Overview
Urine culture is a quantitative (or semi-quantitative) bacteriology pathway that estimates microbial burden in urine and identifies isolates meeting institutional significance criteria.
Classification
| Specimen type | Interpretation emphasis | Common pitfall |
|---|---|---|
| Midstream clean-catch | Count + purity | Calling mixed flora infection |
| Indwelling catheter | Local catheter algorithms | Ignoring colonization vs infection context |
| Straight catheter | Often higher interpretive weight | Delay before plating |
| Bag/pediatric | Often limited usefulness | Over-interpreting mixed growth |
Morphologic Features
Plate reading records colony morphologies and approximate densities. Predominant single morphology differs interpretively from three or more equal types at similar density.
Laboratory Characteristics
- Calibrated-loop or automated quantitative inoculation
- Local media menu for urine culture
- Workup algorithms tied to count/purity
- Contamination/mixed-flora report comments
Reference Intervals
CFU/mL significance thresholds, number of isolates worked up, and susceptibility-testing triggers are institutional. Verify local SOP; do not memorize one universal cutoff as policy.
Clinical and Laboratory Significance
Valid urine cultures support UTI evaluation when collection quality and quantitative criteria align. Contaminated cultures should be labeled as such rather than fully identified by default.
Differential Considerations
Differentiate true bacteriuria patterns from periurethral contamination and from delay-related overgrowth during prolonged transport.
Comparison Tables
Urine plate reading cues
| Pattern | Typical lab cue | Reporting tendency (local SOP) |
|---|---|---|
| Single morphology, significant count | Work up per local cutoff | ID ± AST per algorithm |
| Mixed equal morphologies | Contamination likely (MSU) | Mixed flora / recollect language |
| No growth | Below detection of method | No growth in X hours |
Classification Frameworks
Not applicable.
Laboratory Notes
- Hedge colony-count cutoffs and media menus as local
- No treatment or dosing language in urine culture reports
- Document specimen type on every report
References
Authoritative textbooks, guidelines, and reviews supporting this reference entry. Verify reference intervals, critical limits, and reflex criteria against institutional protocols and current guideline editions.
Textbooks
- Forbes BA, Sahm DF, Weissfeld AS. Bailey & Scott's Diagnostic Microbiology. 15th ed. Elsevier; 2020.
- Mahon CR, Lehman DC, Manuselis G. Textbook of Diagnostic Microbiology. 6th ed. Elsevier; 2018.
- Carroll KC, Hobden JA, Miller S, et al. Jawetz, Melnick, & Adelberg's Medical Microbiology. 28th ed. McGraw-Hill; 2019.
- Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology. 9th ed. Elsevier; 2021.
CLSI and Professional Guidelines
- Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing. CLSI document M100 (verify current edition and institutional adoption).
- Centers for Disease Control and Prevention / NIH. Biosafety in Microbiological and Biomedical Laboratories (BMBL). Current edition (verify institutional adoption).
Frequently Asked Questions
Common questions about using this Urine Culture foundational topics Medical Laboratory Library reference in Medical Laboratory Science education.
What is the Urine Culture laboratory reference?
Urine Culture is a Foundational Topics entry in the LabPedia Medical Laboratory Library, written for Medical Laboratory Science reference lookup.
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Can reference details vary between laboratories?
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