Recovery of Airborne Aerobic Bacteria and Fungi from Hospitals of Varying Bed Strength in a Tropical Setting

Objectives: Study was undertaken in Chennai, India to 1) determine the impact of hospital bed strength and sampling location on recovery of airborne microorganisms; and 2) characterize microorganisms (aerobic bacteria and fungi) isolated. Methods: Indoor air samples (duplicates) were collected from intensive care units (ICUs), operating rooms (ORs) and wards of six (two 100 bed (group III)) hospitals over one-year period using exposed-plates for time periods of 30 minutes. Sampling media included 5% Sheep Blood agar and MacConkey agar for bacteria and Rose Bengal agar for fungi. Results: A total of 2 ORs and 2 wards from group I, 3 ICUs, 3 ORs and 3 wards from group II, and 4 ICUs, 3 ORs and 8 wards from group III hospitals were sampled. Airborne microbial loads ranged between 46-59 CFU/ plate in ICUs, 17 -26 CFU/ plate in ORs and 63-100 CFU/ plate in wards. Airborne microbial loads varied significantly with sampling locations (p < 0.001); variation in airborne microbial loads with hospital bed strength was statistically insignificant (Kruskal-Wallis test). Coagulase-negative Staphylococci and Pseudomonas sp., and Aspergillus sp. were the predominant bacteria and fungi recovered respectively from air of all the hospitals under study. Conclusion: Appropriate location-specific measures such as regulated temperature-humidity levels and air exchanges need to be implemented to contain their spread.