• Food Science and Biotechnology
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• v.17 no.4
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• pp.761-765
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• 2008

Bacillus cereus causes two different types of food poisoning syndromes: diarrhea and emesis. The diarrheal syndrome is attributed to various enterotoxins, including nonhemolytic enterotoxin, hemolytic enterotoxin, and enterotoxin-T, whereas the emetic syndrome is caused by the dodecadepsipeptide toxin cereulide. A multiplex polymerase chain reaction (PCR) assay was developed to rapidly detect and identify B. cereus strains. Three primer pairs specific to regions within genes encoding nonhemolytic enterotoxin (nheA), molecular chaperonin (groEL), and cereulide synthetase (ces) were used to identify and differentiate between the enterotoxin-producing and emetic toxin-producing B. cereus strains. The cereulide-producing emetic B. cereus showed 3 PCR products of 325, 405, and 685 bp for the groEL, ces, and nheA genes, respectively, whereas the enterotoxin-producing B. cereus showed 2 PCR products without a ces gene specific DNA fragment. Specific amplifications and differentiations by multiplex PCR assay were obtained using 62 B. cereus strains and 13 strains' of other bacterial species. The detection limit of this assay for enterotoxin-producing strain and emetic toxin-producing strain from pure cultures were $2.4{\times}10^1$ and $6.0{\times}10^2\;CFU/tube$, respectively. These results suggest that our multiplex PCR method may be useful for the rapid detection and differentiation of B. cereus strains in foods.

• The Journal of the Korean Society for Microbiology
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• v.22 no.2
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• pp.139-145
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• 1987

Adherence to HEp-2 cells has been proposed as a virulence characteristic of enteropathogenic E. coli (EPEC). The role of the HEp-2 adherent E. coli was evaluated in a group of children with endemic diarrhea admitted to Hanyang University Hospital in Seoul, Korea. HEp-2-adherent E. coli was detected in fecal samples of 59 (59%) of 100 cases and ten (22.7%) of 44 concurrent control children (p<0.0005). Adherence was exhibited by 15 serogroups and subgroups, but within these groups more than one adherence pattern was frequently observed. Of 17 strains belonging to traditional infantile EPEC serogroups, 12(70.6%) gave a positive adherence. Of 45 enterotoxin producing strains, 24 (53.3%) gave a positive adherence. HEp-2-adherent strains that did not belong to classic EPEC serogroups and did not produce heat-stable and/or heat-labile enterotoxins(referred as enteroadherent E. coli, EAEC) was found in 29 (29%) of the patients with diarrhea and in six (13.6%) of the well children (p<0.05). From 22 of the 29 cases, no pathogen other than EAEC was isolated. These findings strongly implicate EAEC as the cause of diarrhea in the children. Our study supports the concept that EAEC may be an important cause of endemic diarrhea in Korean children.

• Animal Bioscience
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• v.34 no.4
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• pp.734-742
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• 2021

Objective: The present study aimed to investigate the occurrence and species of coagulase-positive staphylococci (CoPS) and coagulase-negative staphylococci (CoNS) in retail pork meat samples collected during nationwide monitoring. The staphylococcal isolates were characterized for antimicrobial and zinc chloride resistance and enterotoxigenic potential. Methods: A total of 260 pre-packaged pork meat samples were collected from 35 retail markets in 8 provinces in Korea for isolation of staphylococci. Antimicrobial and zinc chloride resistance phenotypes, and genes associated with the resistance phenotypes were determined on the isolates. Furthermore, the presence and distribution of 19 staphylococcal enterotoxin (SE) genes and enterotoxin-like genes among the pork-associated staphylococci were determined by multiplex polymerase chain reaction-based assays using the specific primer sets. Results: A total of 29 staphylococcal strains (29/260, 11.1%) were isolated from samples of retail pork meat, 24 (83%) of which were CoNS. The four CoNS species identified were S. saprophyticus (n = 16, 55%), S. sciuri (n = 3, 10%), S. warneri (n = 3, 10%), and S. epidermidis (n = 2, 7%). Among the 29 isolates, four methicillin-resistant CoNS (MR-CoNS; three S. sciuri and one S. epidermidis) and one methicillin-resistant CoPS (MR-CoPS; one S. aureus) were identified. In addition, a relatively high level of tetracycline (TET) resistance (52%) was confirmed in CoNS, along with a predominant distribution of tet(K). The most prevalent SEs were sep (45%), and sen (28%), which were carried by 81% of S. saprophyticus. Conclusion: These findings suggest that CoNS, especially S. saprophyticus strains, in raw pork meat could be a potential risk factor for staphylococcal food poisoning (SFP), and therefore, requires further investigation to elucidate the role of SEls in SFP and virulence of the pathogen. Our results also suggest that CoNS from raw pork meat may act as a source for transmission of antimicrobial resistance genes such as staphylococcal cassette chromosome mec and tet(K).

• Journal of Veterinary Science
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• v.23 no.1
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• pp.7.1-7.14
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• 2022

Background: Enterotoxigenic Escherichia coli (ETEC) infection is a primary cause of livestock diarrhea. Therefore, effective vaccines are needed to reduce the incidence of ETEC infection. Objectives: Our study aimed to develop a multivalent ETEC vaccine targeting major virulence factors of ETEC, including enterotoxins and fimbriae. Methods: SLS (STa-LTB-STb) recombinant enterotoxin and fimbriae proteins (F4, F5, F6, F18, and F41) were prepared to develop a multivalent vaccine. A total of 65 mice were immunized subcutaneously by vaccines and phosphate-buffered saline (PBS). The levels of specific immunoglobulin G (IgG) and pro-inflammatory cytokines were determined at 0, 7, 14 and 21 days post-vaccination (dpv). A challenge test with a lethal dose of ETEC was performed, and the survival rate of the mice in each group was recorded. Feces and intestine washes were collected to measure the concentrations of secretory immunoglobulin A (sIgA). Results: Anti-SLS and anti-fimbriae-specific IgG in serums of antigen-vaccinated mice were significantly higher than those of the control group. Immunization with the SLS enterotoxin and multivalent vaccine increased interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) concentrations. Compared to diarrheal symptoms and 100% death of mice in the control group, mice inoculated with the multivalent vaccine showed an 80% survival rate without any symptom of diarrhea, while SLS and fimbriae vaccinated groups showed 60 and 70% survival rates, respectively. Conclusions: Both SLS and fimbriae proteins can serve as vaccine antigens, and the combination of these two antigens can elicit stronger immune responses. The results suggest that the multivalent vaccine can be successfully used for preventing ETEC in important livestock.

• Journal of Veterinary Science
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• v.24 no.6
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• pp.85.1-85.13
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• 2023

Background: A recent increase in the occurrence of canine skin and soft tissue infections, including otitis externa and pyoderma, caused by antimicrobial-resistant Staphylococcus pseudintermedius and S. schleiferi has become a significant public and veterinary health issues. Objective: We investigated the virulence potentials associated with the occurrence of canine otitis externa in S. pseudintermedius and S. schleiferi. Methods: In this study, the prevalence of genes encoding leukocidins, exfoliative toxins, and staphylococcal enterotoxins (SEs) was investigated using previously characterized S. pseudintermedius (n = 26) and S. schleiferi (n = 19) isolates derived from canine otitis externa. Susceptibility to cathelicidins (K9CATH and PMAP-36) and hydrogen peroxide (H₂O₂) was also examined in both staphylococcal species. Results: A high prevalence of genes encoding leukocidins (lukS/F-I, lukS1/F1-S, and lukS2/F2-S), exfoliative toxins (siet, expB, and sset), and SEs was identified in both S. pseudintermedius and S. schleiferi isolates. Notably, S. pseudintermedius isolates possessed higher number of SE genes, especially newer SE genes, than S. schleiferi isolates harboring egc clusters. Although no significant differences in susceptibility to K9CATH and H₂O₂ were observed between the two isolate groups, S. pseudintermedius isolates exhibited enhanced resistance to PMAP-36 compared to S. schleiferi isolates. Conclusions: These findings suggest that high a prevalence of various toxin genes together with enhanced resistance to cathelicidins may contribute to the pathogenicity of S. pseudintermedius and S. schleiferi in canine cutaneous infections.

• Journal of Food Hygiene and Safety
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• v.26 no.4
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• pp.366-369
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• 2011

In this study, the contamination levels of total aerobic bacteria, E. coli, total coliform and S. aureus of seasoned dried fishes (SDF) in Korea were investigated. A total of 81 SDF samples were purchased randomly from 28 stores. Contamination range of total aerobic bacteria, total coliform and S. aureus were 150~1,700,000, 10~31,000 and 10~220 CFU/g, respectively. E. coli was detected in only one samples in the qualitative test. We have analyzed quantitatively Staphylococcal enterotoxins (SE-type A, C and D) produced by S. aureus contaminated in SDF using a TECRA kit and standard curve. The curve equation was Y = 0.1499 * X + 0.1183 and maximum amount of SEs in SDF was 0.71 ng/ml. Reduction speed of S. aureus in SDF stored at $37^{\circ}C$ was the highest among the samples stored for 8 days at different temperature of 7, 18 and $37^{\circ}C$. On the basis of the results, SDF in Korea can be contaminated by a variety of pathogenic bacteria. Therefore, precautionary measures are necessary for consumer protection, including the improvement of sanitary conditions in the processing plants in Korea.

• Korean Journal of Food Science and Technology
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• v.46 no.3
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• pp.334-340
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• 2014

Toxin-producing Bacillus cereus is the causative agent of two different types of food poisoning: the emetic and the diarrheal types. This study was conducted to investigate the presence of enterotoxin and emetic toxin genes in 263 B. cereus isolated from 619 different ready-to-eat food items. Hemolytic enterotoxins hblA, hblC, and hblD were detected in 85.6, 41.1, and 76.8%, respectively, of the B. cereus isolates. About 67.0% (175/263) of the isolates presented all of three genes. Non-hemolytic enterotoxins nheA, nheB, and nheC were detected in 100, 97.0, and 68.4% of the isolates, respectively. Approximately 90.0% (236/263) of the isolates presented all of these three non-hemolytic enterotoxin genes. Emetic toxin gene, CER, was detected in 132 of 263 (50.2%) isolates. Computer-assisted cluster analysis of Rep-PCR profiles showed a high genetic diversity among the isolates. All B. cereus isolates from food samples tested in this study carried at least 6 of 10 toxin genes.

• Korean Journal of Food Science and Technology
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• v.53 no.6
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• pp.799-808
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• 2021

This study was performed to investigate the extent of microbial contamination, the presence of enterotoxin genes, and the antibiotic susceptibility of Bacillus cereus in 58 red pepper plants and 43 environmental samples (soil, irrigation water, and gloves) associated with the plant cultivation. The detected counts of total aerobic bacteria, coliform bacteria, Escherichia coli, Bacillus cereus, and Staphylococcus aureus were lower in these samples, as compared to the regulations of standards for foods; moreover, pathogens, such as E. coli, E. coli O157:H7, Listeria monocytogenes, and Salmonella spp., were not detected. Genes encoding hemolysin BL enterotoxins (hblA, hblC, and hblD) as well as non-hemolytic enterotoxins (nheA, nheB, and nheC) were detected in 23 B. cereus specimens that were isolated from the test samples and had β-hemolytic activity. Interestingly, B. cereus is resistant to β-lactam and susceptible to non-β-lactam antibiotics. However, in this case, the isolated B. cereus specimens exhibited a shift from resistant to intermediate in response to cefotaxime and from susceptible to intermediate in case of rifampin, trimethoprim-sulfamethoxazole, vancomycin, clindamycin, and erythromycin. Therefore, the levels of B. cereus should be monitored to detect changes in antibiotic susceptibility and guarantee their safety.

• Journal of Food Hygiene and Safety
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• v.34 no.6
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• pp.576-582
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• 2019

Staphylococcus pseudintermedius is an opportunistic pathogen in dogs and is recognized as a zoonotic pathogen causing public health concern. Although canine-associated S. pseudintermedius has mainly been recognized for its antimicrobial resistance and ability to cause skin infections in dogs, information on antimicrobial resistance profiles and enterotoxigenicity of S. pseudintermedius in livestock is very limited. In this study, we investigated the prevalence of 18 different staphylococcal enterotoxin (SE) genes and toxic shock syndrome toxin gene (tst-1) in S. pseudintermedius strains isolated from dogs, pigs, and beef cattle. Moreover, antimicrobial resistance profiles of the strains were determined along with the presence of mecA and SCCmec types. Except for one bovine isolate, all S. pseudintermedius isolates from dogs and pigs were resistant to multiple drugs (≥ 4 different drugs). Four out of six canine isolates were methicillin resistant and carried SCCmec type V. In addition, 11 different SE genes (seb, sec, see, seg, sei, sej, sel, seo, sep, seq, and seu) and tst-1 were identified in S. pseudintermedius isolates from dogs, pigs, and beef cattle. Most S. pseudintermedius isolates (83%) harbored multiple SE genes, and sel (42%) and sep (42%) were most frequently detected in the isolates. Our results suggested that S. pseudintermedius isolates from livestock and companion animals may serve as a reservoir for SE genes and antimicrobial resistance.

• Tuberculosis and Respiratory Diseases
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• v.79 no.4
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• pp.295-301
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• 2016

Background: Specific immunoglobulin E (IgE) sensitization to staphylococcal enterotoxin (SE) has been recently considered to be related to allergic disease, including asthma. Despite studies on specific IgE (sIgE) to SE and its relationship to asthma diagnosis and severity, the association of sIgE to SE with airway hyperresponsiveness (AHR) remains unclear. Methods: We enrolled 81 asthma patients admitted to the Severance Hospital in Korea from March 1, 2013, to February 28, 2015 and retrospectively reviewed the electronic medical records of the enrolled subjects. The serum levels of sIgE to SE (A/B) of all subjects was measured using the ImmunoCAP 250 (Phadia) system with SE-sIgE positive defined as >0.10 kU/mL. Results: The SE-sIgE level was not significantly correlated with asthma severity (forced expiratory volume in 1 second [$FEV_1$], $FEV_1$/forced vital capacity, sputum eosinophils, and serum eosinophils), whereas the SE-sIgE level in patients with positive AHR ($mean{\pm}standard$ error of the mean, $0.606{\pm}0.273kU/mL$) was significantly higher than that in patients with negative AHR ($0.062{\pm}0.015kU/mL$, p=0.034). In regression analysis, SE sensitization (sIgE to SE ${\geq}0.010kU/mL$) was a significant risk factor for AHR, after adjustment for age, sex, $FEV_1$, and sputum eosinophils (odds ratio, 7.090; 95% confidence interval, 1.180-42.600; p=0.032). Prevalence of SE sensitization was higher in patients with allergic rhinitis and non-atopic asthma patients, as compared to patients without allergic rhinitis and atopic asthma patients, respectively, but without statistical significance. Conclusion: SE sensitization is significantly associated with AHR.