Cause Of Foodborne Illness Research Articles

Characterisation of antibiotic resistant Staphylococcus species and molecular identification of mecA and toxic shock syndrome toxin-1 (tsst-1) genes of Staphylococcus aureus isolates from cows' milk

Staphylococcus aureus (S. aureus) is one of the most important causes of foodborne illness. Due to the interest of people to use traditional dairy products, especially milk, in the current descriptive study the frequency of S. aureus, antibiotic resistance pattern and presence of toxic shock syndrome toxin-1 gene (tsst-1 gene) in these isolated strains was investigated. Thirty-nine strains (26%) of S. aureus were identified from the samples studied, of which 6 (15.38%) were resistant to methicillin, and 9 (23.07%) were positive for mecA gene. Also, 31 (20.7%) coagulase-negative staphylococci isolates were identified. Out of the 39 strains of S. aureus, the presence of tsst gene was detected in 1 strain (2.56%). Therefore, S. aureus contamination indicates a risk to public health and can be significantly controlled using a high level of hygiene and professional training in the handling of raw milk.

Occurrence of Campylobacter spp. in neck skins and fresh chicken meat as a leading cause of bacterial food poisoning

Jedan od vodećih mikroorganizama koji uzrokuje bakterijsko trovanje hranom su bakterije roda Campylobacter koje prouzroče kampilobakteriozu, zoonozu koja je od 2005. godine najčešće prijavljivana bolest uzrokovana hranom u Europskoj Uniji te kao takva predstavlja javno-zdravstveni problem. Najprisutnijim izvorom ovog patogena smatra se pileće meso s obzirom da su kampilobakteri uobičajeni komenzali u probavnom sustavu peradi. S obzirom da se nalaze u crijevima peradi, osim prilikom procesa klanja i obrade mesa, velika mogućnost kontaminacije javlja se u kasnijim fazama proizvodnje kao što su: čupanje perja, evisceracija, pranje, pohranjivanje i hlađenje te kontaminacija putem ruku radnika, opreme ili same okoline, a pretpostavlja se da upravo koža peradi predstavlja glavni izvor ovog patogena. U ovom je radu određivan broj bakterija Campylobacter spp. u uzorcima kože vratova tovnih pilića, pilećih prsa bez kože, pilećih krilaca i pilećih bataka ‒ zabataka. Za određivanje broja kolonija korištena je standardna metoda za određivanje broja Campylobacter spp. prema ISO normiranoj metodi HRN EN ISO 10272 – 2:2017.

The Use of Phage Cocktail and Various Antibacterial Agents in Combination to Prevent the Emergence of Phage Resistance.

Bacterial food poisoning cases due to Salmonella and E. coli O157:H7 have been linked with the consumption of a variety of food products, threatening public health around the world. This study describes the combined effects of a phage cocktail (STG2, SEG5, and PS5), EDTA, nisin, and polylysine against the bacterial cocktail consisting of S. typhimurium, S. enteritidis, and E. coli O157:H7. Overall, phage cocktail (alone or in combination with nisin or/and polylysine) not only showed great antibacterial effects against bacterial cocktail at different temperatures (4 °C, 24 °C, and 37 °C), but also totally inhibited the emergence of phage resistance during the incubation period. These results suggest that the combination of phages with nisin or/and polylysine has great potential to simultaneously control S. typhimurium, S. enteritidis, and E. coli O157:H7.

Whole-genome sequencing and phylogenetic analysis capture the emergence of a multi-drug resistant Salmonella enterica serovar Infantis clone from diagnostic animal samples in the United States.

Salmonella enterica is a major cause of foodborne illness in the United States. A multi-drug resistant (MDR) emergent Salmonella Infantis (ESI) with a megaplasmid (pESI) was first identified in Israel and Italy and subsequently reported worldwide. The ESI clone carrying an extended spectrum β-lactamase blaCTX-M-65 on a pESI-like plasmid and a mutation in the gyrA gene has recently been found in the United States in poultry meat. We analyzed the phenotypic and genotypic antimicrobial resistance, genomics and phylogeny of 200 S. infantis isolates from animal diagnostic samples. Of these, 33.5% were resistant to at least one antimicrobial and 19.5% were multi-drug resistant (MDR). Eleven isolates from different animal sources were phenotypically and genetically similar to the ESI clone. These isolates had a D87Y mutation in the gyrA gene conferring reduced susceptibility to ciprofloxacin and harbored a combination of 6-10 resistance genes: blaCTX-M-65, aac(3)-IVa, aadA1, aph(4)-Ia, aph(3')-Ia, floR, sul1, dfrA14, tetA, and fosA. These 11 isolates carried class I and class II integrons and three virulence genes: sinH, involved in adhesion and invasion, ybtQ and ybtP, associated with iron transport. These isolates were also closely related to each other (separated by 7 to 27 SNPs) and phylogenetically related to the ESI clone recently found in the U.S. This dataset captured the emergence of the MDR ESI clone in multiple animal species and the first report of a pESI-like plasmid in isolates from horses in the U.S.

Development of Recombinase Aided Amplification (RAA)-Exo-Probe Assay for the Rapid Detection of Shiga Toxin-Producing Escherichia coli.

Shiga toxin-producing Escherichia coli (STEC) is a significant cause of foodborne illness causing various gastrointestinal diseases including hemolytic uremic syndrome (HUS), the most severe form, which can lead to kidney failure or even death. Here, we report the development of recombinase aided amplification (RAA)-exo-probe assays targeting the stx1 and stx2 genes for the rapid detection of STEC in food samples. Primers and exo-probes were designed and optimized for the detection of stx1 and stx2 using RAA technology. The optimal STEC RAA-exo-probe assays were then tested for specificity and sensitivity, and validated in both spiked and real food samples. These assays were found to be 100% specific to STEC strains and were also highly sensitive with a detection limit of 1.6 × 103 CFU/mL or 32 copies/reaction. Importantly, the assays were able to successfully detect STEC in spiked and real food samples (beef, mutton, and pork), with a detection limit as low as 0.35 CFU/25g in beef samples after an overnight enrichment step. Overall, the RAA assay reactions completed within ∼20 min and were less dependent on expensive equipment, suggesting they can be easily adopted for in-field testing requiring only a fluorescent reader. As such, we have developed two rapid, sensitive, and specific assays that can be used for the routine monitoring of STEC contamination in food samples, particularly in the field or in poorly equipped labs.

Evidence for the efficacy of pre-harvest agricultural practices in mitigating food-safety risks to fresh produce in North America

Consumption of contaminated produce remains a leading cause of foodborne illness. Increasingly, growers are altering agricultural practices and farm environments to manage food-safety hazards, but these changes often result in substantial economic, social, and environmental costs. Here, we present a comprehensive evidence synthesis evaluating the efficacy of soil, non-crop vegetation, animal, landscape, and irrigation water management strategies aimed at reducing produce-safety risk in North America. We systematically summarized findings from 78 peer-reviewed papers on the effect of 21 management practices on the prevalence, abundance, or survival of four foodborne pathogens (i.e., E. coli, Salmonella spp., Listeria spp., and Campylobacter spp.), resulting in 113 summaries. We then organized a 30-member expert panel, who used these summaries to evaluate the impact of each practice on food-safety outcomes. While more than half of the practices were too understudied to confidently evaluate their impact on food safety, the panel did identify several practices that were associated with reduced preharvest food-safety risks, including not using raw manure, separating crop and livestock production, and choosing low-risk irrigation sources. The panel also identified practices that appear ineffective at reducing food-safety risks, such as the removal of non-crop vegetation. Overall, these findings provide insights into the food-safety impacts of agricultural and land management practices that growers, auditors, and extension personnel can use to co-manage produce preharvest environments for food safety and other aims.

Identifying Predictors of Safe Food Handling Practices among Canadian Households with Children Under Eighteen Years

Poor food handling practices at home are a common cause of foodborne illness. Children are more susceptible to foodborne illness than adults. Because children’s food safety depends on the safe food handling practices of parents and caregivers, this study aims to identify determinants of safe food handling practices among Canadian families with children under 18 years. Data for Canadian households with children (n = 294) were extracted from a larger telephone survey conducted across all Canadian provinces and territories between 2014 and 2015. Four food safety practice outcomes and six demographic variables were examined using multivariable logistics regression. Most survey participants were females (56%) who had less than a bachelor’s degree (67%) and were caring for one child (55%). Approximately 90% of caregivers reported proper hand hygiene, and 79% refrigerated leftovers within 2 h of cooking. Only 33% of caregivers reported preventing cross-contamination, and fewer reported using food thermometers for poultry cuts (13%) and hamburgers (11%). Those in the higher income and education categories were less likely to follow safe food handling practices such as hand hygiene and safe refrigeration of leftovers. This research highlights the need for food safety interventions that target Canadian families with children within certain demographic groups.

Identifying Predictors of Safe Food Handling Practices among Canadian Households with Children Under Eighteen Years

Poor food handling practices at home are a common cause of foodborne illness. Children are more susceptible to foodborne illness than adults. Because children’s food safety depends on the safe food handling practices of parents and caregivers, this study aims to identify determinants of safe food handling practices among Canadian families with children under 18 years. Data for Canadian households with children (n = 294) were extracted from a larger telephone survey conducted across all Canadian provinces and territories between 2014 and 2015. Four food safety practice outcomes and six demographic variables were examined using multivariable logistics regression. Most survey participants were females (56%) who had less than a bachelor’s degree (67%) and were caring for one child (55%). Approximately 90% of caregivers reported proper hand hygiene, and 79% refrigerated leftovers within 2 h of cooking. Only 33% of caregivers reported preventing cross-contamination, and fewer reported using food thermometers for poultry cuts (13%) and hamburgers (11%). Those in the higher income and education categories were less likely to follow safe food handling practices such as hand hygiene and safe refrigeration of leftovers. This research highlights the need for food safety interventions that target Canadian families with children within certain demographic groups.

Evaluation of Alternative Colony Hybridization Methods for Pathogenic Vibrios

Vibrios, such as Vibrio parahaemolyticus, are naturally occurring halophilic bacteria that are a major cause of foodborne illness. Because of their autochthonous nature, managing vibrio levels in marine and estuarine environments is impossible. Instead, it is crucial to reliably enumerate their abundance to minimize human exposure. One method of achieving this is the direct plating/colony hybridization (DP/CH) method, which has been used to efficiently quantify pathogenic vibrios in oysters and other seafood products. Although successful, the method relies on proprietary resources. We examined alternative approaches, assessed the influence of the reagent suppliers' source on enumeration accuracy, and made experimental adjustments that maximized efficiency, sensitivity, and specificity. We report here that in-house conjugation via Cell Mosaic is a viable alternative to the previously available sole-source distributor of the alkaline phosphatase-conjugated probes used to enumerate vibrios in oysters. We also report that milk was a viable alternative as a blocking reagent, pH must be eight, an orbital shaker was a viable alternative to a water bath, and narrow polypropylene containers were a viable alternative to Whirl-Pak bags. These modifications will be crucial to scientists enumerating vibrios and other pathogens in food products.

Optimized Bioorthogonal Non-canonical Amino Acid Tagging to Identify Serotype-Specific Biomarkers in Verotoxigenic Escherichia coli.

According to Canada's Food Report Card 2016, there are 4 million foodborne illnesses acquired each year in the nation alone. The leading causes of foodborne illness are pathogenic bacteria such as shigatoxigenic/verotoxigenic Escherichia coli (STEC/VTEC) and Listeria monocytogenes. Most current detection methods used to identify these bacterial pathogens are limited in their validity since they are not specific to detecting metabolically active organisms, potentially generating false-positive results from non-living or non-viable bacteria. Previously, our lab developed an optimized bioorthogonal non-canonical amino acid tagging (BONCAT) method which allows for the labeling of translationally active wild-type pathogenic bacteria. Incorporation of homopropargyl glycine (HPG) into the cellular surfaces of bacteria allows for protein tagging using the bioorthogonal alkyne handle to report on the presence of pathogenic bacteria. Here, we use proteomics to identify more than 400 proteins differentially detected by BONCAT between at least two of five different VTEC serotypes. These findings pave the way for future examination of these proteins as biomarkers in BONCAT-utilizing assays.

An Overview of the Public Health Challenges in Diagnosing and Controlling Human Foodborne Pathogens.

Pathogens found in food are believed to be the leading cause of foodborne illnesses; and they are considered a serious problem with global ramifications. During the last few decades, a lot of attention has been paid to determining the microorganisms that cause foodborne illnesses and developing new methods to identify them. Foodborne pathogen identification technologies have evolved rapidly over the last few decades, with the newer technologies focusing on immunoassays, genome-wide approaches, biosensors, and mass spectrometry as the primary methods of identification. Bacteriophages (phages), probiotics and prebiotics were known to have the ability to combat bacterial diseases since the turn of the 20th century. A primary focus of phage use was the development of medical therapies; however, its use quickly expanded to other applications in biotechnology and industry. A similar argument can be made with regards to the food safety industry, as diseases directly endanger the health of customers. Recently, a lot of attention has been paid to bacteriophages, probiotics and prebiotics most likely due to the exhaustion of traditional antibiotics. Reviewing a variety of current quick identification techniques is the purpose of this study. Using these techniques, we are able to quickly identify foodborne pathogenic bacteria, which forms the basis for future research advances. A review of recent studies on the use of phages, probiotics and prebiotics as a means of combating significant foodborne diseases is also presented. Furthermore, we discussed the advantages of using phages as well as the challenges they face, especially given their prevalent application in food safety.

Contribution of GalU to biofilm formation, motility, antibiotic and serum resistance, and pathogenicity of Salmonella Typhimurium.

Salmonella Typhimurium is the leading cause of foodborne illnesses in China, resulting in major epidemics and economic losses in recent years. Uridine diphosphate-glucose pyrophosphorylase galU plays an important role in thebiosynthesis of the bacterial envelope. Herein, we evaluated the role of galU in S. Typhimurium infection in chicken. A galU gene mutant was successfully constructed by red homologous recombination technology, and biological characteristics were studied. The galU mutant strain had a rough phenotype;was defective in biofilm formation, autoagglutination, and motility; exhibited greater sensitivity to most antibiotics, serum, and egg albumen; and had lowercapacity for adhesion to chicken embryo fibroblasts cell line (DF-1). The galU mutant showed dramatically attenuated pathogenicity in chicken embryos (100,000-fold), BALB/c mice (420-fold), and chicks (100-fold). The results imply that galU is an important virulence factor in the pathogenicity of S. Typhimurium, and it may serve a target for the development of veterinary drugs, providing a theoretical basis for the prevention and control of S. Typhimurium.

Stimulation of Surface Polysaccharide Production under Aerobic Conditions Confers Aerotolerance in Campylobacter jejuni.

The ability of a foodborne pathogen to tolerate environmental stress critically affects food safety by increasing the risk of pathogen survival and transmission in the food supply chain. Campylobacter jejuni, a leading bacterial cause of foodborne illnesses, is an obligate microaerophile and is sensitive to atmospheric levels of oxygen. Currently, the molecular mechanisms of how C. jejuni withstands oxygen toxicity under aerobic conditions have not yet been fully elucidated. Here, we show that when exposed to aerobic conditions, C. jejuni develops a thick layer of bacterial capsules, which in turn protect C. jejuni under aerobic conditions. The presence of both capsular polysaccharides and lipooligosaccharides is required to protect C. jejuni from excess oxygen in oxygen-rich environments by alleviating oxidative stress. Under aerobic conditions, C. jejuni undergoes substantial transcriptomic changes, particularly in the genes of carbon metabolisms involved in amino acid uptake, the tricarboxylic acid (TCA) cycle, and the Embden-Meyerhof-Parnas (EMP) pathway despite the inability of C. jejuni to grow aerobically. Moreover, the stimulation of carbon metabolism by aerobiosis increases the level of glucose-6-phosphate, the EMP pathway intermediate required for the synthesis of surface polysaccharides. The disruption of the TCA cycle eliminates aerobiosis-mediated stimulation of surface polysaccharide production and markedly compromises aerotolerance in C. jejuni. These results in this study provide novel insights into how an oxygen-sensitive microaerophilic pathogen survives in oxygen-rich environments by adapting its metabolism and physiology. IMPORTANCE Oxygen-sensitive foodborne pathogens must withstand oxygen toxicity in aerobic environments during transmission to humans. C. jejuni is a major cause of gastroenteritis, accounting for 400 million to 500 million infection cases worldwide per year. As an obligate microaerophile, C. jejuni is sensitive to air-level oxygen. However, it has not been fully explained how this oxygen-sensitive zoonotic pathogen survives in aerobic environments and is transmitted to humans. Here, we show that under aerobic conditions, C. jejuni boosts its carbon metabolism to produce a thick layer of bacterial capsules, which in turn act as a protective barrier conferring aerotolerance. The new findings in this study improve our understanding of how oxygen-sensitive C. jejuni can survive in aerobic environments.

Characterization of Phage vB_SalM_SPJ41 and the Reduction of Risk of Antibiotic-Resistant Salmonella enterica Contamination in Two Ready-to-Eat Foods

Salmonella enterica is a major cause of foodborne illness, and the emergence of antibiotic-resistant bacteria has led to huge pressures on public health. Phage is a promising strategy for controlling foodborne pathogens. In this study, a novel Salmonella phage vB_SalM_SPJ41 was isolated from poultry farms in Shanghai, China. Phage vB_SalM_SPJ41 was able to lyse multiple serotypes of antibiotic-resistant S. enterica, including S. Enteritidis, S. Typhimurium, S. Shubra, S. Derby, and S. Nchanga. It had a short incubation period and was still active at a temperature <80 °C and in the pH range of 3~11. The phage can effectively inhibit the growth of S. enterica in liquid culture and has a significant inhibitory and destructive effect on the biofilm produced by antibiotic-resistant S. enterica. Moreover, the phage was able to reduce S. Enteritidis and MDR S. Derby in lettuce to below the detection limit at 4 °C. Furthermore, the phage could reduce S. Enteritidis and S. Derby in salmon below the limit of detection at 4 °C, and by 3.9 log10 CFU/g and· 2.1 log10 CFU/g at 15 °C, respectively. In addition, the genomic analysis revealed that the phages did not carry any virulence factor genes or antibiotic resistance genes. Therefore, it was found that vB_SalM_SPJ41 is a promising candidate phage for biocontrol against antibiotic-resistant Salmonella in ready-to-eat foods.

Distribution of Virulence Genes in Campylobacter spp. Isolated from Agaricus Mushrooms in Iran.

The white button mushroom (Agaricus) is a significant nutritional and therapeutic species utilized in the human diet and could transmit various bacterial infections. Campylobacter species are the most common cause of foodborne illness across the world. The present study has been planned to determine the frequency of virulence genes and antibiotic susceptibility test in Campylobacter spp. recovered from Agaricus mushroom. In this study, 740 Agaricus mushroom samples were gathered randomly from various markets from June 2020 to December 2020. Confirmation of Campylobacter spp. using biochemical analyses and 23S rRNA-based PCR was performed. The agar dilution technique was used to determine resistance to antibiotics using gentamicin (GM10μg), ciprofloxacin (CIP5μg), nalidixic acid (NA30μg), tetracycline (TE30μg), ampicillin (AM10μg), amoxicillin+ clavulanic acid (AMC30μg), erythromycine (E15μg), azithromycin (AZM15μg), clindamycin (CC2μg), and chloramphenicol (C30μg). Multiplex PCR was utilized to determine the prevalence of the recR, dnaJ, wlaN, virBll, cdtC, cdtB, cdtA, flaA, cadF, pidA, ciaB, ceuE, and cgtB genes. Campylobacter spp. were detected in 74 out of 740 Agaricus mushroom samples (10%). According to the data, Agaricus mushroom samples included 32 (4.32%) C. jejuni, 11 (1.48%) C. coli, and 31 (4.18%) other Campylobacter spp. Antimicrobial resistance was most common in C. jejuni isolates. C. jejuni isolates also had the lowest resistance rate to gentamycin, ciprofloxacin, and nalidixic acid. C. coli isolates were reported to have the highest antimicrobial resistance to ciprofloxacin, ampicillin, and erythromycine. Resistance to gentamycin and amoxicillin+ clavulanic acid was likewise lowest among C. coli strains. The flaA and ciaB genes were found in 100% of B-lactams-susceptible C. jejuni and C. coli strains. When examining the relationship between antibiotic resistance and the existence of virulence genes, it was observed that there is a statistically significant relationship (p < 0.001) between bacterial resistance and virulence genes. Our findings indicated that changes in resistance patterns in Campylobacter strains have emerged from multiple treatment approaches in Agaricus mushrooms.

Prevalence, Contamination Level, and Associated Factors of Methicillin-Resistant Staphylococcus aureus in Raw Cow Milk at Selected Districts of Gamo Zone, Southern Ethiopia.

Staphylococcus aureus is pathogenic bacterium contaminating milk and milk products causing bacterial food poisoning. In the current study sites, there is no information on methicillin-resistant Staphylococcus aureus. Thus, the current study sought to assess the risk factors that contribute to the contamination of raw cow milk, the bacterial load, and the prevalence of methicillin-resistant Staphylococcus aurous. A cross-sectional study was conducted, January to December, 2021, on randomly selected 140 milk samples from selling point of Arba Minch Zuria and Chencha districts. Fresh milk samples were processed and tested for bacterial load, bacterial isolation, and methicillin susceptibility patterns. Questionnaire survey was conducted on 140 producers and collectors to assess hygienic factors attributed to contamination of raw cow milk with Staphylococcus aureus. The overall prevalence of S. aureus was 42.1% (59/140) (95% confidence interval (CI): 34.80-51.40%). About 15.6% (22/140) of the milk samples assessed had the viable count and total S. aureus count higher than 5log cfu/mL with 5.3 + 1.68 and 1.36 + 1.7log cfu/ml-1 bacterial loads, respectively. The rate of isolation of S. aureus was significantly high in milk from highland than lowland (p=0.030). The multivariable logistic regression revealed that educational status (OR: 6.00; 95% CI: 4.01-8.07), picking one's nose while working on milk (OR: 1.41; 95% CI: 0.54-2.25), cleaning the milk can (OR: 4.5; 95% CI: 2.61-5.17), hand washing activities (OR: 3.4; 95% CI: 1.670-6.987), check for abnormal milk (OR: 2; 95% CI: 1.55-2.75), and container for milk (OR: 3; 95% CI: 0.12-0.67) were risk factors significantly associated with the occurrence of S. aureus in milk. In conclusion, the highest rate of resistance was observed to ampicillin (84.7%) and cefoxitin (76.3%). All isolates are resistant to at least two types of antimicrobial drugs, while 65.0% of the isolates were found to be multidrug-resistant. The higher prevalence, high load, and antimicrobial resistance of S. aureus indicate the higher public health risk due to the widespread consumption of raw milk in the area. Furthermore, consumers in the study area should be aware of the risks associated with consuming raw milk.

Estimation of Bacteriophage MS2 Inactivation Parameters During Microwave Heating of Frozen Strawberries

Frozen berries have been repeatedly linked to acute gastroenteritis caused by norovirus, the most common cause of foodborne illness in the United States. Many guidelines recommend that frozen berries be microwaved for at least 2 min, but it is unclear if this thermal treatment is effective at inactivating norovirus. The objective of this study was to model the effect of microwave heating at varying power levels on the survival of bacteriophage MS2, a norovirus surrogate, when inoculated onto frozen strawberries. Bacteriophage MS2 was inoculated onto the surface of frozen strawberries with a starting concentration of approximately 10 log PFU/g. Samples (either 3 or 5 whole strawberries) were heated in a 1300-Watt domestic research microwave oven (frequency of 2450 MHz) at power levels of 30, 50, 70, and 100% (full power), for times ranging from 15 to 300 s to determine inactivation. Temperatures at berry surfaces were monitored during heating using fiberoptic thermometry. All experiments were conducted in triplicate. The primary model for thermal inactivation was a log-linear model of logN vs. time. The secondary model was for a D-value decreasing linearly with temperature and an added term that was path-dependent on the thermal history. Parameters in the model were estimated using dynamic temperature history at the surface of the berry, via nonlinear regression using all data simultaneously. The root mean square error was ∼0.5 PFU/g out of a total 6-log reduction. Log reductions of 1.1 ± 0.4, 1.5 ± 0.5, 3.1 ± 0.1, and 3.8 ± 0.2 log PFU/g were observed for 30, 50, 70, and 100% microwave power levels when three berries were heated for 60 s. D-values were 21.4 ± 1.95 s and 10.6 ± 1.1 s at 10 and 60°C, respectively. This work demonstrates an approach to estimate inactivation parameters for viruses from dynamic temperature data during microwave heating. These findings will be useful in predicting the safety effect of microwave heating of berries in the home or food service.

A lanthanide-based high-sensitivity fluorescence method for the on-site rapid detection of thermostable direct hemolysin of Vibrio parahaemolyticus

Vibrio parahaemolyticus is a common foodborne pathogen in seafood, which often causes seafood borne bacterial gastroenteritis or food poisoning. Thermostable direct hemolysin (TDH) is considered to be one of the main virulence factors involved in this pathogen. The most clinical V. parahaemolyticus isolates produce TDH. Therefore, high sensitivity and specificity detection of TDH are of great significance for food safety and early diagnosis of diseases caused by V. parahaemolyticus. In this study, we developed a rapid, sensitive immunochromatographic test paper assay for the quantitative detection of TDH in seafood samples using time-resolved fluorescence techniques. First, we completed the preparation of fluorescent detection antibodies by coupling lanthanide fluorescent nanospheres with homemade high-affinity polyclonal antibodies based on the principle of the double-antibody sandwich. The lanthanide fluorescent nanospheres used in this study are characterized by a large stokes shift and a long fluorescence lifetime, which effectively reduces background noise and improves detection sensitivity. In addition, the method can be completed within 15 min for the detection of TDH, has a detection limit below 50 ng/mL and good linearity in the range of 50–5000 ng/mL. Moreover, it has good specificity and no cross-reactivity with Vibrio vulnificus hemolysin (VVH), Clostridium perfringens α toxin (CPA) or C. perfringens ε toxin (ETX). Finally, the sensitivity of this method was unchanged when the three simulated samples of Patinopecten yessoensis, Ruditapes philippinarum, and Scapharca broughtonii tested, indicating that the method is not affected by samples in a complex matrix. In conclusion, this study establishes a practical new method for on-site rapid detection of TDH, which is easy to operate, fast response, easy to carry and can be implemented under the field conditions without expensive equipment and professional person.

2010. Severity of antimicrobial-resistant non-Typhoidal Salmonella infections treated in two large facilities of a health system in Pennsylvania, 2018-2020

Abstract Background Nontyphoidal Salmonella (NTS) is a leading cause of foodborne illness. Characterization of clinical outcomes of salmonellosis from antimicrobial-resistant (AMR) NTS is limited. The Pennsylvania Department of Health collaborated with federal and academic partners to enhance surveillance for NTS (AMR and outcomes). Methods We evaluated 82 patients with salmonellosis whose NTS isolates were submitted to the PA Public Health Laboratory during 2018–2020 from two Pennsylvania hospitals. We used broth microdilution to test NTS isolates for susceptibility to antibiotics tracked by the National Antimicrobial Resistance Monitoring System. Isolates resistant to ≥3 antimicrobial classes were considered multidrug-resistant (MDR). Electronic medical records of source patients were reviewed for medical history, diagnoses, treatment, and outcomes. Invasive infection was defined as isolation from normally sterile sites (e.g., blood). Results Seven (9%) of 82 isolates were MDR. Twelve (15%) had decreased susceptibility to ciprofloxacin (MIC ≥0.12 µg/mL), 3 (4%) were ceftriaxone resistant, 3 (4%) were trimethoprim-sulfamethoxazole resistant, and 1 (1%) was azithromycin resistant. The median patient age was 29 years; 31 (38%) patients were ≤18 years and 42 (51%) were female. Nearly a quarter of all patients were immunosuppressed (Figure). Outcomes included hospital admission in 38 (46%), intensive care for 5 (6%) patients, and 1 (1%) death. Ten (12%) patients had invasive infections, including 8 with bacteremia; all were hospitalized. Four (40%) of the invasive disease isolates were resistant to ≥1 antimicrobial, compared with 16 (22%) isolates from patients with the non-invasive disease. Fifty-seven (70%) patients were prescribed empiric antimicrobials for their infection. Antibiotics were changed in 45 (79%) after laboratory diagnosis. Demographic and clinical characteristics of patients with nontyphoidal Salmonella treated in two facilities associated with a health system in Pennsylvania, 2018–2020. The five patients treated in intensive care units are included in the total admissions (n=38). Salmonellosis was considered invasive if the organism was isolated from the blood or other normally sterile site (excluding urine). Conclusion NTS can cause severe invasive illness in some patients; drug-resistant NTS infections may be associated with more severity as compared with susceptible NTS. Resistance to clinically consequential drugs coupled with the severity of infections suggests the need for antimicrobial stewardship and highlights the value of clinical data in enhancing surveillance for salmonellosis. Disclosures All Authors: No reported disclosures.

Human Listeriosis.

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that can cause severe invasive infections upon ingestion with contaminated food. Clinically, listerial disease, or listeriosis, most often presents as bacteremia, meningitis or meningoencephalitis, and pregnancy-associated infections manifesting as miscarriage or neonatal sepsis. Invasive listeriosis is life-threatening and a main cause of foodborne illness leading to hospital admissions in Western countries. Sources of contamination can be identified through international surveillance systems for foodborne bacteria and strains' genetic data sharing. Large-scale whole genome studies have increased our knowledge on the diversity and evolution of L. monocytogenes, while recent pathophysiological investigations have improved our mechanistic understanding of listeriosis. In this article, we present an overview of human listeriosis with particular focus on relevant features of the causative bacterium, epidemiology, risk groups, pathogenesis, clinical manifestations, and treatment and prevention.