UTIs

Question 1

Infections of the urinary tract

Answer 1

One of the commonest bacterial infections
Up to 30% of women have recurrent UTI episodes
Any pathogen has to overcome the normal defenses in the Urinary tract

Question 2

Main defence against UTIs

Answer 2

Flushing by urine

Question 3

Route of infection (DIAGRAM)

Answer 3

Infection usually ascends from the external site up the UT continuum
This can in some cases also lead to involvement of the kidneys
Catheterisation a common route of infection
The female urinogenital tract is particularly vulnerable to infection with fecal bacteria, mainly because the urethra is shorter and nearer to the anus.
But also due to the nature of intercourse…..

Question 4

Definitions of urethritis

Answer 4

Inflammation of urethra

Question 5

Definition cystitis

Answer 5

Inflammation of bladder

Question 6

Definition of dysuria

Answer 6

Painful urination

Question 7

Pyuria

Answer 7

Urine that contains pus

Question 8

Pyelonephritis

Answer 8

Kidney infection, characterised by fever and back pain

Question 9

Host factors - urinary tract (DIAGRAM)

Answer 9

Renal calculi
Ureteric reflex
Tumours in and adjacent to urinary tract
Pregnancy, bladder stones
Neurological problems:
-incomplete bladder empying
-large vol of residual urine
-loss of sphincter control
Prostatic hypertrophy
Short urethra in women
Catherization

Question 10

Bacterial attributes in urinary tract (pathogen factors)

DIAGRAM

Answer 10

Capsular antigens
Hemolysins
Urease
Adhesion to uroepithelium (e.g. P. fimbriae in E.coli)
Introital colonization

Question 11

Diagnosis of UTIs: steps

Answer 11

Sampling of midstream Urine (with care)
-cloudy or clear
-haematuria? (urine might be pink)
-culture on agar plates > 2x105 cells/ml
-traces of protein, leukocytes >10/ml
- > nitrites (NO3- > NO2-)
Pure or mixed growth?
Gram Stain of isolated bacteria or direct staining from urine sample

Question 12

Main culprits: community UTIs

Answer 12

E.coli - gram negative rod
-80%
Proteus mirabilis
-gram negative pleomorphic rod
-swarming motility
Staphylococcus saprophyticus
-gram positive coccus
-particularly common in young women of sexually active age

Question 13

Main culprits: hospital UTIs

Answer 13

Different ratios

Question 14

Which media to isolate UTIs

Answer 14

Cysteine-lactose-electrolyte-deficient (CLED) media
-rich media containing lactose and lacking electrolytes (salt) to repress swarming
Subsequent plating on Macconkey agar if E.coli suspected (although Gram stain informative)
NB: some labs use a variant on CLED containing acid fuchsin (pH indicator) called CLED Andrade indicator media – stains E.coli pink

Question 15

E.Coli colonies

Answer 15

Andrade - pink

Normal plate: large yellow colonies, opaque, centre slightly deeper yellow

Question 16

Proteus colonies

Answer 16

Translucent blue colonies

Question 17

Staph aureus colonies

Answer 17

Deep yellow colonies, uniform in colour

Question 18

Staph coagulase-naegative (saprophyticus) colonies

Answer 18

Pale yellow colonies

Question 19

E.Coli - UPEc

Answer 19

Gram-negative motile bacillus
Also causes GI-infections, but UTIs commonly caused by specific strains of E.coli known as UPEC
These differ at the genome level from enteric strains by having up to 1000 extra genes
Possesses potent adhesins for attachment to epithelium

Question 20

UPEC Pilus adhesins (DIAGRAMS)

Answer 20

Type I pili: binds mannose receptors, common on glycoproteins in uroepithelium
P-fimbriae: binds to globobiose (aD-Gal-(1,4)-aD-Gal)
-linked ceramide host lipids
-often found in pyelonephritis strains

Question 21

Further diagnosis of UPEC

Answer 21

Lactose fermenting strain so will produce pink colonies on MacConkey agar (and CLED andrade)
-E.coli pink
Strain designation by PCR and sequencing

Question 22

GP-level urinary dipsticks

Answer 22

Level of nitrites
-indicative of gram -ve (usually E.coli)
Levels of luekocytes produced
Levels of pH, blood, protein, glucose, ketone etc.

Question 23

Proteus mirabilis

Answer 23

Type of proteus spp.
Fabulous swarmer
-swarming: ability to move over a surface
-proteus can swarm over catheter surfaces
-can cover CLED plates / CLED plate suppresses this action?
More common in older patients
-can cause confusion

Question 24

Proteus mirabilis - virulence factors

Answer 24

Urease: urea» ammonia + CO2, raises pH of urine»> can cause precipitation of minerals to form kidney and bladder stones
-smells really bad
IgA protease- reduces flushing…
Many pili adhesins

Question 25

Staphylococcus saprophyticus

Answer 25

Gram positive- cocci
Haemagglutinin key to attachment to cells
common cause of UTIs in young women
Coagulase negative
Novobiocin resistant
Most common in young women

Question 26

Treatment of UTIs

Answer 26

Swift antibiotic treatment to prevent complications of kidney infection
> 3-day course in women, 7-day in men
Common antibiotics include Nitrofurantoin (1st-line) Ciprofloxacin, penicillins and trimethoprim
Resistance a growing issue, esp. for E. coli (20-30% are Tm resistant)

Question 27

Coagulase positive almost always

Answer 27

Staph aureus

Question 28

Complications leading to UTI - catherisation

Answer 28

Commonly UTIs stem from long term in-dwelling catheters
Usually skin commensals like S. aureus and epidermidis or Pseudomonas spp. (Strict aerobe), Klebsiella and Enterococcus
3-5% > in risk with each day of catheterisation

Question 29

ESKAPE

Answer 29

Enterococcus faecium
Staphylococcus aureus
Klebsiella pneumoniae
Acinetobacter baemannii
Pseudomonas aeruginosa
Enterobacter species
-problematic due to resistance
-hardest to treat, particularly in hospital situations

Question 30

Most common hospital infections

Answer 30

Most common is UTI

Followed by surgical wound infections

Question 31

Treatment: hospital UTIs

Answer 31

Similar to community but may require IV antibiotics
Removal and changing of catheter and bag
Resistant E.coli infections now treated with Plazomicin in USA expected to come to UK soon