Development of Quality Control Ranges for Biocide Susceptibility Testing

Area of Science:

• Microbiology
• Antimicrobial Resistance
• Laboratory Science

Background:

• Quality control (QC) is essential for laboratory test validation.
• Currently, no standardized QC strains or ranges exist for biocide susceptibility testing (BST).
• This lack of standardization hinders the reliable assessment of biocide efficacy.

Purpose of the Study:

• To develop and establish quality control (QC) ranges for biocide susceptibility testing (BST).
• To validate the use of specific reference strains and biocides for BST QC.
• To provide a foundation for the future validation of BST methods.

Main Methods:

• An interlaboratory trial involving eleven laboratories was conducted.
• Four reference strains (Staphylococcus aureus, Enterococcus hirae, Escherichia coli, Pseudomonas aeruginosa) and four biocides (benzalkonium chloride, chlorhexidine, octenidine, polyhexanide) were used.
• The broth microdilution method and RangeFinder software were employed to determine QC ranges.

Main Results:

• QC ranges were successfully defined for most reference strain-biocide combinations.
• The development of QC ranges for Pseudomonas aeruginosa with chlorhexidine and polyhexanide was not feasible due to biocide solubility issues.
• The established QC ranges typically span three to five dilution steps.

Conclusions:

• The establishment of these QC ranges represents a significant step towards the validation of biocide susceptibility testing (BST).
• These ranges will enhance the reliability and reproducibility of laboratory biocide efficacy assessments.
• Further research may be needed to address limitations, such as biocide solubility for specific strains.