Whole-genome sequencing and phylogenetic analysis capture the emergence of a multi-drug resistant Salmonella enterica serovar Infantis clone from diagnostic animal samples in the United States

Whole genome sequencing of Salmonella serovars isolated from organic and non-organic whole broiler carcasses on the eastern shore of Maryland, USA

Multidrug-resistant Salmonella is becoming a public health hazard. This study aimed to investigate the genomic diversity of the selected Salmonella serovars isolated from organic and non-organic chickens using whole-genome sequencing (WGS). A total of 94 Salmonella isolates [Infantis (n = 71), Enteritidis (n = 13), Typhimurium (n = 10)] recovered from organic and non-organic retail chickens were subjected to WGS using Illumina MiSeq. All Salmonella isolates contained at least one antibiotic resistance (AR) gene (ARG). All S. Typhimurium and S. Enteritidis isolates, and 98.6 % of S. Infantis isolates possessed aac(6')-Iaa which predicted resistant to aminoglycosides. Most isolates harbored ARGs for sulfonamides, β-lactamase inhibitors, tetracyclines, and fluoroquinolone/quinolone resistance regardless of chicken types. Fisher's exact test indicated a significantly higher prevalence of ARGs in Salmonella isolated from organic chickens. The virulence genes that stimulate Salmonella pathogenicity island 1 (SPI1) encoding, type three secretion system 1 (TTSS-1) translocated effectors, SPI2 encoding, TTSS-2 translocated effectors, fimbrial adherence determinants, serum resistance, stress adaptation and Mg2+ uptake were observed in every serovar regardless of chicken types. Seven plasmids were detected in Salmonella isolates from non-organic chicken, including IncFIB(pN55391), IncFIB(S), Col(BS512), IncFII(S), IncX1, IncC, and ColpVC, whereas Salmonella isolates from organic chicken carried only three plasmids [IncFIB(pN55391), Col(BS512), and IncC]. Phylogenetic analysis confirmed that a significant portion of the isolates had single nucleotide polymorphism (SNP) distances greater than the threshold (SNP ≤ 20), indicating genetic distance among them. These results suggest that the Salmonella isolates from organic and non-organic chickens possessed various AR and virulence genes and thus have the potential to cause salmonellosis.

Unveiling the prevalence of metal resistance genes and their associations with antibiotic resistance genes in heavy metal-contaminated rivers

Heavy metals can drive antibiotic resistance through co-selection mechanisms. Current knowledge predominantly focuses on relationships between metal resistance genes (MRGs) and antibiotic resistance genes (ARGs) at the river reach scale. It remains unclear the links between MRGs and ARGs at the large river basin scale, as does the role of MRG-ARG colocalization in resistance dissemination. This study employed metagenomics to investigate the prevalence of MRGs in the Xiangjiang River, a historically heavy metal-contaminated river, and their connections with ARGs by combining resistome profiling with colocalization analyses. Results revealed the significant prevalence of MRGs in the river compared to nationwide rivers, but it showed weak correlations with metal concentrations in either water or sediment. The prevalence of MRGs in water was weakly driven by abiotic parameters, but was strongly influenced by microbial composition. The proportion of water MRGs attributable to sewage sources was tightly positively correlated with MRG abundances, suggesting the significant contribution of external waste input. Plasmid-originated MRGs were more abundant in water, while chromosomal MRGs dominated in sediment, indicating medium-specific transfer dynamics. The profile of MRGs were strongly correlated with that of ARGs in both media, encompassing several clinically high-risk ARGs. However, MRG-ARG colocalization events were rarely detected (eight instances in total), consistent with low frequencies in nationwide rivers (3.5 % in sediment; 2.0 % in water), implying their limited roles in resistance dissemination. Overall, the findings enhance our understanding of riverine metal resistome and its associations with antibiotic resistome, while emphasize the rare presence of MRG-ARG colocalization in riverine environments.

Monitoring antimicrobial resistance in Salmonella enterica serovar Infantis isolates of poultry, livestock, and humans across the United States, 2013-2020

Salmonella enterica serovar Infantis (S. Infantis) is an emerging zoonotic foodborne pathogen. This study used publicly available data on S. Infantis from the National Antimicrobial Resistance Monitoring System (NARMS) to evaluate the prevalence and antimicrobial resistance (AMR) of S. Infantis across the United States of America between 2013 and 2020. The highest prevalence of S. Infantis was identified in chickens (3027 isolated from 18,078 samples; 16.75 %), swine (431/5600; 6.09 %), turkeys (161/4019; 4.01 %), humans (737/18,774; 3.93 %), and cattle (134/8010; 1.67 %). Over the study period, a significant increase in S. Infantis isolates of chickens and turkeys, a moderate in cattle, a low in humans, and no increase in swine was observed. High resistance to tetracycline, nalidixic acid, and sulfisoxazole and low resistance to cefoxitin and amoxicillin-clavulanic acid were detected among livestock, poultry, and human isolates. Reduced susceptibility to ciprofloxacin was observed in 52.46 % of chicken isolates, 62.11 % of turkey, and 18.59 % of human isolates. Multi-drug resistance (MDR; resistant to at least one agent in ≥3 antimicrobial classes) was detected in 93 % of turkeys, 83 % of chickens, 22 % of humans, 16 % of cattle, and 6 % of swine isolates. This study identified differences in the prevalence and AMR of S. Infantis across the food chain, highlighting the importance of a focused One Health approach to mitigate the emergence of AMR and to reduce the health burden of infections with drug-resistant isolates.

Phenotypic and genotypic characterization of antimicrobial resistance and virulence profiles of Salmonella enterica serotypes isolated from necropsied horses in Kentucky

Salmonella is a foodborne pathogen that poses a significant threat to global public health. It affects several animal species, including horses. Salmonella infections in horses can be either asymptomatic or cause severe clinical illness. Infections caused by Salmonella are presently controlled with antibiotics. Due to the formation of biofilms and the emergence of antimicrobial resistance, the treatment has become more complicated. Our study focused on investigating the prevalence of Salmonella enterica in necropsied horses, assessing the capability for biofilm formation, and motility, determining the phenotypic and genotypic profiles of antibiotic resistance, and detecting virulence genes. A total of 2,182 necropsied horses were tested for the presence of Salmonella. Intestinal samples were enriched in selenite broth and cultured on hektoen and eosin methylene blue agar plates, whereas other samples were directly cultured on aforementioned plates. Confirmation of the serotypes was performed according to the Kauffmann-White-Le Minor Scheme followed by biofilm formation screening using crystal violet assay. The resistance profile of the isolates was determined by broth microdilution assay using the Sensititre️ Vet (Equine EQUIN2F). The genotypic antimicrobial resistance (AMR) and virulence profiles were detected using polymerase chain reaction (PCR). The overall prevalence of Salmonella was 1.19% (26/2182), with 11 different serotypes identified. Salmonella Typhimurium was the most prevalent serotype with 19.2% prevalence. All of the isolates were identified as biofilm producers and motile. Virulence genes related to invasion (invA, hilA, mgtC, and spiA), biofilm formation (csgA and csgB), and motility (filA, motA, flgG, figG, flgH, fimC, fimD, and fimH) of Salmonella were detected among 100% of the isolates. An overall 11.4% of the isolates were identified as multidrug-resistant (MDR), with resistance to gentamicin, amikacin, ampicillin, ceftazidime, ceftiofur, chloramphenicol, and trimethoprim/sulfamethoxazole. We found that beta-lactamase-producing genes blaTEM, blaCTXM, and blaSHV2 were identified in 11.5% of the isolates, while only 3.8% carried the blaOXA-9 gene. The presence of MDR pathogenic Salmonella in horses is alarming for human and animal health, especially when they have a high affinity for forming biofilm. Our study found horses as potential sources of pathogenic Salmonella transmission to humans. Thus, it is important to perform continuous monitoring and surveillance studies to track the source of infection and develop preventive measures.

IMPORTANCE

This study focuses on understanding how Salmonella, specifically isolated from horses, can resist antibiotics and cause disease. Salmonella is a well-known foodborne pathogen that can pose risks not only to animals but also to humans. By studying the bacteria from necropsied horses, the research aims to uncover how certain Salmonella strains develop resistance to antibiotics and which genetic factors make them more dangerous. In addition to antibiotic resistance, the research explores the biofilm-forming ability of these strains, which enhances their survival in harsh environments. The study also investigates their motility, a factor that contributes to the spread of infection. The findings can improve treatment strategies for horses and help prevent the transmission of resistant bacteria to other animals as well as humans. Ultimately, the research could contribute to better management of antibiotic resistance in both veterinary and public health contexts, helping to safeguard animal welfare and public health.

Salmonella Infantis outbreak on six broiler units in Great Britain: investigation, epidemiology, and control

AIMS

To describe the analysis, epidemiology, and control of six contemporaneous and linked outbreaks of Salmonella enterica subsp. enterica serovar Infantis on British broiler farms. Salmonella Infantis is a potentially multidrug-resistant foodborne zoonosis and can persistently colonize poultry flocks and farms.

METHODS AND RESULTS

Routine monitoring initially identified the organism, which was tracked to six farms associated with a single company. Extensive, repeat sampling identified widespread and, in some cases, persistent contamination. Salmonella Infantis was also isolated from three associated processing factories and catching crew equipment, but not from associated hatcheries and feed mills. Whole genome sequencing and resistance phenotyping revealed one strain was present in the processing plants and on five farms. However, on one of those farms, several highly genetically distinct strains were also detected, including one also found in one of the processing plants. The sixth farm had a strain that was genetically unrelated to strains collected from the other premises and which exhibited an extended spectrum beta-lactamase phenotype. Cleaning and disinfection were enhanced, and the organism was eventually cleared from all farms.

CONCLUSIONS

There were multiple incursions of varied strains, with a possible link to processing factories. Elimination of S. Infantis from premises can be challenging but achievable.

Biological and genomic characterization of a polyvalent phage PSH-1 against multidrug-resistant Salmonella Enteritidis

BACKGROUND

Bacteriophage has been renewed attention as a new antibacterial agent due to the limitations of antibiotic treatment. Bacteriophages are generally thought to be highly host specific and even strain specific, but a small number of polyvalent bacteriophages have been found to infect bacteria of different genera.

RESULTS

In this study, a virulent lytic bacteriophage (named Salmonella phage PSH-1) of Salmonella Enteritidis was isolated from the sewage samples of a large-scale pig farm, PSH-1 demonstrated lytic activity against four multidrug-resistant Salmonella Enteritidis isolates and Escherichia coli, and then its biological characteristics, genome and bacteriostatic ability were investigated. The results showed that the initial titer of PSH-1 was 1.15 × 1010 PFU/mL and the optimal multiplicity of infection (MOI) was 0.01, PSH-1 has stable activity in the range of pH 3.0-11.0. One-step growth curve showed that its latent period was 20 min, burst time was 80 min, and the burst was 495 particles. The whole-genome sequencing results revealed phage PSH-1 had a linear dsDNA with 48,466 bp length. The G/C content was 45.33%. Non-coding RNA genes and virulence factors were not found. Eighty- five open reading frames (ORFs) were identified after online annotation. By tests, the use of phage could succeed in controlling the artificial Salmonella contamination in milk at a range of temperatures.

CONCLUSIONS

This study reports a novel Salmonella Enteritidis phage PSH-1, which has a robust lytic ability, no virulence factors, and good stability. The characterization and genomic analysis of PSH-1 will develop our understanding of phage biology and diversity and provide a potential arsenal for controlling of salmonellosis.

Nationwide surveillance and characterization of the third-generation cephalosporin-resistant Salmonella enterica serovar infantis isolated from chickens in South Korea between 2010 and 2022

The occurrence of extended-spectrum β-lactamase (ESBL)/AmpC β-lactamase-producing Salmonella conferring resistance to third-generation cephalosporin has emerged as a global public health concern. In this study, we aimed to investigate the prevalence and molecular characterization of third-generation cephalosporin-resistant Salmonella enterica serovar Infantis. In total, 409 S. Infatis isolates were collected from the feces and carcasses of healthy and diseased food animals, including chickens (n = 348), pigs (n = 48), cattle (n = 8), and ducks (n = 5) between 2010 and 2022 nationwide in South Korea. Among them, 61.9 % (253/409) of S. Infantis strains displayed resistance to ceftiofur, with the most resistant isolates obtained from chickens (98.4 %, 249/253). Moreover, S. Infantis isolates showed high resistance (47.7-67.2 %) to streptomycin, ampicillin, nalidixic acid, sulfisoxazole, chloramphenicol, tetracycline, and trimethoprim/sulfamethoxazole. Additionally, the multidrug resistance (MDR) was significantly greater in the ceftiofur-resistant isolates compared to the ceftiofur-susceptible isolates (p < 0.05). All the ceftiofur-resistant S. Infantis strains produced CTX-M/CMY-2 β-lactamase enzymes, with bla CTX-M-65 comprising the most (98.4 %, 249/253), followed by bla CTX-M-15 (1.2 %, 3/253), and bla CMY-2 (0.4 %, 1/253). The ceftiofur-resistant S. Infantis belonged to 37 different pulsotypes, with X1A1 (26.1 %, 66/253), X1A2 (20.9 %, 53/253), and X5A3 (9.1 %) being the most prevalent, representing a total of 56.1 % (142/253). Furthermore, the S. Infantis sequence type (ST)32 was the most common, accounting for 91.9 % (34/37) of the three distinct STs (ST32, ST16, and ST11) detected across farms located in various provinces nationwide. Most of the bla CMX-M-65 genes (77.5 %, 193/249), all of the bla CTX-M-15 genes (100 %, 3/3), and the bla CMY-2 gene (100 %, 1/1) were transferred to the recipient E. coli RG488 by conjugation. In addition, the majority of the transconjugants (98.9 %, 191/193) containing bla CTX-M-65 genes belong to the IncFIB replicon type, playing an important role in the quick and widespread dissemination of S. Infantis. Thus, ceftiofur-resistant S. Infantis carrying the β-lactamase genes in chickens has the potential to be transmitted to humans.

Emergence of Salmonella Infantis carrying the pESI-like plasmid from eggs in egg grading and packing plants in Korea

The plasmid of emerging S. Infantis (pESI) or pESI-like plasmid in Salmonella enterica Infantis are consistently reported in poultry and humans worldwide. However, there has been limited research on these plasmids of S. Infantis isolated from eggs. Therefore, this study aimed to analyze the prevalence and characteristics of S. Infantis carrying the pESI-like plasmid from eggs in egg grading and packing plants. In this study, the pESI-like plasmid was only detected in 18 (78.3%) of 23 S. Infantis isolates, and it was absent in the other 9 Salmonella serovars. In particular, S. Infantis isolates carrying the pESI-like plasmid showed the significantly higher resistance to β-lactams, phenicols, cephams, aminoglycosides, quinolones, sulfonamides, and tetracyclines than Salmonella isolates without the pESI-like plasmid (p < 0.05). Moreover, all S. Infantis isolates carrying the pESI-like plasmid were identified as extended-spectrum β-lactamase (ESBL) producer, harboring the blaCTX-M-65 and blaTEM-1 genes, and carried non-β-lactamase resistance genes (ant(3'')-Ia, aph(4)-Ia, aac(3)-IVa, aph(3')-Ic, sul1, tetA, dfrA14, and floR) against five antimicrobial classes. However, all isolates without the pESI-like plasmid only carried the blaTEM-1 gene among the β-lactamase genes, and either had no non-β-lactamase resistance genes or harbored non-β-lactamase resistance genes against one or two antimicrobial classes. Furthermore, all S. Infantis isolates carrying the pESI-like plasmid carried class 1 and 2 integrons and the aadA1 gene cassette, but none of the other isolates without the pESI-like plasmid harbored integrons. In particular, D87Y substitution in the gyrA gene and IncP replicon type were observed in all the S. Infantis isolates carrying the pESI-like plasmid but not in the S. Infantis isolates without the pESI-like plasmid. The distribution of pulsotypes between pESI-positive and pESI-negative S. Infantis isolates was clearly distinguished, but all S. Infantis isolates were classified as sequence type 32, regardless of whether they carried the pESI-like plasmid. This study is the first to report the characteristics of S. Infantis carrying the pESI-like plasmid isolated from eggs and can provide valuable information for formulating strategies to control the spread of Salmonella in the egg industry worldwide.

Salmonella in Coastal Birds in Chile: Detection of a Multidrug-Resistant S. Infantis Bearing the bla CTX-M-65 Gene in a pESI-Like Megaplasmid in Humboldt Penguins

Salmonella enterica is one of the most important foodborne pathogens worldwide, and the emergence of multidrug resistance (MDR) clones can aggravate its public health importance. Wildlife species may act as reservoirs of these clones, but their role is not well understood. In this study, faecal samples from shorebirds, with a focus on the endangered Humboldt penguin (Spheniscus humboldti), collected from five sites in central Chile with different levels of anthropogenic pressure were analysed to characterize antimicrobial resistant S. enterica serovars. Overall, Salmonella was isolated from 22 of the 595 samples (3.7%), with positivity ranging between 1.6% and 9.5%, depending on the sampling site. Four of the Salmonella isolates were retrieved from Humboldt penguin samples (1.4% positive samples in this species). Serovars Infantis (nine isolates), Typhimurium (six), Goldcoast (four), and Enteritidis, Agona, and Give (one isolate each) were identified. Resistance levels were the highest for sulphamethoxazole (13/21 isolates with a non-wild-type phenotype), ciprofloxacin, tetracycline, and trimethoprim (11/21 each). Whole-genome sequencing performed on eight S. Infantis strains revealed that seven carried the plasmid replicon IncFIB (pN55391), indicating the presence of the pESI-like megaplasmid, harbouring resistance determinants to multiple antimicrobial classes as well as heavy metal, biocides, and virulence-related genes. Furthermore, five S. Infantis isolates that showed an ESBL phenotype carried the bla CTX-M-65 gene, three of which were detected in Humboldt penguin faeces. The finding of an international emerging S. Infantis clone in protected wildlife is of concern to environmental, animal, and public health specialists, supporting initiatives for an active surveillance of resistance and virulence traits in wildlife exposed to anthropogenic areas.

Detecting Class 1 Integrons and Their Variable Regions in Escherichia coli Whole-Genome Sequences Reported from Andean Community Countries

Various genetic elements, including integrons, are known to contribute to the development of antimicrobial resistance. Class 1 integrons have been identified in E. coli isolates and are associated with multidrug resistance in countries of the Andean Community. However, detailed information on the gene cassettes located on the variable regions of integrons is lacking. Here, we investigated the presence and diversity of class 1 integrons, using an in silico approach, in 2533 whole-genome sequences obtained from EnteroBase. IntFinder v1.0 revealed that almost one-third of isolates contained these platforms. Integron-bearing isolates were associated with environmental, food, human, and animal origins reported from all countries under scrutiny. Moreover, they were identified in clones known for their pathogenicity or multidrug resistance. Integrons carried cassettes associated with aminoglycoside (aadA), trimethoprim (dfrA), cephalosporin (blaOXA; blaDHA), and fluoroquinolone (aac(6')-Ib-cr; qnrB) resistance. These platforms showed higher diversity and larger numbers than previously reported. Moreover, integrons carrying more than three cassettes in their variable regions were determined. Monitoring the prevalence and diversity of genetic elements is necessary for recognizing emergent patterns of resistance in pathogenic bacteria, especially in countries where various factors are recognized to favor the selection of resistant microorganisms.

Emergence of Salmonella Infantis carrying the pESI megaplasmid in commercial farms of five major integrated broiler operations in Korea

Considering Salmonella transmission occurs through several routes in integrated broiler operations, control of nontyphoidal Salmonella in commercial farms is essential. This study aimed to compare the distribution of persistent Salmonella serovars in environments and dead chickens between 5 major integrated broiler operations in Korea. The prevalence of Salmonella-positive farms in dust prior to placement by operations was 0 to 25%, but the prevalence in dust and feces at the time of depletion was increased to 16.7 to 41.7% and 16.7 to 66.7%, respectively. Moreover, the prevalence of farms with Salmonella in chickens that died within 1 week old and at 4 to 5 weeks old ranged from 8.3 to 58.3% and 16.7 to 41.7%, respectively. The prevalence of Salmonella enterica serovar Infantis-positive farms in dust prior to placement and in chickens that died within 1 week old was 5.2 and 3.4%, respectively, but the prevalence in dust and feces at the time of depletion and in chickens that died at 4 to 5 weeks old was significantly increased to 27.6, 41.4, and 20.7%, respectively (P < 0.05). Interestingly, the plasmid of emerging S. Infantis (pESI) was only identified in S. Infantis, and the prevalence of multidrug-resistance was significantly higher in pESI-positive S. Infantis (99.2%) than in pESI-negative S. Infantis (6.7%) (P < 0.05). The distribution of pulsotypes between pESI-positive and pESI-negative S. Infantis were varied, but a majority of S. Infantis were clustered only 2 pulsotypes. Moreover, pESI-positive S. Infantis harbored more virulence factors than pESI-negative S. Infantis. This study is the first report on characteristics of S. Infantis carrying the pESI plasmid in commercial broiler farms in Korea.

The spread of pESI-mediated extended-spectrum cephalosporin resistance in Salmonella serovars-Infantis, Senftenberg, and Alachua isolated from food animal sources in the United States

The goal of this study is to investigate the origin, prevalence, and evolution of the pESI megaplasmid in Salmonella isolated from animals, foods, and humans. We queried 510,097 Salmonella genomes under the National Center for Biotechnology Information (NCBI) Pathogen Detection (PD) database for the presence of potential sequences containing the pESI plasmid in animal, food, and environmental sources. The presence of the pESI megaplasmid was confirmed by using seven plasmid-specific markers (rdA, pilL, SogS, TrbA, ipf, ipr2 and IncFIB(pN55391)). The plasmid and chromosome phylogeny of these isolates was inferred from single nucleotide polymorphisms (SNPs). Our search resolved six Salmonella clusters carrying the pESI plasmid. Four were emergent Salmonella Infantis clusters, and one each belonged to serovar Senftenberg and Alachua. The Infantis cluster with a pESI plasmid carrying blaCTX-M-65 gene was the biggest of the four emergent Infantis clusters, with over 10,000 isolates. This cluster was first detected in South America and has since spread widely in United States. Over time the composition of pESI in United States has changed with the average number of resistance genes showing a decrease from 9 in 2014 to 5 in 2022, resulting from changes in gene content in two integrons present in the plasmid. A recent and emerging cluster of Senftenberg, which carries the blaCTX-M-65 gene and is primarily associated with turkey sources, was the second largest in the United States. SNP analysis showed that this cluster likely originated in North Carolina with the recent acquisition of the pESI plasmid. A single Alachua isolate from turkey was also found to carry the pESI plasmid containing blaCTX-M-65 gene. The study of the pESI plasmid, its evolution and mechanism of spread can help us in developing appropriate strategies for the prevention and further spread of this multi-drug resistant plasmid in Salmonella in poultry and humans.

Genomic characterization, in vitro, and preclinical evaluation of two microencapsulated lytic phages VB_ST_E15 and VB_ST_SPNIS2 against clinical multidrug-resistant Salmonella serovars

BACKGROUND

Salmonella infections continue to be one of the essential public health issues threatening millions of people. With the increasing occurrence of resistance against conventionally used antibiotics, the search for alternatives has become crucial. In this study, we aimed to isolate, characterize, and evaluate two lytic bacteriophages against clinically isolated multidrug-resistant (MDR) Salmonella serovars.

METHODS

Screening for the phage lytic activity was performed using a spot test. Characterization of the isolated phages was done by determining the host range, longevity test, and the effect of temperature, pH, organic solvents, and morphological characterization using a transmission electron microscope. Genomic analysis was performed using Oxford nanopore sequencing. The lytic activities of the free phage lysates and formulated phage as microencapsulated were evaluated both in vitro and in vivo.

RESULTS

Two phages (VB_ST_E15 and VB_ST_SPNIS2) were successfully isolated and showed lytic strong activities against MDR Salmonella (S.) Typhimurium ATCC 14,028, S. Paratyphi A, and S. Typhi. The two phages survived at the tested temperatures, maintained their infectivity for 90 days, and retained their activity until 60 °C with thermal inactivation at 65 °C. They were lytic at a pH range from 3 to 11 but lost their activities at extremely acidic or alkaline pH. The phages could withstand the organic solvents but were completely inactivated by 100% ethanol. Both phages were classified under the order Caudoviricetes, and Genus: Uetakevirus. Their genomic sequences were assembled, annotated, and submitted to the NCBI GenBank database (OR757455 and OR757456). The preclinical evaluation using the murine animal model revealed that the two-phage cocktail managed MDR Salmonella infection as evidenced by the reduction in the bacterial burden, increased animal weight, and histopathological examination.

CONCLUSION

The two encapsulated phage formulas could be considered promising candidates for the management of MDR Salmonella-associated infections and clinical analysis should be undertaken to evaluate their potential use in humans.

Salmonellosis: An Overview of Epidemiology, Pathogenesis, and Innovative Approaches to Mitigate the Antimicrobial Resistant Infections

Salmonella is a major foodborne pathogen and a leading cause of gastroenteritis in humans and animals. Salmonella is highly pathogenic and encompasses more than 2600 characterized serovars. The transmission of Salmonella to humans occurs through the farm-to-fork continuum and is commonly linked to the consumption of animal-derived food products. Among these sources, poultry and poultry products are primary contributors, followed by beef, pork, fish, and non-animal-derived food such as fruits and vegetables. While antibiotics constitute the primary treatment for salmonellosis, the emergence of antibiotic resistance and the rise of multidrug-resistant (MDR) Salmonella strains have highlighted the urgency of developing antibiotic alternatives. Effective infection management necessitates a comprehensive understanding of the pathogen's epidemiology and transmission dynamics. Therefore, this comprehensive review focuses on the epidemiology, sources of infection, risk factors, transmission dynamics, and the host range of Salmonella serotypes. This review also investigates the disease characteristics observed in both humans and animals, antibiotic resistance, pathogenesis, and potential strategies for treatment and control of salmonellosis, emphasizing the most recent antibiotic-alternative approaches for infection control.

Analysis of the hypovirulent Klebsiella pneumoniae with the NDM-5 gene on IncN plasmids

IMPORTANCE

It is crucial to strengthen the ongoing clinical surveillance of non-highly virulent, multi-resistant Klebsiella pneumoniae.