Research on Invasive Nontyphoidal Salmonella Disease and Developments Towards Better Understanding of Epidemiology, Management, and Control Strategies

Clinical Characteristics, Serotypes and Antimicrobial Resistance of Invasive Salmonella Infections in HIV-Infected Patients in Hangzhou, China, 2012-2023

Purpose

Developing countries, invasive Salmonella infections can cause considerable morbidity and mortality. There is a relative lack of data on coinfection with Salmonella in HIV-infected patients in Hangzhou, China.

Patients and Methods

In this study, we manually collected case data of patients aged >18 years with HIV combined with invasive Salmonella infections admitted to Xixi Hospital in Hangzhou from January 2012 to August 2023 by logging into the Hospital Information System, and identified 26 strains of invasive Salmonella using a fully automated microbiological identification system and mass spectrometer. Serotypes were determined using Salmonella diagnostic sera based on the White-Kauffmann-Le Minor scheme. Drug sensitivity tests were performed using the automated instrumental method of the MIC method.

Results

A total of 26 HIV-infected patients with invasive Salmonella coinfections were identified over 11 years; Twenty-five of the 26 patients (96.2%) were males, with a mean age of 33.5 years (26.75, 46.75). The most common type of infection was bloodstream infection (92.3%). One patient also had concomitant meningitis and osteoarthritis, followed by pneumonia (7.7%). The presence of multiple bacterial infections or even multiple opportunistic pathogens was clearly established in 7 (26.9%) patients. Three (11.6%) patients were automatically discharged from the hospital with deterioration of their condition, and one (3.8%) patient died. Salmonella enteritidis was the most common serotype in 6 patients (23.2%), and Salmonella Dublin was the most common serotype in 6 patients (23.2%). Drug sensitivity results revealed multidrug resistance in a total of 8 (30.8%) patients.

Conclusion

The clinical presentation of invasive Salmonella infection in HIV patients is nonspecific and easily masked by other mixed infections. A CD4+ count <100 cells/µL and comorbid intestinal lesions may be important susceptibility factors. Salmonella has a high rate of resistance to common antibiotics, and the risk of multidrug resistance should not be ignored.

Development of a rapid diagnostic test based on loop-mediated isothermal amplification to identify the most frequent non-typhoidal Salmonella serovars from culture

Identification of Salmonella serovars is performed by conventional seroagglutination or sequencing. These methods are labor-intensive and require technical experience. An easy-to-perform assay allowing the timely identification of the most common non-typhoidal serovars (NTS) is needed. In this study, a molecular assay based on loop-mediated isothermal amplification (LAMP) targeting specific gene sequences of Salmonella Enteritidis, S. Typhimurium, S. Infantis, S. Derby, and S. Choleraesuis has been developed for rapid serovar identification from cultured colonies. A total of 318 Salmonella strains and 25 isolates of other Enterobacterales species that served as negative controls were analyzed. All S. Enteritidis (n = 40), S. Infantis (n = 27), and S. Choleraesuis (n = 11) strains were correctly identified. Seven out of 104 S. Typhimurium and 10 out of 38 S. Derby strains missed a positive signal. Cross-reactions of the gene targets were only rarely observed and restricted to the S. Typhimurium primer set (5 false-positives). Sensitivity and specificity of the assay compared to seroagglutination were as follows: 100% and 100% for S. Enteritidis, 93.3% and 97.7% for S. Typhimurium, 100% and 100% for S. Infantis, 73.7% and 100% for S. Derby, and 100% and 100% for S. Choleraesuis, respectively. With results available in just a few minutes of hands-on time and a test run time of 20 min, the LAMP assay developed here may be a useful tool for the rapid identification of common Salmonella NTS in daily routine diagnostics.

Uptake of Plasmodium chabaudi hemozoin drives Kupffer cell death and fuels superinfections

Kupffer cells (KCs) are self-maintained tissue-resident macrophages that line liver sinusoids and play an important role on host defense. It has been demonstrated that upon infection or intense liver inflammation, KCs might be severely depleted and replaced by immature monocytic cells; however, the mechanisms of cell death and the alterations on liver immunity against infections deserves further investigation. We explored the impact of acute Plasmodium infection on KC biology and on the hepatic immune response against secondary infections. Similar to patients, infection with Plasmodium chabaudi induced acute liver damage as determined by serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) elevation. This was associated with accumulation of hemozoin, increased of proinflammatory response and impaired bacterial and viral clearance, which led to pathogen spread to other organs. In line with this, mice infected with Plasmodium had enhanced mortality during secondary infections, which was associated with increased production of mitochondrial superoxide, lipid peroxidation and increased free iron within KCs-hallmarks of cell death by ferroptosis. Therefore, we revealed that accumulation of iron with KCs, triggered by uptake of circulating hemozoin, is a novel mechanism of macrophage depletion and liver inflammation during malaria, providing novel insights on host susceptibility to secondary infections. Malaria can cause severe liver damage, along with depletion of liver macrophages, which can predispose individuals to secondary infections and enhance the chances of death.

Clinical profiles and antimicrobial resistance patterns of invasive Salmonella infections in children in China

Invasive Salmonella infections result in a significant burden of disease including morbidity, mortality, and financial cost in many countries. Besides typhoid fever, the clinical impact of non-typhoid Salmonella infections is increasingly recognized with the improvement of laboratory detection capacity and techniques. A retrospective multicenter study was conducted to analyze the clinical profiles and antimicrobial resistance patterns of invasive Salmonella infections in hospitalized children in China during 2016-2018. A total of 130 children with invasive Salmonella infections were included with the median age of 12 months (range: 1-144 months). Seventy-nine percent of cases occurred between May and October. Pneumonia was the most common comorbidity in 33 (25.4%) patients. Meningitis and septic arthritis caused by nontyphoidal Salmonella (NTS) infections occurred in 12 (9.2%) patients and 5 (3.8%) patients. Patients < 12 months (OR: 16.04) and with septic shock (OR: 23.4), vomit (OR: 13.33), convulsion (OR: 15.86), C-reactive protein (CRP) ≥ 40 g/L (OR: 5.56), and a higher level of procalcitonin (PCT) (OR: 1.05) on admission were statistically associated to an increased risk of developing meningitis. Compared to 114 patients with NTS infections, 16 patients with typhoid fever presented with higher levels of CRP and PCT (P < 0.05). The rates of resistance to ampicillin, sulfamethoxazole/trimethoprim, ciprofloxacin, and ceftriaxone among Salmonella Typhi and NTS isolates were 50% vs 57.3%, 9.1% vs 24.8%, 0% vs 11.2%, and 0% vs 9.9%, respectively. NTS has been the major cause of invasive Salmonella infections in Chinese children and can result in severe diseases. Antimicrobial resistance among NTS was more common.

Antimicrobial Resistance Rates and Surveillance in Sub-Saharan Africa: Where Are We Now?

Introduction

Although antimicrobials have traditionally been used to treat infections and improve health outcomes, resistance to commonly used antimicrobials has posed a major challenge. An estimated 700,000 deaths occur globally every year as a result of infections caused by antimicrobial-resistant pathogens. Antimicrobial resistance (AMR) also contributes directly to the decline in the global economy. In 2019, sub-Saharan Africa (SSA) had the highest mortality rate (23.5 deaths per 100,000) attributable to AMR compared to other regions.

Methods

We searched PubMed for articles relevant to AMR in pathogens in the WHO-GLASS list and in other infections of local importance in SSA. In this review, we focused on AMR rates and surveillance of AMR for these priority pathogens and some of the most encountered pathogens of public health significance. In addition, we reviewed the implementation of national action plans to mitigate against AMR in countries in SSA.

Results and Discussion

The SSA region is disproportionately affected by AMR, in part owing to the prevailing high levels of poverty, which result in a high burden of infectious diseases, poor regulation of antimicrobial use, and a lack of alternatives to ineffective antimicrobials. The global action plan as a strategy for prevention and combating AMR has been adopted by most countries, but fewer countries are able to fully implement country-specific action plans, and several challenges exist in many settings.

Conclusion

A concerted One Health approach will be required to ramp up implementation of action plans in the region. In addition to AMR surveillance, effective implementation of infection prevention and control, water, sanitation, and hygiene, and antimicrobial stewardship programs will be key cost-effective strategies in helping to tackle AMR.

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.

The genomic epidemiology of multi-drug resistant invasive non-typhoidal Salmonella in selected sub-Saharan African countries

Background

Invasive non-typhoidal Salmonella (iNTS) is one of the leading causes of bacteraemia in sub-Saharan Africa. We aimed to provide a better understanding of the genetic characteristics and transmission patterns associated with multi-drug resistant (MDR) iNTS serovars across the continent.

Methods

A total of 166 iNTS isolates collected from a multi-centre surveillance in 10 African countries (2010–2014) and a fever study in Ghana (2007–2009) were genome sequenced to investigate the geographical distribution, antimicrobial genetic determinants and population structure of iNTS serotypes–genotypes. Phylogenetic analyses were conducted in the context of the existing genomic frameworks for various iNTS serovars. Population-based incidence of MDR-iNTS disease was estimated in each study site.

Results

Salmonella Typhimurium sequence-type (ST) 313 and Salmonella Enteritidis ST11 were predominant, and both exhibited high frequencies of MDR; Salmonella Dublin ST10 was identified in West Africa only. Mutations in the gyrA gene (fluoroquinolone resistance) were identified in S. Enteritidis and S. Typhimurium in Ghana; an ST313 isolate carrying bla_CTX-M-15 was found in Kenya. International transmission of MDR ST313 (lineage II) and MDR ST11 (West African clade) was observed between Ghana and neighbouring West African countries. The incidence of MDR-iNTS disease exceeded 100/100 000 person-years-of-observation in children aged <5 years in several West African countries.

Conclusions

We identified the circulation of multiple MDR iNTS serovar STs in the sampled sub-Saharan African countries. Investment in the development and deployment of iNTS vaccines coupled with intensified antimicrobial resistance surveillance are essential to limit the impact of these pathogens in Africa.