Microwave disinfection: assessing the risks of irrigation bottle and fluid contamination

It was previously shown that 50% of irrigation bottles and 40% of irrigation fluids had evidence of bacterial contamination despite cleaning with hot water and soap. Although a novel method of microwave disinfection has recently been proposed to minimize contamination risk, this has not been studied in a real life setting. This study investigates the effectiveness of microwave disinfection for reducing both nasal irrigation bottle and irrigation fluid contamination risk after endoscopic sinus surgery (ESS).

Twenty consecutive patients underwent ESS for chronic rhinosinusitis. Patients were given NeilMed Sinus Rinse bottles (NeilMed Pharmaceuticals, Inc., Santa Rosa CA) to use twice daily, with microwave cleaning instructions preoperatively. Bottles were collected and cultured 1 week postoperatively. Sterile saline (5 mL) was mixed into the irrigation bottle and cultured separately. An additional 10 patients were recruited whereby the bottle was cultured at collection and immediately after microwave disinfection was performed in the clinic.

For the first cohort of the study, 40% of the bottles and 20% of the irrigation samples had positive cultures 1 week postoperatively. Common bacteria included Acinetobacter, coagulase-negative Staphylococcus, and Gram-negative bacilli. For the second cohort of patients, 20% of the irrigation bottles had positive cultures. However, after supervised microwave disinfection, there was a 0% contamination rate.

Despite detailed instructions on microwave disinfection, positive bacterial cultures may still occur after ESS. This risk, however, appears to be significantly reduced when bottles are microwaved under supervision. These findings suggest either a reduced patient compliance to cleaning or a time-dependent recontamination risk after disinfection.