Urinary tract infection (UTI) Flashcards
What is a UTI?
Urinary tract infections are infections anywhere along the urethra, bladder, ureters and kidneys
What is meant by lower UTI?
Infection confined to the bladder (Cystitis) and urethra
What is meant by upper UTI?
Infection involving the ureters or kidneys (Pyelonephritis)
What is the most common type of organism in UTI?
Gram -ve aerobic bacilli
What are the 2 main groups of gram -ve aerobic bacilli
Lactose fermenters
Lactose non-fermenters
What are some important lactose fermenters in UTI?
- Eschericia coli (E.coli) - Most common
- Klebsiella sp.
- Enterobacter sp.
- Serratia sp.
- Citrobacter sp.
What re the 2 main groups of non-lactose fermenting gram -ve aerobic bacilli?
Oxidase negative
Oxidase positive
What are some important oxidase -ve bacteria in UTI?
- Morganella sp.
- Proteus sp.
- Providencia sp.
What is an important oxidase +ve bacteria in UTI?
Pseudomonas aeruginosa
What is the most common pathogen in UTI?
Escherichia coli (E.coli)
What is a virulence factor of E.coli
Endotoxin - Causes fever
Give the characteristics of proteus UTI
1-10% of UTIs
Foul smelling, like burnt chocolate
Proteus produces urease which breaks down urea to form ammonia, which increases urinary pH
This can lead to the precipitation of salts, leading to struvite stone formation
Give the chacareristics of pseudomonas aeruginosa UTI
Gram negative bacillus
Less common cause of UTI, associated with catheter and instrumentation
It is intrinsically resistant to most oral antibiotics, except ciprofloxacin (4C antibiotic)
Give the characteristics of enterococcus UTI
These are a common form of streptococci found in the GI tract
Examples include:
- Enterococcus faecalis
- Enterococcus faecium
Give the characteristics of staphylococcus saprophyticus UTI
A form of coagulase negative staphylococcus, common in women of childbearing age, commonly causing lower tract community infection
Give the characteristics of staphylococcus aureus UTI
Staph. aureus is uncommon in UTI and is usually in bacteraemia
What are some risk factors for UTI
Women
Catheterised patients
Abnormalities of the urinary tract
Why are women at greater risk of UTI?
Short, wide urethra, proximity of urethra to anus, increased risk with sexual activity and pregnancy
What is acute pyelonephritis?
Infection of the tissue of the kidney
Does urine usually contain bacteria?
No, urine within the kidneys, ureters and bladder is usually sterile
It can be contaminated on the way out by bacteria in the lower end of the urethra
What are some bodily defences for bacteria entering via the urological system?
Urine acidity
Complete voiding
Vesicouteric valve
Mucosal and immunological defences
What are the 2 main routes of infection of the urinary tract?
Ascending route (Bacteria from bowel enters and travels up)
Haematogenous route
What are the 2 classes of UTI?
Complicated UTI
Uncomplicated UTI
What is meany by uncomplicated UTI?
- This is a UTI where the anatomy of the urinary tract is normal, and renal imaging will be normal
- No underlying condition contributing to infection
- Unlikely to result in serious kidney damage
What is meant by complicated UTI?
this will occur in urinary tracts with sepsis stones, or also in diabetes
How may complicated UTI occur?
- The recurrent infections can themselves contribute to stone formation
- The combination of recurrent infection and urinary tract obstruction can result in sever and rapid kidney damage
- In these conditions there is a risk of Gram-negative septicaemia
How does a UTI present?
- Dysuria (Pain passing urine)
- Frequency of urination
- Nocturia
- Haematuria
What are some features suggestive of upper urinary tract involvement?
- Fever
- Loin pain
- Rigors
What is bacterial cystitis (Urethral syndrome)?
This is a condition in which a patient has symptoms of UTI, with pus cells present in urine but no significant growth on culture
What are some possible causes of abacterial cystitis?
- Early phase of UTI
- Urethral trauma (Honeymoon cystitis)
- Urethritis caused by chlamydia or gonorrhoea
How may abacterial cystitis be managed?
Alkalinising the urine
What are some investigations used in UTI diagnosis?
Midstream specimen of urine (MSU)
Urine dipstick (Urinalysis)
Lab analysis
What are some other forms of urine collection used in those who can’t provide an MSU?
- ‘Clean catch’ - children, cognitive, or physical restriction
- Bag urine - babies
- Catheter specimen of urine
- Suprapubic aspiration
Who may not be able to provide an MSU?
Elderly
Those with intellectual disabilities
Children
Who is not suitable for urinalysis in UTI?
Elderly
Those with a catheter
What are some signs of UTI on urinalysis?
Leukocyte esterases - Indicated WBCs
Nitrates - Indicates bacteria
Protein + Blood
Describe the process of obtaining a midstream specimen of urine
- Sterilise the labia or tip of penis
- Remove the screw cap, not touching the inside surfaces of the container or cap
- Women hold open labia and men pull back foreskin
- Start to pass some urine into the toilet for 1-2 seconds, without stopping, start to collect the urine sample
- Finish passing the rest into the toilet
What are the 2 main types of urine specimen container?
- Boricon container - Contains boric acid to stop bacteria multiplying, which works for ~24 hours
- Sterile universal container - Must reach the lab within 2 hours
What are the 3 stages of Kass’ criteria for UTI?
- > 10^5 organisms/ml ⇒ Significant ⇒ Probable UTI
- 10^4 organisms/ml ⇒ Query contamination ⇒ Repeat specimen
- < 10^3 organisms/ml ⇒ Not significant bacteriuria
> 10^5 organisms/ml
Significant -> Probable UTI
10^4 organisms/ml
Query contamination -> Repeat specimen
< 10^3 organisms/ml
No significant bacteriuria
What does a mixed growth (≥2 organisms) suggest?
even if >10^5, is probably not significant unless there are abnormalities of the urinary tract as it is more suggestive of a contamination
Management: Female uncomplicated lower UTI
3 days nitrofurantoin (100mg BD) or trimethoprim (200mg BD) PO
Management: Uncatheterised male UTI
Culture
7 days nitrofurantoin (100mg BD) or trimethoprim (200mg BD) PO
Management: Complicated UTI or pyelonephritis in primary care
Co-amoxiclav or co-trimoxazole (7 days)
Management: Complicated UTI or pyelonephritis in hospital
- Amoxicillin and gentamicin IV for 3 days
- Co-trimoxazole and gentamicin if penicilllin allergy
- Stepdown as guided by antibiotic sensitivities
What are some antibiotics usually used for coliforms?
- Gentamicin IV
- Amoxicillin IV/PO
- Trimethoprim PO
- Cotrimoxazole IV/PO
What are some antibiotics usually used in enterococci?
- Amoxicillin PO
- Cotrimoxazole IV/PO
How is asymptomatic bacteriuria usually managed?
- Antibiotic treatment is generally not required, especially in the elderly
- Treatment required in asymptomatic bacteriuria in pregnancy
How is UTI managed in catheterised patients?
- Only give antibotics if there is fever/symptoms
- Unnecessary antibiotics result in the catheter becoming colonised with increasingly resistant organisms
What does CFU stand for?
Colony Forming Unit (Bacteria in a sample)
What does MIC stand for?
Minimum Inhibitory Concentration
What does MBC stand for?
Minimum Bactericidal Concentration
What is meant by MIC?
The minimum concentration of a drug required to inhibit growth of a bacteria
What is meant by MBC?
The minimum concentration of a drug required to kill all bacteria
