Influence of the Type of Diet on the Incidence of Pathogenic Factors and Antibiotic Resistance in Enterococci Isolated from Faeces in Mice

Molecular identification and probiotic potential characterization of lactic acid bacteria isolated from the pigs with superior immune responses

Lactic acid bacteria (LAB) belong to a significant group of probiotic bacteria that provide hosts with considerable health benefits. Our previous study showed that pigs with abundant LAB had more robust immune responses in a vaccination experiment. In this study, 52 isolate strains were isolated from the pigs with superior immune responses. Out of these, 14 strains with higher antibacterial efficacy were chosen. We then assessed the probiotic features of the 14 LAB strains, including such as autoaggregation, coaggregation, acid resistance, bile salt resistance, and adhesion capability, as well as safety aspects such as antibiotic resistance, hemolytic activity, and the presence or absence of virulence factors. We also compared these properties with those of an opportunistic pathogen EB1 and two commercial probiotics (cLA and cLP). The results showed that most LAB isolates exhibited higher abilities of aggregation, acid and bile salt resistance, adhesion, and antibacterial activity than the two commercial probiotics. Out of the 14 strains, only LS1 and LS9 carried virulence genes and none had hemolytic activity. We selected three LAB strains (LA6, LR6 and LJ1) with superior probiotic properties and LS9 with a virulence gene for testing their safety in vivo. Strains EB1, cLA and cLP were also included as control bacteria. The results demonstrated that mice treated LAB did not exhibit any adverse effects on weight gain, organ index, blood immune cells, and ileum morphology, except for those treated with LS9 and EB1. Moreover, the antimicrobial effect of LR6 and LA6 strains was examined in vivo. The results indicated that these strains could mitigate the inflammatory response, reduce bacterial translocation, and alleviate liver, spleen, and ileum injury caused by Salmonella typhimurium infection. In addition, the LR6 treatment group showed better outcomes than the LA6 treatment group; treatment with LR6 substantially reduced the mortality rate in mice. The study results provide evidence of the probiotic properties of the LAB isolates, in particular LR6, and suggest that oral administration of LR6 could have valuable health-promoting benefits.

Intestinal microbiota modulation at the strain level by the olive oil polyphenols in the diet

Introduction

Previously we have reported a r16S gene next generation sequencing study on the effect of high fat diets in the intestinal microbiota using a murine model. However, many important microbial traits occur at strain level and, in order to detect these population changes, culture-dependent approaches need to be applied. With this goal, we decided to study a very well-known commensal genus, Enterococcus, and therefore, intestinal enterococci methodically isolated during the above-mentioned experiment were analyzed.

Materials and methods

A collection of 75 distinct enterococcal strains isolated from feces of mice fed a standard diet or high-fat diets enriched with butter, refined olive oil, or extra virgin olive oil and after 0, 6 or 12 weeks of diet, were genetically and phenotypically characterized in search of virulence factors, biogenic amine production and antibiotic resistance. All strains were tested for the susceptibility in vitro to two virgin olive oil polyphenols, oleuropein (the bitter principle of olives) and hydroxytyrosol (derived from oleuropein by enzymatic hydrolysis and responsible for the high stability of olive oil).

Results

No drastic polyphenol effect was found except at high concentrations. However, when carrying out a comparative statistical study in the 75 strains of the collection according to the different diets, we have detected significant differences between the strains isolated from mice fed with a diet enriched with virgin olive oil and the rest of the diets. EVOO strains also presented less resistance to antibiotics and a more beneficial profile overall.

Discussion

These results support the prebiotic role of polyphenols, showing how they are able to modulate the set of strains that comprises a genus in the gut, allowing them to adapt to a changing environment in the host's intestine and possibly exerting effects on its physiology.

Amoxicillin impact on pathophysiology induced by short term high salt diet in mice

Current evidence emerging from both human and animal models confirms that high-salt diet consumption over a period modulates the gut ecology and subsequently accelerates the development of the pathophysiology of many metabolic diseases. The knowledge of short-term intake of a high-salt diet (HSD) on gut microbiota and their role in the progression of metabolic pathogenesis and the consequence of a typical course of common antibiotics in this condition has yet not been investigated. The present study elicited this knowledge gap by studying how the gut microbiota profile changes in mice receiving HSD for a short period followed by Amoxicillin treatment on these mice in the last week to mimic a typical treatment course of antibiotics. In this study, we provided a standard chow diet (CD) and HSD for 3 weeks, and a subset of these mice on both diets received antibiotic therapy with Amoxicillin in the 3rd week. We measured the body weight of mice for 3 weeks. After 21 days, all animals were euthanised and subjected to a thorough examination for haemato-biochemical, histopathological, and 16S rRNA sequencing, followed by bioinformatics analysis to determine any changes in gut microbiota ecology. HSD exposure in mice for short duration even leads to a significant difference in the gut ecology with enrichment of specific gut microbiota crucially linked to developing the pathophysiological features of metabolic disease-related inflammation. In addition, HSD treatment showed a negative impact on haemato-biochemical parameters. However, Amoxicillin treatment in HSD-fed mice restored the blood-biochemical markers near to control values and reshaped gut microbiota known for improving the pathophysiological attributes of metabolic disease related inflammation. This study also observed minimal and insignificant pathological changes in the heart, liver, and kidney in HSD-fed mice.

High fat diets induce early changes in gut microbiota that may serve as markers of ulterior altered physiological and biochemical parameters related to metabolic syndrome. Effect of virgin olive oil in comparison to butter

Butter and virgin olive oil (EVOO) are two fats differing in their degree of saturation and insaponifiable fraction. EVOO, enriched in polyphenols and other minority components, exerts a distinct effect on health. Using next generation sequencing, we have studied early and long-term effects of both types of fats on the intestinal microbiota of mice, finding significant differences between the two diets in the percentage of certain bacterial taxa, correlating with hormonal, physiological and metabolic parameters in the host. These correlations are not only concomitant, but most noticeably some of the changes detected in the microbial percentages at six weeks are correlating with changes in physiological values detected later, at twelve weeks. Desulfovibrionaceae/Desulfovibrio/D. sulfuricans stand out by presenting at six weeks a statistically significant higher percentage in the butter-fed mice with respect to the EVOO group, correlating with systolic blood pressure, food intake, water intake and insulin at twelve weeks. This not only suggests an early implication in the probability of developing altered physiological and biochemical responses later on in the host lifespan, but also opens the possibility of using this genus as a marker in the risk of suffering different pathologies in the future.

Antimicrobial Resistance Phenotypes and Genotypes of Escherichia coli Isolates from Broiler Chickens Fed Encapsulated Cinnamaldehyde and Citral

ABSTRACT

This study was conducted to investigate the effects of in-feed encapsulated cinnamaldehyde (CIN) and citral (CIT) alone or in combination on antimicrobial resistance (AMR) phenotypes and genotypes of Escherichia coli isolates recovered from feces of 6-, 16-, 23-, and 27-day-old broiler chickens. The five dietary treatments including the basal diet (negative control [NC]) and the basal diet supplemented with 55 ppm of bacitracin (BAC), 100 ppm of encapsulated CIN, 100 ppm of encapsulated CIT, or 100 ppm each of encapsulated CIN and encapsulated CIT (CIN+CIT). Antimicrobial susceptibility testing of 240 E. coli isolates revealed that the most common resistance was to β-lactams, aminoglycosides, sulfonamides, and tetracycline; however, the prevalence of AMR decreased (P < 0.05) as birds aged. The prevalence of resistance to amoxicillin-clavulanic acid, ceftiofur, ceftriaxone, cefoxitin, gentamicin, and sulfonamide was lower (P < 0.05) in isolates from the CIN or CIN+CIT groups than in isolates from the NC or BAC groups. Whole genome sequencing of 227 of the 240 isolates revealed 26 AMR genes and 19 plasmids, but the prevalence of some AMR genes and the number of plasmids were lower (P < 0.05) in E. coli isolated from CIN or CIN+CIT birds than in isolates from NC or BAC birds. The most prevalent resistance genes were tet(A) (108 isolates), aac(3)-VIa (91 isolates), aadA1 (86 isolates), blaCMY-2 (78 isolates), sul1 (77 isolates), aph(3)-Ib (58 isolates), aph(6)-Id (58 isolates), and sul2 (24 isolates). The numbers of most virulence genes carried by isolates increased (P < 0.05) in chickens from 6 to 27 days of age. The prevalence of E. coli O21:H16 isolates was lower (P < 0.05) in CIN and CIN+CIT, and the colibacillosis-associated multilocus sequence type (ST117) was most prevalent in isolates from 23-day-old chickens. A phylogenetic tree of whole genome sequences revealed a close relationship between 25 of the 227 isolates and human or broiler extraintestinal pathogenic E. coli strains. These findings indicate that AMR and virulence genotypes of E. coli could be modulated by providing encapsulated CIN or CIN+CIT feed supplements, but further investigation is needed to determine the mechanisms of the effects of these supplements.

HIGHLIGHTS

Prevalence of an Intestinal ST40 Enterococcus faecalis over Other E. faecalis Strains in the Gut Environment of Mice Fed Different High Fat Diets

E. faecalis is a commensal bacterium with specific strains involved in opportunistic and nosocomial infections. Therefore, it is important to know how the strains of this species are selected in the gut. In this study, fifteen E. faecalis strains, isolated over twelve weeks from the faeces of mice fed standard chow or one of three high fat diets enriched with extra virgin olive oil, refined olive oil or butter were subjected to a genetic “Multilocus Sequence Typing” study that revealed the presence of mainly two genotypes, ST9 and ST40, the latter one prevailing at the end of the research. A V3–V5 sequence comparison of the predominant ST40 strain (12B3-5) in a metagenomic study showed that this sequence was the only E. faecalis present in the mouse cohort after twelve weeks. The strain was subjected to a comparative proteomic study with a ST9 strain by 2D electrophoresis and mass spectrometry. After comparing the results with a E. faecalis database, unshared entries were compared and 12B3-5 showed higher antimicrobial production as well as greater protection from environmental factors such as xenobiotics, oxidative stress and metabolite accumulation, which could be the reason for its ability to outcompete other possible rivals in an intestinal niche.