Salmonella infections

Megaplasmid Dissemination in Multidrug-Resistant Salmonella Serotypes from Backyard and Commercial Broiler Production Systems in the Southeastern United States

Over the past decade, there has been a rise in U.S. backyard poultry ownership, raising concern for residential area antimicrobial-resistant (AMR) Salmonella contamination. This study aims to lay the groundwork to better understand the persistence of AMR Salmonella in residential broiler production systems and make comparisons with commercial systems. Ten backyard and 10 commercial farms were sampled at three time points across bird production. Both fecal (n = 10) and environmental (soil, n = 5, litter/compost, n = 5, feeder, and waterer swabs, n = 6) samples were collected at each visit on days 10, 31, and 52 of production for backyard farms and days 10, 24, and 38 of production for commercial farms. AMR Salmonella was characterized phenotypically by broth microdilution and genotypically by whole-genome sequencing. Overall, Salmonella was more prevalent in commercial farm samples (52.31%) over backyard farms (19.10%). Kentucky (sequence type (ST) 152) was the most common serotype found in both backyard and commercial farms. Multidrug-resistant (MDR, resistance to ≥3 or more antimicrobial classes) isolates were found in both production systems, while ciprofloxacin- and nalidixic acid-resistant and intermediate isolates were more prevalent in commercial (33%) than backyard samples (1%). Plasmids that have been associated with MDR were found in Kentucky and Infantis isolates, particularly IncFIB(K)_1_Kpn3 megaplasmid (Infantis). Our study emphasizes the need to understand the selection pressures in disseminating megaplasmids in MDR Salmonella in distinct broiler production systems.

Blood Clots Per Rectum in a Pediatric Patient With Salmonella Enteritis: A Case Report

Infection is a common cause of hematochezia in children. While infectious diarrhea can present with bloody stools, it is rare to have the passage of frank blood clots per rectum in the pediatric population. This is a case of a seven-year-old male who presented with vomiting, diarrhea, severe abdominal pain, and passage of blood clots per rectum. As symptoms progressed, consideration of non-infectious causes was investigated and subsequently ruled out. The stool polymerase chain reaction (PCR) was positive for Salmonella species, while stool culture was negative for any enteropathogen. This report highlights the unusual occurrence of the passage of blood clots per rectum in a child with salmonella enterocolitis.

Mobile Colistin Resistance Genetic Determinants of Non-Typhoid Salmonella enterica Isolates from Russia

Polymyxin resistance, determined by mcr genes located on plasmid DNA, currently poses a high epidemiological threat. Non-typhoid Salmonella (NTS) are one of the key pathogens causing diarrheal diseases. Here, we report the isolation and whole genome sequencing of multidrug colistin-resistant/susceptible isolates of non-typhoid Salmonella enterica serovars carrying mcr genes. Non-typhoid strains of Salmonella enterica subsp. enterica were isolated during microbiological monitoring of the environment, food, and diarrheal disease patients between 2018 and 2020 in Russia (n = 586). mcr-1 genes were detected using a previously developed qPCR assay, and whole genome sequencing of mcr positive isolates was performed by both short-read (Illumina) and long-read (Oxford Nanopore) approaches. Three colistin-resistant isolates, including two isolates of S. Enteritidis and one isolate of S. Bovismorbificans, carried the mcr-1.1 gene located on IncX4 and IncI2 conjugative plasmids, respectively. The phenotypically colistin-susceptible isolate of S. Typhimurium carried a mcr-9 gene on plasmid IncHI2. In conclusion, we present the first three cases of mcr gene-carrying NTS isolates detected in Russia with both outbreak and sporadic epidemiological backgrounds.

Clinical and epidemiological features in hospitalized young children with acute gastroenteritis in Taiwan: A multicentered surveillance through 2014-2017

BACKGROUND/PURPOSE

Acute gastroenteritis (AGE) remains a significant health issue in children. The worldwide evolution of pediatric AGE pathogens had been recorded since the introduction of rotavirus vaccine. Ten years after the rotavirus vaccine was introduced to the private sectors in Taiwan, a nationwide study was conducted to elucidate the epidemiological changes among major AGE pathogens.

METHODS

From January 2014 to December 2017, children younger than 5 years old, hospitalized with AGE at 10 hospitals across Taiwan were enrolled. Stool specimens were tested for Salmonella spp., Campylobacter spp., Clostridiodes difficile, norovirus, and rotavirus by polymerase chain reaction (PCR). The epidemiological and clinical information was collected.

RESULTS

Enteric pathogen were detected in 1983 (42.2%) of 4700 subjects, with Salmonella spp. (12.5%) being the leading cause of AGE, followed by norovirus (11.2%), rotavirus (8.7%), C. difficile (4.2%), Campylobacter spp. (1.0%), and a mixture of at least 2 of 5 above-mentioned pathogens (4.6%). The case distributions varied across different regions. In eastern Taiwan, rotavirus (21/131, 16.0%) remained the most common pathogen detected. The rotavirus vaccine uptake rate is significantly lower in patients with rotavirus AGE. Besides, rotavirus AGE frequently occurred in children with foreign parent(s), Taiwanese indigenous people, and those with the household monthly income < NT$ 60,000.

CONCLUSION

Salmonella spp. and norovirus were two major pathogens of pediatric AGE in Taiwan during 2014-17. Providing low-to middle-income households with free rotavirus vaccine nationwide and an industry-led act to reduce salmonellosis should be considered by the authorities.

Changing Antimicrobial Resistance and Epidemiology of Non-Typhoidal Salmonella Infection in Taiwanese Children

Non-typhoidal Salmonella (NTS) typically causes self-limiting diarrheal disease but may occasionally lead to invasive infection. This study investigated the epidemiology and antimicrobial resistance of children with NTS infection between 2012 and 2019. We retrospectively analyzed pediatric patients with NTS infections, confirmed by positive cultures, in a tertiary medical center in Taiwan in 2012 and 2019. Clinical features and laboratory data of the patients were collected. Changes in the serogroup category and antimicrobial resistance were also analyzed. Of the total 797 isolates collected, 55 had NTS bacteremia. Compared with the resistance rates in 2012, the rates of resistances to third-generation cephalosporin and ciprofloxacin were significantly higher in 2019 (4.1% vs 14.3%, P < 0.001; 1.9% vs 28.6%, P < 0.001), especially in groups B, D, and E. Moreover, we observed significantly higher antimicrobial resistance (25.3%) to third-generation cephalosporin, and approximately half the NTS isolates in the infant group were multidrug resistant – a higher rate than those of other age groups in 2019. Invasive NTS often presented with a longer fever duration, lower hemoglobin level and with no elevated C-reactive protein (P < 0.05). Non-invasive NTS isolates in 2019 were significantly more resistant to ceftriaxone (P < 0.001) and ciprofloxacin (P < 0.001) than those in 2012. The antimicrobial resistance of NTS in children has increased progressively in the past decade, and different serogroups exhibited different resistance patterns. During this period, infants showed the highest risk to get a third-generation cephalosporin-resistant NTS infection. The high rates of antimicrobial resistance among children with NTS in Taiwan merit continual surveillance.

Molecular Characterization of Cephalosporin-Resistant Salmonella Enteritidis ST11 Isolates Carrying blaCTX-M from Children with Diarrhea

Salmonella Enteritidis is an important foodborne pathogen with high prevalence of resistance to cephalosporins, imposing a serious threat to public health. Therefore, a total of 162 Salmonella Enteritidis isolates collected from child patients in China from 2007 to 2017 were characterized for their resistance to cephalosporins and investigated the transmission characteristics of cephalosporin resistance gene. We found that 15 (9.26%) isolates were all resistant to cefalotin (minimum inhibitory concentration [MIC] ≥512 μg/mL), ceftazidime (MIC 16-128 μg/mL), ceftriaxone (MIC 64 to ≥512 μg/mL), ceftiofur (MIC 64-256 μg/mL), and cefotaxime (MIC 64 to ≥512 μg/mL) with the possession of cephalosporin resistance genes bla_CTX-M-55 (n = 13), bla_CTX-M-101 (n = 1), and bla_CTX-M-153 (n = 1). Molecular typing further revealed that these 15 isolates belonged to sequence type ST11 and shared close pulsed-field gel electrophoresis patterns, suggesting the possibility of clonal spread in Salmonella Enteritidis interspecies. Furthermore, conjugation experiments were successfully performed in 13 of 15 isolates, and bla_CTX-M-55 was present on conjugative plasmids with sizes ranging from 54.7 to 173.4 kb. Compared with recipient Escherichia coli C600, transconjugants conferred elevated MICs for cephalosporins ranging from 2- to 2048-fold. The genetic structure surrounding of bla_CTX-M-55 gene in transconjugants were ΔISEcp1-bla_CTX-M-55-orf477 (n = 8) and ISEcp1-bla_CTX-M-55-orf477 (n = 3), respectively. Taken together, bla_CTX-M on the plasmids might contribute to cephalosporin resistance in Salmonella Enteritidis, and conjugative transfer of bla_CTX-M-55 might facilitate the spread of cephalosporin resistance in Salmonella Enteritidis. Hence, effective mitigation measurements are needed to reduce the threat caused by cephalosporin-resistant Salmonella Enteritidis to public health.

Correlation Between Pathogenic Determinants Associated with Clinically Isolated Non-Typhoidal Salmonella

Non-typhoidal and Typhoidal Salmonella are bacterial pathogens source of worldwide and major disease burden. Virulent determinants of specific serovars belonging to non-typhoidal Salmonella have been extensively studied in different models, yet the pathogenesis of this group of bacteria and the development of clinical symptoms globally remains underexplored. Herein, we implemented microbiological and molecular procedures to investigate isolate virulence traits and molecular diversity, likely in association with disease severity. Our results show that selected clinical isolates from a tertiary referring hospital, depending on the richness of the environment and isolate serotypes, exhibited different, and sometimes controversial, virulence properties. The tested strains were susceptible to Ceftriaxone (90%) with decreasing reactivity to Trimethoprim–Sulfamethoxazole (72%), Chloramphenicol (64%), Ampicillin (48%), Gentamicin (44%), and Ciprofloxacin (2%). Disc susceptibility results partially correlated with minimum inhibitory concentration (MIC); however, special attention must be given to antimicrobial treatment, as a rise in multi-resistant isolates to Trimethoprim–Sulfamethoxazole (2/38 µg/mL), Minocycline (8 µg/mL) and Ampicillin (16 µg/mL) has been noticed, with two isolates resistant to Ceftazidime (16 µg/mL). By comparison to previous molecular epidemiology studies, the variation in the gene profiles of endemic pathogens supports the need for continuous and up-to-date microbiological and molecular reports.

Febrile illness after a beach day: a case of salmonella bacteremia from oral exposure to a sand dollar

This case report discusses a rare presentation of salmonella bacteremia after an oral exposure to a sand dollar in a pediatric patient. A 2-year-old Hispanic male presented to the emergency department with a chief complaint of diarrhea and fever for 8 days after a family trip to Destin beach, Florida, during the sea turtle nesting season. The symptoms began a day after the patient took a bite on a sand dollar found on the beach that caused a small wound inside his cheek. The laboratory testing done in the emergency department was remarkable for blood and stool culture testing positive for non-typhoid salmonella. The sand dollar is a type of a sea urchin commonly found on sandy beaches and consists of an anatomical filtration system to consume sandy water. It could be inferred that the increased presence of sea turtles during the time of the patient's visit to Destin beach could have led to higher levels of salmonella in the seawater and consequently in the sand dollar, possibly leading to the inoculation of salmonella in this patient. To the best of our knowledge, this is a first case report that links oral exposure of the sand dollar to invasive salmonellosis.

Emergence of Salmonella enterica subsp. enterica serovar Chester in a rural area of Japan

In Japan, only one outbreak of Salmonella enterica subsp. enterica serovar Chester (S. Chester) has been confirmed in 1999. We performed a single-center retrospective case review of S. Chester infections that occurred in a rural area of Japan in 2016 (n=8). Case 5 and 6 occurred in twin infants who had contact with a pet dog. The dog's stool culture was positive for S. Chester. Pulsed-field gel electrophoresis and cluster analysis of S. Chester strains revealed that all the isolates appeared to be derived from the same genetic clone. Emergence of Salmonella infection can be overlooked if cases are not reported to health authorities; therefore, core hospitals should play a role to alert the occurrence of public health issue.

Dietary Fatty Acids and Host-Microbial Crosstalk in Neonatal Enteric Infection

Human milk is the best nutritional choice for infants. However, in instances where breastfeeding is not possible, infant formulas are used as alternatives. While formula manufacturers attempt to mimic the performance of human breast milk, formula-fed babies consistently have higher incidences of infection from diarrheal diseases than those breastfed. Differences in disease susceptibility, progression and severity can be attributed, in part, to nutritional fatty acid differences between breast milk and formula. Despite advances in our understanding of breast milk properties, formulas still present major differences in their fatty acid composition when compared to human breast milk. In this review, we highlight the role of distinct types of dietary fatty acids in modulating host inflammation, both directly and through the microbiome-immune nexus. We present evidence that dietary fatty acids influence enteric disease susceptibility and therefore, altering the fatty acid composition in formula may be a potential strategy to improve infectious outcomes in formula-fed infants.

Six-month follow up of a randomized clinical trial-phase I study in Indonesian adults and children: Safety and immunogenicity of Salmonella typhi polysaccharide-diphtheria toxoid (Vi-DT) conjugate vaccine

Introduction

There is a high global incidence of typhoid fever, with an annual mortality rate of 200,000 deaths. Typhoid fever also affects younger children, particularly in resource-limited settings in endemic countries. Typhoid vaccination is an important prevention tool against typhoid fever. However, the available polysaccharide typhoid vaccines are not recommended for children under 2 years of age. A new typhoid conjugate Vi-diphtheria toxoid (Vi-DT) vaccine has been developed for infant immunization. We aimed to define the safety and immunogenicity of the Vi-DT vaccine among adults and children in Indonesia.

Methods

An observational, blinded, comparative, randomized, phase I safety study in two age de-escalating cohorts was conducted in East Jakarta, Indonesia, from April 2017 to February 2018. We enrolled 100 healthy subjects in 2 age groups: adults and children (18–40 and 2–5 years old). These groups were randomized into study groups (Vi-DT vaccine), and comparator groups (Vi-polysaccharide (Vi-PS) vaccine and another additional vaccine) which was administered in 4 weeks apart. Subjects were followed up to six months.

Result

One hundred healthy adults and children subjects completed the study. The Vi-DT and Vi-PS vaccines showed no difference in terms of intensity of any immediate local and systemic events within 30 minutes post-vaccination. Overall, pain was the most common local reaction, and muscle pain was the most common systemic reaction in the first 72 hours. No serious adverse events were deemed related to vaccine administration. The first and second doses of the Vi-DT vaccine induced seroconversion and higher geometric mean titers (GMT) in all subjects compared to that of baseline. However, in terms of GMT, the second dose of Vi-DT did not induce a booster response.

Conclusion

The Vi-DT vaccine is safe and immunogenic in adults and children older than two years. A single dose of the vaccine is able to produce seroconversion and high GMT in all individuals.

Epidemiology of transmissible diseases: Array hybridization and next generation sequencing as universal nucleic acid-mediated typing tools

The magnitude of interest in the epidemiology of transmissible human diseases is reflected in the vast number of tools and methods developed recently with the expressed purpose to characterize and track evolutionary changes that occur in agents of these diseases over time. Within the past decade a new suite of such tools has become available with the emergence of the so-called "omics" technologies. Among these, two are exponents of the ongoing genomic revolution. Firstly, high-density nucleic acid probe arrays have been proposed and developed using various chemical and physical approaches. Via hybridization-mediated detection of entire genes or genetic polymorphisms in such genes and intergenic regions these so called "DNA chips" have been successfully applied for distinguishing very closely related microbial species and strains. Second and even more phenomenal, next generation sequencing (NGS) has facilitated the assessment of the complete nucleotide sequence of entire microbial genomes. This technology currently provides the most detailed level of bacterial genotyping and hence allows for the resolution of microbial spread and short-term evolution in minute detail. We will here review the very recent history of these two technologies, sketch their usefulness in the elucidation of the spread and epidemiology of mostly hospital-acquired infections and discuss future developments.

Effects of Vitellaria paradoxa (C.F. Gaertn.) aqueous leaf extract administration on Salmonella typhimurium-infected rats

BACKGROUND

The present study investigates the effects of Vitellaria paradoxa crude extract administration on Salmonella typhimurium infected Wistar rats.

METHODS

Rats were infected by single dose oral administration of Salmonella typhimurium (1.5×10⁸ CFU). Negative control groups were infected and treated orally with distilled water (vehicle), neutral control group were not infected, while the four test groups were treated up to 18 days with 55 mg/kg, 110 mg/kg, 220 mg/kg and 440 mg/kg body weight of aqueous extract of V. paradoxa respectively. The effects of this extract administration on serum markers (total protein, creatinine, transaminases, bilirubin and lipid profile) as well as acute toxicity test and phytochemical screening were also investigated.

RESULTS

Following in vivo studies, aqueous extract of V. paradoxa allowed to clear salmonellosis in previously infected rats within twelve days of treatment. Infection has resulted in a significant increase of transaminases activity. Besides, significant decrease was observed in liver and kidney relative weight and their protein content. Nevertheless, administration of this plant extract at higher doses has resulted in the correction of some of these injuries. Results obtained from acute toxicity study showed that mice administered with the aqueous leaf extract exhibited a mild reaction to noise and pinch; excreted watery discharges and the LD₅₀ value was 12.0 g/kg. In addition, the extract showed no toxic effect after 14 days. However, it may have a sedative effect or depressant effect on the central nervous system, may induce a decrease in plasma levels of algogenic substances, and may cause diarrhea at high doses. Phytochemical screening of the extract revealed the presence of flavonoids, alkaloids, tannins, phenols and polyphenols, saponins, anthocyanins, steroids and anthraquinones.

CONCLUSIONS

These results support the ethnomedicinal use of V. paradoxa, and suggest that its leave can be used in the management antibacterial phytomedicine.

Inverse trends of Campylobacter and Salmonella in Swiss surveillance data, 1988-2013

Clinical isolates of Campylobacter spp. and Salmonella spp. are notifiable in Switzerland. In 1995, Campylobacter replaced Salmonella as the most frequently reported food-borne pathogen. We analysed notification data (1988-2013) for these two bacterial, gastrointestinal pathogens of public health importance in Switzerland. Notification rates were calculated using data for the average resident population. Between 1988 and 2013, notified campylobacteriosis cases doubled from 3,127 to 7,499, while Salmonella case notifications decreased, from 4,291 to 1,267. Case notifications for both pathogens peaked during summer months. Campylobacter infections showed a distinct winter peak, particularly in the 2011/12, 2012/13 and 2013/14 winter seasons. Campylobacter case notifications showed more frequent infection in males than females in all but 20-24 year-olds. Among reported cases, patients' average age increased for campylobacteriosis but not for salmonellosis. The inverse trends observed in case notifications for the two pathogens indicate an increase in campylobacteriosis cases. It appears unlikely that changes in patients' health-seeking or physicians' testing behaviour would affect Campylobacter and Salmonella case notifications differently. The implementation of legal microbiological criteria for foodstuff was likely an effective means of controlling human salmonellosis. Such criteria should be decreed for Campylobacter, creating incentives for producers to lower Campylobacter prevalence in poultry.

Vaccines for viral and bacterial pathogens causing acute gastroenteritis: Part II: Vaccines for Shigella, Salmonella, enterotoxigenic E. coli (ETEC) enterohemorragic E. coli (EHEC) and Campylobacter jejuni

In Part II we discuss the following bacterial pathogens: Shigella, Salmonella (non-typhoidal), diarrheogenic E. coli (enterotoxigenic and enterohemorragic) and Campylobacter jejuni. In contrast to the enteric viruses and Vibrio cholerae discussed in Part I of this series, for the bacterial pathogens described here there is only one licensed vaccine, developed primarily for Vibrio cholerae and which provides moderate protection against enterotoxigenic E. coli (ETEC) (Dukoral(®)), as well as a few additional candidates in advanced stages of development for ETEC and one candidate for Shigella spp. Numerous vaccine candidates in earlier stages of development are discussed.

Salmonella Infections in Childhood

Salmonella are gram-negative bacilli within the family Enterobacteriaceae. They are the cause of significant morbidity and mortality worldwide. Animals (pets) are an important reservoir for nontyphoidal Salmonella, whereas humans are the only natural host and reservoir for Salmonella Typhi. Salmonella infections are a major cause of gastroenteritis worldwide. They account for an estimated 2.8 billion cases of diarrheal disease each year. The transmission of Salmonella is frequently associated with the consumption of contaminated water and food of animal origin, and it is facilitated by conditions of poor hygiene. Nontyphoidal Salmonella infections have a worldwide distribution, whereas most typhoidal Salmonella infections in the United States are acquired abroad. In the United States, Salmonella is a common agent for food-borne–associated infections. Several outbreaks have been identified and are most commonly associated with agricultural products. Nontyphoidal Salmonella infection is usually characterized by a self-limited gastroenteritis in immunocompetent hosts in industrialized countries, but it may also cause invasive disease in vulnerable individuals (eg, children less than 1 year of age, immunocompromised). Antibiotic treatment is not recommended for treatment of mild to moderate gastroenteritis by nontyphoidal Salmonella in immunocompetent adults or children more than 1 year of age. Antibiotic treatment is recommended for nontyphoidal Salmonella infections in infants less than 3 months of age, because they are at higher risk for bacteremia and extraintestinal complications. Typhoid (enteric) fever and its potential complications have a significant impact on children, especially those who live in developing countries. Antibiotic treatment of typhoid fever has become challenging because of the emergence of Salmonella Typhi strains that are resistant to classically used first-line agents: ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol. The choice of antibiotics for the management of typhoid fever should be guided by the local resistance pattern. Recommendations include using an extended spectrum cephalosporin, azithromycin, or a fluoroquinolone. Fecal carriage of Salmonella is an important factor in the spread of the organism to healthy individuals. The most important measures to prevent the spread and outbreaks of Salmonella infections and typhoid fever are adequate sanitation protocols for food processing and handling as well as hand hygiene. In the United States, 2 vaccines are commercially available against Salmonella Typhi. The WHO recommends the use of these vaccines in endemic areas and for outbreak control.