Microbiology of UTI's

Question 1

What is the definition of a UTI? what is the difference between a lower and upper UTI?

Answer 1

presence of microorg.s in tract causing an environmental infection

Lower - confined to bladder
Upper - involves ureters +/- kidneys

Question 2

what is the definition of a complicated UTI?

Answer 2

UTI + systemic sepsis or urinary structural abnormality or stones

Question 3

what is:

• bacteruria
• cystitis?

Answer 3

Bacteruria - bacteria in urine (not always a UTI)

cystitis - inflammation of bladder

Question 4

what is the colonisation of the normal urinary tract?

Answer 4

Kidneys/ureter/bladder - sterile

Lower urethra - coliforms/enterococcus

Question 5

Why are women more susceptable to UTI’s? what increases the risk of UTI’s?

Answer 5

Short (5cms) wide urethra that’s in close proximity to the anus

Increased risk if: pregnant, sexual intercourse, catheter, abnormal urinary tract

Question 6

What are the two different routes of UTI?

Answer 6

Ascending or from bloodstream due to bacteraemia/septicaemia

Question 7

what are the 4 different coliforms assoc. with UTI’s?

Answer 7

coliforms = gram -ve bacilli

-e.coli
-klebsiella
-enterobacter sp
-proteus sp
other coliforms

Question 8

What is a UTI due to proteus assoc. with?

Answer 8

stone formation: produces urease that breaks down urea = ammonia = increases the urinary pH = precipates salt

Question 9

What gram -ve bacilli that is not considered a coliform can cause UTI’s? What are UTI’s due to this organism assoc. with?

Answer 9

pseudomonas aeruginosa

• assoc. with catheters and other instrumentation
• resistant to most abiotic except ciprofloxacin

Question 10

What gram positive organisms cause UTIs?

Answer 10

• Enterococcus
• staphylococcus saphrophyticus
• staph aureus

Question 11

Enterococcus:

- what type of organism is this?

Answer 11

Gram positive streptococci that occur as diplococci or in strips
-gamma haemolytic (do not cause haemolysis)

Question 12

Staphylococcus saphrophyticus

• What type of organism is this?
• what demographic of patients does this affect?

Answer 12

coagulase negative staphylococcus

-affects women of child bearing age

Question 13

What are the 7 s/s of UTI?

Answer 13

Dysuria
frequency
nocturia
haematuria
fever
loin pain
rigors

Question 14

what type of urine sample is important when testing for UTI’s in general?

Answer 14

MSSU

Question 15

When would:
-clean catch urine
-bag urine
-catheter specimen
-suprapubic aspiration
be used to collect a urine sample?

Answer 15

Clean catch: babies/elderly

Bag urine: attach a bag to urethral meatus in babies - often contaminated with bowel flora so if positive have to do a suprapubic aspiration to confirm

catheter specimen - aspirate from tube

suprapubic aspiration - babies/young children

Question 16

What is the difference between a boricon container and a sterile universal container when sending urine?

Answer 16

Boricon (red top) has preservative that works for about 24hours

sterile universal container must reach lab within 2 hours

Question 17

What different dipstick urine tests would suggest UTI?

Answer 17

• leukocyte esterase
• nitrites (some bacteria convert nitrates to nitrites)
• protein/blood

Question 18

How does the lab diagnose UTI’s?

Answer 18

-microscopy urine if urgent: look for polymorphs (pus cells), bacteria +/- RBCs

• Culture urine on all samples: look for a significant bacteruria (only UTI if there’s a significant amount colonisation of 1 bacteria)
• if there is a mixed growth probably not significant (doesn’t apply for abnormal tracts)

Question 19

What is kess’s criteria?

Answer 19

applies to women of childbearing age:
>10^5 organisms/ml = significant (probable UTI)
<10^3 organisms/ml = not significant
10^4 organisms/ml = contaminated? infection? repeat

Question 20

What is the empirical treatment for female lower UTI?

Answer 20

Trimethoprim/nitrofurantoin - 3 day course

Question 21

What is the empirical treatment for an uncatheterised male lower UTI?

Answer 21

trimethoprim/nitrofurantoin - 7 day course

Question 22

What is the empirical treatment for complicated UTI/pyelonephritis in the community?

Answer 22

co-amoxiclav or cotrimoxazole - 14days

Question 23

What is the empirical treatment for a complicated UTI/pyelonephritis in the hospital setting?

Answer 23

amoxicillin and gentamicin IV - 3 days
(if allergic penicillin cotrimoxazole instead of amox.)
(cotrimoxazole is IV trimethoprim)

Question 24

Trimethoprim:

• how does it work?
• when to avoid?
• what organisms does it cover?

Answer 24

inhibits folic acid synthesis of bacteria, good conc. in urine and prostate, cheap
-avoid in first trimester pregnancy

Organisms:

• range but not pseudomonas
• most coliforms/s. aureus including MRSA

Question 25

Nitrofurantoin: - when can this only be used and why? - when to avoid - what organisms does it cover?

Answer 25

- Can only be used in lower uncomplicated UTI as only reaches effective conc. in the bladder - avoid in late pregnancy, breast feeding and <3mths babies Organisms: - not proteus/pseudomonas - most coliforms, enterococci, staph. aureus inc MRSA

Question 26

Gentamicin: - how is this given? when is a level taken? - how long can it be prescribed for? - risks? - organisms covered?

Answer 26

Given IV in hospital, 7mg/kg once daily and then measure blood levels 6-14hrs later -prescribe for 3 days only Risks: - avoid in pregnancy - narrow therapeutic index, toxicity causes renal and VIIIth CN damage Organisms: - most coliforms - pseudomonas - staph aureus inc MRSA - not enterococcus

Question 27

Antibiotic resistance in UTI's, lots of organisms are becoming antibiotic resistant - what type of bacteria that causes UTI's are becoming antibiotic resistant? what abiotics are useful in these scenarios?

Answer 27

Extended spectrum B lactamase (ESBL) producing bacteria Useful antibiotics: - temocillin (also used in those who can't take gent.) - pivmecillinam (not recommended in pregnancy)

Question 28

Which abiotic if amox and trimeth. resistant? is this safe in pregnancy?

Answer 28

- Cephelexin - safe in pregnancy - trying to reduce use as high risk recurrant UTIs post-treatment

Question 29

If there is a significant bacteruria with no pus cells and asymptomatic in a non-pregnant patient what is the treatment?

Answer 29

nothing

Question 30

In pregnancy - why are women screened for asymptomatic bacteruria?

Answer 30

All pregnant women are screened at the first antenatal visit and if they are left untreated 20-30% progress to pyelonephritis (which can lead to intra-uterine growth retardation or premature labour)

Question 31

What is the treatment for UTI/asymptomatic bacteruria in pregnancy

Answer 31

1st or 2nd trimester nitrofurantoin MR 100mg bd or 50mg qds. 3rd trimester trimethoprim 200 mg bd (unlicensed). 2nd line (any trimester) cefalexin 500 mg tds or as per sensitivities. Treat for 7 days and sample for test of cure

Question 32

What is abacterial cystitis/urethral syndrome? What are the causes of this?

Answer 32

UTI symptoms bu no significant growth (pus cells might be present) Causes: - early phase UTI - urethral trauma 'honeymoon' - urethritis caused by chlamydia/gonorrhea (alkalising urine may help)

Question 33

When would an antibiotic be considered for a catheterised patient?

Answer 33

-if significant culture and symptoms (otherwise increasingly resistant microorg. will colonise)