The ability to generate deoxyribonucleic acid (DNA) profiles from genetic material is a powerful tool commonly used by forensic scientists. The first major step of this process is the collection of DNA from a crime scene. DNA may be deposited in many ways, including in biological fluids and by touch DNA deposition. Techniques such as swabbing are commonly used, but often pose problems when used on rough, porous surfaces. The M-Vac® is a wet-vacuum designed to spray and recollect a buffer solution from a surface to allow for the collection of DNA from these porous objects. Dilute saliva samples and touch DNA via handling were deposited on assorted items and collected using both traditional swabbing and wet vacuum methods. Further, M-Vac® filters containing collected material were extracted using the EZ1 Biorobot either in a single tube or divided into approximately quarters and extracted in four separate tubes to assess DNA yields from both methods. The M-Vac® was shown to collect equal or greater amounts of DNA compared to swabbing from various porous surfaces, and the samples collected with the M-Vac® were shown to produce more complete DNA profiles. Use of the M-Vac® on surfaces following swab collection resulted in the recovery of additional DNA, often exceeding the amount initially recovered from the swab. It was also observed that in nearly all profiles generated from touch DNA sources, alleles were detected that originated from a non-donor source. In some cases, extraction from filters in quarters resulted in a higher total amount of DNA than whole filters when all four quarters were added together. However, quarters from a single filter had a high amount of variation in the level of DNA, indicating that the DNA may not be distributed evenly on the filter.

Master of Science / Food Science Institute / Daniel Y.C. Fung / There are many different environmental sampling methods that are currently used in the industry. They include swab, sponge, flocked swab, direct agar contact, and M-Vac. Several studies have been conducted to determine the benefits and drawbacks of each method. Sampling methods utilized in this study were the swab, flocked swab, and M-Vac. Three surfaces were utilized in this study: ultra high density polypropylene, 304 stainless steel with a 2B finish, and 304 stainless steel with a 2B finish and a buffed surface. Surfaces sampled were 100 cm2. Prior to inoculation, surfaces were autoclaved for 15 min at 121 °C for sterilization. Surfaces were inoculated by either Listeria monocytogenes or Escherichia coli O157:H7 at a concentration of 9 log10 CFU/ml by painting the inoculum onto the surface with a sterilized paintbrush. Brushes were dipped in inoculum for 2 sec before painting from left to right once and then from up to down once. Brushes were redipped for 2 sec and the painting step was repeated. The same brush was used for all E. coli O157:H7 samples and a different brush was used for all L. monocytogenes samples. Then, the surfaces were allowed to dry for 30 min before sampling took place. Listeria monocytogenes samples were appropriately diluted and plated in duplicate onto Tryptic Soy Agar (TSA) and Modified Oxford Media (MOX). Escherichia coli O157:H7 samples were properly diluted and plated in duplicate onto TSA and MacConkey Sorbital Agar (MSA). After plating, dry surfaces were stained using LIVE/DEAD® BacLight™ Bacterial Viability Kit. The Zeiss LSM 5 Pascal confocal laser scanning electron microscope was used for microscopy images and photographs. Six 1 mm by 1 mm random and representative images were taken of each surface. Viable cell count results show that the sponge sampling method, in general, recovered a higher number of microorganisms. The swab was normally shown to recover the least number of microorganisms. When examining the microscopy images it can be concluded that biofilms are more easily formed with L. monocytogenes than E. coli O157:H7. Imaging also allowed for a visual representation of the remaining organisms that made it appear as if there was actually more bacteria recovery when the M-Vac sampling method was employed than when the sponge method was utilized.