Epidemiological characteristics of Salmonella Typhimurium isolated from animals and feed in Poland

Occurrence, antimicrobial resistance and whole genome sequence analysis of Salmonella serovars from pig farms in Ilorin, North-central Nigeria

Salmonella enterica is a foodborne pathogen of global public health importance with developing countries mostly affected. Foodborne outbreaks are often attributed to pork consumption and Salmonella contamination of retail pork is directly linked to the Salmonella prevalence on farm. The widespread use of antimicrobials at different steps of swine production can favor resistant strains of Salmonella. The objectives of this study are to characterize the distribution, multilocus sequence typing (MLST), plasmid, virulence profiles and antimicrobial resistance of Salmonella serovars circulating in selected pig farms. Six hundred fecal samples were randomly collected from nine selected farms in Ilorin, Nigeria. Isolates were analyzed by cultural isolation using selective media, conventional biochemical characterization, serotyping, MLST and whole genome sequencing (WGS). Sixteen samples were positive for Salmonella sub-species, comprising of nine serovars. The antimicrobial susceptibility results revealed low-level resistance against 13 antimicrobial agents. Five strains exhibited resistance to nalidixic acid and intermediate resistance to ciprofloxacin with chromosomal (double) mutation at gyrA and parC while four strains possessed single mutation in parC. Salmonella Kentucky showed double mutation each at gyrA and parC. WGS analysis, revealed eight diverse sequence types (STs), the most common STs were ST-321 and ST-19 (n = 4) exhibited by S. Muenster and S. Typhimurium, respectively. Single Nucleotide Polymorphism (SNP)-based phylogeny analysis showed the 16 isolates to be highly related and fell into 8 existing clusters at NCBI Pathogen Detection. Curtailing the spread of resistant strains will require the establishment of continuous surveillance program at the state and national levels in Nigeria. This study provides useful information for further studies on antimicrobial resistance mechanisms in foodborne Salmonella species.

The Protective Effect of E. faecium on S. typhimurium Infection Induced Damage to Intestinal Mucosa

Intensive farming is prone to induce large-scale outbreaks of infectious diseases, with increasing use of antibiotics, which deviate from the demand of organic farming. The high mortality rate of chickens infected with Salmonella caused huge economic losses; therefore, the promising safe prevention and treatment measures of Salmonella are in urgent need, such as probiotics. Probiotics are becoming an ideal alternative treatment option besides antibiotics, but the effective chicken probiotic strains with clear protective mechanism against Salmonella remain unclear. In this study, we found Enterococcus faecium YQH2 was effective in preventing Salmonella typhimurium infection in chickens. Salmonella typhimurium induced the loss of body weight, and liver and intestinal morphology damage. The inflammatory factor levels increased and intestinal proliferation inhibited. However, after treatment with Enterococcus faecium YQH2, broilers grew normally, the pathological changes of liver and intestine were reduced, and the colonization of Salmonella in the intestine was improved. Not only that, the length of villi and the depth of crypts were relatively normal, and the levels of inflammatory factors such as IL-1β, TNF-α, and IL-8 were reduced. The number of PCNA cells of Enterococcus faecium YQH2 returned to normal under the action of Salmonella typhimurium infection, which was conducive to the normal proliferation of intestinal epithelial cells. The protective effect of Enterococcus faecium YQH2 may be due to the attribution to the activation of hypoxia and then induced the proliferation of intestinal stem cells to repair the damage of intestinal mucosa under Salmonella typhimurium infection. This study demonstrated that Enterococcus faecium YQH2 was effective in preventing Salmonella typhimurium infection, which could be further used in the chicken health breeding.

Identification and Characterization of Salmonella Serovars Isolated from Pig Farms in Benin City, Edo State, Nigeria: One Health Perspective

The present study was carried out to characterize Salmonella serovars from commercial pig farms in Benin City, Nigeria. A total of 81 samples were collected from the Agricultural Development Program farms between January and June 2017. Standard culture-based and polymerase chain reaction procedures were adopted in the isolation and identification of Salmonella serovars. Antibiotic susceptibility profiles of the isolates were conducted using the Kirby-Bauer disc diffusion method with prominent resistance determinants screened for using specific primer sets. The 84 identified Salmonella serovars include 15 Salmonella ser. Enteritidis, 11 Salmonella ser. Typhimurium, and 58 other Salmonella serovars. Phenotypic virulence factors include: hemolytic activity (51.7-100%), lipase activity (48.3-81.8%), protease activity (60.3-100%), gelatinase production (50-90.9%), DNA degrading activity (55.2-90.9%), and S-layer formation (63.8-100%). The biofilm formation profiles include nonbiofilm producers (0-12.1%), weak biofilm producers (0-20%), moderate biofilm producers (24.1-27.3%), and strong biofilm producers (48.3-72.7%). Salmonella serovars in this study harbored resistant determinants, such as tetA, tetC, ampC, sul1, sul2, sul3, floR, ermA, and ermC. The occurrence of resistance phenotype and determinants in pathogenic Salmonella serovars from pig farms is a significant public health concern, which could result in the dissemination of resistant elements within the environment.

Landscape of ROD9 Island: Functional annotations and biological network of hypothetical proteins in Salmonella enterica

Salmonella, an Enterobacteria is a therapeutically important pathogen for the host. The advancement of genome sequencing of S. enterica serovar Enteritidis have identified a distinct ROD9 pathogenic island, imparting virulence. The occurrence of 17 ROD9 hypothetical proteins, necessitates subsequent bioinformatics approach for structural and functional aspects of protein-protein relations or networks in different pathogenic phenotypes express. A collective analysis using predictive bioinformatics tools that includes NCBI-BLASTp and BLAST2GO annotated the motif patterns and functional significance. The VFDB identified 10 virulence proteins at both genomic and metagenomic level. Phylogenetic analysis revealed a divergent and convergent relationship between 17 ROD9 and 41 SP-1 proteins. Here, combining a comprehensive approach from sequence based, motif recognitions, domain identification, virulence ability to structural modelling provides a precise function to ROD9 proteins biological network, for which no experimental information is available.

Long-term dissemination of CTX-M-5-producing hypermutable Salmonella enterica serovar typhimurium sequence type 328 strains in Russia, Belarus, and Kazakhstan

In this paper, we present evidence of long-term circulation of cefotaxime-resistant clonally related Salmonella enterica serovar Typhimurium strains over a broad geographic area. The genetic relatedness of 88 isolates collected from multiple outbreaks and sporadic cases of nosocomial salmonellosis in various parts of Russia, Belarus, and Kazakhstan from 1996 to 2009 was established by multilocus tandem-repeat analysis (MLVA) and multilocus sequence typing (MLST). The isolates belong to sequence type 328 (ST328) and produce CTX-M-5 β-lactamase, whose gene is carried by highly related non-self-conjugative but mobilizable plasmids. Resistance to nalidixic acid and low-level resistance to ciprofloxacin is present in 37 (42%) of the isolates and in all cases is determined by various single point mutations in the gyrA gene quinolone resistance-determining region (QRDR). Isolates of the described clonal group exhibit a hypermutable phenotype that probably facilitates independent acquisition of quinolone resistance mutations.

Development of rapid detection and genetic characterization of salmonella in poultry breeder feeds

Salmonella is a leading cause of foodborne illness in the United States, with poultry and poultry products being a primary source of infection to humans. Poultry may carry some Salmonella serovars without any signs or symptoms of disease and without causing any adverse effects to the health of the bird. Salmonella may be introduced to a flock by multiple environmental sources, but poultry feed is suspected to be a leading source. Detecting Salmonella in feed can be challenging because low levels of the bacteria may not be recovered using traditional culturing techniques. Numerous detection methodologies have been examined over the years for quantifying Salmonella in feeds and many have proven to be effective for Salmonella isolation and detection in a variety of feeds. However, given the potential need for increased detection sensitivity, molecular detection technologies may the best candidate for developing rapid sensitive methods for identifying small numbers of Salmonella in the background of large volumes of feed. Several studies have been done using polymerase chain reaction (PCR) assays and commercial kits to detect Salmonella spp. in a wide variety of feed sources. In addition, DNA array technology has recently been utilized to track the dissemination of a specific Salmonella serotype in feed mills. This review will discuss the processing of feeds and potential points in the process that may introduce Salmonella contamination to the feed. Detection methods currently used and the need for advances in these methods also will be discussed. Finally, implementation of rapid detection for optimizing control methods to prevent and remove any Salmonella contamination of feeds will be considered.

Phenotypic and genetic characterization of Salmonella enterica subsp. enterica serovar Typhimurium isolated from pigs in Rio Grande do Sul, Brazil

This study aimed to investigate the relatedness of porcine Salmonella enterica subsp. enterica (S.) serovar Typhimurium strains isolated in Southern Brazil. Sixty-six isolates from pigs belonging to three commercial companies were submitted to phage typing, XbaI-macrorestriction (PFGE), IS200 hybridization, rep-PCR, antimicrobial susceptibility testing, and PCR assay targeting the spvR region. All strains presented a unique rep-PCR pattern and 63 strains had a common IS200 profile. One pulse-type (XA) was the most prevalent (39/66 strains) and included strains of phage types DT177, DT192, DT194 and RDNC. The spvR region was detected in three strains, which harboured plasmids of 90 kb. High rates of tetracycline, sulfonamide and streptomycin resistance were found. Isolates from farms located in different geographic regions but associated to the same commercial companies clustered together and presented a common resistance profile. Results suggested that clonal groups of S. Typhimurium are present in pig commercial companies in Southern Brazil.