Selection of Multidrug-Resistant Enterobacteria in Weaned Pigs and Its Association With In-feed Subtherapeutic Combination of Colistin and Tylosin.

In-feed antibiotics are administered to piglets to improve performance and production efficiency. However, the use of growth promoters in the swine industry can select for multidrug-resistant (MDR) bacteria. Here, we evaluate the resistance profile of enterobacteria isolated from fecal samples of weaned pigs (21-35 days) fed or not with antibiotics (colistin and tylosin) and investigated the piglets gut microbiota in both groups. Six hundred and eighteen bacterial cultures were isolated from the control group (CON; n = 384) and antibiotic-fed pigs (ATB; n = 234). All isolates were tested for resistance to 12 antibiotics belonging to six distinct antibiotic classes. Isolates were highly resistant to ampicillin (90%; n = 553), amoxicillin (85%; n = 525), and tetracycline (81%; n = 498). A significant increase (P < 0.05) in resistance to cephalexin, kanamycin, doxycycline, and colistin was observed for bacteria from the ATB group. Piglets allocated in the ATB and CON groups shared similar intestinal microbiota, as revealed by alpha- and beta-diversity analyses. Our findings demonstrate that colistin and tylosin contribute to select MDR enterobacteria in weaned piglets. The high frequency of antibiotic resistance among isolates from the CON group suggests that environmental sources (e.g., fecal contents, aerosols, soil, water, food) also represent a potential reservoir of multidrug-resistant enterobacteria in pig production systems.

Retrospective whole-genome comparison of Salmonella enterica serovar Enteritidis from foodborne outbreaks in Southern Brazil.

Salmonella enterica serovar Enteritidis is frequently isolated from animal-source foods associated with human salmonellosis outbreaks. This serovar was spread to animal (mainly poultry) farms worldwide in the 1980s, and it is still detected in foods produced in many countries, including Brazil. The present study reports a retrospective genome-wide comparison of S. Enteritidis from foodborne outbreaks in Southern Brazil in the last two decades. Fifty-two S. Enteritidis isolates were obtained from foodborne outbreaks occurring in different cities of the Brazilian southernmost State, Rio Grande do Sul (RS), from 2003 to 2015. Whole-genome sequences (WGS) from these isolates were obtained and comparatively analyzed with 65 additional genomes from NCBI. Phylogenetic and Bayesian analyses were performed to study temporal evolution. Genes related to antibiotic resistance and virulence were also evaluated. The results demonstrated that all S. Enteritidis isolates from Southern Brazil clustered in the global epidemic clade disseminated worldwide originally in the 1980s. Temporal analysis demonstrated that all Brazilian isolates had a tMRCA (time to most recent common ancestor) in 1986 with an effective population size (Ne) increase soon after until 1992, then becoming constant up to now. In Southern Brazil, there was a significant decrease in the spreading of S. Enteritidis in the last decade. In addition, three antibiotic resistance genes were detected in all isolates: aac(6')-Iaa, mdfA, and tet(34). These results demonstrate the high frequency of one only specific S. Enteritidis lineage (global epidemic clade) in foodborne outbreaks from Southern Brazil in the last two decades.

Nutritive value and fermentation quality of palisadegrass and stylo mixed silages.

The nutritive value and fermentation quality of palisadegrass (Brachiaria brizantha cv. Xaraes) and stylo (Stylosanthes capitata × S. macrocephala cv. Campo Grande) mixed silages were evaluated. The experiment was analyzed in a factorial scheme (5 × 2) in a completely randomized design using increasing levels of stylo (0, 25, 50, 75 and 100% on a fresh matter basis) on palisadegrass silages, with and without microbial inoculants (MI). With the increased ratio of stylo in mixed silages, dry matter (DM), crude protein (CP), acid detergent fiber (ADF), and lignin content increased in silages. The presence of MI promoted lower DM content, and higher neutral detergent fiber corrected for ash and protein, ADF and lignin content. The acid detergent insoluble nitrogen content and the lactic acid bacteria populations were not affected by treatments. The in vitroDM digestibility was affected by the interaction of levels of the stylo and MI. The pH, NH3 -N/total nitrogen and butyric acid concentrations decreased with increasing levels of stylo. Better nutritive value and quality of fermentation was found in the silage containing higher proportions of this stylo mixed with palisadegrass. The microbial inoculant evaluated did not alter the nutritive value or quality of the fermentation of the silages in this experiment.