Survival of foodborne pathogens ( Escherichia coli O157:H7, Salmonella Typhimurium, Staphylococcus aureus , Listeria monocytogenes , and Vibrio parahaemolyticus ) in raw ready-to-eat crab marinated in soy sauce

The effect of emulsifier type and oil fraction on Salmonella Typhimurium growth and thermal inactivation in oil-in-water emulsion

High water activity oil-in-water emulsions can promote survival and growth of Salmonella Typhimurium. Nevertheless, the precise effect of emulsifier type and oil content on bacterial growth and inactivation is not fully understood. Here, emulsions were prepared using different emulsifiers (Tween 20, Tween 80, and Triton X-100) and different oil fractions (20%, 40%, and 60% (v/v)). TSB (control), emulsifier solutions, and emulsions were inoculated with S. Typhimurium. Bacterial growth rate was measured at 7, 22, and 37°C, whereas thermal inactivation was performed at 55°C. Growth and inactivation data was fitted into Logistic and Weibull models, respectively. At an incubation temperature of 37°C, the presence of high amount of oil (60%) in Tween 20 and Triton X stabilized emulsions extended the lag phase (5.83 ± 2.20 and 9.43 ± 1.07 h, respectively, compared to 2.28 ± 1.54 h for TSB, p < 0.05), whereas individual emulsifiers had no effect on growth behavior compared to TSB. This effect was also prevalent but attenuated at 22°C, whereas no growth was observed at 7°C. In thermal inactivation, we observed protective effect in Tween 80 and Triton X-100 solutions, where time required for five-log reduction was 1914.70 ± 706.35 min and 795.34 ± 420.09 min, respectively, compared to 203.89 ± 10.18 min for TSB (p < 0.05). Interestingly, the presence of high amount of oil did not offer protective effect during thermal inactivation. We hypothesize that oleic acid in Tween 80 and lower hydrophobicity value of Triton X-100 help maintain membrane integrity and improve the resistance of bacteria to heat inactivation.

Antimicrobial effect of dried koruk (Vitis vinifera L.) pomace against food-borne pathogens inoculated in kofte

This study aimed to investigate the antimicrobial effects of various concentrations of dried koruk pomace (1%, 1.5%, and 2%) used in kofte formulations. To detect the inactivation effect of dried koruk pomace on food-borne pathogens, kofte samples were separately inoculated with Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium at high and low levels. During the storage period, E. coli O157:H7, L. monocytogenes, and S. Typhimurium counts of the samples inoculated with high levels were decreased in the range of 1.1-1.3 log CFU/g, 0.1-0.2 log CFU/g and 1.1-1.2 log CFU/g, respectively. When low inoculum levels were used, E. coli O157:H7 and S. Typhimurium counts of the samples were reduced to an undetectable level at the beginning and after 2 months of storage, respectively. Although L. monocytogenes counts of the samples were reduced to an undetectable level immediately, the counts were increased during storage till the end of the fifth month. The results indicated that dried koruk pomace was more effective in eliminating E. coli O157:H7 and S. Typhimurium than L. monocytogenes inoculated in kofte. The results suggest that using dried koruk pomace in kofte formulations is an effective method to improve the safety of the products, especially when low levels of contamination occur.

Characterization of ready-to-eat fish surface as a potential source of contamination of Vibrio parahaemolyticus biofilms

The worldwide consumption of ready-to-eat seafood products has steadily increased due to a range of health benefits. However, depending on the handling or cutting process of raw fish, ready-to-eat sashimi can be exposed to microbiological risks that can lead to foodborne infection by marine pathogens. Since surface characteristics are key factors for microbial adhesion and biofilm formation, the present study aims to determine the correlation between raw fish skin properties and Vibrio parahaemolyticus biofilm formation. We analyzed V. parahaemolyticus biofilms (ATCC 17802; initially inoculated ca. 2 or 4 log CFU/cm²) on fish skin (gizzard shad, pomfret, red snapper, and mackerel; fish species served as sashimi without peeling the skin) formed under simulated marine environments (incubating in artificial seawater with rocking motion at 30 °C, the maximum temperature of seasonal seawater) for 24 h. The characteristics of fish skin were determined using confocal laser scanning microscopy/scanning electron microscopy. V. parahaemolyticus showed higher biofilm counts on fish skins than on stainless steel, which was used as a control (P < 0.05). In particular, V. parahaemolyticus formed biofilms with significantly higher levels of bacterial populations on gizzard shad and pomfret (ca. 5 log CFU/cm²; P < 0.05), highlighting the relationship between the biofilm formation level and the characteristics of gizzard shad and pomfret skins. The surface roughness of fish skins, including the main roughness parameters (Ra, Rq, and Rz), influenced the attachment of V. parahaemolyticus (P < 0.05). Additionally, images of V. parahaemolyticus biofilms suggested that different topographical profiles of fish species (e.g., mucus, unique structural features, etc.) could cause V. parahaemolyticus to exhibit different biofilm phenotypes, such as sticking to or entangling on the fish skin surface. The major findings of this study provide various phenotypic adhesions of V. parahaemolyticus to fish skin in considerations of the potential hazard for the consumption of ready-to-eat sashimi served with its skin.

Rapid, specific and sensitive detection of Vibrio parahaemolyticus in seafood by accelerated strand exchange amplification

Vibrio parahaemolyticus infectious diseases caused by seafood contamination may be life-threatening to people with weak immunity. The detection of the Vibrio parahaemolyticus pathogen in aquatic foods is critical for reducing the outbreak of human Vibrio parahaemolyticus-associated diseases. In this study, a highly sensitive, specific, and time-saving real-time narrow thermal-cycling amplification detection method was developed based on accelerated strand exchange amplification (ASEA). It can detect cultured Vibrio parahaemolyticus at concentrations as low as 25 CFU mL^-1. In addition, for artificially spiked scallop meat, the detection limit was 1.8 × 10³ CFU g^-1 without pre-culture and 18 CFU g^-1 of initial inoculum after 3 h enrichment. The whole assay, starting from DNA extraction, can be completed within 20 min. The ASEA detection method established in this study is an effective tool for the rapid detection of Vibrio parahaemolyticus strains in a large number of seafood samples.

Risk Reduction Assessment of Vibrio parahaemolyticus on Shrimp by a Chinese Eating Habit

In China, a traditional perspective recommended that consuming seafood should be mixed or matched with vinegar, because people thought this traditional Chinese eating habit could reduce the risk of pathogenic microorganism infection, such as Vibrio parahaemolyticus induced diarrhea. However, this empirical viewpoint has not yet been evaluated scientifically. This study conducted a simplified quantitative microbiological risk assessment (QMRA) model, which was employed to estimate the risk reduction of V. parahaemolyticus on ready-to-eat (RTE) shrimp by consuming with vinegars (white vinegar, aromatic vinegar, or mature vinegar). Results showed the reduction of V. parahaemolyticus density on RTE shrimp after consuming with white vinegar, aromatic vinegar and mature vinegar was respectively 0.9953 log CFU/g (90% confidence interval 0.23 to 1.76), 0.7018 log CFU/g (90% confidence interval 0.3430 to 1.060) and 0.6538 log CFU/g (90% confidence interval 0.346 to 0.9620). The infection risk of V. parahaemolyticus per meal in this QMRA model was quantified by a mean of 0.1250 with the standard deviation of 0.2437. After consuming with white vinegar, aromatic vinegar, and mature vinegar, the mean infection risk of V. parahaemolyticus on shrimp decreased to 0.0478, 0.0652, and 0.0686. The QMRA scenarios indicated significant reductions in infection risk when eating RTE shrimp by the Chinese eating habit (consuming with vinegar). This good eating habit should be recommended to promote the spread of around the world.

Salmonella Behavior in Meat during Cool Storage: A Systematic Review and Meta-Analysis

The aim of the present study was to investigate Salmonella behavior in meat stored in cool conditions (between 0 °C and 7.5 °C), by employing a systematic review and meta-analysis. The data were obtained from research articles published in SciELO, PubMed, the Web of Science, and Scopus databases. The results of the retrieved studies were obtained from meat (beef, chicken, pork, poultry, and turkey), fish, shellfish, and broth media samples The data were extracted as sample size (n), initial concentration (Xi), final concentration (Xf), standard deviation (SD), standard error (SE), and microbial behavior effects (reduction or growth). A meta-analysis was carried out using the metaphor package from R software. A total of 654 articles were initially retrieved. After applying the exclusion criteria, 83 articles were selected for the systematic review, and 61 of these were used for the meta-analysis. Most studies were conducted at 0 °C to 4.4 °C storage temperatures under normal atmosphere package conditions. Salmonella Typhimurium, S. Enteritidis, and a cocktail (strain mixture) were inoculated at 5.0 and 6.0 log CFU mL−1. Articles both with and without the addition of antimicrobial compounds were found. Salmonella concentration decreases were observed in most studies, estimated for all study combinations as −0.8429 ± 0.0931 log CFU g−1 (95% CI; −1.0254, −0.6604) (p < 0.001), varying for each subgroup analysis. According to this survey, Salmonella concentration decreases are frequent during cool storage, although concentration increases and no bacterial inactivation were observed in some studies.

Quantitative Risk Assessment of Vibrio parahaemolyticus in Shellfish from Retail to Consumption in Coastal Cities of Eastern China

ABSTRACT

Vibrio parahaemolyticus is the main foodborne pathogen worldwide that causes acute gastroenteritis. A quantitative microbiological risk assessment (QMRA) was conducted to evaluate the health risk associated with V. parahaemolyticus in shellfish in the coastal cities in the eastern part of the People's Republic of China. The QMRA framework was established from shellfish at retail to cooking at home to consumption. The prevalence and level of V. parahaemolyticus in shellfish, cooking methods, storage temperature, time after purchase, shellfish consumption frequency, and consumption amount were analyzed in the exposure assessment. The results of the exposure assessment were introduced into the beta-Poisson dose-response model, and Monte Carlo analysis was used to calculate the risk of gastroenteritis from shellfish consumption. The probability of illness caused by V. parahaemolyticus from shellfish consumption per person per year (Pill,yr) was 3.49E-05. Seasonal differences were noted in the Pill/meal; the maximum was 4.81E-06 in summer and the minimum was 2.27E-07 in winter. The sensitivity analysis revealed that the level of V. parahaemolyticus in shellfish and the amount of shellfish consumed per meal were main factors contributing to illness. This QMRA provided valuable information such as the probability of illness associated with the consumption of shellfish and reference points for prevention strategies and control standards of V. parahaemolyticus in shellfish.

HIGHLIGHTS

Salmonella typhimurium strip based on the photothermal effect and catalytic color overlap of PB@Au nanocomposite

This work reports a sensitive and accurate multimode detection method to detect Salmonella typhimurium using inherent color, photothermal and catalytic properties of Prussian blue@gold nanoparticles (PB@Au). The inherent color of PB@Au can realize direct visual detection while the temperature increase (ΔT) of it can realize sensitive and quantitative photothermal detection. Moreover, catalytic coloration detection is applied to further amplify detection signal. The risk limit, prevention and control of Salmonella typhimurium can be more intuitively displayed through catalytic color overlap degree between PB@Au and catalytic product. The sensitivity of method is improved through photothermal and catalytic coloration detection (10¹ CFU·mL^-1) compared with direct visual detection (10² CFU·mL^-1). The multimode detection improves the accuracy of method, and exhibits good repeatability, acceptable selectivity and stability. This method is also successfully applied in real samples, displaying its good practical applicability.

Marination liquids enriched with probiotics and their inactivation effects against food-borne pathogens inoculated on meat

The aim of the study was to develop marination liquids (MLs) enriched with probiotics (Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus or their combination) to improve the safety and sensory quality of meat during marination. The total acidity, total phenolic content, antioxidant and antimicrobial activities of MLs were in the range of 0.70-0.92 g tartaric acid/100 mL, 331.00-513.80 mg GAE/L, 71.10%-93.37% and 6.50-10.00 mm, respectively. At the end of the marination, the numbers of Escherichia coli O157: H7, Listeria monocytogenes and Salmonella Typhimurium on meat samples (≅6 log CFU/g) were decreased in the range of 0.7-2.7, 2.1-3.3 and 0.8-2.0 log CFU/g, respectively, depending on the type of ML and the treatment time used. Additionally, meat sample marinated with MLs containing L. casei was the most preferred sample in terms of appearance, color, flavor and general acceptability. These results showed that the existing effects of koruk juice were increased by probiotics.

Effects of decontamination treatment combined with natural chemicals and/or ultra-high pressure on the quality and safety of ready-to-eat wine-pickled mud snails (Bullacta exarata)

Ready-to-eat wine-pickled mud snails (Bullacta exarata) typically host a large number of microorganisms and are frequently contaminated with pathogenic bacteria during processing, resulting in a higher risk for foodborne illness with consumption. In this study, the decontamination effects of different treatment methods, including the use of ultrasonic cleaning (USC), natural chemicals, and ultra-high pressure (UHP), on the quality and safety of pickled mud snails were investigated by assessing the total viable count (TVC), total volatile base nitrogen (TVB-N) content, thiobarbituric acid-reactive substance (TBARS), and pH value of the products after 12 months of storage at –20 °C. Treatment with 200 W USC for 5 min was the most effective approach for reducing TVC in raw mud snails, with a minimal change in food quality. Natural chemical treatment or UHP treatment significantly inhibited the increase in TVC, pH, and TBARS and TVB-N accumulation compared with the control group; however, their combined treatment had no synergistic effect. In contrast, the combined chemical treatment was more effective in inhibiting changes in the above indices in pickled mud snails than UHP treatment alone or combined chemicals+UHP treatment. In addition, the bacterial diversity of pickled mud snails before and after 12 months of storage at –20 °C was determined using Illumina MiSeq sequencing. Our results indicated that USC combined with natural chemicals can be utilized commercially to maintain the quality and safety of pickled mud snails during storage at –20 °C.

Bactericidal effect of marinades on meats against different pathogens: a review

Marinades are seasoned liquids used to improve tenderness, palatability, flavor, color and/or texture of different meats. In addition to contribute to the sensory characteristics, marinates can inactivate food microorganism as well. The purpose of this study was to assess the current state of knowledge regarding the effect of marinades on meats and important food pathogens. Using a systematic review of literature, different types of marinades were evaluated, identifying its ingredients, concentrations, temperature, marinating time and their effect on Salmonella, Escherichia coli, Listeria monocytogenes, Campylobacter and Vibrio. Findings demonstrated that the use of marinades on meats not only prevents the growth of pathogens but also inactivates food pathogens. Most marinades were able to reduce < 3 log CFU/g of pathogens, and Vibrio populations demonstrated the highest reductions (> 4 log CFU/g). The pH was the most pronounced parameter influencing the pathogens inactivation, however, ingredients and storage temperature also affected pathogen reduction in marinades.

High concentration of sodium chloride could induce the viable and culturable states of Escherichia coli O157:H7 and Salmonella enterica serovar Enteritidis

In the present study, Escherichia coli O157:H7 and Salmonella enterica serovar Enteritidis were transferred into Luria-Bertani medium without NaCl (LBWS) and adjusted to various pHs (4, 5, 6 and 7) with lactic acid containing 0·75, 5, 10 and 30% NaCl, and stored at 25°C until the bacterial populations reached below detectable levels on tryptic soy agar (TSA). Although E. coli O157:H7 and S. Enteritidis did not grow on TSA when incubated in LBWS with 30% NaCl for 35 and 7 days, more than 60 and 70% of the bacterial cells were shown to be viable via fluorescent staining with SYTO9 and propidium iodide (PI), respectively, suggesting that a number of cells could be induced into the viable but nonculturable (VBNC) state. These bacteria that were induced into a VBNC state were transferred to a newly prepared tryptic soy broth (TSB) and then incubated at 37°C for several days. After more than 7 days, E. coli O157:H7 and S. Enteritidis regained their culturability. We, therefore, suggest that E. coli O157:H7 and S. Enteritidis entered the VBNC state under the adverse condition of higher salt concentrations and were revived when these conditions were reversed.

Electrolyzed Oxidizing Water and Its Applications as Sanitation and Cleaning Agent

Electrolyzed oxidizing water (EOW) is one of the promising novel antimicrobial agents that have recently been proposed as the alternative to conventional decontamination methods such as heat and chemical sanitizers. Acidic EOW with pH ranging from 2 to 5 is regarded most applicable in the antimicrobial treatment of vegetables and meats. Neutral and alkaline electrolyzed water have also been explored in few studies for their applications in the food industry. Neutral electrolyzed water is proposed to solve the problems related to the storage and corrosion effect of acidic EOW. Recently, the research focus has been shifted toward the application of slightly acidic EOW as more effective with some supplemental physical and chemical treatment methods such as ultrasound and UV radiations. The different applications of electrolyzed water range from drinking water and wastewater to food, utensil, and hard surfaces. The recent studies also conclude that electrolyzed water is more effective in suspensions as compared with the food surfaces where longer retention times are required. The commercialization of EOW instruments is not adopted frequently in many countries due to the potential corrosion problems associated with acidic electrolyzed water. This review article summarizes the EOW types and possible mechanism of action as well as highlights the most recent research studies in the field of antimicrobial applications and cleaning. Electrolyzed water can replace conventional chemical decontamination methods in the industry and household. However, more research is needed to know its actual mechanism of antimicrobial action along with the primary concerns related to EOW in the processing of different food products.

The universal dual-mode aptasensor for simultaneous determination of different bacteria based on naked eyes and microfluidic-chip together with magnetic DNA encoded probes

It was critically important to develop some sensitive, convenient and on-site methods for simultaneous assay of different pathogenic bacteria in foods. In this work, a dual-mode aptasensor was established for fulfilling above aims combing colorimetry with microfluidic chip. This as-prepared dual-mode aptasensor not only realized rapid screening by naked eye on-site, but also the simultaneous quantification of multiple bacteria. Namely, the presence of pathogenic bacteria was firstly judged by naked eyes with Salmonella typhimurium (S.T) and Vibrio parahaemolyticus (V.P) as models. And then, S.T and V.P in positive samples were simultaneously quantified by microfluidic chip. In order to obtain the multiple signals, a series of magnetic DNA encoded-probes (MDEs) was fabricated containing rolling cycle amplified long DNA chain (RCA-DNA) rich in G-quadruplex sequences. They can combine with hemin as DNAzyme to catalyze 3,3'-5,5'-Tetramethyl benzidine (TMB)-H₂O₂ system for color development and be cleaved by EcoRV endonuclease to produce DNA fragments with different lengths. The microfluidic chip was employed to separate and quantify the fragments for quantifying S.T and V.P simultaneously. For this protocol, 100 CFU·mL^-1 of V.P or S.T could be observed by the naked eye and as low as 32 S.T and 30 CFU·mL^-1 V.P could be detected by the chip within 3 min. The dual-mode aptasensor could quickly screen positive samples, and simultaneously perform quantitative detection of the bacteria in positive samples. Our protocol demonstrated its potential in on-site qualification & simultaneous quantification of foodborne bacteria in foods.

Assessment of the effect of marination with organic fruit vinegars on safety and quality of beef

The aim of the present study was to determine the effects of organic fruit vinegars (blackberry, pomegranate, rosehip, and grape) used as marination liquids (MLs) on food-borne pathogens inoculated on beef, as well as on the quality characteristics (physical, chemical, microbiological and sensory properties) of beef during marination process at 4 °C for 24 h. In the first part of the study, meat samples separately inoculated with Salmonella Typhimurium, Listeria monocytogenes and Escherichia coli O157:H7 (≅6 log CFU/mL) were marinated in four different MLs and the count of S. Typhimurium, L. monocytogenes and E. coli O157:H7 on samples decreased in the range of 1.040-1.225, 1.420-1.913 and 1.232-1.435 log CFU/g, respectively. Marination with rosehip vinegar (MLR) was determined as the most effective treatment against all pathogens. In the second part of the study, proximate composition, color parameters, cooking yield, marinate absorption, pH, texture profile, aerobic plate count and sensory properties of marinated meat samples were determined. The moisture content of the samples marinated with grape vinegar (MLG) (73.50%) was found lower than of the samples marinated with other formulations (in the range of 75.95-76.65%) (P < 0.05). Marination by various MLs resulted in significant differences between the L*, a* and b* values of meat samples (P < 0.05). The hardness value of the samples was decreased by marination with MLR (P < 0.05) and was determined as 25.70 N. There were no significant differences between the meat samples marinated with the four different MLs in terms of cooking yield, marinate absorption and pH (P > 0.05). Aerobic plate count was reduced in the range of 0.589-0.950 log CFU/g for 24 h marination (P > 0.05). The highest sensory evaluation scores in terms of flavor were determined in meat samples marinated with MLG (P > 0.05). Therefore, different fruit vinegars used as MLs improved the safety and quality of meat at different levels.

Prevalence, antibiotic susceptibility and characterization of Vibrio parahaemolyticus isolates in China

Vibrio parahaemolyticus is a marine and estuarine bacterium that poses a major threat to human health worldwide. In this study, from 2017 to 2019, we evaluated 900 food samples collected from China in 2017, with the aim of determining the incidence and features of V. parahaemolyticus in ready-to-eat (RTE) foods, shrimp and fish in China. The contamination rates in these were 3.67, 19.33 and 10.67%, respectively, and the prevalence of V. parahaemolyticus was higher in summer than in winter. In addition, 101 V. parahaemolyticus strains were isolated. Our results suggested that most of the isolates were resistant to aminoglycosides based on the antimicrobial resistance patterns of these aquatic product isolates against 14 antimicrobial agents. Furthermore, most of the isolates were multidrug-resistant. Serotyping showed that the isolates of the O2 serotype comprised the maximum proportion. Enterobacterial repetitive intergenic consensus sequence (ERIC)-PCR results indicated that the isolates (n = 101) could be classified into 12 clusters. There were 82 STs suggesting genetic variation and relatedness among these isolates. Our findings demonstrated the presence of V. parahaemolyticus in foods from Chinese retail markets and show that this methodology can be used for microbiological risk assessment in China.

Food-Borne Vibrio parahaemolyticus in China: Prevalence, Antibiotic Susceptibility, and Genetic Characterization

Vibrio parahaemolyticus is a marine and estuarine bacterium that leads to damage of aquatic industry by foodborne outbreaks and possesses an enormous threat to food safety as well as human health worldwide. In the current study, we investigated 905 food samples (ready-to-eat foods, fish, and shrimp) from 15 provinces in China, and aimed to determine prevalence, biological characteristics and genetic diversity of presumptive V. parahaemolyticus isolates. Firstly, 14.17% of 240 fish samples, 15.34% of 365 shrimp samples and 3.67% of 300 RTE food samples were positive for potential V. parahaemolyticus. Secondly, 69 food samples (14.87%) collected in summer were positive for target isolates, while the rate of positive sample of 441 food samples in winter reached 7.26%. Thirdly, we purified 202 V. parahaemolyticus strains for further research. And antimicrobial susceptibility results of strains tested revealed that the highest resistance rate was observed for ampicillin (79.20%). At the same time, 148 (73.27%) of all isolates were classified and defined as multi-drug resistant foodborne bacteria. The results of PCR assay showed that the isolates being positive for the tdh, trh or both genes, were up to 9.90%, 19.80% or 3.96%. Besides, multiplex PCR test showed that the isolates carrying O2 serogroup were the most prevalent. Furthermore, sequence types (STs) of 108 isolates were obtained via multi-locus sequence typing. Not only 82 STs were detected, but also 41 of which were updated in the MLST database. Thus, our findings significantly demonstrated the high contamination rates of V. parahaemolyticus in fish and shrimp and it may possess potential threat for consumer health. We also provided up-to-date dissemination of antibiotic-resistant V. parahaemolyticus which is important to ensure the high efficacy in the treatment of human and aquatic products infections. Lastly, with the identification of 82 STs including 41 novel STs, this study significantly revealed the high genetic diversity among V. parahaemolyticus. All of our research improved our understanding on microbiological risk assessment in ready-to-eat foods, fish, and shrimp.

Occurrence and Identification of Pathogenic Vibrio Contaminants in Common Seafood Available in a Chinese Traditional Market in Qingdao, Shandong Province

The investigation of the causative agents for foodborne diseases and subsequent development of preventive steps to control the outbreak and related economic loss is the basic goal and priority of a rational food safety program. The entero-pathogenic Vibrio spp., which are Gram negative bacteria inhabiting estuarine ecosystems, are the major cause of foodborne illness associated with the consumption of raw or undercooked contaminated seafood or shellfish. To survey the Vibrio contamination in sea snails (Neptunea cumingi Crosse and Busycon canaliculatu), a total of 20 samples were collected from traditional market, at Qingdao city in Shandong province, China and analyzed for Vibrio species contamination. Presumptive-positive colonies grown on a specific Vibrio agar-based medium were picked and identified by the VITEK^TM. Vibrio alginolyticus, V. parahaemolyticus, and V. vulgaris were isolated and identified in 11, 8, and 2 seafood samples, respectively. Among the 8 isolates of V. parahaemolyticus. The V. parahaemolyticus isolates were further tested for the tdh, trh, and tlh virulence factors. All the V. parahaemolyticus isolates were tlh-positive, however, all of them were tdh-negative. Interestingly 2 V. parahaemolyticus isolates were positive for trh virulence factor. These results indicated that there is a high incidence of V. alginolyticus and V. parahaemolyticus in sea snails. Therefore, food safety regulations for fishery auction markets should be established to control these species in addition to other Vibrio pathogenic contaminants. Our study provides the first evidence for the prevalence of Vibrio spp. in sea snail samples from traditional market in the Qingdao province of China.

Characterization of Mixed-Species Biofilm Formed by Vibrio parahaemolyticus and Listeria monocytogenes

Mixed-species biofilms are the predominant form of biofilms found in nature. Research on biofilms have typically concentrated on single species biofilms and this study expands the horizon of biofilm research, where the characterization and dynamic changes of mono and mixed-species biofilms formed by the pathogens, Vibrio parahaemolyticus and Listeria monocytogenes were investigated. Compared to mono-species biofilm, the biomass, bio-volume, and thickness of mixed-species biofilms were significantly lower, which were confirmed using crystal violet staining, confocal laser scanning microscopy and scanning electron microscopy. Further experimental analysis showed these variations might result from the reduction of bacterial numbers, the down-regulation of biofilm-regulated genes and loss of metabolic activity in mixed-species biofilm. In addition, V. parahaemolyticus was located primarily on the surface layers of the mixed-species biofilms thus accruing competitive advantage. This competitive advantage was evidenced in a higher V. parahaemolyticus population density in the mixed-species biofilms. The adhesion to surfaces of the mixed-species biofilms were also reduced due to lower concentrations of extracellular polysaccharide and protein when the structure of the mixed-species was examined using Raman spectral analysis, phenol-sulfuric acid method and Lowry method. Furthermore, the minimum biofilm inhibitory concentration to antibiotics obviously decreased when V. parahaemolyticus co-exited with L. monocytogenes. This study firstly elucidated the interactive behavior in biofilm development of two foodborne pathogens, and future studies for biofilm control and antibiotic therapy should take into account interactions in mixed-species biofilms.

Underestimated Risks of Infantile Infectious Disease from the Caregiver's Typical Handling Practices of Infant Formula

The impact on infant caregiver as a reservoir of pathogens has not been exploited with perspective to powdered infant formula (PIF). Here we reveal novel route of pathogen transfer through hand-spoon-PIF unexpectedly occurred by even typical practices of caregivers, handling of PIF and storage of feeding-spoon in PIF container. Hand-spoon-PIF contamination route was simulated to analyze the transfer and subsequent survival of pathogens. Major pathogens associated with infantile fatal diseases (Cronobacter sakazakii, Salmonella enterica, Staphylococcus aureus) were readily transmitted to PIF from skin (3−6 log CFU/hand) via spoons following long-term survival of transferred pathogens (3 weeks; use-by date of PIF) as the excessive level of infectious dose, highlighting direct onset of diseases. Low bacterial load on skin (ca. 1 log CFU/hand) could prevent cross-contamination of PIF, however, at least 72 h survival of transferred pathogen on spoons demonstrated the probability on re-contamination of PIF. To our knowledge, this is the first study to investigate the cross-contamination of utensils in contact with powdered-foods. Bacterial load on hands is the key determinant of pathogen transfer and the extent of risk are species-dependent. These evidential results redefine risk of caregivers’ practices and facilitate incorporation of cross-contamination into risk-assessment as underestimated route of infection.

Prevalence, Antibiotic Susceptibility and Diversity of Vibrio parahaemolyticus Isolates in Seafood from South China

Vibrio parahaemolyticus is a leading cause of foodborne infections in China and a threat to human health worldwide. The main objective of this study is to determine the prevalence and characteristic of V. parahaemolyticus isolates in fish, oyster and shrimp samples from the South China domestic consumer market. To accomplish this, we examined 504 seafood samples from 11 provinces of China. The prevalence rates were 9.38, 30.36, and 25.60%, respectively. In summer (33.33%), the prevalence of V. parahaemolyticus was more common than that detected in the winter (14.01%). In addition, we identified 98 V. parahaemolyticus strains. The antimicrobial resistance trends of our seafood isolates to 15 antimicrobial agents revealed that major isolates were resistant to ampicillin (79.59%). Furthermore, 68.38% of the isolates were identified as being multidrug resistance. The prevalence of tdh or trh genes among the isolates was 8.16 and 12.24%, respectively. ERIC-PCR and multilocus sequence typing (MLST) results enabled classification of the isolates (n = 98) into different clusters, revealing genetic variation and relatedness among the isolates. Thus, our findings demonstrate the prevalence of V. parahaemolyticus in a variety of common seafood consumed domestically in China and provides insights into the dissemination of antibiotic-resistant strains, which should improve our microbiological risk assessment knowledge associated with V. parahaemolyticus in seafoods.

Drug resistance, AmpC-β-lactamase and extended-spectrum β-lactamase-producing Enterobacteriaceae isolated from fish and shrimp

The present study aims to detect the production of extended-spectrum beta-lactamases (ESBL) by enterobacteria isolated from samples of fresh shrimp and fish obtained from the retail trade of the city of Sobral, Ceará State, Brazil. All bacterial isolates were submitted to identification and antimicrobial susceptibility testing using aminopenicillin, beta-lactamase inhibitors, carbapenem, 1st, 2nd, 3rd and 4th generation cephalosporins, and monobactam. Three types of beta-lactamases - ESBL, AmpC and KPC - were investigated. 103 strains were identified, and the most frequent species in shrimp and fish samples was Enterobacter cloacae (n = 54). All the strains were resistant to penicillin and more than 50% of the isolates were resistant to ampicillin and cephalothin. Resistance to three 3rd generation cephalosporins (cefotaxime, ceftriaxone and ceftazidime) and one fourth generation cephalosporin (cefepime) was detected in two isolates of E. cloacae from shrimp samples. Phenotypic detection of AmpC was confirmed in seven strains. The ESBL was detected in two strains of E. cloacae from shrimp samples. No strain showed KPC production. These data can be considered alarming, since food (shrimp and fish) may be carriers of enterobacteria resistant to drugs of clinical interest.

Sodium Chloride Does Not Ensure Microbiological Safety of Foods: Cases and Solutions

Addition of salt or salt-containing water to food is one of the oldest and most effective preservation methods in history; indeed, salt-cured foods are generally recognized as microbiologically safe due to their high salinity. However, a number of microbiological risks remain. The microbiological hazards and risks associated with salt-cured foods must be addressed more in-depth as they are likely to be underestimated by previous studies. This review examined a number of scientific reports and articles about the microbiological safety of salt-cured foods, which included salted, brined, pickled, and/or marinated vegetables, meat, and seafood. The following subjects are covered in order: (1) clinical cases and outbreaks attributed to salt-cured foods; (2) the prevalence of foodborne pathogens in such foods; (3) the molecular, physiological, and virulent responses of the pathogens to the presence of NaCl in both laboratory media and food matrices; (4) the survival and fate of microorganisms in salt-cured foods (in the presence/absence of additional processes); and (5) the interaction between NaCl and other stressors in food processes (e.g., acidification, antimicrobials, drying, and heating). The review provides a comprehensive overview of potentially hazardous pathogens associated with salt-cured foods and suggests further research into effective intervention techniques that will reduce their levels in the food chain.