The Characterization of Methylene Blue in detecting bacterial contamination with the updated design of the Rapid Culture Nanowell Device

Abstract

With approximately 24,500 preterm children born annually in Canada and an estimated shortage of 6 million ounces of breast milk, the distribution of donor milk must be time-sensitive yet safe to efficiently meet this demand. Donor human milk banks take the greatest precautions to protect their users, but some of these microorganisms manage to circumvent the employed methods. The consumption of contaminated donor milk has the potential to be fatal particularly to the vulnerable, immunocompromised premature infants. The tools used by milk banks to ensure safe distribution rely heavily on the culture plate. It has been the gold standard in screening for microbiological specimens due to its wide availability, low cost, and simplicity. However, the procedural times for bacterial culture plates are tedious and long, lasting a minimum of 48 hours. Advances in microfluidics, particularly in combination with the concept of monitoring metabolites to indicate bacterial viability, hold much promise to significantly reducing the long processing times of culture plates. Combining the concept of compartmentalized culture and a chromogenic optical dye for the detection of metabolic changes as a diagnostic sensor would simplify the identification and quantification of microbial presence. The updated Rapid Culture Detection system is a nanowell device fabricated using polydimethylsiloxane (PDMS) that uses the oxygen-sensitive redox indicator Methylene Blue to determine the presence of bacteria. Preliminary studies have shown to detect bacteria in as little as 3.33 hours using these nanowells compared to the 24 hours required for microwell liquid culture (620%). Initial studies have also been conducted with human milk, indicating a slower detection than in LB media. The novel easy-to-use and low-cost Rapid Culture Detection system is a promising alternative detection tool for protecting infants from pathogenic illnesses caused by contaminated human milk and shortening the time required to access lifesaving nutrition.