Forensic Analysis of Polymeric Carpet Fibers Using Direct Analysis in Real Time Coupled to an AccuTOF™ Mass Spectrometer

Polymeric fibers are encountered in numerous forensic circumstances. This study focused on polymeric carpet fibers most encountered at a crime scene, which are nylons, polyesters and olefins. Analysis of the multiple polymer types was done using Direct Analysis in Real Time (DART™) coupled to an Accurate time-of-flight (AccuTOF™) mass spectrometer (MS). A DART gas temperature of 275 °C was determined as optimal. Twelve olefin, polyester, and nylon polymer standards were used for parameter optimization for the carpet fiber analysis. A successful identification and differentiation of all twelve polymer standards was completed using the DART-AccuTOF™. Thirty-two carpet samples of both known and unknown fiber composition were collected and subsequently analyzed. All samples with known fiber compositions were correctly identified by class. All of the remaining carpet samples with no known composition information were correctly identified by confirmation using Fourier-transform infrared spectroscopy (FTIR). The method was also capable of identifying sub-classes of nylon carpet fibers. The results exhibit the capability of DART-AccuTOF™ being applied as an addition to the sequence of tests conducted to analyze carpet fibers in a forensic laboratory.

Recovery Optimization and Survival of the Human Norovirus Surrogates Feline Calicivirus and Murine Norovirus on Carpet

ABSTRACT Carpets have been implicated in prolonged and reoccurring outbreaks of human noroviruses (HuNoV), the leading cause of acute gastroenteritis worldwide. Viral recovery from environmental surfaces, such as carpet, remains undeveloped. Our aim was to determine survival of HuNoV surrogates on an understudied environmental surface, carpet. First, we measured the zeta potential and absorption capacity of wool and nylon carpet fibers, we then developed a minispin column elution (MSC) method, and lastly we characterized the survival of HuNoV surrogates, feline calicivirus (FCV) and murine norovirus (MNV), over 60 days under 30 and 70% relative humidity (RH) on two types of carpet and one glass surface. Carpet surface charge was negative between relevant pH values (i.e., pH 7 to 9). In addition, wool could absorb approximately two times more liquid than nylon. The percent recovery efficiency obtained by the MSC method ranged from 4.34 to 20.89% and from 30.71 to 54.14% for FCV and MNV on carpet fibers, respectively, after desiccation. Overall, elution buffer type did not significantly affect recovery. Infectious FCV or MNV survived between <1 and 15 or between 3 and 15 days, respectively. However, MNV survived longer under some conditions and at significantly (P < 0.05) higher titers compared to FCV. Albeit, surrogates followed similar survival trends, i.e., both survived longest on wool then nylon and glass, while 30% RH provided a more hospitable environment compared to 70% RH. Reverse transcription-quantitative PCR signals for both surrogates were detectable for the entire study, but FCV genomic copies experienced significantly higher reductions (<3.80 log10 copies) on all surfaces compared to MNV (<1.10 log10 copies). IMPORTANCE Human noroviruses (HuNoV) are the leading cause of acute gastroenteritis worldwide. Classical symptoms of illness include vomiting and diarrhea which could lead to severe dehydration and death. HuNoV are transmitted by the fecal-oral or vomitus-oral route via person-to-person contact, food, water, and/or environmental surfaces. Published laboratory-controlled studies have documented the environmental stability of HuNoV on hard surfaces, but there is limited laboratory-based evidence available about survival on soft surfaces, e.g., carpet and upholstered furniture. Several epidemiological reports have suggested soft surfaces may be HuNoV fomites illustrating the importance of conducting a survival study. The three objectives of our research were to demonstrate techniques to characterize soft surfaces, develop a viral elution method for carpet, and characterize the survival of HuNoV surrogates on carpet. These results can be used to improve microbial risk assessments, the development of much-needed soft surface disinfectant, and standardizing protocols for future soft surface studies.