Pregnancy-Induced Physiologic Adaptation of the Abdominal Aorta Is Associated with Changes in Gene Expression and Genomic Methylation.

BACKGROUND/AIMS: Ten-eleven translocation 2 (Tet2), a DNA demethylase enzyme, has been identified as a master epigenetic regulator of vascular smooth muscle cell plasticity. We hypothesized that pregnancy will induce significant adaptive changes in aortic biomechanics that correlate with the Tet family gene expression. METHODS: Abdominal aortas from pregnant and nonpregnant mice were dissected and cannulated. Intraluminal pressure was adjusted using a pressure-servo system while using a video dimension analyzer to measure the lumen diameter. Quantitative polymerase chain reaction and immunoblot was used to analyze the expression of Tet genes. Global genomic methylation was assessed with the luminometric methylation assay. RESULTS: Compared to the nonpregnant (NP, 706 ± 8 µm) control group, the aortic luminal diameter was significantly increased in both E18.5 (836 ± 14 µm) and PP30 (889 ± 16 µm) mice. Distensibility was reduced in E18.5 (90 ± 4%) mice and returned to NP values (108 ± 2%) in PP30 (108 ± 3%) mice. Tet2 transcription decreased at the beginning of pregnancy and subsequently increased in late gestation, inversely corresponding to changes in global methylation. CONCLUSION: Physiologic changes in the aorta were accompanied by changes in gene expression and genomic methylation, suggesting an epigenetic component to maternal vascular remodeling during pregnancy.

Reduced hydroxymethylation characterizes medulloblastoma while TET and IDH genes are differentially expressed within molecular subgroups.

INTRODUCTION: Medulloblastoma (MB) is an embryonal tumour that originates from genetic deregulation of cerebellar developmental pathways and is classified into 4 molecular subgroups: SHH, WNT, group 3, and group 4. Hydroxymethylation levels progressively increases during cerebellum development suggesting a possibility of deregulation in MB pathogenesis. The aim of this study was to investigate global hydroxymethylation levels and changes in TET and IDH gene expression in MB samples compared to control cerebellum samples. METHODS: The methods utilized were qRT-PCR for gene expression, dot-blot and immunohistochemistry for global hydroxymethylation levels and sequencing for the investigation of IDH mutations. RESULTS: Our results show that global hydroxymethylation level was decreased in MB, and low 5hmC level was associated with the presence of metastasis. TET1 expression levels were decreased in the WNT subgroup, while TET3 expression levels were decreased in the SHH subgroup. Reduced TET3 expression levels were associated with the presence of events such as relapse and death. Higher expression of IDH1 was observed in MB group 3 samples, whereas no mutations were detected in exon 4 of IDH1 and IDH2. CONCLUSION: These findings suggest that reduction of global hydroxymethylation levels, an epigenetic event, may be important for MB development and/or maintenance, representing a possible target in this tumour and indicating a possible interaction of TET and IDH genes with the developmental pathways specifically activated in the MB subgroups. These genes could be specific targets and markers for each subgroup.

Prevalence and genetic profiling of tetracycline resistance (Tet-R) genes and transposable element (Tn916) in environmental Enterococcus species.

Resistance against antimicrobial agents in enterococci is a global concern that not only challenges infection therapy but also make them reservoir of antibiotic resistance in human and animal alike. This study was conducted to establish tetracycline resistance profiles, prevalence of tet genes and transposable element (Tn916) in enterococcal soil and clinical isolates. Enterococci (n = 1210) from different environmental niche were collected and subjected to molecular identification. In total, 361 isolates showed tetracycline resistance at the breakpoint of 32 µg ml-1. MICs (32-512 µg ml-1) were established by both agar and micro-broth dilution methods. Soil isolates (n = 76) were further investigated for Tet genes (tet-A, C, K, L, M, S, O) and Tn916. Major resistance was observed in E. faecium 67% followed by E. faecalis 22%, E. hirae 8% and E. casseliflavus 2.6%. Results revealed that tet(L) was more frequently found in E. faecium 74.5%, while tet(M) was in high prevalence in E. faecalis 82.3%. Tn916 was detected in both clinical and soil isolates (i.e. 43.3% and 19.7%, respectively). RAPD-PCR analysis showed high diversity among the investigated isolates. Cumulatively, our results revealed high-level tetracycline resistance and the presence of multiple Tet genes and transposable element Tn916 in enterococci.

Characterisation of penicillin and tetracycline resistance in Staphylococcus aureus isolated from bovine milk samples in Minas Gerais, Brazil.

This Regional Research Communication describes the characterisation of ampicillin, penicillin and tetracycline resistance in Staphylococcus aureus isolated from bovine subclinical mastitis in Minas Gerais State, Brazil. Ninety S. aureus isolates from bovine mastitis exhibiting phenotypic resistance to ampicillin, penicillin and/or tetracycline were selected for this study. The minimum inhibitory concentration (MIC) of each antibiotic was determined using the E-Test® and the production of beta-lactamase was determined by cefinase disks. The resistance genes blaZ, tet(K), tet(L), tet(M), and tet(O) were investigated by PCR in all of the isolates. The MIC results classified 77, 83 and 71% of the isolates as resistant to ampicillin, penicillin and tetracycline, respectively. The MIC50 and MIC90 were, respectively, 1 and 2 µg/ml for ampicillin, 0·5 and 1 µg/ml for penicillin and 32 and 64 µg/ml for tetracycline. Eighty-six per cent of beta-lactamase producing isolates were detected. Of the 90 isolates investigated, 97% amplified blaZ, 84% amplified tet(K), 9% amplified tet(L), 2% amplified tet(M) and 1% amplified tet(O). Seventy-nine isolates (88%) showed blaZ together with at least one tet gene. S. aureus isolates showed high MIC50 and MIC90 values for the three antimicrobials. The blaZ and tet(K) genes were widespread in the herds studied, and most of the isolates harboured blaZ and tet(K) concomitantly.

Evaluation of phyto-gallic acid as a potential inhibitor of Staphylococcus aureus efflux pump mediated tetracycline resistance: an in-vitro and in-silico study.

Plants contain many bioactive compounds with potent antibacterial and efflux pump inhibitory activity (EPI). In this study, gallic acid extracted from pomegranate molasses by analytical HPLC holds promise as an EPI drug for Staphylococcus aureus mediated tetracycline resistance, it lowered the bacterial resistance and reversed the mechanism via tet family efflux pump, using molecular technique and in-silico molecular docking analysis. Extracted gallic acid combined with tetracycline demonstrated a significant decrease in the minimal inhibitory concentration MIC compared to its single activity. Similarly, little growth and lower fluorescence of S. aureus were observed on ethidium bromide (2.5 mg/mL) agar plates, indicating a reversible efflux pump mechanism and a potent EPI activity. Molecular docking demonstrated a promising affinity binding energy between gallic acid and tet efflux genes, opening a new baseline in bacterial infection treatment. PCR for tetK and Qac A/B genes failed to show any relation between tet genes and gallic acid.

Detection of tetracycline resistance genes and their diversity in Escherichia coli isolated from pig farm waste in Banten province, Indonesia.

Background and Aim: Livestock waste in the form of feces and liquid represents an important reservoir of antibiotic resistance genes (ARGs). Because many ARGs can be horizontally transferred to other pathogens, livestock waste plays an essential role in the emergence and transmission of various ARGs in the environment. Therefore, this study aimed to detect and assess the diversity of tet genes in Escherichia coli isolated from pig farm waste in Banten province, Indonesia. Materials and Methods: Solid waste (feces) and wastewater were collected from 44 pig farms in Banten province. The isolation and identification of E. coli referred to the Global Tricycle Surveillance extended-spectrum beta-lactamase E. coli World Health Organization (2021) guidelines. tet genes were detected using quantitative real-time polymerase chain reaction after dividing pig farms in the province into four clusters based on their adjacent areas and characteristics. Results: tetA, tetB, tetC, tetM, tetO, and tetX were detected in solid waste and wastewater from pig farms, whereas tetE was not detected in either sample type. tetX (100%) and tetO (75%) were the most dominant genes in solid waste, whereas wastewater samples were dominated by tetA, tetM, tetO, and tetX (prevalence of 50% each). Furthermore, eight tet gene patterns were found in pig farm waste (prevalence of 12.5% each). Conclusion: The results showed a high prevalence of tetO and tetX in solid waste and wastewater from pig farms in Banten province. This significant prevalence and diversity indicated the transmission of tet genes from pigs to the environment, posing a serious threat to public health.

Antimicrobial Resistance of E. coli and Salmonella Isolated from Wild Birds in a Rehabilitation Center in Turkey.

Wildlife plays a critical role as a reservoir for zoonosis especially pathogenic enteric bacteria. In this study we evaluated the presence of E. coli and Salmonella isolates from wild birds and determined their antimicrobial resistance. Intestine and fecal samples from 82 dead wild birds obtained from rehabilitation centre, were examined by microbiological analysis, antibiotic susceptibilities against of 18 antimicrobials and presence of tetracycline resistance genes by multiplex and singleplex PCR were investigated. A total of 51 E. coli were identified as well as Salmonella Kentucky and Salmonella Bisberg. A majority of the E. coli isolates were resistant to lincomysin (100%), penicilline (96.1%), kanamycin (80.4%), tetracycline (68.6%), and oxytetracycline (64.7%). All Salmonella serotypes were resistant to lincomycin, nalidixic acid and penicilline.In addition, 58.82% of E. coli isolates had phenotypic resistance to at least three or more antimicrobials. Our results indicated that the high frequency of tetracycline resistance (68.62%) due to the tet (A), tet (B), and tet (D) genes. This is the first report isolating S. Bisberg and determining antibiotic susceptibility of E.coli and Salmonella isolates from wild birds in Turkey. These results will help providing better understand of the dissemination of antibiotic resistancy in the environment, which can be used to potentially decrease spread through bird migration. Moreover, these results help assess the risk of spread of resistance from wild birds to humans.

Characterization of class 1, 2, 3 integrons, ESBL genes and antibiotic susceptibility of Salmonella serotypes from broiler and cattles in Turkey.

Antimicrobial resistance in Salmonella has been associated with the presence of integrons and many other resistance mechanisms contributing to the spread of antimicrobial-resistant genes within and between livestock and human populations. In this study, the presence of Salmonella serovars from broiler and cattle samples and their antimicrobial resistance, integrons, tet resistance, ESBL and resistance genes carriage were investigated. Total of 209 litter (broiler farms) and fecal samples (cattle farms) were examined by bacteriological procedures, susceptibilities against 18 antimicrobials and genes carriages were detected by singleplex and multiplex PCR. A total of 46/209 (22 %) Salmonella strains were isolated. Six different Salmonella serotypes from 46 Salmonella isolates were identified and the most common serotype was S. Infantis 38 (82.6%) from broiler litter; followed by S. Kitenge 3 (6.5 %) from fecal sample. The highest occurrence of resistance observed for penicilline (46/46, %100), lincomycin (43/46, 93.5%) and 42 isolates (43/46, 93.5%) exhibited MDR. The overall occurrence of class 1, 2 and 3 integrons carrying Salmonella in tested samples were 63.04% (29/46), 43.5% (20/46) and 84.8% (39/46) respectively. Out of the 27 isolates produced an ESBL, mostly CTX and TEM. On 46 Salmonella isolates, in 16 (34.8%) Tcr' genes were determined. Genotypic and phenotipic detection of ESBL genes found within integrons from Salmonella isolates from different sources (broiler and cattle) can provide powerful information about health and economic risk associated with transferable multidrug resistance.

Prevalence, Antibiotic-Resistance, and Replicon-Typing of Salmonella Strains among Serovars Mainly Isolated from Food Chain in Marche Region, Italy.

Nontyphoidal salmonellosis (NTS) is the second most commonly reported gastrointestinal infection in humans and an important cause of food-borne outbreaks in Europe. The use of antimicrobial agents for animals, plants, and food production contributes to the development of antibiotic-resistant Salmonella strains that are transmissible to humans through food. The aim of this study was to investigate the presence and the potential dissemination of multidrug-resistant (MDR) Salmonella strains isolated in the Marche Region (Central Italy) via the food chain. Strains were isolated from different sources: food, human, food animal/livestock, and the food-processing environment. Among them, we selected MDR strains to perform their further characterization in terms of resistance to tetracycline agent, carriage of tet genes, and plasmid profiles. Tetracycline resistance genes were detected by PCR and plasmid replicons by PCR-based replicon typing (PBRT). A total of 102 MDR Salmonella strains were selected among the most prevalent serovars: S. Infantis (n = 36/102), S. Derby (n = 20/102), S. Typhimurium (n = 18/102), and a monophasic variant of S. Typhimurium (MVST, n = 28/102). Resistance to sulfisoxazole (86%) and tetracycline (81%) were the most common, followed by ampicillin (76%). FIIS was the most predominant replicon (17%), followed by FII (11%) and FIB (11%) belonging to the IncF incompatibility group. Concerning the characterization of tet genes, tetB was the most frequently detected (27/89), followed by tetA (10/89), tetG (5/89), and tetM (1/89). This study showed the potential risk associated with the MDR Salmonella strains circulating along the food chain. Hence, epidemiological surveillance supported by molecular typing could be a very useful tool to prevent transmission of resistant Salmonella from food to humans, in line with the One Health approach.

Antibiotic Susceptibility Profile and Tetracycline Resistance Genes Detection in Salmonella spp. Strains Isolated from Animals and Food.

Salmonella spp. is among the leading causes of foodborne infections in humans and a large number of animals. Salmonella spp. is a pathogen involved in the dissemination of antimicrobial resistance because it can accumulate antibiotic resistance genes (ARGs). In this study, the antibiotic resistance profile to 15 antibiotics, belonging to six different classes, of 60 strains of Salmonella spp. collected from pets, farm animals, wildlife, and food in Sicily (Italy) was investigated by the Kirby-Bauer method. Given that almost 33.3% of the Salmonella spp. strains were resistant to tetracycline, Real-Time PCR analysis was applied on all the 60 strains to detect the presence of eight selected tet resistance genes. Besides, the presence of the int1 gene, related to the horizontal gene transfer among bacteria, was also investigated in all the strains by Real-Time PCR analysis. Our data showed that 56% of the isolated strains harbored one or more tet resistance genes and that these strains were most frequently isolated from animals living in close contact with humans. Concerning int1, 17 strains (28.3%) harbored this genetic element and eight of these simultaneously contained tet genes. The results of this study highlight the importance of using a molecular approach to detect resistance genetic determinants, whose spread can increase the diffusion of multidrug-resistant strains. Besides, the study of zoonotic bacteria such as Salmonella spp. which significantly contribute to ARGs dissemination should always follow a One Health approach that considers the health of humans, animals, and the environment to be closely related.

Trueperella pyogenes Isolates from Livestock and European Bison (Bison bonasus) as a Reservoir of Tetracycline Resistance Determinants.

Determinants of tetracycline resistance in Trueperella pyogenes are still poorly known. In this study, resistance to tetracycline was investigated in 114 T. pyogenes isolates from livestock and European bison. Tetracycline minimum inhibitory concentration (MIC) was evaluated by a microdilution method, and tetracycline resistance genes were detected by PCR. To determine variants of tetW and their linkage with mobile elements, sequencing analysis was performed. Among the studied isolates, 43.0% were tetracycline resistant (MIC ≥ 8 µg/mL). The highest MIC90 of tetracycline (32 µg/mL) was noted in bovine and European bison isolates. The most prevalent determinant of tetracycline resistance was tetW (in 40.4% of isolates), while tetA(33) was detected only in 8.8% of isolates. Four variants of tetW (tetW-1, tetW-2, tetW-3, tetW-4) were recognized. The tetW-3 variant was the most frequent and was linked to the ATE-1 transposon. The tetW-2 variant, found in a swine isolate, was not previously reported in T. pyogenes. This is the first report on determinants of tetracycline resistance in T. pyogenes isolates from European bison. These findings highlight that wild animals, including wild ruminants not treated with antimicrobials, can be a reservoir of tetracycline-resistant bacteria carrying resistance determinants, which may be easily spread among pathogenic and environmental microorganisms.

Dysregulated TET Family Genes and Aberrant 5mC Oxidation in Breast Cancer: Causes and Consequences.

DNA methylation (5-methylcytosine, 5mC) was once viewed as a stable epigenetic modification until Rao and colleagues identified Ten-eleven translocation 1 (TET1) as the first 5mC dioxygenase in 2009. TET family genes (including TET1, TET2, and TET3) encode proteins that can catalyze 5mC oxidation and consequently modulate DNA methylation, not only regulating embryonic development and cellular differentiation, but also playing critical roles in various physiological and pathophysiological processes. Soon after the discovery of TET family 5mC dioxygenases, aberrant 5mC oxidation and dysregulation of TET family genes have been reported in breast cancer as well as other malignancies. The impacts of aberrant 5mC oxidation and dysregulated TET family genes on the different aspects (so-called cancer hallmarks) of breast cancer have also been extensively investigated in the past decade. In this review, we summarize current understanding of the causes and consequences of aberrant 5mC oxidation in the pathogenesis of breast cancer. The challenges and future perspectives of this field are also discussed.

Occurrence of tet(O/M/O) Mosaic Gene in Tetracycline-Resistant Campylobacter.

Campylobacter is one of the most important microorganisms responsible for foodborne diseases in the EU. In this study, we investigated resistance to tetracycline in 139 Campylobacter jejuni and Campylobacter coli samples isolated from human clinical cases. From these, 110 were resistant to tetracycline, with MIC (minimal inhibitory concentration) varying in a range of 1 to >512 µg/mL, and 109 (78.4%) carried tet(O), a gene that confers resistance to tetracycline through the expression of a protein that confers protection to the ribosome. Amongst the tetracycline-resistant isolates, one C. jejuni (HCC30) was the only tet(O)-negative sample, presenting an MIC of 256 µg/mL. Instead, the mosaic gene tet(O/M/O) was found in HCC30 and, as far as we know, this is the first description of this chimeric gene originating from homologous recombination between tet(O) and tet(M). The previously described mosaic gene tet(O/32/O), also found in Campylobacter, presents a chimeric structure very similar to that of tet(O/M/O), affecting domains II and III of encoded proteins distantly related to the elongation factor G (EF-G). The tet(O/M/O) mosaic gene has been found in nucleotide databases in several genomes of Campylobacter isolated from different origins, indicating its frequent acquisition, even though it can be undetected through screening by PCR with specific tet(O) primers. In this work, we address the improvement of classical PCR to efficiently diagnose the most prevalent tetracycline resistance determinants in Campylobacter, including tet(O/M/O), which should be taken into account in the optimization of campylobacteriosis treatments.

Detection of multi-drug resistant (MDR) Escherichia coli and tet gene prevalence at a pig farm in Kupang , Indonesia.

OBJECTIVE: The purpose of this study was to detect the incidence of multi-drug resistant (MDR) and the spread of tet genes that encode tetracycline (TE) resistance in E. coli in pig farms in the city of Kupang, Indonesia. MATERIALS AND METHODS: Samples of pig feces have been obtained from 96 pig farms in Kupang city, Indonesia. Escherichia coli bacteria were isolated and identified morphologically and biochemically, and finally confirmed by the API test. The disk diffusion method has been used to observe the antibiotic sensitivity effects and has been followed by observing resistant genes encoding TE resistance using the multiplex polymerase chain reaction (m-PCR) method to detect the presence of tet genes such as tet (A), tet (B), tet (C), tet (D), and tet (E), respectively. RESULTS: A total of 82 (85.4%) of E. coli isolates have been found in all pig feces samples obtained from 96 pig farms in Kupang city. This study has shown a high level of antibiotic resistance dominated by erythromycin (85.4%) and cephalothin (58.5%) and followed by several other antibiotics with a percentage below 34.1%. The prevalence of MDR E. coli was 57.3% by showing 39 different patterns. The most common pattern was showed by the Cephalothin-Colistin-Erythromycin pattern. The resistance of E. coli to TE appears to be related to the presence of tet (A) and tet (E) genes. CONCLUSION: This study has encouraged the need for public awareness (farmers) of the wise use of antibiotics in preventing the spread of resistant bacteria that can cause health problems in animals and humans.

Prevalence of Antibiotic-Resistant Escherichia coli in Drinking Water Sources in Hangzhou City.

This study investigated the distribution of antibiotic resistant Escherichia coli (E. coli) and examined the possible relationship between water quality parameters and antibiotic resistance from two different drinking water sources (the Qiantang River and the Dongtiao Stream) in Hangzhou city of China. E. coli isolates were tested for their susceptibility to 18 antibiotics. Most of the isolates were resistant to tetracycline (TE), followed by ampicillin (AM), piperacillin (PIP), trimethoprim/sulfamethoxazole (SXT), and chloramphenicol (C). The antibiotic resistance rate of E. coli isolates from two water sources was similar; For E. coli isolates from the Qiantang River, their antibiotic resistance rates decreased from up- to downstream. Seasonally, the dry and wet season had little impact on antibiotic resistance. Spearman's rank correlation revealed significant correlation between resistance to TE and phenicols or ciprofloxacin (CIP), as well as quinolones (ciprofloxacin and levofloxacin) and cephalosporins or gentamicin (GM). Pearson's chi-square tests found certain water parameters such as nutrient concentration were strongly associated with resistance to some of the antibiotics. In addition, tet genes were detected from all 82 TE-resistant E. coli isolates, and most of the isolates (81.87%) contained multiple tet genes, which displayed 14 different combinations. Collectively, this study provided baseline data on antibiotic resistance of drinking water sources in Hangzhou city, which indicates drinking water sources could be the reservoir of antibiotic resistance, potentially presenting a public health risk.

Tetracycline Resistance Patterns of Lactobacillus buchneri Group Strains.

Lactobacilli are applied as starter cultures for controlled fermentation in the production of food and feed. Among other lactobacilli, members of the Lactobacillus buchneri group are used in fermented milk, wine, and silage. Most of the L. buchneri species used for the manufacturing of food or feed are already on the list for qualified presumption of safety status and are recommended as biological agents by the European Food Safety Authority. Consequently, new strains intended as food or feed additives do not require any additional safety check than confirming the absence of transferable antibiotic resistance determinants. Of these determinants, tetracycline resistance genes are especially predominant in lactobacilli. Within this study, a total of 128 strains belonging to the L. buchneri group ( L. buchneri , L. diolivorans , L. farraginis , L. hilgardii , L. kefiri , L. kisonensis , L. otakiensis , L. parabuchneri , L. parafarraginis , L. parakefiri , L. rapi , L. senioris , and L. sunkii ) were examined for their susceptibility to tetracycline. Tetracycline MICs were assessed by the broth microdilution method according to ISO 10932/IDF 223. Subsequently, the presence of tetracycline resistance genes was investigated by using PCR. In addition, selected strains were tested for a broader range of tetracycline resistance genes by using a microarray technique. Applying the tetracycline cutoff values defined by European Food Safety Authority for heterofermentative and obligately homofermentative lactobacilli, 96.9% of the strains would have been categorized as tetracycline resistant. However, none of the tested tetracycline resistance genes could be detected by PCR or microarray analysis. Furthermore, the MIC distribution of all strains was unimodal and at the high end of the tested tetracycline concentration range (4 to 256 µg/ml). Thus, these data suggest that tetracycline resistance in the L. buchneri group strains is intrinsic, which complies with the requirements defined in the qualified presumption of safety outline.

Combination of antibiotics suppressed the increase of a part of ARGs in fecal microorganism of weaned pigs.

The presence of antibiotic resistance genes (ARGs) is one of the most important public health concerns. Six tetracycline resistance genes (TRGs-tetA, tetC, tetL, tetO, tetW, and tetX) were quantified using real-time quantitative polymerase chain reaction (qPCR) in the fecal microorganisms of weaned pigs. Two hundred 35-day-old weaned pigs were fed different dietary antibiotics for 28 days: (1) no antibiotic as the control treatment (CT); (2) chlortetracycline, bacitracin zinc and colistin sulfate (CBC); (3) bacitracin zinc and colistin sulfate (BC); and (4) chlortetracycline (CTC). The detection frequencies (DFs) of tetC, tetL, and tetW were 100 %; and the DFs of tetA, tetD, tetM, tetO, and tetX were 65 %. The relative abundances (tet/16S rRNA gene copy numbers) of six tet genes (tetA, tetC, tetL, tetO, tetW and tetX) were between 1.5 × 10(-4) and 2.0 × 10(-1). In the group CTC, the relative abundances of tetC (P < 0.01), tetL (P < 0.01), tetO (P < 0.05), tetW (P < 0.01), and tetX (P < 0.01) were greater than those of the group CT. Compared with the group CTC, the relative abundances of tetC (P < 0.01), tetL (P < 0.01), and tetW (P < 0.01) were decreased in the CBC and BC groups. These results indicate that a combination of different antibiotics suppressed the abundance increase of a part of tet genes, which suggests that a combination of antibiotics produces multiple selection pressures on fecal microorganism of pigs.

Occurrence and diversity of tetracycline resistance genes in the agricultural soils of South Korea.

Reports on the occurrence and diversity of antibiotic-resistant bacteria and genes, which are considered to be emerging pollutants worldwide, have, to date, not been published on South Korean agricultural soils. This is the first study to investigate the persistence of tetracycline (oxytetracycline, tetracycline, and chlortetracycline)-resistant bacterial community and genes in natural and long-term fertilized (NPK, pig, and cattle manure composts) agricultural soils in South Korea. The results showed that oxytetracycline and chlortetracycline could be the dominant residues in animal manures; regular fertilization of manures, particularly pig manures, may be the prime cause for the spread and abundance of tetracycline resistance in South Korean agricultural soils. Both the country's natural and agricultural soils are reservoirs of antibiotic-resistant species. Of the 113 tetracycline-resistant isolates identified (19 typical bacterial genera and 36 distinct species), approximately 40 to 99 % belonged to Gram-positive bacteria and Bacillus constituted the predominant genera. Of the 24 tet genes targeted, tetG, tetH, tetK, tetY, tetO, tetS, tetW, and tetQ were detected in all soil samples, highlighting their predominance and robust adaptability in soils. Meanwhile, it is suggested that tetC, tetE, tetZ, tetM, tetT, and tetP(B) are the common residues in pig manures, and furthermore, the treatment of soils with pig manures may wield a different impact on the tet gene resistome in agricultural soils. This study thus highlights the necessity for regulating the usage of tetracyclines in South Korean animal farming. This must be followed by proper monitoring of the subsequent usage of animal manures especially that derived from pig farms located in agricultural soils.

Epigenetic regulation of hematopoietic stem cell development.

Hematopoietic stem cells (HSCs) are multipotent self-renewing precursors with the capacity to differentiate into all adult blood cell lineages. HSC development is a highly orchestrated process regulated by multiple transcription factors and signaling pathways. Emerging evidence suggests that epigenetic regulation is an additional essential component of HSC development. Powerful genetic and imaging approaches, combined with conservation of mammalian programs, have made zebrafish a prominent model for the study of HSC production. This chapter summarizes approaches that have been used to identify epigenetic regulators of HSC development in zebrafish and highlights additional strategies that are likely to facilitate progress in this promising field.

Minimal role of base excision repair in TET-induced global DNA demethylation in HEK293T cells.

Oxidation of 5-methylcytosine by TET family proteins can induce DNA replication-dependent (passive) DNA demethylation and base excision repair (BER)-based (active) DNA demethylation. The balance of active vs. passive TET-induced demethylation remains incompletely determined. In the context of large scale DNA demethylation, active demethylation may require massive induction of the DNA repair machinery and thus compromise genome stability. To study this issue, we constructed a tetracycline-controlled TET-induced global DNA demethylation system in HEK293T cells. Upon TET overexpression, we observed induction of DNA damage and activation of a DNA damage response; however, BER genes are not upregulated to promote DNA repair. Depletion of TDG (thymine DNA glycosylase) or APEX1 (apurinic/apyrimidinic endonuclease 1), two key BER enzymes, enhances rather than impairs global DNA demethylation, which can be explained by stimulated proliferation. By contrast, growth arrest dramatically blocks TET-induced global DNA demethylation. Thus, in the context of TET-induction in HEK293T cells, the DNA replication-dependent passive mechanism functions as the predominant pathway for global DNA demethylation. In the same context, BER-based active demethylation is markedly restricted by limited BER upregulation, thus potentially preventing a disastrous DNA damage response to extensive active DNA demethylation.