Short-term cold stress can reduce the abundance of antibiotic resistance genes in the cecum and feces in a pig model

Gut microbiome and metabolome to discover pathogenic bacteria and probiotics in ankylosing spondylitis

Objective

Previous research has partially revealed distinct gut microbiota in ankylosing spondylitis (AS). In this study, we performed non-targeted fecal metabolomics in AS in order to discover the microbiome-metabolome interface in AS. Based on prospective cohort studies, we further explored the impact of the tumor necrosis factor inhibitor (TNFi) on the gut microbiota and metabolites in AS.

Methods

To further understand the gut microbiota and metabolites in AS, along with the influence of TNFi, we initiated a prospective cohort study. Fecal samples were collected from 29 patients with AS before and after TNFi therapy and 31 healthy controls. Metagenomic and metabolomic experiments were performed on the fecal samples; moreover, validation experiments were conducted based on the association between the microbiota and metabolites.

Results

A total of 7,703 species were annotated using the metagenomic sequencing system and by profiling the microbial community taxonomic composition, while 50,046 metabolites were identified using metabolite profiling. Differential microbials and metabolites were discovered between patients with AS and healthy controls. Moreover, TNFi was confirmed to partially restore the gut microbiota and the metabolites. Multi-omics analysis of the microbiota and metabolites was performed to determine the associations between the differential microbes and metabolites, identifying compounds such as oxypurinol and biotin, which were correlated with the inhibition of the pathogenic bacteria Ruminococcus gnavus and the promotion of the probiotic bacteria Bacteroides uniformis. Through experimental studies, the relationship between microbes and metabolites was further confirmed, and the impact of these two types of microbes on the enterocytes and the inflammatory cytokine interleukin-18 (IL-18) was explored.

Conclusion

In summary, multi-omics exploration elucidated the impact of TNFi on the gut microbiota and metabolites and proposed a novel therapeutic perspective: supplementation of compounds to inhibit potential pathogenic bacteria and to promote potential probiotics, therefore controlling inflammation in AS.

In vitro assessment of the bacterial stress response and resistance evolution during multidrug-resistant bacterial invasion of the Xenopus tropicalis intestinal tract under typical stresses

The intestinal microbiome might be both a sink and source of resistance genes (RGs). To investigate the impact of environmental stress on the disturbance of exogenous multidrug-resistant bacteria (mARB) within the indigenous microbiome and proliferation of RGs, an intestinal conjugative system was established to simulate the invasion of mARB into the intestinal microbiota in vitro. Oxytetracycline (OTC) and heavy metals (Zn, Cu, Pb), commonly encountered in aquaculture, were selected as typical stresses for investigation. Adenosine 5'-triphosphate (ATP), hydroxyl radical (OH·-) and extracellular polymeric substance (EPS) were measured to investigate their influence on the acceptance of RGs by intestinal bacteria. The results showed that the transfer and diffusion of RGs under typical combined stressors were greater than those under a single stressor. Combined effect of OTC and heavy metals (Zn, Cu) significantly increased the activity and extracellular EPS content of bacteria in the intestinal conjugative system, increasing intI3 and RG abundance. OTC induced a notable inhibitory response in Citrobacter and exerted the proportion of Citrobacter and Carnobacterium in microbiota. The introduction of stressors stimulates the proliferation and dissemination of RGs within the intestinal environment. These results enhance our comprehension of the typical stresses effect on the RGs dispersal in the intestine.

Effects of Neolamarckia cadamba leaves extract on microbial community and antibiotic resistance genes in cecal contents and feces of broilers challenged with lipopolysaccharides

The effects of Neolamarckia cadamba leaves extract (NCLE), with effective ingredients of flavonoids, on antibiotic resistance genes (ARGs) and relevant microorganisms in cecal contents and feces of broilers treated with or without lipopolysaccharide stimulation (LPS) were investigated. LPS stimulation increased (P < 0.05) the relative abundance of ARGs and mobile genetic elements (MGEs), such as tet(W/N/W), APH(3')-IIIa, ErmB, tet (44), ANT (6)-Ia, tet(O), tet (32), Vang_ACT_CHL, myrA, ANT (6)-Ib, IncQ1, tniB, and rep2 in cecal contents. However, the difference disappeared (P > 0.05) when NCLE was added at the same time. These differential ARGs and MGEs were mainly correlated (P < 0.01) with Clostridiales bacterium, Lachnospiraceae bacterium, and Candidatus Woodwardibium gallinarum. These species increased in LPS-stimulated broilers and decreased when NCLE was applied at the same time. In feces, LPS stimulation decreased (P < 0.05) the relative abundance of tet(Q), adeF, ErmF, Mef(En2), OXA-347, tet (40), npmA, tmrB, CfxA3, and ISCrsp1, while the LPS + NCLE treated group showed no significant effect (P > 0.05) on these ARGs. These differential ARGs and MGEs in feces were mainly correlated (P < 0.01) with Clostridiales bacterium, Pseudoflavonifractor sp. An184, Flavonifractor sp. An10, Ruminococcaceae bacterium, etc. These species increased in LPS-stimulated broilers and increased when NCLE was applied at the same time. In conclusion, LPS stimulation and NCLE influenced microbial communities and associated ARGs in both cecal contents and feces of broilers. NCLE alleviated the change of ARGs and MGEs in LPS-induced broilers by maintaining the microbial balance.IMPORTANCEAntibiotics showed a positive effect on gut health regulation and growth performance improvement in livestock breeding, but the antimicrobial resistance threat and environment pollution problem are increasingly severe with antibiotics abuse. As alternatives, plant extract containing bioactive substances are increasingly used to improve immunity and promote productivity. However, little is known about their effects on diversity and abundance of ARGs. Here, we investigated the effects of NCLE, with effective ingredients of flavonoids, on ARGs and relevant microorganisms in cecal contents and feces of broilers treated with or without lipopolysaccharide stimulation. We found that NCLE reduced the abundance of ARGs in cecal contents of lipopolysaccharide-induced broilers by maintaining the microbial balance. This study provides a comprehensive view of cecal and fecal microbial community, ARGs, and MGEs of broiler following LPS stimulation and NCLE treatment. It might be used to understand and control ARGs dissemination in livestock production.

Methionine influences the profile of intestinal antibiotic resistome through inhibiting the growth of Escherichia coli

Antibiotic resistance genes (ARGs) are a new type of environmental pollutant. However, studies have mainly focused on the distribution characteristics of ARGs in the livestock environment, lacking of studies on the composition of ARGs in the intestinal tract of animals and the effect of nutrients on intestinal ARGs and microbial communities. Reducing antimicrobial resistance and maintaining optimal animal health and performance are urgently needed. Methionine is an essential amino acid which plays a critical role in the growth and reproductive performance of animals. In this study, feeding experiment, in vitro fermentation and bacterial culture experiment were performed to explore the influence of methionine on the intestinal resistome of sows. We found that dietary 0.2 % methionine supplementation decreased the total abundance of intestinal ARGs, which was further confirmed by in vitro fecal microbial fermentation of sows. Metagenome binning analysis identified that Escherichia coli was the major ARG host, which carried 60-113 ARGs and 134-286 virulence factors, indicating that Escherichia coli in the pig intestine is not only a core ARG host, but also an important pathogen. In addition, we found that methionine supplementation inhibited the growth of Escherichia coli, indicating that dietary methionine may reduce the resistome risk in sow intestine by inhibiting core ARG hosts such as Escherichia coli. These findings reveal that dietary methionine application plays a critical role in intestinal antibiotic resistance, providing a new idea for preventing and controlling environmental pollution by antibiotic-resistant microbes.

Longitudinal metagenomic study reveals the dynamics of fecal antibiotic resistome in pigs throughout the lifetime

BACKGROUND

The dissemination of antibiotic resistance genes (ARGs) poses a substantial threat to environmental safety and human health. Herein, we present a longitudinal paired study across the swine lifetime from birth to market, coupled with metagenomic sequencing to explore the dynamics of ARGs and their health risk in the swine fecal microbiome.

RESULTS

We systematically characterized the composition and distribution of ARGs among the different growth stages. In total, 829 ARG subtypes belonging to 21 different ARG types were detected, in which tetracycline, aminoglycoside, and MLS were the most abundant types. Indeed, 134 core ARG subtypes were shared in all stages and displayed a growth stage-associated pattern. Furthermore, the correlation between ARGs, gut microbiota and mobile genetic elements (MGEs) revealed Escherichia coli represented the main carrier of ARGs. We also found that in most cases, the dominant ARGs could be transmitted to progeny piglets, suggesting the potential ARGs generation transmission. Finally, the evaluation of the antibiotic resistance threats provides us some early warning of those high health risk ARGs.

CONCLUSIONS

Collectively, this relatively more comprehensive study provides a primary overview of ARG profile in swine microbiome across the lifetime and highlights the health risk and the intergenerational spread of ARGs in pig farm.

Pet cats may shape the antibiotic resistome of their owner's gut and living environment

BACKGROUND

Companion animals can contribute to the physical and mental health of people and often live in very close association with their owners. However, the antibiotic resistome carried by companion animals and the impact they have on their owners and living environment remain unclear. In this study, we compared the ARG profiles of cats, humans, and their living environments using metagenomic analysis to identify the core ARGs in the cat and human gut and explore the potential impact of cats on ARGs in the human gut through the environment.

RESULTS

Results showed that the abundance of ARGs in the cat gut was significantly higher than that in the human gut (P < 0.0001), with aminoglycoside and tetracycline resistance genes being the dominant ARGs in the cat gut. There was no significant difference in the abundance of total ARGs in the guts of cat owners and non-owners (P > 0.05). However, the abundance of aminoglycoside resistance genes including APH(2'')-IIa and AAC(6')-Im was significantly higher in cat owners than that in non-cat owners (P < 0.001). Also, ARG abundance was positively correlated with the frequency of cat activity in the living environment. Enterobacteriaceae was the dominant ARG host co-occurring in the cat gut, human gut, and living environment.

CONCLUSIONS

Our results show that cats may shape the living environment resistome and thus the composition of some ARGs in the human gut, highlighting the importance of companion animal environment health. Video Abstract.

Genetic- and Fiber-Diet-Mediated Changes in Antibiotic Resistance Genes in Pig Colon Contents and Feces and Their Driving Factors

Comprehensive studies on the effects of genetics and fiber diets on antibiotic resistance genes (ARGs) remain scarce. In this study, we analyzed the profiles of ARGs in colonic contents and fecal samples of Taoyuan, Duroc, and Xiangcun pigs (n = 10) fed at different fiber levels. Through macrogenomic analysis, we identified a total of 850 unique types of ARGs and classified them into 111 drug resistance classes. The abundance of partially drug-resistant ARGs was higher in the colonic contents of local pig breeds under a large-scale farming model. ARGs were found to be widely distributed among a variety of bacteria, predominantly in the phyla Firmicutes, Proteobacteria, and Bacteroidetes. Fiber diets reduce the abundance of ARGs in colonic contents and feces, and mobile genetic elements (MGEs) and short-chain fatty acids (SCFAs) are important drivers in mediating the effect of fiber diets on the abundance of ARGs. In vitro fermentation experiments confirmed that butyric acid significantly reduced the abundance of ARGs. In summary, the results of this study enhanced our understanding of the distribution and composition of ARGs in the colon of different breeds of pigs and revealed that a fiber diet can reduce ARGs in feces through its Butyric acid, providing reference data for environmental safety.

The abundance and diversity of antibiotic resistance genes in layer chicken ceca is associated with farm enviroment

Industrialized layer chicken feedlots harbor complex environmental microbial communities that affect the enrichment and exchange of gut bacteria and antibiotic resistance genes (ARGs). However, the contribution of different environmental sources to the gut ARGs of layer chickens is not clear. Here, layer chicken gut and environmental samples (air, water, feed, cage, feather, maternal hen feces, uropygial glands) were collected during the early 3 month period before the laying of eggs, and the source and characteristics of the gut microorganisms and ARGs were analyzed by performing 16S rRNA and metagenomic sequencing. The results showed that the abundances of Bacteroidetes and Actinobacteria in cecum of layer chickens gradually increased, while that of Proteobacteria decreased with age, and the number and relative abundance of ARGs decreased significantly with age. On day 5, 57% of the layer chicken cecal ARGs were from feather samples, and 30% were from cage samples. Subsequently, the contribution of cage ARGs became progressively more prominent over time. At days 30 and 57, the contribution of cage ARGs to the chick cecal ARGs reached 63.3 and 69.5%, respectively. The bacterial community composition (especially the abundances of Klebsiella pneumoniae and Escherichia coli) was the major factor impacting the ARG profile. K. pneumoniae and E. coli were mainly transmitted from feathers to the layer chicken cecum, and the contribution rates were 32 and 3.4%, respectively. In addition, we observed the transmission of ARG-carrying bacteria (Bacteroides fragilis) from the cage to the gut, with a contribution rate of 11.5%. It is noteworthy that B. fragilis is an opportunistic pathogen that may cause diarrhea in laying hens. These results can provide reference data for the healthy breeding of layer chickens and the prevention and control of ARG pollution.

Does increasing the organic fertilizer application rate always boost the antibiotic resistance level in agricultural soils?

The amendment of organic fertilizer derived from livestock manure or biosolids is a significant driver of increasing antibiotic resistance in agricultural soils; however, it remains unclear whether increasing organic fertilizer application rates consistently enhances soil antibiotic resistance levels. Herein, we collected soils with long-term amendment with three types of organic fertilizers at four application rates (15, 30, 45, and 60 t/ha/y) and found that the higher the fertilization rate, the higher the antibiotic resistance gene (ARG) abundance. However, when the fertilization rate exceeded 45 t/ha/y, the ARG abundance ceased to significantly increase. Moreover, the soil ARG abundance was positively correlated with total nitrogen (TN) content and bacterial abundance, especially Firmicutes, and negatively affected by pH and bacterial diversity. Soil TN/bacterial abundance and pH/bacterial diversity reached maximum and minimum values at the 45 t/ha/y fertilization rate, respectively. Meanwhile, at this fertilization rate, Firmicutes enrichment peaked. Therefore, an organic fertilization rate of 45 t/ha/y appeared to represent the threshold for soil antibiotic resistance in this study. The underlying mechanism for this threshold was closely related to soil TN, pH, bacterial abundance, and diversity. Taken together, the findings of this study advance the current understanding regarding the soil resistome under different fertilization rates, while also providing novel insights into organic fertilizer management in agricultural practices.

Metagenomics analysis reveals potential pathways and drivers of piglet gut phage-mediated transfer of ARGs

The growing prevalence of antibiotic-resistant pathogens has led to a better understanding of the underlying processes that lead to this expansion. Intensive pig farms are considered one of the hotspots for antibiotic resistance gene (ARG) transmission. Phages, as important mobile carriers of ARGs, are widespread in the animal intestine. However, our understanding of phage-associated ARGs in the pig intestine and their underlying drivers is limited. Here, metagenomic sequencing and analysis of viral DNA and total DNA of different intestinal (ileum, cecum and feces) contents in healthy piglets and piglets with diarrhea were separately conducted. We found that phages in piglet ceca are the main repository for ARGs and mobile genetic element (MGE) genes. Phage-associated MGEs are important factors affecting the maintenance and transfer of ARGs. Interestingly, the colocalization of ARGs and MGE genes in piglet gut phages does not appear to be randomly selected but rather related to a specific phage host (Streptococcus). In addition, in the feces of piglets with diarrhea, the abundance of phages carrying ARGs and MGE genes was significantly increased, as was the diversity of polyvalent phages (phages with broad host ranges), which would facilitate the transfection and wider distribution of ARGs in the bacterial community. Moreover, the predicted host spectrum of polyvalent phages in diarrheal feces tended to be potential enteropathogenic genera, which greatly increased the risk of enteropathogens acquiring ARGs. Notably, we also found ARG-homologous genes in the sequences of piglet intestinal mimiviruses, suggesting that the piglet intestinal mimiviruses are a potential repository of ARGs. In conclusion, this study greatly expands our knowledge of the piglet gut microbiome, revealing the underlying mechanisms of maintenance and dissemination of piglet gut ARGs and providing a reference for the prevention and control of ARG pollution in animal husbandry.

Removal of antibiotic resistance genes during livestock wastewater treatment processes: Review and prospects

Antibiotic resistance genes (ARGs) are emerging pollutants that have received extensive attention. Many different types of ARGs exist in livestock wastewater. If not effectively treated, they can threaten animal production, public health and the ecological safety of the surrounding environment. To address the high risk of livestock wastewater contamination by ARGs, the effects of different wastewater treatment processes on ARGs and their influencing factors and mechanisms are reviewed herein. Additionally, the current problems associated with removal of ARGs are discussed, and future research is proposed.

The fate of antibiotic resistance genes and their association with bacterial and archaeal communities during advanced treatment of pig farm wastewater

Advanced wastewater treatment plants are widely used in most large-scale pig farms in southern China. However, the fate of antibiotic resistance genes (ARGs) and their association with bacterial and archaeal communities during advanced wastewater treatment remain unclear. In this study, the profiles of ARGs in typical advanced wastewater treatment plants were surveyed using metagenomic analysis. The results showed that 279- 326 different subtypes of ARGs were detected in raw wastewater, with a total abundance of 5.98 ± 0.48 copies per bacterial cell. During the advanced wastewater treatment, the abundance and number of ARGs were significantly reduced. Microbial communities (bacteria and archaea) contributed the most to the variation in ARG abundance and composition (PCA axis_1), accounting for 10.8 % and 15.7 %, respectively, followed by mobile genetic elements (MGEs) and physicochemical factors. Special attention should be given to potential pathogenic bacteria such as Escherichia, Streptococcus, Enterococcus and Staphylococcus and archaea such as Methanocorpusculum, Candidatus Methanoplasma and Candidatus Methanomethylophilus, which were important potential ARG hosts. Bacterial communities may indirectly affect ARG variation by affecting archaeal communities. These findings indicated that ARG levels in pig farm wastewater can be effectively reduced during advanced treatment and highlighted the important role played by archaea, which should not be ignored.

Risk assessment of three sheep stocking modes via identification of bacterial genomes carrying antibiotic resistance genes and virulence factor genes

In order to protect the prairie ecological environment, intensive farming has become a prevalent method of sheep stocking. However, the link between captivity stocking mode and ecological risk of sheep feces is still poorly understood. In this study, metagenomics was used to identify the environmental risk of sheep feces among three stocking modes. Our results showed that captivity mode (C) elevated antibiotic resistance in feces, with the abundance of antibiotic resistance genes (ARGs) (5.381 copies/cell) higher than that of half-pen stocking (Fh) (1.093 copies/cell) and grazing mode (Fr) (0.315 copies/cell) (Duncan's test, P < 0.05). Virulence factor genes (VFGs) analysis showed offensive virulence factors had the highest abundance in captivity feces (C: 3.826 copies/cell, Fh: 0.342 copies/cell, Fr: 0.163 copies/cell) (Duncan's test, P < 0.05). 15 metagenome-assembled genomes (MAGs) were identified as potential pathogenic antibiotic resistant bacteria (PARB) and revealed that Escherichia, Klebsiella may be the main host of ARGs and VFGs in sheep feces. Furthermore, the minimal inhibition concentrations (MIC) of tetracycline of E. coli in the captivity feces was 8.6 times and 4.7 times than that of grazing and half-pen stocking samples, respectively. The Non-metric multidimensional scaling (NMDS) revealed that high stocking density leads to feces causing increased harm to the environment. Although feces from sheep raised in captivity and half-pen stocking modes are easier to collect, they are more harmful to the environment and aerobic composting should be done before their application to farmland. This work provides a guideline for better control of the environmental risk of sheep feces from different stocking modes.

Sodium butyrate reduces ammonia production in the cecum of laying hens by regulating ammonia-producing bacteria

Sodium butyrate is a commonly used feed additive and can reduce ammonia (NH₃) emissions from laying hens, but the mechanism of this effect is unknown. In this study, the sodium butyrate and cecal content of Lohmann pink laying hens were measured, and in vitro fermentation experiments and NH₃-producing bacteria coculture experiments were carried out to explore the relationship between NH₃ emissions and its associated microbiota metabolism. Sodium butyrate was found to significantly reduce NH₃ emission from the cecal microbial fermentation of Lohmann pink laying hens (P < 0.05). The concentration of NO₃^--N in the fermentation broth of the sodium butyrate-supplemented group increased significantly, and the concentration of NH₄⁺-N decreased significantly (P < 0.05). Moreover, sodium butyrate significantly reduced the abundance of harmful bacteria and increased the abundance of beneficial bacteria in the cecum. The culturable NH₃-producing bacteria consisted mainly of Escherichia and Shigella, such as Escherichia fergusonii, Escherichia marmotae and Shigella flexnerii. Among them, E. fergusonii had the highest potential for NH₃ production. The coculture experiment showed that sodium butyrate can significantly downregulate the expression of the lpdA, sdaA, gcvP, gcvH and gcvT genes of E. fergusonii (P < 0.05), thus reducing the NH₃ emission produced by the bacteria during metabolism. In general, sodium butyrate regulated NH₃-producing bacteria to reduce NH₃ production in the cecum of laying hens. These results are of great significance for NH₃ emission reduction in the layer breeding industry and for future research.

Integrated Analysis of Transcriptome, microRNAs, and Chromatin Accessibility Revealed Potential Early B-Cell Factor1-Regulated Transcriptional Networks during the Early Development of Fetal Brown Adipose Tissues in Rabbits

In domestic mammals, cold stress decreases the survival rate of newborns and increases the cost of management. Brown adipose tissue (BAT) is the main thermogenic organ for cubs, and well-developed fetal BAT (FBAT) is beneficial for newborns to maintain core temperatures during the first several days of life. However, our knowledge of the epigenetic mechanisms during the early development of FBAT remains largely unknown. Rabbits (Oryctolagus cuniculus) are economically important domestic animals. In this study, a histological analysis shows that the tissue content, thermogenic capacity, and lipid content of FBAT dramatically increases from gestational day 21 (G21) to gestational day 24 (G24) in rabbits. RNA-seq, microRNA-seq (miRNA-seq), and the assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) show that many genes, miRNAs, and chromatin-accessible regions (referred to as peaks) were identified as significantly changed from G21 to G24, respectively. The upregulated genes from G21 to G24 were significantly enriched in the mitochondrial metabolism and thermogenesis-related signal pathways. The integrated analysis of transcriptome and chromatin accessibility reveals that the peaks in the promoters have a more regulatory effect than peaks in other genomic elements on the expression of their nearby genes in FBATs. The upregulated genes that are associated with increased chromatin accessibility in the promoter regions are involved in the energy metabolism-related signaling pathways. The genes that have a greater tendency to be regulated by miRNAs than the chromatin accessibility in gene promoters are involved in the apelin, insulin, and endocytosis signaling pathways. Furthermore, genome-wide transcription factor (TF) footprinting analysis identifies early B-cell factor1 (EBF1) as playing a key role during early FBAT development. The carbon metabolism, citrate cycle, and PPAR signaling pathways are significantly enriched by the predicted EBF1-regulated cascade TF-network. In conclusion, our work provides a framework for understanding epigenetics regulatory mechanisms underlying the early development of FBAT and identifies potential TF involved in the early development of FBAT in rabbits.

Metagenomic assembly reveals the circadian oscillations of the microbiome and antibiotic resistance genes in a model of laying hens

The increasing risks of antibiotic resistance genes (ARGs) in livestock feces have attracted global attention. However, how the rhythmic activity of ARGs changes in fecal microbiota remains largely unclear. In our study, we collected 52 fresh fecal samples every 6 h over 72 h from laying hens and characterized circadian oscillations of bacteria and ARGs using an approach based on assembled metagenome shotgun sequencing. We found that 14% of commensal bacterial taxonomic units fluctuated over 24 h. A total of 33 out of 281 ARGs and 17 of 574 mobile genetic elements (MGEs) featured rhythmic patterns in feces. lnuC and ANT(6)H-lb were the two most abundant ARGs with circadian oscillation identified from feces, and they increased during the day and decreased at night. Acetate, butyrate, propionate, and 78 out of 392 MetaCyc pathways relating to short-chain fatty acid (SCFA) metabolism featured circadian oscillations. Assessment of the above ARG-other element connections revealed that 17 ARGs presented strong correlations with 7 MGEs, and 2 SCFAs (acetate and propanoate) and bacterial species in feces. Structural equation model (SEM) analysis showed that ARGs were directly affected by microbial β-diversity and MGEs. These results showed a comprehensive map of ARGs over 24 h and revealed circadian oscillations of ARGs, which are influenced by key bacterial species, MGEs, and metabolites. Together, our findings advance comprehension of circadian oscillations of ARGs in the fecal microbiota and provide a reference for ARGs control and management.

Non-targeted Metabolomics Analysis Based on LC–MS to Assess the Effects of Different Cold Exposure Times on Piglets

Pigs are susceptible to low temperature conditions, and cold stress causes metabolic changes in the body to increase heat production as an adaption to adverse environments. To characterize and validate different metabolites in piglet livers at different cold exposure times, sixteen 30-day-old male weaned piglets with similar weights were randomly divided into four groups: the normal temperature group (24 ± 2°C, NT) and cold exposure (4 ± 2°C) 2-h group (CS2), 6-h group (CS6), and 12-h group (CS12). At the end of the experiment, the liver samples were analyzed using systemic non-targeted metabolomics. Eight known differentially abundant metabolites (farnesyl pyrophosphate, isocitrate, triethanolamine, phenylethylamine, deoxynosine, citric acid, maltotriose, and epinephrine) were observed between the CS groups and the control group in positive and negative ion modes. The eight main differentially abundant metabolites involved in seven metabolite classifications. Metabolic pathways and enrichment analyses revealed that the pathways involved three KEGG pathway classifications. Most of the pathways were related to amino acid or energy metabolism. Moreover, the metabolic pathways were not identical under different cold exposure times, with those following 2 and 6 h of cold exposure more related to carbohydrates and energy production and those following 12 h of cold exposure more related to the metabolism connected with epinephrine. Thus, under different cold exposure times, the metabolite profiles and metabolic pathways differed.

Abundance, diversity and diffusion of antibiotic resistance genes in cat feces and dog feces

The ARG profiles in pet feces, such as cat and dog feces, and their potential threat to environmental safety are still unclear. In this study, ARGs in 45 cat and 28 dog fecal samples were detected, and a diffusion experiment was performed to assess the risk of ARGs diffusion into the air. The results showed that the abundances of ARGs in cat feces and dog feces were high, and the abundance in dog feces (0.89 ± 0.17 copies/bacterial cell) was significantly higher than that in cat feces (0.46 ± 0.09 copies/bacterial cell) (P < 0.05). The bacterial community, especially Firmicutes and Desulfobacterota in cat feces, and Proteobacteria in dog feces, was the main factor affecting the variation in the ARG profiles, contributing to 31.6% and 32.4% of the variation in cat feces and dog feces, respectively. Physicochemical factors (especially NH₄⁺-N) and age also indirectly affected the variation in the ARG profiles by affecting the bacterial community. In addition, the ARGs in cat feces and dog feces diffused into the air, but there was no evidence that this diffusion posed a threat to environmental safety and human health. These results can provide reference data for healthy animal breeding and the prevention and control of ARG pollution.