Comparative genetic characterization of CMY-2-type beta-lactamase producing pathogenic Escherichia coli isolated from humans and pigs suffering from diarrhea in Korea.

BACKGROUND: Pathogenic Escherichia coli are an important cause of bacterial infections in both humans and pigs and many of antimicrobials are used for the treatment of E. coli infection. The objective of this study was to investigate the characteristics and relationship between humans and pigs regarding third-generation cephalosporin resistance and CMY-2-producing E. coli in Korea. RESULTS: All 103 third-generation cephalosporin-resistant E. coli isolates showed multidrug resistance. Also, except for ß-lactam/ß-lactamase inhibitor combinations, all antimicrobials resistant rates were higher in pigs than in humans. A total of 36 isolates (humans: five isolates; pigs: 31 isolates) were positive for the CMY-2-encoding genes and thirty-two (88.9%) isolates detected class 1 integrons with 10 different gene cassette arrangements, and only 1 isolate detected a class 2 integron. The most common virulence genes in pigs were LT (71.0%), F18 (51.6%), and STb (51.6%), while stx2 (80.0%) was the most frequently detected gene in humans. Stx2 gene was also detected in pigs (6.5%). Interestingly, 36 CMY-2-producing E. coli isolates showed a high diversity of sequence types (ST), and ST88 was present in E. coli from both pigs (11 isolates) and humans (one isolate). CONCLUSION: Our findings suggest that a critical need for comprehensive surveillance of third-generation cephalosporin resistance is necessary to preserve the usefulness of third-generation cephalosporins in both humans and pigs.

Outbreak of severe diarrhea due to zoonotic Cryptosporidium parvum and C. xiaoi in goat kids in Chungcheongbuk-do, Korea.

Severe diarrhea was reported in goat kids in Chungcheongbuk-do, Korea, from 2021 to 2023, and Cryptosporidium infection was suspected. To confirm the cause of this outbreak, fecal samples were collected from goat farms where diarrhea had been reported and analyzed for Cryptosporidium infection using a molecular assay. A total of 65 fecal samples, including 37 from goats with diarrhea and 28 from goats without diarrhea, were collected from six goat farms. Forty-eight of the goats were kids (<2 months) and 17 were adults (>1 year). Cryptosporidium was identified in 53.8% (35/65) of total samples. Overall, 86.5% (32/37) of the diarrheic fecal samples tested positive; however, Cryptosporidium was not detected in any fecal sample from non-diarrheic adult goats. Therefore, cryptosporidiosis was significantly associated with diarrhea in goat kids, and adult goats were not responsible for transmission of Cryptosporidium to them. Phylogenetic analysis and molecular characterization revealed two Cryptosporidium species, namely, C. parvum (n = 28) and C. xiaoi (n = 7). In the C. parvum-positive samples, gp60 gene analysis revealed three zoonotic subtypes-IIaA18G3R1, IIdA15G1, and IIdA16G1. To the best of our knowledge, this study is the first to identify C. parvum IIaA18G3R1 and IIdA16G1 in goats, as well as the first to identify C. xiaoi in goats in Korea. These results suggest that goat kids play an important role as reservoir hosts for different Cryptosporidium species and that continuous monitoring with biosecurity measures is necessary to control cryptosporidiosis outbreaks.

Antimicrobial resistance, virulence genes, and phylogenetic characteristics of pathogenic Escherichia coli isolated from patients and swine suffering from diarrhea.

BACKGROUND: Escherichia (E.) coli causes colibacillosis in swine and humans, and is frequently associated with antimicrobial resistance. In this study we aimed to compare antimicrobial resistance, O-serogroups, virulence genes, and multi-locus sequence type of E. coli between isolates from pigs and patients suffering from diarrhea, and the most prevalent pathogenic E. coli strain from swine isolates in Korea. METHODS: We tested 64 and 50 E. coli strains from pigs and patients suffering from diarrhea for antimicrobial susceptibility test, virulence genes, O-serogroups, and multi-locus sequence typing. RESULTS: We confirmed that isolates from swine showed significantly higher resistance than from those from patients, especially to fluoroquinolone (ciprofloxacin: 37.5 and 10.0%; norfloxacin: 29.7 and 8.0%, respectively). Stx1 (46.0%) was most frequently detected in patients followed by stx2 (38.0%). There was no significant difference in stx2 (swine: 23.4%, patients: 38.0%). In isolates from patients, O157 (12.0%) was the most prevalent O-serogroup, and two isolates (3.1%) from pigs were confirmed to have O157. Additionally, sequence type (ST) 10 (swine: 6 isolates, patients: 2 isolates) and ST 88 (swine: 2 isolates, patients: 1 isolate) were simultaneously detected. CONCLUSIONS: We found that both isolates from swine and human had the stx2 gene, which could cause severe disease. Moreover, antimicrobial resistance was significantly higher in pigs than in patients. These results suggest that pig could act as a reservoir in human infection and antimicrobial resistance could be transferred to human from pigs.

Molecular characteristics of fluoroquinolone-resistant Escherichia coli isolated from suckling piglets with colibacillosis.

OBJECTIVES: Colibacillosis is a frequent enteric disease in the pig industry that causes significant economic losses. The objective of this study was to investigate the molecular characteristics of fluoroquinolone (FQ)-resistant E. coli isolates from suckling piglets with colibacillosis. RESULTS: A total of 43 FQ-resistant E. coli isolates were tested in this study and all isolates showed multi-drug resistance (MDR) and mutations in quinolone resistance determining regions (gyrA or parC). Especially, FQ-resistant E. coli isolates with double mutations in both gyrA and parC were shown a high FQs minimum inhibitory concentration (≥ 64 mg/L for ciprofloxacin, ≥ 128 mg/L for enrofloxacin, and ≥ 256 mg/L for norfloxacin). Among 43 FQ-resistant E. coli isolates, 12 (27.9%) were showed plasmid-mediated quinolone resistance (PMQR) positive E. coli. Prevalence of PMQR gene, aac(6')-Ib-cr, qnrS, and qepA, were identified in 7, 3, and 2 E. coli isolates, respectively. We identified the following in PMQR-positive E. coli isolates: the tetracycline resistance genes tetD (12 isolates, 100.0%), tetE (12 isolates, 100.0%), tetA (11 isolates, 91.7%), and tetB (1 isolate, 8.3%); ß-lactamases-encoding blaCMY-2 (10 isolates, 83.3%), blaTEM-1 (7 isolates, 58.3%), blaOXA-1 (7 isolates, 58.3%), blaSHV-1 (3 isolates, 16.7%), and blaAAC-2 (1 isolate, 8.3%); and the chloramphenicol resistance genes (10 isolates, 83.3%); the sulfonamide resistance genes sul1 (9 isolates, 75.0%) and sul2 (10 isolates, 83.3%); the aminoglycoside modifying enzyme gene aac(3)-II (2 isolates, 16.7%). The F4 (7 isolates, 58.3%), LT:STb:EAST1 (5 isolates, 41.7%), and paa (3 isolates, 25.0%) were most common fimbrial antigen, combinations of toxin genes, and non-fimbrial adhesins genes, respectively. All PMQR-positive E. coli carried class I integrons but only 4 isolates carried the gene cassette. The most prevalent plasmid replicon was FIB (9 isolates, 75.0%), followed by FIC, HI1, and N (7 isolates, 58.3%), respectively. CONCLUSIONS: Because FQ-resistant E. coli can serve as a reservoir of FQ resistant genetic determinants that can be transferred to pathogenic bacteria in humans or pigs, this represents a public health hazard.

Distribution of Gastrointestinal Parasitic Infection in Domestic Pigs in the Republic of Korea: Nationwide Survey from 2020-2021.

This study aimed to examine the distribution of gastrointestinal parasitic infections in domestic pigs in the Republic of Korea. From May 2020 to October 2021, 364 pig fecal samples were collected from 75 farms in 7 Provinces and microscopically examined. A total of 170 (46.7%) pigs were infected with at least one of the following parasites: Balantioides coli, strongyles, Ascaris suum, Trichuris suis, and coccidia. By parasite species, B. coli, strongyles, A. suum, T. suis, and coccidia oocysts or eggs were detected in 144 (39.6%), 24 (6.6%), 14 (3.8%), 4 (1.1%), and 1 (0.3%) samples, respectively. One hundred fifty-four, 15, and 1 cases showed single, double, and triple infections, respectively. Of the swine fecal samples from 75 farms, 69 specimens (92.0%) were infected with 1 or more parasites. All surveyed farms across the country exhibited a positive rate of over 30%, among which the highest positive rate was 65.0% in Chungcheongnam-do, and Jeollabuk-do was followed by 61.9%. Winter showed a statistically lower prevalence than other seasons. This study showed that gastrointestinal parasites are prevalent in pigs in Korea, although the diversity of parasites is low.

Therapeutic Efficacy of Weissella cibaria CMU and CMS1 on Allergic Inflammation Exacerbated by Diesel Exhaust Particulate Matter in a Murine Asthma Model.

Background and Objectives: Diesel exhaust particulate matter (DEPM) is an air pollutant that is associated with asthma. In this study, the therapeutic efficacy of Weissella cibaria strains CMU (Chonnam Medical University) and CMS (Chonnam Medical School) 1, together with the drug Synatura, an anti-tussive expectorant, was investigated in a murine asthma model exacerbated by DEPM. Materials and Methods: BALB/c mice were sensitized with ovalbumin (OVA) before intranasal challenge with OVA and DEPM. W. cibaria CMU, CMS1, and Synatura were administered orally for 21 days. Results: Neither Synatura nor W. cibaria strains affected spleen, liver, or lung weights. W. cibaria strains CMU and CMS1 significantly reduced the levels of interleukin (IL)-4, OVA-specific immunoglobulin E (IgE), and total lung collagen in bronchoalveolar lavage fluid (BALF), similar to those with Synatura, regardless of the oral dose concentration (p < 0.05). In addition, the W. cibaria CMU strain significantly alleviated IL-1ß, IL-6, IL-12, monocyte chemotactic protein-1, and tumor necrosis factor-α in BALF, whereas the CMS1 strain significantly alleviated IL-10 and IL-12 in BALF (p < 0.05); however, Synatura did not show any statistical efficacy against them (p > 0.05). All concentrations of W. cibaria CMU and low concentrations of W. cibaria CMS1 significantly reduced lung bronchiolar changes and inflammatory cell infiltration. Conclusions: In conclusion, W. cibaria CMU in asthmatic mice showed better efficacy than W. cibaria CMS1 in improving asthma exacerbated by DEPM exposure, as well as better results than pharmaceuticals.

First Clinical Cases of Spirometrosis in Two Cats in Korea.

This study reports the first two clinical cases of spirometrosis caused by Spirometra sp. in cats in Korea. In these two cases, the cats vomited, and long proglottids of tapeworm were recovered. The sick cats presented with anorexia and lethargy. However, they unexpectedly showed no diarrhea, which is the main symptom of spirometrosis. Based on a fecal floatation test as well as morphological and molecular analyses, the parasite was diagnosed as Spirometra sp. The 2 cases were treated with praziquantel. This study suggests regular monitoring of health and deworming in companion animals, even when animals are well cared for, with regular preventive medication. Additionally, spirometrosis should be considered in the differential diagnosis in cases of gastrointestinal symptoms in Spirometra endemic areas.

Fluorophosphonate-Based Degrader Identifies Degradable Serine Hydrolases by Quantitative Proteomics.

Novel chemical biology probes linking a serine hydrolase-directed fluorophosphonate warhead and cereblon-binding pomalidomide were assessed for the degradation of serine hydrolases. A quantitative proteomics approach to detect degraded proteins revealed that, despite the engagement of ∼40 serine hydrolases, degradation was achieved for only a single serine hydrolase, lysophospholipase II (LYPLA2).

Effects of Queso Blanco cheese containing Bifidobacterium longum KACC 91563 on fecal microbiota, metabolite and serum cytokine in healthy beagle dogs.

The study describes the effects of administration of Queso Blanco cheese containing Bifidobacterium longum on the fecal microbiota, metabolite and serum cytokine in healthy beagle dogs. Twelve healthy beagle dogs were randomly divided in three groups of four dogs each:a control group, not fed with any cheese, and groups fed with Queso Blanco cheese with B. longum KACC 91563 (QCB) or without B. longum (QC) for 8 weeks. Fecal microbiota was analyzed using a culture-based method and 16s rRNA gene sequencing. Serum cytokine levels, activation of natural killer cells, and proliferation of peripheral blood mononuclear cells were determined. SPME-GC-MS method was used to determine the concentrations of short chain fatty acids and indole in dog feces. Administration of QCB for 4 weeks significantly increased the Bifidobacterium. QCB supplementation for 8 weeks reduceds Enterobacteriaceae and Clostridium perfringens (p < 0.05). The abundance of Fusobacterium, Blautia and Collinesella in QCB group were reduced as compared with the control group. Serum TNF-α and IL-6 levels at 8 weeks significantly increased in QCB group as compared with QC group. There was no change in the concentrations of total short chain fatty acids by B. longum at 0 and 4 weeks. At week 8, the acetic acid, propionic acid and butyric acid of the QCB and QC groups were significantly decreased compared to the control group. In conclusion, our results demonstrate that administration of QCB had positive effects on fecal microbiota and immune response in beagle dogs. We suggest that Queso Blanco cheese containing B. longum KACC 91563 could be used as a functional food for companion animals.

Serum Metabolic Profiling Reveals Potential Anti-Inflammatory Effects of the Intake of Black Ginseng Extracts in Beagle Dogs.

Black ginseng (BG) has better health benefits than white ginseng. The intake of BG changes the levels of metabolites, such as amino acids, fatty acids, and other metabolites. However, there is no research on the effect of BG extract intake on the metabolic profile of dog serum. In this study, serum metabolic profiling was conducted to investigate metabolic differences following the intake of BG extracts in beagle dogs. The beagle dogs were separated into three groups and fed either a regular diet (RD, control), RD with a medium concentration of BG extract (BG-M), or RD with a high concentration of BG extract (BG-H). Differences were observed among the three groups after the dogs ingested the experimental diet for eight weeks. The concentrations of alanine, leucine, isoleucine, and valine changed with the intake of BG extracts. Furthermore, levels of glycine and ß-alanine increased in the BG-H group compared to the control and BG-M groups, indicating that BG extracts are associated with anti-inflammatory processes. Our study is the first to demonstrate the potential anti-inflammatory effect of BG extract in beagle dogs. Glycine and ß-alanine are proposed as candidate serum biomarkers in dogs that can discriminate between the effects of ingesting BG-H.

Trial data of the anti-obesity potential of a high resistant starch diet for canines using Dodamssal rice and the identification of discriminating markers in feces for metabolic profiling.

INTRODUCTION: Dodamssal rice (Oryza sativa L.) includes high levels of resistant starch (RS), which is a source of dietary fiber. Recently, there has been an increase in the prevalence of obesity in canines; however, the information regarding diet treatments for such a condition is inadequate. OBJECTIVES: Targeted metabolic profiles in canine feces were performed to identify potential biomarkers of RS and demonstrate the effect and potential use of Dodamssal rice as an anti-obesity treatment. METHODS: Study canines were divided into three groups and fed either a regular diet, high-fat diet (HFD), or high-fat diet with Dodamssal rice (DoHFD). Fecal metabolites were analyzed using gas chromatography time-of-flight mass spectrometry and a gas chromatography-flame ionization detector. Multivariate analyses were used to analyze and visualize the obtained data. RESULTS: A total of 52 metabolites were detected in the canine feces. In addition, HFD group feces contained a significantly low level of C12:0. The DoHFD group feces had higher levels of 4-aminobutyric acid, glucose, and 3-hydroxybutyric acid compared to the other groups (p < 0.05). CONCLUSION: For the first time, targeted metabolic profiling in the canine feces in response to three diets was performed. This metabolic profiling approach should be a useful tool to detect discriminating markers as well as assess the effect of diet compositions for anti-obesity treatment of canines. Furthermore, Dodamssal rice may possibly be used not only for canines, but also to treat obesity in other animals and humans.

Properties of Site-Specifically Incorporated 3-Aminotyrosine in Proteins To Study Redox-Active Tyrosines: Escherichia coli Ribonucleotide Reductase as a Paradigm.

3-Aminotyrosine (NH2Y) has been a useful probe to study the role of redox active tyrosines in enzymes. This report describes properties of NH2Y of key importance for its application in mechanistic studies. By combining the tRNA/NH2Y-RS suppression technology with a model protein tailored for amino acid redox studies (α3X, X = NH2Y), the formal reduction potential of NH2Y32(O•/OH) ( E°' = 395 ± 7 mV at pH 7.08 ± 0.05) could be determined using protein film voltammetry. We find that the Δ E°' between NH2Y32(O•/OH) and Y32(O•/OH) when measured under reversible conditions is ∼300-400 mV larger than earlier estimates based on irreversible voltammograms obtained on aqueous NH2Y and Y. We have also generated D6-NH2Y731-α2 of ribonucleotide reductase (RNR), which when incubated with ß2/CDP/ATP generates the D6-NH2Y731•-α2/ß2 complex. By multifrequency electron paramagnetic resonance (35, 94, and 263 GHz) and 34 GHz 1H ENDOR spectroscopies, we determined the hyperfine coupling (hfc) constants of the amino protons that establish RNH2• planarity and thus minimal perturbation of the reduction potential by the protein environment. The amount of Y in the isolated NH2Y-RNR incorporated by infidelity of the tRNA/NH2Y-RS pair was determined by a generally useful LC-MS method. This information is essential to the utility of this NH2Y probe to study any protein of interest and is employed to address our previously reported activity associated with NH2Y-substituted RNRs.

Hydrogen bond network between amino acid radical intermediates on the proton-coupled electron transfer pathway of E. coli α2 ribonucleotide reductase.

Ribonucleotide reductases (RNRs) catalyze the conversion of ribonucleotides to deoxyribonucleotides in all organisms. In all Class Ia RNRs, initiation of nucleotide diphosphate (NDP) reduction requires a reversible oxidation over 35 Å by a tyrosyl radical (Y122•, Escherichia coli) in subunit ß of a cysteine (C439) in the active site of subunit α. This radical transfer (RT) occurs by a specific pathway involving redox active tyrosines (Y122 ⇆ Y356 in ß to Y731 ⇆ Y730 ⇆ C439 in α); each oxidation necessitates loss of a proton coupled to loss of an electron (PCET). To study these steps, 3-aminotyrosine was site-specifically incorporated in place of Y356-ß, Y731- and Y730-α, and each protein was incubated with the appropriate second subunit ß(α), CDP and effector ATP to trap an amino tyrosyl radical (NH2Y•) in the active α2ß2 complex. High-frequency (263 GHz) pulse electron paramagnetic resonance (EPR) of the NH2Y•s reported the gx values with unprecedented resolution and revealed strong electrostatic effects caused by the protein environment. (2)H electron-nuclear double resonance (ENDOR) spectroscopy accompanied by quantum chemical calculations provided spectroscopic evidence for hydrogen bond interactions at the radical sites, i.e., two exchangeable H bonds to NH2Y730•, one to NH2Y731• and none to NH2Y356•. Similar experiments with double mutants α-NH2Y730/C439A and α-NH2Y731/Y730F allowed assignment of the H bonding partner(s) to a pathway residue(s) providing direct evidence for colinear PCET within α. The implications of these observations for the PCET process within α and at the interface are discussed.

Comparative Genetic Characterization of CTX-M-Producing Escherichia coli Isolated from Humans and Pigs with Diarrhea in Korea Using Next-Generation Sequencing.

Pathogenic E. coli causes intra- and extraintestinal diseases in humans and pigs and third-generation cephalosporins are the primary option for the treatment of these diseases. The objective of this study was to investigate the characteristics and correlation between CTX-M-producing E. coli from humans and pigs regarding CTX-M-producing E. coli using next-generation sequencing and bioinformatic tools. Among the 24 CTX-M-producing E. coli, three types of CTX-M genes (CTX-M-12, CTX-M-14, and CTX-M-15) were detected in humans and four types of CTX-M genes (CTX-M-14, CTX-M-15, CTX-M-55, and CTX-M-101) were detected in pigs. A total of 24 CTX-M-producing E. coli isolates also showed the following antimicrobial resistance genes: other B-Lactam resistance gene (75.0%); aminoglycoside resistance genes (75.0%); phenicol resistance genes (70.8%); tetracycline resistance genes (70.8%); sulfonamide resistance genes (66.7%); quinolone resistance genes (62.5%); trimethoprim resistance genes (54.2%); and fosfomycin resistance genes (8.3%). FII (92.3%) and FIB (90.9%) were the most common plasmid replicon in humans and pigs, respectively. A total of thirty-eight different genes associated with virulence 24 CTX-M-producing E. coli and all isolates contained at least more than one virulence gene. A total of 24 CTX-M-producing E. coli isolates showed 15 diverse sequence types (STs): thirteen isolates from human belonged to 6 different STs, and 11 isolates from pig belonged to 9 different STs. The presence of virulence genes in E. coli together with antimicrobial resistance genes (including CTX-M genes) emphasizes the necessity of comprehensive surveillance and persistent monitoring of the food chain to avoid all types of bacterial contamination, regardless of human or pig origin.

Comparative Genetic Characterization of Pathogenic Escherichia coli Isolated from Patients and Swine Suffering from Diarrhea in Korea.

The aim of this study was to compare the virulence factors and antimicrobial resistance of the most common pathogenic Escherichia coli strains in swine and patients with diarrhea in Korea. We examined virulence genes and antimicrobial susceptibility in 85 and 61 E. coli strains isolated from swine and patients with diarrhea, respectively. The most prevalent pathogen in swine was enterotoxigenic E. coli (ETEC) (47.1%), followed by Shiga toxin-producing E. coli (STEC) (32.9%). Similarly, the majority of the patient isolates (50.8%) were proven to be STEC, the most common pathotype, followed by ETEC (23.0%). We found that swine isolates had significantly higher resistance than patient isolates, especially to fluoroquinolones (ciprofloxacin: 37.5% and 16.1%; norfloxacin: 29.7% and 16.1%, respectively). Additionally, sequence type (ST) 100 (swine: 21; patients: 4), ST 1 (swine: 21, patients: 2), ST 10 (swine: 8; patients: 6), ST 641 (swine: 3, patients: 2), and ST 88 (swine: 2, patients: 11) were detected in both swine and humans. In addition, we confirmed that isolates from swine and patients had similar virulence traits and were phylogenetically similar. According to these findings, swine and humans are susceptible to cross infection and the transfer of antimicrobial resistance.

Comparative Study of Intestinal Microbiome in Patients with Ulcerative Colitis and Healthy Controls in Korea.

Ulcerative colitis (UC) poses a contemporary medical challenge, with its exact cause still eluding researchers. This is due to various factors, such as the rising incidence, diagnostic complexities, and difficulties associated with its management. We compared the intestinal microbiome of patients with UC to that of healthy controls to determine the qualitative and quantitative changes associated with UC that occur in the intestinal microbiota. The intestinal bacterial abundance in 40 Korean patients with UC and 25 healthy controls was assayed using via next-generation sequencing. There were five major phyla in both groups: Firmicutes (UC patients: 51.12%; healthy controls: 46.90%), Bacteroidota (UC patients: 37.04%; healthy controls: 40.34%), Proteobacteria (UC patients: 6.01%; healthy controls: 11.05%), Actinobacteriota (UC patients: 5.71%; healthy controls: 1.56%), and Desulfobacteriota (UC patients: 0.13%; healthy controls: 0.14%). Firmicutes was more prevalent in patients with UC (51.12%) compared to that of healthy controls (46.90%). Otherwise, Bacteroidota was more prevalent in healthy controls (40.34%) compared to patients with UC (37.04%). Although there was no significant difference, our results showed a substantially lower gut microbiome diversity in patients with UC (mean: 16.5; 95% confidence interval (CI) = 14.956-18.044) than in healthy controls (mean: 17.84; 95% CI = 15.989-19.691), the beta diversity and the flora structure of the microbiome in patients with UC differed from those in healthy controls. This will be helpful for the development of new treatment options and lay the groundwork for future research on UC. To understand the disease mechanism, it is essential to define the different types of microbes in the guts of patients with UC.

Effects of Antimicrobial Administration Route on Growth and Antimicrobial Resistance in Weaned Piglets.

This study aimed to determine how the route of antimicrobial administration affected the growth performance of weaned piglets. Additionally, we aimed to investigate potential differences between antimicrobial resistance developed by antimicrobials administered orally through drinking water, and those administered through feed, in weaned piglets. The research was undertaken on a farm housing 500 sows and involved 150 weaned piglets at 21 days of age. These piglets were evenly distributed into three groups of equal size: water, feed, and control. Antimicrobials were administered through drinking water and feed in the water and feed groups, respectively, while the control group received no antimicrobial treatment. The observation of piglets continued until they reached 70 days of age. The feed conversion ratio in the water group (1.7 ± 0.78) was significantly higher than in the control (2.4 ± 1.77) and feed (2.7 ± 1.68) groups. Additionally, the route of administration did not affect antimicrobial resistance rates. Based on these results, it can be inferred that administering antimicrobials through drinking water is advantageous for pig farming.

Experimental infection of post-weaned pigs with F18-encoding enterotoxigenic and enterotoxigenic/shigatoxigenic Escherichia coli strain isolated from the diarrheic feces in Korea.

Background: In the porcine industry, Escherichia coli (E. coli) infections have been causing post-weaning diarrhea (PWD) and edema disease (ED) for many years. It is classified into pathotypes and serotypes in animals according to virulence factors. Serotyping is performed for O, K, H, and F antigens, essential for discriminating pathogenicity and epidemiology. Furthermore, E. coli strains that produce F18 fimbriae are major sources of ED and PWD associated with Shiga-toxin producing E. coli (STEC) expressing F18ab and enterotoxigenic E. coli (ETEC) expressing F18ac, respectively. Aim: To investigate the pathogenicity potential and infection characteristics of experimental infection and confirm the pathological features of the Korean STEC/ETEC strains F18ab and F18ac in piglets. Methods: Three-week-old pigs were randomized into three experimental groups: infected G1 (F18ab), infected G2 (F18ac), and G3 (control). General health status was monitored daily, and pathological changes were evaluated. Results: Diarrhea occurred in all infected piglets. Pathological changes were only observed in the small intestine and regional lymph nodes. In G1, mucosal necrosis, inflammatory cell infiltration with hemorrhagic lesions, and apoptotic cell death in the tunica media of arterioles in the small intestine were observed. In contrast, the mucosa and epithelium appeared almost intact, with no abnormal vessel lesions in G2. Conclusion: Both strains, isolated from pigs in Korea, could be infected and did not spread from the alimentary tract to other organs. The pathological features were quite different among the F18 subtypes. The F18ab strain was more virulent than F18ac, and the virulence characteristics of the F18ac strain were more similar to ETEC than STEC.

Comparative genetic characterisation of third-generation cephalosporin-resistant Escherichia coli isolated from integrated and conventional pig farm in Korea.

OBJECTIVES: Pig-farming systems consist of integrated or conventional farms, and many antimicrobials are used to treat bacterial infections. The objective of this study was to compare characteristics of third-generation cephalosporin resistance and extended-spectrum ß-lactamase (ESBL)/pAmpC ß-lactamase-producing Escherichia coli between integrated and conventional farms. METHODS: Third-generation cephalosporin-resistant E. coli was collected from integrated and conventional pig farms from 2021 to 2022. Polymerase chain reaction and DNA sequencing were performed for the detection of ß-lactamase-encoding genes, molecular analysis, and identification of genetic relationships. To determine the transferability of ß-lactamase genes, conjugation assays were conducted. RESULTS: Antimicrobial resistance rates were higher in conventional farms than in integrated farms; ESBL- and pAmpC-lactamase-producing E. coli rates were higher in conventional farms (9.8%) than in integrated farms (3.4%). Fifty-two (6.5%) isolates produced ESBL/pAmpC ß-lactamase genes. Isolates from integrated farms harboured CTX-15 (3 isolates), CTX-55 (9 isolates), CTX-229 (1 isolate), or CMY-2 (1 isolate) genes; isolates from conventional farms harboured CTX-1 (1 isolate), CTX-14 (6 isolates), CTX-15 (2 isolates), CTX-27 (3 isolates), CTX-55 (14 isolates), CTX-229 (1 isolate), and CMY-2 (11 isolates) genes. Of the 52 ESBL/pAmpC ß-lactamase-producing E. coli isolates, class 1 integrons with 11 different gene cassette arrangements were detected in 39 (75.0%) isolates, and class 2 integrons were detected in 3 isolates. The most common sequence type in both integrated and conventional farms was ST5229, followed by ST101, and then ST10. CONCLUSION: Third-generation cephalosporin-resistant patterns and molecular characteristics differed between integrated and conventional farms. Our findings suggest that continuous monitoring of third-generation cephalosporin resistance on pig farms is necessary to prevent the dissemination of resistant isolates.

YBR246W is required for the third step of diphthamide biosynthesis.

Diphthamide, the target of diphtheria toxin, is a post-translationally modified histidine residue that is found in archaeal and eukaryotic translation elongation factor 2. The biosynthesis and function of this modification has attracted the interest of many biochemists for decades. The biosynthesis has been known to proceed in three steps. Proteins required for the first and second steps have been identified, but the protein(s) required for the last step have remained elusive. Here we demonstrate that the YBR246W gene in yeast is required for the last step of diphthamide biosynthesis, as the deletion of YBR246W leads to the accumulation of diphthine, which is the enzymatic product of the second step of the biosynthesis. This discovery will provide important information leading to the complete elucidation of the full biosynthesis pathway of diphthamide.