Effects of subtherapeutic concentrations of antimicrobials on gene acquisition events in Yersinia, Proteus, Shigella, and Salmonella recipient organisms in isolated ligated intestinal loops of swine

Feeding with 4,4'-diaponeurosporene-producing Bacillus subtilis enhances the lactogenic immunity of sow

Specific antibodies produced sow by oral porcine epidemic diarrhea virus (PEDV) vaccines would transfer to newborn piglets via colostrum, and it is an effective strategy to prevent porcine epidemic diarrhea (PED). However, there is a lag in the development of corresponding vaccines due to the rapid mutation of PEDV, which could increase the difficulty of PED prevention and control in pig farms. Hence, congenital lactogenic immunity was assessed by feeding 4,4'-diaponeurosporene-producing Bacillus subtilis (B.S-Dia) to sow on the 80th day of gestation in order to protect newborn piglets from PEDV infection. Firstly, we found that the quantities of T lymphocytes and monocytes in the blood and colostrum after oral administration of B.S-Dia were significantly increased as observed by flow cytometry, whereas the proliferative activity of T lymphocytes in colostrum was also markedly increased. Furthermore, enzyme-linked immunosorbent assay (ELISA) results revealed that levels of TGF (Transforming growth factor) -β, Interleukin (IL) -6, lysozyme and lactoferrin were significantly increased. Finally, it was found in the piglets' challenge protection test that offspring pigs of the sows feeding B.S-Dia during pregnancy did not develop diarrhea symptoms and intestinal pathological changes at 48 h after infection with PEDV, and PEDV load in the jejunum and ileum was significantly reduced, but offspring pigs of the sows taking orally PBS during pregnancy developed pronounced diarrhea symptoms and extensive PEDV colonization was noted both in the jejunum and ileum. In summary, sow by oral administration of B.S-Dia substantially increased congenital lactogenic immunity, thereby preventing newborn piglets from being infected with PEDV.

Porcine intraepithelial lymphocytes undergo migration and produce an antiviral response following intestinal virus infection

The location of intraepithelial lymphocytes (IELs) between epithelial cells provide a first line of immune defense against enteric infection. It is assumed that IELs migrate only along the basement membrane or into the lateral intercellular space (LIS) between epithelial cells. Here, we identify a unique transepithelial migration of porcine IELs as they move to the free surface of the intestinal epithelia. The major causative agent of neonatal diarrhea in piglets, porcine epidemic diarrhea virus (PEDV), increases the number of IELs entering the LIS and free surface of the intestinal epithelia, driven by chemokine CCL2 secreted from virus-infected intestinal epithelial cells. Remarkably, only virus pre-activated IELs inhibits PEDV infection and their antiviral activity depends on the further activation by virus-infected cells. Although high levels of perforin is detected in the co-culture system, the antiviral function of activated IELs is mainly mediated by IFN-γ secretion inducing robust antiviral response in virus-infected cells. Our results uncover a unique migratory behavior of porcine IELs as well as their protective role in the defense against intestinal infection.

When piglets are infected with intestinal virus, porcine intraepithelial lymphocytes undergo intra-and trans-epithelial migration promoted by chemokines from infected epithelial cells and produce an antiviral response.

The use of aminoglycosides in animals within the EU: development of resistance in animals and possible impact on human and animal health: a review

Aminoglycosides (AGs) are important antibacterial agents for the treatment of various infections in humans and animals. Following extensive use of AGs in humans, food-producing animals and companion animals, acquired resistance among human and animal pathogens and commensal bacteria has emerged. Acquired resistance occurs through several mechanisms, but enzymatic inactivation of AGs is the most common one. Resistance genes are often located on mobile genetic elements, facilitating their spread between different bacterial species and between animals and humans. AG resistance has been found in many different bacterial species, including those with zoonotic potential such as Salmonella spp., Campylobacter spp. and livestock-associated MRSA. The highest risk is anticipated from transfer of resistant enterococci or coliforms (Escherichia coli) since infections with these pathogens in humans would potentially be treated with AGs. There is evidence that the use of AGs in human and veterinary medicine is associated with the increased prevalence of resistance. The same resistance genes have been found in isolates from humans and animals. Evaluation of risk factors indicates that the probability of transmission of AG resistance from animals to humans through transfer of zoonotic or commensal foodborne bacteria and/or their mobile genetic elements can be regarded as high, although there are no quantitative data on the actual contribution of animals to AG resistance in human pathogens. Responsible use of AGs is of great importance in order to safeguard their clinical efficacy for human and veterinary medicine.

Residues of chlortetracycline, doxycycline and sulfadiazine-trimethoprim in intestinal content and feces of pigs due to cross-contamination of feed

Background

Cross-contamination of feed with low concentrations of antimicrobials can occur at production, transport and/or farm level. Concerns are rising about possible effects of this contaminated feed on resistance selection in the intestinal microbiota. Therefore, an experiment with pigs was set up, in which intestinal and fecal concentrations of chlortetracycline (CTC), doxycycline (DOX) and sulfadiazine-trimethoprim (SDZ-TRIM) were determined after administration of feed containing a 3 % carry-over level of these antimicrobials.

Results

The poor oral bioavailability of tetracyclines resulted in rather high concentrations in cecal and colonic content and feces at steady-state conditions. A mean concentration of 10 mg/kg CTC and 4 mg/kg DOX in the feces was reached, which is higher than concentrations that were shown to cause resistance selection. On the other hand, lower mean levels of SDZ (0.7 mg/kg) and TRIM (< limit of detection of 0.016 mg/kg) were found in the feces, corresponding with the high oral bioavailability of SDZ and TRIM in pigs.

Conclusions

The relation between the oral bioavailability and intestinal concentrations of the tested antimicrobials, may be of help in assessing the risks of cross-contaminated feed. However, future research is needed to confirm our results and to evaluate the effects of these detected concentrations on resistance selection in the intestinal microbiota of pigs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0803-8) contains supplementary material, which is available to authorized users.

Inhibition of the virulence, antibiotic resistance, and fecal shedding of multiple antibiotic-resistant Salmonella Typhimurium in broilers fed Original XPC™

Salmonella carriage is an insidious problem for the poultry industry. While most Salmonella serotypes are avirulent in poultry, these bacteria can contaminate chicken meat during processing, leading to one of the most important food safety hazards. In this study, we examined the anti-Salmonella effects of Diamond V Original XPC^™ (XPC) included in the finisher diet fed to commercial broilers. On 3 occasions between day one (D1) and D20, broilers were experimentally infected with multiple antibiotic-resistant Salmonella Typhimurium. After confirming that the chicks were shedding Salmonella in the feces on D21, broiler chicks were fed a diet containing XPC (n = 57 birds; 1.25 kg/MT) or an XPC-free control diet (CON) (n = 57 birds) to D49. Fecal samples were obtained weekly and subjected to selective culture for enumerating and determining the antibiotic resistance of the Salmonella. Salmonella isolates were then subjected to an in vitro virulence assay, which predicts the ability of Salmonella to cause illness in a mammalian host. Broilers were euthanized on D49 and a segment of the large intestine was removed and subjected to the same assays used for the fecal samples. When compared to the birds fed the CON diet, Salmonella fecal shedding, virulence (invasion and invasion gene expression), and antibiotic resistance were significantly decreased in birds fed XPC (5-fold, 7.5-fold, 6-fold, and 5.3-fold decreases, respectively). Birds fed XPC exhibited heavier body weight (BW) and greater BW gains than those fed the CON diet. The decrease in virulence was associated with a decreased expression of a genetic regulator of Salmonella invasion into cells (hilA), while the decrease in antibiotic resistance was due to a loss of an integron (SGI1) from the input strain. This study revealed that Original XPC^™ inhibits the shedding, downstream virulence, and antibiotic resistance of Salmonella residing in broilers.

Pharmacokinetics of oral chlortetracycline in nonpregnant adult ewes

The objectives of this study were to determine plasma concentrations and pharmacokinetic parameters of feed-grade chlortetracycline (CTC) in sheep after oral administration of 80 or 500 mg/head daily, divided into two equal doses given at 12-h intervals for 8 days. These are the approved, and commonly used but unapproved, feed additive doses, respectively, in the United States for the prevention of ovine infectious abortion. Blood samples were collected just prior to dosing at 0, 12, 24, 72, 96, and 192 h, as well as 4, 8, 12, 24, and 36 h after the last dose, and noncompartmental pharmacokinetic analysis was performed to estimate elimination half-life and area under the plasma concentration-time curve (AUC). Mean observed maximum CTC concentrations (Cmax ) were 20.0 ng/mL (80 mg dose) and 101 ng/mL (500 mg dose). Mean apparent elimination half-life was 18 h (80 mg dose) and 20 h (500 mg dose). Although published data do not exist to estimate plasma CTC concentrations necessary for the prevention of ovine infectious abortion, concentrations reached in our study suggest that either the FDA-approved and FDA-unapproved dosages are not high enough or that the pharmacodynamic parameter relating preventive dose to pathogen minimum inhibitory concentrations is yet to be determined.

Altered egos: antibiotic effects on food animal microbiomes

The human food chain begins with upwards of 1,000 species of bacteria that inhabit the intestinal tracts of poultry and livestock. These intestinal denizens are responsible for the health and safety of a major protein source for humans. The use of antibiotics to treat animal diseases was followed by the surprising discovery that antibiotics enhanced food animal growth, and both led to six decades of antibiotic use that has shaped food animal management practices. Perhaps the greatest impact of antibiotic feeding in food animals has been as a selective force in the evolution of their intestinal bacteria, particularly by increasing the prevalence and diversity of antibiotic resistance genes. Future antibiotic use will likely be limited to prudent applications in both human and veterinary medicine. Improved knowledge of antibiotic effects, particularly of growth-promoting antibiotics, will help overcome the challenges of managing animal health and food safety.

Carbadox has both temporary and lasting effects on the swine gut microbiota

Antibiotics are used in livestock and poultry production to treat and prevent disease as well as to promote animal growth. Carbadox is an in-feed antibiotic that is widely used in swine production to prevent dysentery and to improve feed efficiency. The goal of this study was to characterize the effects of carbadox and its withdrawal on the swine gut microbiota. Six pigs (initially 3-weeks old) received feed containing carbadox and six received unamended feed. After 3-weeks of continuous carbadox administration, all pigs were switched to a maintenance diet without carbadox. DNA was extracted from feces (n = 142) taken before, during, and following (6-week withdrawal) carbadox treatment. Phylotype analysis using 16S rRNA sequences showed the gradual development of the non-medicated swine gut microbiota over the 8-week study, and that the carbadox-treated pigs had significant differences in bacterial membership relative to non-medicated pigs. Enumeration of fecal Escherichia coli showed that a diet change concurrent with carbadox withdrawal was associated with an increase in the E. coli in the non-medicated pigs, suggesting that carbadox pre-treatment prevented an increase of E. coli populations. In-feed carbadox caused striking effects within 4 days of administration, with significant alterations in both community structure and bacterial membership, notably a large relative increase in Prevotella populations in medicated pigs. Digital PCR was used to show that the absolute abundance of Prevotella was unchanged between the medicated and non-medicated pigs despite the relative increase shown in the phylotype analysis. Carbadox therefore caused a decrease in the abundance of other gut bacteria but did not affect the absolute abundance of Prevotella. The pending regulation on antibiotics used in animal production underscores the importance of understanding how they modulate the microbiota and impact animal health, which will inform the search for antibiotic alternatives.

Simultaneous infections by different Salmonella strains in mesenteric lymph nodes of finishing pigs

BACKGROUND

Salmonellosis is a major worldwide zoonosis, and Salmonella-infected finishing pigs are considered one of the major sources of human infections in developed countries. Baseline studies on salmonellosis prevalence in fattening pigs in Europe are based on direct pathogen isolation from mesenteric lymph nodes (MLN). This procedure is considered the most reliable for diagnosing salmonellosis in apparently healthy pigs. The presence of simultaneous infections by different Salmonella strains in the same animal has never been reported and could have important epidemiological implications.

RESULTS

Fourteen finishing pigs belonging to 14 farms that showed high salmonellosis prevalence and a variety of circulating Salmonella strains, were found infected by Salmonella spp, and 7 of them were simultaneously infected with strains of 2 or 3 different serotypes. Typhimurium isolates showing resistance to several antimicrobials and carrying mobile integrons were the most frequently identified in the colonized MLN. Four animals were found infected by Salmonella spp. of a single serotype (Rissen or Derby) but showing 2 or 3 different antimicrobial resistance profiles, without evidence of mobile genetic element exchange in vivo.

CONCLUSION

This is the first report clearly demonstrating that pigs naturally infected by Salmonella may harbour different Salmonella strains simultaneously. This may have implications in the interpretation of results from baseline studies, and also help to better understand human salmonellosis outbreaks and the horizontal transmission of antimicrobial resistance genes.