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

Age-associated impairment of T cell immunity is linked to sex-dimorphic elevation of N-glycan branching

Impaired T cell immunity with aging increases mortality from infectious disease. The branching of Asparagine-linked glycans is a critical negative regulator of T cell immunity. Here we show that branching increases with age in females more than males, in naïve more than memory T cells, and in CD4+ more than CD8+ T cells. Female sex hormones and thymic output of naïve T cells (TN) decrease with age, however neither thymectomy nor ovariectomy altered branching. Interleukin-7 (IL-7) signaling was increased in old female more than male mouse TN cells, and triggered increased branching. N-acetylglucosamine, a rate-limiting metabolite for branching, increased with age in humans and synergized with IL-7 to raise branching. Reversing elevated branching rejuvenated T cell function and reduced severity of Salmonella infection in old female mice. These data suggest sex-dimorphic antagonistic pleiotropy, where IL-7 initially benefits immunity through TN maintenance but inhibits TN function by raising branching synergistically with age-dependent increases in N-acetylglucosamine.

Sex Differences in Salmonellosis Incidence Rates-An Eight-Country National Data-Pooled Analysis

BACKGROUND

There are few studies on sex differences in the incidence rates (IR) for salmonellosis over several countries by age and time period. The purpose of this study was to explore the extent and consistency of the sex and age-specific differences.

METHODS

We analyzed national data from eight countries between 1994 and 2016. We computed country-specific male to female incidence rate ratios (IRRs) for each age group and pooled the data using meta-analytic methods. Variations of the IRRs by age, country and time period were evaluated using meta-regression.

RESULTS

The pooled male to female incidence RRs for ages 0-1, 1-4, 5-9 and 10-14, were 1.04 (1.02-1.06), 1.02 (1.01-1.03), 1.07 (1.05-1.08) and 1.28 (1.23-1.33), respectively. For the ages 15-44 and 45-64, the incidence rates were significantly higher in females. Meta-regression analyses indicate that age groups contributed most of the variation in the male to female IRRs.

CONCLUSIONS

We suggest that genetic and hormonal factors and interactions between hormones and gut microbiota could contribute to the sex differences observed in young children. These findings should provide clues about the mechanisms of the infection, and should be useful in targeting treatments and development of vaccines.

HIGHLIGHTS

(1) This manuscript provides consistent estimates of the excess salmonellosis incidence rates in male children up to age 15, which suggests an impact of sex hormones or genetic differences. (2) Our findings should promote the further investigations on sex-related determinants of infectious diseases.

Acute Bacterial Gastroenteritis

Acute bacterial gastroenteritis is among the most common infections worldwide, with millions of infections annually in the United States. Much of the illness is foodborne, occurring as both sporadic cases and large multistate outbreaks. Pathogen evolution through genetic exchange of virulence traits and antibiotic resistance determinants poses challenges for empiric therapy. Culture-independent diagnostic tests in clinical laboratories afford rapid diagnosis and expanded identification of pathogens. However, cultures remain important to generate sensitivity data and strain archiving for outbreak investigations. Most infections are self-limited, permitting judicious selection of antibiotic use in more severe forms of illness.

Age-related alterations in human gut CD4 T cell phenotype, T helper cell frequencies, and functional responses to enteric bacteria

Intestinal lamina propria (LP) CD4 T cells play critical roles in maintaining intestinal homeostasis and in immune responses to enteric microbes, yet little is known regarding whether they contribute to age-associated intestinal immune dysfunction. In this study, we evaluated the direct ex vivo frequency, activation/inhibitory phenotype, death profiles, and in vitro functional responses of human jejunum LP CD4 T cells, including Th1, Th17, and Th22 subsets isolated from younger (<45 years) and older (>65years) persons. Expression of the co-inhibitory molecule CTLA-4 was significantly lower in older CD4 T cells, whereas expression of HLA-DR, CD38, CD57, and PD-1 were not significantly different between groups. Total CD4 T cell frequencies were similar between age groups, but lower frequencies and numbers of Th17 cells were observed directly ex vivo in older samples. Older Th17 and Th1 cells proliferated to a lesser degree following in vitro exposure to bacterial antigens vs. their younger counterparts. Levels of spontaneous cell death were increased in older CD4 T cells; however, cellular death profiles following activation did not differ based on age. Thus, small intestinal CD4 T cells from older persons have altered phenotypic and functional profiles including reduced expression of a co-inhibitory molecule, increased spontaneous cell death, and both reduced frequencies and altered functional responses of specific Th cell subsets. These changes may contribute to altered intestinal homeostasis and loss of protective gut immunity with aging.

Epidemiology and Outcomes of Nontyphoidal Salmonella Bacteremias from England, 2004 to 2015

Nontyphoidal Salmonella (NTS) bacteremia causes hospitalization and high morbidity and mortality. We linked Gastrointestinal Bacteria Reference Unit (GBRU) data to the Hospital Episode Statistics (HES) data set to study the trends and outcomes of NTS bacteremias in England between 2004 and 2015. All confirmed NTS isolates from blood from England submitted to GBRU between 1 January 2004 and 31 December 2015 were deterministically linked to HES records. Adjusted odds ratios (AOR), proportions, and confidence intervals (CI) were calculated to describe differences in age, sex, antibiotic resistance patterns, and serotypes over time. Males, neonates, and adults above 65 years were more likely to have NTS bacteremia (AOR, 1.54 [95% CI, 1.46 to 1.67]; 2.57 [95% CI, 1.43 to 4.60]; and 3.56 [95% CI, 3.25 to 3.90], respectively). Proportions of bacteremia increased from 1.41% in 2004 to 2.67% in 2015. Thirty-four percent of all blood isolates were resistant to a first-line antibiotic, and 1,397 (56%) blood isolates were linked to an HES record. Of the patients with NTS bacteremia, 969 (69%) had a cardiovascular condition and 155 (12%) patients died, out of which 120 (77%) patients were age 65 years and above. NTS bacteremia mainly affects older people with comorbidities placing them at increased risk of prolonged hospital stay and death. Resistance of invasive NTS to first-line antimicrobial agents appeared to be stable in England, but the emergence of resistance to last-resort antibiotics, such as colistin, requires careful monitoring.

An Unusual Case of Mycotic Popliteal Aneurysm Presenting as Recurrent Salmonella enteritidis Bacteraemia

We describe a patient with a Salmonella enteritidis mycotic aneurysm. A 91-year-old man presented with recurrent episodes of S. enteritidis bacteraemia 2 months apart. During the second presentation, he underwent magnetic resonance imaging of the left lower limb that revealed rupture of the popliteal artery with a popliteal fossa collection. This was aspirated and cultures grew S. enteritidis. He underwent endovascular stenting and received a prolonged course of antibiotics. Popliteal artery mycotic aneurysm should be considered as a differential in patients presenting with unilateral painful leg swelling and bacteraemia from microorganisms with a propensity for endovascular infections.

Mass spectrometry imaging identifies palmitoylcarnitine as an immunological mediator during Salmonella Typhimurium infection

Salmonella Typhimurium causes a self-limiting gastroenteritis that may lead to systemic disease. Bacteria invade the small intestine, crossing the intestinal epithelium from where they are transported to the mesenteric lymph nodes (MLNs) within migrating immune cells. MLNs are an important site at which the innate and adaptive immune responses converge but their architecture and function is severely disrupted during S. Typhimurium infection. To further understand host-pathogen interactions at this site, we used mass spectrometry imaging (MSI) to analyse MLN tissue from a murine model of S. Typhimurium infection. A molecule, identified as palmitoylcarnitine (PalC), was of particular interest due to its high abundance at loci of S. Typhimurium infection and MLN disruption. High levels of PalC localised to sites within the MLNs where B and T cells were absent and where the perimeter of CD169⁺ sub capsular sinus macrophages was disrupted. MLN cells cultured ex vivo and treated with PalC had reduced CD4⁺CD25⁺ T cells and an increased number of B220⁺CD19⁺ B cells. The reduction in CD4⁺CD25⁺ T cells was likely due to apoptosis driven by increased caspase-3/7 activity. These data indicate that PalC significantly alters the host response in the MLNs, acting as a decisive factor in infection outcome.

An Unusual Case of Septic Arthritis of the Hip

Non-typhoidal Salmonella, particularly Salmonella enterica serovar typhimurium is food borne pathogen causing mild self-limiting diarrhoea in healthy adults. It can occasionally cause extraintestinal focal infection in susceptible patients. Salmonella, as the aetiological agent of osteomyelitis and septic arthritis is rare and has been mostly reported in patients with sickle cell disease or thalassaemia. We report a case of septic arthritis by Salmonellatyphimurium in an immunocompromised patient who was successfully treated following timely isolation and identification of the aetiological agent.

Antimicrobial Resistance Among Nontyphoidal Salmonella Isolated From Blood in the United States, 2003-2013

BACKGROUND

Salmonella causes an estimated 100 000 antimicrobial-resistant infections annually in the United States. Salmonella antimicrobial resistance may result in bacteremia and poor outcomes. We describe antimicrobial resistance among nontyphoidal Salmonella blood isolates, using data from the National Antimicrobial Resistance Monitoring System.

METHODS

Human nontyphoidal Salmonella isolates from 2003 to 2013 were classified as fully susceptible, resistant to ≥1 antimicrobial agent, or resistant to a first-line agent. Logistic regression was used to compare resistance patterns, serotypes, and patient characteristics for Salmonella isolated from blood versus stool and to determine resistance trends over time.

RESULTS

Approximately 20% of blood isolates had antimicrobial resistance to a first-line treatment agent. Bacteremia was associated with male sex, age ≥65 years, and specific serotypes. Blood isolates were more likely to be resistant to ≥1 agent for serotypes Enteritidis, Javiana, Panama, and Typhimurium. Blood isolates were most commonly resistant to tetracycline (19%), and more likely resistant to a first-line agent (odds ratio, 1.81; 95% confidence interval, 1.56-2.11) than stool isolates. Ceftriaxone resistance increased in blood isolates from 2003 to 2013 (odd ratio, 1.12; 95% confidence interval, 1.02-1.22).

CONCLUSIONS

Resistance to first-line treatment agents in patients with Salmonella bacteremia is a concern for public health and for informing clinical decisions. Judicious antimicrobial use is crucial to limit resistance.

Pleural empyema due to Salmonella enterica serovar Enteritidis in an immunocompetent elderly patient: a case report

INTRODUCTION

Pleural empyema as a focal infection due to Salmonella enterica serovar Enteritidis is rare and most commonly described among immunosuppressed patients or patients who suffer from sickle cell anaemia and lung malignancies.

CASE PRESENTATION

Here, we present an 81-year-old immunocompetent Greek woman with bacteraemia and pleural empyema due to Salmonella Enteritidis without any gastrointestinal symptoms.

CONCLUSION

In our case, we suggest that patient's pleural effusion secondary to heart failure was complicated by empyema and that focal intravascular infection was the cause of bacteraemia.

Cholera toxin-B (ctxB) antigen expressing Salmonella Typhimurium polyvalent vaccine exerts protective immune response against Vibrio cholerae infection

Live attenuated vaccines are cost effective approach for preventing a broad range of infectious diseases, and thus are of great interest. However, immune-defects can predispose the patient to infections by the vaccine candidate itself. So far, few live vaccine candidates have been designed specifically for immune compromised individuals. Recently, we reported a new Salmonella Typhimurium Z234-vaccine strain (Periaswamy et al., PLoS ONE 2012;7:e45433), which was specifically attenuated in the NADPH-oxidase deficient host. In the present study, the Z234-vaccine strain was further engineered to express heterologous antigen (Vibrio cholerae toxin antigen subunit-B, i.e. CtxB) with the intention of creating a vector for simultaneous protection against Cholera and Salmonellosis. The primary aim of this study was to ensure the expression of CtxB antigen by the recombinant vaccine strain Z234-pMS101. The antigen CtxB was expressed through Z234 as a fusion protein with N-terminal signal sequence of Salmonella outer protein (SopE), an effector protein from Salmonella under the control of SopE promoter. The CtxB-expressing plasmid construct pMS101 (pM968-pSopE-ctxB) was found to be stable both in vitro and in vivo. In an oral mouse infection model, the vaccine strain Z234-pMS101 efficiently colonized the host gut. The extent of protection was confirmed after challenging the immunized hosts with live V. cholerae. Vaccinated mice showed reduced gut colonization by V. cholerae. Further assessment of immunological parameters supported the possibility of conferring effective immune response by Z234-pMS101 vaccine strain. Overall, the Z234-pMS101 vaccine strain showed potential as a promising polyvalent vaccine candidate to protect against S. Typhimurium and V. cholerae infection simultaneously.

Antimicrobial use in critically ill horses

OBJECTIVE

To discuss controversies surrounding antimicrobial use in critically ill horses.

DATA SOURCES

PubMed searches from 1970-present for terms including, but not limited to: "horse," "foal," "antimicrobial," "prophylaxis," "infection," "surgery," "sepsis," and "antimicrobial resistance."

HUMAN DATA SYNTHESIS

Increasing bacterial antimicrobial resistance has changed first-line antimicrobial choices and prompted shortening of the duration of prophylactic and therapeutic treatment. The need to decrease bacterial resistance development to critically important antimicrobials has been highlighted.

VETERINARY DATA SYNTHESIS

Veterinary medicine has followed a similar trend but often without a high-level evidence. Common dilemmas include diseases in which the theoretically most effective drug is a reserved antimicrobial, the inability to differentiate infectious from noninfectious disease, the duration and necessity of prophylactic antimicrobials and use of antimicrobials in primary gastrointestinal disease. These problems are illustrated using examples of purulent infections, neonatal sepsis, colic surgery, and treatment of colitis. Although enrofloxacin, cephalosporins, and doxycycline, in contrast to gentamicin, reach therapeutic concentrations within the lungs of healthy horses, the first two should not be used as first line treatment due to their reserved status. Due to the high risk of bacterial sepsis, antimicrobial treatment remains indispensable in compromised neonatal foals but shortening the length of antimicrobial treatment might be prudent. One prospective randomized study demonstrated no difference between 3 and 5 days of perioperative antimicrobial treatment in colic surgery but shorter durations were not evaluated. High-level evidence to recommend antimicrobial treatment of adult horses with undifferentiated diarrhea does not exist.

CONCLUSIONS

Few evidence-based recommendations can be made. Commonly used antimicrobial combinations remain the mainstay for treating purulent infections. Antimicrobial treatment for compromised foals should not extend beyond recovery. Continuation of prophylactic antimicrobials >3 days is likely unnecessary after colic surgery; shorter durations might be equally effective. Antimicrobial prophylaxis in adult horses with diarrhea is unlikely to be beneficial.