Urinary Tract Infection

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1
Definition
• Lodgment and multiplication of bacteria in
the urinary tract from pelvis to bladder
• Specific infections like MTB excluded
• Renal and urethral infections excluded
2
Urinary Tract
Only lower part of urethra has a
resident bacterial flora
Rest of the urinary tract is normally
sterile
Flushing effect of urine flow
Local phagocytic activity
Mucosal IgA and secretions from
prostatic and urethral glands
3
Definitions
Bacteriuria
Presence of bacteria in the urine
Pyuria
Presence of WBCs in the urine
Cystitis
UTI associated with superficial mucosa o f
bladder
Pyelonephritis
UTI of renal parenchyma and or collection system
Uncomplicated UTI
Infection involving structurally and functionally
normal urinary tract (simple UTI)
Complicated UTI
Infection involving structurally and functionally
abnormal urinary tract
Urethritis
Infection of the urethra
4
Concept of Significant
Bacteriuria
•
Up to 104/ml considered normal i.e.
Insignificant
•
105/ml and above considered to be
Significant
•
Concept valid only for voided
specimen of urine
•
Exceptions - slow growing
organisms, patient on antibiotic
therapy, diuretic therapy
5
Predisposing factors for UTI
Shortness of female urethra
Sexual intercourse (honeymoon cystitis)
Pregnancy & Contraceptive devices
Prostatic hypertrophy
Neurogenic bladder
Abnormal kidney &
bladder or stones
Catheterization or surgical
instrumentation
6
Clinical manifestations
Urgency
Frequency
Dysuria
Pain & tenderness - above the
symphysis pubis (lower), loin (upper)
Fever
Bed wettings in children
7
Importance of Urine RE
•
•
•
•
•
Presence of proteins
Presence of pus cells
Presence of bacteria
Correlation with growth obtained
Suspicion of anaerobic bacterial infection
8
Bacteria Commonly Encountered
in UTI
•
•
•
•
•
•
•
E. Coli
Proteus
Klebsiella
Pseudomonas
Citrobacter
Staph aureus
Anaerobes particularly
bacteroides
• Enterococcus ie Group
D streptococci.
9
Pathogenicity
By ascending route
following colonization
or periurethral area by
enteric organisms
Rarely
hematogenous
Entry of
microorganisms
Some strains of E coli
(uropathogens) possess pili
interacting with galactose
containing receptor sites on
epithelial cell surfaces
Proteus sp. possess
urease, which raises the pH
and cause precipitation of
phosphate crystals leading
to stone formations
Ability to adhere urinary
epithelial cells
10
Collection of Specimens
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Clean catch mid-stream specimen of urine
Early morning sample preferred
Catheter specimen
Suprapubic aspiration
Differential specimen from two ureters
Instructions to the patients
Early transport to the lab essential
11
Instruction for collection of mid stream urine
Sterile specimen container
Female patients
Spread
labia,
using plain
soap or
antiseptic
wipe front
to back,
dry with
tissues
Begin passing urine
Stop flow in midstream
Pass several ml into pen container
without touching rim
Stop flow before it ends
Recap container
Pass remaining urine into lavatory
Send specimen to laboratory
immediately
(refrigerate if prolonged transport
time)
Male patients
Retract
prepuce,
using plain
soap or
antiseptic
clean glans.
Dry with
tissues.
12
Presumptive Screening Tests
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•
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Griess nitrite test
Catalase test
Triphenyltetrazolium chloride (TTC) test
Microscopic demonstration of bacteria in
smear stained by gram’s method
• Glucose test method
• Dip slide culture method
13
Processing of Specimen
• Uncentrifuged specimen inoculated on
CLED medium
– Cystein, lactose, electrolyte-deficiency medium
• Centrifuged specimen used for microscopic
exam
– Unstained
– Gram stained
14
Lab Diagnosis of UTI
Specimens
Urine
Mid stream urine (MSU)
Catheter specimen urine (CSU)
Supra pubic aspiration (SPA)
Urine transport device (boric acid or refrigerate)
Microscopy
wet mount
Pus cells / hpf
Bacteria / crystals/ casts
Gram stain
GNB/GPC
Urine
Culture
Kass semi-qauntative method
(1 bacterium / field is significant)
Standard loop technique
To know significant bacteriruria
15
Antibiotic Sensitivity Testing
• High potency disks used
• Antibiotics normally active in urine selected
• Antibiotics found in higher concentration in
urine preferred
• Primary sensitivity test frequently used
16
How to suspect anaerobic UTI?
• Extremely foul smelling urine
• Failure to respond to usually useful
antibiotics against aerobes
• Failure to grow bacteria seen in Gram stain
prepared from centrifuged specimen
17
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