Remote monitoring and rapid detection of aspergillus fumigatus using a self-contained and sterile cartridge loading system

Microbial contamination can result in serious disease outbreaks in healthcare environments and in mass food spoilage in the food & beverage and agricultural industries. This contamination can ultimately lead to increased mortality, illnesses, costs and reputational damage. Currently available bio-contamination detection systems are based primarily around selective placement of growth media plates in areas under investigation. These platforms must then be removed and transported to a laboratory, where they are typically incubated and studied to assess the growth of microbes. This process can take upwards of 42 hours, depending on the availability of an adequately equipped onsite laboratory. Impaction devices have been introduced to help test larger volumes of air in small areas; however, the incubation and visual examination of platforms still present a significant hindrance to rapid detection of contamination outbreaks. Furthermore, such investigations require dedicated trained personnel. A technological overview and validation experimentation is presented herein, focussing on the rapid, automated detection of airborne Aspergillus Fumigatus spores present in the environment using the RAPID READER optical based sensor. A. fumigatus is a fungus shown to cause disease in immunecompromised individuals. A. fumigatus is a saprotroph (mycelium based growth) which has been found to be widespread in nature [1]. This study shows the ability of the RAPID READER system to detect, within a short timescale, the presence of A. fumigatus using the patented technology. Technology Microbial contaminants may be spread by various means e.g. direct transmission from contaminated surfaces or individuals by touch or through contaminated water supplies. However, in the aforementioned industries even with strict decontamination methods for surfaces, individuals and water supplies in place, microbial contamination still remains commonplace. An aspect of microbial contamination which is far more difficult to control is that of airborne contamination. Microbes may persist on hard to reach surfaces for up to several months or more. When disturbed, these microbes become airborne, enabling transmission to other areas of the particular facility in question. Furthermore, poor compliance with cleaning procedures and high footfall in other areas of a facility may result in regions of high levels of contamination. Again as this area is disturbed by the movement of individuals or machinery, microbial contamination from a ‘low risk’ (e.g. warehouse) to a ‘high risk’ (e.g. food production line) area, through airborne contaminants, is likely. White Paper NW_15 Current methods for assessing the levels of microbial contamination involve the use of (a) sampling and plating, (b) biochemical laboratory analysis and (c) optical methods. Assessments using methods (a) and (b) usually involve relatively long timescales (~ several days), highly trained staff and/or investment in costly chemicals and instrumentation. For example, samples must be prepared by an individual skilled in the field of microbiology before growing on nutrient media and enumeration or, in the case of polymerase chain reaction (PCR), samples must be isolated and one or a series of chemical preparations performed before the microbes are identified. Therefore, such methods are usually invoked in very specific laboratory analyses. Optical methods are most suited to remote monitoring of airborne microbial activity as technologies can be devised which may be deployed in the field and require minimal end user interaction. The RAPID READER system operation is based on biophysical elastic light scattering induced by microbial colonies and the morphological changes they can induce on the surface on which they grow. It is known in the scientific literature that individual bacterial colonies act as biological spatial light modulators which produce unique scatter patterns. The RAPID READER system is based around the optical monitoring of laser light passing through a polymer and agar based sensor. Environmental air is impacted upon the sensor in short evenly spaced bursts, during which time airborne contaminants take hold and begin to grow. By selecting highly specific growth media with the appropriate optical characteristics, contaminants that require monitoring may be individually targeted. As the contaminant grows, the laser light passing through the medium begins to be affected. Scattering of the light occurs, accompanied by a change in the direct transmission intensity through the agar sample. Originally A. fumigatus was thought to only reproduce asexually, however it was later discovered to also have a fully functioning sexual reproductive cycle [2]. This cycle is shown in Fig 1. During each cycle spores (ascospores and conidiospores depending on reproductive track) are created which may then become airborne and spread the mould beyond its immediate area. A. fumigatus causes roughly 90% of all invasive aspergillus infections in people, and has a high (50-95%) mortality rate [3]. The main route of infection is inhalation, and to a lesser extent open wounds, and infection is especially dangerous to immunocompromised patients. Due to the nature of the A. fumigatus growth, which generates a web-like mesh called a mycelium (shown in Fig 2), the scattering of light is enhanced through diffraction as the colonies thicken. Moreover, changes caused on the surface by the growths (chemical and topographical), exacerbate the scatter effect. Colonies can form from as little as a single airborne spore. Given that the transmitted and scattered light paths are modified by the growth of microbes on the agar, both the transmission and scatter intensities are constantly monitored for changes during operation, in order to evaluate the presence and growth of A. Fumigatus on the sample.