Gram Mixture Control Audit

Screen mixed Gram-stain cell-color observations with a supplied minority criterion and control validity; mixture does not distinguish contamination from Gram variability.

Description

A Gram-stain sample can contain both purple and pink cell observations.

A Gram-stain sample can contain both purple and pink cell observations. A minority-fraction criterion detects a mixed color pattern only when controls are declared valid.^[1]

Screen mixed Gram-stain cell-color observations with a supplied minority criterion and control validity; mixture does not distinguish contamination from Gram variability.

When to use Gram Mixture Control Audit

Use this tool to screen mixed Gram-stain cell-color observations with a supplied minority criterion and control validity; mixture does not distinguish contamination from Gram variability.

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 Gram Mixture Control Audit 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 purpleCells, pinkCells, minimumMinorityFraction, controlsPassed using the field table and calculation rules, then run the tool.
Read purpleFraction, pinkFraction, mixedReactionFlag, interpretable. 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
purpleCells	Purple cells	integer; minimum: 0	Required
pinkCells	Pink cells	integer; minimum: 0	Required
minimumMinorityFraction	Minimum minority fraction	number; minimum: 0; maximum: 1	Required
controlsPassed	Controls passed	boolean	Required

Enter nonnegative integer color counts with positive combined count and a minority threshold from 0 through 0.5. The tool reports both fractions, interpretable from the control flag and the gated inclusive mixture flag. Threshold zero can flag a one-color sample when controls pass.

mixed = controlsPassed AND min(purpleFraction,pinkFraction)≥minimumMinorityFraction

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

Output field	Meaning	Value type
purpleFraction	Purple fraction	number
pinkFraction	Pink fraction	number
mixedReactionFlag	Mixed reaction flag	boolean
interpretable	Interpretable	boolean

json

{
  "input": {
    "purpleCells": 30,
    "pinkCells": 70,
    "minimumMinorityFraction": 0.1,
    "controlsPassed": true
  },
  "output": {
    "purpleFraction": 0.3,
    "pinkFraction": 0.7,
    "mixedReactionFlag": true,
    "interpretable": true
  }
}

Limitations and assumptions

A mixture does not distinguish contamination from Gram variability or technical effects. The controls are supplied rather than checked, and counts do not identify an organism or sample purity.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. 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 Viable Nonculturable Discordance: Screen discordance between viability assay and matched culturability; this pattern alone does not prove a VBNC state. For a complementary task, use TSI Slant Butt Logic: Interpret valid TSI reaction pairs with acid-butt inference under sulfide blackening; not a species identification.

References

Gram Mixture Control Audit — tool.io

Similar or alternative tools

Viable Nonculturable Discordance
Screen discordance between viability assay and matched culturability; this pattern alone does not prove a VBNC state.
TSI Slant Butt Logic
Interpret valid TSI reaction pairs with acid-butt inference under sulfide blackening; not a species identification.