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Micro Lec 3 Flashcards

UTI lecture (77 cards)

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1
Q

Are most urine samples received negative or positive for culture and microscopy

A

negative

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2
Q

Automated sample processing is increasingly used, what are these known as

A

UF1000
WASP lab

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3
Q

The urinary tract is normally sterile apart from what

A

the urethra

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4
Q

Where do most urinary tract infections commonly ascend from

A

the urethra

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5
Q

List mechanisms to avoid infection of the urinary tract

A
  • Diluting and flushing action ofurine production
  • Valve between bladded and ureter prevents reflux
  • Extreme low pH, high osmolarity, IgA secretion, high urea concentration
  • Proteins that prevent attachment
    - Tamm Horsfall protein (uromodulin) produced by kidney, binds E. coli
    - GP51 protein secreted by bladder epithelial cells binds many bacteria preventing adhesion
    - Manno-oligosaccharide in urine – binds E. coli
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6
Q

List the risk factors for UTI

A
  • Catherisation
  • Obstruction
  • Vesicoureteric reflux
  • Pregnancy
  • Diabetes
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7
Q

How does obstruction cause risk for UTI

A
  • Enlarged prostate, urinary stones, congenital
  • Malformations
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8
Q

How does vesicoureteric reflux cause risk of UTI

A

caused by abnormal valve development

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9
Q

How does pregnancy cause risk of UTI

A

Impaired urine flow due to hormonal changes (many cause dilation of ureters) and pressure on the UT

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10
Q

How does diabetes cause risk of UTI

A

Autonomic neuropathy leads to incomplete emptying of the bladder

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11
Q

List two commonly associated UTIs and where they are often seen

A
  • Staphylococcus saprophyticus which is commonly found in sexually active women
  • ESBL-producing E. coli are seen in community patients, who have has no contact with the healthcare system
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12
Q

Describe hospital associated UTI

A

Pathogens are often resistant to antimicrobials

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13
Q

List other pathogens of the urinary tract - fungal

A
  • Candida albicans, unicellular yeast, divides by budding
  • Commensal of the skin, GIT, female genitalia, associoated with urinary catheters - CAUTI
  • Isolation from neonates or immunocompromised may indicated haematogenous spread to kidneys; serious infection, women wish thrush or babies wirth nappy rash may have Candida contaminating urine samples
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14
Q

Outline the features of the cystitis

A

inflammation of the bladder
95% of LUTI
caused by E.coli

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14
Q

What is cystitis

A

An infection of the lower urinary tract

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15
Q

What are the symptoms of Cystitis

A

dysuria, frequency, suprapubic pain (pain in the lower abdomen)

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16
Q

What is acute pyelonephritis

A

An infection of the upper urinary tracts, infection of the kidney

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17
Q

what is the most common cause of acute pyelonephritis

A

E. coli

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18
Q

What are the symptoms of acute pyelonephritis

A

flank pain, fever, nausea, vomiting

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19
Q

Acute pyelonephritis is an ascending infection, what do a third of cases lead to

A

bacteraemia

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20
Q

What is chronic pyelonephritis

A

an infection of the upper urinary tract, chronic inflammation of the kidney

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21
Q

What is chronic pyelonephritis associated with

A

Obstruction of the urinary tract, vesicoureteric reflux in children

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22
Q

Is chronic pyelonephritis a renal abscess

A

yes

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23
Q

Short term, when is a foley catheter used

A

during an operation
- latex

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24
Long term, when is a foley catheter used
prostate problems, physical disability - silicone, PVC, teflon, silver coated
25
How is a foley catheter inserted
aseptically
26
Using a CAUTI, source of microrganisms may be
endogenous OR exogenous
27
Provide examples of endogenous source of microorganisms
meatal, rectal, or vaginal colonisation - from the patient themself
28
Provide examples of exogenous source of microorganisms
usually via contaminated hands of healthcare personnel during catheter insertion or manipulation of the collecting system
29
List organisms associated with CAUTI
Leading pathogens -E. coli, Proteus, Pseudomonas, Klebsiella, Serratia, Staphylococci, Enterococci and Candida Bacterial growth on the surface, urinary proteins, urinary salts lead to encrustation; biofilm formation
30
Outline the steps of pathogenesis of biofilm. formation on urinary catheters during CAUTIs
1 - Coating of catheter with host proteins 2- Introduction of organisms 3- Cell attachment and monolayer formation 4 - Cell wall adhesion and proliferation 5 - Biofilm maturation 6 - detachment
31
Can CAUTI symptoms resolve
symptoms minimal and generally resolve on removal of catheter
32
Outline 2 CAUTI complications
1-2% of catheter-associated bacteriuria leads to bacteraemia 30% of hospital-associated GNR bacteraemias are associated with CAUTI
33
List methods of specimen collection
- Mid-stream urine (MSU) - Clean-catch urine - Pad urine - Bag urine - Suprapubic aspirate - Catheter stream urine (CSU)
34
Outline the features of Mid-stream urine (MSU)
Majority of samples. The first urine is passed and discarded - contaminated with organisms colonising the distal region of the urethra. Mid-stream urine is collected in a sterile pot. Not suitable for very young/very old.
35
Outline the features of clean-catch urine
Used for very young children. Sample caught into a sterile container. Equivalent to an MSU. Requires patience.
36
Outline the features of pad urine
Absorbent pad placed in nappy and checked regularly. Alternative to clean-catch. Problems with sample contamination.
37
Outline the features of bag urine
alternative to pad urine, where a bag collects the sample
38
Outline the features of suprapubic aspirate
Collected if alternatives have failed. A needle through the skin aspirates urine directly from the bladder
39
Outline the features of catheter stream urine (CSU)
Samples taken through a port aseptically
40
How must samples be transported
quickly and high temps avoided
41
What should happen if sample transport delays are unavoidable
Refrigerate at 4 degrees celsius for max of 24hrs Add boric acid, a preservative
42
What information can helkp confirm an infection
- Detection of a single bacterial pathogen associated with UTI- bacteriuria - Elevated number of white blood cells (WBC) in the sample - pyuria - Observation of fungi or parasites in the sample
43
How do dip slides work
agar on both sides, one nutritious one selective, once urine on bacterial growth give levels of bacteria within sample, hardly any = urine from patient is contaminated with surface bacteria, high growth = uti infection
44
What is helpful during sample processing microscopy
- Wet prep is helpful = fixed volume of urine aliquoted into well and observed under x40 mag and quantify - WBC -10WBC/microlitres is signification; pyuria. Delayed processing or Proteus mirabilis can lead to lower counts = if there is a high WBC count but no organism isolated; sterile pyuria - RBC-RBC in urine is abnormal; haematurie. May indicated glomerulonephritis, renal calculi or malignancy - gram stain of no use
45
sample procession microscopy 2
- Epithelial cells indicated skin contamination - Bacterial cells, fungi and parasites = visible bacteria is not diagnostic, fungi or parasites is diagnostic - Casts = proteinaceous structures produced by the kidneys, May occur due to different pathologies
46
Where do urinary casts form
in the distal nephron
47
What are cylindrical 'casts' of renal tubules made of
Tamm-Horsfall protein
48
What can become attached to urinary casts
particular matter, break off and pass into urine
49
What are hyaline casts formed by
stressed cells
50
Outline the features of cellular casts
cells attached the cast surface due to acute tubular injury
51
Outline the features of Granular casts
Four types Degeneration of cellular casts
52
What are the bacterial thresholds and what do they mean
1 x 10^5 CFU/ml is significant 1 x 10^4 CFU/ml of a pure culture is used as the threshold in labs
53
List the methods of quantifying bacteria in urine
- Calibrated loop - Paperfoot method - Multipoint inoculator - Dip slide
54
Describe the calibrated loop method
A fixed volume of urine is spread on the agar plate 1 microlitre or 10 microlitres loop used The CFU per ml urine can be calculated after incubation of the plate
55
Describe the dip-slide method
Direct observation of the CFU on the agar surface allows the CFU/ml to be determined
56
What is a disadvantage of the dip-slide method
no microscopy results
57
Outline the features of urine analysis media
- Cysteine lactose electrolyte deficient (CLED) - Distinguishes lactose (LF; yellow colonies) and non- lactose fermenting (NLF; colourless colonies) organisms - Prevents Proteus species swarming
58
Based on the traditional CLED medium how is the swarming of proteus spp prevented
two chromogens are present in the medium. One allows the detection of enterococci giving rise to blue colonies whilst the second results in purple colonies of E. coli. Phenylalanine and Tryptophan are also included as indicators of Tryptophan deaminase activity producing brown colonies of Proteus spp
59
Outline the features of chromogenic media
- Hydrolysis of substrates in the agar by bacterial enzymes produced coloured products - Allow identification based on colour of colonies - Rapid identification
60
Compare CLED to chromogenic media
- CLED is cheap but differentiation of colony types is limited. May require 48hr to obtain a result - Chromogenic is more expensive, but colonies are easier to differentiate and presumptive identifications can be made at 24hr
61
Outline the features of point of care testing
Near patient testing Reduces numbers of urine samples being sent for processing
62
Table on pg
37
63
Outline the features of automated analysis of urine using UF1000
-Digital imagine and auto particle recognition software - recognises specific urine particles: RBC, WBC, hyaline casts, squamous epithelial cells, bacteria, yeasts - Quantifies all of the above - Can be viewed on screen - Parameters set for +/- microscopy, signals which will require cultured
64
Outline the features of WASP lab automation
- Pre-analytical laboratory automation, generating value in terms of effectiveness and efficiency. - Automation meets the following needs of the laboratory: -Speed -High level of standardisation -Full traceability -Proficiency of sample set up Inoculation phase: incubation in CO2 or O2 reading and picking activities.
65
List three urinary tract pathogens
- E. coli - Proteus mirabilis - Staphylococcus saprophyticus
66
Describe the pathogen E.coli
- Major facultative-anaerobic inhabitants of the human gut - Gram negative bacilli - Usually motile, flagella - Often have fimbriae -Class I and II, associated with infection -P fimbriae (bind to P blood group antigens on RBC and uroepithelial cells) - Often produce a polysaccharide - capsule - Ferment lactose - Oxidase negative
67
Describe the pathogen Proteus mirabilis
- Commensal of 50% of individuals - Principally associated with UTI - NLF, GNR - Virulence associated with: - Highly motile -Swarming motility - Produces large quantities of urease -Splits urea to ammonia and CO2 -High urine pH facilitates formation of renal -stones -Magnesium and calcium in the form for struvite and apatite crystals leads to formation of stones - Expression of up to six fimbrial types -Adhesion to uroepithelium - IgA protease
68
Describe the pathogen staphylococcus saprophyticus
- GPC in clusters around 1 micro m diameter - Coagulase negative staphylococcus Asymptomatic coloniser of UT - Associated with UTI in sexually active women, rare in other populations - Identification -Does not utilise mannitol (pink); distinguished from S. aureus (yellow) on mannitol salt agar (MSA) -Reduced susceptibility to novobiocin (reduced or no zone of inhibition). Other CNS are sensitive
69
List the possible treatments of uti
Nitrofurantoin Ciprofloxacin Gentamicin Trimethoprim Cefalexin Amoxicillin Co-amoxiclav
70
Outline nitrofurantoin
Only used for UTI, not used in the later stages of pregnancy, during breast feeding or for infants under 3 months
71
outline ciprofloxacin
Used in complicated infection, but not during pregnancy and used with caution in children
72
Outline gentamicin
Nephrotoxic, IV administration, typically used in combination therapy
73
Outline trimethoprim
Not for enterococcal I infection Not used during pregnancy
74
outline cefalexin
Not for enterococcal infection
75
Outline amoxicillin
Many E. coli now resistant
76
Outline Co-amoxiclav
(amoxicillin and β-lactamase inhibitor clavulanic acid) Broad spectrum, not widely used
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