• Journal of Food Hygiene and Safety
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• v.35 no.2
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• pp.103-108
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• 2020

Recently, consumer demand for safe but minimally processed food has rapidly increased. For this reason, many food processing industries are applying hurdle technology to enhance food safety, extend shelf life, and make foods appear minimally processed. Meanwhile, studies have shown that a treatment (stress) meant to inactivate foodborne pathogens may trigger adaptation mechanisms and could even offer cross protection against subsequent treatments. Also, certain routine farm practices such as antibiotic and herbicide use could result in the development of antibiotic-resistant pathogens. Such bacteria may be tolerant to food processing-associated stress and be more likely to remain viable in processed foods. In this review, we discuss the correlation between food processing-associated stress and antibiotic resistance. We also discuss molecular mechanisms such as the use of sigma factors, SOS response pathways and efflux pumps as means of cross protection against antimicrobial compounds and other food processing-associated stresses.

• The Korean Journal of Food And Nutrition
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• v.25 no.1
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• pp.188-195
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• 2012

To produce rapidly the traditional Kanjang soy sauce-like product with rich flavors, lactic acid bacteria of Enterococcus spp. isolated from Chungkukjang was used as one of starter cultures. Among 119 Enterococcus spp., eight strains were selected by protease-secreting activities and identified as four E. faecium, three E. faecalis, and one E. gallinarium. The strains showed low resistances toward eight antibiotics and had no resistant genes to the vancomycin. Especially, E. faecium O24 was cultivated well on 5% NaCl medium that was selected for further study as the starter. E. faecium O24 grew well on the steamed soybean and the counts increased by ten times overnight, which produced mostly 80 mg% glutamic acid and aspartic acid as the seasoning amino acids on the product. Various organic acids including principal lactic acid were also produced. Flavors of maltol and guaiacol, typical soy-sauce flavor, were produced in the mixed cultures of Zygosaccharomyces rouxii and Candida versatilis. Therefore, E. faecium O24 could be a starter of soybean fermentation for soy sauce-like product with rich flavors rapidly.

• Food Science of Animal Resources
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• v.30 no.5
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• pp.804-810
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• 2010

This study was performed to select protease-producing Bacillus sp. as a potential probiotic starter for fermented meat products. In order to isolate protease-producing bacterium from meju, measured the diameter of the clear zone on agar plate (TSA, 1% (w/v) skim milk) and analyzed for intracellular protease activity, then 10 Bacillus-like strains were isolated. Three Bacillus-like strains (P19, P27, and P33) among 10 strains were able to tolerate in acidic condition (TSB, pH 2.5, 2 h incubation). These 3 strains were showed antimicrobial activity against food-borne pathogenic bacteria. These vegetative cells of 3 strains were showed a survival rate of 0.04% to 0.08% under the artificial gastric acidic condition (TSB, pH 2.5 with 1% (w/v) pepsin), but spore-forming cells were 56.29% to 84.77%. Vegetative cells of 3 strains were the least bile-resistant, while spore-forming cells of 3 strains showed higher survival rate more than 76% under artificial bile condition (TSB, 0.1% (w/v) oxgall bile). In these strains, P27 strain was finally selected as a good probiotic strain. P27 strain was tentatively identified as Bacillus amyloliquefaciens by API CHB kit and 16S rDNA sequence analysis. The results of this study suggest that B. amyloliquefaciens P27 can be used as a potential probiotic starter for fermented meat product.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.5
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• pp.751-756
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• 2002

A study was carried out to evaluate the incidences and causes of bovine mastitis in Tanzanian shorthorn zebu (Bos indicus) in the traditional sector and crossbred cows (Bos taurus${\times}$Bos indicus) in the dairy ranching sector, both found under the extensive range management system. Management practices were evaluated through a survey study using structured questionnaires. A total of 120 lactating cows (60 cows from each sector) were screened for the disease using the California Mastitis Test (CMT). Confirmatory tests used for infected cows included; the Direct Microscopic Somatic Cell Count (DMSCC), culture, bacteriological and biochemical laboratory assays. Survey results showed that management practices were generally very poor in both sectors with 84% of the surveyed herds being kept and milked under very unhygienic environmental conditions. The level of infection was higher in the crossbred cows (5% clinical and 38.3% sub-clinical mastitis) and lower in the zebu cows with only sub-clinical mastitis (23.3%). Crossbred cows had (p<0.05) higher somatic cell counts than zebu cows. The four highest-ranking bacterial isolates in order of importance were Staphylococcus aureus, Escherichia coli, Streptococcus agalactiae and Bacillus spp. It was concluded that bovine mastitis under the extensive management system in Tanzania was a result of poor management practices and that zebu cows were more resistant to the diseases than crossbred cows.

• Journal of Microbiology and Biotechnology
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• v.9 no.6
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• pp.778-783
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• 1999

Campylobacter is a pathogen for both humans and animals that can be transferred from animals to humans. Four isolates, which grew under 5-10% $CO_2$ and had small and translucent colonies, were obtained from swine gastric mucosa and characterized using various methods. These bacteria were gram negative, spirally shaped with round ends. One or two non-sheathed polar flagella were observed under electron microscopy. A PCR with species-specific protein (SSP) primers for 16S rRNA gene in Campylobacter produced a typical 462 bp fragment. The isolates had various biochemical and molecular characteristics which differentiated them from other Campylobacters. The isolates were catalase and oxidase positive, urease (rapid) negative, nitrate reduction positive, indoxyl acetate hydrolysis positive, y-glutamyl transpeptidase negative, and alkaline phosphatase negative. All four isolates showed growth at $37^{\circ}C{\;}and{\;}42^{\circ}C{\;}but{\;}not{\;}at{\;}25^{\circ}C$, were resistant to cephalotin and cefoperazone, and susceptible to carbenicillin. The isolates showed various results in the reduction of chloride to triphenyl tetrazolium (TTC) and a susceptibility to nalidixic acid. Western blot analysis of these isolates with antiserum raised against one isolate showed different patterns from those of reference strains. A dendrogram drawn with the RAPD results showed that these isolates belonged to a new Campylobacter spp. group different from those of C. jejuni, C. doylei, C. lari, and C. coli.

• Journal of Microbiology
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• v.43 no.2
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• pp.133-143
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• 2005

Shigellosis is a global human health problem. Four species of Shigella i.e. S. dysenteriae, S. flexneri, S. boydii and S. sonnei are able to cause the disease. These species are subdivided into serotypes on the basis of O-specific polysaccharide of the LPS. Shigella dysenteriae type 1 produces severe disease and may be associated with life-threatening complications. The symptoms of shigellosis include diarrhoea and/or dysentery with frequent mucoid bloody stools, abdominal cramps and tenesmus. Shigella spp. cause dysentery by invading the colonic mucosa. Shigella bacteria multiply within colonic epithelial cells, cause cell death and spread laterally to infect and kill adjacent epithelial cells, causing mucosal ulceration, inflammation and bleeding. Transmission usually occurs via contaminated food and water or through person-to-person contact. Laboratory diagnosis is made by culturing the stool samples using selective/differential agar media. Shigella spp. are highly fragile organism and considerable care must be exercised in collecting faecal specimens, transporting them to the laboratories and in using appropriate media for isolation. Antimicrobial agents are the mainstay of therapy of all cases of shigellosis. Due to the global emergence of drug resistance, the choice of antimicrobial agents for treating shigellosis is limited. Although single dose of norfloxacin and ciprofloxacin has been shown to be effective, they are currently less effective against S. dysenteriae type 1 infection. Newer quinolones, cephalosporin derivatives, and azithromycin are the drug of choice. However, fluoroquinolone-resistant S. dysenteriae type 1 infection have been reported. Currently, no vaccines against Shigella infection exist. Both live and subunit parenteral vaccine candidates are under development. Because immunity to Shigella is serotype-specific, the priority is to develop vaccine against S. dysenteriae type 1 and S. flexneri type 2a. Shigella species are important pathogens responsible for diarrhoeal diseases and dysentery occurring all over the world. The morbidity and mortality due to shigellosis are especially high among children in developing countries. A recent review of literature (KotIoff et al.,1999) concluded that, of the estimated 165 million cases of Shigella diarrhoea that occur annually, $99\%$ occur in developing countries, and in developing countries $69\%$ of episodes occur in children under five years of age. Moreover, of the ca.1.1 million deaths attributed to Shigella infections in developing countries, $60\%$ of deaths occur in the under-five age group. Travellers from developed to developing regions and soldiers serving under field conditions are also at an increased risk to develop shigellosis.

• Journal of Microbiology
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• v.43 no.2
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• pp.172-178
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• 2005

To determine the prevalence and genotypes of $\beta$-lactamases among clones of a metagenomic library from the cold-seep sediments of Edison seamount (10,000 years old), we performed pulse-field gel electrophoresis, antibiotic susceptibility testing, pI determination, and DNA sequencing analysis. Among the 8,823 clones of the library, thirty clones produced $\beta$-lactamases and had high levels of genetic diversity. Consistent with minimum inhibitory concentration patterns, we found that five ($167\%$) of thirty clones produced an extended-spectrum $\beta$-lactamase. 837- and 259-bp fragments specific to bla$_{TEM}$ genes were amplified, as determined by banding patterns of PCR amplification with designed primers. TEM­1 was the most prevalent $\beta$-lactamase and conferred resistance to ampicillin, piperacillin, and cephalothin. TEM-116 had a spectrum that was extended to ceftazidime, cefotaxime, and aztreonam. The resistance levels conferred by the pre-antibiotic era alleles of TEM-type $\beta$-lactamases were essentially the same as the resistance levels conferred by the TEM-type alleles which had been isolated from clinically resistant strains of bacteria of the antibiotic era. Our first report on TEM-type $\beta$-lactamases of the pre-antibiotic era indicates that TEM-type $\beta$-lactamases paint a picture in which most of the diversity of the enzymes may not be the result of recent evolution, but that of ancient evolution.

• Journal of Microbiology
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• v.34 no.4
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• pp.320-326
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• 1996

To analyze the effects of host versus plasmid on survival of 2, 4-degrading bacteria in environmental samples, strains Pseudomonas cepacia/pJP4, Alcaligenes JMP228/pJP4, P. cepacia/p712, and Alcaligenes JMP228/p712 were separately inoculated into samples of field soil, paddy soil, lake water, and river water, and then the changes of their populations were measured. The strains used contained a 2, 4-D degradative plasmid, either pJP4 conferring fast-growing property to the host or p712 conferring slow-growing property, and were resistant to antibiotics such that the inoculated strains could be enumerated against the indigenous microbial populations. In sterile environmental samples, these strains were stably maintained at the levels used for inoculation, except in sterile paddy soil where Alcaligenes JMP228 strains died drapidly. In natural soil samples for four strains declined steadily with time, but in naturla water samples their polulations fell rapidly at the early phase and then remained almost constant. When the environmentla samples were treated with 2, 4-D, P. cepacia/pJP4 and P. cepacia/p712 maintained significant numbers, while Alcaligenes JMP228/pJP4 and Alcaligenes JMP228/p712 declined significantly in most of the samples. The results indicated that the survivability of genetically modified microorganisms could vary depending on the environments and that their abundance in the environments under s2, 4-D selection was markedly influenced by the nature of the 2, 4-D degradative plasmid as well as type of the host strain.

• Journal of Microbiology and Biotechnology
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• v.25 no.1
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• pp.137-142
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• 2015

Trimethoprim-sulfamethoxazole (TMP-SMX) has been used for the treatment of urinary tract infections, but increasing resistance to TMP-SMX has been reported. In this study, we analyzed TMP-SMX resistance genes and their relatedness with integrons and insertion sequence common regions (ISCRs) in uropathogenic gram-negative bacilli. Consecutive nonduplicate TMP-SMX nonsusceptible clinical isolates of E. coli, K. pneumoniae, Acinetobacter spp., and P. aeruginosa were collected from urine. The minimal inhibitory concentration was determined by Etest. TMP-SMX resistance genes (sul and dfr), integrons, and ISCRs were analyzed by PCR and sequencing. A total of 45 E. coli (37.8%), 15 K. pneumoniae (18.5%), 12 Acinetobacter spp. (70.6%), and 9 Pseudomonas aeruginosa (30.0%) isolates were found to be resistant to TMP-SMX. Their MICs were all over 640. In E. coli and K. pneumoniae, sul1 and dfr genes were highly prevalent in relation with integron1. The sul3 gene was detected in E. coli. However, in P. aeruginosa and Acinetobacter spp., only sul1 was prevalent in relation with class 1 integron; however, dfr was not detected and sul2 was less prevalent than in Enterobacteriaceae. ISCR1 and/or ISCR2 were detected in E. coli, K. pneumoniae, and Acinetobacter spp. but the relatedness with TMP-SMX resistance genes was not prominent. ISCR14 was detected in six isolates of E. coli. In conclusion, resistance mechanisms for TMP-SMX were different between Enterobacteriaceae and glucose non-fermenting gram-negative bacilli. Class 1 integron was widely disseminated in uropathogenic gram-negative baciili, so the adoption of prudent use of antimicrobial agents and the establishment of a surveillance system are needed.

• Environmental Engineering Research
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• v.25 no.4
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• pp.614-621
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• 2020

Antibiotic pollution is one of the factors contributing to the spread of antibiotic-resistant bacteria in the environment. Advanced oxidation and irradiation processes have been introduced to eliminate antibiotics from water and wastewater. However, few studies have reported the toxic effects of residual antibiotics and their byproducts induced by a treatment system. In this study, we compared the efficacies of chemical (high-performance liquid chromatography (HPLC)) and biological (antimicrobial susceptibility test) assays for measuring the concentrations of residual antibiotics after gamma irradiation for degrading amoxicillin, cephradine, lincomycin, and tetracycline. The concentrations of residual antibiotics estimated using the two assay methods were almost identical, except cephradine. In the case of cephradine, inhibited bacterial growth was observed that was equivalent to twice the concentration measured by HPLC in the samples subjected to gamma irradiation. The observed inhibition of bacterial growth suggested the generation of potentially toxic intermediates following antibiotic degradation. These results indicate that biological and chemical assays should be used in concert for monitoring antibiotic contamination and the toxic derivatives of antibiotic degradation. The results demonstrate that these four antibiotics can be decomposed by 2.0 kGy gamma-irradiation without toxic effects of their byproducts.