Prevalence and classification of toxigenic Staphylococcus aureus isolated from refrigerated ready-to-eat foods (sushi, kimbab and California rolls) in Korea

Prevalence of Foodborne Bacterial Pathogens and Antibiotic Resistance Genes in Sweets from Local Markets in Iran

BACKGROUND

This study aimed to investigate the prevalences of some important antibiotic-resistance genes (ARGs) and foodborne bacterial pathogens in sweet samples collected from local markets in Iran.

METHODS

Forty sweet samples were collected. Foodborne pathogens and ARGs were detected in the sweet samples by conventional and multiplex PCR assays using species-specific primers.

RESULTS

Staphylococcus aureus, Cronobacter sakazakii, Shigella spp., Campylobacter jejuni, and Campylobacter coli were detected and identified in 47.5%, 20%, 45%, 5%, and 30% of the sweet samples, respectively. We found S. aureus and Shigella spp. were the most prevalent bacterial pathogens. S. aureus was found to be the most frequent pathogenic bacteria profiled in these samples. We also found a significant correlation between the presence of C. coli and Cr. sakazakii. We detected the blaSHV resistance gene in 97.5% of the sweet samples; however, blaTEM was detected in only one sample (2.5%).

CONCLUSIONS

Regarding these results, we suggest preventive strategies such as implementing automation of food processing; monitoring the personal hygiene and health of food handlers, and testing regularly for antibiotic resistance in raw materials and products.

Microbiological Food Safety of Seaweeds

The use of seaweeds in the human diet has a long history in Asia and has now been increasing also in the western world. Concurrent with this trend, there is a corresponding increase in cultivation and harvesting for commercial production. Edible seaweed is a heterogenous product category including species within the green, red, and brown macroalgae. Moreover, the species are utilized on their own or in combinatorial food products, eaten fresh or processed by a variety of technologies. The present review summarizes available literature with respect to microbiological food safety and quality of seaweed food products, including processing and other factors controlling these parameters, and emerging trends to improve on the safety, utilization, quality, and storability of seaweeds. The over- or misuse of antimicrobials and the concurrent development of antimicrobial resistance (AMR) in bacteria is a current worldwide health concern. The role of seaweeds in the development of AMR and the spread of antimicrobial resistance genes is an underexplored field of research and is discussed in that context. Legislation and guidelines relevant to edible seaweed are also discussed.

Enterotoxigenicity and genetic relatedness of Staphylococcus aureus in a commercial poultry plant and poultry farm

Raw (fresh) and frozen poultry products are frequently associated with Staphylococcus aureus contamination. New Zealand is among the developed countries with high incidences of staphylococcal food poisoning. The study investigated the S. aureus isolates obtained from various stages of poultry production, to determine the primary source of contamination. Viable cell counts of S. aureus were enumerated using Petrifilm™ Staph Express Count Plates, and the isolates were confirmed by Gram-stain and coagulase-positive test. Sixty S. aureus isolates were further confirmed by PCR. The PCR analysis used primers that specifically amplifies a fragment of the femA gene, unique to S. aureus. The confirmed S. aureus strains were further examined for enterotoxigenicity by PCR. Multilocus Sequence Typing (MLST) was then used to identify sequence types (STs) of the sixty isolates of S. aureus. The relatedness of the sequence types was investigated by eBURST. In this study, it was observed that all samples from the processing plant and live chickens at the farm were contaminated by S. aureus. Fifty-nine (59) of the 60 isolates were enterotoxigenic carrying enterotoxin genes: seg, sei, seh, sek, sel, sem, sen, or seo. The sixty isolates were categorised into six different sequence types: ST5, ST2594, ST101, ST83, ST398, ST1; where ST5, ST83 and ST2594 belonged to the Clonal Complex (CC) 5 with ST5 being the clonal ancestor. The sources of S. aureus contamination in the final poultry products were linked to fresh mechanically separated meat, fresh skin, fresh skin-on-breast fillet, rubber fingers on mechanical pluckers, and live chickens at the farm. The skin of live chickens at the farm was most likely the origin of S. aureus contamination on equipment and final products. Not all identified S. aureus strains at the farm were observed in the final products. Therefore, further investigation on other potential contamination sources such as gloves and knives used at the processing plant, and feeders and drinkers at the farm level is recommended.

Pathogenicity and seasonal variation of Aeromonas hydrophila isolated from seafood and ready-to-eat sushi in South Korea

Aeromonas hydrophila is an emerging foodborne pathogen capable of causing human gastroenteritis, and the main reservoir is the aquatic environment. In this study, the prevalence and virulence of A. hydrophila in seafoods and ready-to-eat (RTE) sushi distributed in various conditions (refrigerated, dried, or frozen) or seasons was investigated. Strains were isolated from seafood (refrigerated or frozen oysters, sashimi, and processed fish; n = 333) and RTE sushi (n = 88) samples collected in South Korea and then genetically analyzed for gastroenteritis-related virulence genes (aer, ast, and alt). Raw oysters showed the highest prevalence of A. hydrophila (57.1%; 47/91) among all seafoods. Among the sashimi samples, flatfish sashimi (54.8%; 34/62) and salmon sushi (51.4%; 18/35) were the most prevalent. A. hydrophila was not detected in the oysters or anchovies distributed as either frozen or dried products. Seasonal investigations of sashimi and sushi showed that the summer prevalence of A. hydrophila with putative virulence genes was significantly lower in sashimi but highest in sushi. These results indicated that sushi could have been contaminated from several sources during the manufacturing or distribution processes. Significant correlations among the prevalence of putative virulence genes were confirmed, although no combination of genes presented a Phi correlation coefficient above 0.5 (0.26-0.43). To our knowledge, this is the first study to investigate the prevalence of A. hydrophila in various types of retail seafoods and RTE sushi in the East Asia region and then relate the prevalence to the distribution conditions of the samples. This study provides background information on the level of potential risk posed by A. hydrophila in retail seafoods and RTE sushi.

Geographic Pattern of Sushi Product Misdescription in Italy-A Crosstalk between Citizen Science and DNA Barcoding

The food safety of sushi and the health of consumers are currently of high concern for food safety agencies across the world due to the globally widespread consumption of these products. The microbiological and toxicological risks derived from the consumption of raw fish and seafood have been highlighted worldwide, while the practice of species substitution in sushi products has attracted the interest of researchers more than food safety agencies. In this study, samples of sushi were processed for species authentication using the Cytochrome Oxidase I (COI) gene as a DNA barcode. The approach of Citizen Science was used to obtain the sushi samples by involving people from eighteen different Italian cities (Northern, Central and Southern Italy). The results indicate that a considerable rate of species substitution exists with a percentage of misdescription ranging from 31.8% in Northern Italy to 40% in Central Italy. The species most affected by replacement was Thunnus thynnus followed by the flying fish roe substituted by eggs of Mallotus villosus. These results indicate that a standardization of fish market names should be realized at the international level and that the indication of the scientific names of species should be mandatory for all products of the seafood supply chain.

Characterisation of Classical Enterotoxins, Virulence Activity, and Antibiotic Susceptibility of Staphylococcus Aureus Isolated from Thai Fermented Pork Sausages, Clinical Samples, and Healthy Carriers in Northeastern Thailand

Introduction

Contamination by Staphylococcus aureus of food produced from animal sources may have diverse and multifactorial causes that depend on geographical distribution. The goal of this study was to isolate and characterise S. aureus strains from contaminated fermented pork sausage, which is a local food of northeastern Thailand.

Material and Methods

S. aureus strains were isolated from local pork sausage, and the presence of classical enterotoxins was determined by PCR and reversed passive latex agglutination. These results were compared with strains derived from hospitalised patients and healthy carriers. Additionally, production of extracellular enzymes and haemolysin, biofilm formation, and antibiotic susceptibility were assessed.

Results

S. aureus was identified in 36 sausage isolates (60%). The strains positive for staphylococcal enterotoxin A were more frequently found in isolates from sausage and healthy carriers than in those from patients. All tested S. aureus strains were positive for DNase, lipase, proteinase, haemolysin, and biofilm formation; notably, strains isolated from food and healthy carriers displayed similar values. Most isolates were resistant to penicillin and ampicillin, while none were to methicillin.

Conclusions

Thai fermented pork sausages are associated with a high risk of staphylococcal food poisoning, which may be linked to contamination caused by carriers. Dissemination of knowledge regarding best practices in sanitation and hygiene is important in local communities.

Health Functionality and Quality Control of Laver (Porphyra, Pyropia): Current Issues and Future Perspectives as an Edible Seaweed

The growing interest in laver as a food product and as a source of substances beneficial to health has led to global consumer demand for laver produced in a limited area of northeastern Asia. Here we review research into the benefits of laver consumption and discuss future perspectives on the improvement of laver product quality. Variation in nutritional/functional values among product types (raw and processed (dried, roasted, or seasoned) laver) makes product-specific nutritional analysis a prerequisite for accurate prediction of health benefits. The effects of drying, roasting, and seasoning on the contents of both beneficial and harmful substances highlight the importance of managing laver processing conditions. Most research into health benefits has focused on substances present at high concentrations in laver (porphyran, Vitamin B12, taurine), with assessment of the expected effects of laver consumption. Mitigation of chemical/microbiological risks and the adoption of novel technologies to exploit under-reported biochemical characteristics of lavers are suggested as key strategies for the further improvement of laver product quality. Comprehensive analysis of the literature regarding laver as a food product and as a source of biomedical compounds highlights the possibilities and challenges for application of laver products.

The Prevalence, Antibiotic Resistance and Biofilm Formation of Staphylococcus aureus in Bulk Ready-To-Eat Foods

The prevalence of Staphylococcus aureus in 2160 bulk ready-to-eat foods from the Sichuan province of China during 2013-2016 was investigated. The antibiotic resistance and the associated genes, as well as biofilm formation capacity of the S. aureus isolates were measured. Furthermore, the relationship between the antibiotic resistance and the resistant genes was discussed. It was found that 54 S. aureus isolates were recovered, and their prevalence in meat products, dairy, fruit and vegetables, and desserts were 31 (2.6%), six (3.0%), nine (2.2%) and eight (2.3%), respectively. Most strains (52/54) were resistant to at least one of the antibiotics, and 21 isolates were identified as multidrug-resistant (MDR) S. aureus. Three isolates were found to be methicillin-resistant S. aureus. Penicillin, erythromycin, clindamycin, tetracycline and inducible clindamycin resistance were determined as the predominant antibiotics, and the isolates with the phenotypic resistance on these five antibiotics were all determined positive for the resistant gene associated. In total, 33 of 54 S. aureus isolates showed biofilm formation capacity, including two strong biofilm producers, one moderate and 30 weak ones. Two S. aureus isolates with strong biofilm formation abilities showed multi-drug resistance, and one moderate biofilm producer was resistant to two categories of antibiotics.

Prevalence, toxigenic potential and antimicrobial susceptibility profile of Staphylococcus isolated from ready-to-eat meats

Aim

An epidemiological surveillance for Staphylococci contamination of ready-to-eat (RTE) meats from Enugu State, Nigeria, was carried out to determine the prevalence, species distribution, toxigenic potential and antimicrobial susceptibility profile of the organisms and hence the microbiological and toxicological safety of the meats.

Materials and Methods

Isolation and phenotypic Staphylococcus detection were done according to standard microbiological methods. Phenotypic resistance to 17 commonly used antimicrobial agents was determined by disc diffusion method. Molecular characterization of the isolates to species level and detection of selected toxigenic and antimicrobial-resistance genes were done by PCR methods.

Results

Twenty-four (9.4%) of the 255 meat samples investigated were contaminated with Staphylococcus species. Twenty-four Staphylococcus isolates belonging to six species of coagulase-negative Staphylococcus (CoNS) were identified. Four (16.7%) isolates harbored genes coding for exfoliative toxin-A. Ten (41.7%) isolates were multidrug resistant, while mecA, tetK, mphC, ermT and ermC were the antimicrobial-resistance genes detected in the isolates. Meat samples sourced from motor parks (16.7%) and open markets (8.5%) were the most contaminated.

Conclusion

9.4% of RTE meats sampled were contaminated with toxigenic and multidrug resistance CoNS. Beef was the most contaminated RTE meat type and harbored all the toxigenic and most of the antibiotic-resistant genes detected. Meat samples from motor parks had the highest staphylococcal contamination (16.7%), while those from mechanic village had the least (2.4%). Majority (79.2%) of the isolates were not susceptible to fusidic acid but none exhibited antimicrobial-resistance to chloramphenicol, ciprofloxacin, linezolid or teicoplanin. Food safety authorities in the study area should work proactively to massively improve the hygienic practices of meat vendors; in order to limit staphylococcal contamination of RTE meats and the associated public health problems.

Microbial diversities and potential hazards of Korean turbid rice wines (makgeolli): Multivariate analyses

A number of makgeolli (Korean traditional turbid rice wine) products are commercially available in various forms. To date, there has been no comprehensive investigation of these products. Here, we collected samples of almost all of the makgeolli products that are currently commercially available (n = 167), recorded their manufacturing variables, and examined physiochemical parameters and microbial communities, using quantitative and qualitative methods. The aerobic plate count (APC) and counts of lactic acid bacteria (LAB), acetic acid bacteria (AAB), fungi, total coliforms, and Bacillus cereus were obtained, and the presence of Escherichia coli and eight foodborne pathogens was also examined. The data obtained were segmented and analyzed based on multiple variables associated with the manufacturing characteristics. Despite high ethanol contents (up to 16.0%) and high acidities (pH 3.3-4.5), the rice wine products examined here had diverse and abundant microbiotas (mean values: APC, 5.3; LAB,4.4; AAB,1.5; fungi, 3.8 log CFU/ml). In particular, LAB and fungi, which are used as co-starter cultures during rice wine manufacturing, accounted for the majority of the microbiotas. Bivariate analyses revealed significant positive correlations between the individual micro-organism counts (Pearson correlation coefficient = 0.668-0.947). Among the manufacturing variables considered in this study, only the pasteurization status had a significant effect on the microbial communities of rice wine products (p < 0.05). When examining the presence of foodborne pathogens, B. cereus was isolated from some of the rice wine products (58.1%) at low levels (<100 CFU/ml), and its detection rate was not significantly lower in the pasteurized products than the raw products. Overall, the results presented here provide a comprehensive overview of the microbiotas of commercially available turbid rice wines and their relationships to manufacturing variables. These data will help to direct future studies focusing on rice wine quality and safety control measures.

Characterization of Staphylococcus aureus Isolated from Food Products in Western Algeria

The current study aimed to characterize Staphylococcus aureus isolates from foodstuffs collected from western Algeria. A total of 153 S. aureus isolates from various raw and processed foods were obtained and identified using matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. Isolates were characterized by antimicrobial susceptibility testing and toxin gene detection. Methicillin-resistant Staphylococcus aureus (MRSA) isolates were identified by detection of the mecA gene and characterized by staphylococcal cassette chromosome mec (SCCmec) typing. We found that 30.9% (153/495) of food samples were contaminated with S. aureus. Thirty-three (21.5%) S. aureus isolates were identified as MRSA, and 16.9% (26/153) carried the mecA gene. Three SCCmec types were identified of which type IV was the most common (69.2%) followed by type V (15.3%) and type II (7.6%). Two MRSA isolates were not typable with SCCmec typing. None of the examined isolates harbored mecC. Furthermore, 14.3% (22/153) of the isolates were toxigenic S. aureus. The cytotoxin gene pvl was detected in 11.1% of the S. aureus isolates. This gene was more commonly detected (76.4%) in MRSA isolates than in methicillin-suceptible Staphylococcus aureus (MSSA) isolates. The tsst-1 gene coding for toxic shock syndrome toxin was isolated rarely (3.2%) and only in MSSA isolates. According to disk diffusion test results, 70 isolates were resistant to only one antimicrobial drug, and 51 (33.3%) isolates were multidrug resistant. Other 32 isolates were susceptible to all antibiotics. Our study highlights, for the first time, a high prevalence of multidrug-resistant S. aureus isolates carrying pvl or tsst-1 found in food products in Algeria. The risk of MRSA transmission through the food chain cannot be disregarded, particularly in uncooked foods.

Enterotoxin Gene Profile and Molecular Characterization of Staphylococcus aureus Isolates from Bovine Bulk Milk and Milk Products of Tigray Region, Northern Ethiopia

Staphylococcal food poisoning (SFP) is an important foodborne disease worldwide, and milk and milk products are commonly associated with SFP outbreaks. The objectives of this study were to investigate the distribution of staphylococcal enterotoxin (se) genes in Staphylococcus aureus from raw cow's milk and milk products and to assess their genetic background with the spa typing method. Of the 549 samples (297 bulk milk and 162 milk product samples) collected from Tigray region, Northern Ethiopia, 160 (29.1%) were positive for S. aureus, of which 82 (51%) were found to harbor se genes by a modified multiplex PCR. Nine se genes were identified: sea (n = 12), seb (n = 3), sec (n = 3), sed(n = 4), seg (n = 49), seh (n = 2), sei (n = 40), sej (n = 1), and tsst-1 (n = 24). The classical type of genes accounted for 27%. Of the 82 enterotoxigenic isolates, 41.5 and 12.4% harbored two or more se genes, respectively. The highest gene association was observed between sei and seg, whereas sea and seb were always found together with the new types of se genes. Altogether, 18 genotypes of toxin genes were identified, and 33% of the samples contained > 5 log CFU ml(-1) S. aureus. spa typing identified 22 spa types and three novel spa sequences, which showed the high genetic diversity of the isolates. No apparent relationship was observed between spa type and se genes. Of the 25 spa types, 13 (52%) were from raw milk, 3 (12%) from milk products, and 9 (36%) from both types of sample. Types t314 (20.7%,n = 17), t458 (18.3%, n = 15), and t6218 (9.8%, n= 8) were the most common spa types identified and were widely distributed in three of the eight studied localities. This is the first study from the Tigray region to report the high distribution of enterotoxigenic S. aureus with a diversified genetic background from dairy food. The study may provide valuable data for microbial food safety risk assessment, molecular epidemiology, and phylogenetic studies of S. aureus in Ethiopia.

Virulence Factors and Antibiotic Susceptibility of Staphylococcus aureus Isolates in Ready-to-Eat Foods: Detection of S. aureus Contamination and a High Prevalence of Virulence Genes

Staphylococcus aureus is one of the leading causes of food poisoning. Its pathogenicity results from the possession of virulence genes that produce different toxins which result in self-limiting to severe illness often requiring hospitalization. In this study of 200 sushi and sashimi samples, S. aureus contamination was confirmed in 26% of the food samples. The S. aureus isolates were further characterized for virulence genes and antibiotic susceptibility. A high incidence of virulence genes was identified in 96.2% of the isolates and 20 different virulence gene profiles were confirmed. DNA amplification showed that 30.8% (16/52) of the S. aureus carried at least one SE gene which causes staphylococcal food poisoning. The most common enterotoxin gene was seg (11.5%) and the egc cluster was detected in 5.8% of the isolates. A combination of hla and hld was the most prevalent coexistence virulence genes and accounted for 59.6% of all isolates. Antibiotic resistance studies showed tetracycline resistance to be the most common at 28.8% while multi-drug resistance was found to be low at 3.8%. In conclusion, the high rate of S. aureus in the sampled sushi and sashimi indicates the need for food safety guidelines.

Assessment of Enterotoxin Production and Cross-Contamination of Staphylococcus aureus between Food Processing Materials and Ready-To-Eat Cooked Fish Paste

This study evaluated Staphylococcus aureus growth and subsequent staphylococcal enterotoxin A production in tryptone soy broth and on ready-to-eat cooked fish paste at 12 to 37 °C, as well as cross-contamination between stainless steel, polyethylene, and latex glove at room temperature. A model was developed using Barany and Roberts's growth model, which satisfactorily described the suitable growth of S. aureus with R(2)-adj from 0.94 to 0.99. Except at 12 °C, S. aureus cells in TSB presented a lag time lower (14.64 to 1.65 h), grew faster (0.08 to 0.31 log CFU/h) and produced SEA at lower cell density levels (5.65 to 6.44 log CFU/mL) compare to those inoculated on cooked fish paste with data of 16.920 to 1.985 h, 0.02 to 0.23 log CFU/h, and 6.19 to 7.11 log CFU/g, respectively. Staphylococcal enterotoxin type A (SEA) visual immunoassay test showed that primary SEA detection varied considerably among different storage temperature degrees and media. For example, it occurred only during exponential phase at 30 and 37 °C in TSB, but in cooked fish paste it took place at late exponential phase of S. aureus growth at 20 and 25 °C. The SEA detection test was negative on presence of S. aureus on cooked fish paste stored at 12 and 15 °C, although cell density reached level of 6.12 log CFU/g at 15 °C. Cross-contamination expressed as transfer rate of S. aureus from polyethylene surface to cooked fish paste surface was slower than that observed with steel surface to cooked fish paste under same conditions. These results provide helpful information for controlling S. aureus growth, SEA production and cross-contamination during processing of cooked fish paste.

Prevalence of Staphylococcus aureus in Imported Fish and Correlations between Antibiotic Resistance and Enterotoxigenicity

A total of 156 Staphylococcus aureus isolates were obtained from 330 imported fresh fish samples from three countries. Selective media were used for the isolation of S. aureus, and the isolates were confirmed by PCR. The isolates were tested for mecA gene, antibiotic resistance, and enterotoxin genes (sea, seb, sec, sed, see, seg, seh, and sei). Most isolates carried sea, seg, and sei genes, and seg-sei was the most frequent enterotoxin profile. About 88.5% of the S. aureus exhibited resistance to at least one antibiotic. High resistance to penicillin and ampicillin; low resistance to tetracycline, erythromycin, rifampin, and clindamycin; and very low resistance to cefotaxime, amoxicillin-clavulanic acid, gentamicin, and ciprofloxacin were exhibited by S. aureus from the three countries. In addition, some antibiotic resistance exhibited a strong correlation (P ≤ 0.01) with enterotoxigenicity in S. aureus. The study concluded that the large amount of globally traded fish increases the possibility of intercontinental transmission of enterotoxigenic and multidrug-resistant S. aureus through fish and highlights the potential influence of local fish handling and processing on consumer health worldwide. The introduction of periodic training in food safety and hygiene is essential to increase fish handlers' awareness of good hygienic practices in handling fish. These findings also enrich the ongoing debate about the risk of methicillin- and multidrug-resistant S. aureus as a foodborne pathogen compared with drug-susceptible S. aureus.

Microbiological quality of seasoned roasted laver and potential hazard control in a real processing line

Microbiological quality of laver, one of the edible seaweeds, has not been reported in a real processing line. Laver or supplements were collected from six manufacturers (A to F) to assess potential microbiological hazards and the critical control points in commercial processing lines. Aerobic plate counts (APC), coliform counts, Bacillus cereus, Staphylococcus aureus, and Vibrio parahaemolyticus were enumerated, and the presence of B. cereus, Listeria monocytogenes, Salmonella, S. aureus, and V. parahaemolyticus were confirmed during processing. The raw material, i.e., dried laver, had a high initial APC level (4.4 to 7.8 log CFU/g), which decreased gradually during processing (final products, 1.3 to 5.9 log CFU/g). Coliforms and B. cereus were not detected in any of the final products, but they were present in some raw materials and semiprocessed products in quantitative analysis. After enrichment for recovery of stress-injured cells, E. coli and foodborne pathogens were not detected in any samples, with the exception of B. cereus. Heat-injured and spore-forming B. cereus isolates were occasionally obtained from some of the raw materials and products after enrichment, thus B. cereus may be a potential microbiological hazard that should be controlled using strategic intervention measures. Secondary roasting (260 to 400°C, 2 to 10 s) significantly reduced the APC (maximum log reduction, 4.7 log CFU/g), and this could be a key intervention step for controlling microbiological hazards during processing (critical control point). When this step was performed appropriately, according to the processing guide for each plant, the microorganisms were inactivated more successfully in the products. This study provides scientific evidence that may facilitate the development of strategies for microbiological hazard control and hygienic management guidelines for real manufacturing plants.

Prevalence, antimicrobial susceptibility, and enterotoxin gene detection of Staphylococcus aureus isolates in ready-to-eat foods in Shaanxi, People's Republic of China

Various ready-to-eat (RTE) foods are becoming increasingly popular in the world and could be easily contaminated with various microorganisms including certain pathogens. A total of 342 RTE food samples, including 32 cooked meats, 123 vegetable salads, 26 boiled peanuts, 109 cold noodles, and 52 dried tofu samples, were collected in Shaanxi Province, People's Republic of China, during the period of July to October 2012 and screened for Staphylococcus aureus. All S. aureus isolates were characterized by antimicrobial susceptibility and PCR for detecting nine enterotoxin genes (sea to sej). Overall, 25.4% of samples were positive for S. aureus, including 10 (31.3%) cooked meats, 34 (27.6%) salad vegetables, 6 (23.1%) boiled peanuts, 20 (18.3%) cold noodles, and 17 (32.7%) dried tofu samples. Of the isolated S. aureus organisms, 98.4% were resistant to at least one antimicrobial agent and 58.6% to three or more antimicrobials. Resistance to erythromycin (78.1%) and tetracycline (40.6%) was most frequently detected, while all isolates were sensitive to vancomycin and amikacin. Moreover, 55.5% of isolates were positive for one or more enterotoxin genes. The genes sed (25.8%) and sea (19.5%) were commonly detected among the isolates; seg, sei, and sej were not found. Our findings indicate that RTE foods in Shaanxi were contaminated with S. aureus isolates that harbored multiple toxin genes and exhibited multiple-drug resistance. Appropriated hygienic measures should be taken by producers, retailers, and consumers to reduce the risk posed by S. aureus in RTE foods.

Microbiological quality and risk factors related to sandwiches served in bakeries, cafés, and sandwich bars in South Korea

The objective of this study was to investigate the microbiological quality of sandwiches produced on site and served in bakeries, cafés, and sandwich bars in South Korea and to determine the major risk factors affecting the sanitation level in each store (n = 1,120). The microbiological quality of the sandwiches was analyzed, and the sanitation level of each store was evaluated as satisfactory or unsatisfactory based on sanitation guidelines. Total coliforms were detected in 906 samples (80.9%), but only 3 samples (0.3%) contained confirmed Escherichia coli contamination. The detection rate was highest for Bacillus cereus (10.0%), followed by Staphylococcus aureus (1.3%) and Salmonella (0.2%). Vibrio parahaemolyticus was not detected in any samples. The microbial contamination level was significantly lower in winter (P < 0.05) and in stores with a higher sanitation grade. Factors related to the microbiological quality of sandwiches were evaluated as the relative risk (RR) of coliform contamination, and the higher risk factors for sandwich contamination were improper holding temperature (RR = 8.75), cross-contamination (RR = 6.30), lack of proper ventilation systems (RR = 6.16), and the absence of clean and/or suitable outer garments (RR = 5.73). Most factors were related to the failure of food handlers to adhere to sanitation guidelines rather than to unsanitary environments. This study provides a comprehensive analysis of the relationship between the microbiological quality of sandwiches served on-site and various risk factors. These results will help researchers establish guidelines for the sanitary management of sandwich shops.