Table 1 Interpretation and classification of biofilm production based on optical density (OD) values of the tissue culture plate method.

From: Resistance patterns and virulence factors of Pseudomonas aeruginosa in hospitalized patients: A Saudi Arabian study

Biofilm Classification

OD (Optical Density)

Description

Strong Biofilm Producer

4 x ODc < OD

Bacteria that produce a high amount of biofilm.

Moderate Biofilm Producer

2 x ODc < OD ≤ 4 x ODc

Bacteria that produce a moderate amount of biofilm.

Weak Biofilm Producer

ODc < OD ≤ 2 x ODc

Bacteria that produce a weak amount of biofilm.

Non-Biofilm Producer

OD ≤ ODc

Bacteria that do not produce a significant biofilm.

  1. *ODc: Average OD of negative control + 3 × SD (standard deviation) of negative control.
  2. OD: Optical density; ODc: OD cut-off value.
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