Bactericidal Survival Endpoint

Find the first dilution meeting a caller-defined bactericidal kill fraction based on survivor counts, rather than merely recording MBC.

Description

A bactericidal endpoint compares survivor counts with the starting population using an explicit required kill fraction.

A bactericidal endpoint compares survivor counts with the starting population using an explicit required kill fraction. It is distinct from a no-growth MIC endpoint.^[1]

Find the first dilution meeting a caller-defined bactericidal kill fraction based on survivor counts, rather than merely recording MBC.

When to use Bactericidal Survival Endpoint

Use this tool to find the first dilution meeting a caller-defined bactericidal kill fraction based on survivor counts, rather than merely recording MBC.

Prepare the sample, count, growth or assay measurements requested by this tool. Confirm units, sampling periods and reporting bases; supply independently established comparison criteria where requested.

How to use Bactericidal Survival Endpoint and understand its results

Prepare the sample, count, growth or assay measurements requested by this tool. Confirm units, sampling periods and reporting bases; supply independently established comparison criteria where requested.
Enter concentrations, survivingCfu, initialCfu, minimumKillFraction using the field table and calculation rules, then run the tool.
Read killFractions, mbcConcentration, endpointFound, rightCensored. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
concentrations	Concentrations	list of number	Required
survivingCfu	Surviving cfu	list of number	Required
initialCfu	Initial cfu	integer; minimum: 1	Required
minimumKillFraction	Minimum kill fraction	number; minimum: 0; maximum: 1	Required

Enter increasing positive concentrations and aligned nonincreasing integer survivors within the positive initial CFU. Choose minimum kill fraction in [0,1]. Return every kill fraction, the first qualifying concentration and endpointFound. No match returns a zero concentration placeholder and rightCensored true.

killFraction_i=1−survivors_i/initial; endpoint=first killFraction≥minimum

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
killFractions	Kill fractions	list of number
mbcConcentration	Mbc concentration	number
endpointFound	Endpoint found	boolean
rightCensored	Right censored	boolean

json

{
  "input": {
    "concentrations": [
      1,
      2,
      4
    ],
    "survivingCfu": [
      1000,
      100,
      10
    ],
    "initialCfu": 100000,
    "minimumKillFraction": 0.999
  },
  "output": {
    "killFractions": [
      0.99,
      0.999,
      0.9999
    ],
    "mbcConcentration": 2,
    "endpointFound": true,
    "rightCensored": false
  }
}

Limitations and assumptions

The caller chooses the criterion and assay protocol. Detection limits, uncertainty and recovery are not modeled, and this observed endpoint does not establish a clinical treatment effect.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Growth Inhibition MIC Endpoint: Derive the observed MIC from a monotone dilution-growth series, preserving below- and above-range censoring. For a complementary task, use Observed Decimal Reduction Time: Estimate a measured D value from positive viable counts and exposure time under log-linear death assumptions.

References

Bactericidal Survival Endpoint — tool.io

Similar or alternative tools

Growth Inhibition MIC Endpoint
Derive the observed MIC from a monotone dilution-growth series, preserving below- and above-range censoring.
Observed Decimal Reduction Time
Estimate a measured D value from positive viable counts and exposure time under log-linear death assumptions.