Microbiological profile of oxygen humidifiers at a tertiary care centre in the Himalayas: An exploratory study

Background: Reusable humidifiers are often colonised by microbes, the aerosols generated from which are hypothesised to transmit respiratory infections-jeopardising patient safety. Materials and Methods: In this time-bound cross-sectional study, 10 ml of water was collected in sterile containers from humidifiers installed in selected wards/critical care units/intensive care units and from the source used to refill these humidifiers. These samples were subjected to KOH and gram staining followed by inoculation on blood, MacConkey and Sabouraud dextrose agar and brain heart infusion broth in the aerobic environment at 37°C. Observations were recorded as per standard guidelines and compared against blood and respiratory cultures of patients. Results: Despite an average of 8.23 days of exposure to oxygen humidified by contaminated water, n = 28 (of n = 39) blood samples reported no growth (NG) and n = 12 reported nonpathogenic organisms (NPO). Among n = 18 available respiratory samples, n = 1 reported Escherichia coli, which was not cultured from the same humidifier indicative of some other source. n = 1 reported NG, n = 6 reported NPO and n = 10 reported normal throat flora. No fungal elements were reported from any humidifier, source, or patient samples. The source-humidifier pathogen pair did not match for any humidifier. Conclusions: Sterile patient cultures, despite prolonged exposure to oxygen humidified with contaminated water, indicate that humidifier contaminants did not infect patients. The disparity between the source or patient cultures and humidifier contaminants may be attributed to compromised universal precautions due to the exhaustion of health-care professionals during COVID-19. Furthermore, the type of water used to refill (Distilled/RO/Tap water) had no effect on the microbial contamination of humidifiers.