Diagnosis and Treatment

Question 1

What situations should cultures be taken in suspected UTI?

Answer 1

Women with mild or limited symptoms for whom dipstick testing in inconclusive

Suspected UTI in men

Suspected acute pyelonephritis

Pregnant women with symptoms, or for screening purposes

After failed antibiotic treatment or persistant symptoms

Recurrent UTI (definned as >2 UTIs wthin 6 months or >3 UTIs/year)

Children suspected UTI

Question 2

When should you not routinely culture urine?

Answer 2

You should NOT routinely culture urine from asymptomatic, non-pregnant patients, wether they have urinary catheters or not

Question 3

How should Mid-stream urine be collected?

Answer 3

Collected from non-catheterised patients, having discarded the first 10-20ml of the stream as its more likely to include organisms that contaminate the anterior urethra.

Urine should be collected into a sterile vessel.
-Should be refrigerated or collected in special containers that contain boric acid.

Question 4

Why should you store urine in a refrigerator or in boric acid?

Answer 4

Urine is a good culture medium so this prevents bacterial overgrowth

Question 5

If there is likely to be a delay in specimen reaching the laboratory what alternative method can you use?

Answer 5

Dipslide

Question 6

What is a dipslide

Answer 6

This is a plastic holder coated in agar which is dipped into the urine immediately after collection.

Any organisms present in the urine are inoculated on to the agar and will grow in quantities proportional to their concentration in the urine at the time of inoculation

Question 7

What is the downside of using a dipslide?

Answer 7

Does not allow microscopy or related studies to be performed on the urine itself

Question 8

How should catheter specimens be obtained?

Answer 8

From the catheter sampling port and not from the collection bag

Question 9

What is the recommended method for urine collection in children?

Answer 9

A clean catch urine sample

Question 10

If you cannot do a clean catch urine sample in children what can you do?

Answer 10

Use other non-invasive methods such as urine collection pads

If other non-invasive methods are not possible:
-Use a catheter sample of suprapubic aspiration

Question 11

How is suprapubic aspiration performed?

Answer 11

SPA is obtained by direct aspiration from a full bladder through the skin in the suprapubic area.

Such a sample is uncontaminated by urethral or perineal organisms and any growth is considered significant.

Question 12

What can the results of urine collection pads show?

Answer 12

These methods are helpful, if negative, to exclude a UTI but a high false positive rate makes diagnosis less accurate

Question 13

What are urine cultures?

Answer 13

Semi-quantitative
-A measued amount of urine is plated out and the number of colonies which grow is proportional to the number of organisms in the origninal sample

Samples are cultured on simple media which grow the faecal type organisms which commonly cause UTI.

The results are expressed as the number of organisms/ml

Question 14

Where are the causative organisms of UTI largerly derived from?

Answer 14

Faeces and there is an ascending route of infection via the urethra.

Question 15

Name the common UTI causative organisms

Answer 15

E. coli
Proteus sp.
Enterococcus faecalis
Klebsiella sp.
Pseudomonas sp.
Staph. saprophyticus

Question 16

What is the most common cause of UTI?

Explain why this is the case

Answer 16

E.coli

Strains with specialised projections called P fijmbraie are particularly adherent to uroepithelium and seem more likely than other strains to cause upper tract infection (acute pyelonephritis)

Question 17

What is Staph. saprophyticus?

Answer 17

Coagulase negative Staph which has been recognised as a cause of UTI, particularly in sexually active women.

Question 18

What do Proteus sp. produce?

Answer 18

The enzyme urease which splits urea to release ammonia, thus making urine alkaline and encouraging stone formation

Question 19

What bacteria species are more often found in hospital patients?

Answer 19

Proteus, Klebsiella and Pseudomonas sp

Often associated with catheters or instrumentation of the urinary tract

Tend to be more antibiotic resistant, especially Pseudomonas sp.

Question 20

Stones within the urinary tract are often associated with what species?

Answer 20

Proteus or Klebsiella UTIs:
-Hence such infections should always be investigated by way of upper renal tract imaging (e.g. non-contrast CT scan) to exclude renal tract stone disease

Question 21

Differentiating between contamination and infection is a major problem in urine microbiology.

How do you differentiate contamination from infection?

Answer 21

Urine is easily contaminated at the point of collection and the growth of mixed organisms is much more likely to reflect contamination than infection.

Question 22

The interprestation of lab results for urine depends on the consideration of what factors?

Answer 22

The number of organisms present.

the purity of the culture and presence or absence of white cells

Question 23

Describe microscopy of urine

Answer 23

Microscopy of unstained urine (“wet prep”) can be carried out to determine whether or not there are cells, casts or organisms present.

Question 24

What is pyuria and what does it show?

Answer 24

The presence of >10 white blood cells/mm3 in centrifuged urine is tremed significant pyuria, and this is a marker of inflammation.

The presence of pyuria is supportive evidence for the presence of infection rather than contamination

Question 25

Describe the use of symptomatic therapy in UTIs

Answer 25

Some uncomplicated infections will resolve on symptomatic therapy.

Drinking plenty of fluid (2-3L a day) and taking alkalinising agents which are available “over the counter” may bring relief and sometimes a “spontaneous” cure, although frequently the symptoms disappear while the bacteruria persists.

Question 26

Why is it important to distinguish between simple cystitis and acute pyelonephritis?

Answer 26

The treatment differs

Question 27

Describe the use of cranberry juice in UTI

Answer 27

A systematic review provides some evidence that cranberry juice reduces symptomatic UTIs in some women over a 12 month period.

However, there have been a large number of withdrawals in clinical trials and cranberry juice may not be acceptable to all patients

Question 28

Describe what the best treatment for UTI would be

Answer 28

Simplest, cheapest and safest oral antibiotic to which the infecting organism is sensible.

The antibiotic should reach high levels in urine and ideally have little effect on normal flora elsewhere

Question 29

Give an example of UTI antibiotics causing an upset in normal flora elsewhere

Answer 29

The development of vaginal thrush doe to Candida albicans is common in female patients who are treated with broad spectrum antibiotics

Question 30

Describe how you pick antibiotics for suspected lower UTI in women (Simple Cystitis)

Answer 30

The widespread use of antibiotics encourages the emergence of resistant organisms, so there is a tendency to prefer drugs in UTI which are not used in the treatment of other serious infections.

A 3 day course is generally thought to be sufficent in simple cystitis.

Question 31

What do the SIGN guidelines recommend for acute lower UTI in non-pregnant women?

Answer 31

3 days of trimethoprim or nitrofurantoin

Question 32

Describe treatment using Trimethoprim

Answer 32

Gives good coverage of appropriate organisms

Monotherapy with trimethoprim is now preffered to the combination drug co-trimoxazole which has a higher incidence of side effects for little gain in activity.

3 days treatment is probably enough

NOT used in pregnancy

Question 33

Describe treatment using Nitrofuratoin

Answer 33

Appropriate spectrum of activity (except proteus). Cheap and not used for anything other than simple UTI

Question 34

For suspected UTI in women what do you do if they do not respond to a 3 day course of either trimethoprim or nitrofurantoin.

Answer 34

Should have cultures taken

Question 35

How do you treat suspected lower UTI in men?

Answer 35

Longer antibiotic courses are recommended and some guidelines recommend 14 days of a guinolone (e.g. ciprofloxacin) for all men to cover the possibility of prostatitis.

The NHS grampian guidelines suggest 7 days of nitrofurantoin or trimethoprim if the infection appears uncomplicated

Question 36

How do you treat acute pyelonephritis?

Answer 36

Requires at least 7 days therapy, the choice of antibiotic being guided by sensitivity testing.

The SIGN guidelines suggest that non-pregnant women with symptoms of upper urinary tract infections should be treated with ciprofloxacin for 7 days.

This should be reviewed once the results of urine cultures and sensitivity tests are known

Question 37

How should treatment be given to patients admitted to hospital?

Answer 37

Patients admitted to hospital may be bacteraemic and parenteral therapy for the first 48 hours should be considered especially if the patient if vomiting.

Question 38

When should you investigate UTI?

Answer 38

Single episodes in men and repeat episodes in females should be investigated further for underlying pathology (e.g. renal calculi)

Question 39

When should resolution of infection be checked?

Answer 39

Resolution of infection should be checked by obtaining a urine sample 1-2 weeks after the cessation of antibiotic therapy

Question 40

How should you handle UTI in pregnancy (including asymptomatic bacteruria)?

Answer 40

Associated with premature labour and therefore should be treated.

Normal practice to take a MSU for culture at the first antenatal visit.

Positive cultures should be confirmed by repeat testing

Nitrofurantoin is safe during pregnancy but can cause neonatal haemolysis if used at term

Cephalexin is generally safe but treatment should be guided by sensitivities.

Question 41

How do you manage catheter relsted UTI?

Answer 41

Catheters become colonised with mixed organisms and a positive culture is not an indication for treatment.

Only patients with symptoms or signs of a UTI (e.g. fever, suprapubic pain, signs of systemic sepsis etc) should be treated.

Treatment should consist of the appropraite antibiotics preceded by changeing the catheter.

Question 42

When should you treat asymptomatic bacteraemia?

Answer 42

Pregnancy

When an operative procedure involving the urinary tract is planned

Question 43

What advice should you give people with recurrent UTI infections?

Answer 43

Drinking plenty of fluids

Emptying bladder after sexual intercourse

Attention to personal hygiene

Question 44

What further investigations may you carry out in people with reccurent UTI?

Answer 44

Gynaecological examination and IVP

Question 45

What treatment may help with recurrent UTI?

Answer 45

Long term antibiotic prophylaxis
-One tablet of nitrofurantoin or trimethoprim per night for up to one year may break the cycle when no predisposing factors can be found

For uncomplicated UTIs which are recurrent a single dose of appropriate antibiotic taken prophylactically immediately after intercourse may be beneficial