Growth promotion and gut microbiota: insights from antibiotic use

Effects of adding antibiotics to an inactivated oil-adjuvant avian influenza vaccine on vaccine characteristics and chick health

During poultry immunization, antibiotics are typically added to inactivated oil-adjuvant avian influenza (AI) vaccines. Here, we evaluated the effects of adding ceftiofur, a third-generation cephalosporin, to an AI vaccine on vaccine stability and structure and on chick growth, immune efficacy, blood concentrations, biochemical and immunological indices, and gut microbiota. The results demonstrated that neither aqueous ceftiofur sodium nor ceftiofur hydrochloride oil emulsion formed a stable mixture with the vaccine. Adding ceftiofur formulations, particularly ceftiofur hydrochloride, at >4% significantly destabilized the vaccine's water-in-oil structures. Adding ceftiofur also increased vaccine malabsorption at the injection site; specifically, adding ceftiofur hydrochloride reduced H5N8 and H7N9 antibody titers after the first immunization (P < 0.05) and H7N9 antibody titers after the second immunization (P < 0.01). Serum drug concentrations did not differ significantly between the groups with ceftiofur sodium and hydrochloride addition. Ceftiofur addition increased postvaccination chick weight loss; compared with the vaccine alone, ceftiofur sodium-vaccine mixture increased chick weight significantly (P < 0.05). Ceftiofur addition also increased stress indices and reduced antioxidant capacity significantly (P < 0.05 or P < 0.01). Vaccination-related immune stress reduced gut microbiota diversity in chicks; ceftiofur addition reversed this change. AI vaccine immunization significantly reduced the relative abundance of Lactobacillus and Muribaculaceae but significantly increased that of Bacteroides and Eubacterium coprostanoligenes group. Ceftiofur addition restored the gut microbiota structure; in particular, ceftiofur hydrochloride addition significantly increased the abundance of the harmful gut microbes Escherichia-Shigella and Enterococcus, whereas ceftiofur sodium addition significantly reduced it. The changes in gut microbiota led to alterations in metabolic pathways related to membrane transport, amino acids, and carbohydrates. In conclusion, adding ceftiofur to the AI vaccine had positive effects on chick growth and gut microbiota modulation; however, different antibiotic concentrations and formulations may disrupt vaccine structure, possibly affecting vaccine safety and immunization efficacy. Thus, the addition of antibiotics to oil-adjuvant vaccines is associated with a risk of immunization failure and should be applied to poultry with caution.

Sub-chronically exposing zebrafish to environmental levels of methomyl induces dysbiosis and dysfunction of the gut microbiota

The widespread use of carbamate pesticides has led to numerous environmental and health concerns, including water contamination and perturbation of endocrine homeostasis among organisms. However, there remains a paucity of research elucidating the specific effects of methomyl on gut microbial composition and physiological functions. This study aimed to investigate the intricate relationship between changes in zebrafish bacterial communities and intestinal function after 56 days of sub-chronic methomyl exposure at environmentally relevant concentrations (0, 0.05, 0.10, and 0.20 mg/L). Our findings reveal significant methomyl-induced morphological changes in zebrafish intestines, characterized by villi shortening and breakage. Notably, methomyl exposure down-regulated nutrient and energy metabolism, and drug metabolism at 0.05-0.10 mg/L, while up-regulating cortisol, inflammation-related genes, and apoptotic markers at 0.20 mg/L. These manifestations indicate physiological stress imposition and disruption of gut microbiota equilibrium, impacting metabolic processes and instigating low-grade inflammatory responses and apoptotic cascades. Importantly, changes in intestinal function significantly correlated with shifts in specific bacterial taxa abundance, including Shewanella, Rubrobacter, Acinetobacter, Bacillus, Luteolibacter, Nocardia, Defluviimonas, and Bacteroides genus. In summary, our study underscores the potential adverse effects of environmental methomyl exposure on aquatic organisms, emphasizing the necessity for further research to mitigate its repercussions on environmental health and ecosystem stability.

In vivo analysis the effect of antibiotic growth promoters (AGPs), Oxytetracycline di-hydrate and Tylosin phosphate on the intestinal microflora in broiler chicken

Abstract The study was aimed to analyse the effects of antibiotic growth promoters (AGPs), Oxytetracycline di-hydrate and Tylosin phosphate on the intestinal microflora in broiler chicken. The AGPs were provided in different concentrations solely or in combinations for 42 days of rearing. Faecal samples were collected from the intestine (duodenum, jejunum and caeca) of broiler chicken on 14th, 28th and 42nd days of trial. Samples were cultured on different selective medium and bacterial identification was performed by different biochemical and molecular diagnostic tools. Results showed a significant effect of AGPs on the growth of pathogenic microorganisms such as Escherichia coli and Clostridium perfringens in the intestine. Interestingly, an impaired growth was observed for both bacterium showing a significant effect (P<0.05) of AGPs on E. coli and C. perfringens on day 14th, 28th, and 42nd. This effect was observed solely and in combination while using AGPs. Data further showed that the effect was more prominent in combination and with an increase concentration of AGPs. Remarkably, no impairment was seen on the growth of L. reuteri at different sites of intestine and duration (14th, 28th, and 42nd days). The results showed that the use of AGPs in diet has no harmful effect on beneficial bacteria, however, an impaired growth was seen on the harmful bacteria. It is suggested that a combination of AGPs (OXY-1.0+TP-0.5) is economical and have no harmful effect on the broiler chicken. The use of AGPs in a recommended dose and for a specific period of time are safe to use in poultry both as growth promoter and for the prevention of diseases.

Multi-Omics Analysis Reveals the Gut Microbiota Characteristics of Diarrheal Piglets Treated with Gentamicin

The involvement of alterations in gut microbiota composition due to the use of antibiotics has been widely observed. However, a clear picture of the influences of gentamicin, which is employed for the treatment of bacterial diarrhea in animal production, are largely unknown. Here, we addressed this problem using piglet models susceptible to enterotoxigenic Escherichia coli (ETEC) F4, which were treated with gentamicin. Gentamicin significantly alleviated diarrhea and intestinal injury. Through 16s RNS sequencing, it was found that gentamicin increased species richness but decreased community evenness. Additionally, clear clustering was observed between the gentamicin-treated group and the other groups. More importantly, with the establishment of a completely different microbial structure, a novel metabolite composition profile was formed. KEGG database annotation revealed that arachidonic acid metabolism and vancomycin resistance were the most significantly downregulated and upregulated pathways after gentamicin treatment, respectively. Meanwhile, we identified seven possible targets of gentamicin closely related to these two functional pathways through a comprehensive analysis. Taken together, these findings demonstrate that gentamicin therapy for diarrhea is associated with the downregulation of arachidonic acid metabolism. During this process, intestinal microbiota dysbiosis is induced, leading to increased levels of the vancomycin resistance pathway. An improved understanding of the roles of these processes will advance the conception and realization of new therapeutic and preventive strategies.

Seaweed polysaccharide relieves hexavalent chromium-induced gut microbial homeostasis

Heavy metals released in the environment pose a huge threat to soil and water quality, food safety and public health. Additionally, humans and other mammals may also be directly exposed to heavy metals or exposed to heavy metals through the food chain, which seriously threatens the health of animals and humans. Chromium, especially hexavalent chromium [Cr (VI)], as a common heavy metal, has been shown to cause serious environmental pollution as well as intestinal damage. Thus, increasing research is devoted to finding drugs to mitigate the negative health effects of hexavalent chromium exposure. Seaweed polysaccharides have been demonstrated to have many pharmacological effects, but whether it can alleviate gut microbial dysbiosis caused by hexavalent chromium exposure has not been well characterized. Here, we hypothesized that seaweed polysaccharides could alleviate hexavalent chromium exposure-induced poor health in mice. Mice in Cr and seaweed polysaccharide treatment group was compulsively receive K2Cr2O7. At the end of the experiment, all mice were euthanized, and colon contents were collected for DNA sequencing analysis. Results showed that seaweed polysaccharide administration can restore the gut microbial dysbiosis and the reduction of gut microbial diversity caused by hexavalent chromium exposure in mice. Hexavalent chromium exposure also caused significant changes in the gut microbial composition of mice, including an increase in some pathogenic bacteria and a decrease in beneficial bacteria. However, seaweed polysaccharides administration could ameliorate the composition of gut microbiota. In conclusion, this study showed that seaweed polysaccharides can restore the negative effects of hexavalent chromium exposure in mice, including gut microbial dysbiosis. Meanwhile, this research also lays the foundation for the application of seaweed polysaccharides.

Antibacterial and anti-inflammatory activity of plant species used in traditional poultry ethnomedicine in Zimbabwe: A first step to developing alternatives to antibiotic poultry feed additives

ETHNOPHARMACOLOGICAL RELEVANCE

Global interest in phytogenic feed additives as alternatives to antibiotics in feed has been spurred by the banning of antibiotic growth promoters by several countries. Suitable plant extracts for development of phytogenic feed additives should have therapeutic value and should also be safe.

AIM OF STUDY

The aim of this study was to evaluate the antibacterial, antioxidant and anti-lipoxygenase activities as well as cytotoxicity of selected plant species used in poultry ethnomedicine in Zimbabwe.

METHODS

Antibacterial activity was determined against three ATCC strains (Staphylococcus aureus, Escherichia coli, Salmonella Enteritidis) and two clinical strains isolated from chickens (Escherichia coli and Salmonella Gallinarum) using a two-fold serial microdilution assay. Qualitative antibacterial bioautography was also carried out using the ATCC strains. Antioxidant activities of crude acetone and methanol extracts were determined using free radical scavenging assays whilst anti-lipoxygenase activity was evaluated using a ferrous oxidation-xylenol orange (FOX) assay. Cytotoxicity was evaluated using a tetrazolium-based colorimetric assay (MTT assay) on Vero monkey kidney cells.

RESULTS

Erythrina abyssinica had the best antibacterial activity against both ATCC strains and clinical strains with minimum inhibitory concentration (MIC) values ranging from 0.02 to 0.156 mg/ml. Aloe greatheadii, Adenia gummifera (leaves), Senna singueana and Aloe chabaudii had moderate activity against the poultry pathogens. Bioautography showed that all ten plant species have antibacterial activity against the tested microorganisms with E. abyssinica and S. singueana having prominent bands of inhibition against both Gram-negative and Gram-positive bacteria. The acetone extract of S. singueana and the methanol extract of Euphorbia matabelensis had the most powerful antioxidant activities with mean IC₅₀ values of 1.43 μg/ml and 1.31 μg/ml respectively in the ABTS assay which were comparable with those of the positive controls (ascorbic acid and trolox). Bobgunnia madagascariensis, A. chabaudii, E. abyssinica and Tridactyle bicaudata extracts had reasonable antioxidant activity. The S. singueana extract had the most potent anti-lipoxygenase activity with a mean IC₅₀ value of 1.72 μg/ml. The cytotoxicity results showed that only the acetone extracts of A. greatheadii and S. singueana were relatively safe at concentrations that were active against the tested microorganisms (selective index >1). Regarding anti-lipoxygenase activity, extracts of B. madagascariensis, S. singueana, T. bicaudata and E. matabelensis were more active than toxic (selective index >5) indicating anti-inflammatory potential.

CONCLUSIONS

This study showed that S. singueana had a cocktail of therapeutic activity and supports further investigation of this plant species for development of phytogenic poultry feed additives. Other plant species with noteworthy biological activities include B. madagascariensis, E. abyssinica, A. greatheadii, T. bicaudata and E. matabelensis.

First Report of Potentially Pathogenic Klebsiella pneumoniae from Serotype K2 in Mollusk Tegillarca granosa and Genetic Diversity of Klebsiella pneumoniae in 14 Species of Edible Aquatic Animals

Klebsiella pneumoniae can cause serious pneumonitis in humans. The bacterium is also the common causative agent of hospital-acquired multidrug-resistant (MDR) infections. Here we for the first time reported the genetic diversity of K. pneumoniae strains in 14 species of edible aquatic animals sampled in the summer of 2018 and 2019 in Shanghai, China. Virulence-related genes were present in the K. pneumoniae strains (n = 94), including the entB (98.9%), mrkD (85.1%), fimH (50.0%), and ybtA (14.9%) strains. Resistance to sulfamethoxazole-trimethoprim was the most prevalent (52.1%), followed by chloramphenicol (31.9%), and tetracycline (27.7%), among the strains, wherein 34.0% had MDR phenotypes. Meanwhile, most strains were tolerant to heavy metals Cu2+ (96.8%), Cr3+ (96.8%), Zn2+ (91.5%), Pb2+ (89.4%), and Hg2+ (81.9%). Remarkably, a higher abundance of the bacterium was found in bottom-dwelling aquatic animals, among which mollusk Tegillarca granosa contained K. pneumoniae 8-2-5-4 isolate from serotype K2 (ST-2026). Genome features of the potentially pathogenic isolate were characterized. The enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR)−based genome fingerprinting classified the 94 K. pneumoniae strains into 76 ERIC genotypes with 63 singletons, demonstrating considerable genetic diversity in the strains. The findings of this study fill the gap in the risk assessment of K. pneumoniae in edible aquatic animals.

Early-life antibiotic exposure increases the risk of childhood overweight and obesity in relation to dysbiosis of gut microbiota: a birth cohort study

Background

Early-life antibiotic exposure is associated with the development of later obesity through the disruption of gut microbiota in the animal models. However, the related epidemiological evidence is still conflicting.

Methods

A birth cohort was consisted of 2140 mother-infant pairs in Chaoyang District Maternal and Child Health Care Hospital in this study. Here, their available antibiotic exposure during the first one year of life was ascertained using a open-ended questionnaire and related anthropometric parameters from the health screening program. The compositions of gut microbiota were comprehensively analyzed by16S rRNA high throughput sequencing. Then the spearman correlations were performed by the multiple covariance-adjusted regressions between the antibiotic exposure with anthropometric parameters and compositions of gut microbiota.

Results

Among the 2140 subjects, the antibiotic exposure during the first one year of life was 53.04%, mainly by Cephalosporins (53.39%) and Erythromycins(27.67%) for the treatment of respiratory tract infection (79.56%), which were not significantly different among the subgroups. Compared to the control group, both childhood overweight and obesity at two and a half years were higher in the antibiotic exposed group, with higher percents of Faecalibacterium, Agathobacter and Klebsiella, and lower percentage of Bifidobacterium. Moreover, there were positively potential associations between early-life antibiotic exposure with the accelerated anthropometric parameters and disruption of Faecalibacterium, Agathobacter, Klebsiella and Bifidobacterium at two and a half years.

Conclusion

These above results proved that early-life antibiotic exposure was positively associated with the accelerated childhood overweight and obesity from one year to two and a half years by impacting the disorders of Faecalibacterium, Agathobacter, Klebsiella and Bifidobacterium, which would propose the theoretical basis for rationalizing the personalized antibiotic exposure among the infants to truly reflect the fairness of public health.

Supplementary information

The online version contains supplementary material available at 10.1186/s12941-022-00535-1.

Effects of early sub-therapeutic antibiotic administration on body tissue deposition, gut microbiota and metabolite profiles of weaned piglets

BACKGROUND

This study aimed to evaluate the effects of sub-therapeutic antibiotic (STA) administration and its subsequent withdrawal on the body tissue deposition, gut microbiota, and metabolite profiles of piglets. The piglets in the experimental group were fed with STA (30 mg kg^-1 bacitracin methylene disalicylate, 75 mg kg^-1 chlortetracycline, 300 mg kg^-1 calcium oxytetracycline) for 14 days and the target bodyweight of the withdrawal period was 25 kg.

RESULTS

The experiment was divided into two periods: the administration period and the withdrawal period. The results showed that STA did not improve piglets' growth performance during the two periods. Piglets treated with STA had lower body water deposition during the withdrawal period and tended to increase body lipid deposition during the withdrawal period and the whole period in comparison with the piglets in the control group. It was found that STA markedly altered the colonic microbiota and their metabolites in the piglets. Sub-therapeutic antibiotics were initially effective in decreasing the abundance of pathogenic bacteria during the administration period; however, STA could not continue the effect during the withdrawal period, leading to a rebound of pathogenic bacteria such as Alloprevotella and the increased abundance of other pathogenic bacteria like Oscillibacter. Remarkably, STA treatment decreased Blautia abundance. This bacterium plays a potential protective role against obesity. Metabolomic analysis indicated that STA mainly altered amino acid metabolism, lipid metabolism, and carbohydrate metabolism during the two periods. Spearman's correlation analysis showed that the gut microbiota was highly correlated with microbial metabolite changes.

CONCLUSION

These results suggest that early STA administration may alter body tissue deposition later in life by reshaping the gut microbiota and their metabolite profiles. © 2022 Society of Chemical Industry.

Dietary Bacitracin Methylene Disalicylate Improves Growth Performance by Mediating the Gut Microbiota in Broilers

The growth performance of livestock and poultry has always been a concern. However, much work is currently focused on the selection of breeds and diets to improve the growth performance of livestock and poultry. Furthermore, numerous studies have shown that the gut microbiota is closely related to the growth performance of livestock and poultry. At present, there are many reports on the impact of antibiotic intervention on the structure of gut microbiota. However, there are few reports on the influence of antibiotic intervention on the structure of intestinal microbes and the effect of this change on growth performance. Bacitracin methylene disalicylate (BMD) intervention changes the microbial structure in the caecum of broilers at different growth stages, as shown in this study. To further reveal the potential relationship between gut microbiota changes and growth performance caused by BMD intervention, correlation analysis was used for analysis. A total of 144 1-day-old male Cobb-Vantress were randomly divided into two groups. In addition to antibiotic-free starter mash diets, starter mash diets supplemented with 55 mg/kg BMD were also used, called the CON group and the BMD group, and lasted 28 days. (1) These study results showed that adding BMD to the diet had a significant effect on the growth performance of broilers. Compared with the CON group, the body weight of the BMD group increased significantly by 11.08% and 20.13% on Days 14 and 28, respectively (p < 0.05). Similarly, at 0−14, 14−28 and 0−28 days of age, the average daily gain of the BMD group increased significantly by 12.28%, 24.49% and 20.80%, respectively. The average daily feed intake of the BMD group increased significantly by 18.28%, 27.39% and 24.97% (p < 0.05). In addition, at 0−28 days of age, the feed conversion ratio increased significantly by 5.5% (p < 0.05). (2) Alpha diversity results show that BMD intervention has an impact on gut microbiota at different growth stages. (3) The early intervention significantly affected 7 taxa by Day 14, followed by 22 taxa by Day 28, which is similar to the results in the caecal flora. Compared with the CON group, the Christensenellaceae R-7 group had the highest linear discriminant analysis (LDA) score on Day 28. In addition, Pearson’s correlation analysis showed that the Lachnospiraceae FCS020 group was significantly negatively correlated with growth performance. In general, these results indicate that dietary supplementation of BMD has an effect on broiler gut microbiota structure and growth performance. However, changes in growth performance may be caused by the gut microbiota structure.

Dietary Exposure to Antibiotic Residues Facilitates Metabolic Disorder by Altering the Gut Microbiota and Bile Acid Composition

Antibiotics used as growth promoters in livestock and animal husbandry can be detected in animal-derived food. Epidemiological studies have indicated that exposure to these antibiotic residues in food may be associated with childhood obesity. Herein, the effect of exposure to a residual dose of tylosin—an antibiotic growth promoter—on host metabolism and gut microbiota was explored in vivo. Theoretical maximal daily intake (TMDI) doses of tylosin were found to facilitate high-fat-diet-induced obesity, induce insulin resistance, and perturb gut microbiota composition in mice. The obesity-related phenotypes were transferrable to germfree recipient mice, indicating that the effects of a TMDI dose of tylosin on obesity and insulin resistance occurred mainly via alteration of the gut microbiota. Tylosin TMDI exposure restricted to early life, the critical period of gut microbiota development, altered the abundance of specific bacteria related to host metabolic homeostasis later in life. Moreover, early-life exposure to tylosin TMDI doses was sufficient to modify the ratio of primary to secondary bile acids, thereby inducing lasting metabolic consequences via the downstream FGF15 signaling pathway. Altogether, these findings demonstrate that exposure to very low doses of antibiotic residues, whether continuously or in early life, could exert long-lasting effects on host metabolism by altering the gut microbiota and its metabolites.

IMPORTANCE This study demonstrates that even with limited exposure in early life, a residual dose of tylosin might cause long-lasting metabolic disturbances by altering the gut microbiota and its metabolites. Our findings reveal that the gut microbiota is susceptible to previously ignored environmental factors.

Trace amounts of antibiotic altered metabolomic and microbial profiles of weaned pigs infected with a pathogenic E. coli

Background

Our previous study has shown that supplementation of trace amounts of antibiotic exacerbated the detrimental effects of enterotoxigenic E. coli (ETEC) infection and delayed the recovery of pigs that may be associated with modified metabolites and metabolic pathways. Therefore, the objective of this study was to explore the impacts of trace levels of antibiotic (carbadox) on host metabolic profiles and colon microbiota of weaned pigs experimentally infected with ETEC F18.

Results

The multivariate analysis highlighted a distinct metabolomic profile of serum and colon digesta between trace amounts of antibiotic (TRA; 0.5 mg/kg carbadox) and label-recommended dose antibiotic (REC; 50 mg/kg carbadox) on d 5 post-inoculation (PI). The relative abundance of metabolomic markers of amino acids, carbohydrates, and purine metabolism were significantly differentiated between the TRA and REC groups (q < 0.2). In addition, pigs in REC group had the highest (P < 0.05) relative abundance of Lactobacillaceae and tended to have increased (P < 0.10) relative abundance of Lachnospiraceae in the colon digesta on d 5 PI. On d 11 PI, pigs in REC had greater (P < 0.05) relative abundance of Clostridiaceae compared with other groups, whereas had reduced (P < 0.05) relative abundance of Prevotellaceae than pigs in control group.

Conclusions

Trace amounts of antibiotic resulted in differential metabolites and metabolic pathways that may be associated with its slow responses against ETEC F18 infection. The altered gut microbiota profiles by label-recommended dose antibiotic may contribute to the promotion of disease resistance in weaned pigs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00703-5.

Growth promotion and antibiotic induced metabolic shifts in the chicken gut microbiome

Antimicrobial growth promoters (AGP) have played a decisive role in animal agriculture for over half a century. Despite mounting concerns about antimicrobial resistance and demand for antibiotic alternatives, a thorough understanding of how these compounds drive performance is missing. Here we investigate the functional footprint of microbial communities in the cecum of chickens fed four distinct AGP. We find relatively few taxa, metabolic or antimicrobial resistance genes similarly altered across treatments, with those changes often driven by the abundances of core microbiome members. Constraints-based modeling of 25 core bacterial genera associated increased performance with fewer metabolite demands for microbial growth, pointing to altered nitrogen utilization as a potential mechanism of narasin, the AGP with the largest performance increase in our study. Untargeted metabolomics of narasin treated birds aligned with model predictions, suggesting that the core cecum microbiome might be targeted for enhanced performance via its contribution to host-microbiota metabolic crosstalk.

This study compares the functional profiles of the cecal microbiome among chickens fed four different antimicrobial growth promoters. Chickens receiving narasin exhibited the largest performance increase via apparent nitrogen recycling by the core cecal microbiome.

Jejunoileal mucosal growth in mice with a limited microbiome

Previous work demonstrated enhanced enterocyte proliferation and mucosal growth in gnotobiotic mice, suggesting that intestinal flora participate in mucosal homeostasis. Furthermore, broad-spectrum enteral antibiotics are known to induce near germ-free (GF) conditions in mice with conventional flora (CONV). We hypothesized that inducing near GF conditions with broad-spectrum enteral antibiotics would cause ordered small intestinal mucosal growth in CONV mice but would have no effect in GF mice with no inherent microbiome. C57BL/6J CONV and GF mice received either an antibiotic solution (Ampicillin, Ciprofloxacin, Metronidazole, Vancomycin, Meropenem) or a vehicle alone. After treatment, small intestinal villus height (VH), crypt depth (CD), mucosal surface area (MSA), crypt proliferation index (CPI), apoptosis, and villus and crypt cell types were assessed. Antibiotic-treated CONV (Abx-CONV) mice had taller villi, deeper crypts, increased CPI, increased apoptosis, and greater MSA compared to vehicle-treated CONV mice. Minor differences were noted in enterocyte and enterochromaffin cell proportions between groups, but goblet and Paneth cell proportions were unchanged in Abx-CONV mice compared to vehicle-treated CONV mice (p>0.05). Antibiotics caused no significant changes in VH or MSA in GF mice when compared to vehicle-treated GF mice (p>0.05). Enteral administration of broad-spectrum antibiotics to mice with a conventional microbiome stimulates ordered small intestinal mucosal growth. Mucosal growth was not seen in germ-free mice treated with antibiotics, implying that intestinal mucosal growth is associated with change in the microbiome in this model.

Understanding host-microbiome-environment interactions: Insights from Daphnia as a model organism

Microbes perform a variety of vital functions that are essential for healthy ecosystems, ranging from nutrient recycling, antibiotic production and waste decomposition. In many animals, microbes become an integral part by establishing diverse communities collectively termed as "microbiome/s". Microbiomes defend their hosts against pathogens and provide essential nutrients necessary for their growth and reproduction. The microbiome is a polygenic trait that is dependent on host genotype and environmental variables. However, the alteration of microbiomes by stressful condition and their recovery is still poorly understood. Despite rapid growth in host-associated microbiome studies, very little is known about how they can shape ecological processes. Here, we review current knowledge on the microbiome of Daphnia, its role in fitness, alteration by different stressors, and the ecological and evolutionary aspects of host microbiome interactions. We further discuss how variation in Daphnia physiology, life history traits, and microbiome interactive responses to biotic and abiotic factors could impact patterns of microbial diversity in the total environment, which drives ecosystem function in many freshwater environments. Our literature review provides evidence that microbiome is essential for Daphnia growth, reproduction and tolerance against stressors. Though the core and flexible microbiome of Daphnia is still debatable, it is clear that the Daphnia microbiome is highly dependent on interactions among host genotype, diet and the environment. Different environmental factors alter the microbiome composition and diversity of Daphnia and reduce their fitness. These interactions could have important implications in shaping microbial patterns and their recycling as Daphnia are keystone species in freshwater ecosystem. This review provides a framework for studying these complex relationships to gain a better understanding of the ecological and evolutionary roles of the microbiome.

Dynamic changes in the intestinal microbial community of two time-aged soils under combined cadmium and ciprofloxacin contaminated conditions

The effects of combined contaminated soils containing cadmium (Cd) and ciprofloxacin (CIP) on the human gut microbiota are demonstrated using an in vitro test. Uncontaminated soil samples were artificially polluted with Cd and CIP using three different treatments (CK: 0 mg·kg^-1; CIPI: 5 mg·kg^-1, CIPII: 25 mg·kg^-1, and Cd: 80 mg·kg^-1). An experiment was performed to investigate the effect of Cd and CIP on the human colon microbiota using two aging times (D30: Day 30; D60: Day 60), and then the method of high-throughput 16S rRNA gene sequencing was used. In this study, we observed five phyla: Proteobacteria, Firmicutes, Synergistetes, Bacteroidetes, and Actinobacteria in colon microbial community. In addition, our results indicated that the relative abundances of the gut bacteria varied at the phylum level. Nevertheless, a slight decline in the relative abundance of Bacteroidetes among all the sets (compared to the D30-CK + Cd set) was revealed, and the lowest decline percentage of 90% was observed in the D60-CIPI + Cd set. Our results validated that the relative abundance of Rhodococcus increased with an increase in the CIP concentration in D30. In addition, this may disrupt normal physiological functions of the intestine after exposure to contaminated soil via the mouth. This study provides a theoretical basis for human risk assessment of oral exposure to Cd and CIP contaminated soils.

A systematic review on antibiotics misuse in livestock and aquaculture and regulation implications in China

China is one of the largest producers and consumers of antibiotics, and China is a larger producer of livestock farming and aquaculture in the world. The livestock farming and aquaculture industry is a major area of antibiotic misuse, which has caused serious antibiotic residues and environment pollution. The antibiotic residues exceeding the standard may lead to antibiotic resistances in animals or human bodies, which poses a threat to human health. In this context, this study tries to systematically review the current situation of antibiotic misuse in livestock and aquaculture in China, and put forward corresponding regulatiory measures for the central government. Based on the status quo of livestock farming and aquaculture in China, this study reviewed antibiotic misuse in livestock farming and aquaculture and antibiotic resistance in China, introduced China's current policies on antibiotic regulation and the gap between China and developed countries, and analyzed the implications of current regulatory policies on animal health and productivity. At last, we put forward suggestions for the future antibiotic regulation, including strictly implementing the relevant laws and regulations, formulating specific supporting measures, encouraging the research and development of antibiotic substitutes, introducing advanced technologies for supervision and regulation, strengthening the publicity of science popularization and enhancing the public's awareness of the rational use of antibiotics. If these policy recommendations can be implemented, they will significantly promote the regulation of antibiotic abuse.

Effect of Mass Azithromycin Distributions on Childhood Growth in Niger: A Cluster-Randomized Trial

IMPORTANCE

Mass azithromycin distributions may decrease childhood mortality, although the causal pathway is unclear. The potential for antibiotics to function as growth promoters may explain some of the mortality benefit.

OBJECTIVE

To investigate whether biannual mass azithromycin distributions are associated with increased childhood growth.

DESIGN, SETTING, AND PARTICIPANTS

This cluster-randomized trial was performed from December 2014 until March 2020 among 30 rural communities in Boboye and Loga departments in Niger, Africa, with populations from 200 to 2000 individuals. Communities were randomized in a 1:1 ratio to biannual mass distributions of azithromycin or placebo for children ages 1 to 59 months. Participants, field-workers, and study personnel were masked to treatment allocation. Height and weight changes from baseline to follow-up at 4 years were compared between groups. Data were analyzed from June through November 2021.

INTERVENTIONS

Participants received azithromycin at 20 mg/kg using height-based approximation or by weight for children unable to stand every 6 months at the participants' households. Placebo contained the vehicle of the azithromycin suspension.

MAIN OUTCOMES AND MEASURES

Longitudinal anthropometric assessments were performed on a random sample of children before the first treatment and then annually for 5 years. Height and weight were the prespecified primary outcomes.

RESULTS

Among 3936 children enrolled from 30 communities, baseline characteristics were similar between 1299 children in the azithromycin group and 2637 children in the placebo group (mean 48.2% [95% CI, 45.5% to 50.8%] girls vs 48.0% [95% CI, 45.7% to 50.3%] girls; mean age, 30.8 months [95% CI, 29.5 to 32.0 months] vs 30.6 months [95% CI, 29.2 to 31.6 months]). Baseline anthropometric assessments were performed among 2230 children, including 985 children in the azithromycin group and 1245 children in the placebo group, of whom follow-up measurements were available for 789 children (80.1%) and 1063 children (85.4%), respectively. At the prespecified 4-year follow-up visit, children in the azithromycin group gained a mean 6.7 cm (95% CI, 6.5 to 6.8 cm) in height and 1.7 kg (95% CI, 1.7 to 1.8 kg) in weight per year and children in the placebo group gained a mean 6.6 cm (95% CI, 6.4 to 6.7 cm) in height and 1.7 kg (95% CI, 1.7 to 1.8 kg) in weight per year. Height at 4 years was not statistically significantly different between groups when adjusted for baseline height (0.08 cm [95% CI, -0.12 to 0.28 cm] greater in the azithromycin group; P = .45), and neither was weight when adjusted for height and baseline weight (0.02 kg [95% CI, -0.10 to 0.06 kg] less in the azithromycin group; P = .64). However, among children in the shortest quartile of baseline height, azithromycin was associated with a 0.4 cm (95% CI, 0.1 to 0.7 cm) increase in height compared with placebo.

CONCLUSIONS AND RELEVANCE

This study did not find evidence of an association between mass azithromycin distributions and childhood growth, although subgroup analysis suggested some benefit for the shortest children. These findings suggest that the mortality benefit of mass azithromycin distributions is unlikely to be due solely to growth promotion.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02048007.

Gentamicin Induced Microbiome Adaptations Associate With Increased BCAA Levels and Enhance Severity of Influenza Infection

Involvement of gut microbiota in pulmonary disease by the gut-lung axis has been widely observed. However, the cross-talk messengers between respiratory mucosal immunity and gut microbiota are largely unknown. Using selective pharmacologic destruction of gut microenvironment mouse models, we found gut microbiota displayed significantly lower alpha diversity and relative abundance of bacteria in Gentamicin treated mice. Metagenomic studies revealed functional differences in gut bacteria in altering metabolic profiles in mice blood. Branched-chain amino acids (BCAAs) are the essential factors linked between gut and lung. During this process, selective destruction of gut microbiota by Gentamicin induced high levels of BCAAs, and the high levels of BCAAs impacted the lung immunity against influenza virus. In vivo, Gentamicin-treated mice or mice fed with high BCAAs diets displayed reduced survival. At the sites of infection, the number of CD11b⁺Ly6G⁺ cells decreased, and CD8⁺ T cells increased accompanied by exuberant expression of pro-inflammatory cytokines could result in tissue damage. CD11b⁺Ly6G⁺ cells transplantation conferred remarkable protection from influenza virus infections. In vitro, BCAAs promoted bone marrow-derived cells differentiation to dendritic cells. Taken together, these findings demonstrate that Gentamicin induced disruption of the gut microbiota leads to increased BCAA levels that suppress CD11b⁺Ly6c⁺ cell development in association with overactive CD8⁺ T responses which may contribute to enhanced severity of the viral infection.

Antibiotic effects on gut microbiota, metabolism, and beyond

Current advances on gut microbiota have broadened our view on host-microbiota interactions. As a microbiota-targeted approach, the use of antibiotics has been widely adopted to explore the role of gut microbiota in vivo. Antibiotics can change the microbial composition, resulting in varied effects, depending on the antibiotic class, dosage, and duration. Antibiotic intervention in early life leads to life-long phenotype alterations, including obesity. Antibiotic-induced changes in gut microbiota affect the epithelial utilization of both macronutrients (e.g., amino acids) and micronutrients (e.g., copper, vitamin E) and the redox homeostasis. Of particular interest is the regulation of gut anaerobiosis and aerobiosis by oxygen availability, which is closely related to epithelial metabolism. Additionally, antibiotic interventions enable to identify novel roles of gut microbiota in gut-liver axis and gut-brain axis. Indigenous antimicrobial molecules are produced by certain microbes, and they have the potential to affect function through eliciting changes in the gut microbiota. This review discusses at length these findings to gain a better and novel insight into microbiota-host interactions and the mechanisms involved.

Antibiotics and Host-Tailored Probiotics Similarly Modulate Effects on the Developing Avian Microbiome, Mycobiome, and Host Gene Expression

Alternative approaches are greatly needed to reduce the need for antibiotic use in food animal production. This study utilized a pipeline for the development of a host-tailored probiotic to enhance performance in commercial turkeys and modulate their microbiota, similar to the effects of low-dose antibiotic administration. We determined that a host-tailored probiotic, developed in the context of the commercial turkey gut microbiome, was more effective at modulating these parameters than a nontailored probiotic cocktail. Furthermore, the host-tailored probiotic mimicked many of the effects of a low-dose antibiotic growth promoter. Surprisingly, the effects of the antibiotic growth promoter and host-tailored probiotic were observed across kingdoms, illustrating the coordinated interkingdom effects of these approaches. This work suggests that tailored approaches to probiotic development hold promise for modulating the avian host and its microbiota.

The microbiome is important to all animals, including poultry, playing a critical role in health and performance. Low-dose antibiotics have historically been used to modulate food production animals and their microbiome. Identifying alternatives to antibiotics conferring similar modulatory properties has been elusive. The purpose of this study was to determine if a host-tailored probiotic could recapitulate effects of a low-dose antibiotic on host response and the developing microbiome. Over 13 days of life, turkey poults were supplemented continuously with a low-dose antibiotic or oral supplementation of a prebiotic with or without two different probiotics (8 cage units, n = 80 per group). Gastrointestinal bacterial and fungal communities of poults were characterized by 16S rRNA gene and ITS2 amplicon sequencing. Localized and systemic host gene expression was assessed using transcriptome sequencing (RNA-Seq), kinase activity was assessed by avian-specific kinome peptide arrays, and performance parameters were assessed. We found that development of the early-life microbiome of turkey poults was tightly ordered in a tissue- and time-specific manner. Low-dose antibiotic and turkey-tailored probiotic supplementation, but not nontailored probiotic supplementation, elicited similar shifts in overall microbiome composition during development compared to controls. Treatment-induced bacterial changes were accompanied by parallel shifts in the fungal community and host gene expression and enhanced performance metrics. These results were validated in pen trials that identified further additive effects of the turkey-tailored probiotic combined with different prebiotics. Alternative approaches to low-dose antibiotic use in poultry are feasible and can be optimized utilizing the indigenous poultry microbiome. Similar approaches may also be beneficial for humans.

Effects of dietary alpha-ketoglutarate on bacteria profiles in the faeces of lactating sows and their suckling piglets

The aim of the study was to investigate the effects of dietary alpha-ketoglutarate (AKG) on the faecal bacteria composition of suckling piglets after supplementation of AKG to the diet of lactating sows. After farrowing, the sows were assigned to either a normal lactation diet (control group, n = 12) or a diet supplemented with 0.25% AKG (AKG group, n = 12) based on body weight (BW) and parity. During the 21-d suckling period, BW and diarrhoea occurrences of piglets were recorded daily, while faeces were sampled weekly from sows and piglets. The levels of pH, ammonia, short-chain fatty acids (SCFA) and lactate in the faeces of piglets were determined. In particular, bacteria profiles in faeces of sows and their suckling piglets were examined by Illumina sequencing. The results showed that the AKG diet altered the faecal bacteria composition in sows during the 21-d lactation period, leading to increases (p < 0.05) in the abundances of genera Prevotella, Lactobacillus, Bacteroides and Methanobrevibacter, but decreases (p < 0.05) in the abundances of genera Oscillospira and Dorea. AKG supplement to the sows during lactation indirectly enhanced (p < 0.05) bacterial richness and SCFA levels (especially, acetate) in the faeces of piglets during the 21-d suckling period. It is suggested that maternal AKG supplementation alters the composition of faecal bacteria in the sows, and increases the faecal bacteria richness and acetate levels in the piglets, which might be associated with an enhanced growth performance of piglets.

Linear growth in preschool children treated with mass azithromycin distributions for trachoma: A cluster-randomized trial

Background

Mass azithromycin distributions have been shown to reduce mortality among pre-school children in sub-Saharan Africa. It is unclear what mediates this mortality reduction, but one possibility is that antibiotics function as growth promoters for young children.

Methods and findings

24 rural Ethiopian communities that had received biannual mass azithromycin distributions over the previous four years were enrolled in a parallel-group, cluster-randomized trial. Communities were randomized in a 1:1 ratio to either continuation of biannual oral azithromycin (20mg/kg for children, 1 g for adults) or to no programmatic antibiotics over the 36 months of the study period. All community members 6 months and older were eligible for the intervention. The primary outcome was ocular chlamydia; height and weight were measured as secondary outcomes on children less than 60 months of age at months 12 and 36. Study participants were not masked; anthropometrists were not informed of the treatment allocation. Anthropometric measurements were collected for 282 children aged 0–36 months at the month 12 assessment and 455 children aged 0–59 months at the month 36 assessment, including 207 children who had measurements at both time points. After adjusting for age and sex, children were slightly but not significantly taller in the biannually treated communities (84.0 cm, 95%CI 83.2–84.8, in the azithromycin-treated communities vs. 83.7 cm, 95%CI 82.9–84.5, in the untreated communities; mean difference 0.31 cm, 95%CI -0.85 to 1.47, P = 0.60). No adverse events were reported.

Conclusions

Periodic mass azithromycin distributions for trachoma did not demonstrate a strong impact on childhood growth.

Trial registration

The TANA II trial was registered on clinicaltrials.gov #NCT01202331.

Mass distribution of a single dose of the broad-spectrum antibiotic azithromycin twice per year to pre-school children in Sub-Saharan Africa has been shown to reduce childhood mortality. The mechanism by which azithromycin reduces mortality is currently not clear, especially since the antibiotic is not targeted to sick children but rather given to all children in the community whether or not they have an infectious disease. In this study, we report the height and weight of children enrolled in a trial in Ethiopia in which communities were randomized either to twice annual mass azithromycin distributions for blinding trachoma or to no treatments. After accounting for age and sex, children from azithromycin-treated communities were on average slightly taller at the 12- and 36-month study visits than those from untreated communities, but the difference was not statistically significant.

The Costs of Living Together: Immune Responses to the Microbiota and Chronic Gut Inflammation

While the vertebrate microbiota is critical to the normal function of many host traits, hosts may expend a large amount of energy to constrain and interface with their microbiota via their immune system to avoid the high fitness costs associated with gut dysbiosis, pathobionts, and opportunistic pathogens. All jawed vertebrates share mucosal immunity dedicated to isolating the microbiota, and a breakdown of this system can result in chronic gut inflammation. In humans, chronic gut inflammation negatively affects growth and development. There is little information available on the prevalence of chronic gut inflammation in wild animals, but given that animals with different life histories emphasize different immune responses, it follows that wild animals may vary in their susceptibility to chronic gut inflammation, and most animals will experience signaling that can lead to this state. These can be top-down signals originating from sources like the central nervous system or bottom-up signals originating from changes in the gut microbiota. The sources of these signals might include stress, developmental transitions, food restriction, and dietary shifts. Here, we briefly discuss host-microbiota interactions from the perspective of life history theory and ecoimmunology, focusing on the mucosal immune system and chronic gut inflammation. We also include future directions for research and the tools necessary to investigate them.

A Review on Gut Remediation of Selected Environmental Contaminants: Possible Roles of Probiotics and Gut Microbiota

Various environmental contaminants including heavy metals, pesticides and antibiotics can contaminate food and water, leading to adverse effects on human health, such as inflammation, oxidative stress and intestinal disorder. Therefore, remediation of the toxicity of foodborne contaminants in human has become a primary concern. Some probiotic bacteria, mainly Lactobacilli, have received a great attention due to their ability to reduce the toxicity of several contaminants. For instance, Lactobacilli can reduce the accumulation and toxicity of selective heavy metals and pesticides in animal tissues by inhibiting intestinal absorption of contaminants and enhancing intestinal barrier function. Probiotics have also shown to decrease the risk of antibiotic-associated diarrhea possibly via competing and producing antagonistic compounds against pathogenic bacteria. Furthermore, probiotics can improve immune function by enhancing the gut microbiota mediated anti-inflammation. Thus, these probiotic bacteria are promising candidates for protecting body against foodborne contaminants-induced toxicity. Study on the mechanism of these beneficial bacterial strains during remediation processes and particularly their interaction with host gut microbiota is an active field of research. This review summarizes the current understanding of the remediation mechanisms of some probiotics and the combined effects of probiotics and gut microbiota on remediation of foodborne contaminants in vivo.

Gut microbiota: puppeteer of the host juvenile growth

PURPOSE OF REVIEW

This review focuses on the recent discoveries about the impact of intestinal microbiota on mammalian host juvenile growth.

RECENT FINDINGS

Intestinal microbiota is a powerful modulator of many facets of multicellular host's physiology. Recent results from human field studies and animal research have clearly shown that not only the nutrition, but also the intestinal microbiota impacts host postnatal growth kinetics. Absence of microbiome leads to stunted growth in mammalian gnotobiotic models and changes in the composition of the intestinal microbiota can impact the postnatal growth kinetics both positively and negatively under normal nutritional conditions as well as in undernutrition. Strikingly, specific bacterial strains are able to interact with GH/IGF-1 somatotropic axis activity, thus directly impacting host juvenile development.

SUMMARY

Intestinal microbiota dictates the pace of host postnatal growth. This newly described role envisages that therapy with specific bacterial strains, together with re-nutritional strategies, might successfully alleviate the long-term sequelae of undernutrition during childhood in humans.

Tannins and Bacitracin Differentially Modulate Gut Microbiota of Broiler Chickens

Antibiotic growth promoters have been used for decades in poultry farming as a tool to maintain bird health and improve growth performance. Global concern about the recurrent emergence and spreading of antimicrobial resistance is challenging the livestock producers to search for alternatives to feed added antibiotics. The use of phytogenic compounds appears as a feasible option due to their ability to emulate the bioactive properties of antibiotics. However, detailed description about the effects of in-feed antibiotics and alternative natural products on chicken intestinal microbiota is lacking. High-throughput sequencing of 16S rRNA gene was used to study composition of cecal microbiota in broiler chickens supplemented with either bacitracin or a blend of chestnut and quebracho tannins over a 30-day grow-out period. Both tannins and bacitracin had a significant impact on diversity of cecal microbiota. Bacitracin consistently decreased Bifidobacterium while other bacterial groups were affected only at certain times. Tannins-fed chickens showed a drastic decrease in genus Bacteroides while certain members of order Clostridiales mainly belonging to the families Ruminococcaceae and Lachnospiraceae were increased. Different members of these groups have been associated with an improvement of intestinal health and feed efficiency in poultry, suggesting that these bacteria could be associated with productive performance of birds.

Hunger and microbiology: is a low gastric acid-induced bacterial overgrowth in the small intestine a contributor to malnutrition in developing countries?

Underproduction of hydrochloric acid into the stomach is frequently encountered in subjects from developing countries. We explore the hypothesis that hypochlorhydria compromises the gastric barrier and favours bacterial overgrowth in the proximal parts of the small intestine where nutrient absorption takes place. Food calories are thus deviated into bacterial metabolism. In addition to an adequate caloric supply, correcting hypochlorhydria might be needed to decrease childhood malnutrition.

Antibiotic use and microbiome function

Our microbiome should be understood as one of the most complex components of the human body. The use of β-lactam antibiotics is one of the microbiome covariates that influence its composition. The extent to which our microbiota changes after an antibiotic intervention depends not only on the chemical nature of the antibiotic or cocktail of antibiotics used to treat specific infections, but also on the type of administration, duration and dose, as well as the level of resistance that each microbiota develops. We have begun to appreciate that not all bacteria within our microbiota are vulnerable or reactive to different antibiotic interventions, and that their influence on both microbial composition and metabolism may differ. Antibiotics are being used worldwide on a huge scale and the prescription of antibiotics is continuing to rise; however, their effects on our microbiota have been reported for only a limited number of them. This article presents a critical review of the antibiotics or antibiotic cocktails whose use in humans has been linked to changes in the composition of our microbial communities, with a particular focus on the gut, oral, respiratory, skin and vaginal microbiota, and on their molecular agents (genes, proteins and metabolites). We review the state of the art as of June 2016, and cover a total of circa 68 different antibiotics. The data herein are the first to compile information about the bacteria, fungi, archaea and viruses most influenced by the main antibiotic treatments prescribed nowadays.

Effects of environmental pollutants on gut microbiota

Environmental pollutants have become an increasingly common health hazard in the last several decades. Recently, a number of studies have demonstrated the profound relationship between gut microbiota and our health. Gut microbiota are very sensitive to drugs, diet, and even environmental pollutants. In this review, we discuss the possible effects of environmental pollutants including antibiotics, heavy metals, persistent organic pollutants, pesticides, nanomaterials, and food additives on gut microbiota and their subsequent effects on health. We emphasize that gut microbiota are also essential for the toxicity evaluation of environmental pollution. In the future, more studies should focus on the relationship between environmental pollution, gut microbiota, and human health.

Illumina Miseq platform analysis caecum bacterial communities of rex rabbits fed with different antibiotics

Antibiotics have been widely used for the prevention and the treatment of diseases to humans and animals, and they have fed additives for agricultural animals to promote growth. However, there is a growing concern over the practice due to its side effects on intestinal microbial communities which plays a vital role in animals' health. To investigate the effect of antibiotics on the bacterial population of the caecum in rex rabbits, 80 rex rabbits were randomly divided into four groups: control group (B, basal diet), chlortetracycline group (C, 50 mg/kg), colistin sulfate group (S, 20 mg/kg) and zinc bacitracin group (Z, 40 mg/kg). Caecum microbial communities of rex rabbits from the four groups were analyzed through Illumina Miseq platform after being fed 28 days. The results showed that most obtained sequences belongs to Firmicutes followed by Bacteroidetes, and the ratio of Bacteroidetes/Firmicutes in C group (42.31 %) was higher than that in Z group (21.84 %). Zinc bacitracin supplementation caused a significant decreased of the Proteobacteria phylum and Lactobacillus spp. (P < 0.05), while the Lactobacillus spp. significantly increased in S group (P < 0.05). In addition, Ruminococcus spp., especially Ruminococcus albus were the predominant bacterial species found in both S and Z groups. The proportion of Coprococcus spp. significantly increased in Z group (P < 0.05). These findings suggested that the antibiotics used may cause significant changes in the caecum microbiota of rex rabbits, and we also found C group had a similarity caecum bacteria structure with B group which was probably due to the high levels of chlortetracycline resistance.

Oral imazalil exposure induces gut microbiota dysbiosis and colonic inflammation in mice

The fungicide imazalil (IMZ) is used extensively in vegetable and fruit plantations and as a post-harvest treatment to avoid rot. Here, we revealed that ingestion of 25, 50 and 100 mg IMZ kg(-1) body weight for 28 d induced gut microbiota dysbiosis and colonic inflammation in mice. The relative abundance of Bacteroidetes, Firmicutes and Actinobacteria in the cecal contents decreased significantly after exposure to 100 mg kg(-1) IMZ for 28 d. In feces, the relative abundance in Bacteroidetes, Firmicutes and Actinobacteria decreased significantly after being exposed to 100 mg kg(-1) IMZ for 1, 14 and 7 d, respectively. High throughput sequencing of the V3-V4 region of the bacterial 16S rRNA gene revealed a significant reduction in the richness and diversity of microbiota in cecal contents and feces of IMZ-treated mice. Operational taxonomic units (OTUs) analysis identified 49.3% of OTUs changed in cecal contents, while 55.6% of OTUs changed in the feces after IMZ exposure. Overall, at the phylum level, the relative abundance of Firmicutes, Proteobacteria and Actinobacteria increased and that of Bacteroidetes decreased in IMZ-treated groups. At the genus level, the abundance of Lactobacillus and Bifidobacterium decreased while those of Deltaproteobacteria and Desulfovibrio increased in response to IMZ exposure. In addition, it was observed that IMZ exposure could induce colonic inflammation characterized by infiltration of inflammatory cells, elevated levels of lipocalin-2 (lcn-2) in the feces, and increased mRNA levels of Tnf-α, IL-1β, IL-22 and IFN-γ in the colon. Our findings strongly suggest that ingestion of IMZ has some risks to human health.

Impact of 4-epi-oxytetracycline on the gut microbiota and blood metabolomics of Wistar rats

The impact of 4-epi-oxytetracycline (4-EOTC), one of the main oxytetracycline (OTC) metabolites, on the gut microbiota and physiological metabolism of Wistar rats was analyzed to explore the dynamic alterations apparent after repeated oral exposure (0.5, 5.0 or 50.0 mg/kg bw) for 15 days as shown by 16S rRNA pyrosequencing and UPLC-Q-TOF/MS analysis. Both principal component analysis and cluster analysis showed consistently altered patterns with distinct differences in the treated groups versus the control groups. 4-EOTC treatment at 5.0 or 50.0 mg/kg increased the relative abundance of the Actinobacteria, specifically Bifidobacteriaceae, and improved the synthesis of lysophosphatidylcholine (LysoPC), as shown by the lipid biomarkers LysoPC(16:0), LysoPC(18:3), LysoPC(20:3), and LysoPC(20:4). The metabolomic analysis of urine samples also identified four other decreased metabolites: diacylglycerol, sphingomyelin, triacylglycerol, and phosphatidylglycerol. Notably, the significant changes observed in these biomarkers demonstrated the ongoing disorder induced by 4-EOTC. Blood and urine analysis revealed that residual 4-EOTC accumulated in the rats, even two weeks after oral 4-EOTC administration, ceased. Thus, through thorough analysis, it can be concluded that the alteration of the gut microbiota and disorders in blood metabolomics are correlated with 4-EOTC treatment.