It has been known that the ability of Shiga toxinproducing Escherichia coli (STEC) to produce Stx2e in culture media plays a role in the diagnosis of edema disease and determination of subunit vaccine candidates in STEC isolates. To examine the efficiency of Stx2e production in several commercial media, a Stx2e-producing strain (KEFS1302) was grown in four different media: ISO-Sensitest broth (ISB), E. coli broth (ECB), trypticase soy broth (TSB), and Mueller Hinton broth (MHB), with or without mitomycin C at 37°C (250 rpm) for 6 h. Toxin production was measured by enzyme-linked immunosorbent assay. In the presence of mitomycin C, ECB was found to be the most suitable medium, reaching a production peak (OD600 = 1.2) at 1 h; Stx2e was mostly produced during the logarithmic phase (within 3 h). On the other hand, toxin production in ISB reached a peak at 3 h after incubation in the absence of mitomycin C. Stx2e was purified by fast protein liquid chromatography (FPLC) using anion-exchange chromatography. The 43 kDa band of Stx2e was confirmed by western blot using the ECB supernatant. Our results showed that ECB and ISB media would be a suitable medium for mass production of Stx2e even if the toxin production is dependent on time.

The emergence of antimicrobial resistant Escherichia (E.) coli is a major problem in pig farms. To tackle this issue, in July 2011, the Korean government banned the use of antimicrobials for growth promotion of animals in farms. Moreover, E. coli encoding the Stx2e gene cause edema disease which results in high mortality and morbidity in pig farms. Therefore, the aim of this study was to investigate the prevalence of antimicrobial resistance among E. coli encoding the Stx2e gene isolated from weaned piglets with diarrhea before and after the ban on antibiotic growth promoters (AGPs) in Korea from 2007 to 2016. In this period, 479 E. coli isolates were obtained from weaned piglets with diarrhea, and of them, 144 E. coli isolates encoding the Stx2e gene were detected by polymerase chain reaction. The susceptibility of the E. coli isolates to antibiotics were tested using the standard Kirby-Bauer disk diffusion method. The most frequently observed resistances in isolates obtained from weaned piglets in the last 10 years were to tetracycline (92.4%) and chloramphenicol (88.9%). The prevalence of resistance to colistin (3.1% to 16.5%) and tetracycline (86.2% to 97.5%) was also observed to have increased over this period. Additionally, multi-drug resistance was also found to have increased (87.7% to 97.5%) after the ban on AGPs. These findings provide useful data for designing prevention and treatment strategies for postweaning diarrhea and edema disease, and can be used in future studies on antimicrobial resistance in Korea.

The seroprevalence of major infectious abortion agents was investigated in native Korean goats from Jeonnam province using ELISA. A total of 98 blood samples were collected from goats. Overall, 48 (49.0%), 11 (11.2%), and 1 (1.0%) serum samples tested positive for C. burnetii, T. gondii, and C. abortus, respectively, while none of the samples were positive for B. abortus or N. caninum. Moreover, a PCR assay conducted to detect C. burnetii antigens in goats with a history of abortion revealed 18 (38.3%) of 47 goats were C. burnetii positive by both the ELISA and PCR assay.

A 26-month-old male mixed-breed dog of Korean origin was subjected to necropsy following death after a history of decreased appetite and weight loss. Necropsy revealed generalized lymphadenopathy and splenomegaly. Histopathological examination of samples from the spleen, mandibular lymph nodes, liver, kidney, and large intestine showed granulomas with numerous macrophages containing intracytoplasmic Leishmania amastigotes. Transmission electron microscopy revealed Leishmania amastigotes in the macrophage cytoplasm. All tissues with granulomas were positive for Leishmania spp, which was confirmed to be Leishmania infantum by conventional polymerase chain reaction (PCR), real-time PCR, and in situ hybridization. To our knowledge, this is the second case of canine visceral leishmaniasis in Korea.

Bovine brucellosis causes abortion and infertility. The authors conducted this study in order to determine pathological lesions of Korean native cows and fetuses who received experimental vaccination with Brucella abortus RB51 and were challenged with Brucella abortus 2308. Gross and histopathological lesions in endometrium and placenta were observed in cows of the vaccinated group. Twenty-five percent of pregnant cattle in the vaccinated group showed endometritis and placentitis, which was three times lower, compared with the non-vaccinated group. The pathological lesions in the uterus and placenta in both groups were consistent with previous reports. Therefore, vaccination in heifers using Brucella abortus RB51 may not provide adequate protection against infection with Brucella abortus virulent strain.

The present study was conducted to investigate serotype distribution and biofilm formation of Actinobacillus (A.) pleuropneumoniae isolated from pneumonic lungs of pigs. A total of 37 A. pleuropneumoniae were isolated between January 2009 and June 2010. Serotypes of A. pleuropneumoniae isolates were determined using two different PCRs. The majority of isolates belonged to serotype 5 (n=31, 83.8%), and the others belonged to serotype 1 (n=4, 10.8%), and 2 (n=2, 5.4%), respectively. The ability of biofilm formation of the isolates was also determined by quantitative microtiter plate assay. Biofilm formation was observed in both 23 (62.2%) of the 37 field isolates and seven (43.8%) of the 16 reference strains. On the other hand, biofilm formation was various according to the serotypes: 20 (64.5%) of serotype 5, and three (75.0%) of serotype 1. However, two isolates of serotype 2 did not produce the biofilm in this study. Consequently, A. pleuropneumoniae serotype 5 was the most frequently detected (83.8% of the isolates), and 23 (62.2%) of 37 isolates exhibited biofilm positive phenotype in this study.

Toxocara (T.) canis, round worm of dogs and cats, is probably the most common gastrointestinal helminthes of domestic canid and is ascarid nematodes in the order Ascaridida, family Toxocaridae. The prevalence of patent toxocariasis is highest in the young dogs and much less common in adult dogs. There are few reports on the status of T. canis prevalence of dogs in Korea. Few cases of human visceral larva migrans also reported in Korea. However, as far as we know, there is no report on the canine toxocariasis case determined by pathological findings in Korea until now. In this research, we diagnosed canine toxocariasis by fecal egg test and pathologic findings in 2-month old two Pointer dogs. Typical T. canis eggs were detected in the fecal test. Numerous adult ascarids in the lumen of small intestine and stomach in one dog and multifocal white necrotic lesions in lung, liver, and kidney in another dog were observed grossly. Histologically, multifocal necrosis, eosinophilic inflammation and intralesional ascarid larva were prominent findings in the lung, liver and kidney.