Effect of Rapid Product Desiccation or Hydration on Thermal Resistance of Salmonella enterica Serovar Enteritidis PT 30 in Wheat Flour

Salmonella is able to survive in low-moisture environments and is known to be more heat resistant as product water activity (aw) decreases. However, it is unknown how rapidly the resistance changes if product aw is altered rapidly, as can occur in certain processes. Therefore, the objective was to determine the effect of rapid product desiccation or hydration on Salmonella thermal resistance. Two dynamic moisture treatments were compared with two static moisture treatments to determine the effect of time-at-moisture on the thermal resistance of Salmonella enterica serovar Enteritidis phage type 30 (PT 30) in wheat flour. After inoculation, two static moisture groups were equilibrated to 0.3 and 0.6 aw over 4 to 7 days, and two dynamic moisture groups then were rapidly (<4 min) desiccated from 0.6 to 0.3 aw or hydrated from 0.3 to 0.6 aw. Samples then were subjected to isothermal (80°C) heat treatments, and Salmonella thermal resistance was compared via decimal reduction times (i.e., D80°C-values). The D80°C-value in flour that was rapidly desiccated from 0.6 to 0.3 aw was statistically equivalent (P > 0.05) to the D80°C-value in flour previously equilibrated to 0.3 aw, but both were greater (P < 0.05) than the D80°C-value in flour previously equilibrated to 0.6 aw. Similarly, the D80°C-value in flour rapidly hydrated from 0.3 to 0.6 aw was statistically equivalent (P > 0.05) to the D80°C-value in flour previously equilibrated to 0.6 aw, and both were less than the D80°C-value in flour previously equilibrated to 0.3 aw. Therefore, Salmonella in the rapidly desiccated flour (0.3 aw) was as thermally resistant as that which previously had been equilibrated to 0.3 aw, and Salmonella in the rapidly hydrated flour (0.6 aw) responded similarly to that in the flour previously equilibrated to 0.6 aw. These results suggest that the response period to new aw is negligible, which is critically important in applying thermal resistance data or parameters to industrial pasteurization validations.

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Characterization of SEN3800-associated virulence of Salmonella enterica serovar Enteritidis phage type 8

Annals of Microbiology ◽

10.1007/s13213-014-0898-8 ◽

2014 ◽

Vol 65 (2) ◽

pp. 631-637

Author(s):

Daniel C. Shippy ◽

Nicholas M. Eakley ◽

Dareen M. Mikheil ◽

Anna De La Cotera ◽

Amin A. Fadl

Keyword(s):

Salmonella Enterica ◽

Phage Type ◽

Salmonella Enterica Serovar Enteritidis

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Growth of Salmonella Enteritidis Phage Type 30 in Almond Hull and Shell Slurries and Survival in Drying Almond Hulls

Journal of Food Protection ◽

10.4315/0362-028x-69.4.712 ◽

2006 ◽

Vol 69 (4) ◽

pp. 712-718 ◽

Cited By ~ 51

Author(s):

AARON R. UESUGI ◽

LINDA J. HARRIS

Keyword(s):

Incubation Time ◽

Rapid Growth ◽

Salmonella Enterica ◽

Salmonella Enteritidis ◽

Phage Type ◽

Weather Conditions ◽

Water Sources ◽

Salmonella Enterica Serovar Enteritidis ◽

Outbreak Strain ◽

High Concentrations

Traceback investigation of a 2000 to 2001 outbreak of salmonellosis associated with consumption of raw almonds led to isolation of the outbreak strain Salmonella enterica serovar Enteritidis phage type (PT) 30 on three geographically linked almond farms. Interviews with these growers revealed that significant rain fell during the 2000 harvest when many almonds were drying on the ground. The objectives of this study were to document weather conditions during the 2000 harvest, determine the potential for growth of Salmonella Enteritidis PT 30 in hull or shell slurries, and evaluate survival of Salmonella Enteritidis PT 30 on wet almond hulls during drying. Dry almond hulls and in-shell kernels wetted for 24 h increased in weight by 250 to 300% and 100%, respectively. Both hull and shell slurries supported rapid growth of Salmonella Enteritidis PT 30 at 24°C; slurries containing hulls also supported growth at 15°C. Maximum Salmonella Enteritidis PT 30 concentrations of 6.2 and 7.8 log CFU/ml were observed at 15 and 24°C, respectively. Salmonella Enteritidis PT 30 grown in wet hulls that were incubated at 24°C survived drying at either 15 or 37°C. Reductions of 1 to 3 log CFU/g of dry hull were observed during drying; reductions generally declined as incubation time increased from 2 to 7 days. Evaluation of shipping records revealed that approximately 60% of outbreak-associated almonds had not been exposed to rain, eliminating this factor as the sole cause of the outbreak. However, the data provide evidence that wet almonds may be a greater risk for high concentrations of Salmonella, and specific guidelines should be established for harvesting and processing almonds that have been exposed to rain or other water sources.

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Correlation of conversion of Salmonella enterica serovar enteritidis phage type 1, 4, or 6 to phage type 7 with loss of lipopolysaccharide.

Journal of Clinical Microbiology ◽

10.1128/jcm.35.1.330-333.1997 ◽

1997 ◽

Vol 35 (1) ◽

pp. 330-333 ◽

Cited By ~ 17

Author(s):

D L Baggesen ◽

H C Wegener ◽

M Madsen

Keyword(s):

Salmonella Enterica ◽

Phage Type ◽

Salmonella Enterica Serovar Enteritidis

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A severe gastroenteritis outbreak of Salmonella enterica serovar Enteritidis PT8, with PFGE profile XbaI.0024 and MLVA profile 2-9-7-3-2 following a christening reception, Greece, 2016

Epidemiology and Infection ◽

10.1017/s0950268817002667 ◽

2017 ◽

Vol 146 (1) ◽

pp. 28-36 ◽

Cited By ~ 1

Author(s):

G. MANDILARA ◽

C. M. VASSALOS ◽

A. CHRISOSTOMOU ◽

K. KARADIMAS ◽

E. MATHIOUDAKI ◽

...

Keyword(s):

Salmonella Enterica ◽

Virulent Strain ◽

Phage Type ◽

Variable Number Tandem Repeat ◽

Admission Rate ◽

Variable Number ◽

Molecular Techniques ◽

Contributing Factors ◽

Salmonella Enterica Serovar Enteritidis ◽

Hospital Admission Rate

SUMMARYIn June 2016, a Salmonella enterica serovar Enteritidis outbreak (n = 56) occurred after a christening reception in Central Greece, mainly affecting previously healthy adults; one related death caused media attention. Patients suffered from profuse diarrhoea, fever and frequent vomiting episodes requiring prolonged hospitalisation and sick leave from work, with a 54% hospital admission rate. The majority of cases experienced serious illness within <12 h of attending the party. We investigated the outbreak to identify the source(s) of infection and contributing factors to the disease severity. From the retrospective cohort study, the cheesy penne pasta was the most likely vehicle of infection (relative risk 7·8; 95% confidence interval 3·6–16·8), explaining 79% of the cases. S. enterica ser. Enteritidis isolates were typed as phage-type PT8, pulsed-field gel electrophoresis type XbaI.0024, multiple locus variable-number tandem repeat analysis-type 2-9-7-3-2. The strain did not share the single-nucleotide polymorphism address of the concurrent European S. enterica ser. Enteritidis PT8 outbreak clusters. Following five consecutive years with no documented S. enterica ser. Enteritidis outbreaks in Greece, this outbreak, likely associated with a virulent strain, prompted actions towards the enhancement of the national Salmonella molecular surveillance and control programmes including the intensification of training of food handlers for preventing similar outbreaks in the future. Advanced molecular techniques were useful in distinguishing unrelated outbreak strains.

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Increased Water Activity Reduces the Thermal Resistance of Salmonella enterica in Peanut Butter

Applied and Environmental Microbiology ◽

10.1128/aem.01028-13 ◽

2013 ◽

Vol 79 (15) ◽

pp. 4763-4767 ◽

Cited By ~ 33

Author(s):

Yingshu He ◽

Ye Li ◽

Joelle K. Salazar ◽

Jingyun Yang ◽

Mary Lou Tortorello ◽

...

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Thermal Resistance ◽

Water Activity ◽

Salmonella Enterica ◽

Morphological Changes ◽

Peanut Butter ◽

Content Type ◽

The Difference ◽

Scanning Electron

ABSTRACTIncreased water activity in peanut butter significantly (P< 0.05) reduced the heat resistance of desiccation-stressedSalmonella entericaserotypes treated at 90°C. The difference in thermal resistance was less notable when strains were treated at 126°C. Using scanning electron microscopy, we observed minor morphological changes ofS. entericacells resulting from desiccation and rehydration processes in peanut oil.

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Survival, Elongation, and Elevated Tolerance of Salmonella enterica Serovar Enteritidis at Reduced Water Activity

Journal of Food Protection ◽

10.4315/0362-028x-69.11.2681 ◽

2006 ◽

Vol 69 (11) ◽

pp. 2681-2686 ◽

Cited By ~ 39

Author(s):

JASPER KIEBOOM ◽

HARSHI D. KUSUMANINGRUM ◽

MARCEL H. TEMPELAARS ◽

WILMA C. HAZELEGER ◽

TJAKKO ABEE ◽

...

Keyword(s):

Water Activity ◽

Salmonella Enterica ◽

Morphological Changes ◽

Physiological Activity ◽

Membrane Integrity ◽

Salmonella Enterica Serovar Enteritidis ◽

Normal Morphology ◽

Processing Plants ◽

Reduced Water ◽

Number Of Cells

Growing microorganisms on dry surfaces, which results in exposure to low water activity (aw), may change their normal morphology and physiological activity. In this study, the morphological changes and cell viability of Salmonella enterica serovar Enteritidis challenged to low aw were analyzed. The results indicated that exposure to reduced aw induced filamentation of the cells. The amount of filamentous cells at aw 0.94 was up to 90% of the total number of cells. Surviving filamentous cells maintained their membrane integrity after exposure to low aw for 21 days. Furthermore, cells prechallenged to low aw, obtained with an ionic humectant, demonstrated higher resistance to sodium hypochlorite than control cells. These resistant cells are able to survive disinfection more efficiently and can therefore cause contamination of foods coming in contact with surfaces. This points to the need for increased attention to cleaning of surfaces in household environments and disinfection procedures in processing plants.

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Effects of Inoculation Procedures on Variability and Repeatability of Salmonella Thermal Resistance in Wheat Flour

Journal of Food Protection ◽

10.4315/0362-028x.jfp-16-057 ◽

2016 ◽

Vol 79 (11) ◽

pp. 1833-1839 ◽

Cited By ~ 31

Author(s):

IAN M. HILDEBRANDT ◽

BRADLEY P. MARKS ◽

ELLIOT T. RYSER ◽

ROSSANA VILLA-ROJAS ◽

JUMING TANG ◽

...

Keyword(s):

Thermal Resistance ◽

Water Activity ◽

Wheat Flour ◽

Thermal Inactivation ◽

Culture Method ◽

Isothermal Treatment ◽

Inactivation Kinetics ◽

Inoculation Methods ◽

Low Moisture Foods ◽

D Values

ABSTRACT Limited prior research has shown that inoculation methods affect thermal resistance of Salmonella in low-moisture foods; however, these effects and their repeatability have not been systematically quantified. Consequently, method variability across studies limits utility of individual data sets and cross-study comparisons. Therefore, the objective was to evaluate the effects of inoculation methodologies on stability and thermal resistance of Salmonella in a low-moisture food (wheat flour), and the repeatability of those results, based on data generated by two independent laboratories. The experimental design consisted of a cross-laboratory comparison, both conducting isothermal Salmonella inactivation studies in wheat flour (~0.45 water activity, 80°C), utilizing five different inoculation methods: (i) broth-based liquid inoculum, (ii) lawn-based liquid inoculum, (iii) lawn-based pelletized inoculum, (iv) direct harvest of lawn culture with wheat flour, and (v) fomite transfer of a lawn culture. Inoculated wheat flour was equilibrated ~5 days to ~0.45 water activity and then was subjected to isothermal treatment (80°C) in aluminum test cells. Results indicated that inoculation method impacted repeatability, population stability, and inactivation kinetics (α = 0.05), regardless of laboratory. Salmonella inoculated with the broth-based liquid inoculum method and the fomite transfer of a lawn culture method exhibited instability during equilibration. Lawn-based cultures resulted in stable populations prior to thermal treatment; however, the method using direct harvest of lawn culture with wheat flour yielded different D-values across the laboratories (α = 0.05), which was attributed to larger potential impact of operator variability. The lawn-based liquid inoculum and the lawn-based pelletized inoculum methods yielded stable inoculation levels and repeatable D-values (~250 and ~285 s, respectively). Also, inoculation level (3 to 8 log CFU/g) did not affect D-values (using the lawn-based liquid inoculum method). Overall, the results demonstrate that inoculation methods significantly affect Salmonella population kinetics and subsequent interpretation of thermal inactivation data for low-moisture foods.

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Water activity change at elevated temperatures and thermal resistance of Salmonella in all purpose wheat flour and peanut butter

Food Research International ◽

10.1016/j.foodres.2016.01.008 ◽

2016 ◽

Vol 81 ◽

pp. 163-170 ◽

Cited By ~ 48

Author(s):

Roopesh M. Syamaladevi ◽

Ravi Kiran Tadapaneni ◽

Jie Xu ◽

Rossana Villa-Rojas ◽

Juming Tang ◽

...

Keyword(s):

Thermal Resistance ◽

Water Activity ◽

Wheat Flour ◽

Elevated Temperatures ◽

Peanut Butter ◽

Activity Change

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Differences in Gene Content between Salmonella enterica Serovar Enteritidis Isolates and Comparison to Closely Related Serovars Gallinarum and Dublin

Journal of Bacteriology ◽

10.1128/jb.187.18.6545-6555.2005 ◽

2005 ◽

Vol 187 (18) ◽

pp. 6545-6555 ◽

Cited By ~ 81

Author(s):

S. Porwollik ◽

C. A. Santiviago ◽

P. Cheng ◽

L. Florea ◽

M. McClelland

Keyword(s):

Salmonella Enterica ◽

Domestic Fowl ◽

Phage Type ◽

Gene Content ◽

Comparative Genomic ◽

Old Field ◽

Salmonella Enterica Serovar Enteritidis ◽

Cross Hybridization ◽

Reference Collection ◽

Almost All

ABSTRACT Salmonella enterica serovar Enteritidis is often transmitted into the human food supply through eggs of hens that appear healthy. This pathogen became far more prevalent in poultry following eradication of the fowl pathogen S. enterica serovar Gallinarum in the mid-20th century. To investigate whether changes in serovar Enteritidis gene content contributed to this increased prevalence, and to evaluate genetic heterogeneity within the serovar, comparative genomic hybridization was performed on eight 60-year-old and nineteen 10- to 20-year-old serovar Enteritidis strains from various hosts, using a Salmonella-specific microarray. Overall, almost all the serovar Enteritidis genomes were very similar to each other. Excluding two rare strains classified as serovar Enteritidis in the Salmonella reference collection B, only eleven regions of the serovar Enteritidis phage type 4 (PT4) chromosome (sequenced at the Sanger Center) were absent or divergent in any of the other serovar Enteritidis strains tested. The more recent isolates did not have consistent differences from 60-year-old field isolates, suggesting that no large genomic additions on a whole-gene scale were needed for serovar Enteritidis to become more prevalent in domestic fowl. Cross-hybridization of phage genes on the array with related genes in the examined genomes grouped the serovar Enteritidis isolates into two major lineages. Microarray comparisons of the sequenced serovar Enteritidis PT4 to isolates of the closely related serovars Dublin and Gallinarum (biovars Gallinarum and Pullorum) revealed several genomic areas that distinguished them from serovar Enteritidis and from each other. These differences in gene content could be useful in DNA-based typing and in understanding the different phenotypes of these related serovars.

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