Diagnosis and Treatment Flashcards
What situations should cultures be taken in suspected UTI?
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
When should you not routinely culture urine?
You should NOT routinely culture urine from asymptomatic, non-pregnant patients, wether they have urinary catheters or not
How should Mid-stream urine be collected?
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.
Why should you store urine in a refrigerator or in boric acid?
Urine is a good culture medium so this prevents bacterial overgrowth
If there is likely to be a delay in specimen reaching the laboratory what alternative method can you use?
Dipslide
What is a dipslide
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
What is the downside of using a dipslide?
Does not allow microscopy or related studies to be performed on the urine itself
How should catheter specimens be obtained?
From the catheter sampling port and not from the collection bag
What is the recommended method for urine collection in children?
A clean catch urine sample
If you cannot do a clean catch urine sample in children what can you do?
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
How is suprapubic aspiration performed?
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.
What can the results of urine collection pads show?
These methods are helpful, if negative, to exclude a UTI but a high false positive rate makes diagnosis less accurate
What are urine cultures?
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
Where are the causative organisms of UTI largerly derived from?
Faeces and there is an ascending route of infection via the urethra.
Name the common UTI causative organisms
E. coli Proteus sp. Enterococcus faecalis Klebsiella sp. Pseudomonas sp. Staph. saprophyticus
What is the most common cause of UTI?
Explain why this is the case
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)
What is Staph. saprophyticus?
Coagulase negative Staph which has been recognised as a cause of UTI, particularly in sexually active women.
What do Proteus sp. produce?
The enzyme urease which splits urea to release ammonia, thus making urine alkaline and encouraging stone formation
What bacteria species are more often found in hospital patients?
Proteus, Klebsiella and Pseudomonas sp
Often associated with catheters or instrumentation of the urinary tract
Tend to be more antibiotic resistant, especially Pseudomonas sp.
Stones within the urinary tract are often associated with what species?
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
Differentiating between contamination and infection is a major problem in urine microbiology.
How do you differentiate contamination from infection?
Urine is easily contaminated at the point of collection and the growth of mixed organisms is much more likely to reflect contamination than infection.
The interprestation of lab results for urine depends on the consideration of what factors?
The number of organisms present.
the purity of the culture and presence or absence of white cells
Describe microscopy of urine
Microscopy of unstained urine (“wet prep”) can be carried out to determine whether or not there are cells, casts or organisms present.
What is pyuria and what does it show?
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
Describe the use of symptomatic therapy in UTIs
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.
Why is it important to distinguish between simple cystitis and acute pyelonephritis?
The treatment differs
Describe the use of cranberry juice in UTI
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
Describe what the best treatment for UTI would be
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
Give an example of UTI antibiotics causing an upset in normal flora elsewhere
The development of vaginal thrush doe to Candida albicans is common in female patients who are treated with broad spectrum antibiotics
Describe how you pick antibiotics for suspected lower UTI in women (Simple Cystitis)
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.
What do the SIGN guidelines recommend for acute lower UTI in non-pregnant women?
3 days of trimethoprim or nitrofurantoin
Describe treatment using Trimethoprim
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
Describe treatment using Nitrofuratoin
Appropriate spectrum of activity (except proteus). Cheap and not used for anything other than simple UTI
For suspected UTI in women what do you do if they do not respond to a 3 day course of either trimethoprim or nitrofurantoin.
Should have cultures taken
How do you treat suspected lower UTI in men?
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
How do you treat acute pyelonephritis?
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
How should treatment be given to patients admitted to hospital?
Patients admitted to hospital may be bacteraemic and parenteral therapy for the first 48 hours should be considered especially if the patient if vomiting.
When should you investigate UTI?
Single episodes in men and repeat episodes in females should be investigated further for underlying pathology (e.g. renal calculi)
When should resolution of infection be checked?
Resolution of infection should be checked by obtaining a urine sample 1-2 weeks after the cessation of antibiotic therapy
How should you handle UTI in pregnancy (including asymptomatic bacteruria)?
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.
How do you manage catheter relsted UTI?
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.
When should you treat asymptomatic bacteraemia?
Pregnancy
When an operative procedure involving the urinary tract is planned
What advice should you give people with recurrent UTI infections?
Drinking plenty of fluids
Emptying bladder after sexual intercourse
Attention to personal hygiene
What further investigations may you carry out in people with reccurent UTI?
Gynaecological examination and IVP
What treatment may help with recurrent UTI?
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
