First report of liver abscess caused by Salmonella enterica serovar Dublin

Metabolome of purulent materials of liver abscesses from crossbred cattle and Holstein steers fed finishing diets with or without in-feed tylosin

Liver abscesses in feedlot cattle are a polymicrobial infection with Fusobacterium necrophorum and Trueperella pyogenes as the primary and secondary etiologic agents, respectively. Cattle with liver abscesses do not exhibit clinical signs and the abscesses are detected only at slaughter. The objective was to conduct metabolomics analysis of purulent materials of liver abscesses to identify biochemicals. Liver abscesses from crossbred cattle (n = 24) and Holstein steers (n = 24), each fed high-grain finishing diet with tylosin (n = 12) or no tylosin (n = 12), were included in the study. Abscess purulent materials were analyzed by ultrahigh-performance liquid chromatography-tandem mass spectroscopy. A total of 759 biochemicals were identified and were broadly categorized into carbohydrates, energy metabolism pathways intermediates, peptides, amino acids and their metabolites, lipids and their metabolites, nucleotides, vitamins and cofactors, xenobiotics, and partially characterized molecules. The top 50 biochemicals identified included amino acids, lipids, nucleotides, xenobiotics, peptides, and carbohydrates and their metabolites. Among the 15 amino acid metabolites in the top 50 biochemicals, four were tryptophan metabolites, indoleacrylate, indolepropionate, tryptamine, and anthranilate. The 3-phenylpropionate, a product of phenylalanine metabolism, was the predominant metabolite in purulent materials. Between the four treatment groups, a two-way ANOVA analysis identified biochemicals that exhibited significant main effects for cattle type and in-feed tylosin use and their interactions. A total of 59 and 85 biochemicals were different (P < 0.05) between the cattle type (crossbred vs. Holstein steers) and in-feed tylosin use (tylosin vs. no tylosin), respectively. Succinate, an intermediate of lactate fermentation by some bacterial species, was one of the top 30 biochemicals that differentiated the four treatment groups. A number of lysophospholipids, indicative of bacterial and host cell membrane lyses, were identified in the purulent materials. In conclusion, to our knowledge this is the first report on the metabolome of liver abscess purulent materials and several biochemicals identified were related to metabolic activities of the bacterial community, particularly F. necrophorum and T. pyogenes. Biochemicals unique to liver abscesses that appear in the blood may serve as biomarkers and be of diagnostic value to detect liver abscesses of cattle before slaughter.

Safety of the Salmonella enterica serotype Dublin strain Sdu189-derived live attenuated vaccine—A pilot study

Salmonella enterica serovar Dublin (S. Dublin) is an important zoonotic pathogen with high invasiveness. In the prevention and control of the Salmonella epidemic, the live attenuated vaccine plays a very important role. To prevent and control the epidemic of S. Dublin in cattle farms, the development of more effective vaccines is necessary. In this study, we constructed two gene deletion mutants, Sdu189ΔspiC and Sdu189ΔspiCΔaroA, with the parental strain S. Dublin Sdu189. The immunogenicity and protective efficacy were evaluated in the mice model. First, both mutant strains were much less virulent than the parental strain, as determined by the 50% lethal dose (LD₅₀) for specific pathogen-free (SPF) 6-week-old female BALB/c mice. Second, the specific IgG antibody level and the expression level of cytokine TNF-α, IFN-γ, IL-4, and IL-18 were increased significantly in the vaccinated mice compared to the control group. In addition, the deletion strains were cleared rapidly from organs of immunized mice within 14 d after immunization, while the parental strain could still be detected in the spleen and liver after 21 d of infection. Compared with the parental strain infected group, no obvious lesions were detected in the liver, spleen, and cecum of the deletion strain vaccinated groups of mice. Immunization with Sdu189ΔspiC and Sdu189ΔspiCΔaroA both provided 100% protection against subsequent challenges with the wild-type Sdu189 strain. These results demonstrated that these two deletion strains showed the potential as live attenuated vaccines against S. Dublin infection. The present study established a foundation for screening a suitable live attenuated Salmonella vaccine.

The first description of liver abscesses due to Salmonella enterica subsp. enterica in an African HIV-infected young woman: case report and review of the literature

Salmonella is Gram-negative bacilli that cause a foodborne infections. When the disease occurs in patients living with HIV (PLWHA), salmonellosis is an AIDS defining illness. Here we describe the case of a 26-year-old HIV-infected female patient who was hospitalized for pain in the right upper quadrant of the abdomen, and whose explorations revealed a liver abscess due to salmonella enterica enterica that progressed well after needle aspiration and antibiotic treatment.

Characterization of Salmonella Dublin isolated from bovine and human hosts

BACKGROUND

Salmonella enterica subsp. enterica serovar Dublin (S. Dublin), a cattle adapted serovar causes enteritis, and systemic disease in bovines. The invasive index of this serovar far exceeds that of the other serovars and human infections often present as fatal or highly resistant infections. In this, observational study, phenotypic properties of human and bovine-derived isolates of S. Dublin along with antibiogram of common antimicrobials were evaluated. The multiplex PCR confirmed isolates were genotyped using 7-gene legacy MLST. MIC assay was done by broth microdilution method. Previously published protocols were used to assess the motility, biofilm formation and morphotype. Vi antigen was agglutinated using commercial antiserum. Caenorhabditis elegans infection model was used to evaluate the virulence potiential. Phenotyping experiments were done in duplicates while virulence assay was done in triplicates. Whole-genome sequencing was used to predict the genes responsible for acquired resistance and a genotype-phenotype comparison was made.

RESULTS

We evaluated 96 bovine and 10 human isolates in this study. All the isolates belonged to ST10 in eBG53 and were negative for Vi-antigen. The swarming motility, biofilm formation and morphotype were variable in the isolates of both groups. Resistance to sulfamethoxazole, ampicillin, chloramphenicol, tetracycline was > 90% in animal isolates whereas resistance to sulfamethoxazole was > 70% in human isolates. MDR was also higher in animal isolates. Human isolates were significantly (P < 0.0001) more virulent than animal isolates on C. elegans infection model. The genomic comparison based on the core SNPs showed a high degree of homogeneity between the isolates. The carriage of IncA/C2 plasmid was seen as a typical feature of isolates from the bovine hosts.

CONCLUSION

Human isolates showed more diversity in the phenotypic assays. Animal isolates showed a higher degree of antimicrobial resistance with greater MDR but human isolates formed more biofilm and had greater swarming motility as well as increased virulence to the nematode C. elegans. The carriage of IncA/C2 plasmid could contribute to the distinguishing feature of the bovine isolates. The tandem use of genotypic-phenotypic assays improves the understanding of diversity and differential behaviour of the same serovar from unrelated host sources.

Salmonella typhimurium: a rare cause of mesh-related infection

The use of mesh in the management of abdominal wall hernias has significantly reduced the incidences of hernia recurrences. The placement of synthetic meshes to reinforce the abdominal wall is not without caveats. Synthetic meshes are associated with a risk of infection. Common causative microorganisms for mesh-related infection range from a diversity of gram positive, gram negative and anaerobic bacteria. However, non-typhoidal Salmonella spp. mesh-related infection remains poorly described in the literature. In this case, we report the management of an immunocompromised patient who developed Salmonella typhimurium mesh-related infection that was complicated by abscess formation.

Bacterial flora of liver abscesses in crossbred beef cattle and Holstein steers fed finishing diets with or without tylosin

Holstein steers raised for beef production consistently have a higher prevalence and more severe form of liver abscesses than cattle of beef breeds. A study was conducted to compare bacterial flora of liver abscesses collected from multiple abattoirs from 4 groups of cattle, arranged in a 2 × 2 factorial design, consisting of crossbred cattle and Holstein steers, and each group fed a finishing diet supplemented with or without tylosin. A total of 383 liver abscess samples, consisting of 94 and 81 from crossbred cattle and 89 and 119 from Holstein steers fed finishing diets with or without tylosin, respectively, were subjected for anaerobic and aerobic bacterial isolations. The minimum inhibitory concentrations (MIC) of tylosin to the predominant bacterial species were determined. The likelihood chi-square test was performed to assess unadjusted differences in bacterial prevalence proportions between the 2 types of cattle (crossbred and Holstein steers) and feed type (tylosin or no tylosin). There was no interaction between cattle type and tylosin inclusion on the prevalence of any of the bacterial species isolated. Liver abscesses from Holstein steers yielded a higher total number of isolates compared to liver abscesses from crossbred cattle (1060 vs. 788). subsp. was isolated from all abscesses. The prevalence of subsp. was 19.1% and was not affected by the cattle type or tylosin. The prevalence of was higher ( < 0.01) in crossbred cattle (73.7%) compared to Holstein steers (29.8%). Also, the prevalence of was higher in abscesses from tylosin-fed (66.1%) cattle than no tylosin-fed cattle (35%). The overall prevalence of was 25.3% and was similar ( = 0.58) between cattle type, but the prevalence was lower ( < 0.01) in tylosin-fed (16.9%) compared to no tylosin-fed group (33%). Mean MIC of tylosin for and were similar across both cattle types and tylosin inclusion. Although bacterial flora of liver abscesses from Holstein steers appeared to be more diverse than that of crossbred cattle, there was no difference in the prevalence of the and and in fact, prevalence of was higher in crossbred than Holstein steers. Therefore, the difference in bacterial flora is not the likely reason for higher prevalence and severity of liver abscesses in Holstein steers than crossbred beef cattle.