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Antimicrobial Resistance and Increased Virulence of Salmonella

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A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Antimicrobial Agents and Resistance".

Deadline for manuscript submissions: closed (15 February 2023) | Viewed by 22810

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Dr. Bijay Khajanchi

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Guest Editor

National Center for Toxicological Research, Jefferson, AR, USA
Interests: salmonella plasmid biology; genome sequencing; three dimensional tissue culture systems; food microbiology; cell biology

Dr. Steven Foley

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Guest Editor

Division of Microbiology, National Center for Toxicological Research (NCTR), US Food and Drug Administration (FDA), Jefferson, AR 72079, USA
Interests: antimicrobial resistance; virulence; foodborne pathogens
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Widespread use of antibiotics has facilitated the emergence of highly resilient pathogens that pose a threat to public health via co-selection of antibiotic resistance genes and virulence factors. Salmonella is one of the major bacterial pathogens that can cause infections to humans and poultry, representing a public health concern. Plasmid-encoded genetic factors often contribute to virulence and antimicrobial resistance (AMR) to Salmonella; however, mechanisms are poorly understood. By identifying the specific virulence factors and antimicrobial resistance genes and understanding plasmid dissemination, strategies can be developed to better control the pathogens and/or reduce the spread of the virulence and antimicrobial resistance plasmids.

In this Special Issue, we therefore invite you to contribute original research and review papers describing areas including (but not limited to) antimicrobial resistance and virulence plasmids of Salmonella, dissemination of AMR and virulence of Salmonella, plasmid genetics of Salmonella, coexistence of antibiotic resistance genes and virulence factors, the role of mobile genetic elements in AMR, the role of virulence factors in Salmonella pathogenicity, and the role of Salmonella plasmid factors in increased virulence.

Dr. Bijay Khajanchi
Dr. Steven Foley
Guest Editors

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Keywords

Salmonella
antimicrobial resistance
virulence
plasmids
co-selection

Published Papers (12 papers)

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Editorial

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4 pages, 196 KiB

Open AccessEditorial

Antimicrobial Resistance and Increased Virulence of Salmonella

by Bijay K. Khajanchi and Steven L. Foley

Microorganisms 2022, 10(9), 1829; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10091829 - 14 Sep 2022

Cited by 4 | Viewed by 1321

Abstract

This special issue of Microorganisms highlights the importance of antimicrobial resistance (AMR) and increased virulence of Salmonella with multiple research papers [...] Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

Research

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13 pages, 2181 KiB

Open AccessArticle

Clinical Characteristics, Antimicrobial Resistance, Virulence Genes and Multi-Locus Sequence Typing of Non-Typhoidal Salmonella Serovar Typhimurium and Enteritidis Strains Isolated from Patients in Chiang Mai, Thailand

by Songphon Buddhasiri, Chutikarn Sukjoi, Arishabhas Tantibhadrasapa, Panupon Mongkolkarvin, Pattarapon Boonpan, Thanakorn Pattanadecha, Nattamon Onton, Touch Laisiriroengrai, Sunatcha Coratat, Banyong Khantawa, Surapun Tepaamorndech, Kwanjit Duangsonk and Parameth Thiennimitr

Microorganisms 2023, 11(10), 2425; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms11102425 - 28 Sep 2023

Viewed by 1239

Abstract

Non-typhoidal salmonellosis (NTS) caused by ingesting Salmonella enterica contaminated food or drink remains a major bacterial foodborne disease. Clinical outcomes of NTS range from self-limited gastroenteritis to life-threatening invasive NTS (iNTS). In this study, we isolated Salmonella spp. from the stool and blood of patients hospitalized at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand, between 2016–2021 (a total of 395 cases). Then, serovar Typhimurium and Enteritidis were identified and further characterized by multiplex PCR, and multi-locus sequence typing. Our data show that multidrug resistance (MDR) sequence type 34 (ST34) and ST11 are the predominant sequence types for serovars Typhimurium and Enteritidis, respectively. Most S. Typhimurium ST34 lacks spvB, and most S. Enteritidis ST11 harbor sseI, sodCI, rpoS and spvB genes. NTS can be found in a wide range of ages, and anemia could be a significant factor for S. Typhimurium infection (86.3%). Both S. Typhimurium (6.7%) and S. Enteritidis (25.0%) can cause iNTS in immunocompromised patients. S. Typhimurium conferred MDR phenotype higher than S. Enteritidis with multiple antibiotic resistance indexes of 0.22 and 0.04, respectively. Here, we characterized the important S. Typhimurium, S. Enteritidis, and human clinical factors of NTS within the region. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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21 pages, 5218 KiB

Open AccessArticle

Purified Plant-Derived Phenolic Acids Inhibit Salmonella Typhimurium without Alteration of Microbiota in a Simulated Chicken Cecum Condition

by Zabdiel Alvarado-Martinez, Zajeba Tabashsum, Arpita Aditya, Grace Suh, Matthew Wall, Katherine Hshieh and Debabrata Biswas

Microorganisms 2023, 11(4), 957; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms11040957 - 06 Apr 2023

Cited by 1 | Viewed by 1482

Abstract

Salmonella enterica serovar Typhimurium (ST) remains a predominant zoonotic pathogen because of its colonization in poultry, survivability in the environment, and increasing antibiotic-resistance pattern. Plant-derived phenolics, gallic acid (GA), protocatechuic acid (PA), and vanillic acids (VA) have demonstrated antimicrobial activity in vitro; therefore, this study collected chicken cecal fluid and supplemented it with these phenolics to evaluate their potential for eliminating ST and mod-ulating the microbiota of complex environments. ST was quantified through plating, while micro-biome analysis was performed through pair-end 16S-rRNA gene sequencing. CFU/mL of ST in cecal fluid with GA was significantly reduced by 3.28 and 2.78 log at 24 h and 48 h, while PA only had a slight numerical decrease. VA significantly reduced ST by 4.81 and 5.20 log at 24 h and 48 h. Changes in relative abundance of major phyla were observed at 24 h for samples with GA and VA as Firmicute levels increased 8.30% and 20.90%, while Proteobacteria decreased 12.86% and 18.48%, respectively. Significant changes in major genre were observed in Acinetobacter (3.41% for GA) and Escherichia (13.53% for VA), while Bifidobacterium increased (3.44% for GA) and Lactobacillus remained unchanged. Results suggest that phenolic compounds exert different effects on certain pathogens, while supporting some commensal bacteria. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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13 pages, 1724 KiB

Open AccessArticle

Genomic Investigation of Salmonella Typhi in Hong Kong Revealing the Predominance of Genotype 3.2.2 and the First Case of an Extensively Drug-Resistant H58 Genotype

by Xin Li, Huiluo Cao, Jonathan Hon-Kwan Chen, Yuey-Zhun Ng, Ka-Kin Fung, Vincent Chi-Chung Cheng and Pak-Leung Ho

Microorganisms 2023, 11(3), 667; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms11030667 - 06 Mar 2023

Cited by 1 | Viewed by 1682

Abstract

Typhoid fever is a notable disease in Hong Kong. We noticed two local cases of typhoid fever caused by Salmonella Typhi within a two-week period in late 2022, which had no apparent epidemiological linkage except for residing in the same region of Hong Kong. A phylogenetic study of Salmonella Typhi isolates from Hong Kong Island from 2020 to 2022 was performed, including a whole-genome analysis, the typing of plasmids, and the analysis of antibiotic-resistance genes (ARGs), to identify the dominant circulating strain and the spread of ARGs. A total of seven isolates, from six local cases and an imported case, were identified from positive blood cultures in two hospitals in Hong Kong. Five antibiotic-sensitive strains of genotype 3.2.2 were found, which clustered with another 30 strains originating from Southeast Asia. Whole-genome sequencing revealed clonal transmission between the two index cases. The remaining two local cases belong to genotype 2.3.4 and genotype 4.3.1.1.P1 (also known as the H58 lineage). The genotype 4.3.1.1.P1 strain has an extensively drug-resistant (XDR) phenotype (co-resistance to ampicillin, chloramphenicol, ceftriaxone, ciprofloxacin, and co-trimoxazole). Although the majority of local strains belong to the non-H58 genotype 3.2.2 with a low degree of antibiotic resistance, the introduction of XDR strains with the global dissemination of the H58 lineage remains a concern. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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15 pages, 1522 KiB

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Association of ISVsa3 with Multidrug Resistance in Salmonella enterica Isolates from Cattle (Bos taurus)

by Gentry L. Lewis, Robert J. Fenton, Etsuko N. Moriyama, John Dustin Loy and Rodney A. Moxley

Microorganisms 2023, 11(3), 631; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms11030631 - 01 Mar 2023

Cited by 3 | Viewed by 1434

Abstract

Salmonella enterica is, globally, an important cause of human illness with beef being a significant attributable source. In the human patient, systemic Salmonella infection requires antibiotic therapy, and when strains are multidrug resistant (MDR), no effective treatment may be available. MDR in bacteria is often associated with the presence of mobile genetic elements (MGE) that mediate horizontal spread of antimicrobial resistance (AMR) genes. In this study, we sought to determine the potential relationship of MDR in bovine Salmonella isolates with MGE. The present study involved 111 bovine Salmonella isolates obtained collectively from specimens derived from healthy cattle or their environments at Midwestern U.S. feedyards (2000–2001, n = 19), or specimens from sick cattle submitted to the Nebraska Veterinary Diagnostic Center (2010–2020, n = 92). Phenotypically, 33/111 isolates (29.7%) were MDR (resistant to ≥3 drug classes). Based on whole-genome sequencing (WGS; n = 41) and PCR (n = 111), a MDR phenotype was strongly associated (OR = 186; p < 0.0001) with carriage of ISVsa3, an IS91-like Family transposase. In all 41 isolates analyzed by WGS ((31 MDR and 10 non-MDR (resistant to 0–2 antibiotic classes)), MDR genes were associated with carriage of ISVsa3, most often on an IncC type plasmid carrying bla_CMY-2. The typical arrangement was floR, tet(A), aph(6)-Id, aph(3″)-Ib, and sul2 flanked by ISVsa3. These results suggest that AMR genes in MDR S. enterica isolates of cattle are frequently associated with ISVsa3 and carried on IncC plasmids. Further research is needed to better understand the role of ISVsa3 in dissemination of MDR Salmonella strains. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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15 pages, 1489 KiB

Open AccessArticle

Comparative Analysis between Salmonella enterica Isolated from Imported and Chinese Native Chicken Breeds

by Wenjian Shi, Wenli Tang, Yafei Li, Yu Han, Lulu Cui and Shuhong Sun

Microorganisms 2023, 11(2), 390; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms11020390 - 03 Feb 2023

Cited by 3 | Viewed by 1530

Abstract

Salmonella enterica is considered a significant threat to the global poultry industry and public health. In recent decades, antimicrobial resistance in Salmonella enterica has attracted increasing concern throughout the world. However, limited information is available on Salmonella enterica among different breeds of breeder chickens. Thus, this study aimed to compare the prevalence, serotype distribution, emergence of extended-spectrum beta-lactamases (ESBLs), antimicrobial resistance, and genetic resistance mechanisms in Salmonella enterica among different breeds of breeder chickens. A total of 693 samples (dead embryos, cloacal swabs, water, feed, environmental swabs, and meconium of newly hatched chicks) were selected and cultured for Salmonella from four breeder chicken farms in Shandong province, China, representing one imported and three native breeds, and the isolates were further serotyped. Of the Salmonella isolates, susceptibility to 11 antimicrobials of 5 classes, ESBL screening, and the presence of 21 antimicrobial resistance genes were determined in the present study. Overall, 94 (13.6%) isolates were recovered, which were divided into 3 serotypes (Salmonella Pullorum (n = 36), Salmonella Thompson (n = 32), and Salmonella Enteritidis (n = 26)). The results showed that the prevalence of Salmonella enterica isolates from the imported breeds was higher compared with the three domestic breeds. Eight of the ninety-four isolates were ESBL-positive strains, which were recovered from a domestic breed chicken farm. These eight ESBL-producing isolates were serotyped to Pullorum. Surprisingly, Salmonella Enteritidis (S. enteritidis) and S. pullorum were simultaneously isolated from a single dead embryo observed among one native breed. Meanwhile, among the Salmonella isolates, 53.2% (50/94) were multidrug-resistant strains, and 44.7% (42/94) of the isolates presented resistance to at least five antibiotics. Nearly all of the isolates (97.9%, 92/94) were resistant to at least one antimicrobial; one isolate of S. Thompson was resistant to seven antimicrobial agents belonging to four different classes. The carriage rate of three resistance genes (tetA, tetB, and sul1) among isolates from the imported breeds (87%, 70%, and 65.2%) was higher than that in those from domestic breeds (35.2%, 36.6, and 14.1%). To our knowledge, this is the first report of ESBLs-producing Salmonella isolated from a Chinese native breed of breeder chickens. Our results also highlight that a high prevalence of multidrug-resistant Salmonella enterica contamination is widespread among different breeds of breeder chickens, which is a major risk of food-borne diseases and public health. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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13 pages, 6655 KiB

Open AccessArticle

Comparative Analysis of the Liver Transcriptome of Beijing You Chickens and Guang Ming Broilers under Salmonella enterica Serovar Typhimurium Infection

by Zixuan Wang, Hailong Wang, Astrid Lissette Barreto Sánchez, Mamadou Thiam, Jin Zhang, Qinghe Li, Maiqing Zheng, Jie Wen, Hegang Li, Guiping Zhao and Qiao Wang

Microorganisms 2022, 10(12), 2440; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10122440 - 09 Dec 2022

Viewed by 1437

Abstract

Salmonella enterica serovar Typhimurium (ST) is a food-borne pathogen that can infect animals and humans. It is currently the most common bacterial pathogen that negatively affects the poultry industry. Although different chicken breeds have been observed to exhibit diverse resistance to ST infection, the underlying genetic mechanisms remain unclear and the genes involved in this differential disease resistance need to be identified. To overcome this knowledge gap, we used a liver transcriptome analysis to screen differentially expressed genes (DEGs) in two different chicken breeds (local Beijing You (BY) and commercial Guang Ming No. 2 broiler line B (GM)) before and after ST infection. We also performed weighted gene co-expression network analysis (WGCNA) to detect hub genes, and employed selection signal analysis of candidate genes. Three promising genes (EGR1, JUN and FOS) were eventually identified, and were significantly and differentially expressed in the same breed under different conditions, and in the two breeds after ST infection. Hub genes, such as PPFIA4 and ZNF395, were identified using WGCNA, and were associated with the ratio of heterophils to lymphocytes (H/L), an indicator of disease resistance. the present study identified several genes and pathways associated with resistance to ST infection, and found that BY had greater resistance to ST infection than GM. The results obtained provide valuable resources for investigating the mechanisms of resistance to ST infection in different chicken breeds. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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16 pages, 4051 KiB

Open AccessArticle

Silencing of Salmonella typhimurium Pathogenesis: Atenolol Acquires Efficient Anti-Virulence Activities

by Abrar K. Thabit, Khalid Eljaaly, Ayat Zawawi, Tarek S. Ibrahim, Ahmed G. Eissa, Samar S. Elbaramawi, Wael A. H. Hegazy and Mahmoud A. Elfaky

Microorganisms 2022, 10(10), 1976; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10101976 - 06 Oct 2022

Cited by 16 | Viewed by 1790

Abstract

The targeting of bacterial virulence is proposed as a promising approach to overcoming the bacterial resistance development to antibiotics. Salmonella enterica is one of the most important gut pathogens that cause a wide diversity of local and systemic illnesses. The Salmonella virulence is controlled by interplayed systems namely Quorum sensing (QS) and type three secretion system (T3SS). Furthermore, the Salmonella spy on the host cell via sensing the adrenergic hormones enhancing its virulence. The current study explores the possible anti-virulence activities of β-adrenoreceptor blocker atenolol against S. enterica serovar Typhimurium in vitro, in silico, and in vivo. The present findings revealed a significant atenolol ability to diminish the S. typhimurium biofilm formation, invasion into HeLa cells, and intracellular replication inside macrophages. Atenolol significantly downregulated the encoding genes of the T3SS-type II, QS receptor Lux analogs sdiA, and norepinephrine membranal sensors qseC and qseE. Moreover, atenolol significantly protected mice against S. typhimurium. For testing the possible mechanisms for atenolol anti-virulence activities, an in silico molecular docking study was conducted to assess the atenolol binding ability to QS receptor SdiA and norepinephrine membranal sensors QseC. Atenolol showed the ability to compete on the S. typhimurium targets. In conclusion, atenolol is a promising anti-virulence candidate to alleviate the S. typhimurium pathogenesis by targeting its QS and T3SS systems besides diminishing the eavesdropping on the host cells. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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7 pages, 222 KiB

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Epidemiological and Clinical Characteristics of Non-Typhoidal Salmonella Bloodstream Infections in Central Israel: A Case-Control Study

by Yael Israel, Khitam Muhsen, Assaf Rokney and Amos Adler

Microorganisms 2022, 10(10), 1942; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10101942 - 30 Sep 2022

Cited by 1 | Viewed by 1201

Abstract

Non-typhoidal Salmonella (NTS) infection continues to be a significant cause of morbidity. In addition to gastroenteritis (GE), NTS may cause bloodstream infections (BSI). Our goals were to characterize the demographics, clinical characteristics and outcome of NTS-BSI in central Israel. The study was a retrospective, case-control study conducted at the Tel Aviv Sourasky Medical Center between 2001–2018. Cases with NTS-BSI were matched by age and compared with two control groups, hospitalized patients with NTS-GE and patients with E. coli BSI. The NTS-BSI group included 34 patients who were compared with 69 and 68 patients in the NTS-GE and E. coli BSI groups, respectively. In the NTS-BSI group, the median age was 59 years, with 20% of patients below 20 years of age. Diarrhea was less common in NTS-BSI patients compared with NTS-GE: 53% vs. 80% (p < 0.01). Compared with NTS-GE patients, NTS-BSI patients had a higher rate of recent antimicrobial use: 21% vs. 5.9%, p = 0.03, respectively. They also had a slightly higher Charlson Comorbidity Index score, and history of past malignancy and steroid use, but these differences were not statistically significant. Antimicrobial treatment was documented in 30/34 of the NTS-BSI patients vs. 55/69 of the NTS-GE patients (p < 0.001). NTS-BSI patients had higher rates of in-hospital death (23% vs. 4%, p < 0.01) and a longer length of stay (8 vs. 4 days, p < 0.001) compared with NTS-GE. There was no significant difference in the outcome compared with the E. coli BSI group. In conclusion, our study found relatively low rates of pediatric cases compared with previous studies in Israel. NTS-BSI patients had slightly higher rates of comorbidities compared with NTS-GE patients, and a similar prognosis to E. coli BSI patients. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

14 pages, 5306 KiB

Open AccessArticle

The Loss of focA Gene Increases the Ability of Salmonella Enteritidis to Exit from Macrophages and Boosts Early Extraintestinal Spread for Systemic Infection in a Mouse Model

by Ran Gao, Jian Zhang, Haoyu Geng, Yaonan Wang, Xilong Kang, Shizhong Geng, Xin’an Jiao and Paul Barrow

Microorganisms 2022, 10(8), 1557; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10081557 - 02 Aug 2022

Cited by 2 | Viewed by 1430

Abstract

Salmonella Enteritidis (SE) can spread from the intestines to cause systemic infection, mainly involving macrophages. Intramacrophage Salmonella exits and reinfects neighboring cells, leading to severe disease. Salmonella genes involved in exiting from macrophages are not well understood or fully identified. A focA::Tn5 mutant was identified by an in vitro assay, with increased ability to exit from macrophages. A defined SEΔfocA mutant and its complemented derivative strain, SEΔfocA::focA, were constructed to confirm this phenotype. Although the lethal ability of focA mutants was similar to that of the parental SE in mice, it was isolated earlier from the liver and spleen than the parental SE. focA mutants induced higher levels of proinflammatory IL-12 and TNF-α compared with the parental SE and SEΔfocA::focA. focA mutants showed higher cytotoxicity and lower formate concentrations than SE and SEΔfocA::focA, whereas there was no change in pyroptosis, apoptosis and flagella formation ability. These current data suggest that the focA gene plays an important role in regulating intramacrophage Salmonella exiting and extraintestinal spread in mice, although the specific mechanism requires further in-depth studies. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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12 pages, 1954 KiB

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Increased Prevalence of Salmonella Infantis Isolated from Raw Chicken and Turkey Products in the United States Is Due to a Single Clonal Lineage Carrying the pESI Plasmid

by Elizabeth A. McMillan, Margaret D. Weinroth and Jonathan G. Frye

Microorganisms 2022, 10(7), 1478; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10071478 - 21 Jul 2022

Cited by 12 | Viewed by 2392

Abstract

Infantis has recently become one of the most common serotypes of Salmonella isolated in the U.S. from raw meat samples collected in processing facilities and in retail stores. Investigations have determined that the majority of these isolates contain the pESI plasmid, but there has not been a large-scale investigation of the chromosome of these isolates. Here, we investigated 3276 whole-genome sequences of Salmonella Infantis with and without the pESI plasmid to understand chromosomal differences between plasmid carriage groups. S. Infantis genomes arranged into multiple clades with a single clade containing the isolates carrying the plasmid. Fifty-eight SNPs were identified in complete linkage disequilibrium between isolates that did and did not carry the plasmid. However, there were no unique genes present only in the genomes of isolates containing the plasmid. On average, isolates with the plasmid did contain more insertion sequences than those without (p < 0.05). Given that S. Infantis isolates carrying pESI form a single clade, it can be inferred that the increase in carriage of this plasmid in the U.S. is due to rapid clonal expansion of a single strain rather than as a result of multiple transfer events. As this S. Infantis clone does not contain any unique chromosomal genes, its proliferation appears to be due to pESI plasmid-encoded genes that may be advantageous in the chickens and turkeys or in their environment. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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Review

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Understanding the Mechanism of Antimicrobial Resistance and Pathogenesis of Salmonella enterica Serovar Typhi

by Maryam Khan and Saba Shamim

Microorganisms 2022, 10(10), 2006; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10102006 - 11 Oct 2022

Cited by 3 | Viewed by 4602

Abstract

Salmonella enterica serovar Typhi (S. Typhi) is a Gram-negative pathogen that causes typhoid fever in humans. Though many serotypes of Salmonella spp. are capable of causing disease in both humans and animals alike, S. Typhi and S. Paratyphi are common in human hosts only. The global burden of typhoid fever is attributable to more than 27 million cases each year and approximately 200,000 deaths worldwide, with many regions such as Africa, South and Southeast Asia being the most affected in the world. The pathogen is able to cause disease in hosts by evading defense systems, adhesion to epithelial cells, and survival in host cells in the presence of several virulence factors, mediated by virulence plasmids and genes clustered in distinct regions known as Salmonella pathogenicity islands (SPIs). These factors, coupled with plasmid-mediated antimicrobial resistance genes, enable the bacterium to become resistant to various broad-spectrum antibiotics used in the treatment of typhoid fever and other infections caused by Salmonella spp. The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains in many countries of the world has raised great concern over the rise of antibiotic resistance in pathogens such as S. Typhi. In order to identify the key virulence factors involved in S. Typhi pathogenesis and infection, this review delves into various mechanisms of virulence, pathogenicity, and antimicrobial resistance to reinforce efficacious disease management. Full article

(This article belongs to the Special Issue Antimicrobial Resistance and Increased Virulence of Salmonella)

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