Available options in the management of non-typhi Salmonella

Stool carriage of CTX-M/CMY-producing Salmonella enterica in a Chinese tertiary hospital in Shenzhen, China

Salmonellosis, caused by non-typhoidal Salmonella, is a common foodborne gastrointestinal infection. Third-generation cephalosporins are recommended as the first-line treatment for Salmonella infections. Our study aimed to investigate the molecular epidemiology, antimicrobial resistance, and the transmission of extended-spectrum β-lactamases (ESBL) genes in 96 clinical Salmonella isolates collected between 2020 and 2022 at a tertiary hospital in Shenzhen, China. We performed antimicrobial susceptibility testing and whole-genome sequencing to identify serotypes, multilocus sequence typing, antimicrobial resistance genes in these isolates, and the genetic structures of the bla CTX-M/bla CMY genes. Seventeen Salmonella serotypes were identified, with S. 4,[5],12:i:- (37.5%) being the most common, followed by S. Enteritidis (15.63%), S. Typhimurium (14.58%), S. London (7.29%), and S. Rissen (5.21%). MLST analysis revealed 19 distinct sequence types (STs), with ST34 being the most prevalent (36.46%), followed by ST11 (15.63%) and ST19 (13.54%). Antimicrobial resistance testing showed those isolates had high levels of resistance to ampicillin (72.92%) and tetracycline (71.88%), with 70.83% of isolates as multidrug-resistant (MDR). Three bla CTX-M genes (bla CTX-M-14, bla CTX-M-55, and bla CTX-M-65) and bla CMY-2 were identified among 18 cefotaxime-resistant strains, of which one and 12 isolates successfully transferred bla CMY or bla CTX-M to E. coli C600 via conjugation, respectively. The bla CTX-M/bla CMY-2-carrying contigs in nine Salmonella isolates ranged from 2,156 to 164,862 bp, were located either on the chromosome (n=1) or plasmids (IncI1, IncK1, IncA/C) (n=9), and the bla CTX-M/bla CMY-2 genes were associated with ISEcp1. Our study demonstrates the diversity of MDR Salmonella serotypes in clinical isolates, and highlights the role of plasmids and mobile genetic elements in the horizontal transfer of bla CTX-M/bla CMY, emphasizing the need for continuous surveillance of Salmonella in clinical samples.

Prevalence of antibiotic resistance in Salmonella Typhimurium isolates originating from Iran: a systematic review and meta-analysis

Objective

Antibiotic resistance in Salmonella represents a significant global public health concern. Among various serovars, Salmonella enterica serovar Typhimurium is prevalent in multiple countries. This study aims to conduct a systematic review and meta-analysis to evaluate the pattern of antibiotic resistance in S. Typhimurium isolates from diverse sources in Iran.

Methods

We conducted a comprehensive and systematic search for relevant articles until December 2023 in the following databases: PubMed, Scopus, Web of Science, and SID. The collected data were analyzed using Stata software version 17.

Results

Eighteen studies examined the pattern of antibiotic resistance in S. Typhimurium for various antibiotics in Iran. Piperacillin and tetracycline exhibited the highest resistance rates, at 79 and 60% respectively, while cefixime and ceftriaxone had the lowest resistance rates at 0%.

Conclusion

Our findings indicate a high level of antibiotic resistance among the studied antibiotics. This high level of antibiotic resistance raises concerns and underscores the necessity for monitoring the use of antibiotics. Moreover, resistance to these antibiotics was more prevalent in samples isolated from animals compared to other sources. This highlights the importance of animal screening to detect the presence of drug-resistant isolates, with the ultimate goal of reducing antibiotic resistance and preventing the transmission of resistant strains to humans.

Population dynamics and antimicrobial resistance of Salmonella Derby ST40 from Shenzhen, China

Salmonella enterica subsp. enterica serovar Derby (S. Derby) is one of the most common serotypes responsible for salmonellosis in humans and animals. The two main sequence types (ST) observed in China are ST40 and ST71, with ST40 presently being the most common in Shenzhen. Recent years have seen an increasing number of cases of salmonella caused by ST40 S. Derby, but the epidemiology is not clear. We gathered 314 ST40 S. Derby isolates from food and patient samples for 11 years in Shenzhen; 76 globally prevalent representative strains were also collected. Whole-genome sequencing (WGS) combined with drug resistance phenotyping was used to examine population structural changes, inter-host associations, drug resistance characteristics, and the food-transmission risks of ST40 S. Derby in Shenzhen over this period. The S. enterica evolutionary tree is divided into five clades, and the strains isolated in Shenzhen were primarily concentrated in Clades 2, 4, and 5, and thus more closely related to strains from Asian (Thailand and Vietnam) than European countries. Our 11-year surveillance of S. Derby in Shenzhen showed that Clades 2, 4, and 5 are now the dominant epidemic branches, and branches 2 and 5 are heavily multi-drug resistant. The main resistance pattern is ampicillin-tetracycline-ciprofloxacin-chloramphenicol-nalidixic acid-streptomycin-sulfamethoxazole/trimethoprim. This may lead to a trend of increasing resistance to ST40 S. Derby in Shenzhen. Using a segmentation of ≤3 SNP among clone clusters, we discovered that Clades 2 and 4 contained multiple clonal clusters of both human- and food-derived strains. The food-derived strains were mainly isolated from pig liver, suggesting this food has a high risk of causing disease outbreaks in Shenzhen.

Non-Typhoidal Salmonella Infection in Children: Influence of Antibiotic Therapy on Postconvalescent Excretion and Clinical Course-A Systematic Review

(1) Background: Although published recommendations are available, the use of antibiotics in non-typhoidal Salmonella (NTS) infections in children is still controversially debated in clinical practice. Patients might even be put at risk, with necessary antibiotic therapy being withheld due to the widespread concern of prolonged post-convalescent shedding. The authors conducted a systematic review to assess whether antibiotic treatment influences fecal excretion or the clinical course in children with NTS infection. (2) Methods: The review was carried out following the PRISMA guidelines. In a Medline database search, studies assessing the influence of antibiotic therapy on excretion and/or the clinical course of NTS infections were selected. Studies reporting on adults only were not considered. Out of 532 publications which were identified during the systematic literature search, 14 publications were finally included (3273 patients in total). Quality and bias assessment was performed using the Newcastle-Ottawa scale (NOS) or the Cochrane risk-of bias tool (ROB-2). (3) Results: Four early studies from decades ago demonstrated a prolongation of intestinal NTS excretion in children after antibiotic treatment, whereas most studies published more recently observed no significant influence, which might be due to having used more “modern” antibiotic regimes (n = 7 studies). Most studies did not describe significant differences regarding the severity and duration of symptoms between untreated patients and those treated with antibiotics. Quality and bias were mainly moderate (NOS) or variable (ROB-2), respectively. (4) Conclusions: There is no substantial evidence of prolonged excretion of NTS in pediatric patients after treatment with newer antimicrobials. Consequently, clinicians should not withhold antibiotics in NTS infection for children at risk, such as for very young children, children with comorbidities, and those with suspected invasive disease due to concerns about prolonged post-convalescent bacterial excretion. In the majority of cases with uncomplicated NTS diarrhea, clinicians should refrain from applying antibiotics.

Invasive non-typhoidal Salmonella infections in sub-Saharan Africa: a systematic review on antimicrobial resistance and treatment

BACKGROUND

Non-typhoidal Salmonella (NTS) are a frequent cause of invasive infections in sub-Saharan Africa. They are frequently multidrug resistant (co-resistant to ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol), and resistance to third-generation cephalosporin and fluoroquinolone non-susceptibility have been reported. Third-generation cephalosporins and fluoroquinolones are often used to treat invasive NTS infections, but azithromycin might be an alternative. However, data on antibiotic treatment efficacy in invasive NTS infections are lacking. In this study, we aimed to assess the spatiotemporal distribution of antimicrobial resistance in invasive NTS infections in sub-Saharan Africa and to describe the available evidence and recommendations on antimicrobial treatment.

METHODS

We conducted a systematic review of all available literature on antimicrobial resistance and treatment in invasive NTS infections. We performed a random effects meta-analysis to assess the temporal distribution of multidrug resistance, third-generation cephalosporin resistance, and fluoroquinolone non-susceptibility. We mapped these data to assess the spatial distribution. We provided a narrative synthesis of the available evidence and recommendations on antimicrobial treatment.

RESULTS

Since 2001, multidrug resistance was observed in 75% of NTS isolates from all sub-Saharan African regions (95% confidence interval, 70-80% and 65-84%). Third-generation cephalosporin resistance emerged in all sub-Saharan African regions and was present in 5% (95% confidence interval, 1-10%) after 2010. Fluoroquinolone non-susceptibility emerged in all sub-Saharan African regions but did not increase over time. Azithromycin resistance was reported in DR Congo. There were no reports on carbapenem resistance. We did not find high-quality evidence on the efficacy of antimicrobial treatment. There were no supranational guidelines. The "Access group" antibiotics ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol and "Watch group" antibiotics ceftriaxone, cefotaxime, and ciprofloxacin were recommended as the first-choice antibiotics in national guidelines or reviews. These also recommended (a switch to) oral fluoroquinolones or azithromycin.

CONCLUSIONS

In addition to the widespread multidrug resistance in invasive NTS infections in sub-Saharan Africa, resistance to third-generation cephalosporins and fluoroquinolone non-susceptibility was present in all regions. There was a lack of data on the efficacy of antimicrobial treatment in these infections, and supranational evidence-based guidelines were absent.

Source Attribution Study of Sporadic Salmonella Derby Cases in France

Salmonella enterica subsp. enterica serovar Derby is one of the most frequent causes of gastroenteritis in humans. In Europe, this pathogen is one of the top five most commonly reported serovars in human cases. In France, S. Derby has been among the ten most frequently isolated serovars in humans since the year 2000. The main animal hosts of this serovar are pigs and poultry, and white meat is the main source of human contamination. We have previously shown that this serovar is polyphyletic and that three distinct genetic lineages of S. Derby cohabit in France. Two of them are associated with pork and one with poultry. In this study, we conducted a source attribution study based on single nucleotide polymorphism analysis of a large collection of 440 S. Derby human and non-human isolates collected in 2014-2015, to determine the contribution of each lineage to human contamination. In France, the two lineages associated with pork strains, and corresponding to the multilocus sequence typing (MLST) profiles ST39-ST40 and ST682 were responsible for 94% of human contaminations. Interestingly, the ST40 profile is responsible for the majority of human cases (71%). An analysis of epidemiologic data and the structure of the pork sector in France allowed us to explain the spread and the sporadic pattern of human cases that occurred in the studied period.

Genotypic Resistance to Quinolone and Tetracycline in Salmonella Dublin Strains Isolated from Humans and Animals in Brazil

Resistance of Salmonella Dublin strains to quinolones and tetracycline has been increasing worldwide. Studies regarding the genotypic resistance traits of strains of this serovar isolated in Brazil are scarce. This study aims to examine the genetic characteristics of Salmonella Dublin strains isolated in Brazil, which are associated with resistance to quinolone and tetracycline. The minimum inhibitory concentrations (MICs) of nalidixic acid, ciprofloxacin, and tetracycline of the 10 strains sensitive and 21 strains resistant to quinolone and tetracycline were determined using Etest.^® The mutation profiles of the gyrA, gyrB, parC, and parE genes were accessed by sequencing, while the presence of plasmid-mediated quinolone resistance and tet genes was analyzed by PCR. Quinolone-resistant strains presented the amino acid substitutions Ser96→Tyr, Ser96→Phe, Asp107→Asn, or Asp108→Gly on the gyrA gene, and the Ser224→Phe and Glu231→Asp mutations on the gyrB gene. The qnrA, tet(A), and tet(B) genes were detected in 5, 13, and 6 strains, respectively. Analysis of the MIC values revealed that 1 and 3 strains presented intermediate and resistant MIC profiles to nalidixic acid, respectively; 6 strains presented intermediate MIC profile to ciprofloxacin; and 13 strains presented resistant MIC profile to tetracycline. In the Salmonella Dublin strains studied, quinolone resistance was mainly related to mutation points that led to target alteration in the gyrA and gyrB genes, while tetracycline resistance was associated with the presence of tet(A) and/or tet(B) genes, with the highest resistance levels detected in strains bearing the tet(B) gene. The presence of the aforementioned genotypic resistance traits in Salmonella Dublin strains isolated over 33 years in Brazil indicates that ciprofloxacin or tetracycline therapy against such strains may fail.

Antimicrobial Resistance in Nontyphoidal Salmonella Isolated from Human and Poultry-Related Samples in Brazil: 20-Year Meta-Analysis

Nontyphoidal Salmonella are one of the leading causes of foodborne diseases in the world. As poultry products are recognized as main sources of human salmonellosis, nontyphoidal Salmonella control has become a global issue for the poultry industry. The increasing antimicrobial resistance in poultry-related nontyphoidal Salmonella serovars is a global matter of concern. By monitoring the evolution of antimicrobial resistance, alternative treatments can be identified and possible restrictions in the treatment of systemic human salmonellosis foreseen. A meta-analysis was conducted to assess the profile and temporal evolution of the antimicrobial resistance of nontyphoidal Salmonella of poultry and human origin in Brazil, isolated in the period from 1995 to 2014. Four databases were researched; twenty-nine articles met the eligibility criteria and were included in the meta-analysis. In the nontyphoidal isolates of poultry origin, the highest levels of antimicrobial resistance were verified for sulfonamides (44.3%), nalidixic acid (42.5%), and tetracycline (35.5%). In the human-origin isolates, the resistance occurred mainly for sulfonamides (46.4%), tetracycline (36.9%), and ampicillin (23.6%). Twenty-two articles described results of antimicrobial resistance specifically for Salmonella Enteritidis, also enabling the individual meta-analysis of this serovar. For most antimicrobials, the resistance levels of Salmonella Enteritidis were lower than those found when considering all the nontyphoidal serovars. In the poultry-origin isolates, a quadratic temporal distribution was observed, with reduced resistance to streptomycin in Salmonella Enteritidis and in all nontyphoidal serovars, and a linear increase of resistance to nalidixic acid in Salmonella Enteritidis. In the human-origin isolates, a linear increase was identified in the resistance to nalidixic acid in Salmonella Enteritidis and in all the nontyphoidal isolates, and to gentamicin in Salmonella Enteritidis. Continuous monitoring of the development and spread of antimicrobial resistance could support the measurement of the consequences on poultry and human health.

Salmonella infections: an update on epidemiology, management, and prevention

Salmonella species are a group of Gram-negative enterobacteria and known human pathogens in developing as well as industrialized countries. Despite significant advances in sanitation, provision of potable water, and highly controlled food chain surveillance, transmission of Salmonella spp. continues to affect communities, preferentially children, worldwide. This review summarizes updated concepts on typhoidal and non-typhoidal Salmonella infections, starting with a historical perspective that implicates typhoid Salmonella as a significant human pathogen since ancient times. We describe the epidemiology of this pathogen with emphasis on the most recent non-typhoidal Salmonella outbreaks in industrialized countries and continued outbreaks of typhoid Salmonella in underserved countries. An overview of clinical aspects of typhoid and non-typhoid infections in developing and industrialized countries, respectively, is provided, followed by a description on current treatment concepts and challenges treating multidrug-resistant Salmonella infections. We conclude with prevention recommendations, and recent research studies on vaccine prevention.

Salmonella entericaserotypes and antibiotic susceptibility in New Zealand, 2002–2007

We analysed the serotypes and antibiotic susceptibility of 1560 human and 1505 non-humanSalmonellaisolated in New Zealand (NZ) between 2002 and 2007. The most common serotypes in humans wereSalmonella entericaserovar Typhimurium,S. Enteritidis,S. Brandenburg andS. Infantis. Over the 6-year period human cases due toS. Agona andS. Enteritidis increased and cases due toS. Typhimurium decreased. The most common serotypes from non-human sources wereS. Typhimurium,S. Brandenberg,S. Hindmarsh andS. Infantis, and there were no significant changes over time. More isolates were non-susceptible to streptomycin than to any other antibiotic. Almost all isolates were susceptible to ciprofloxacin and gentamicin. There were significant trends of increasing non-susceptibility to streptomycin and sulfonamides in isolates from human and non-human sources, while ampicillin, tetracycline and multidrug non-susceptibility also increased in human isolates. Despite these increases, rates of antibiotic non-susceptibility inSalmonellain NZ are still lower than in many international settings.

Septic arthritis of the hip with psoas abscess caused by Non-typhi Salmonella infection in an immunocompetent patient

Osteoarticular infections caused by Non-typhi Salmonella are exceptionally encountered. We report a case of a bacteriologically documented hip infection associated with a psoas abscess due to Non-typhi Salmonella. A 64-year-old immunocompetent male was admitted in our department for pain and motion range limitation in the right hip with fever. Non-typhi Salmonella was recovered in joint fluid obtained by needle aspiration. Antimicrobial chemotherapy combined with surgical intervention was necessary for eradication of the infection. Physicians should be aware of this rare manifestation of Non-typhi Salmonella infections in non-debilitated patients.

Review article: the history of acute infectious diarrhoea management--from poorly focused empiricism to fluid therapy and modern pharmacotherapy

BACKGROUND

Acute diarrhoea management has progressed from largely ineffective measures in the early years to a more effective physiologic approach in recent years.

AIM

To review the history of acute diarrhoea management.

METHODS

Citations in PubMed were reviewed on 'acute diarrhoea treatment' along with an extensive file maintained by the corresponding author.

RESULTS

Freedom from diarrhoea was equated in early military conflicts with bravery and strength where diarrhoea-free soldiers had the 'guts' to fight. Until early 20th century, colonic irrigants, purgatives and emetic drugs were used to help eliminate undesired intestinal contents. Only a few early authorities suggested the need for replacement of fluids and salt, now standard treatment. Drugs aimed at diarrhoea symptom control have been broadly used for more than 100 years. The evolving history of one of those drugs, kaopectate is unappreciated. Once understanding the pathophysiology and infectious aetiology of acute diarrhoea, new oral fluids, pharmacologic agents designed to block specific secretory alterations and anti-infective drugs have been identified.

CONCLUSIONS

Physiologic and antimicrobial approaches to controlling diarrhoea can lead to reduction of stool number and enteric complaints, important in industrialized areas, with the potential for decreasing threat of fatal illness among infants in developing regions.

Effect of exposure to fluoroquinolones and beta-lactams on the in vitro activity of other groups of antibiotics in Salmonella spp

After designing in vitro models of repeated exposure of Salmonella spp. to various beta-lactams and fluoroquinolones we studied the decrease in susceptibility to other antibiotic families of the mutants generated. There was a decrease in the susceptibility of all the mutants to tetracycline, cotrimoxazole and chloramphenicol. Mutants generated following exposure to fluoroquinolones showed reduced susceptibility to amoxicillin, amoxicillin/clavulanic acid, cefoxitin and cefuroxime, whereas mutants generated following beta-lactam exposure showed reduced susceptibility to nalidixic acid and ciprofloxacin. We observed that the efflux pump systems are activated in the mutants generated and this may therefore be the cause of the decrease in susceptibility. In many cases the decrease is small and is not detected if the CLSI criteria are applied. Nevertheless, more detailed studies should be done to evaluate the importance of this phenomenon and rationalize the use of antibiotics in both humans and animals so as to control the increase in the number of multiresistant strains.

Plasmid-mediated quinolone resistance in non-Typhi serotypes of Salmonella enterica

BACKGROUND

Serious infections with Salmonella species are often treated with fluoroquinolones or extended-spectrum beta-lactams. Increasingly recognized in Enterobacteriaceae, plasmid-mediated quinolone resistance is encoded by qnr genes. Here, we report the presence of qnr variants in human isolates of non-Typhi serotypes of Salmonella enterica (hereafter referred to as non-Typhi Salmonella) from the United States National Antimicrobial Resistance Monitoring System for Enteric Bacteria.

METHODS

All non-Typhi Salmonella specimens from the United States National Antimicrobial Resistance Monitoring System for Enteric Bacteria collected from 1996 to 2003 with ciprofloxacin minimum inhibitory concentrations > or = 0.06 microg/mL (233 specimens) and a subset with minimum inhibitory concentrations < or = 0.03 microg/mL (102 specimens) were screened for all known qnr genes (A, B, and S) by polymerase chain reaction. For isolates with positive results, qnr and quinolone resistance-determining region sequences were determined. Plasmids containing qnr genes were characterized by conjugation or transformation.

RESULTS

Conjugative plasmids harboring qnrB variants were detected in 7 Salmonella enterica serotype Berta isolates and 1 Salmonella enterica serotype Mbandaka isolate. The S. Mbandaka plasmid also had an extended-spectrum beta -lactamase. Variants of qnrS on nonconjugative plasmids were detected in isolates of Salmonella enterica serotype Anatum and Salmonella enterica serotype Bovismorbificans.

CONCLUSIONS

Plasmid-mediated quinolone resistance appears to be widely distributed, though it is still uncommon in non-Typhi Salmonella isolates from the United States, including strains that are quinolone susceptible by the criteria of the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards). The presence of this gene in non-Typhi Salmonella that causes infection in humans suggests potential for spread through the food supply, which is a public health concern.

The clonal spread of multidrug-resistant non-typhi Salmonella serotypes

Non-typhoid Salmonella are one of the most important organisms causing food-borne diseases worldwide. There have been significant increases in developed countries in recent years in the occurrence of resistance, in particular multidrug resistance phenotypes, in non-typhoid Salmonella spp. Such increases have been observed in many countries, not only within the European community but also the Americas and Southeast Asia. Of particular concern is the increasing detection of Salmonella isolates displaying resistance to key antimicrobials, notably fluoroquinolones and third-generation cephalosporins. An important factor associated with this increase in multidrug resistance among particular Salmonella spp. is the national and international spread of certain clonal genotypes, the most recent being the global epidemic spread of multidrug-resistant S. Typhimurium DT104, since the early 1990s. In this review, we describe examples where particular antimicrobial-resistant Salmonella serotypes emerged, persisted for periods of time, and then quickly decreased in prevalence.

Relation between induction of the mar operon and cyclohexane tolerance and reduction in fluoroquinolone susceptibility in Salmonella spp

The relationship between cyclohexane tolerance and induction of the mar operon and a decrease in susceptibility to ciprofloxacin and moxifloxacin in isolates of Salmonella spp. from food and clinical isolates of Salmonella spp. was studied. We studied the influence of the mar operon using an inductor (acetylsalicylic acid) and we also studied the cyclohexane resistance. Induction was seen to produce an increase in the minimum inhibitory concentration (MIC) of these quinolones, which suggested that there was overexpression of the AcrAB type active efflux systems due to induction of the mar operon. Cyclohexane susceptibility was not shown to be a very sensitive method for studying this process, as only 3% (5/176) of the clinical isolates studied were cyclohexane-resistant; most of these belonged to the Hadar serotype. This study confirmed the participation of active efflux systems in the decrease in fluoroquinolone susceptibility in Salmonella spp. Furthermore, the study has indicated that these mechanisms (i.e., active efflux systems) are present in strains that are susceptible to the fluoroquinolone compounds, so their stimulation may be one of the mechanisms involved in the reduction in fluoroquinolone susceptibility. This suggests that the exposure of Salmonella spp. to antibiotics should be limited in order to prevent these active efflux systems from being activated. Consequently, the use of fluoroquinolones, both in the treatment of humans and in veterinary practice, should be controlled and rationalized in an attempt to curb the increase in the number of strains that are resistant to these compounds.