urinalysis and culture required
Presence of white blood cell casts indicates upper urinary tract infection
Imaging is not usually needed for acute uncomplicated pyelonephritis
Recurrent pyelonephritis may require CT imaging for kidney stones
Treatment options for pyelonephritis
- Fluoroquinolones
- TMP-SMX
- 3rd generation cephalosporins
ESBL strain causing pyelonephritis should be treated with what?
carbapenem
What drugs are not effective in pyelonephritis?
Avoid nitrofurantoin and fosfomycin because of inadequate renal tissue concentration
What are the common causes of prostatitis in young adults?
Neisseria gonorrhoeae and Chlamydia trachomatis
What are the common causes of prostatitis in elderly patients?
E. coli and other enteric bacteria
What are the common causes of prostatitis in due to hematologic seeding?
Staph aureus
Presentation of acute prostatitis
Fever, dysuria, frequent urination, severe pain upon prostate palpation
Pts may be very ill, even present with sepsis
Presentation of chronic prostatitis
Dysuria, frequency, urinary hesitancy, pelvic discomfort
How is prostatitis diagnosed?
Digital rectal exam to reveal tender prostate; urine or blood culture may be negative
How is prostatitis treated?
Fluoroquinolones or TMP-SMX – achieve high levels in prostate
What causes asymptomatic bacteriuria?
Results from colonization of the bladder
How is asymptomatic bacteriuria diagnosed?
Presence of pyuria is insufficient for diagnosis – about 50% will lack
Instead, diagnosed by quantitative urinalysis:
Female: 2 consecutive clean catches of voided urine of >105 CFU/mL of a single organism
Male: 1 clean catch of voided urine of >105 CFU/mL of a single organism
Catheter: 1 urine specimen > 102 CFU/mL of a single organism
In young healthy women, what does asymptomatic bacteriuria correlate with?
sexual activity
Rarely lasts longer than a few weeks
What are risk factors for asymptomatic bacteriuria?
- Diabetic women
- Neurologic/anatomic abnormalities
- Indwelling Foley catheters
How is asymptomatic bacteriuria treated?
No need for screening or treating asymptomatic bacteriuria in most populations.
note that bacteria that causes asymptomatic cystitis tend to be less virulent, and have less capacity for hemolysis and pilus expression
What populations with asymptomatic bacteriuria should be treated?
- Pregnant women
- Renal transplant pts (first 3 months following surgery)
- Urologic surgery pts where mucosal bleeding is anticipated (eg, prostate resection)
What types of contraceptives are linked with increased risk of UTI recurrence?
Oral contraceptives are the least, while spermicidal foam and condom use and diaphragm-spermicide use are all correlated with increased recurrence of infection
Why are spermicidal foams and gels associated with increased UTI risk?
lowers the vaginal pH (changes the microflora of the vagina)
Why is diaphragm-spermicide use associated with increased UTI risk?
alters the angle of the urethra and the money-shot
Increased UTI with age is associated with what?
lower estrogen levels
T or F. Bacturia is worse in pregnant women compared to the general population
T. And ~25% progress to pyelonephritis so it’s important to treat
What can pyelonephritis in pregnancy lead to?
- premature labor
- fetal loss
- etc.
What are the antibiotics that become most cocnentrated in the kidney (and therefore are good) in pyelonephritis?
- Aminoglycosides (good for GNR)
- Fluoroquinolones (lots of AEs)
- Sulfas
What is the receptor for type I fimbriae for adhesion of UPEC in the bladder
mannose
What is the receptor for P fimbriae for adhesion of UPEC in the bladder
globoserin and glycolipid. P receptors are only in the kidney pelvis
T or F. UPEC with larger capsules are more virulent
T. Prevents phagocytosis
Why do UEPC have a-haemolysin?
It causes lysis of red cells that releases iron which the bacteria can sequester via siderophores for growth
What is the best physiological defense against UT bacterial colonization
Urine flow. Washes everything out and promotes epithelial cell turnover
lack of flow allows growth and quorum-sensing
What are some complications of UTIs?
- gram negative sepsis
- intrarenal or extrarenal abscess
- chronic renal insufficiency
- recurrent infection
UTIs promote the formation of ___ renal calculi
Struvite
T or F. Males are typically treated for UTIs longer than women
T. 1 week (because prostatitis problems) vs 1-3 days in women due to anatomical differences
Asymptomatic bacteriuria is common in what population?
Elderly, usually don’t treat
What bugs tend to cause hemorrhagic cystitis in immunocompromised patients?
Adenovirus
BK virus
CMV
Why is resistance to nitrofurantoin so low?
the drug has multiple targets
But it has to be activated endogenously so efflux pumps and lack of activation can occur
