Indoor air microbial counts in dormitory of nursing students, Bangkok

Background: Most medical and nursing students live in institute dormitories located in a university hospital where a variety of biological and chemical hazards are used and probably diffuse into the dormitory environments. Objectives: This study aimed to investigate bacterial and fungal counts, and microbial groups in a dormitory of nursing students in Bangkok, Thailand. Methods: Two-time assessments of bacterial and fungal counts in indoor air samples collected from a dormitory of nursing students including 8 floors with 95 rooms were carried out. A total of 380 indoor air samples (190 for bacteria and 190 for fungi) were collected from all dormitory rooms using a BioStage Impactor and 48 outdoor air samples were collected for comparison. Air samples were collected twice, i.e., in the first month and the third month of the study. Results: The mean bacterial counts were 151 ± 109 cfu/m³ and 158 ± 92 cfu/m³ and those of fungal counts were 374 ± 273 cfu/m³ and 363 ± 257 cfu/m³ from the first and the second assessment. The lower floors of the dormitory (1-4 floors) had significantly higher levels of bacterial and fungal counts in both assessments when compared with the higher floors of the dormitory (5-8 floors) (P < 0.001). The percentages of bacterial and fungal counts with > 300 cfu/m³ in the lower floors were significantly higher than those in the higher floors in the first and the second assessments (P < 0.05 and P < 0.001, respectively). Additionally, the most common isolated bacteria and fungi were Staphylococcus spp., and Aspergillus spp., respectively. Conclusion: This study reveals that the lower floors of the dormitory had significantly higher levels of bacterial and fungal counts when compared with the higher floors of the dormitory from both assessments. Most isolated microbes do not generally present a health hazard but high loads may trigger allergic reactions in susceptible hosts.