Na-Jung Choi

Emetic toxin producing Bacillus cereus Korean isolates contain genes encoding diarrheal-related enterotoxins.

Bacillus cereus can cause the diarrheal and emetic type of food poisoning but the symptoms of emetic food poisoning caused by B. cereus occasionally include emesis and diarrhea. The enterotoxin characteristics of emetic toxin (cereulide) producing B. cereus were needed to be determined. Therefore, forty B. cereus strains isolated from various sources in Korea were investigated for the presence of enterotoxin genes. All strains were confirmed to produce the emetic toxin using HPLC-MS methods. The rates of the nheABC, hblCDA, entFM and cytK genes amongst emetic toxin producing B. cereus strains were 82.5, 7.5, 50.0 and 27.5%, respectively. Pattern III harbored nheABC and entFM genes and pattern V processed entFM gene and were shown to be the major patterns, being present in 55.0% (21 of 40) of the emetic toxin producing B. cereus strains. Our findings revealed that 34 (85.0%) of 40 emetic toxin producing B. cereus strains isolated in Korea have the potential to cause diarrheal and emetic type of food poisoning, simultaneously. Thus, emetic toxin and enterotoxin genes should be constantly screened to provide insight into B. cereus food poisoning.

Comparison of enterotoxin production and phenotypic characteristics between emetic and enterotoxic Bacillus cereus.

Bacillus cereus was divided into emetic toxin (cereulide)- and enterotoxin-producing strains, but emetic toxin-producing B. cereus is difficult to detect immunochemically. Screening methods for emetic toxin-producing B. cereus are needed. The objectives of this study were to identify and detect emetic toxin-producing B. cereus among 160 B. cereus strains, and to compare enterotoxin production and phenotypic characteristics between the emetic toxin-producing and enterotoxin-producing strains. Forty emetic toxin-producing B. cereus strains were determined with high-pressure liquid chromatography-mass spectrometry analysis. Among the emetic toxin-producing strains (n = 40), 31 (77.5%) and 3 (7.5%) strains produced nonhemolytic enterotoxin (NHE) and hemolysin BL (HBL) enterotoxins, respectively. In addition, 107 (89.2%) and 100 (83.3%) strains produced NHE and HBL enterotoxins among the enterotoxin-producing strains (n = 120). The number of strains positive for starch hydrolysis, salicin fermentation, and hemolysis among the emetic toxin-producing strains were 3 (7.5%), 3 (7.5%), and 26 (65.0%), respectively, and among enterotoxin-producing strains, these numbers were 101 (84.2%), 100 (83.3%), and 111 (92.5%), respectively. In particular, the three emetic toxin-producing B. cereus strains (JNHE 6, JNHE 36, and KNIH 28) produced the HBL and NHE enterotoxins and were capable of starch hydrolysis and salicin fermentation. The absence of HBL enterotoxin and certain phenotypic properties, such as starch hydrolysis and salicin fermentation, indicates that these properties were not critical characteristics of the emetic toxin-producing B. cereus tested in this study.

Bacteriological quality of vegetables from organic and conventional production in different areas of Korea.

Foods grown in organic production systems have been described as representing an increased risk to public health compared with foods from conventional production. Leafy vegetables (spinach, romaine lettuce, and green sesame leaves) grown in organic and conventional systems were collected from various areas in Korea and examined using standard culture methods to compare the microbiological quality of the produce grown in the two agricultural systems. The 354 samples of these leafy vegetables were analyzed for levels of indicator bacteria (aerobic bacteria, coliforms, and Escherichia coli) and the prevalence of the pathogens Staphylococcus aureus, E. coli O157:H7, Listeria monocytogenes, Bacillus cereus, and Salmonella. Aerobic bacteria and coliforms were detected in all vegetable types, but nonpathogenic E. coli was below the limit of detection in all samples. B. cereus was the most prevalent pathogen, found on 7 (11.1%) of the 63 organic spinach samples. The prevalence of S. aureus was highest in organic sesame leaves; it was found on 5 (8.0%) of the 63 samples. The prevalence of L. monocytogenes was highest on organic romaine lettuce and spinach; it was found in 4 (6.4%) of 63 samples of each type of vegetable. E. coli O157:H7 found on only 1 (1.58%) of 55 conventional spinach samples. These results suggest that farming type at most only slightly affects the hygienic quality of leafy vegetables, and no effect was found for sample collection area. Salmonella was not isolated from any of the conventional or organic leafy vegetables. These results do not support the hypothesis that organic produce poses a substantially greater risk of pathogen contamination than does conventional produce.

Analysis of Microbiological Contamination Levels of Cabbage and Fresh-cut Produce on Difference Area toward Climate in Korea

ABSTRACT - The purpose of this study was to evaluate microbiological contamination of fresh-cut produce sal-ads and raw cabbage toward climate change. Total aerobic bacteria, coliform and Escherichia coli were monitored toget the contamination levels and E. coli O157:H7, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenesand Salmonella spp. to detect pathogens with risk of foodborne disease from samples. Collection of 360 samples (180fresh-cut produce salads and 180 raw cabbage), including 60 samples from each area after setting 3 areas dependingon annual temperature and annual rainfall. As a result, total aerobic bacteria and coliform group were different wasperformed areas in raw cabbage but there was no difference between areas in fresh-cut produce salads. In additionfoodborne pathogens including E. coli were not isolated from fresh-cut produce salads.Key words: Fresh-cut produce, Foodborne pathogens, Contamination levels, Climate 최근 전 세계적으로 민감한 문제 중 하나인 기후변화는기후 온난화, 대기 오염 증가로 인하여 생태계는 물론, 경제, 산업, 문화의 전반적인 부분에 걸쳐 다양한 파급효과가발생하고 있는 실정이며 식품 안전을 포함한 사회 전반의문제가 되고 있다. 이에 세계적 규모의 기후변화는 이제 현실화되어 심각한 문제를 야기하고 있으며, 기후변화에 따른 문제점이 특정 국가 차원에서 국제적으로 확대되고 있다