Interpretation of Urine culture

Views:
 
Category: Education
     
 

Presentation Description

Interpretation of Urine culture

Comments

Presentation Transcript

Interpretation of urine cultures Cumitech Guidelines incorporated:

Dr.T.V.Rao MD Interpretation of urine cultures Cumitech Guidelines incorporated 12/15/2011 Dr.T.V.Rao MD 1

Pathophysiology of urinary tract infection:

Pathophysiology of urinary tract infection Uncomplicated urinary tract infection : Bacterial or yeast infection in a structurally and neurologically normal urinary tract Complicated urinary tract infection : Bacterial or yeast infection in a urinary tract with functional or structural abnormalities

Risk factors in complicated urinary tract infection:

Risk factors in complicated urinary tract infection Indwelling catheters Urinary calculi Neurogenic bladder Prostatic enlargement Uterine prolapse Urologic instrumentation or surgery Renal transplantation Diabetes mellitus

Urinary Tract Specimens:

Urinary Tract Specimens First-voided morning urine optimal (generally bacteria have been proliferating in bladder urine for several hours) Midstream urine specimens (initially voided urine contains urethral commensals) Indwelling catheters (freshly placed, urine aspirated by needle inserted into catheter) (Foley catheter tips not acceptable) Straight catheter specimens Suprapubic aspirates (infants or children, recovery of anaerobes) Cystoscopic collection of urine Contamination-free specimen 12/15/2011 Dr.T.V.Rao MD 4

Collection of Urine Specimens:

Urine collected in sterile specimen container must be processed within 2 hours, or refrigerated and processed within 24 hours Urine collected in sterile specimen container with borate preservative should be processed within 24 hours (no refrigeration required) Collection of Urine Specimens 12/15/2011 Dr.T.V.Rao MD 5

Prompt transpiration needed:

Transport to lab as soon as possible Urine should be cultured within 2 hours or be refrigerated for up to 24 hours Microorganisms grow very rapidly in urine at room temperature This could give a false positive culture result Prompt transpiration needed 12/15/2011 Dr.T.V.Rao MD 6

Specimen Inoculations:

Specimen Inoculations All cultures processed by Semiquantitative method a loop of standard dimension of approximately known volume is inoculated into selected culture plate In general a loop of SWG – 28 with a diameter of 3.26 mm internal diameter which can hold a drop of water or urine 0.004 ml. After inoculation the culture plates are incubated at 37 0 c extending to > 18 hours are read The colony counts are made, as each colony corropsdes to number of viable bacteria per ml of urine Dr.T.V.Rao MD 7 12/15/2011

Inoculation of Urine:

Inoculation of Urine Inoculation of urine for quantitative culture (colony forming units →cfu’s ) performed with a calibrated 0.001 mL and 0.01 mL plastic or wire loop Sheep blood agar (SBA) utilized for quantitative urine culture With 0.001 ml loop, 1 colony on SBA equivalent to 1,000 cfu’s per mL of urine With 0.01 ml loop, 1 colony on SBA equivalent to 100 cfu’s per mL of urine MacConkey agar utilized as selective differential agar for gram-negative bacteria , Colistin nalidixic acid agar as selective agar for gram-positive bacteria, and chocolate agar for fastidious gram-negative bacteria ( Haemophilus ) 12/15/2011 Dr.T.V.Rao MD 8

Common Uropathogens:

Common Uropathogens 12/15/2011 Dr.T.V.Rao MD 9 Escherichia coli Other Enterobacteriaceae ( Klebsiella , Enterobacter , Proteus , Citrobacter ) Pseudomonas aeruginosa Enterococcus Staphylococcus saprophyticus Staphylococcus aureus Streptococcus agalactiae (group B ) Candida

Uncommon Uropathogens:

Uncommon Uropathogens 12/15/2011 Dr.T.V.Rao MD 10 Corynebacterium urealyticum Hemophilus influenzae and H . parainfluenzae Blastomyces dermatitidis Neisseria gonorrhaeae Mycobacterium tuberculosis

Counting the colonies:

With 0.001 ml loop, 1 colony on SBA equivalent to 1,000 cfu’s per mL of urine With 0.01 ml loop, 1 colony on SBA equivalent to 100 cfu’s per mL of urine Counting the colonies Dr.T.V.Rao MD 11 12/15/2011

Interpretation of Urine Cultures: General Guidelines:

A single species of Enterobacteriaceae recovered at >10 5 cfu’s/mL urine: with patients symptomatic for urinary tract infection, 95% probability of true bacteriuria Interpretation of Urine Cultures: General Guidelines 12/15/2011 Dr.T.V.Rao MD 12

What is Significant bacteriuria :

Significant bacteriuria in an asymptomatic patient is 100,000 or more colonies per milliliter of urine from a midstream, clean-catch specimen; yet, a colony count of 200 Escherichia coli per ml may be significant in a midstream male void or catheterized female . About 95% of all positive UTI cultures will produce essentially pure cultures if urine is collected carefully and the media inoculated promptly . What is Significant bacteriuria Dr.T.V.Rao MD 13 12/15/2011

What can be a significant count:

A single species of Enterobacteriaceae recovered at 10 4 -10 5 cfu’s/mL urine: with patients symptomatic for urinary tract infection, 33% probability of true bacteriuria What can be a significant count Dr.T.V.Rao MD 14 12/15/2011

Urine Cultures:

Urine Cultures Organisms/ml --- very important! <10,000 (Rare) May indicate contamination Lab usually does not identify the organisms Generally not treated unless there is a single organism and patient has S&S 12/15/2011 Dr.T.V.Rao MD 15

Urine Cultures…:

> 100,000 organisms/ml (Many) Usually indicates an infection Patient most likely will have S&S Most often will be treated with antibiotic appropriate for that organism Urine Cultures… 12/15/2011 Dr.T.V.Rao MD 16

Cumitech Guidelines for Interpretation of Routine Urine Cultures:

One isolate at > 10 4 : Full ID and Susceptibility One or two gram-negative isolates at > 10 5 and other isolates at least 10X less : Full ID and Susceptibility of gram-negative isolates Cumitech Guidelines for Interpretation of Routine Urine Cultures Dr.T.V.Rao MD 17 12/15/2011

Cumitech Guidelines for Interpretation of Routine Urine Cultures1:

Cumitech Guidelines for Interpretation of Routine Urine Cultures 1 One isolate at > 10 4 : Full ID and Susceptibility One or two gram-negative isolates at > 10 5 and other isolates at least 10X less: Full ID and Susceptibility of gram-negative isolates Other patterns of isolates at > 10 4 : Presumptive ID only Ignore mixed urethral flora at < 10 4 1 Clarridge, Johnson, Pezzlo, and Weissfeld, ASM Cumitech 2B, November 1998. 12/15/2011 Dr.T.V.Rao MD 18

HOW TO REPORT URINE CULTURES: Cumitech Recommendations:

HOW TO REPORT URINE CULTURES: Cumitech Recommendations Negative urines (no growth) 0.01 ml inoculum Sterile or < 100 CFU/ml OR No growth of > 100 CFU/ml 0.001 ml inoculum Sterile or < 1000 CFU/ml OR No growth of > 1000 CFU/ml 12/15/2011 Dr.T.V.Rao MD 19

Reading the Culture Plates:

Reading the Culture Plates A true infection in the absence of prior antibiotic therapy the number of bacteria is likely to be at least 10 5 or more. Contaminated specimens present with colony counts <10 4, however even less than 10 3 On several occasions the colonies are diverse species Several studies prove counts >10 4 to be considered as presence of Urinary tract infection with the supporting clinical history On some occasions more than one pathogen is isolated but should be processed for all practical purposes eg E.coli along with Streptococcus fecalis On few occasions even counts 10 3 are proved significant Dr.T.V.Rao MD 20 12/15/2011

Interpretation of Enterobacteriaceae:

A single species of Enterobacteriaceae recovered at >10 5 cfu’s/mL urine: with patients symptomatic for urinary tract infection, 95% probability of true bacteriuria A single species of Enterobacteriaceae recovered at 10 4 -10 5 cfu’s/mL urine: with patients symptomatic for urinary tract infection, 33% probability of true bacteriuria Interpretation of Enterobacteriaceae Dr.T.V.Rao MD 21 12/15/2011

Interpretation of Enterobacteriaceae:

A single species of Enterobacteriaceae recovered at >10 5 cfu’s/mL urine: with patients symptomatic for urinary tract infection, 95% probability of true bacteriuria A single species of Enterobacteriaceae recovered at 10 4 -10 5 cfu’s/mL urine: with patients symptomatic for urinary tract infection, 33% probability of true bacteriuria Interpretation of Enterobacteriaceae Dr.T.V.Rao MD 22 12/15/2011

Gram positives and fungi the counts may be <105:

Gram-positive, fungal, and fastidious uropathogens often present in lower numbers (10 4 -10 5 cfu’s/mL urine) Urethral commensals recovered at <10 4 cfu’s/mL urine Gram positives and fungi the counts may be <10 5 12/15/2011 Dr.T.V.Rao MD 23

Cumitech Guidelines for Interpretation of Routine Urine Cultures1:

Other patterns of isolates at > 10 4 : Presumptive ID only Ignore mixed urethral flora at < 10 4 1 Clarridge, Johnson, Pezzlo, and Weissfeld, ASM Cumitech 2B, November 1998. Cumitech Guidelines for Interpretation of Routine Urine Cultures 1 Dr.T.V.Rao MD 24 12/15/2011

Cumitech Guidelines for Interpretation of Special or uncommon Urine Cultures1:

One or two isolates at > 10 2 to 10 5 : Full ID and Susceptibility is essential before confirmed as uncommon isolates 1 Clarridge, Johnson, Pezzlo , and Weissfeld , ASM Cumitech 2B, November 1998. Cumitech Guidelines for Interpretation of Special or uncommon Urine Cultures 1 Dr.T.V.Rao MD 25 12/15/2011

Reporting of negative urine cultures:

Negative culture results showing no bacterial growth are available after 24 hours. Positive results require 24-72 hours to complete identification of the number and type of bacteria found Reporting of negative urine cultures Dr.T.V.Rao MD 26 12/15/2011

Asymptomatic Bacteriuria:

Asymptomatic Bacteriuria 12/15/2011 Dr.T.V.Rao MD 27 Presence of uropathogens by culture without signs or symptoms of urinary tract infection Clinically significant (should be treated) with preschool children (? vesicoureteral reflux, congenital urinary tract anomaly), pregnant women, and adults with obstructive uropathy Without clinical significance (should not be treated) for adults in absence of urinary tract obstruction

When to do an antibiotic sensitivity testing on Urine Isolate?:

When to do an antibiotic sensitivity testing on Urine Isolate? Follow laboratory guidelines for susceptibility testing of isolates in which a definitive ID and AST is recommended, according to Cumitech, CMPH, MCM, IDSA, other guidelines. That would include “significant CFU/ml” of : Enterobacteriaceae P. aeruginosa Enterococcus sp. S. aureus Significant CoNS, except S. saprophyticus Others, including yeast, upon request or if SOP’s have been set up in accordance with CLSI Guidelines of Best practices 12/15/2011 Dr.T.V.Rao MD 28

PowerPoint Presentation:

Created by Dr.T.V.Rao MD for ‘ e’Learning ” resources for Microbiologists in the Developing World Email doctortvrao@gmail.com Dr.T.V.Rao MD 29 12/15/2011

authorStream Live Help