Cleanliness in context: reconciling hygiene with a modern microbial perspective

Area of Science:

• Microbial Ecology
• Public Health
• Dermatology

Background:

• Hygiene is traditionally linked to cleanliness and health.
• The germ theory of disease led to hygiene being conflated with sterilization.
• Current hand hygiene studies often use bacterial load reduction as a proxy for pathogen transmission.

Purpose of the Study:

• To critically evaluate the prevailing concept of hygiene in light of microbial ecology research.
• To propose a revised definition of hygiene that accounts for the human microbiota.

Main Methods:

• Review of existing literature on hygiene, particularly hand hygiene studies.
• Analysis of findings from recent microbial ecology research on the human skin microbiota.

Main Results:

• Most hygiene studies measure bulk bacterial reduction, not specific pathogen reduction.
• Human skin hosts a diverse microbiota, with many beneficial or commensal microbes.
• The skin microbiota is generally beneficial and rarely pathogenic.

Conclusions:

• Defining hygiene solely by microbial reduction is insufficient and potentially detrimental.
• A more accurate definition of hygiene is needed to distinguish between pathogenic and non-pathogenic microbes.
• Proposed definition: Hygiene encompasses actions reducing pathogenic microorganism transmission to prevent disease.