Tryptanthrin Reduces Campylobacter jejuni Colonization in the Chicken Gut by a Bactericidal Mechanism.

Campylobacter jejuni is a leading cause of foodborne bacterial gastroenteritis worldwide, and raw or undercooked chicken meat is considered the major source of human campylobacteriosis. In this study, we identified 36 compounds that showed inhibitory effects on C. jejuni growth at low concentrations by screening a chemical compound library. Three of the 36 compounds were herbal compounds, including tryptanthrin (TRP), an indoloquinazoline alkaloid. TRP has been reported to have a variety of biological properties, such as antimicrobial, anti-inflammatory, and antitumor activities, but there was previously no information about its anti-C. jejuni activity. We further conducted in vitro and in vivo experiments to evaluate the potential of TRP for the control of C. jejuni in chicken farms. The MIC of TRP for C. jejuni was much lower than that of 13 other herbal compounds that were previously reported to have anti-C. jejuni activities. Time-kill assays under growing and nongrowing conditions demonstrated that TRP has bactericidal activity against C. jejuni. In addition, TRP showed a narrow-spectrum antimicrobial effect against C. jejuni, and there was little potential for the development of TRP-resistant C. jejuni during serially passaged culture. In chick infection experiments, the administration of TRP in drinking water significantly reduced the cecal colonization of C. jejuni when TRP was used either before or after C. jejuni infection. These data suggest that TRP is effective for the control of C. jejuni in chicken farms. IMPORTANCE Campylobacter is a widespread pathogen in the food chain of chickens. Once chickens become infected, large numbers of Campylobacter cells are excreted in their feces. The development of an effective material for reducing the amount of Campylobacter in the chicken intestinal tract will make it possible to reduce the contamination of the food chain with Campylobacter and to produce safe and secure chicken meat. In the present study, in vivo experiments revealed that the use of an herbal compound, tryptanthrin, significantly reduced the number of Campylobacter cells in the chicken gut by a bactericidal mechanism. Furthermore, our in vitro experiments demonstrated that, compared with the other herbal compounds, tryptanthrin achieved antimicrobial activity against C. jejuni at the lowest concentration. The use of tryptanthrin may lead to the development of a novel control measure for reducing the colonization of C. jejuni in the food chain.

[A Case of Breast Cancer in the Elderly Localized in the Nipple].

An 89-year-old woman presented to our clinic with a complaint of a wound in the left nipple. The pathological diagnosis via skin biopsy revealed adenocarcinoma. A physical examination, mammography, ultrasonography, and CT scan revealed a mass in the left nipple. However, a definite diagnosis could not be established by skin biopsy. Left breast-conserving surgery and sentinel lymph node biopsy were performed for diagnosis and treatment. Histological examination revealed a scirrhous type invasive ductal carcinoma in the left nipple and areola with skin invasion and lymph node metastasis. Radiation and hormone therapy were used as adjuvant therapy. She is alive with no local recurrence for 5 months post surgery. Since ductal carcinoma of the nipple is uncommon, we present this case report along with a review of the relevant literature.

[A Case of Stage â £ Breast Cancer Treated with Mastectomy after Spontaneous Removal of a Cosmetic Breast Implant].

A 51-year-oldwoman came to our hospital complaining of a skin ulcer in the left breast. She hadpreviously undergone cosmetic breast augmentation by placement of a bag prosthesis under each mammary gland. She was diagnosed with Stage Ⅳ(T4bN1M1)breast cancer with multiple bone metastases. Following the diagnosis, 3 regimens of hormonal therapy were sequentially administered. The treatment was then switched to chemotherapy following confirmation of tumor progression in the left breast tumor. After 3 cycles of paclitaxel andbevacizumab as the second-line of chemotherapy, the size of the left breast tumor was remarkably reduced. Mastectomy with axillary lymph node sampling and removal of the implant were scheduled for local control. However, due to gradual exposure of the implant under the left breast, it was spontaneously removedfrom the original position when the patient was waiting for the surgery. Therefore, only mastectomy with axillary lymph node sampling was performed, followed by 45 Gy/25 times of postmastectomy and locoregional lymph node irradiation. Six months after the surgery, the patient is alive with no signs of local recurrence.

Salmonella Genomic Island 3 Is an Integrative and Conjugative Element and Contributes to Copper and Arsenic Tolerance of Salmonella enterica.

Salmonella genomic island 3 (SGI3) was first described as a chromosomal island in Salmonella 4,[5],12:i:-, a monophasic variant of Salmonella enterica subsp. enterica serovar Typhimurium. The SGI3 DNA sequence detected from Salmonella 4,[5],12:i:- isolated in Japan was identical to that of a previously reported one across entire length of 81 kb. SGI3 consists of 86 open reading frames, including a copper homeostasis and silver resistance island (CHASRI) and an arsenic tolerance operon, in addition to genes related to conjugative transfer and DNA replication or partitioning, suggesting that the island is a mobile genetic element. We successfully selected transconjugants that acquired SGI3 after filter-mating experiments using the S. enterica serovars Typhimurium, Heidelberg, Hadar, Newport, Cerro, and Thompson as recipients. Southern blot analysis using I-CeuI-digested genomic DNA demonstrated that SGI3 was integrated into a chromosomal fragment of the transconjugants. PCR and sequencing analysis demonstrated that SGI3 was inserted into the 3' end of the tRNA genes pheV or pheR The length of the target site was 52 or 55 bp, and a 55-bp attI sequence indicating generation of the circular form of SGI3 was also detected. The transconjugants had a higher MIC against CuSO4 compared to the recipient strains under anaerobic conditions. Tolerance was defined by the cus gene cluster in the CHASRI. The transconjugants also had distinctly higher MICs against Na2HAsO4 compared to recipient strains under aerobic conditions. These findings clearly demonstrate that SGI3 is an integrative and conjugative element and contributes to the copper and arsenic tolerance of S. enterica.

Transcriptomic analysis of Campylobacter jejuni grown in a medium containing serine as the main energy source.

Campylobacter jejuni is one of the most important causes of food-borne diseases in industrialized countries. Amino acids are an important nutrient source for this pathogen because it lacks enzymes related to glycolysis. However, the metabolic characteristics of C. jejuni grown in a nutrient-restricted medium with specific amino acids have not been fully elucidated. This study shows that C. jejuni NCTC 11168 grows well in a nutrient-restricted medium containing serine, aspartate, glutamate, and proline. Subtracting serine significantly reduced growth, but the removal of the three other amino acids did not, suggesting that serine is a priority among the four amino acids. A transcriptomic analysis of C. jejuni NCTC 11168 grown in a medium with serine as the main energy source was then performed. Serine seemed to be sensed by some chemoreceptors, and C. jejuni reached an adaptation stage with active growth in which the expression of flagellar assembly components was downregulated and the biosyntheses of multiple amino acids and nucleotide sugars were upregulated. These data suggest that C. jejuni NCTC 11168 requires serine as a nutrient.

[A Case of Liver Metastases of Ampullary Carcinoma with Clinical Complete Response Treated with Gemcitabine plus Cisplatin].

We report a case of liver metastases of ampullary carcinoma that achieved clinical complete response after gemcitabine plus cisplatin(GC)combination chemotherapy. A 69-year-old man with obstructive jaundice was diagnosed with ampullary carcinoma and underwent laparoscopic pancreaticoduodenectomy. Postoperative histopathological examination revealed pT3aN0M0, Stage ⅡA adenocarcinoma of the papilla of Vater. Five months after surgery, multiple liver metastases were identified by CT and MRI. The patient received GC chemotherapy intravenously at doses of 1,000 and 25mg/m2 on days 1 and 8, respectively, every 3 weeks. After 3 courses of GC chemotherapy, a CT scan revealed that the liver metastases reduced in size, and PR was achieved based on the RECIST standard. However, Grade 3 neutropenia appeared. After 7 courses, the liver metastases disappeared, and the patient had achieved CR. After 9 courses, the clinical CR continued. Approximately 14 months have passed since the recurrence, and the patient is currently alive.

[Long-Term Survival in a Case of Breast Cancer with Brain Metastases and No Other Distant Metastases Treated by Surgical Removal and Gamma Knife Radiosurgery].

A 44-year-oldwoman was diagnosedwith right breast cancer andund erwent mastectomy andaxillary lymph node dissection in February 2006. She was pathologically diagnosed with invasive ductal carcinoma without lymph node metastasis. Immunohistochemical examination showedthat the tumor was estrogen receptor positive, progesterone receptor negative, andhada HER2 status score of 0. She received 4 cycles of AC, followedby leuprorelin andtamoxifen. Several metastases were identified in the right supraclavicular lymph nodes in August 2008 during the endocrine therapy. Then, she received S-1 as the first-line chemotherapy. Although metastases showed complete response, she developed an eye disorder caused by S-1 and thus the treatment agent was changedto leuprorelin andanastrozole. She complainedof headache andright homonymous hemianopsia in November 2013. MRI showeda 42mm diameter tumor in the left occipital lobe, suspectedto be brain metastasis from breast cancer. Craniotomy was performedto remove the brain tumor, which was pathologically diagnosedas metastasis from breast cancer. In the brain tumor, the estrogen receptor status hadchangedto negative, but the HER2 status remained unchanged, showing a score of 0. Vinorelbine was administered after the brain surgery. Unfortunately, brain metastasis was foundin the dura mater near the surgical cavity, andgamma knife radiosurgery was performedin January 2014. Thereafter, brain metastases were repeatedly found, and gamma knife radiosurgery was again performed in January 2015, September 2016, and February 2017. In addition, a large tumor appearedin the left occipital lobe andwas surgically removed in June 2016. No other distant metastases were found, andvinorelbine was continueduntil February 2018. Because the patient developed dyslexia caused by gamma knife-induced radiation necrosis, bevacizumab was administered between November 2018 and April 2019. MRI showed that the edema due to radiation necrosis reduced and dyslexia symptoms improved. As of now, she has survivedfor 5 years and 6 months after the diagnosis of brain metastases.

[A Middle-Term Survival Case of Pancreas Tail Cancer with Colonic Obstruction].

A 63-year-old man had abdominal pain and sequential constipation and diarrhea. He complained of abdominal pain and vomiting, and was admitted to the hospital with a diagnosis of ileus. CT demonstrated a colonic obstruction at the splenic flexure, which was suspected to be colon cancer. Ileostomy was performed in March 2015, and he underwent radical resection in May 2015. Cancer of the pancreas tail had invaded the spleen, colon, stomach, and left renal capsule. Distal pancreatectomy was performed, along with extended right hemicolectomy, left nephrectomy, partial gastrectomy, and stoma closure. He received adjuvant chemotherapy for 6 months after the operation. He is alive without recurrence of pancreatic cancer for over 3 years.

Impact of biomarker changes during neoadjuvant chemotherapy for clinical response in patients with residual breast cancers.

BACKGROUND: Residual cancer burden or Ki67 expression levels in residual tumors reportedly provided significant prognostic information for a non-pathological complete response subset after neoadjuvant chemotherapy (NAC). However, the significance of Ki67 reduction for clinical response during chemotherapy in each subtype or menopausal status is yet to be determined. METHODS: A total of 183 breast cancers surgically removed after chemotherapy were recruited for this study. Expression levels of estrogen receptor (ER), progesterone receptor (PgR), and Ki67 were determined immunohistochemically for semiquantitative measurement and these biomarkers were compared in pre- and post-NAC samples from pathological non-responders (n = 125). Responses to chemotherapy were evaluated both clinically and pathologically. RESULTS: Ki67 expression levels after NAC (median 5 %, range 0-70 %) were significantly reduced compared with before NAC (25, 1-80 %, P < 0.0001), but only in patients who attained clinical response. This significant suppression of Ki67 in clinical responders was consistently observed in breast cancers from the ER-positive subset, but not the ER-negative subset in the total test set (n = 120). These observations were also made in the validation set (n = 63). Among premenopausal, but not postmenopausal patients, a significant decrease in PgR expression levels was detected in breast cancers of patients who attained clinical response (pre-NAC 50, 0-100 %, post-NAC 5, 0-20 %; P = 0.0003). CONCLUSION: The impact of Ki67 suppression on clinical response seems to be restricted to ER-positive breast cancers. Since PgR expression levels of premenopausal ER-positive cancers were significantly reduced in clinical responders, inhibition of estrogen signaling due to chemotherapy-induced amenorrhea may be involved in this association.

High levels at baseline of serum pyridinoline crosslinked carboxyterminal telopeptide of type I collagen are associated with worse prognosis for breast cancer patients.

It is speculated that adjuvant use of bisphosphonate reduces recurrence in breast cancer patients through suppression of bone resorption. To determine the prognostic impact of bone resorption markers, we investigated serum levels of the pyridinoline crosslinked carboxyterminal telopeptide of type I collagen (1CTP) and N-terminal crosslinking telopeptides of type I collagen (NTX). 1CTP and NTX were measured at baseline (before operation or neoadjuvant therapies) and afterward in 469 patients operated on breast cancer. The optimal cutoff value of 1CTP for relapse-free survival (RFS) was set at 3.6 ng/ml with an area under the receiver operating characteristics curve of 0.641 [95% confidence interval (CI) = 0.560-0.721; p = 0.0011]. However, we were unable to determine a significant cutoff value for NTX. RFS was significantly worse for 1CTP-high patients with than for those with low levels of 1CTP (p = 0.0002). Multivariate analysis with tumor size, lymph node metastasis, and nuclear grade showed that 1CTP was a significant independent prognostic factor (hazard ratio = 2.04, 95% CI = 1.13-3.68; p = 0.018). Worse prognosis for the subset with high 1CTP levels applied only to postmenopausal patients (p = 0.0002). RFS of 130 patients whose 1CTP changed from low at baseline to high at 6 months postoperatively showed RFS almost as poor as that for patients with high 1CTP throughout. These findings suggest that 1CTP may be useful not only for identifying patients with unfavorable prognosis, but also for selecting patients who may benefit from administration of bone-modifying agents in an adjuvant setting.

Gastric cancer diagnosed after Helicobacter pylori eradication in diabetes mellitus patients.

BACKGROUND: Helicobacter pylori infection is the most important risk factor for gastric cancer, for which eradication therapy is commonly performed. However, gastric cancer is sometimes discovered after successful eradication of H. pylori. Much evidence indicates that diabetes mellitus (DM) is a risk factor for gastric cancer. The incidence and characteristics of gastric cancer diagnosed after H. pylori eradication in DM patients remain to be determined. METHODS: We followed the clinical course of patients who underwent H. pylori eradication therapy at our institution. Endoscopy was performed before and after eradication. We compared the incidence and clinical characteristics of gastric cancer arising in DM and non-DM patients. RESULTS: In total, 965 patients who underwent successful eradication (518 DM and 447 non-DM patients) were followed-up for an average of 4.5 years. During the follow-up period, 21 gastric cancers were diagnosed (12 in DM patients and 9 in non-DM patients). The incidence of gastric cancer after eradication was not significantly different between DM and non-DM patients (0.485 and 0.482 %/year, respectively). There was no significant difference in the pathology, diameter, depth, location, or treatment of gastric cancer between patients with and without DM. CONCLUSION: The incidence and characteristics of gastric cancer occurring after H. pylori eradication were comparable between DM and non-DM patients.

Influence of body mass index on clinicopathological factors including estrogen receptor, progesterone receptor, and Ki67 expression levels in breast cancers.

BACKGROUND: High body mass index (BMI) is associated not only with a higher incidence of breast cancers but also with poorer prognosis. It is speculated that both enhanced production of estrogens and other factors associated with obesity are involved in these associations, but the biological characteristics associated with high BMI have yet to be thoroughly identified. METHODS: We studied 525 breast cancers, focusing on biological differences between tumors associated with high and low BMI and by immunohistochemically defined intrinsic subtype. Ki67 expression levels were used to differentiate luminal A from luminal B estrogen receptor (ER)+/human epidermal growth factor receptor 2 (HER2)-breast cancers. RESULTS: Premenopausal patients with high BMI showed a significantly higher frequency of lymph node metastasis (46.4 % vs. 22.9 %, P = 0.005) and tended to have a larger tumor size (P = 0.05) and higher nuclear grade (P = 0.07) than those with low BMI. These differences were not observed among postmenopausal patients. BMI was not associated with distribution of breast cancer subtypes, and ER, progesterone receptor (PR), and Ki67 expression levels of each subtype showed no differences between high and low BMI among premenopausal patients. CONCLUSION: Higher BMI might influence aggressive tumor characteristics among premenopausal patients, but its influence on ER, PR, and Ki67 expression levels seems to be limited.

Nationwide analysis of antimicrobial resistance in pathogenic Escherichia coli strains isolated from diseased swine over 29 years in Japan.

Pathogenic Escherichia coli strains are important causes of several swine diseases that result in significant economic losses worldwide. In Japan, the use of antimicrobials in swine is much higher than that in other farm animals every year. Antimicrobial resistance in pathogenic E. coli strains also heavily impacts the swine industry due to the limited treatment options and an increase in the potential risk of the One Health crisis. In 2016, we investigated 684 Japanese isolates of swine pathogenic E. coli belonging to four major serogroups and reported the emergence and increase in the highly multidrug-resistant serogroups O116 and OSB9 and the appearance of colistin-resistant strains. In the present study, by expanding our previous analysis, we determined the serotypes and antimicrobial resistance of 1,708 E. coli strains isolated from diseased swine between 1991 and 2019 in Japan and found recent increases in the prevalences of multidrug-resistant strains and minor serogroup strains. Among the antimicrobials examined in this study that have been approved for animal use, a third-generation cephalosporin was found to be effective against the most isolates (resistance rate: 1.2%) but not against highly multidrug-resistant strains. We also analyzed the susceptibilities of the 1,708 isolates to apramycin and bicozamycin, both which are available for treating swine in Japan, and found that the rates of resistance to apramycin and bicozamycin were low (6.7% and 5.8%, respectively), and both antimicrobials are more effective (resistance rates: 2.7% and 5.4%, respectively) than third-generation cephalosporins (resistance rate: 16.2%) against highly multidrug-resistant strains.

Influence of Helicobacter pylori eradication on the management of type 2 diabetes.

BACKGROUND/AIMS: H. pylori eradication therapy has been widely performed. In addition, the number of patients with type 2 diabetes is increasing worldwide. The aim of this study was to understand the influence of H. pylori eradication therapy on the management of type 2 diabetes. METHODOLOGY: A total of 174 patients with type 2 diabetes who did not have an active peptic ulcer or serious complications and were cured successfully of their H. pylori infection at our institute were included in this study. The time course of mean glycosylated hemoglobin (HbA1c) values and body mass index (BMI) during the year before and after H. pylori eradication were assessed by a paired Student's t-test. RESULTS: No significant changes in mean HbA1c values were observed during the year before or after eradication. However, the mean BMI, which did not change during the year before eradication, increased significantly at 6 months (23.1±2.6kg/m2, p<0.05) and 12 months (23.1±2.7kg/m2, p<0.05) after eradication as compared with the time point of eradication (22.9±2.6kg/m2). CONCLUSIONS: H. pylori eradication significantly increased BMI but not HbA1c in patients with type 2 diabetes, despite diabetes treatment.

Inhibitor of kappaB kinase beta regulates gastric carcinogenesis via interleukin-1alpha expression.

BACKGROUND & AIMS: Nuclear factor-kappaB (NF-kappaB) is an important transcription factor involved in various biological processes, including carcinogenesis. However, it is unknown whether NF-kappaB activation is involved in gastric carcinogenesis. METHODS: To explore the roles of inhibitor of kappaB kinase (IKKbeta), the key kinase for NF-kappaB activation, in gastric epithelium, we established a conditional gastric mucosal epithelium knockout mouse (Ikkbeta(DeltaST)). Gastric cancer was induced using N-methyl-N-nitrosourea (MNU). After 8 months, the number of tumors and their sizes were evaluated. Apoptosis was analyzed by terminal deoxynucleotidyl transferase-mediated deoxyuridine nick-end labeling staining, and levels of inflammatory cytokines were measured. RESULTS: No phenotypical or histologic difference was observed between untreated Ikkbeta(DeltaST) and controls (Ikkbeta(F/F)). The number of tumors was significantly less in the MNU-treated Ikkbeta(DeltaST) group than in the Ikkbeta(F/F) group (mean +/- standard error, 2.21 +/- 0.48 vs 0.80 +/- 0.23), and the size of the tumors did not differ (2.75 +/- 0.99 vs 2.89 +/- 1.12 mm). After a single oral dose of MNU, interleukin (IL)-1alpha was up-regulated significantly in control mice compared with Ikkbeta(DeltaST) mice, whereas the levels of IL-1beta, IL-6, and tumor necrosis factor-alpha were unchanged. MNU significantly increased apoptotic cell death in Ikkbeta(DeltaST) mice compared with Ikkbeta(F/F) mice, and apoptosis was dependent on decreased IL-1alpha expression. IL-1alpha also induced the proliferation of gastric cancer cells. Fewer tumors were observed in IL-1-receptor knockout mice (Il-1r(-/-); 1.17 +/- 0.44) than in control mice (2.42 +/- 0.52). CONCLUSIONS: IKKbeta regulates gastric carcinogenesis via IL-1alpha expression, which is associated with anti-apoptotic signaling and cell proliferation.

[A case of gastric cancer with liver metastasis had a good reaction to S-1/CDDP chemotherapy after S-1 chemotherapy was ineffective].

A woman in her sixties underwent total gastrectomy for gastric cancer. The pathological diagnosis was pT3, pN3, sH0, pCY0, sP0, sM0, fStage IV. Chemotherapy with S-1 was used after surgical treatment. Because a CT scan after three courses chemotherapy showed the paraaortic lymph nodes swelling, combination chemotherapy with S-1 and docetaxel was used as a second-line chemotherapy. When the CT scan after 8 courses of this combination chemotherapy revealed multiple liver metastases, the chemotherapy was changed to CPT-11 monotherapy and paclitaxel monotherapy as the third-and fourth-line chemotherapy, respectively. In spite of those chemotherapies, the metastatic disease progressed, and therefore, combination chemotherapy with S-1 and CDDP was used as the fifth-line chemotherapy. After 6 courses of this treatment, serum CEA and CA19-9 levels dropped into the normal range. Multiple liver metastases were markedly reduced, and were considered as a partial response(PR). The patient is still alive, maintaining the effect of PR for 17 months without any adverse effects except appetite loss and vomiting of grade 2.

[A case whose lung metastasis was detected and resected eleven years after resection of primary colon cancer].

In July 1999, a 79-year-old man underwent sigmoidectomy and D3 lymphadectomy for sigmoid colon cancer (ss, n(-), stage II, cur A). In September 2000, hepatectomy of right lobe and cholecystectomy were performed for his liver metastasis. Every three to six months follow-up had been kept since adjuvant chemotherapy (200 mg/day of 5-FU per os for two years) completed. Eleven years and two months after sigmoidectomy (in September 2010), a chest X-ray examination detected a small nodule in upper area of his right lung, which was diagnosed as either primary lung cancer or metastatic lung tumor followed by chest CT scan and PET-CT examination. In November 2010, laparoscopy-assisted partial resection of his right lung was performed. Histochemical examination of the resected lung tumor resulted cytokeratin 7(-), cytokeratin 20(+) and TTF-1(-), confirming its final diagnosis as lung metastasis from sigmoid colon cancer. He has been alive for six months without any recurrence since resection of his lung metastasis. It was a very rare case to have more than ten-year interval between colon cancer resection and detection of its lung metastasis. However, when we diagnosed the patient with lung tumor, who had undergone a colorectal resection, we should consider if he had a lung metastasis from colorectal cancer.

Investigation of a Novel S-1 Administration Schedule for Treating Metastatic and Recurrent Breast Cancer (KBCOG13).

BACKGROUND/AIM: S-1, a 5-fluorouracil(5-FU) oral anti-cancer drug, has been traditionally used with a schedule of 4-week oral administration followed by 2-week rest for breast cancer treatment. We, herein, aimed to investigate the clinical efficacy and safety of a schedule of 2-week oral administration followed by 1-week rest for patients with metastatic breast cancer. PATIENTS AND METHODS: We enrolled patients with HER2-negative metastatic breast cancer who had not received prior chemotherapy. S-1 was administered consecutively for 2-weeks followed by a 1-week rest. RESULTS: Between September 1, 2013 and August 31, 2016, 32 patients were enrolled. The median follow-up time was 32.1 months. The median progression-free survival (PFS) was 9.4 months. Overall survival (OS) was 41.0 months, time to treatment failure (TTF) was 7.8 months, response rate (RR) was 31.3%, and disease control rate (DCR) was 78.1%. The incidence of grade 3 side-effects was not high. CONCLUSION: The 3-week schedule of S-1 can be considered useful as a treatment for patients with metastatic breast cancer, helping in maintaining a high quality of life.

Duplication of blaCTX-M-1 and a class 1 integron on the chromosome enhances antimicrobial resistance in Escherichia coli isolated from racehorses in Japan.

OBJECTIVES: Extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae have become a cause for great concern. Although some studies have reported the prevalence of ESBL-producing bacteria and ESBL-encoding genes in horses worldwide, the genetic structure surrounding the ESBL gene has not been analysed in detail. In the present study, we isolated two ESBL-producing Escherichia coli strains from diseased racehorses in Japan and demonstrated the mechanisms underlying the acquisition of their antimicrobial resistance (AMR) genes. METHODS: Two ESBL-producing E. coli strains (E148 and E189) were isolated from the heart and liver of horses with endocarditis and sepsis in 2014 and 2016, respectively, in Japan. Complete genomic sequences of the two strains were analysed using a PacBio RSII sequencer. Antimicrobial susceptibility testing was performed by the agar dilution method. RESULTS: The two isolates possessed a chromosomal AMR gene cluster containing blaCTX-M-1 that was similar to the pEQ1 plasmid found in E. coli isolated from a racehorse in the Czech Republic. In one of the two strains, tandem duplication of the 16-kb region containing blaCTX-M-1 and a class 1 integron, which occurred via IS26-mediated recombination, increased minimum inhibitory concentrations (MICs) associated with the duplicated AMR genes. CONCLUSION: Chromosomal blaCTX-M-1 possibly derived from the pEQ1 or pEQ1-like plasmid was found in Japanese equine E. coli isolates. In Japanese strains, many AMR genes containing blaCTX-M-1 and the class 1 integron are highly accumulated in one region on the chromosome, and the AMR of E. coli was enhanced via the IS26-mediated duplication of the AMR gene cluster.

A survey of antimicrobial resistance in Escherichia coli isolated from wild sika deer (Cervus nippon) in Japan.

We examined the antimicrobial susceptibility of 848 Escherichia coli isolates from 237 feces samples of wild sika deer (Cervus nippon) captured between 2016 and 2019 in 39 of the 47 prefectures of Japan. Five of the 237 wild sika deer (2.1%) carried E. coli with resistance to at least one antimicrobial, and all the resistant isolates showed resistance to tetracycline. The resistant isolates contained antimicrobial resistance genes that were similar to those in E. coli derived from humans and farm animals. Although wild sika deer are not currently likely to be a source for the transmission of antimicrobial resistance in Japan, they can potentially mediate antimicrobial resistance spread by coming into contact with humans, animals, and their surroundings.