Vaccination Against Lawsonia intracellularis Decreases Shedding of Salmonella enterica serovar Typhimurium in Co-Infected Pigs and Alters the Gut Microbiome.

Salmonella enterica serovar Typhimurium continues to be a major cause of foodborne illness worldwide and pork can serve as a source of infection. Co-infection of S. enterica with Lawsonia intracellularis, a common intestinal pathogen of swine, has been found as risk factor for increased S. enterica shedding. The objective of this study was to investigate if vaccination against L. intracellularis could lead to decreased S. Typhimurium shedding. To test this hypothesis, pigs were challenged with either S. Typhimurium or S. Typhimurium and L. intracellularis, with and without L. intracellularis vaccination (n = 9 per group). A non-challenged group served as a negative control. Vaccination decreased the shedding of S. Typhimurium in co-infected animals by 2.12 log10 organisms per gram of feces at 7 days post infection. Analysis of the microbiome showed that vaccination led to changes in the abundance of Clostridium species, including Clostridium butyricum, in addition to other compositional changes that may explain the protection mediated against S. Typhimurium. These results indicate that vaccination against L. intracellularis in co-infected herds may provide a new tool to increase food safety by helping to prevent S. enterica without the need for antibiotics.

Perfil fenotípico e susceptibilidade antimicrobiana de Streptococcus equi isolados de equinos da região Sul do Brasil / Phenotypic profile and antimicrobial susceptibility of Streptococcus equi isolated from horses in southern Brazil

As características fenotípicas [morfológicas, bioquímicas, susceptibilidade aos antimicrobianos, índice de resistência múltipla aos antimicrobianos (IRMA), concentração inibitória mínima (CIM) e concentração bactericida mínima (CBM) da benzilpenicilina] de 38 isolados de Streptococcus equi oriundos de amostras clínicas de animais com adenite equina foram alvo deste estudo. A fenotipia demonstrou três padrões de colônias, três biotipos de fermentação de carboidratos e variação de 0 a 0,4 no IRMA. Todos os isolados de S. equi demonstraram sensibilidade à penicilina, tanto pelo método de disco difusão quanto pelo método de microdiluição. A CIM e CBM média de benzilpenicilina foi de 0,0095μg/mL e 0,0267μg/mL para S. equi subesp. equi e de 0,0128μg/mL e 0,0380μg/mL para S. equi subesp. zooepidemicus. Os valores de CIM e CBM diferiram entre as subespécies (p<0,05). O diâmetro do halo de inibição de penicilina demonstrou relação com a CIM (ì=0,03638 - 0,00072x) para S. equi subesp. equi. Também foi demonstrada relação entre o diâmetro do halo de inibição de penicilina com a CBM para S. equi subesp. equi (ì=0,10931- 0,00223x). Entretanto para as amostras de S. equi subesp. zooepidemicus esta relação somente foi verificada para a CBM (ì=0,1322 - 0,00271x). A CIM de benzilpenicilina frente às amostras isoladas da região Central, Planalto e Sul do estado do Rio Grande do Sul foram estatisticamente semelhantes, mas diferiram do isolado do estado do Paraná, sugerindo o caráter atípico desta cepa. Todos os isolados de S. equi são sensíveis à penicilina e sulfazotrim, confirmando a eleição destes antimicrobianos para o tratamento das infecções por este agente na clínica veterinária. Os resultados obtidos não dispensam a utilização prudente dos antimicrobianos.

Phenotypic characteristics [morphology, biochemical fermentation, antimicrobial susceptibility, index of multiple resistances to antimicrobials (IMRA), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of benzilpenicillin] of 38 Streptococcus equi isolates from clinical samples of horses with strangles were the aim of this study. The phenotypic analyses demonstrated three colony patterns, three carbohydrate fermentation biotypes and IMRA variation from 0 to 0.4. All the isolates of S. equi demonstrated sensitivity to penicillin, both by the disc diffusion method and microdilution method. The average MIC and MBC for benzilpenincillin were of 0.0095μg/mL and 0.0267μg/mL for S. equi subsp. equi and of 0.0128μg/mL and 0.0380μg/mL for S. equi subsp. zooepidemicus. The values of MIC and MBC differed between the subspecies (p<0.05). The diameter of penicillin inhibition halo demonstrated a relation with the MIC (ì=0.03638 - 0.00072x) for Streptococcus equi subsp. equi. A relation between the diameter of the inhibition halo of penincillin was also observed with the MBC for S. equi subsp. equi (ì=0.10931 - 0.00223x). However for the samples of S. equi subsp. zooepidemicus this relation was only verified with the MBC (ì=0.1322 - 0.00271x). The MIC of benzilpenicillin of the samples isolated from the Central, Planalto and South regions of Rio Grande do Sul were statistically similar, although different from the Paraná state sample, suggesting the atypical character of this strain. All the S. equi isolates are sensitive to penicillin and sulfazotrim, confirming these as antibiotics of choice for the treatment of infections caused by this agent in the clinical veterinary practice. The results obtained do not discard the prudent use of antimicrobials.