Microbiological Surveillance of Operation Theatres and Intensive Care Units of a Newly Established Tertiary Care Teaching Hospital in the Ethnic Belt of Lower Assam

ABSTRACT Background: Hospital-associated infections (HAIs) present a major challenge for newly established healthcare institutions. Environmental reservoirs in high-risk areas such as operation theatres (OTs) and intensive care units (ICUs-NICU, PICU) are significant sources of exogenous infection. Objectives: To estimate the microbiological load and profile of air and surfaces in the OTs and ICU of a newly established tertiary care teaching hospital in Lower Assam. Materials and Methods: This prospective surveillance study was conducted over 12 months (January 2025 to December 2025). Surface samples were collected with sterile cotton swabs from nine predetermined sites (floor, wall, operating table, overhead light, anaesthesia workstation, suction machine, AC vent, baby radiant warmer and instrument trolley). Airborne bacterial load was determined by the settle plate method and expressed in CFU/m³ using Omeliansky’s formula. Isolates were identified by morphological and biochemical characteristics. Results: Of 108 surface swabs, 88 (81.5%) showed no growth and 20 (18.5%) were culture positive; positivity did not differ significantly across sites (p = 0.93). Gram-positive organisms predominated (85.2% of isolates), chiefly Bacillus species, coagulase-negative staphylococci (CoNS) and Micrococcus, followed by Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa. Baseline air counts in the OTs were within the permissible limit of 180 CFU/m³, whereas the ICU (185 CFU/m³) exceeded it; after corrective ventilation and filter maintenance the ICU count fell to 55 CFU/m³ (a 70.3% reduction). Conclusion: Routine microbiological monitoring, strict adherence to cleaning protocols and continued surveillance are essential to maintain a low bioburden and to prevent institutional outbreaks in newly established healthcare settings. Keywords: Microbiological surveillance; operation theatre; intensive care unit; settle plate method; Omeliansky’s formula; hospital-associated infection; Assam