Incidence and prognosis of non-typhoid Salmonella bacteraemia in Denmark: a 10-year county-based follow-up study

A Population-Based Study on the Incidence, Risk Factors, and Outcome of Salmonella Bloodstream Infections in South Sweden 2012-2022

INTRODUCTION

Invasive infections caused by Salmonella are a significant global health concern. This population-based study aimed to comprehensively analyze invasive Salmonella infections in South Sweden, focusing on incidence, clinical presentation, risk factors, and outcomes.

METHODS

This population-based observational cohort study, conducted from 2012 to 2022, included all patients with Salmonella bloodstream infections (BSI) in the Skåne region, South Sweden. A control group consisted of patients with positive stool cultures/PCR for Salmonella but without BSI. Data were collected following a predefined study protocol from medical records. Standardized statistical analyses assessed patient characteristics, clinical presentation, and outcomes.

RESULTS

Between 2012 and 2022, 149 patients with SBSI were identified, with the majority having non-typhoidal Salmonella (NTS) infections (95%). A declining trend in the incidence of SBSI was observed, with the highest incidence in 2012 (1.5 per 100,000 person-years) and the lowest in 2020 (0.3 per 100,000 person-years). Patients with BSI were more likely to be older, have comorbidities, be immunosuppressed, and use proton pump inhibitors (PPIs). Additionally, patients with BSI presented with fewer gastrointestinal symptoms, had a higher respiratory rate, lower saturation, and higher SOFA scores, suggesting a more septic presentation. Patients with SBSI had significantly longer hospital stays and higher 30-day, 90-day, 180-day, and 365-day mortality rates compared to the control group.

CONCLUSION

Invasive Salmonella infections are rare in South Sweden. In a cohort of enteric and invasive Salmonella infection, the absence of classic gastroenteritis symptoms increases the risk of Salmonella bloodstream infection. This study highlights the importance of distinguishing between clinical presentations to guide appropriate treatment when Salmonella infection is suspected. The declining trend in incidence, particularly associated with international travel, necessitates further investigation to understand contributing factors.

Non-typhoidal Salmonella bacteremia: comparison of adults and children in a single medical center

Introduction. Non-typhoidal Salmonella (NTS) bacteremia can cause significant morbidity and mortality. There is high incidence of Salmonellosis in the Middle East, including Israel, but there is a paucity of data on the clinical and epidemiological features of children in comparison to adults.Hypothesis/Gap Statement. Previous studies describing the differences between paediatric and adult populations with Salmonella bacteremia are sparse.Aim. This study's aim was to describe the differences between adults and children with NTS bacteremia.Methodology. All records of patients with NTS bacteremia between 1 January 1998 and 31 July 2020 were reviewed. Data regarding clinical manifestations and laboratory results were extracted from the medical records; records of children (aged <18 years) were compared with those of adults.Results. Records for 137 cases of Salmonella bacteremia (69 adults and 68 children, aged 2 days to 98 years) were reviewed. Seventy nine (58 %) patients had concomitant gastrointestinal symptoms. Fifty-eight (84 %) adults and 13 (19 %) children had underlying conditions (P<0.001). Eighteen patients died, none of whom was a child. Over the study period, most of the children (n=46, 67 %) but only five adults were discharged from the emergency department on their first visit to the ED.Conclusions. The main characteristics of NTS bacteremia in children compared to adults, are higher rates of prior discharge from emergency department, higher rate of gastrointestinal symptoms and better prognosis.

[Invasive Infections Caused by Nontyphoidal Salmonella sp. in Childhood Clinical Features and Incidence Trends between 1994 and 2014]

Little is known about the clinical characteristics of invasive infections caused by nontyphoidal Salmonella sp. in childhood and the temporal changes of their incidence over a long period of time. In order to clarify these issues, we retrospectively analyzed the records of 17 such infected children admitted between August 1994 and December 2014 to our center. We divided the study period into the first (1994-1999), second (2000-2004), third (2005-2009), and fourth (2010-2014) periods. The ages of the 17 patients ranged from 2 days to 13 years. Clinical syndrome included bacteremia with enteritis (n = 13), followed by bacteremia or sepsis alone, (n = 2), osteomyelitis (n = 1), and meningitis (n = 1). The affected patient numbers in the first to fourth periods were 10, 5, 2, and 0, respectively, and the decreasing trend was significant (trend p < 0.001). This significant trend held up even after correction by the number of in-patients during each quarter period (trend p = 0.009). In the 14 cases of bacteremia with or without enteritis, excluding two neonatal cases and one case of osteomyelitis, most patients (n = 13, 93%) had WBC of <15,000/µL with a wide range of serum CRP levels (0.8-20.4mg/dL) on admission. Thus, it was very difficult to diagnose these bacteremia cases based on blood tests alone, and we needed to consider such risk factors of bacteremia as high fever, poor general condition, and younger age. O group serotypes of the isolates were as follows: O9 (n = 11), O7 (n = 5), and O4 (n = 1). Of the 15 strains evaluated, two strains were resistant to ampicillin and one each was resistant and intermediately resistant to fosfomycin. All strains were susceptible to cefotaxime, ofloxacin or levofloxacin, and trimethoprim-sulfamethoxazole. We were also presented with two rare cases : one involved sepsis due to vertical transmission and the other involved meningitis. The latter case had clinical relevance in that recurrence developed 3 weeks after treatment with susceptible antibiotics. In conclusion, this study is the first report on invasive infections caused by nontyphoidal Salmonella sp. in childhood in Japan, and provides important information on their clinical features and incidence trends over the last 20 years.

Global burden of invasive nontyphoidal Salmonella disease, 2010(1)

Nontyphoidal Salmonella is a major cause of bloodstream infections worldwide, and HIV-infected persons and malaria-infected children are at increased risk for the disease. We conducted a systematic literature review to obtain age group-specific, population-based invasive nontyphoidal Salmonella (iNTS) incidence data. Data were categorized by HIV and malaria prevalence and then extrapolated by using 2010 population data. The case-fatality ratio (CFR) was determined by expert opinion consensus. We estimated that 3.4 (range 2.1-6.5) million cases of iNTS disease occur annually (overall incidence 49 cases [range 30-94] per 100,000 population). Africa, where infants, young children, and young adults are most affected, has the highest incidence (227 cases [range 152-341] per 100,000 population) and number of cases (1.9 [range 1.3-2.9] million cases). An iNTS CFR of 20% yielded 681,316 (range 415,164-1,301,520) deaths annually. iNTS disease is a major cause of illness and death globally, particularly in Africa. Improved understanding of the epidemiology of iNTS is needed.

Population-based epidemiology and microbiology of community-onset bloodstream infections

Bloodstream infection (BSI) is a major cause of infectious disease morbidity and mortality worldwide. While a positive blood culture is mandatory for establishment of the presence of a BSI, there are a number of determinants that must be considered for establishment of this entity. Community-onset BSIs are those that occur in outpatients or are first identified <48 h after admission to hospital, and they may be subclassified further as health care associated, when they occur in patients with significant prior health care exposure, or community associated, in other cases. The most common causes of community-onset BSI include Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Antimicrobial-resistant organisms, including methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase/metallo-β-lactamase/carbapenemase-producing Enterobacteriaceae, have emerged as important etiologies of community-onset BSI.

Non-typhoidal Salmonella bacteraemia in elderly patients: an increased risk for endovascular infections, osteomyelitis and mortality

Non-typhoidal Salmonella (NTS) is a common pathogen causing foodborne infections, bacteraemia, and extra-intestinal focal infections (EFIs) in humans. The study compares the clinical characteristics of elderly patients with NTS bacteraemia with those of young adults. Of 272 adults with NTS bacteraemia identified in this study, 162 (59·6%) were aged ⩾55 years. EFIs were observed in 36% of the 162 patients. The most common EFIs in the elderly patients (⩾55 years) was mycotic aneurysm, followed by pulmonary infections and bone/joint infections. Elderly patients more often had chronic heart, lung, renal and malignant diseases, had more EFIs, and a higher 30-day mortality rate. Independent factors of 30-day mortality in elderly patients were solid-organ tumour [adjusted odds ratio (aOR) 4·4, P=0·003], mycotic aneurysm (aOR 3·7, P=0·023) and shock (aOR 12·1, P<0·0001). HIV infection, autoimmune diseases, and receipt of immunosuppressive therapy were more often observed in young patients.

Ultra-fast and sensitive detection of non-typhoidal Salmonella using microwave-accelerated metal-enhanced fluorescence ("MAMEF")

Certain serovars of Salmonella enterica subsp. enterica cause invasive disease (e.g., enteric fever, bacteremia, septicemia, meningitis, etc.) in humans and constitute a global public health problem. A rapid, sensitive diagnostic test is needed to allow prompt initiation of therapy in individual patients and for measuring disease burden at the population level. An innovative and promising new rapid diagnostic technique is microwave-accelerated metal-enhanced fluorescence (MAMEF). We have adapted this assay platform to detect the chromosomal oriC locus common to all Salmonella enterica subsp. enterica serovars. We have shown efficient lysis of biologically relevant concentrations of Salmonella spp. suspended in bacteriological media using microwave-induced lysis. Following lysis and DNA release, as little as 1 CFU of Salmonella in 1 ml of medium can be detected in <30 seconds. Furthermore the assay is sensitive and specific: it can detect oriC from Salmonella serovars Typhi, Paratyphi A, Paratyphi B, Paratyphi C, Typhimurium, Enteritidis and Choleraesuis but does not detect Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Streptococcus pneumoniae, Haemophilus influenzae or Acinetobacter baumanii. We have also performed preliminary experiments using a synthetic Salmonella oriC oligonucleotide suspended in whole human blood and observed rapid detection when the sample was diluted 1∶1 with PBS. These pre-clinical data encourage progress to the next step to detect Salmonella in blood (and other ordinarily sterile, clinically relevant body fluids).

Salmonella enterica bacteraemia: a multi-national population-based cohort study

Background

Salmonella enterica is an important emerging cause of invasive infections worldwide. However, population-based data are limited. The objective of this study was to define the occurrence of S. enterica bacteremia in a large international population and to evaluate temporal and regional differences.

Methods

We conducted population-based laboratory surveillance for all salmonella bacteremias in six regions (annual population at risk 7.7 million residents) in Finland, Australia, Denmark, and Canada during 2000-2007.

Results

A total of 622 cases were identified for an annual incidence of 1.02 per 100,000 population. The incidence of typhoidal (serotypes Typhi and Paratyphi) and non-typhoidal (other serotypes) disease was 0.21 and 0.81 per 100,000/year. There was major regional and moderate seasonal and year to year variability with an increased incidence observed in the latter years of the study related principally to increasing rates of non-typhoidal salmonella bacteremias. Advancing age and male gender were significant risk factors for acquiring non-typhoidal salmonella bacteremia. In contrast, typhoidal salmonella bacteremia showed a decreasing incidence with advancing age and no gender-related excess risk.

Conclusions

Salmonella enterica is an important emerging pathogen and regional determinants of risk merits further investigation.

Bacteraemia as a result of Campylobacter species: a population-based study of epidemiology and clinical risk factors

Invasive disease as a result of Campylobacter is rarely reported. We reviewed 46 cases of blood stream infection with Campylobacter in a Danish population with complete follow-up. The incidence was 2.9 per 1 million person-years with a peak incidence in the age group above 80 years. In the population, the ratio of notified bacteraemia/enteritis patients with Campylobacter infection was 0.004. Patients with bacteraemia were older and had higher comorbidity, e.g. alcoholism, immunosuppression, previous gastrointestinal surgery or HIV infection. We found 26% of blood isolates resistant to ciprofloxacin. The length of hospitalization was significantly longer in bacteraemia patients, whereas the outcome was favourable with 28-day mortality of 4% in bacteraemia patients and 1% in enteritis patients. None of the bacteraemia patients relapsed within 365-day follow-up.

Salmonella gastroenteritis complicated with bacteremia and ruptured cholangitis in an infant with congenital choledochal cyst

Choledochal cyst perforation associated with bacteria is very rare. An 11-month-old infant was admitted to hospital because of fever and bloody diarrhea. Abdominal ultrasonogram revealed a choledochal cyst. Despite antibiotic treatment with initial improvement, jaundice and abdominal tenderness developed 6 days later. Ultrasonography-guided aspiration yielded bile-stained ascites. Emergency operation confirmed the diagnosis of choledochal cyst with perforation. Blood, stool, and bile juice cultures all yielded Salmonella typhimurium. To our knowledge, it is rare that a child with choledochal cyst has systemic infection with S. typhimurium and cyst perforation. We propose that systemic Salmonella infection carries a risk of cyst perforation in patients with congenital choledochal cyst.

High incidence of intravascular focus in nontyphoid Salmonella bacteremia in the age group above 50 years: a population-based study

Questions regarding the relative frequency of vascular complications in nontyphoid Salmonella bacteremia are pending, and the true population-based age-related incidence is not known. We reviewed all cases of nontyphoid Salmonella bacteremia during a 10-year period from 1994 through 2003 in a well-defined population of 492,843 residents in North Jutland County, Denmark. 77 of a total of 111 cases occurred in patients >50 years old. In this age group, five cases of mycotic aneurysm and two cases of endocarditis were documented, corresponding to a 9% occurrence. The annual incidence rate of endovascular nontyphoid Salmonella infection in this age group was 4.4 per 1,000,000 person years. The mortality was 43% in cases with endovascular infection, and surgical procedures were important for survival. We conclude that in patients older than 50 years, detection of nontyphoid Salmonella bloodstream infection should be followed by examinations for mycotic aneurysms and endocarditis.