MSC MLT MICROBIOLOGY

1. Urinary Tract Infection
(UTI)
MODERATOR: MRS AVITTA LOBO
PRESENTER : LIVYA WILSON A

2. Human Urinary System

3. Introduction
 Urinary tract infection(UTI) is an infection in any part of urinary system-
kidneys, ureters, bladder and urethra.
 The entire UT is lined by urothelium that is continuous with
the skin
 Most infection involve the lower urinary tract- bladder & urethra
 Flushing action of urine & sloughing of epithelial cells protects the UT
from infection, micro-organisms (bacteria)

4. Definition
 Urinary Tract Infection (UTI) is defined as a disease
caused by microbial invasion of the urinary tract that
extends from the renal cortex of the kidney to the urethral
meatus.
 Bacteriuria : Presence of detectable bacteria in urine.
 Pyuria : Presence of pus cells in urine
 Most common UTIs are those of the bladder (cystitis) &
the renal pelvis or the kidneys (pyelonephritis)

5. Classification of UTI
2 types
Depending upon the anatomical sites involved :
☻ LowerUTI
☻ UpperUTI
Depending upon the source of infection :
☻ Hospital acquired
☻ Community acquiredUTI

7. Epidemology
 UTI are among the most common bacterial infections that need
medical care; accounting for second most common infection
after respiratory tract infections in the community
 In hospitals, they are the most common hospital acquired
infections accounting for 35% of total HAIs

8. Predisposing factors
1. Prevalence: About 10% of humans develop UTI in
some part of their life.
2. Gender: Predominantly a disease of females; due
to the anatomical structure of female urogenital
system
• short urethra
• close proximity of urethral meatus to anus

9. 3. Age: Incidence increases with age.
• During 1st year of life  2% in both females and males.
• After that, the incidence decreases in males until old age where they again
show an increased prevalence because of the prostate enlargement which
interferes with emptying of the bladder.
• In females, the incidence keeps increasing after 1st year of life.
During 5- 17 years - 1-3%.
In adult life -10- 20%.

10. 4. Pregnancy:
• Anatomical and hormonal changes in pregnancy favor development of UTIs.
• Most females develop asymptomatic bacteriuria during pregnancy.
• Can lead to serious infections in both mother and fetus.
5. Structural and functional abnormality:
• May cause obstruction to the urine flow and urinary stasis; which predisposes
to infection.
• Structural obstruction: E.g. urethral stricture, renal and ureteric stones,
prostate enlargement, tumors, renal transplants, etc.
• Functional obstruction: E.g. neurogenic bladder due to spinal cord injury or
multiple sclerosis.

11. 6. Bacterial virulence: expression of pili helps in bacterial adhesion to
uroepithelium.
7. Vesico-ureteric reflux: If the normal valve-like mechanism at the vesico-
ureteric junction is weakened, it allows urine from bladder up into ureters
and sometimes into the renal pelvis.
8. Genetic factors: Genetically determined receptors present on uroepithelial
cells may help in bacterial attachment.

12. Etiology
 Escherichia coli (uropathogenic E.coli) – most common cause
 Endogenous flora such as gram negative bacilli (E.coli, Klebsiella, Proteus)
& enterococci are important agents
 Agents of hospital acquired UTIs commonly are multidrug resistant and
also staphylococci, Pseudomonas, Acinetobacter are also increasingly
reported
 Among fungi, Candida albicans is a frequent cause of UTI

14. Pathogenesis
2 routes: ascending and descending
Ascending Route
• Most common route

15. Descending Route
• Invasion of renal parenchyma through hematogenous
seedling of the pathogen, as a consequence of
bacteremia.
• Accounts for 5% of total UTIs.

17. Host Defense Mechanisms
Play an important role in prevention of UTI.
(I) Factors related to urine
(II) Activation of host's mucosal immunity by the pathogens

18. Clinlcal Manifestations
Various forms:
I. Asymptomatic bacteriuria
2. Lower UTI: Cystitis and acute urethral syndrome
3. Upper UTI (pyelonephritis)

19. Asymptomatic Bacteriuria
• Isolation of specified quantitative count of bacteria in
an appropriately collected urine specimen, obtained from
a person without symptoms of UTI.
• More common in females
• Incidence increases with age ( I% among school girls to
more than 20% in old age).

20. Clinical Significance
In certain group of people routine screening and
treatment for asymptomatic UTI is highly recommended:
 pregnant women
 People undergoing prostatic surgery or any urologic procedure where bleeding
is anticipated.
Neither screening for or treatment is needed in:
 non-pregnant women
 pre-menopausal women
 old age
 catheterized patient
 patients with spinal injury

21. Cystitis (Infection of Bladder)
Characterized by localized symptoms such as:
• Dysuria (pain while micrurition), frequency, urgency, and
supra-pubic tenderness (over the bladder area).
• Urine becomes cloudy, with bad odor, and in some cases
grossly bloody (hematuria).
• Not associated systemic manifestation.

22. Acute Urethral Syndrome
Seen in young sexually active females, characterized by:
• Presence of classical symptoms of lower UTI as
described for cystitis
• Low bacterial count ( 102 to 105CFU/mL)
• Pyuria
• Agents: Most are due to usual agents, few cases may be
caused by gonococcus, Chlamydia, herpes simplex virus, etc.

23. Upper UTI or Pyelonephritis
• Inflammation of kidney parenchyma, calyces and the
renal pelvis i.e. the part of ureter present inside the kidney.
• Associated with:
 systemic manifestations  fever, flank pain, vomiting.
 Lower tract symptoms  frequency, urgency and dysuria.

24. Laboratory Diagnosis
Specimen collection:
In a wide mouthed screw capped sterile container
1. midstream urine
2. suprapubic aspiration from bladder
3. in catheterized patients  urine aspirated from the catheter rube after clamping
distally and disinfecting, but never collected from urine bag
Transport:
• Processed immediately
• If delay  refrigerated/ stored by adding boric acid

25. Direct examination:
 Microscopy : uncentrifugated sample – examined by direct
microscopy for pus cells and bacteria
Screening tests
• Wet mount examination  to demonstrate the pus cells
• Leukocyte esterase test  to detect the esterase enzyme liberated by
leukocytes
• Catalase test 
• to detect catalase producing bacteria

27. • Presence of catalase evidenced by frothing on addition of hydrogen
peroxide indicates bacteriuria
• Positive result obtained in hematuria
• Griess nitrite test
• to detect nitrite reducing bacteria based on the presence of nitrite in
urine. That indicates the presence of nitrite reducing bacteria in
urine
• Gram’s staining

28.  Triphenyltetrazolium chloride (TTC)
 Based on the production of pink red precipitate in the reagent caused by respiratory
activity of growing bacteria
 Glucose test paper
 Based on utilisation of minute amounts of glucose present in normal urine by bacteria
causing infection
 Dip slide culture
 Agar coated slides are dipped in urine – incubated and growth estimated by colony
counting or by colour change of indicator

29. Culture:
 MacConkey agar and blood agar
 CLED (cysteine lactose electrolyte deficient) agar
• A count of ≥105 colony forming units (CFU)/mL of urine is
considered as significant  indicates infection (referred to as
'significant bacteriuria')
• Counts between 10⁴/ ml & 10⁵/ml – doubtful significance
• Quantitative culture such as pour plate method is carried out to
count the number of colonies

30. Count less than this are considered as significant if :
the patient is prior antibiotic
there is obstruction in the urinary tract
a fungal infection
if pyelonephritis
specimen collected by suprapubic aspiration

32.  CYSTEIN LACTOSE ELECTROLYTE-DEFICIENT AGAR
 Mix the urine(freshly collected clean-catch specimen) by rotating the
container.
 Using a sterile calibrated wire loop e.g. one that holds 1/500 ml,
inoculate a loopful of urine on a quarter plate of CLED agar, if microscopy
shows many bacteria, use a half plate of medium.
 Incubate the plate aerobically at 35-37 degree overnight

33. Antibody coated bacteria test:
• To differentiate upper and lower UTI
• If culture is suggestive of infection
• If rapid result needed &direct microscopy suggests
significant pyuria- a primary susceptibility test with urine
itself is done to permit initiation of early specific antibiotic
treatment

34. Treatment
• Based on antimicrobial susceptibility testing report.
• Quinolones, nitrofurantoin, cephalosporins, and
aminoglycosides are among the preferred drugs