A 28-d experiment evaluated the growth performance, acute-phase response, and bacterial shedding patterns in pigs (n = 108; initially, 38.7 ± 6.7 kg) fed 6 treatment diets, including a control diet with no antimicrobial agents (CON), a positive control diet containing chlortetracycline, 100 mg/kg (CT), a diet containing anti-Salmonella Typhimurium bacteriophage, 3 × 10(9) plaque-forming units/kg of feed (ASB), Lactobacillus plantarum CJLP56, 6.5 × 10(8) cfu/kg of feed (LP), 0.2% microencapsulated organic acids (MOA), or 5% fermented soybean meal (FSM). Pigs were fed the diets for 2 wk before and 2 wk after challenging orally with Salmonella enterica serotype Typhimurium (SalT). Before bacterial challenge, ADFI was similar in all groups. After SalT challenge, ADFI of CON pigs was less (P < 0.05) than all other groups. Before challenge, pigs on MOA, FSM, and CT diets had greater (P < 0.05) ADG and G:F than CON pigs. After challenge (wk 3 to 4) and during the overall experimental period (wk 1 to 4), ADG of all treatment groups and G:F of all treatment groups except the LP group were greater (P < 0.05) than those of CON pigs. Relative to all other treatments, CON and LP pigs had greater (P < 0.05) bacterial shedding scores on d 7 after SalT challenge. At d 14 postchallenge, shedding scores declined (P < 0.05) in all treatment groups compared with CON pigs. Serum haptoglobin for all treatment groups increased from d 0 concentrations on d 6 postchallenge and declined to prechallenge concentrations on d 13 (P < 0.05). Circulating IGF-I concentrations declined from 2 to 6 d postchallenge and increased again by d 13 in ASB and LP groups, did not decline in FSM and CT groups, and continuously declined through d 13 in CON and LP groups (P < 0.05). However, in MOA group, IGF-I concentrations declined from preinfection concentrations on d 2, increased on d 4, and declined again until d 13 (P < 0.05). The serum concentrations of the cytokines IL-6 and IL-1β were not generally affected by SalT challenge. In conclusion, acute infection of growing pigs with SalT was associated with short-term febrile responses in most pigs and reductions in ADFI and ADG of CON pigs. Compared with the CON diet, ASB, FSM, and MOA diets had a similar benefit to the antibiotic-supplemented diet in improving the performance of growing pigs, especially after bacterial challenge. However, further work needs to be done to better understand their mode of action in this class of pigs.
The antibacterial activity and selection of resistant bacteria, along with mechanisms of fluoroquinolone resistance, were investigated by integrating the static [MIC or mutant-prevention concentration (MPC)] and in vitro dynamic model approaches using Escherichia coli isolates from diseased dogs. Using the dynamic models, selected E. coli strains and enrofloxacin and marbofloxacin at a range of simulated area under concentration-time curve over a 24 h interval (AUC 24 h )/MIC ratios were investigated. Our results indicated increasing losses in susceptibility of E. coli upon continuous exposure to enrofloxacin and marbofloxacin in vitro. This effect was transferable to other fluoroquinolones, as well as to structurally unrelated drugs. Our results also confirmed an AUC 24 h /MIC (AUC 24 h /MPC)-dependent antibacterial activity and selection of resistant E. coli mutants, in which maximum losses in fluoroquinolone susceptibility occurred at simulated AUC 24 h /MIC ratios of 40-60. AUC 24 h /MPC ratios of 39 (enrofloxacin) and 32 (marbofloxacin) were considered protective against the selection of resistant mutants of E. coli. Integrating our MIC and MPC data with published pharmacokinetic information in dogs revealed a better effect of the conventional dosing regimen of marbofloxacin than that of enrofloxacin in restricting the selection of resistant mutants of E. coli. Target mutations, especially at codon 83 (serine to leucine) of gyrA, and overexpression of efflux pumps contributed to resistance development in both clinically resistant and in vitro-selected mutants of E. coli. We also report here a previously undescribed mutation at codon 116 of parC in two laboratory-derived resistant mutants of E. coli. Additional studies would determine the exact role of this mutation in fluoroquinolone susceptibility, as well as establish the importance of our findings in the clinical setting.
Summary Although various biological activities of Phellinus gilvus (PG) have been reported, the active compounds responsible for these effects are not known. Here, we evaluated the activity of various solvent extracts of PG, and found the ethyl acetate extract (Fd) to be the most active fraction, showing a strong DPPH free radical scavenging activity, and inhibitory effects on LPS-induced nitric oxide (NO) production and COX-2 mRNA expression in RAW264.7 macrophages. Six major compounds were identified from the ethyl acetate extract of PG, and protocatechualdehyde (PCA) was supposed to be the major phenolic compound of PG responsible for its DPPH free radical scavenging activity and its inhibitory effects on LPS-induced NO production in RAW264.7 cells. Further in vitro and in vivo experiments are currently underway to confirm this observation and to investigate the detailed molecular mechanisms involved in the process as well as the biological activities of other fractions of Fd. Key Words Phellinus gilvus , protocatechualdehyde, DPPH, NO, RAW264.7 cellsPhellinus gilvus (PG) is a medicinal mushroom belonging to Hymenochaetaceae basidiomycetes , and has advantages over many Phellinus species due to its short growth period (3 mo), making it cheaper to produce ( 1-3 ). Previous studies in our laboratory and by other investigators have established various biological activities of PG. Among the reported benefits of PG are inhibition of pulmonary inflammation, prevention of intraperitoneal adhesion under infectious circumstances, promotion of dermal wound healing, anti-platelet aggregation and antitumor activities ( 1-4 ). In a previous study with various solvent extracts of PG, we have demonstrated marked DPPH free radical scavenging and xanthine oxidase (XO)-inhibitory activities of the ethyl acetate extract of PG, along with the enhancement of cellular immunity by hot water extracts of PG and inhibition of thrombin-induced platelet aggregation by chloroform-, methanol-and butanol extracts of PG ( 3 ). In the current investigation, we determined the major components of the ethyl acetate extract of PG responsible for its biological activities and further compared the magnitude of the antioxidant/anti-inflammatory activities of components with the various fractional extracts of PG.The fruiting body of PG was provided by Gyeongbuk Agriculture Technology Administration (Daegu, Korea). The preparation of PG fractional extracts was reported earlier ( 3 ). Briefly, fruiting bodies of the mushroom were cut into small pieces and dried at 40-50˚C for 48 h. The pieces were homogenized, extracted with water (1 : 25) at 100˚C for 10 h, and the aqueous phase (Fa) concentrated at 80˚C in a rotary evaporator (Büchi Rotavapor R-114, Switzerland) and the final volume reduced to 1/10 of the initial volume. The Fa was then mixed with 95% ethanol (1 : 3, v/v) and stored at 4˚C overnight. The solution was then centrifuged at 15,000 ϫ g for 30 min, the precipitate dialyzed (1 : 100,000) in water, filtered, centrifuged, re-dissolved and ly...
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