Culture and Sensitivity Report Format: Sample and Guide

A culture and sensitivity (C&S) report tells the doctor two things: whether a pathogen grew from the specimen, and which antibiotics are likely to work against it. The format matters because the report is read quickly, often on a phone, by someone deciding on treatment. This guide gives a complete sample urine C&S report you can copy, a field-by-field table of what to write and common mistakes, and explains the parts most report formats leave out: what S, I, SDD and R mean, how to report colony counts, what to write for no growth, mixed growth and contamination, preliminary versus final reports, and cascade reporting.

Starter content. Colony-count thresholds, wording and antibiotic panels below are common conventions. Your laboratory's SOP, reviewed by your microbiologist or pathologist, decides the actual format, and interpretation follows the CLSI or EUCAST document your lab has adopted. Every report is authorised by the lab's pathologist.

What a culture and sensitivity report contains

• Header: laboratory name, address and accreditation details if any; report number; page numbering.
• Patient and request: name, age, sex, patient ID, referring doctor, clinical details (for example "dysuria, on no antibiotics").
• Specimen: type and collection method (midstream urine, catheter urine, pus swab from a named site, blood culture set), collection date and time, receipt date and time.
• Microscopy (optional): Gram stain or wet-mount findings, pus cells per high-power field.
• Culture: incubation conditions and duration, growth result.
• Organism(s): identification of each significant isolate with its colony count or semi-quantitative growth.
• Antimicrobial susceptibility: for each organism, the antibiotics tested, the method (disc diffusion zone in mm, or MIC in µg/mL) and the interpretation.
• Comments: cascade footnote, contamination note, advice to repeat, critical-result communication.
• Interpretive standard: which document the breakpoints come from, as adopted by the lab.
• Sign-off: the authorising pathologist or microbiologist, date and time; status (preliminary or final).

Sample urine culture and sensitivity report

Sample data: fictional laboratory, patient and doctor. Zone sizes and interpretations are illustrative; interpretation follows the breakpoints your laboratory adopts.

To print this format, use your browser's Print command (Ctrl+P) on this page. A real signed report with a live QR check is on the sample report page.

Field-by-field: how to fill each section

What S, I, SDD and R mean

The interpretation turns a measurement (a zone diameter or an MIC) into a category by comparing it with a breakpoint for that organism, antibiotic and method.

• S, Sensitive (Susceptible): the organism is inhibited by concentrations usually reached with the standard dose; the antibiotic is likely to work.
• I, Intermediate: the result sits between the S and R breakpoints. Under CLSI, it means the drug may work where it concentrates (for example in urine) or at a higher dose, and it is a buffer against technical variation. EUCAST has, since 2019, used "I" to mean susceptible, increased exposure: the drug works if given at a higher dose or by a route that increases exposure. Either way, "intermediate" is not "weakly sensitive" and should not be read as a second-best choice.
• SDD, Susceptible-dose dependent (a CLSI category for some drug–organism pairs): the drug is likely to work only with a higher dose or more frequent dosing.
• R, Resistant: the organism is not inhibited by achievable concentrations; the drug is unlikely to work.

Breakpoints are published by CLSI (document M100) and EUCAST and revised regularly; the lab chooses one standard, keeps to its current edition and states it on the report. Do not mix standards on one report.

Colony counts: how to report them

For urine, report the count in colony-forming units per mL (CFU/mL). A count of ≥ 10⁵ CFU/mL of a single organism in a clean-catch midstream urine is the traditional threshold for significant bacteriuria, but lower counts can be significant in symptomatic patients, catheter specimens and some organisms, and labs adopt different cut-offs by specimen type. Common presets are ≥ 10⁵ CFU/mL, 10⁴–10⁵ CFU/mL and < 10⁴ CFU/mL. For swabs, pus and sputum, semi-quantitative terms (scanty, moderate, heavy) are usual. Whatever the convention, the lab's SOP sets the thresholds, and the report should say whether a count is considered significant.

No growth, mixed growth and contamination: what to write

• No growth: "No growth after 48 hours of aerobic incubation." Always state the duration, and for blood cultures the full incubation period.
• Mixed growth: three or more organisms in a urine culture usually suggest contamination during collection. A common wording is "Mixed growth of three or more organisms, suggestive of contamination. Please send a fresh clean-catch midstream sample if clinically indicated." Sensitivities are usually not reported.
• Contaminated: where the specimen is clearly contaminated (for example skin flora in a single blood-culture bottle with other bottles negative), say so and advise on repeat collection as your SOP directs.
• Commensals: for non-sterile sites, name the normal flora rather than reporting each organism ("Normal upper-respiratory flora").

Preliminary and final reports

A culture takes time. A preliminary report lets the doctor act early, for example "Gram-negative bacilli isolated; identification and sensitivity to follow", or, for blood cultures, "No growth at 48 hours; incubation continuing". The preliminary report must be clearly marked PRELIMINARY so it is never mistaken for the final. The final report, with identification and the full susceptibility table, follows on the same order and is signed. If the final changes something the doctor may have acted on, call them.

Cascade reporting: which antibiotics to show

Labs often test more antibiotics than they report. In cascade (selective) reporting, broader-spectrum or reserve agents are shown only when the first-line agents are resistant. For example, if a urinary E. coli is sensitive to nitrofurantoin, fosfomycin, amoxicillin-clavulanate and cefuroxime, the lab may withhold ceftriaxone, piperacillin-tazobactam and meropenem from the report, with the footnote "Additional antibiotics were tested; results available on request." This supports antimicrobial stewardship without hiding information: the results remain in the lab record and count in the lab's cumulative antibiogram. Decide the tiers with your microbiologist and infection-control team.

Variations: pus, blood, sputum and stool culture report formats

Pus and wound swab

Name the site precisely ("pus from right foot ulcer"), include Gram stain findings and use semi-quantitative growth. Use the panel for the organism group isolated (for example a Staphylococcus panel with a cefoxitin screen for methicillin resistance). Note if anaerobic culture was not performed.

Blood culture

Report the number of sets and bottles, the volume if recorded, the time to positivity, the Gram stain of the positive bottle (often phoned to the doctor as a critical result), the organism and susceptibility, and for negative cultures "No growth after 5 days of incubation" (or your system's duration). Interpret a single bottle with a skin commensal cautiously.

Sputum

State the specimen quality (for example by the pus-cell and squamous-cell counts per low-power field); a saliva-like specimen is often rejected rather than reported. Report pathogens with semi-quantitative growth and normal flora in words.

Stool

Report the enteric pathogens the lab looks for (for example Salmonella, Shigella, Vibrio) and state that others were not sought. Susceptibility is usually reported only for selected pathogens and drugs.

How to read a culture and sensitivity report

For doctors and patients reading the report:

1. Check the specimen and collection details: right patient, right site, collected before antibiotics?
2. Read the growth line: no growth, a significant organism, or likely contamination.
3. For each organism, look at the interpretation column, not the numbers: S means likely to work, R unlikely.
4. Read the comments: suppressed antibiotics, advice to repeat, or a critical-result note.
5. Check whether the report is preliminary or final.

A culture report supports treatment decisions; it does not make them. Patients should always discuss the report with their doctor before starting or changing any antibiotic.

Making the format automatic

Typing this format by hand invites the mistakes in the table above. In PathLab Software's microbiology lab software, the specimen, incubation, growth, isolates and colony counts are fields; picking an AST panel fills the antibiotics in your order; S/I/R fills in from breakpoints your lab enters (none are shipped), with every override audited; cascade suppression and the footnote are automatic; and the preliminary and final reports come from the same culture record. Each finalised isolate also counts in a quarterly cumulative antibiogram built from your own results. Signed reports go out with QR verification; see the WhatsApp lab reports guide for delivery. Microbiology is included in the Complete and Network plans; see pricing.

Report cultures with panels, cascade and a quarterly antibiogram: see microbiology lab software.

Questions people ask

What is the format of a culture and sensitivity report?

A culture and sensitivity report lists the specimen with collection and receipt times, incubation, the growth result, each organism with its colony count, and an antibiotic table per organism with zone size or MIC and the interpretation in words. It ends with comments, the interpretive standard used and the pathologist's signature.

What does "sensitive" mean in a culture report?

Sensitive (susceptible) means the organism was inhibited by antibiotic concentrations usually reached with a standard dose, so that antibiotic is likely to work. The category comes from comparing the zone size or MIC with breakpoints the laboratory adopted. Treatment decisions remain with the doctor.

What does S and R mean in a culture report?

S stands for sensitive or susceptible: the antibiotic is likely to work at the standard dose. R stands for resistant: the antibiotic is unlikely to work. I (intermediate) and SDD (susceptible-dose dependent) sit between them and usually mean a higher dose or a site where the drug concentrates is needed.

What is the format of a urine culture report?

A urine culture report states the collection method (midstream or catheter), collection and receipt time, microscopy, incubation, the growth result with organism and colony count in CFU/mL, the antibiotic table with interpretations, comments and the signature. No-growth reports should state the incubation time.

What is cascade reporting in microbiology?

Cascade or selective reporting means the lab tests a full antibiotic panel but reports broader-spectrum or reserve antibiotics only when first-line agents are resistant, adding a note that more results are available on request. It supports antimicrobial stewardship; suppressed results stay in the lab record.

How long does a culture and sensitivity report take?

A no-growth urine culture is commonly reported after 24 to 48 hours, and a positive culture with sensitivity in 48 to 72 hours. Blood cultures are incubated for several days before being reported negative. Labs often issue a preliminary report first; the SOP sets the times.