Antimicrobial susceptibility of pathogenic Escherichia coli isolated from pigs in Korea

The in vitro susceptibilities of 285 isolates of Escherichia coli from preweaned and postweaned pigs with diarrhea and edema disease were tested with the 15 commonly used antimicrobial drugs by an agar dilution minimal inhibitory concentration procedure according to National Committee for Clinical Laboratory Standards (NCCLS) guidelines. All E. coli isolates tested in this study belonged to enterotoxigenic E. coli, attaching and effacing E. coli, or Shiga toxin-producing E. coli. Field isolates had low MIC90 for ceftiofur (1 microg/ml). No correlation in antimicrobial resistance was found in three types of E. coli.     

Lectin histochemistry of Peyer's patches in the porcine ileum

Lectin staining pattern in Peyer's patches of porcine ileum was studied using twenty one biotinylated-labeled lectins as cell markers which were visualized with avidin-biotin-peroxidase complex method (ABC). WGA appears to be a selective marker for tingible body macrophages in the porcine germinal centers. ConA may be a positive marker for the lymphoid tissues, whereas 9 lectins (DBA, SBA, SJA, s-WGA, PNA, ECL, UEA-I, PHA-E, and PHA-L) may be negative markers for the lymphoid tissues in all areas.     

Enteritis associated with porcine circovirus 2 in pigs

This report describes the diagnosis of porcine circovirus 2 (PCV2)-associated enteritis in 6 weaned pigs without postweaning multisystemic wasting syndrome by histopathology, virus isolation, and in situ hybridization. The most unique lesions were granulomatous inflammation affecting Peyer's patches, characterized by infiltrates of epithelioid macrophages and giant multinucleated cells. Large, multiple, basophilic or amphophilic, grape-like intracytoplasmic inclusion bodies were often seen in the cytoplasm of histiocytic cells and giant multinucleated cells. No microscopic lesions were observed in the lymphoid tissue, such as lymph node, spleen, and tonsil. A strong hybridization signal for PCV2 was detected in the cytoplasm of histiocytes and giant multinucleated cells in Peyer's patches. Porcine circovirus 2 was isolated from homogenates of the small and large intestines in 2 weaned pigs. The presence of diarrhea and granulomatous enteritis, and abundant PCV2 DNA associated with the microscopic lesions is suggestive of PCV2-associated enteritis. Thus, PCV2-associated enteritis could be a distinct clinical manifestation of PCV2.     

Na2SO4胁迫对鞑靼滨藜氮同化作用的影响

在室外水培条件下，随Ｎａ２ＳＯ４胁迫浓度的升高及胁迫时间的延长，鞑靼滨藜叶生长速率，硝酸还原酶活性和全氮含量均呈下降趋势，游离氨基酸含量呈上升趋势。由实验结果可以看出，盐胁迫下硝酸还原活性的迅速下降是植物减少有害含氮化合物的积累和减少能量损耗的重要适应性反应。     

Effects of DDA, CpG-ODN, and plasmid-encoded chicken IFN-�� on protective immunity by a DNA vaccine against IBDV in chickens

This study examined the adjuvant effects of dimethyl dioctadecyl ammonium bromide (DDA), CpG oligodeoxynucleotides (CpG-ODN), and chicken interferon-γ (ChIFN-γ) on a DNA vaccine (pcDNA-VP243) against the infectious bursal disease virus (IBDV). A plasmid encoding chicken IFN-ã was constructed. Twice at 2-week intervals, two-week-old chickens were injected intramuscularly and intraperitoneally with either a DNA vaccine alone or a DNA vaccine together with the respective adjuvants. On week 2 after the second immunization, the chickens were orally challenged with the highly virulent IBDV. The groups that received the DNA vaccines plus either DDA or CpG-ODN showed significantly lower survival rates than the group that received the DNA vaccine alone. However, the survival rates for the DNA vaccine alone and for the DNA vaccine plus ChIFN-γ were similar. The chickens had no detectable antibodies to the IBDV before the challenge but all the surviving chickens in all groups except for the normal control group showed the induction of antibodies to the IBDV at day 10 after the challenge. As judged by the lymphocyte proliferation assays using the a WST-8 solution performed on the peripheral blood and splenic lymphocytes, the stimulation indices (SI) of the peripheral blood lymphocytes in all groups except for the normal control group were similar immediately before the challenge. At 10 days post-challenge, the SI for DNA vaccine plus either CpG-ODN or ChIFN-γ was similar to that of the DNA vaccine control group. For splenic lymphocytes, the SI in the DNA vaccine plus CpG-ODN and DNA vaccine plus ChIFN-γ groups were higher than for the DNA vaccine control. These results suggest that DDA actually compromises the protection against the IBDV by DNA vaccine, and CpG-ODN and IFN-γ had no significant effect.     

Determining the toxicity and hazard to fish of a rice insecticide

The experiments described were carried out to establish whether the effects of the insecticide, Ripcord (active ingredient cypermethrin), on fish, would limit its use in rice. Laboratory and field experiments were carried out, and the effects of cypermethrin were compared with those of a ‘standard insecticide’, carbofuran, widely used for pest control in rice, and a ‘positive control’, chlorfenvinphos, expected to be toxic to fish in rice paddies at insecticidally effective rates. Acute toxicity tests in the laboratory with the technical materials on the fish Tilapia nilotica showed cypermethrin, with a 96 h LC₅₀ value of 2 μg/l, to be some 20 times more toxic than chlorfenvinphos, with a 96 h LC₅₀ value of 39 μg/l, and some 250 times more toxic than carbofuran with a 96 h LC₅₀ of 480 μg/l. The LC₅₀ values obtained from laboratory tests with formulated products (cypermethrin EC, chlorfenvinphos granules and carbofuran granules) on T. nilotica and Cyprinus carpio were broadly in agreement with those obtained from the tests with the technical materials and confirmed C. carpio to have a similar susceptibility to that of T. nilotica. However, a field experiment carried out in paddy rice in Korea with commercial formulations and at commercial application rates showed that mortality of caged C. carpio was much less with cypermethrin (< 15%) than with chlorfenvinphos (97%) or carbofuran (67%). A second field experiment in Spain where cypermethrin was applied by air resulted in no mortality of caged C. carpio held in the paddy. It is concluded that the limited toxic effects of cypermethrin on fish in the field, when compared with those of chlorfenvinphos and carbofuran, make it acceptable for use in rice. The effects of cypermethrin were limited in comparison with those of chlorfenvinphos and carbofuran because only very low application rates of cypermethrin are needed to give pest control. The penetration of the liquid cypermethrin formulations into the water was also lower than that of the granular insecticides and, finally, cypermethrin was more rapidly lost from water. Together, these factors are sufficient to explain the minimal toxic effects of cypermethrin in the field when compared with chlorfenvinphos and carbofuran, despite its considerably higher acute toxicity determined in laboratory tests.     

Seroprevalence of porcine respiratory coronavirus in selected Korean pigs

A total of 446 serum samples from 88 herds in Korea were examined for antibody to porcine respiratory coronavirus (PRCV) using blocking enzyme-linked immunosorbent assay (ELISA). All serum samples were collected from 24- to 26-week-old finishing pigs between December 1998 and June 1999. By ELISA, 237 out of 446 sera tested (53.1%) and 54 out of 88 sampled herds (61.3%) were positive against PRCV. Of 446 sera from 88 herd tested, 185 (41.5%) serum samples from 22 (25%) herds were seronegative against PRCV and transmissible gastroenteritis virus infection. Our data suggested that seropositive herds for PRCV are distributed diffusely throughout South Korea.