A method development for bacterial quantification and qualification in occupational exposure

Area of Science:

• Occupational health
• Analytical chemistry
• Microbiology

Background:

• Bacterial contamination is a concern in occupational settings, with airborne colony-forming units indicating exposure but not bacterial origin.
• Current methods for assessing airborne bacteria lack specificity regarding bacterial species identification.

Purpose of the Study:

• To apply Fourier transform infrared spectroscopy (FTIR) for identifying bacterial species in airborne samples.
• To validate FTIR as a quantitative and qualitative method for assessing airborne bacteria in an occupational setting, specifically a nurses' station.

Main Methods:

• Airborne samples from a nurses' station (n=40) were collected using the National Institute of Occupational Safety and Health 0800 method.
• Bacterial strains were identified using diagnostic gallery tests and FTIR.
• FTIR data were analyzed using principal component analysis (PCA) for bacterial classification and quantification, with specific focus on Staphylococcus aureus.

Main Results:

• FTIR, particularly with second derivatization in the 1200-1500 cm⁻¹ range, effectively discriminated bacterial Gram-type via PCA.
• The 900-1200 cm⁻¹ region modeling differentiated Gram-negative bacteria in airborne samples.
• Validated FTIR spectral bands (2850 and 2906 cm⁻¹) accurately assessed Staphylococcus aureus contamination levels, correlating well with commercial counting methods.

Conclusions:

• Fourier transform infrared spectroscopy is a functional and validated technique for assessing airborne quality in occupational exposures.
• FTIR provides a reliable alternative for both quantitative and qualitative analysis of bio-aerosols, offering species-level identification.
• This study recommends FTIR as a valuable tool for occupational health monitoring and environmental microbiology.