Insights into the processes that drive the evolution of drug resistance in Mycobacterium tuberculosis. - Related Documents




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439601.0000Insights into the processes that drive the evolution of drug resistance in Mycobacterium tuberculosis. At present, the successful transmission of drug-resistant Mycobacterium tuberculosis, including multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains, in human populations, threatens tuberculosis control worldwide. Differently from many other bacteria, M. tuberculosis drug resistance is acquired mainly through mutations in specific drug resistance-associated genes. The panel of mutations is highly diverse, but depends on the affected gene and M. tuberculosis genetic background. The variety of genetic profiles observed in drug-resistant clinical isolates underlines different evolutionary trajectories towards multiple drug resistance, although some mutation patterns are prominent. This review discusses the intrinsic processes that may influence drug resistance evolution in M. tuberculosis, such as mutation rate, drug resistance-associated mutations, fitness cost, compensatory mutations and epistasis. This knowledge should help to better predict the risk of emergence of highly resistant M. tuberculosis strains and to develop new tools and strategies to limit the development and spread of MDR and XDR strains.201830344622
439510.9999Whole-genome sequencing of rifampicin-resistant Mycobacterium tuberculosis strains identifies compensatory mutations in RNA polymerase genes. Epidemics of drug-resistant bacteria emerge worldwide, even as resistant strains frequently have reduced fitness compared to their drug-susceptible counterparts. Data from model systems suggest that the fitness cost of antimicrobial resistance can be reduced by compensatory mutations; however, there is limited evidence that compensatory evolution has any significant role in the success of drug-resistant bacteria in human populations. Here we describe a set of compensatory mutations in the RNA polymerase genes of rifampicin-resistant M. tuberculosis, the etiologic agent of human tuberculosis (TB). M. tuberculosis strains harboring these compensatory mutations showed a high competitive fitness in vitro. Moreover, these mutations were associated with high fitness in vivo, as determined by examining their relative clinical frequency across patient populations. Of note, in countries with the world's highest incidence of multidrug-resistant (MDR) TB, more than 30% of MDR clinical isolates had this form of mutation. Our findings support a role for compensatory evolution in the global epidemics of MDR TB.201122179134
439220.9999The Neglected Contribution of Streptomycin to the Tuberculosis Drug Resistance Problem. The airborne pathogen Mycobacterium tuberculosis is responsible for a present major public health problem worsened by the emergence of drug resistance. M. tuberculosis has acquired and developed streptomycin (STR) resistance mechanisms that have been maintained and transmitted in the population over the last decades. Indeed, STR resistant mutations are frequently identified across the main M. tuberculosis lineages that cause tuberculosis outbreaks worldwide. The spread of STR resistance is likely related to the low impact of the most frequent underlying mutations on the fitness of the bacteria. The withdrawal of STR from the first-line treatment of tuberculosis potentially lowered the importance of studying STR resistance. However, the prevalence of STR resistance remains very high, could be underestimated by current genotypic methods, and was found in outbreaks of multi-drug (MDR) and extensively drug (XDR) strains in different geographic regions. Therefore, the contribution of STR resistance to the problem of tuberculosis drug resistance should not be neglected. Here, we review the impact of STR resistance and detail well-known and novel candidate STR resistance mechanisms, genes, and mutations. In addition, we aim to provide insights into the possible role of STR resistance in the development of multi-drug resistant tuberculosis.202134946952
439130.9999'To be, or not to be'-The dilemma of 'silent' antimicrobial resistance genes in bacteria. Antimicrobial resistance is a serious threat to public health that dramatically undermines our ability to treat bacterial infections. Microorganisms exhibit resistance to different drug classes by acquiring resistance determinants through multiple mechanisms including horizontal gene transfer. The presence of drug resistance genotypes is mostly associated with corresponding phenotypic resistance against the particular antibiotic. However, bacterial communities harbouring silent antimicrobial resistance genes-genes whose presence is not associated with a corresponding resistant phenotype do exist. Under suitable conditions, the expression pattern of such genes often revert and regain resistance and could potentially lead to therapeutic failure. We often miss the presence of silent genes, since the current experimental paradigms are focused on resistant strains. Therefore, the knowledge on the prevalence, importance and mechanism of silent antibiotic resistance genes in bacterial pathogens are very limited. Silent genes, therefore, provide an additional level of complexity in the war against drug-resistant bacteria, reminding us that not only phenotypically resistant strains but also susceptible strains should be carefully investigated. In this review, we discuss the presence of silent antimicrobial resistance genes in bacteria, their relevance and their importance in public health.202235882476
426340.9999The emergence of antibiotic resistance by mutation. The emergence of mutations in nucleic acids is one of the major factors underlying evolution, providing the working material for natural selection. Most bacteria are haploid for the vast majority of their genes and, coupled with typically short generation times, this allows mutations to emerge and accumulate rapidly, and to effect significant phenotypic changes in what is perceived to be real-time. Not least among these phenotypic changes are those associated with antibiotic resistance. Mechanisms of horizontal gene spread among bacterial strains or species are often considered to be the main mediators of antibiotic resistance. However, mutational resistance has been invaluable in studies of bacterial genetics, and also has primary clinical importance in certain bacterial species, such as Mycobacterium tuberculosis and Helicobacter pylori, or when considering resistance to particular antibiotics, especially to synthetic agents such as fluoroquinolones and oxazolidinones. In addition, mutation is essential for the continued evolution of acquired resistance genes and has, e.g., given rise to over 100 variants of the TEM family of beta-lactamases. Hypermutator strains of bacteria, which have mutations in genes affecting DNA repair and replication fidelity, have elevated mutation rates. Mutational resistance emerges de novo more readily in these hypermutable strains, and they also provide a suitable host background for the evolution of acquired resistance genes in vitro. In the clinical setting, hypermutator strains of Pseudomonas aeruginosa have been isolated from the lungs of cystic fibrosis patients, but a more general role for hypermutators in the emergence of clinically relevant antibiotic resistance in a wider variety of bacterial pathogens has not yet been proven.200717184282
442550.9999Multidrug resistance in bacteria. Large amounts of antibiotics used for human therapy, as well as for farm animals and even for fish in aquaculture, resulted in the selection of pathogenic bacteria resistant to multiple drugs. Multidrug resistance in bacteria may be generated by one of two mechanisms. First, these bacteria may accumulate multiple genes, each coding for resistance to a single drug, within a single cell. This accumulation occurs typically on resistance (R) plasmids. Second, multidrug resistance may also occur by the increased expression of genes that code for multidrug efflux pumps, extruding a wide range of drugs. This review discusses our current knowledge on the molecular mechanisms involved in both types of resistance.200919231985
439460.9999Signatures of Selection at Drug Resistance Loci in Mycobacterium tuberculosis. Tuberculosis (TB) is the leading cause of death by an infectious disease, and global TB control efforts are increasingly threatened by drug resistance in Mycobacterium tuberculosis. Unlike most bacteria, where lateral gene transfer is an important mechanism of resistance acquisition, resistant M. tuberculosis arises solely by de novo chromosomal mutation. Using whole-genome sequencing data from two natural populations of M. tuberculosis, we characterized the population genetics of known drug resistance loci using measures of diversity, population differentiation, and convergent evolution. We found resistant subpopulations to be less diverse than susceptible subpopulations, consistent with ongoing transmission of resistant M. tuberculosis. A subset of resistance genes ("sloppy targets") were characterized by high diversity and multiple rare variants; we posit that a large genetic target for resistance and relaxation of purifying selection contribute to high diversity at these loci. For "tight targets" of selection, the path to resistance appeared narrower, evidenced by single favored mutations that arose numerous times in the phylogeny and segregated at markedly different frequencies in resistant and susceptible subpopulations. These results suggest that diverse genetic architectures underlie drug resistance in M. tuberculosis and that combined approaches are needed to identify causal mutations. Extrapolating from patterns observed for well-characterized genes, we identified novel candidate variants involved in resistance. The approach outlined here can be extended to identify resistance variants for new drugs, to investigate the genetic architecture of resistance, and when phenotypic data are available, to find candidate genetic loci underlying other positively selected traits in clonal bacteria. IMPORTANCEMycobacterium tuberculosis, the causative agent of tuberculosis (TB), is a significant burden on global health. Antibiotic treatment imposes strong selective pressure on M. tuberculosis populations. Identifying the mutations that cause drug resistance in M. tuberculosis is important for guiding TB treatment and halting the spread of drug resistance. Whole-genome sequencing (WGS) of M. tuberculosis isolates can be used to identify novel mutations mediating drug resistance and to predict resistance patterns faster than traditional methods of drug susceptibility testing. We have used WGS from natural populations of drug-resistant M. tuberculosis to characterize effects of selection for advantageous mutations on patterns of diversity at genes involved in drug resistance. The methods developed here can be used to identify novel advantageous mutations, including new resistance loci, in M. tuberculosis and other clonal pathogens.201829404424
424770.9999Drug resistance in tuberculosis. Drug-resistant tuberculosis remains a worldwide problem. New laboratory methods have improved our ability to more rapidly identify resistant strains, but the most effective approach is to prevent the appearance of resistance by appropriate choice of antibiotics and directly-observed therapy. Mycobacterium tuberculosis is treated with familiar and unique drugs; consequently, mechanisms of resistance have some unique features. All drug resistance thus far identified develops by mutational events rather than acquisition of resistance genes from other bacteria. An agenda is presented for countering the appearance of further drug resistance in mycobacteria.19979421707
426480.9999Mutational Evolution of Pseudomonas aeruginosa Resistance to Ribosome-Targeting Antibiotics. The present work examines the evolutionary trajectories of replicate Pseudomonas aeruginosa cultures in presence of the ribosome-targeting antibiotics tobramycin and tigecycline. It is known that large number of mutations across different genes - and therefore a large number of potential pathways - may be involved in resistance to any single antibiotic. Thus, evolution toward resistance might, to a large degree, rely on stochasticity, which might preclude the use of predictive strategies for fighting antibiotic resistance. However, the present results show that P. aeruginosa populations evolving in parallel in the presence of antibiotics (either tobramycin or tigecycline) follow a set of trajectories that present common elements. In addition, the pattern of resistance mutations involved include common elements for these two ribosome-targeting antimicrobials. This indicates that mutational evolution toward resistance (and perhaps other properties) is to a certain degree deterministic and, consequently, predictable. These findings are of interest, not just for P. aeruginosa, but in understanding the general rules involved in the evolution of antibiotic resistance also. In addition, the results indicate that bacteria can evolve toward higher levels of resistance to antibiotics against which they are considered to be intrinsically resistant, as tigecycline in the case of P. aeruginosa and that this may confer cross-resistance to other antibiotics of therapeutic value. Our results are particularly relevant in the case of patients under empiric treatment with tigecycline, which frequently suffer P. aeruginosa superinfections.201830405685
431790.9999Development and spread of bacterial resistance to antimicrobial agents: an overview. Resistance to antimicrobial agents is emerging in a wide variety of nosocomial and community-acquired pathogens. The emergence and spread of multiply resistant organisms represent the convergence of a variety of factors that include mutations in common resistance genes that extend their spectrum of activity, the exchange of genetic information among microorganisms, the evolution of selective pressures in hospitals and communities that facilitate the development and spread of resistant organisms, the proliferation and spread of multiply resistant clones of bacteria, and the inability of some laboratory testing methods to detect emerging resistance phenotypes. Twenty years ago, bacteria that were resistant to antimicrobial agents were easy to detect in the laboratory because the concentration of drug required to inhibit their growth was usually quite high and distinctly different from that of susceptible strains. Newer mechanisms of resistance, however, often result in much more subtle shifts in bacterial population distributions. Perhaps the most difficult phenotypes to detect, as shown in several proficiency testing surveys, are decreased susceptibility to beta-lactams in pneumococci and decreased susceptibility to vancomycin in staphylococci. In summary, emerging resistance has required adaptations and modifications of laboratory diagnostic techniques, empiric anti-infective therapy for such diseases as bacterial meningitis, and infection control measures in health care facilities of all kinds. Judicious use is imperative if we are to preserve our arsenal of antimicrobial agents into the next decade.200111524705
9922100.9998De novo acquisition of antibiotic resistance in six species of bacteria. Bacteria can become resistant to antibiotics in two ways: by acquiring resistance genes through horizontal gene transfer and by de novo development of resistance upon exposure to non-lethal concentrations. The importance of the second process, de novo build-up, has not been investigated systematically over a range of species and may be underestimated as a result. To investigate the DNA mutation patterns accompanying the de novo antibiotic resistance acquisition process, six bacterial species encountered in the food chain were exposed to step-wise increasing sublethal concentrations of six antibiotics to develop high levels of resistance. Phenotypic and mutational landscapes were constructed based on whole-genome sequencing at two time points of the evolutionary trajectory. In this study, we found that (1) all of the six strains can develop high levels of resistance against most antibiotics; (2) increased resistance is accompanied by different mutations for each bacterium-antibiotic combination; (3) the number of mutations varies widely, with Y. enterocolitica having by far the most; (4) in the case of fluoroquinolone resistance, a mutational pattern of gyrA combined with parC is conserved in five of six species; and (5) mutations in genes coding for efflux pumps are widely encountered in gram-negative species. The overall conclusion is that very similar phenotypic outcomes are instigated by very different genetic changes. The outcome of this study may assist policymakers when formulating practical strategies to prevent development of antimicrobial resistance in human and veterinary health care.IMPORTANCEMost studies on de novo development of antimicrobial resistance have been performed on Escherichia coli. To examine whether the conclusions of this research can be applied to more bacterial species, six species of veterinary importance were made resistant to six antibiotics, each of a different class. The rapid build-up of resistance observed in all six species upon exposure to non-lethal concentrations of antimicrobials indicates a similar ability to adjust to the presence of antibiotics. The large differences in the number of DNA mutations accompanying de novo resistance suggest that the mechanisms and pathways involved may differ. Hence, very similar phenotypes can be the result of various genotypes. The implications of the outcome are to be considered by policymakers in the area of veterinary and human healthcare.202539907470
4292110.9998The impact of different antibiotic regimens on the emergence of antimicrobial-resistant bacteria. BACKGROUND: The emergence and ongoing spread of antimicrobial-resistant bacteria is a major public health threat. Infections caused by antimicrobial-resistant bacteria are associated with substantially higher rates of morbidity and mortality compared to infections caused by antimicrobial-susceptible bacteria. The emergence and spread of these bacteria is complex and requires incorporating numerous interrelated factors which clinical studies cannot adequately address. METHODS/PRINCIPAL FINDINGS: A model is created which incorporates several key factors contributing to the emergence and spread of resistant bacteria including the effects of the immune system, acquisition of resistance genes and antimicrobial exposure. The model identifies key strategies which would limit the emergence of antimicrobial-resistant bacterial strains. Specifically, the simulations show that early initiation of antimicrobial therapy and combination therapy with two antibiotics prevents the emergence of resistant bacteria, whereas shorter courses of therapy and sequential administration of antibiotics promote the emergence of resistant strains. CONCLUSIONS/SIGNIFICANCE: The principal findings suggest that (i) shorter lengths of antibiotic therapy and early interruption of antibiotic therapy provide an advantage for the resistant strains, (ii) combination therapy with two antibiotics prevents the emergence of resistance strains in contrast to sequential antibiotic therapy, and (iii) early initiation of antibiotics is among the most important factors preventing the emergence of resistant strains. These findings provide new insights into strategies aimed at optimizing the administration of antimicrobials for the treatment of infections and the prevention of the emergence of antimicrobial resistance.200819112501
4241120.9998Mechanisms of antimicrobial resistance and implications for epidemiology. The development of antibacterial agents has provided a means of treating bacterial diseases which were, previously, often fatal in both man and animal and thus represents one of the major advances of the 20th century. However, the efficacy of these agents is increasingly being compromised by the development of bacterial resistance to the drugs currently available for therapeutic use. Bacterial resistance can be combated in two ways. New drugs to which bacteria are susceptible can be developed and policies to contain the development and spread of resistance can be implemented. Both strategies require an understanding of the mechanisms of drug resistance, its epidemiology and the role of environmental factors in promoting resistance. Over the past thirty years our knowledge of bacterial resistance has increased dramatically mainly due to new technology that has become available. Bacteria are able to resist antibacterials by a variety of mechanisms: for example, altering the target to decrease susceptibility to the antibacterial, inactivating or destroying the drug, reducing drug transport into the cell or metabolic bypass. These drug resistance determinants are mediated via one of two distinct genetic mechanisms, a mutation in the bacterial chromosome or by a transmissible element; either a plasmid or a transposon. Significant differences exist between these two types of drug resistance as transmissible resistance, which is mainly plasmid-mediated, permits intraspecies and even interspecies transfer to occur. In contrast, chromosomal resistance can only be passed on to progeny. Transmissible antibacterial resistance is the major cause of concern as it can lead to the rapid spread of antibacterial resistance and has proven difficult, if not impossible, to eradicate. Furthermore, plasmids and transposons can code for multiple antibiotic resistance as well as virulence genes. Antibacterials for which transferable resistance has been identified include most commonly used antibacterials such as beta-lactams, aminoglycosides, macrolides, sulphonamides, tetracyclines, chloramphenicol and trimethoprim. One notable exception is the 4-quinolones for which plasmid-mediated resistance has yet to be identified.19938212509
4249130.9998Detection of essential genes in Streptococcus pneumoniae using bioinformatics and allelic replacement mutagenesis. Although the emergence and spread of antimicrobial resistance in major bacterial pathogens for the past decades poses a growing challenge to public health, discovery of novel antimicrobial agents from natural products or modification of existing antibiotics cannot circumvent the problem of antimicrobial resistance. The recent development of bacterial genomics and the availability of genome sequences allow the identification of potentially novel antimicrobial agents. The cellular targets of new antimicrobial agents must be essential for the growth, replication, or survival of the bacterium. Conserved genes among different bacterial genomes often turn out to be essential (1, 2). Thus, the combination of comparative genomics and the gene knock-out procedure can provide effective ways to identify the essential genes of bacterial pathogens (3). Identification of essential genes in bacteria may be utilized for the development of new antimicrobial agents because common essential genes in diverse pathogens could constitute novel targets for broad-spectrum antimicrobial agents.200818392984
4833140.9998Emerging mechanisms of fluoroquinolone resistance. Broad use of fluoroquinolones has been followed by emergence of resistance, which has been due mainly to chromosomal mutations in genes encoding the subunits of the drugs' target enzymes, DNA gyrase and topoisomerase IV, and in genes that affect the expression of diffusion channels in the outer membrane and multidrug-resistance efflux systems. Resistance emerged first in species in which single mutations were sufficient to cause clinically important levels of resistance (e.g., Staphylococcus aureus and Pseudomonas aeruginosa). Subsequently, however, resistance has emerged in bacteria such as Campylobacter jejuni, Escherichia coli, and Neisseria gonorrhoeae, in which multiple mutations are required to generate clinically important resistance. In these circumstances, the additional epidemiologic factors of drug use in animals and human-to-human spread appear to have contributed. Resistance in Streptococcus pneumoniae, which is currently low, will require close monitoring as fluoroquinolones are used more extensively for treating respiratory tract infections.200111294736
4422150.9998Diversity among multidrug-resistant enterococci. Enterococci are associated with both community- and hospital-acquired infections. Even though they do not cause severe systemic inflammatory responses, such as septic shock, enterococci present a therapeutic challenge because of their resistance to a vast array of antimicrobial drugs, including cell-wall active agents, all commercially available aminoglycosides, penicillin and ampicillin, and vancomycin. The combination of the latter two occurs disproportionately in strains resistant to many other antimicrobial drugs. The propensity of enterococci to acquire resistance may relate to their ability to participate in various forms of conjugation, which can result in the spread of genes as part of conjugative transposons, pheromone-responsive plasmids, or broad host-range plasmids. Enterococcal hardiness likely adds to resistance by facilitating survival in the environment (and thus enhancing potential spread from person to person) of a multidrug-resistant clone. The combination of these attributes within the genus Enterococcus suggests that these bacteria and their resistance to antimicrobial drugs will continue to pose a challenge.19989452397
3829160.9998Associations among Antibiotic and Phage Resistance Phenotypes in Natural and Clinical Escherichia coli Isolates. The spread of antibiotic resistance is driving interest in new approaches to control bacterial pathogens. This includes applying multiple antibiotics strategically, using bacteriophages against antibiotic-resistant bacteria, and combining both types of antibacterial agents. All these approaches rely on or are impacted by associations among resistance phenotypes (where bacteria resistant to one antibacterial agent are also relatively susceptible or resistant to others). Experiments with laboratory strains have shown strong associations between some resistance phenotypes, but we lack a quantitative understanding of associations among antibiotic and phage resistance phenotypes in natural and clinical populations. To address this, we measured resistance to various antibiotics and bacteriophages for 94 natural and clinical Escherichia coli isolates. We found several positive associations between resistance phenotypes across isolates. Associations were on average stronger for antibacterial agents of the same type (antibiotic-antibiotic or phage-phage) than different types (antibiotic-phage). Plasmid profiles and genetic knockouts suggested that such associations can result from both colocalization of resistance genes and pleiotropic effects of individual resistance mechanisms, including one case of antibiotic-phage cross-resistance. Antibiotic resistance was predicted by core genome phylogeny and plasmid profile, but phage resistance was predicted only by core genome phylogeny. Finally, we used observed associations to predict genes involved in a previously uncharacterized phage resistance mechanism, which we verified using experimental evolution. Our data suggest that susceptibility to phages and antibiotics are evolving largely independently, and unlike in experiments with lab strains, negative associations between antibiotic resistance phenotypes in nature are rare. This is relevant for treatment scenarios where bacteria encounter multiple antibacterial agents.IMPORTANCE Rising antibiotic resistance is making it harder to treat bacterial infections. Whether resistance to a given antibiotic spreads or declines is influenced by whether it is associated with altered susceptibility to other antibiotics or other stressors that bacteria encounter in nature, such as bacteriophages (viruses that infect bacteria). We used natural and clinical isolates of Escherichia coli, an abundant species and key pathogen, to characterize associations among resistance phenotypes to various antibiotics and bacteriophages. We found associations between some resistance phenotypes, and in contrast to past work with laboratory strains, they were exclusively positive. Analysis of bacterial genome sequences and horizontally transferred genetic elements (plasmids) helped to explain this, as well as our finding that there was no overall association between antibiotic resistance and bacteriophage resistance profiles across isolates. This improves our understanding of resistance evolution in nature, potentially informing new rational therapies that combine different antibacterials, including bacteriophages.201729089428
4262170.9998Fitness cost of antibiotic susceptibility during bacterial infection. Advances in high-throughput DNA sequencing allow for a comprehensive analysis of bacterial genes that contribute to virulence in a specific infectious setting. Such information can yield new insights that affect decisions on how to best manage major public health issues such as the threat posed by increasing antimicrobial drug resistance. Much of the focus has been on the consequences of the selective advantage conferred on drug-resistant strains during antibiotic therapy. It is thought that the genetic and phenotypic changes that confer resistance also result in concomitant reductions in in vivo fitness, virulence, and transmission. However, experimental validation of this accepted paradigm is modest. Using a saturated transposon library of Pseudomonas aeruginosa, we identified genes across many functional categories and operons that contributed to maximal in vivo fitness during lung infections in animal models. Genes that bestowed both intrinsic and acquired antibiotic resistance provided a positive in vivo fitness advantage to P. aeruginosa during infection. We confirmed these findings in the pathogenic bacteria Acinetobacter baumannii and Vibrio cholerae using murine and rabbit infection models, respectively. Our results show that efforts to confront the worldwide increase in antibiotic resistance might be exacerbated by fitness advantages that enhance virulence in drug-resistant microbes.201526203082
4897180.9998Rapid diagnosis of tuberculosis. Detection of drug resistance mechanisms. Tuberculosis is still a serious public health problem, with 10.8 million new cases and 1.8 million deaths worldwide in 2015. The diversity among members of the Mycobacterium tuberculosis complex, the causal agent of tuberculosis, is conducive to the design of different methods for rapid diagnosis. Mutations in the genes involved in resistance mechanisms enable the bacteria to elude the treatment. We have reviewed the methods for the rapid diagnosis of M. tuberculosis complex and the detection of susceptibility to drugs, both of which are necessary to prevent the onset of new resistance and to establish early, appropriate treatment.201728318570
9575190.9998Antibiotic resistome of Salmonella typhi: molecular determinants for the emergence of drug resistance. Resistome is a cluster of microbial genes encoding proteins with necessary functions to resist the action of antibiotics. Resistome governs essential and separate biological functions to develop resistance against antibiotics. The widespread clinical and nonclinical uses of antibiotics over the years have combined to select antibiotic-resistant determinants and develop resistome in bacteria. At present, the emergence of drug resistance because of resistome is a significant problem faced by clinicians for the treatment of Salmonella infection. Antibiotic resistome is a dynamic and ever-expanding component in Salmonella. The foundation of resistome in Salmonella is laid long before; therefore, the antibiotic resistome of Salmonella is reviewed, discussed, and summarized. We have searched the literature using PubMed, MEDLINE, and Google Scholar with related key terms (resistome, Salmonella, antibiotics, drug resistance) and prepared this review. In this review, we summarize the status of resistance against antibiotics in S. typhi, highlight the seminal work in the resistome of S. typhi and the genes involved in the antibiotic resistance, and discuss the various methods to identify S. typhi resistome for the proactive identification of this infection and quick diagnosis of the disease.202134085183