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Chapter27.pptx
1. CHAPTER 27
URINARY TRACT
INFECTIONS
Part III
Microbiology as Applied to Infectious
Diseases
Universities Press
3-6-747/1/A & 3-6-754/1, Himayatnagar
Hyderabad 500 029 (A.P.), India
Email: info@universitiespress.com
marketing@universitiespress.com
Phone: 040-2766 5446/5447
2. Dr Sonal Saxena, MD
Director Professor and Head of the Department of Microbiology
Maulana Azad Medical College,
New Delhi
and
Dr Amala A Andrews, MD
Maulana Azad Medical College,
New Delhi
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3. INTRODUCTION
Urinary tract infections (UTIs) affects all age groups
Most common UTIs are those of the bladder (cystitis) and the renal
pelvis or the kidneys (pyelonephritis)
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4. TYPES OF UTI
Anatomically classified as
Upper UTI: Involves the kidney or ureter
Acute pyelitis—infection of the pelvis of the kidney
Acute pyelonephritis—infection of the parenchyma of the
kidney
Lower UTI: Involves infection from the urinary bladder
downwards
Urethritis—infection of the urethra
Acute urethral syndrome (in women, it is often caused by
Chlamydia)
Cystitis—infection of the urinary bladder
Prostatitis—infection of the prostate
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5. TYPES OF UTI
Based on how it is acquired, UTI may be classified
as
Community-acquired
Hospital-acquired (Chapter 11)
UTI can present as :
Acute UTI
Chronic UTI
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6. PREDISPOSING FACTORS FOR UTIs
Age: The incidence of UTI increases with age
Gender: Young and sexually active females are specifically prone to the infection
Pregnancy: Increases the risk of UTIs
Structural and functional abnormalities of the urinary tract: Increased risk of UTI
Metabolic factors: Diabetes mellitus increases the risk of UTIs
Interventions: Instrumentation including catheterization and any surgical procedure may
result in a UTI
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7. PATHOGENESIS
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Bacteria ascend from the anterior urethra through the column of
urine
If there is stasis of the urine either in the bladder or ureters due to
neurogenic or mechanical causes, the microorganisms colonise
and establish infection
Hematogenous spread to the urinary tract occurs in less than 2%
of cases
Factors influencing establishment of infection
•Host factors (gender, age and familial predisposition)
•Microorganism (presence of type 1 pili [fimbriae]) or adhesins, e.g.,
uropathogenic E. coli
•Environmental factors (vaginal colonisers, pH, anatomic and functional
abnormalities...)
9. CLINICAL FEATURES
Asymptomatic bacteriuria
Symptomatic UTI: The common symptoms include urgency and frequency of micturition
associated with discomfort or pain
Cystitis(lower UTI): Dysuria, fever with chills and frequency
Pyelonephritis or pyelitis (upper UTI): Flank or loin pain, tenderness, high fever and rigor
Infants and children with UTI: Fever, vomiting, diarrhea and poor feeding
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11. SPECIMEN COLLECTION
Fig. 27.2 Types of urine samples to be collected
(MSU—midstream urine; CSU—catheter
sample of urine; EMU—early morning urine)
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12. TRANSPORT
At room temperature within half an hour or refrigerated
at 4°C for up to four hours
Beyond this time, such a sample should not be
processed for bacterial culture
If delay expected, a special container with 1.8% boric
acid is provided, in which urine, which can be kept at
room temperature for up to 24 hours
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Microscopy
An uncentrifuged sample is examined by direct microscopy for pus cells and bacteria.
presence of pus cells and bacteria in large numbers bacterial infection of the urinary tact
Screening
For the presumptive diagnosis of significant bacteriuria
Dipstick tests
i) Griess nitrite test: Presence of nitrite indicates the presence of nitrite-reducing bacteria in
urine.
ii) Leukocyte esterase test: Positive dipstick test helps in diagnosing cystitis
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iii) Catalase test: positive in bacteriuria and hematuria
iv) Triphenyl tetrazolium chloride (TTC) test: positive indicates presence of bacteria
v) Gram stain
vi) Glucose test paper tests
vii) Dip slide culture
None of the screening methods is as sensitive or reliable as culture
15. CULTURE
Quantitative culture provides an estimate of the total number of bacteria in 1 mL of
urine
Pour plate method
Semi-quantitative culturing is done on blood agar or MacConkey agar with a
standard calibrated loop
A colony count of 105/mL is considered significant.
Counts between 104/mL and 105/mL are of uncertain significance.
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Counts less than this are considered significant if:
The patient is already on antibiotics
There is an obstruction in the urinary tract
A fungal infection is present
Pyelonephritis is present
The specimen has been collected by suprapubic aspiration
Fig. 27.3 Semi-quantitative culture of
urine using a calibrated inoculation
loop
CULTURE
17. If ≥3 types of organisms are grown, these are considered as
contaminants, which may have been introduced into the urine
sample from the perineal region or skin or external urethral
meatus due to improper collection
Detection of antibody-coated bacteria differentiates upper UTI
(involvement of the kidney) from lower UTI
Upper UTI results in antibody response, which allows the
antibody to coat the microorganism
Can be detected in the urine by immunofluorescence using
antihuman immunoglobulin tagged to a fluorescent dye
Antibiotic sensitivity testing is done
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CULTURE
18. TREATMENT
Community-onset UTI can be treated with
ciprofloxacin and nitrofurantoin (for out-patients)
For complicated UTI and those with renal involvement,
a higher antibiotic like third-generation cephalosporin or
ceftriaxone may be given
In case of hospital-acquired UTI and/or catheter-
associated UTI, carbapenems or
piperacillin/tazobactam may be given
Prescribe appropriate antibiotics only after a sensitivity
report becomes available.
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