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SURVIVAL AND ATTACHMENT OF SALMONELLA ENTERICA ON ALMOND, HAZELNUT, AND BLACK PEPPER
Title
SURVIVAL AND ATTACHMENT OF SALMONELLA ENTERICA ON ALMOND, HAZELNUT, AND BLACK PEPPER
Creator
Zhai, Yang
Date
2016, 2016-05
Description
S. Enteritidis (SE) and S. Typhimurium (ST) are the two most common Salmonella enterica serovars that cause foodborne illnesses in U.S....
Show moreS. Enteritidis (SE) and S. Typhimurium (ST) are the two most common Salmonella enterica serovars that cause foodborne illnesses in U.S. Outbreaks of these serovars have been attributed to low moisture foods such as nuts and spices. However, little is known about the mechanisms of attachment on low moisture food surfaces. This study evaluated the associations between attachment and survival of Salmonella enterica serovars, storage temperatures, and surface characteristics of selected food samples. In the study, S. Enteritidis PT4 and S. Typhimurium LT2 were inoculated onto the surfaces of black peppercorns, almonds and hazelnuts at ~108 CFU/g. After 2 h air-drying, samples were stored at 4 and 25°C with 58 ± 2% relative humidity for up to 14 d. At specific time points, the food sample were washed two times in 1 × Phosphate Buffered Saline (PBS) to remove attached bacterial cells. The bacterial suspensions were serially diluted and plated on Brain Heart Infusion (BHI) and Xylose Lysine Deoxycholate (XLD) agar plates for enumeration. Significant differences (P<0.05) were found in the survival and attachment of SE and ST under all the conditions. ST can survive and attach better than SE at both 4 and 25°C. The decline rates on almonds, hazelnuts, and black peppercorns at 25°C were 0.348 ± 0.017, 0.273 ± 0.015, and 0.196 ± 0.017 log CFU/g per day for SE and 0.077 ± 0.008, 0.157 ± 0.008, and 0.048 ± 0.005 log CFU/g per day for ST, respectively. The attachment rates on almonds, hazelnuts and black peppercorns at 25°C were 18.71 ± 14.38, 1.56 ± 1.50, and 4.68 ± 0.76% for SE and 38.46 ± 11.32, 18.45 ± 7.73, and 56.30 ± 14.72% for ST, respectively. In addition, low temperature (i.e. 4°C) may contribute more to the survival of Salmonella than ambient temperature (i.e. 25°C). Certain surface characteristics (roughness & hydrophobicity) of hazelnut may probably result in weaker attachment of both Salmonella serovars. The results can be used to better understand the physiology of Salmonella enterica on low moisture foods and aid in developing effective control measures to reduce pathogen contamination.
M.S. in Food Safety and Technology, May 2016
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Measuring Maternal-Fetal Attachment: Model Fit and Measurement Invariance of a New Assessment Tool
Title
Measuring Maternal-Fetal Attachment: Model Fit and Measurement Invariance of a New Assessment Tool
Creator
Hedrick, Laura
Date
2019
Description
The importance of studying Maternal-Fetal Attachment (MFA) as part of the system of maternal-child perinatal functioning is well established...
Show moreThe importance of studying Maternal-Fetal Attachment (MFA) as part of the system of maternal-child perinatal functioning is well established in the literature, as MFA relates to health-related and psychosocial variables both during pregnancy and after the infant is born (e.g., positive health behaviors in pregnancy; levels of maternal stress, anxiety, and depressive symptoms; positive parenting behaviors after the child is born; and secure infant attachment at age one year). Despite the apparent value of studying MFA, there is no acceptable measurement tool for the construct. Existing assessment tools often do not meet minimum psychometric standards, may not be practical for broad research application, and have demonstrated inconsistent results in correlational research. Therefore, a clear need exists for a measurement scale with strong psychometric properties that is based on empirically supported development strategies. The present line of research sought to fill this need. The process of developing a new measurement tool began in a previous study, Hedrick (2015), which used Exploratory Factor Analyses to identify options for a potential measurement scale from subsets of a large pool of items intended to measure MFA. In Hedrick (2015), three options were identified as acceptable, then compared based on ranges of communalities, percentage of variance explained, internal consistency, and performance on two measures of concurrent and discriminant validity. However, these assessments failed to differentiate a single option as most preferable. Therefore, the first aim of present study was to complete the task of differentiating among the working measures to choose a measurement scale. Confirmatory Factor Analysis (CFA) was used to attempt to determine which working measure from the EFA study had the factor structure that fit best in a second sample of participants. The CFA process was not able to differentiate a superior working measure from the options. Therefore, the most theoretically sound of the three was chosen to use as a measurement tool, with some small adjustments made based on the CFA results. To continue to establish the validity of the new questionnaire measure, the second aim of the study was to assess its measurement invariance among different administration methods and populations. The measurement tool was found to be non-invariant in both areas. Specifically, the results of the measurement invariance analyses indicated that the measure should be administered on paper rather than online, would be best applied in research in African American/Black populations than in research with other racial/ethnic groups, and should not be used to compare MFA scores among racial/ethnic groups. Measurement invariance analyses also revealed that the scale was non-invariant at the metric level regarding parity groups. The implications of these findings for further research is discussed.
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