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Pathology > Microbiology - UTI > Flashcards

Microbiology - UTI Flashcards

1
Q

is the urethra sterile? what about bladder?

A
  • urethra is not sterile

- urine in bladder is sterile but urine coming out urethra is not sterile

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2
Q

what happens id squamous epithelial cells are found in MSU sample?

A

sample hasn’t been taken properly

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3
Q

define bacteriuria

A

presence of bacteria in urine

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4
Q

Is asymptomatic bacteriuria relevant?

A

not usually relevant

but asymptomatic bacteriuria with coliform is significant in PREGNANCY

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5
Q

define cystitis

A

inflammation of bladder
often caused by infection
AKA: LOWER UTI

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6
Q

what is an uncomplicated cystitis?

A

infection in a structurally and neurologically normal urinary tract

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7
Q

what is an uncomplicated cystitis?

A

infection with functional or structural abnormalities e.g. indwelling catheters and calculi

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8
Q

in which groups of patients is the UTI classed as complicated?

A
  • men
  • pregnant women
  • children (not young girls)
  • patients in a HC associated settings
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9
Q

what are most UTIs caused by?

A
  • over 95% of UTIs are caused by single bacterial species
  • most common: E.coli
  • E.coli have adherence factors that allow it to prevent being flushed out by passage of urine
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10
Q

what is the 2nd most common cause of UTI in young women?

A 
Staphylococcus saprophyticus (coagulase -ve)
has virulence factor (P-fimbriae) that allow adherence to epithelium
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11
Q

which bacteria causes UTIs in presence of prosthesis? (e.g. procedures/ long term indwelling catheter)

A

staphylococcus epidermis

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12
Q

what other organisms can cause UTIs?

A
  • proteus mirabilis
  • klebsiella aerogenes
  • enterococcus faecalis
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13
Q

what does recurrent UTIs suggest about the organism?

A

recurrent UTIs (esp in presence of structural abnormalities) increases chances of infection caused by non E.coli organisms (e.g. proteus, pseudomonas, klebsiella, enterobacter, enterococci, staphylococci)

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14
Q

what antibacterial host defences does the urinary tract have?

A
  • urine (osmolality, pH, organic acids to try to stop some bacteria entering)
  • urine flow (movement of urine stop bacteria)
  • urinary tract mucosa (bactericidal activity, cytokines)
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15
Q

why are females more susceptible to UTIs?

A
  • female urethra is short and in proximity to vulvar/ perianal areas
  • contamination is likely
  • organisms that cause UTI colonise vaginal/periurethral area first
  • massage of urethra/sexual intercourse can force bacteria into bladder
  • once in bladder bacteria can multiply
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16
Q

why can renal tract abnormalities increase susceptibility to infection?

A
  • obstruction inhibits flow of urine

- stasis of urine

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17
Q

what are the mechanical causes of obstruction?

A

Extrarenal: valves/stenosis/bands, calculi, BPH
Intrarenal: nephrocalcinosis, analgesic nephropathy, uric acid nephropathy, PKD, hypokalaemic nephropathy

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18
Q

causes of neurogenic malfunction that increase susceptibility to infection

A
  • poliomyelitis
  • tabes dorsalis
  • diabetic neuropathy
  • spinal cord injuries
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19
Q

what is the problem with vesicoureteric reflux?

A
  • perpetuate infection by maintaining residual pool of infected urine in bladder after voiding
  • reflux can result in scarring of kidneys
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20
Q

how can the haematogenous route affect the kidney?

A
  • kidney frequent site of abscess in pt with S. aureus bacteraemia or endocarditis
  • S. aureus normally doesn’t cause UTI
  • S. aureus doesn’t have appropriate virulence factors to cause ascending infection
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21
Q

symptoms of UTI in children <2 years (inc. neonates)

A

symptoms are non specific

  • failure to thrive
  • vomiting
  • fever
22
Q

symptoms of UTI in children >2 years

A

localised symptoms

  • frequency
  • dysuria
  • abdominal or flank pain
23
Q

what are the lower UTI symptoms?

A
  • bacteria = irritation of urethral and vesical mucosa = frequent/painful urination of small amounts of turbid urine
  • suprapubic heaviness/pain
  • gross haematuria
  • fever absent (in infections confined to lower UT)
24
Q

what are the upper UTI symptoms?

A
  • lower UT symptoms (frequency, urgency, dysuria) = may precede UUTS by 1/2 days
  • fever with rigors
  • flank pain
25
Q

what are the symptoms of UTI in older patients?

A
  • asymptomatic (not specific symptoms)
  • atypical (e.g. abdo pain, confusion)
  • diagnosis difficult as non infected older pts often experience frequency/dysuria/hesistancy and incontinence
26
Q

investigations of uncomplicated UTI/pyelonephritis

A
  • urine dipstick
  • MSU for urine MC&S
  • Bloods - FBC, U&E, CRP
27
Q

what do nitrites in the urine suggest?

A

E.coli UTI

E. coli produces lots of nitrites

28
Q

Leucocyte esterase +ve

Nitrite +ve

A

UTI

29
Q

Leucocyte esterase -ve

Nitrite +ve

A

start ABx

further management guided by urine culture

30
Q

Leucocyte esterase +ve

Nitrite -ve

A

only start ABx of clinical evidence of UTI

may be caused by non-coliform bacterium

31
Q

further investigations for complicated UTI

A

renal USS

IV urography

32
Q

what should you consider in sexually active young men?

A

chlamydia trachomatis

33
Q

in which patients should laboratory testing for MC&S be done?

A
  • pregnancy (asymptomatic bacteriruia issue)
  • suspected UTI in children
  • suspected UTI in men
  • suspected pyelonephritis
  • catheterised pt
  • failed antibiotic tx (resistance)
  • abnormalities in GU tract
  • renal impairment
34
Q

why is a MSU better than first catch urine?

A
  • more representative of what is going on in bladder

- first catch may be contaminated by urethral bacteria that is not part of disease process

35
Q

what is the problem with giving unnecessary antibiotics?

A
  • killing normal bacteria may result in thrush

- yeasts not affected by Abx

36
Q

which urine culture results are diagnostic of a UTI?

A
  • culture of single organisms >10^5 CFUs/mL + urinary symptoms
  • culture of E.coli or S.saprophyticus >10^3 CFUs/mL + urinary symptoms
37
Q

how do you interpret white cells in urine culture?

A

WBCs >10^4/mL = inflammation

pyuria is usually absent in childre

38
Q

what can contaminate a urine culture?

A
  • mixed growth reduces significance of urine culture (suggests contamination)
  • epithelial cells present in high numbers = failed MSU technique
39
Q

if there is a sterile pyuria (raised WCC but no growth on culture) what could it be?

A
  • prior treatment with antibiotics (most common)
  • catheterisation
  • TB
  • Calculi
  • bladder neoplasm
  • STI (Chlamydia)
40
Q

what are the different lab testing techniques?

A
  • microscopy
  • culture (chromogenic agar - turns different colours based on growth)
  • sensitivities
41
Q

what different colours does chromogenic agar go?

A
  • Pink = E. coli
  • Blue = other coliforms
  • Light blue = gram +ve
42
Q

what sampling techniques are used?

A
  • MSU (best method)
  • Catheterisation ( may introduce organisms)
  • Suprapubic aspiration (very young children)
43
Q

what are the most common antibiotics used for uncomplicated UTIs?

A
  • trimethoprim
  • nitrofurantoin (not in pregnancy as associated with haemolysis)
  • cephalexin
44
Q

how long is treatment given for?

A
  • 3 das of therapy for uncomplicated UTI in women

- women with previous UTI caused by antibiotic resistant organisms or > 7 days symptoms and in men give 7 days of tx

45
Q

which patients are affected by candida UTIs?

A

pts with indwelling catheters

46
Q

management of candida UTIs?

A
  • removal of catheter
  • antifungals no more effective than no therapy
  • no benefit in treating asymptomatic infection
47
Q

when should you treat asymptomatic candida UTIs?

A
  • renal transplant patients

- pts who are waiting to undergo elective urinary tract surgery

48
Q

define pyelonephritis

A

infection of kidney

49
Q

what is the link between organism number and infection of parts of kidney?

A
  • few organisms needed to infect renal medulla

- many needed to infect cortex

50
Q

management of pyelonephritis

A
  • prior to culture results = amoxicillin (or ciprofloxacin)

- culture results = co-amox, gentamicin

51
Q

when do you do imaging in men/women?

A 
men = calculi
women = structural cause
52
Q

complications of pyelonephritis?

A
  • perinephric abscess
  • chronic pyelonephritis (scarring, chronic renal impairment)
  • septic shock
  • acute papillary necrosis

Pathology (21 decks)

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