Salmonella enterica Serovar Diversity, Distribution, and Prevalence in Public Access Waters from a Central California Coastal Leafy Green Growing Region during 2011 - 2016

Prevalence and serovar diversity of Salmonella enterica was measured during a five-year survey of surface waters in a 500 mi^2 agricultural region of the Central California Coast. Rivers, streams, lakes, and ponds were sampled bimonthly resulting in 2,979 samples. Overall prevalence was 56.4% with higher levels detected in Spring than in Fall. Small, but significant, differences in prevalence were detected based on sample locations. Detection of Salmonella was correlated positively with both significant rain events and, in some environments, levels of generic Escherichia coli . Analysis of 1,936 isolates revealed significant serovar diversity, with 91 different serovars detected. The most common isolated serovars were S. enterica subsp. enterica serovars I 6,8:d:- (406 isolates, 21.0%, and potentially monophasic Salmonella Muenchen), Give (334 isolates, 17.3%), Muenchen (158 isolates, 8.2%), Typhimurium (227 isolates, 11.7%), Oranienburg (106 isolates, 5.5%), and Montevideo (78 isolates, 4%). Sixteen of the 24 most common serovars detected in the region are among the serovars reported to cause the most human salmonellosis in the United States. Some of the serovars were associated with location and seasonal bias. Analysis of Xba I Pulsed Field Gel Electrophoresis (PFGE) patterns of strains of serovars Typhimurium, Oranienburg, and Montevideo showed significant intra-serovar diversity. PFGE pulsotypes were identified in the region for multiple years of the survey, indicating persistence or regular re-introduction to the region. Importance Non-typhoidal Salmonella is the among the leading causes of bacterial foodborne illness and increasing numbers of outbreaks and recalls are due to contaminated produce. High prevalence and 91 different serovars were detected in this leafy green growing region. Seventeen serovars that cause most of the human salmonellosis in the United States were detected, with 16 of those serovars detected in multiple locations and multiple years of the 5-year survey. Understanding the widespread prevalence and diversity of Salmonella in the region will assist in promoting food safety practices and intervention methods for growers and regulators.

Prevalence and Serotype Diversity of Salmonella enterica in the Estonian Meat Production Chain in 2016–2020

Background: Salmonella enterica represents a considerable public concern worldwide, with farm animals often recognised as an important reservoir. This study gives an overview of the prevalence and serotype diversity of Salmonella over a 5-year period in the meat production chain in Estonia. Data on human salmonellosis over the same period are provided. Methods: Salmonella surveillance data from 2016 to 2020 were analysed. Results: The prevalence of Salmonella at the farm level was 27.7%, 3.3% and 0.1% for fattening pigs, cattle and poultry, respectively. S. Derby was the most prevalent serotype at the farm level for fattening pigs and S. Dublin for cattle. The top three serotypes isolated at the slaughterhouse and meat cutting levels were S. Derby, monophasic S. Typhimurium and S. Typhimurium with proportions of 64.7%, 9.4% and 7.0%, respectively. These serotypes were the top five most common Salmonella serotypes responsible for human infections in Estonia. S. Enteritidis is the main cause (46.9%) of human salmonellosis cases in Estonia, but in recent years, Enteritidis has not been detected at the slaughterhouse or meat cutting level. Conclusion: In recent years, monophasic S. Typhimurium has become epidemiologically more important in Estonia, with the second-highest cause in human cases and third-highest among the most prevalent serotypes of Salmonella enterica in the meat chain.

Draft Genome Sequence of Salmonella enterica Serovar Enteritidis from Jos, Plateau State, Nigeria

Salmonella enterica serovar Enteritidis causes the highest incidence of human salmonellosis infections. Here, we describe the whole-genome sequence and annotation of Salmonella enterica serovar Enteritidis strain 1145s, isolated in Nigeria. The strain has a genome of 4.57 Mb with a GC content of 52% and contains one plasmid.

Prevalence, serovar, and antimicrobial resistance of Salmonella isolated from meat and minced meat used for production smoked sausage

The objective of this study was to research the prevalence, serovars, and antimicrobial resistance profiles of Salmonella isolated from meat and minced meat used for the production of fermented sausage. A total of 116 samples were tested, and among them, 20 (17.2%) were positive. Salmonella was detected in 3 (10.3%) beef samples, 5 (19.2%) pork samples, and 6 (20.7%) poultry samples. In minced meat, the Salmonella prevalence was 18.8%. Salmonella enterica serovar Agama (5.2%) was the most commonly identified serovar, followed by S. Enteritidis (4.3%), S. Typhimurium (3.4%), S. Infantis (2.6%), and S. Lindenburg (1.7%). Most of the serovars identified in the present study are recognized as frequent causes of human salmonellosis. Thus, the presence of these serovars means foods with these meats are a likely source of human infections. We found the Salmonella isolates exhibited high rates of resistance to antimicrobials tetracycline, ampicillin, streptomycin, and ciprofloxacin. The highest level of resistance was to tetracycline (75%), followed by resistance to ampicillin (50%), streptomycin (30%), ciprofloxacin (20%), gentamicin (20%), and neomycin (10%). The high-level resistance observed for some of the serovars calls for concern. Salmonella with multidrug resistance in meat used to produce fermented sausages is considered a high additional risk for human health.

Phenotypic and Genotypic Characterization of Salmonella spp. Isolated from Foods Involved in Human Salmonellosis Outbreaks in Minas Gerais State, Brazil

Salmonella spp. is one of the primary pathogens that cause foodborne diseases worldwide. In the present study, we deeply characterized Salmonella spp. originated from foods related to human salmonellosis outbreaks in Minas Gerais – Brazil, from 2003 to 2017. In this regard, the serotyping, antimicrobial susceptibility, virulence genes and genetic polymorphism determined by rep-PCR were performed in 70 Salmonella spp. isolates. Thirteen serotypes of Salmonella spp. were identified, and S. Enteritidis and S. Typhimurium were the most prevalent, both corresponding to 74.3% (52/70) of all isolates. Sixty-five (92.8%) isolates demonstrated to be resistant to at least one of the 15 antimicrobials tested. Ten isolates (14.2%) showed a multidrug-resistant phenotype. Sixteen virulence genes were screened and detection ranged from 75.7 to 100% of all isolates. There was a statistical difference among Salmonella spp. serotypes in detecting the sipB , sopE , lfpA , sefA and spvC genes. Forty isolates of S. Enteritidis from 16 outbreaks were grouped into 14 fingerprints, while 12 S. Typhimurium retrieved six fingerprints. The bacteria presented a serological pattern like those reported by main public health centers worldwide. One major concern of our findings is the high levels of both detection of virulence genes and resistance to antimicrobials, especially to critically important drugs. In this concern, especial attention should be given to the serotype S. Enteritidis. Although the isolates of Salmonella spp. have presented a relatively variable genome, high genetic similarity was observed among them, with some of them sharing identical fingerprints. These results corroborate the hypothesis of clonal circulation of Salmonella spp. in human infections in Minas Gerais.

Presence of plasmid-mediated quinolone resistance (PMQR) genes in non-typhoidal Salmonella strains with reduced susceptibility to fluoroquinolones isolated from human salmonellosis in Gyeonggi-do, South Korea from 2016 to 2019

Non-typhoidal salmonellosis remains a pressing public health problem worldwide. Quinolones, particularly fluoroquinolones, are widely used to treat various infections, including non-typhoidal salmonellosis, which can be a serious illness. The emergence of fluoroquinolone-resistant Salmonella has resulted in treatment failure and high mortality rates. In this study, we estimated the presence of plasmid-mediated quinolone resistance (PMQR) genes in Salmonella enterica isolated from human salmonellosis patients in South Korea from 2016 to 2019. We evaluated the association of these genes with fluoroquinolone susceptibility. Antimicrobial susceptibility tests for Salmonella isolates were performed using the Vitek II system, and the minimum inhibitory concentrations (MIC) of ciprofloxacin and levofloxacin were determined using the E-test method. Plasmid-mediated quinolone resistance (PMQR) genes were detected by PCR amplification and quinolone resistance-determining regions (QRDRs) of the gyrA and parC genes were analyzed following Sanger sequencing of the PCR products. Thirty-four Salmonella strains with reduced susceptibility to fluoroquinolones (ciprofloxacin MIC ≥ 0.125 µg/mL and levofloxacin MIC ≥ 0.25 µg/mL) were selected from 208 human clinical Salmonella isolates. Among them, 22 Salmonella strains harbored one PMQR gene (qnrA, qnrB, or qnrS), and three Salmonella strains carried two PMQR genes (qnrS and aac(6′)-Ib-cr or qnrA and qnrB). qnrS was the most common PMQR gene. Serotyping revealed that Salmonella 4,[5]12:i:- (32.4%, 11/34) and Salmonella Typhimurium (29.4%, 10/34) were the two most predominant serovars, and Multi-locus sequence typing (MLST) showed that ST19 and ST34 were the most frequent sequence types. In conclusion, qnr gene-positive Salmonella 4,[5],12:i:- and Salmonella Typhimurium were the main serovars responsible for reduced susceptibility to fluoroquinolones. Therefore, our findings suggest that PMQR-positive Salmonella strains, which can be isolated from various samples including human, food, and the environment, should be carefully monitored.

Integrative and Conjugative Element-Mediated Azithromycin Resistance in Multidrug-Resistant Salmonella enterica Serovar Albany

ABSTRACT We identified an erm42-carrying integrative and conjugative element, ICE_erm42, in 26.4% of multidrug-resistant Salmonella enterica serovar Albany isolates recovered from cases of human salmonellosis between 2014 and 2019 in Taiwan. ICE_erm42-carrying strains displayed high-level resistance to azithromycin, and the element could move into the phylogenetically distant species Vibrio cholerae via conjugation.

Impact of Salmonella Control Programmes in Poultry on Human Salmonellosis Burden in Greece

Since 2008, veterinary authorities in Greece have implemented national control programmes (NSCPs) targeting S. Enteritidis (SE) and S. Typhimurium (ST) in poultry. We assessed the effect of the programs on the reported number of human isolates. Using monthly data for 2006–2017, we defined two groups (SE, ST) and one control group with serotypes unrelated to poultry or eggs. For SE we also analysed data for 2006–2015 due to a multi-county SE outbreak in 2016. We performed an interrupted time series analysis and used a negative binominal regression model. For both SE and ST, there was no significant trend of the isolation rate before or after NSCPs’ introduction. After the NSCPs’ introduction there was an increasing rate (IRR: 1.005, 95% CI: 1.001–1.008) for control serotypes and a decreasing one for SE (IRR: 0.990, 95% CI: 0.986–0.995) (for 2009 to 2015 analysis). From 2006 to 2017, NSCPs had a statistically significant impact on the number of SE isolates that decreased by 49% (IRR:0.511, 95% CI: 0.353–0.739). No impact was shown on the number of ST (p-value = 0.741) and control isolates (p = 0.069). As a conclusion, NSCP’s implementation was associated with decreased SE isolates and overall burden of salmonellosis; however further measures aiming at human salmonellosis due to ST, should be considered.

Whole-Genome Sequencing Analysis of Salmonella Enterica Serotype Enteritidis Isolated from Poultry Sources in South Korea, 2010–2017

Salmonella enterica subsp. enterica serotype Enteritidis (SE) is recognized as a major cause of human salmonellosis worldwide, and most human salmonellosis is due to the consumption of contaminated poultry meats and poultry byproducts. Whole-genome sequencing (data were obtained from 96 SE isolates from poultry sources, including an integrated broiler supply chain, farms, slaughterhouses, chicken transporting trucks, and retail chicken meats in South Korea during 2010–2017. Antimicrobial resistance and virulence genes were investigated using WGS data, and the phylogenetic relationship of the isolates was analyzed using single-nucleotide polymorphism (SNP) typing and core genome multilocus sequence typing (cgMLST). All isolates carried aminoglycoside resistance genes, aac(6’)-Iaa, and 56 isolates carried multiple antimicrobial resistance genes. The most frequent virulence gene profile, pef-fim-sop-inv.-org-sip-spa-sif-fli-flg-hil-ssa-sse-prg-pag-spv, was found in 90 isolates. The SNP analysis provided a higher resolution than the cgMLST analysis, but the cgMLST analysis was highly congruent with the SNP analysis. The phylogenetic results suggested the presence of resident SE within the facility of processing plants, environments of slaughterhouses, and the integrated broiler supply chain, and the phylogenetically related isolates were found in retail meats. In addition, the SE isolates from different origins showed close genetic relationships indicating that these strains may have originated from a common source. This study could be valuable reference data for future traceback investigations in South Korea.