scholarly journals Enumeration and Survival of Salmonella enterica in Live Oyster Shellstock Harvested from Canadian Waters

2019 ◽  
Vol 83 (1) ◽  
pp. 6-12 ◽  
Author(s):  
SANDEEP TAMBER ◽  
ALEX MONTGOMERY ◽  
KATIE ELORANTA ◽  
ENRICO BUENAVENTURA
Keyword(s):  
Salmonella Enterica ◽  
Most Probable Number ◽  
Oyster Tissue ◽  
Probable Number ◽  
Ambient Temperatures ◽  
Fundamental Information ◽  
Data Gaps ◽  
Contamination Event ◽  
Management Approaches ◽  
The Relationship

ABSTRACT Since 2015, 11 recalls of live oyster shellstock have been issued in Canada due to the presence of Salmonella enterica. Six of those recalls took place in 2018. To understand this increase, fundamental information is needed on the relationship between S. enterica and oysters. The aims of this study were to address important data gaps concerning the levels of Salmonella in naturally contaminated oysters and the ability of this pathogen to survive in live oyster shellstock. Enumeration data were evaluated for five oyster and clam samples collected from the east coast of Canada from 2015 to 2018. The reported levels were <0.0015 to 0.064 most probable number per g of oyster tissue. The S. enterica isolates recovered from these animals belonged to serovars Typhimurium, Infantis, Enteritidis, and I 4,5:i:−. Filter feeding by the oysters was exploited to assess the Salmonella accumulation that would occur following a natural contamination event. Detectable levels of the pathogen were observed after 30 min of exposure and began to plateau at 60 min. A survival study in live oyster shellstock indicated that after 4 days of storage at ambient temperatures, the Salmonella level declined slightly from 4.3 to 3.7 log CFU/g. These data indicate that the levels of Salmonella found in naturally contaminated oysters are low and are not expected to increase between the point of harvest and the point of consumption. The changing ecology of shellfish environments requires continued monitoring and testing to safeguard public health. The data presented here will be useful for the evaluation and design of sampling plans and risk management approaches for the control of Salmonella in live oyster shellstock. HIGHLIGHTS

Persistence of Orally Administered Salmonella enterica Serovars Agona and Montevideo in Atlantic Salmon (Salmo salar L.)

2005 ◽  
Vol 68 (7) ◽  
pp. 1336-1339 ◽  
Author(s):  
L. L. NESSE ◽  
T. LØVOLD ◽  
B. BERGSJØ ◽  
K. NORDBY ◽  
C. WALLACE ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Salmonella Enterica ◽  
Most Probable Number ◽  
Fish Feed ◽  
Internal Organs ◽  
Probable Number ◽  
Atlantic Salmon Salmo Salar ◽  
Gastric Intubation

The objective of our experiments was to study the persistence and dissemination of orally administered Salmonella in smoltified Atlantic salmon. In experiment 1, salmon kept at 15°C were fed for 1 week with feed contaminated with 96 most-probable-number units of Salmonella Agona per 100 g of feed and then starved for 2 weeks. Samples were taken from the gastrointestinal tract and examined for Salmonella 1, 2, 8, 9, 15, and 16 days after the feeding ended. In experiment 2, Salmonella Agona and Montevideo were separately mixed with feed and administered by gastric intubation. Each fish received 1.0 × 108, 1.0 × 106, or 1.0 × 104 CFU. The different groups were kept in parallel at 5 and 15°C and observed for 4 weeks. Every week, three fish in each group were sacrificed, and samples were taken from the skin, the pooled internal organs, the muscle, and the gastrointestinal tract and examined for the presence of Salmonella. The results from the two experiments showed that the persistence of Salmonella in the fish was highly dependent on the dose administered. Salmonella was not recovered from any of the fish that were fed for 1 week with the lowest concentration of Salmonella. In the fish given the highest dose of Salmonella, bacteria persisted for at least 4 weeks in the gastrointestinal tract as well as, to some extent, the internal organs. The present study shows that under practical conditions in Norway, the risk of Salmonella in fish feed being passed on to the consumer of the fish is negligible.

Survival of Escherichia coli on Lettuce under Field Conditions Encountered in the Northeastern United States

2017 ◽  
Vol 80 (7) ◽  
pp. 1214-1221 ◽  
Author(s):  
Daniel L. Weller ◽  
Jasna Kovac ◽  
Sherry Roof ◽  
David J. Kent ◽  
Jeffrey I. Tokman ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Microbial Contamination ◽  
Field Conditions ◽  
Risk Assessments ◽  
Most Probable Number ◽  
Northeastern United States ◽  
Probable Number ◽  
E Coli ◽  
The Relationship ◽  
Sample Time

ABSTRACT Although wildlife intrusion and untreated manure have been associated with microbial contamination of produce, relatively few studies have examined the survival of Escherichia coli on produce under field conditions following contamination (e.g., via splash from wildlife feces). This experimental study was performed to estimate the die-off rate of E. coli on preharvest lettuce following contamination with a fecal slurry. During August 2015, field-grown lettuce was inoculated via pipette with a fecal slurry that was spiked with a three-strain cocktail of rifampin-resistant nonpathogenic E. coli. Ten lettuce heads were harvested at each of 13 time points following inoculation (0, 2.5, 5, and 24 h after inoculation and every 24 h thereafter until day 10). The most probable number (MPN) of E. coli on each lettuce head was determined, and die-off rates were estimated. The relationship between sample time and the log MPN of E. coli per head was modeled using a segmented linear model. This model had a breakpoint at 106 h (95% confidence interval = 69, 142 h) after inoculation, with a daily decrease of 0.70 and 0.19 log MPN for 0 to 106 h and 106 to 240 h following inoculation, respectively. These findings are consistent with die-off rates obtained in similar studies that assessed E. coli survival on produce following irrigation. Overall, these findings provide die-off rates for E. coli on lettuce that can be used in future quantitative risk assessments.

scholarly journals Chlorine Dioxide Inactivation ofCryptosporidium parvum Oocysts and Bacterial Spore Indicators

2001 ◽  
Vol 67 (7) ◽  
pp. 2993-3001 ◽  
Author(s):  
Christian P. Chauret ◽  
Chris Z. Radziminski ◽  
Michael Lepuil ◽  
Robin Creason ◽  
Robert C. Andrews
Keyword(s):  
Chlorine Dioxide ◽  
Most Probable Number ◽  
Inactivation Kinetics ◽  
Clostridium Sporogenes ◽  
Probable Number ◽  
Waterborne Pathogen ◽  
Viability Assay ◽  
The Relationship ◽  
Different Sources

ABSTRACT Cryptosporidium parvum, which is resistant to chlorine concentrations typically used in water treatment, is recognized as a significant waterborne pathogen. Recent studies have demonstrated that chlorine dioxide is a more efficient disinfectant than free chlorine against Cryptosporidium oocysts. It is not known, however, if oocysts from different suppliers are equally sensitive to chlorine dioxide. This study used both a most-probable-number–cell culture infectivity assay and in vitro excystation to evaluate chlorine dioxide inactivation kinetics in laboratory water at pH 8 and 21�C. The two viability methods produced significantly different results (P < 0.05). Products of disinfectant concentration and contact time (Ct values) of 1,000 mg � min/liter were needed to inactivate approximately 0.5 log10 and 2.0 log10 units (99% inactivation) of C. parvumas measured by in vitro excystation and cell infectivity, respectively, suggesting that excystation is not an adequate viability assay. Purified oocysts originating from three different suppliers were evaluated and showed marked differences with respect to their resistance to inactivation when using chlorine dioxide.Ct values of 75, 550, and 1,000 mg � min/liter were required to achieve approximately 2.0 log10 units of inactivation with oocysts from different sources. Finally, the study compared the relationship between easily measured indicators, includingBacillus subtilis (aerobic) spores andClostridium sporogenes (anaerobic) spores, and C. parvum oocysts. The bacterial spores were found to be more sensitive to chlorine dioxide than C. parvum oocysts and therefore could not be used as direct indicators of C. parvum inactivation for this disinfectant. In conclusion, it is suggested that future studies address issues such as oocyst purification protocols and the genetic diversity of C. parvum, since these factors might affect oocyst disinfection sensitivity.

scholarly journals Dynamics of Salmonella Shedding and Welfare of Hens in Free-Range Egg Production Systems

2016 ◽  
Vol 83 (5) ◽  
Author(s):  
Vaibhav C. Gole ◽  
Rebecca Woodhouse ◽  
Charles Caraguel ◽  
Talia Moyle ◽  
Jean-Loup Rault ◽  
...  
Keyword(s):  
Production System ◽  
Salmonella Enterica ◽  
Egg Production ◽  
Production Systems ◽  
Most Probable Number ◽  
Probable Number ◽  
Content Type ◽  
Free Range ◽  
Phage Types ◽  
Positive Correlations

ABSTRACT The current study investigated the effect of environmental stressors (i.e., weather changes) on Salmonella shedding in free-range production systems and the correlations with behavioral and physiological measures (i.e., fecal glucocorticoid metabolites). This involved longitudinal and point-in-time surveys of Salmonella shedding and environmental contamination on four commercial free-range layer farms. The shedding of Salmonella was variable across free-range farms and in different seasons. There was no significant effect of season on the Salmonella prevalence during this investigation. In this study, the combined Salmonella most probable number (MPN) counts in environmental (including feces, egg belt, dust, nest box, and ramp) samples were highest in samples collected during the summer season (4th sampling, performed in February). The predominant serovars isolated during this study were Salmonella enterica serovar Mbandaka and Salmonella enterica serovar Typhimurium phage types 135 and 135a. These two phage types were involved in several egg product-related Salmonella outbreaks in humans. Multilocus variable-number tandem-repeat analysis (MLVA) results indicated that MLVA types detected from human food poisoning cases exhibited MLVA patterns similar to the strains isolated during this study. All Salmonella isolates (n = 209) were tested for 15 different genes involved in adhesion, invasion, and survival of Salmonella spp. We also observed variations for sopA, ironA, and misL. There were no positive correlations between fecal corticosterone metabolite (FCM) and Salmonella prevalence and/or shedding in feces. Also, there were no positive correlations between Salmonella prevalence and Salmonella count (log MPN) and any of the other welfare parameters. IMPORTANCE In this study, the welfare of laying hens and Salmonella shedding were compared over a prolonged period of time in field conditions. This study investigated the long-term shedding of Salmonella serovars in a free-range egg production system. Given that there is increasing demand for free-range eggs, it is essential to understand the risks associated with such a production system.

Effects of Tomato Variety, Temperature Differential, and Post–Stem Removal Time on Internalization of Salmonella Enterica Serovar Thompson in Tomatoes†

2012 ◽  
Vol 75 (2) ◽  
pp. 297-303 ◽  
Author(s):  
XIAODONG XIA ◽  
YAGUANG LUO ◽  
YANG YANG ◽  
BRYAN VINYARD ◽  
KEITH SCHNEIDER ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Tomato Fruit ◽  
Most Probable Number ◽  
Bacterial Suspension ◽  
Time Interval ◽  
Temperature Differential ◽  
Probable Number ◽  
Tomato Variety ◽  
Removal Time ◽  
Tomato Pulp

Tomatoes have been implicated in salmonellosis outbreaks due to possible contamination through bacterial internalization during postharvest handling. This study was conducted to determine the effects of tomato variety, temperature differential between tomato pulp and bacterial suspension, and the time delay between stem removal and immersion in bacterial suspension on internalization of Salmonella enterica serovar Thompson in tomato fruit. Mature green tomatoes at 32.2°C were immersed in water containing approximately 106 CFU/ml S. enterica bacteria. Different tomato varieties (Mountain Spring, Applause, and BHN961), temperature differentials (−10, 0, and 10°F, or −5.6, 0, and 5.6°C, respectively), and post–stem removal times (0, 2, and 16 h) were evaluated for their effects on S. enterica internalization. The incidence and density of internalized cells were determined by culture enrichment and most-probable-number methods, respectively. Overall, variety and post–stem removal time by variety interaction significantly affected the incidence of S. enterica internalization (P &lt; 0.0001), while temperature differential had no significant effect (P = 0.36). Mountain Spring tomatoes were less susceptible to S. enterica internalization than were Applause and BHN961. Increasing the time interval between stem removal and immersion greatly reduced pathogen internalization in BHN961 and Applause, while it had no effect in Mountain Spring tomatoes. The variety and interactions between varieties and post–stem removal times (P = 0.0363) and between temperature differentials and post–stem removal times (P = 0.0257) had significant effects on the populations of internalized S. enterica. Furthermore, all internalized S. enterica cells were found within the core tissue segments immediately underneath the stem scars.

scholarly journals Distribution and Characterization of Salmonella enterica Isolates from Irrigation Ponds in the Southeastern United States

2015 ◽  
Vol 81 (13) ◽  
pp. 4376-4387 ◽  
Author(s):  
Zhiyao Luo ◽  
Ganyu Gu ◽  
Amber Ginn ◽  
Mihai C. Giurcanu ◽  
Paige Adams ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Geometric Mean ◽  
Multidrug Resistant ◽  
Most Probable Number ◽  
Sample Type ◽  
Probable Number ◽  
Content Type ◽  
Safety Standards ◽  
Produce Contamination ◽  
Southern Georgia

ABSTRACTIrrigation water has been implicated as a likely source of produce contamination bySalmonella enterica. Therefore, the distribution ofS. entericawas surveyed monthly in irrigation ponds (n= 10) located within a prime agricultural region in southern Georgia and northern Florida. All ponds and 28.2% of all samples (n= 635) were positive forSalmonella, with an overall geometric mean concentration (0.26 most probable number [MPN]/liter) that was relatively low compared to prior reports for rivers in this region.Salmonellapeaks were seasonal; the levels correlated with increased temperature and rainfall (P< 0.05). The numbers and occurrence were significantly higher in water (0.32 MPN/liter and 37% of samples) than in sediment (0.22 MPN/liter and 17% of samples) but did not vary with depth. Representative isolates (n= 185) from different ponds, sample types, and seasons were examined for resistance to 15 different antibiotics; most strains were resistant to streptomycin (98.9%), while 20% were multidrug resistant (MDR) for 2 to 6 antibiotics. DiversiLab repetitive extragenic palindromic-element sequence-based PCR (rep-PCR) revealed genetic diversity and showed 43 genotypes among 191 isolates, as defined by >95% similarity. The genotypes did not partition by pond, season, or sample type. Genetic similarity to known serotypes indicated Hadar, Montevideo, and Newport as the most prevalent. All ponds achieved the current safety standards for genericEscherichia coliin agricultural water, and regression modeling showed that theE. colilevel was a significant predictor for the probability ofSalmonellaoccurrence. However, persistent populations ofSalmonellawere widely distributed in irrigation ponds, and the associated risks for produce contamination and subsequent human exposure are unknown, supporting continued surveillance of this pathogen in agricultural settings.

Effects of Dry Storage and Resubmersion of Oysters on Total Vibrio vulnificus and Total and Pathogenic (tdh+/trh+) Vibrio parahaemolyticus Levels

2015 ◽  
Vol 78 (8) ◽  
pp. 1574-1580 ◽  
Author(s):  
THOMAS P. KINSEY ◽  
KERI A. LYDON ◽  
JOHN C. BOWERS ◽  
JESSICA L. JONES
Keyword(s):  
Vibrio Parahaemolyticus ◽  
Storage Time ◽  
Vibrio Vulnificus ◽  
Ambient Air ◽  
Most Probable Number ◽  
Probable Number ◽  
Ambient Temperatures ◽  
Dry Storage ◽  
Hemolysin Gene ◽  
Thermostable Direct Hemolysin

Vibrio vulnificus (Vv) and Vibrio parahaemolyticus (Vp) are the two leading causes of bacterial illnesses associated with raw shellfish consumption. Levels of these pathogens in oysters can increase during routine antifouling aquaculture practices involving dry storage in ambient air conditions. After storage, common practice is to resubmerge these stored oysters to reduce elevated Vv and Vp levels, but evidence proving the effectiveness of this practice is lacking. This study examined the changes in Vv and in total and pathogenic (thermostable direct hemolysin gene and the tdh-related hemolysin gene, tdh+ and trh+) Vp levels in oysters after 5 or 24 h of dry storage (28 to 32°C), followed by resubmersion (27 to 32°C) for 14 days. For each trial, replicate oyster samples were collected at initial harvest, after dry storage, after 7 days, and after 14 days of resubmersion. Oysters not subjected to dry storage were collected and analyzed to determine natural undisturbed vibrio levels (background control). Vibrio levels were measured using a most-probable-number enrichment followed by real-time PCR. After storage, vibrio levels (excluding tdh+ and trh+ Vp during 5-h storage) increased significantly (P &lt; 0.001) from initial levels. After 7 days of resubmersion, Vv and total Vp levels (excluding total Vp in oysters stored for 5 h) were not significantly different (P &gt; 0.1) from levels in background oysters. Vv and total and pathogenic Vp levels were not significantly different (P &gt; 0.1) from levels in background oysters after 14 days of resubmersion, regardless of dry storage time. These data demonstrate that oyster resubmersion after dry storage at elevated ambient temperatures allows vibrio levels to return to those of background control samples. These results can be used to help minimize the risk of Vv and Vp illnesses and to inform the oyster industry on the effectiveness of routine storing and resubmerging of aquaculture oysters.

Prevalence, Concentrations, and Antibiotic Sensitivities of Salmonella Serovars in Poultry from Retail Establishments in Seattle, Washington

2014 ◽  
Vol 77 (6) ◽  
pp. 885-893 ◽  
Author(s):  
E. MAZENGIA ◽  
M. SAMADPOUR ◽  
H. W. HILL ◽  
K. GREESON ◽  
K. TENNEY ◽  
...  
Keyword(s):  
Significant Proportion ◽  
Performance Standards ◽  
Production Method ◽  
Immunomagnetic Separation ◽  
Product Type ◽  
Most Probable Number ◽  
Probable Number ◽  
Critical Data ◽  
Data Gaps ◽  
Processed Products

Poultry have been identified as one of the major sources of salmonellosis, with estimates ranging from 10 to 22% of total cases. Despite several advances in the industry and new performance standards, the incidence of salmonellosis in the population has not declined over the last 15 years. Salmonella is pervasive in a wide variety of foods, and thus, estimating its burden resulting from specific food categories has been challenging and plagued with uncertainty due to critical data gaps. The objective of this study was to conduct a year-long market survey (1,322 samples) to help bridge the data gaps on the contamination rates and levels of Salmonella on raw poultry by product type (i.e., breast, thighs, drums, wings, and split breast) and production method (conventional versus organic). The isolates recovered were serotyped and tested for antibiotic sensitivities. A PCR method was utilized for initial screening of samples after an overnight enrichment in tryptic soy broth. Three-tube most-probable-number (MPN) assays and anti-Salmonella immunomagnetic separation methods were utilized to determine the levels of Salmonella and aid with the recovery of Salmonella species, respectively. Eleven percent of the samples were positive for Salmonella. Significant differences in percent positive rates by product type included up to a 4-fold difference in percent positive rates between establishments, ranging from 7 to 31%. Of the samples positive for Salmonella species, 94% had &lt;30 MPN/100 g. Production methods identified as organic or as not using antibiotics had significantly higher rates of recovery of Salmonella. On the other hand, all of the Salmonella isolates that were resistant to two or more antibiotics originated from conventional processing establishments where antibiotics were utilized. In addition, a significant proportion of isolates from conventionally processed products were serotypes clinically relevant to humans.

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