Factors affecting the microbiological air quality in a school corridor - a case study

Purpose: Investigation of Indoor Bioaerosol Concentration (IBC) with potential health risks assesment, with dependence on number of present people, temperature and relative humidity (RH) in school corridor space, which remain under-researched spaces. Methods: The impact method (AirIdeal 3P) was used for measurements of IBC including α- and β-hemolytic bacteria, Staphylococcus aureus, mannitol(+)Staphylococci, Pseudomonas aeruginosa, mesophiles, psychrophiles, actinomycetes, fungi. Genetical identification of S. aureus and hemolytic bacteria (MecA gene analysis, 16 S rRNA sequencing, and phylogenetic analysis) were performed. Pearson’s correlation was used to assess the association between student occupancy and IBC, while Spearman’s rank correlation was used to evaluate relationships between microclimatic conditions and IBC (p < 0.05). Results: The highest concentrations of mannitol(+)Staphylococci (2510 CFU m⁻³), S. aureus (1360 CFU m⁻³), and mesophiles (2520 CFU m⁻³) were observed on days with the largest number of students (264). All bacterial groups showed I/O > 1, while fungi showed I/O < 1. Indoors, the highest mean concentration was reached by psychrophiles (1403 CFU m⁻³). Pearson’s correlation was significant for mannitol(+)Staphylococci (r = 0.85), Staphylococcus aureus (r = 0.79), and mesophiles (r = 0.76), showing the dynamic and positive relationship between student number and IBC. MecA gene and 16 S rRNA analysis confirmed the presence of S. aureus. 16 S rRNA and phylogenetic analysis of β-hemolytic bacteria revealed the Staphylococcus (33%), Bacillus (33%), Corynebacterium (20%) as dominant genera. Spearman’s rank correlation revealed a weak correlation between meteorological factors and IBC. Conclusion: The presence of potential airborne pathogens with proven internal sources underscores the need for detailed monitoring of corridor air quality.