High bacterial load of indoor air in hospital wards: the case of University of Gondar teaching hospital, Northwest Ethiopia.

Background: The air inhaled by people is abundantly populated with microorganisms which also are called bioaerosols. Bioaerosols is a colloidal suspension, formed by liquid droplets and particles of solid matter in the air, whose components contain or have attached to them viruses, fungal spores and conidia, bacterial endospores, plant pollen and fragments of plant tissues. They account for 5-34 % of indoor air pollution.

Methods: A cross-sectional study was conducted to assess the bacteriological concentration and to identify specific species of bacteria in the indoor air of Gondar University teaching hospital. Air samples were taken from 14 randomly selected wards. Bacterial measurements were made by passive air sampling technique i.e., the settle plate method. In each ward five Petri dishes were exposed for 30 and 60 min in the morning and afternoon. Bacteria were collected on nutrient agar and blood agar media. Both quantitative and qualitative analyses were conducted. The quantitative analysis was mainly conducted to determine bacterial load or number of bacteria in the indoor air. Bacterial load was enumerated as colony forming units. Qualitative analysis was conducted to identify specific species of bacteria. For this study we have selected Staphylococcus aureus and Streptococcus which had high public health concern. Mannitol test was used to isolate Staphylococcus aureus, whereas Bacitracin test was conducted to isolate Streptococcus pyogene.

Result: The result of this study indicated that the highest bacterial load which was 1468 CFU/m(3) has been recorded at 2:00 PM in Ward C at 60 min exposure time and the lowest bacterial concentration (i.e., 480 CFU/m(3)) was recorded at 8:00 AM in physiotherapy ward. Based on the result bacterial concentration of indoor air of Gondar University teaching hospital was found between 480 and 1468 CFU/m(3). The result of one way ANOVA showed that the highest mean bacterial concentration (1271.00 CFU/m(3)) was found in Medical ward and the least (583.25 CFU/m(3)) concentration was found in ward D and the grand total average concentration was 878.43 CFU/m(3). Favorable conditions for growth and multiplication of bacteria like temperature (26.5-29.5 °C), humidity (64.5-85 %), presence of unhygienic attached toilets, poor waste management system and poor ventilation system were observed during the survey. Staphylococcus aureus was identified in 10 wards and Streptococcus pyogenes was isolated in 8 hospital wards.

Conclusions: Compared with different indoor air biological standards, higher concentration of indoor air bacterial load was found in Gondar University teaching hospital. The higher bacterial load may be due to temperature, humidity, presence of unhygienic attached toilets, poor waste management system and poor ventilation system. Therefore, attention must be given to control those environmental factors which favor the growth and multiplication of microbes in indoor environment. In addition, also the ventilation condition, cleanliness of toilets, sweeping methods and waste disposal system of the compound should be improved.