Tulathromycin, a macrolide antibiotic, is used for the treatment of respiratory disease in cattle and swine. The aim of our study was to investigate the in vitro and ex vivo activities of tulathromycin in serum, (noninflamed) transudate, and (inflamed) exudate against Pasteurella multocida in piglets. The pharmacokinetics properties of tulathromycin were studied for serum, transudate, and exudate using a tissue cage model. In vitro antibiotic susceptibility of P. multocida and dynamic time-kill curve experiments over eight tulathromycin concentrations were determined. The ratio of 24-h area under the concentration–time curve to minimum inhibitory concentration (AUC(0-24h)/MIC) was recognized as an important pharmacokinetic/pharmacodynamic (PK/PD) parameter of tulathromycin for antibacterial efficiency (R2= 0.9969). In serum ex vivo, for bacteriostatic, bactericidal activity, and virtual bacterial eradication AUC(0-24h)/MIC values for tulathromycin were 44.55, 73.19, and 92.44 h by using sigmoid Emax model WinNonlin software, respectively, and lower values were obtained for exudate and transudate. In conjunction with the data on MIC90, the dose of tulathromycin for a bacteriostatic effect and virtual elimination of P. multocida as computed using the value of the PK/PD breakpoint obtained in serum were 6.39 and 13.25mg/kg. However, it would be preferable to calculate a dose combined with population pharmacokinetics data to optimize the dosage regimen for bacteriological and clinical cure.

Inflammation leads to porcine tight junction disruption of small intestinal epithelial cells, resulting in intestinal dysfunction. Herein, we established lipopolysaccharide (LPS)-induced in-vivo and in-vitro inflammatory models. The results revealed that LPS induced tight junction disruption in IPEC-J2 cells by downregulating tight-junction-related protein zonula occludens-1 (ZO-1), occludin and claudin-1 expression, while ginsenoside Rg1 rescued such inhibition and abrogated the upregulated expression of phosphorylation p38 MAPK. The p38 MAPK inhibitor (SB203580) showed a similar effect with Rg1 and attenuated the LPS-induced inhibition of ZO-1, occludin and claudin-1 expression, which is consistent with the reduced expression of NLRP3 inflammasome and IL-1β. Furthermore, the specific inhibitors of NLRP3 and IL-1β result in increased expression of tight-junction-related protein, demonstrating that p38 MAPK signaling was associated with Rg1 suppression of tight junction disruption. Besides, LPS treatment decreased the expression of ZO-1, occludin and claudin-1 through p38 MAPK signaling, and caused abnormal morphological changes in murine ileum. Meanwhile, Rg1 attenuated the decreased expression of ZO-1, occludin and claudin-1 and partially alleviated LPS-induced morphological changes in murine ileum. In summary, these findings characterized a novel mechanism by which Rg1 alleviates LPS-induced intestinal tight junction disruption by inhibiting the p38 MAPK-mediated NLRP3 inflammasome pathway.

Background: Haemophilus parasuisis a commensal organism of the upper respiratory tract of healthy pigs and causes high morbidity and mortality in piglets. The aim of this study was to investigate the epidemiology ofH. parasuisin China from 2014 to 2017.Methods: We characterized 143H. parasuisisolates by serotyping, antimicrobial susceptibility, biofilm formation and with enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) assays.Results: Serotyping revealed serovar 5 as the most prevalent (26.6%) followed by serovars 4 (22.4%), 7 (9.1 %), 13 (6.3%), 12 (5.6 %), and non-typeable (8.4%). In a panel of 23 antimicrobials, the minimum inhibitory concentration 50% (MIC₅₀) were in the range of 0.25–16 μg/mL and MIC₉₀were 2–>512 μg/mL. A total of 99 isolates ofH. parasuis(69.2%) were able to form biofilms and 59.6% (59/99) performed weak biofilm-forming ability. ERIC-PCR revealed a very heterogeneous pattern with 87 clusters.Discussion: TheseH. parasuisisolates showed a high serovar and genotypic lineage diversity, different abilities to form biofilms and a high degree of genetic diversity. Biofilm formation was related to antimicrobial susceptibility but there were no statistically significant associations between the antimicrobial susceptibility and either the serovars or the ERIC-PCR clusters. This study showed a high prevalence of high-MICH. parasuisstrains and suggests the need for a continuous surveillance of clinical isolates ofH. parasuis.

Antibiotic resistance is an increasing concern for human and animal health worldwide. Recently, the concept of reverting bacterial resistance by changing the metabolic state of antibiotic-resistant bacteria has emerged. In this study, we investigated the reversal of Apramycin resistance in Salmonella. First, non-targeted metabonomics were used to identify key differential metabolites of drug-resistant bacteria. Then, the reversal effect of exogenous substances was verified in vivo and in vitro. Finally, the underlying mechanism was studied. The results showed that the metabolites citrulline and glutamine were significantly reduced in Apramycin-resistant Salmonella. When citrulline and glutamine were added to the culture medium of drug-resistant Salmonella, the killing effect of Apramycin was restored markedly. Mechanistic studies showed that citrulline and glutamine promoted the Tricarboxylic acid cycle, produced more NADH in the bacteria, and increased the proton-motive force, thus promoting Apramycin entry into the bacterial cells, and killing the drug-resistant bacteria. This study provides a useful method to manage infections by antibiotic-resistant bacteria.

The metabolic microenvironment of bacteria impacts drug efficacy. However, the metabolic mechanisms of drug-resistant Salmonella spp. remain largely unknown. This study characterized the metabolic mechanism of gentamicin-resistant Salmonella Choleraesuis and found that D-ribose increased the gentamicin-mediated killing of this bacteria. Non-targeted metabolomics of homologous gentamicin-susceptible Salmonella Choleraesuis (SCH-S) and gentamicin-resistant S. Choleraesuis (SCH-R) was performed using UHPLC-Q-TOF MS. The metabolic signature of SCH-R included disrupted central carbon metabolism and energy metabolism, along with dysregulated amino acid and nucleotide metabolism, vitamin and cofactor metabolism, and fatty acid synthesis. D-ribose, the most suppressed metabolite in SCH-R, was shown to strengthen gentamicin efficacy against SCH-R and a clinically isolated multidrug-resistant strain. This metabolite had a similar impact on Salmonella. Derby and Salmonella. Typhimurium. D-ribose activates central carbon metabolism including glycolysis, the pentose phosphate pathway (PPP), and the tricarboxylic acid cycle (TCA cycle), increases the abundance of NADH, polarizes the electron transport chain (ETC), and elevates the proton motive force (PMF) of cells, and induces drug uptake and cell death. These findings suggest that central carbon metabolism plays a critical role in the acquisition of gentamicin resistance by Salmonella, and that D-ribose may serve as an antibiotic adjuvant for gentamicin treatment of resistant bacterial infections.