Enteropathogenic Escherichia coli (EPEC) have developed survival strategies to evade host defense systems. The intracellular level of guanosine tetraphosphate (ppGpp) controlled by RelA and SpoT can mediate immune evasion of EPEC. However, the impact of ppGpp-defective EPEC infection on phagocytes remains unknown. In this study, we report that disrupting relA and spoT of EPEC E2348/69 strain promotes its phagocytosis in porcine macrophages. Our experimental analysis showed that both uptake and killing of an E2348/69 ΔrelAΔspoT mutant by macrophages were increased compared to those of wildtype strain. These results suggest that ppGpp plays an essential role in evading phagocytosis during EPEC pathogenesis.

We investigated the epidemiological characteristics of the antimicrobial resistant Enterococcus isolates from the four major rivers of Korea in 2012. A total 316 surface water samples were collected from three distinct sites (nearby livestock farms, tributaries, and major rivers) at two different seasons (dry season: n = 76, wet season: n = 240). A total 654 bacterial cells were isolated from samples and their genus distribution were determined. We found that Gram-negative bacteria including various genera were prevalent (n = 522, 79.8%), and Enterococcus was the most common genus of Gram-positive bacteria (n = 119, 18.2%). The isolation rate of Gram-negative bacteria was higher in wet season, whereas that of Enterococcus isolates was higher in dry season. The prevalence of Enterococcus isolates was also higher nearby livestock farms than on tributaries and main rivers. Since Enterococcus isolate is a key indicator for animal fecal contamination, the following experiments focused on this microorganism. As compared to a previous report in 2006, the resistance rates in E. faecium to erythromycin (40.0% to 69.9%) and chloramphenicol (0% to 16.4%) were increased, whereas those to penicillin (56.0% to 4.1%) and teicoplanin (36.0% to 0%) were decreased. We also found that antimicrobial-resistant (AMR) E. faecium isolates from rivers and livestock samples shared similar pulsed-filed gel electrophoresis (PFGE) profiles, validating the transmission of AMR Enterococcus isolates from livestock to river. Taken together, this study provides us with detailed information about bacterial contamination status in four major rivers, and highlights the changes in AMR pattern of Enterococcus isolates, which are expected to have originated from livestock.

Enteropathogenic Escherichia coli (EPEC) is one of the etiological agents that causes diarrhea in weaning pigs. In this study, we report that mutating both relA and spoT genes in EPEC E2348/69 can promote bacterial clearance in porcine gastrointestinal tract (GIT). Our experimental analyses showed that an E2348/69 ΔrelAΔspoT mutant strain was not detected in porcine feces after 1 day post-infection (dpi), whereas its parental strain was continuously detected in porcine feces within 10 dpi. Histologic assessment revealed that the mutant strain was unable to induce moderate pathologic lesions in porcine GIT when compared to those with the wildtype strain. Taken together, our data suggest that the relA and spoT genes in EPEC play an important role in bacterial survival and pathogenesis in porcine GIT.

Salmonella is one of the most important bacterial pathogens responsible for many zoonotic food-related infectious diseases. Quantitative detection of the foodborne Salmonella contamination in various food sources is therefore critical for preventing the related disease outbreaks. In this study, we developed and evaluated a reliable real-time polymerase chain reaction (RT-PCR) assay to detect the Salmonella contamination quantitatively. The experimental results showed that our invA gene-specific quantitative RT-PCR (qRT-PCR) assay provides a strong correlation between the Cq values and the direct plate counts of Salmonella species in the artificially formulated samples. Further study may be necessary to identify more accurate correlation and equation that can apply to Salmonella spp.

Both iron-deficient and zinc-sufficient diets have been known to be associated with a decreased risk of colon cancer. We investigated that effect of dietary zinc on the formation of colonic aberrant crypt foci (ACF) induced by azoxymethane (AOM) followed by dextran sodium sulfate in iron-deficient mice. Five-week old ICR mice were acclimated for 1 week and fed on iron-deficient diet (4.50 ppm iron) with three different zinc levels (0.01, 0.1, and 1.0 ppm) for 12 weeks. The total number of aberrant crypt (AC) and ACF was measured in the colonic mucosa after methylene blue staining. The total ACF numbers of low Zn (LZn), medium Zn (MZn) and high Zn (HZn) diet groups were 10.00 ± 2.67, 8.78 ± 3.12, and 7.96 ± 2.44, respectively and there were no significant differences among the groups. However, the total AC numbers of HZn (27.07 ± 3.88) and MZn (26.39 ± 5.59) diet groups were significantly low compared to LZn (22.57 ± 5.09) diet group (p<0.01). Cytosolic SOD activity was the highest in LZn diet group. But thiobarbituric acid-reactive substances level in liver was also the highest in LZn diet group compared to other groups. There is no difference in cell proliferation in mucous membrane among the groups, while apoptotic positive cells were increased in the HZn diet group. The high zinc diet exhibited decreased β-catenin-stained areas on the mucous membrane of colon compared to the LZn or MZn diet group. These findings indicate that dietary zinc might exert a modulating effect on development of ACF/AC in the mice with iron-deficient status.

A new oat (Avena sativa L.) cultivar 'Darkhorse' was developed by Honam Agricultural Research Institute (HARI) m2005. It was released because ofits earlmess, high forage yield potential and adaptability for late summer sowing. It was devel-oped from the a

A new oat (Avena sativa L.) cultivar, "Highspeed" was developed by Honam Agricultural Research Institute (HARI) in2005. It was released because of its earliness, high forage yield potential, and good adaptability for late summer sowing. "High-speed" was s

Mananbyeo was developed from a three way cross ilyang110/Yeongdeog7//Milyang110 in 1999. It has short growing duration about 71 days from seeding to heading and short culm length of 75 cm. It has almost similar number of panicles per hill , spikelets per