Urinary Tract Infection Flashcards
What is the general definition of an uncomplicated UTI?
Microbial colonization of the UT by pathogenic micro-organisms, and infection of the structures of the UT together with signs and symptoms of inflammation’
True or false: UTI’s may be ascending or descending
True
Ascending is most common (Microorganisms ascend into the bladder)
What is UPEC?
Among the common uropathogens associated to UTIs development, UroPathogenic Escherichia coli (UPEC) is the primary cause.
Are UTI’s endogenous or exogenous?
Endogenous
Are UTI’s communicable?
UTI’s are non-communicable
UTI may be ‘uncomplicated’ or ‘complicated’. Can uncomplicated UTI’s progress to complicated UTI’s?
Uncomplicated UTI may progress to complicated UTI
What is classed as significant bacteriuria?
- Presence of at least 105 bacteria / ml of urine
- May be symptomatic / asymptomatic
What is Cystitis (Lower UTI)?
- Infection of the bladder. Most common UTI
- Generally ascending
- Syndrome of frequency, dysuria (painful uriantion) and urgency
- Foul smelling (lots of bacteria and pus) / bloodstained urine (organisms can burst open red blood cells)
What is acute Pyelonephritis (Upper UTI)?
- Infection of one or both kidneys.
- Ascending (severe urinary reflux): complication of a UTI
- Descending (haematological spread from distant infection)
- Back, chills, fever, frequency and dysuria
- Far more aggressive than cyctitis
What is the difference between relapse and reinfection?
Recurrent UTI, may be relapse or reinfection:
- Relapse: recurrent UTI caused by the SAME microorganism that caused the original infection
- Reinfection: recurrent UTI caused by a DIFFERENT microorganism
Epide iology of UTI: Nosocomial (Hospital) Infections
- UTI are most common in hospitals (23.2%)
- A lot of patients have urinary catheters (plastic), microbes can stick to it and form biofilms
Community infections:
UTI account for approx what percentage of all GP consultations?
UTI account for approx 3% of all GP consultations
Draw a table of the prevalence of UTI’s acording to age
- 1-5 Females tend to have a shorter urethra -Organisms can enter and get acess to the bladder
- 18-60 (sexually active) due to sexual practices, organisms get pushed up the urinary tract
- 60-80- hospitalisation (urinary catheter) health declines
What percentage of women have a UTI per year?
5%
What percentage of women have a UTI during their lifetime?
50%
What percentage of non-pregnant women with a UTI will have a recurrence?
20% of non-pregnant women with a UTI will have a recurrence
Anal, perineal and perianal colonisation with faecal organisms such as:
E.Coli
Anal, perineal and perianal colonisation with skin organisms such as:
CNS
Microorganisms associated with community UTI: Which perecentage are associated with Escherichia coli?
80%
Microorganisms associated with community UTI: Which perecentage are associated with staphylococcus saprophyticus?
10%
Microorganisms associated with community UTI: Which perecentage are associated with Proteus mirabilis?
10%
Proteus mirabilis found in our gut
Microorganisms associated with hospital UTI: Which perecentage are associated with Escherichia coli?
50%
Microorganisms associated with hospital UTI: Which perecentage are associated with Proteus sp, Klebsiella sp and Enterobacter sp?
40%
Microorganisms associated with hospital UTI: Which perecentage are associated with Staphylococcus aureus (and MRSA) Coagulase negative staphylococci, Enterococcus faecalis and Candida albicans?
10%
Funngi e.g. candia albicans can overgrow when patient treated with (broad spectrum) antibiotics
Name some other, less frequent causes of UTI
(a) Viral – very rare; cytomegalovirus (CMV)
(b) Fungi – Candida species (hospitalisation, antibiotic use, catheterisation)
(c) Parasites: Schistosoma haematobium (Middle East, Africa, India)
(d) Mycobacterium tuberculosis / MAI (HIV, immunosuppressed) can get into bloodstream and become systemic
What is this organism?
Mycobacterium tuberculosis
What organism is this?
Schistosoma haematobium
What is this organism?
Candida albicans
Draw a table of the risk factors for UTI’s
- Contraceptive diapharam pressing on urethra, orevents urination
- Nonoxynol-9 is the chemical in spermicides eliminates lactobaillus (good bacteria) and allows e.coli to colonise
- Enlarged prostate in males can prevent effective urination
- Pregnant females- hormonal balance shifted
UTIs associated with specific serotypes of E. coli (UPEC): based on which antigens?
•O (cell wall), F (fimbriae/pilli) and K (located on the surface on the cell- surrounds somatic antigen) antigens
UPEC uropathogenic E. Coli
Pathogenesis of UTI: Which E. coli Virulence Factors promote attactchment?
•Fimbriae (harilike structures anchored in the cytoplasmic membrane and protude through the cell wall as proteinaceous hairlike structures involved with attachment: 100-400 per bacterium
- P fimbriae (pyelonephritis associated pili-PAP) Binds to galactose disacchaide moities on P blood group antigens of RBC and uroepithelial cells (widespread in genitourinary system)
- Type 1 fimbriae- FimH (high affininity to mannose receptors)
Pathogenesis of UTI: Which E. coli Virulence Factors promote the avoidance of host defence?
Polysaccharide capsule eg. K1 (sialic acid)
Pathogenesis of UTI:Describe the production of exocellular factors by E.Coli
Haemolysin; siderophores (enterobactin, aerobactin)
Draw a diagram of type 1 fimbriae
Describe the treatment of UTI
- Any symptomatic UTI requires antibiotics
- Bacteriuria (symptomatic or asymptomatic) screening is important and antimicrobial treatment is necessary
- Urine sample for microbiological analysis should always be taken prior to treatment
‘Antibiotics treat asymptomatic bacteriuria in pregnancy efficaciously, decreasing the incidence of pyelonephritis in the women treated. Antibiotic therapy also appears to reduce the incidence of low-birth-weight and preterm babies’ (World Health Organisation)
What is VUR?
Can be symptomatic or asymptomatic
It is abnormal flow of urine from your bladder back up the ureters up into the kidneys. Prophylactic antibiotics to stop potential renal scarring.
In preschool children with vesicoureteric reflux (VUR) and pregnant women requires antibiotic treatment
Describe the collection of appropriate clinical samples for microbiological analysis prior to antibiotic treatment
(1) Mid-stream urine (MSU): most common (gets rid of normal flora first)
(2) Bag-urine / suprapubic aspiration (avoids fecal contamination but very invasive)
(3) Catheter specimen of urine (CSU) (Urine has been collecting and sat around for a while likely to be overgrown with different fecal and skin microbes)
Foley catheter
Treatment of uncomplicated Lower UTI (short course therapy)
Describe the MOA of Nitrofurantoin (1952) 50mg/ qds
First line of treatment
In its primary state has no antimicroial activity, its secondary (reduced) form is active and acts on protein syntheisis, DNA synthesis, respiration.
- MOA is unique: reduced by bacterial flavoproteins (nitrofuran reductase); ribosomal protein and DNA damage; respiration; pyruvate metabolism.
- Multi-target activity may account for current widespread sensitivity
- Can be given in pregnancy
Treatment of uncomplicated Lower UTI (short course therapy)
Describe the MOA of Trimethoprim 200mg/bd
- MOA: inhibits dihydrofolate reductase; DHF cannot be reduced to THF (precursor in thymidine synthesis); DNA production inhibited.
- Teratogenic (interfere with the develpment of foetuses- birth defects) risk ( not given during pregnancy)
Treatment of complicated Upper UTI (Pyelonephritis)
Describe the MOA of ciprofloxacin 500mg/bd
10-14 days (consider initial i.v administration followed by oral once afebrile)
- MOA: inhibition of DNA gyrase
- High tissue concentrations achieved
- Avoid in pregnancy (arthopathy)
Treatment of complicated Upper UTI (Pyelonephritis)
Describe the MOA of Ceftriaxone
Given intrvenously
Once daily; 10-14 days (no oral formulation)
- MOA: inhibition of PBP
- Hypersensitivity
Describe the prevention of UTI /recurrent UTI and
non-specific therapy
- Low dose antibiotic eg. nitrofurantoin 50-100mg at night (prophylactic antimicrobial)
- Cleanse genital area before sexual intercourse
- Single dose antibiotic after sexual intercourse / void urine
- Drink plenty of water / do not resist urination
- ? Cranberry Juice (published in New England Journal of medicine NEJM, 1998); condensed tannins bind to fimbirae of E. coli and stops them from attatching to the bladder wall
Inhibition of the Adherence of P-Fimbriated Escherichia coli to Uroepithelial-Cell Surfaces by Proanthocyanidin Extracts from Cranberries; NEJM, 1998
Condensed tannins bind to fimbirae of E. coli and stops them from attatching to the bladder wall
Diagnostic Clinical Microbiology: Case study
A 20-year old female presents to her GP complaining of a burning sensation in her bladder along with frequent and painful urination
- Her urine is cloudy and foul smelling
- She informs the GP that she suffers from recurrent UTIs
What is the most likely pathogen?
Reasons for laboraotry confirmation of infection
- Confirm the aetiological agent
- Ensure appropriate antibiotics are given
- Avoid the possibility of further complications
Describe specimen collection and transport
- Correctly labelled specimen and patient form (creates an audit trail)
- MSU ideally collected in a container with 1.8% (v/w) BORIC ACID is a preservative (red top); 20mL needed
- Transport <24h (boric acid may ‘preserve’ bacteria for up to 72hrs)
- Refrigeration, 4oC if necessary
Automated Urinalysis Now Widespread in Clinical Microbiology commonly used:
- Iris iQ200 ELITE
- UF 1000
Laboratory Investigations, non-culture techniques
Microscopy (eg. light microscopy, phase contrast)
(a) Allows a rapid preliminary report
(b) Examine for: bacteria; white blood cells; red blood cells; parasites
(c) Presence of WBC and HIGH numbers of bacteria is suggestive of UTI
(d) Presence of large numbers of intact RBC may indicate other disease eg. renal trauma, carcinoma (should not be present in normal urine)
Laboratory Investigations, Semi-quantitative culture
(a) 2ul of MSU cultured onto CLED agar (Cystine-Lactose-Electrolyte Deficient; differential/selective agar)
(b) 37oC /air /24h
(c) 20 - 200 colonies on CLED =
104 – 105 CFU/ml of urine
(d) >200 colonies →105CFU/ml of urine therefore a significant bacteria
(e) E. coli is a lactose fermenting colony, 2-3mm diameter (blue to yellow)
Describe the Full Identification of E.coli (API)
(b) Tests commonly positive for E. coli :indole; LDC / ODC; fermentation of glucose (+gas), sorbitol, mannitol
(c) Tests negative for E. coli: urease; citrate, gelatin
Remember….
MALDI-TOF (MS) for bacterial ID is now being used in many laboratories
Describe Sterile Pyuria
Sterile pyuria is the presence of elevated numbers of white blood cells (>10 white cells/mm3) in urine which appears sterile using standard culture techniques.
I.E. High WBC (pus) on microscopy (indicative of UTI) but no organisms recovered with routine culture on CLED agar
(a) Renal tuberculosis (3x EMU)
(b) Antibiotic treatment prior to MSU collection
(c) Urethritis (eg STIs Trichomonas vaginalis, Chlamydia trachomatis)
(d) Vaginitis: vaginal discharge (lots of WBC produced which can contaminate the urine sample)
UTI: Key Points
- Common in hospital and community
- E. coli is the major pathogen
- All symptomatic UTI requires treatment
- Asymptomatic bacteriuria should be treated in preschool children / pregnant women
- 3-day short course treatment is now recommended in uncomplicated lower UTI in women
- 10-14 day treatment in upper UTI, males, pregnancy, recurrent UTI
- Prophylactic antibiotics for recurrent UTI / non-specific therapy
- Sterile pyuria requires further investigation
Are infections of the urethra classed as a UTI?
No
Thats an STI
- UTI’s involve the bladder, ureters and kideneys
Is the uninary tract sterile?
Yes
The only non sterile part is the very distal tip of the urethra which contains skin and normal flora
Describe the female urethra and why females are lmoresusceptible to UTI’s
- Lots of orificies close together
- Short urehtra leading up to the bladder
Male urethra
- Urethra approximately 12-20cm
