Clinical Staphylococcus aureus inhibits human T-cell activity through interaction with the PD-1 receptor

IMPORTANCE

Therapies that target and aid the host immune defense to repel cancer cells or invading pathogens are rapidly emerging. Antibiotic resistance is among the largest threats to human health globally. Staphylococcus aureus (S. aureus) is the most common bacterial infection, and it poses a challenge to the healthcare system due to its significant ability to develop resistance toward current available therapies. In long-term infections, S. aureus further adapt to avoid clearance by the host immune defense. In this study, we discover a new interaction that allows S. aureus to avoid elimination by the immune system, which likely supports its persistence in the host. Moreover, we find that blocking the specific receptor (PD-1) using antibodies significantly relieves the S. aureus-imposed inhibition. Our findings suggest that therapeutically targeting PD-1 is a possible future strategy for treating certain antibiotic-resistant staphylococcal infections.

Fibrinolytic and antibiotic treatment of prosthetic vascular graft infections in a novel rat model

OBJECTIVES

We developed a rat model of prosthetic vascular graft infection to assess, whether the fibrinolytic tissue plasminogen activator (tPA) could increase the efficacy of antibiotic therapy.

MATERIALS AND METHODS

Rats were implanted a polyethylene graft in the common carotid artery, pre-inoculated with approx. 6 log10 colony forming units (CFU) of methicillin resistant Staphylococcus aureus. Ten days after surgery, rats were randomized to either: 0.9% NaCl (n = 8), vancomycin (n = 8), vancomycin + tPA (n = 8), vancomycin + rifampicin (n = 18) or vancomycin + rifampicin + tPA (n = 18). Treatment duration was seven days. Approximately 36 hours after the end of treatment, the rats were euthanized, and grafts and organs were harvested for CFU enumeration.

RESULTS

All animals in the control group had significantly higher CFU at the time of euthanization compared to bacterial load found on the grafts prior to inoculation (6.45 vs. 4.36 mean log10 CFU/mL, p = 0.0011), and both the procedure and infection were well tolerated. Vancomycin and rifampicin treatment were superior to monotherapy with vancomycin, as it lead to a marked decrease in median bacterial load on the grafts (3.50 vs. 6.56 log10 CFU/mL, p = 0.0016). The addition of tPA to vancomycin and rifampicin combination treatment did not show a further decrease in bacterial load (4.078 vs. 3.50 log10 CFU/mL, p = 0.26). The cure rate was 16% in the vancomycin + rifampicin group vs. 37.5% cure rate in the vancomycin + rifampicin + tPA group. Whilst interesting, this trend was not significant at our sample size (p = 0.24).

CONCLUSION

We developed the first functional model of an arterial prosthetic vascular graft infection in rats. Antibiotic combination therapy with vancomycin and rifampicin was superior to vancomycin monotherapy, and the addition of tPA did not significantly reduce bacterial load, nor significantly increase cure rate.

Frailty level at discharge predicts mortality in older patients with Clostridioides difficile more accurately than age or disease severity

PURPOSE

Clostridioides difficile infection (CDI) has a high mortality among older patients. Identification of older patients with CDI in increased mortality risk is important to target treatment and thereby reduce mortality. The aim of this study was to investigate mortality rates and compare frailty levels at discharge, measured by the record-based Multidimensional Prognostic Index (MPI), with age and severity of CDI as mortality predictors in patients with CDI diagnosed during hospitalisation.

METHODS

This was a population-based cohort study from Central Denmark Region, Denmark, including all patients  ≥ 60 years with a positive CD toxin test without prior infection and diagnosed from 1 January to 31 December 2018. Frailty level, estimated from the electronic medical record, was defined as low, moderate, or severe frailty. CDI severity was graded according to international guidelines. Primary outcome was 90-day mortality.

RESULTS

We included 457 patients with median age 77 years (interquartile range 69-84) and females (49%). Overall, 90-day mortality was 28%, and this was associated with age (hazard ratio (HR): 2.71 (95% confidence interval 1.64-4.47)), CDI severity (HR 4.58 (3.04-6.88)) and frailty (HR 10.15 (4.06-25.36)). Frailty was a better predictor of 90-day mortality than both age (p < 0.001) and CDI severity (p = 0.04) with a receiver operating characteristic curve area of 77%.

CONCLUSION

The 90-day mortality among older patients with CDI in a Danish region is 28%. Frailty measured by record-based MPI at discharge outperforms age and disease severity markers in predicting mortality in older patients with CDI.

Risk of Helicobacter pylori transmission by faecal microbiota transplantation via oral capsules

OBJECTIVES

The aim was to determine if Helicobacter pylori is transmitted from donors to recipients by faecal microbiota transplantation (FMT) via oral capsules.

METHODS

In a cohort of faeces donors not primarily screened for H. pylori, consecutive stool samples were retrospectively analysed by the H. pylori stool antigen test (SAT). Subsequently, we analysed recipient stool samples collected before and after receiving faeces donated by H. pylori SAT-positive donors, and we recorded recipient use of antibiotics and proton pump inhibitors. All stool samples were frozen upon collection and stored at -80°C until use.

RESULTS

Thirteen out of 40 faeces donors (33%; 95% CI, 20-48%) were H. pylori SAT-positive. Among those positive, five donors donated faeces for 28 capsule-based FMTs performed in 26 recipients with stool samples collected before and after FMT. At a median of 59 days (range, 7-84 days) after FMT, no recipients (0%; 95% CI, 0-11%) were H. pylori SAT-positive.

DISCUSSION

We found no occurrence of H. pylori transmission from healthy, asymptomatic donors to recipients by oral capsule-based FMT, although with a wide CI.

Cohort description: The Danish Blood Donor Staphylococcus aureus Carriage Study

Purpose

Staphylococcus aureus carriage poses an increased risk of S. aureus infection. The aim of this study was to investigate the colonization of S. aureus among healthy individuals and to establish a prospective cohort and biobank for research in the health consequences of colonization.

Population and methods

The Danish Blood Donor S. aureus Carriage Study (DBDSaCS) was established in 2014. So far, a total of 6082 healthy participants have been included with nasal swabs and repeated swabs are performed at subsequent donations. Samples from the first 2217 participants were cultured using a two-step method to evaluate the effect of using enrichment broth. Furthermore, 262 participants were sampled from both the nares and the throat. All participants completed a questionnaire with self-reported health, anthropometric measurements, current smoking status, and physical activity. Plasma samples, nasal swab transport media, and S. aureus isolates were stored.

Results

The prevalence of S. aureus nasal colonization was 41%. The prevalence of colonization was higher in men (46%) than women (34%), lower for smokers, and decreased with increasing age (<25 years: 44% vs >55 years: 35%). In participants swabbed from the nose and throat, the prevalence of S. aureus colonization after enrichment was 55% with significantly higher prevalence in the throat (45%) than in the nose (40%). The use of an enrichment broth increased the proportion of S. aureus colonization.

Conclusion

We describe a large and growing cohort of healthy individuals established to investigate predictors for S. aureus carriage and the health consequences of carriage. Multiple projects using data from DBDSaCS linked with Danish health registers, biomarkers, and genetic markers are ongoing. Results will be published in the coming years.

Oral iron supplementation is not associated with short-term risk of infections: results from the Danish Blood Donor Study

BACKGROUND

Blood donors are at increased risk of developing iron deficiency, and several studies have recommended iron supplementation for this group. The aim of this study was to investigate the effect of oral iron supplementation on risk of infections among healthy blood donors.

STUDY DESIGN AND METHODS

We included 82,062 participants from the Danish Blood Donor Study who completed a questionnaire on health-related items including use of oral iron supplementation. Infection outcomes were ascertained by using ICD-10 codes in the Danish National Patient Register and Anatomical Therapeutic Chemical codes in the Danish Prescription Register. Multivariable Cox proportional hazards analysis was used as the statistical model. Risk estimates are presented as crude hazard ratios (HRs) with 95% confidence intervals (CIs).

RESULTS

During 19,978 person-years of observation, 6983 donors redeemed at least one prescription of antimicrobials. Similarly, during 19,829 person-years of observation, 242 donors were treated for infection at a hospital. Use of oral iron supplementation was not associated with redeemed prescriptions of antimicrobials in any strata: premenopausal women-HR 1.00, 95% CI 0.91-1.10; postmenopausal women-HR 1.07, 95% CI 0.87-1.32; and men-HR 1.01, 95% CI 0.84-1.21. In addition, use of oral iron supplementation was not associated with risk of hospital-based treatment for infection.

CONCLUSION

In a large cohort of blood donors, use of oral iron supplementation was not associated with subsequent short-term risk of infection. These findings are important to help understanding the safety of using oral iron supplementation among blood donors and the general population.

[Genital actinomycosis and pelvic abscesses in a woman with a 13-year-old intrauterine device]

A 55-year-old woman who had had the same intrauterine device (IUD) for 13 years was referred to the gynaecology outpatient clinic due to constitutional symptoms, abdominal pain and vaginal discharge. Diagnostic imaging showed multiple pelvic abscesses, and severe chronic endometritis with Actinomyces was found in an endometrial biopsy. The patient underwent surgical drainage of the accessible abscesses and started long-term antibiotic treatment. This case report illustrates that actinomycosis is an important differential diagnosis in symptomatic women with IUD and suspected gynaecologic malignancy.

Low-Grade Inflammation Is Associated with Susceptibility to Infection in Healthy Men: Results from the Danish Blood Donor Study (DBDS)

INTRODUCTION

The aim of this study was to examine whether low-grade inflammation (LGI) is associated with a subsequently increased risk of infection.

METHODS

We included 15,754 healthy participants from the Danish Blood Donor Study, who completed a questionnaire on health-related items. LGI was defined as a C-reactive protein level between 3 and 10 mg/L. Infections were identified by ICD-10 codes in the Danish National Patient Register and ATC-codes in the Danish Prescription Register. Multivariable Cox proportional hazard analysis was used as the statistical model.

RESULTS

During 53,302 person-years of observation, 571 participants were hospitalized for infection. Similarly, during 26,125 person-years of observation, 7,276 participants filled a prescription of antimicrobials. LGI was associated with increased risk of hospital-based treatment for infection only among men (hazard ratio = 1.60, 95% confidence interval (CI): 1.10-2.34) and specifically infections were abscesses and infections of the skin and subcutaneous tissue. Similarly, LGI was associated with the overall use of antimicrobials among men, and particularly with phenoxymethylpenicillin and broad-spectrum antimicrobials for treatment of urinary tract infections. The difference between men and women was not statistically significant.

CONCLUSIONS

In a large cohort of healthy individuals, LGI was associated with an increased risk of infection among healthy male blood donors.

Treatment of Clostridium difficile infection in mice with vancomycin alone is as effective as treatment with vancomycin and metronidazole in combination

Objective

Clostridium difficile is a major cause of nosocomial infectious diarrhoea. Treatment of C. difficile infection (CDI) depends on disease severity. A combination of vancomycin and metronidazole is often recommended in severe cases. The aim of this study was to examine, in a murine model of CDI, if mice treated with a combination of vancomycin and metronidazole had a better clinical outcome than mice treated with vancomycin or metronidazole alone.

Design

C57BL/6J mice pretreated with an antimicrobial mixture were challenged with C. difficile VPI 10463 or phosphate-buffered saline by oral gavage. After the challenge, the mice were treated with placebo, vancomycin, metronidazole or a combination of vancomycin and metronidazole for 10 days. The mice were monitored for 20 days with weight and a clinical score. Stool samples were examined for C. difficile spore load and presence of C. difficile toxins.

Results

None of the mice in the vancomycin-treated group died during the treatment phase compared to a mortality of 17%, 33% and 55% in the combination, metronidazole and infected control group, respectively. Mice treated with vancomycin alone or in combination with metronidazole recovered from CDI faster than mice treated with metronidazole alone. However, after discontinuation of treatment, vancomycin-treated and combination-treated mice succumbed to clinical and bacteriological relapse.

Conclusions

Mice treated with vancomycin alone had a better clinical outcome in the treatment phase of CDI than mice treated with metronidazole alone. A combination of vancomycin and metronidazole did not improve the clinical outcome when compared to treatment with vancomycin alone.

Trial registration number

The trial registration number from the Danish Experimental Animal Inspectorate is J number 2012-15-2934-00422.

Antimicrobial susceptibility testing of Clostridium difficile using EUCAST epidemiological cut-off values and disk diffusion correlates

With the emergence of reduced susceptibility of Clostridium difficile to metronidazole and vancomycin the value of antimicrobial susceptibility testing has increased. The aim of our study was to evaluate disk diffusion for susceptibility testing of C. difficile by comparing disk diffusion results with MICs from gradient tests and to propose zone diameter breakpoint correlates for the EUCAST epidemiological cut-off values (ECOFFs) recently published. We tested 211 clinical isolates of C. difficile, from patients with diarrhoea hospitalized at Aarhus and Odense University Hospitals, Denmark. Furthermore, ten clinical isolates of C. difficile from the Anaerobe Reference Laboratory, University Hospital of Wales, with known reduced susceptibility to either metronidazole or vancomycin, were included. Isolates were tested with Etest gradient strips and disk diffusion towards metronidazole, vancomycin and moxifloxacin on Brucella Blood Agar supplemented with hemin and vitamin K. We found an excellent agreement between inhibition zone diameter and MICs. For each MIC value, the inhibition zones varied from 0 to 8 mm, with 93% of values within 6 mm for metronidazole, 95% of values within 4 mm for vancomycin, and 98% of values within 4 mm for moxifloxacin. With proposed zone diameter breakpoints for metronidazole, vancomycin and moxifloxacin of WT ≥ 23 mm, WT ≥ 19 and WT ≥ 20 mm, respectively, we found no very major errors and only major errors below 2%. In conclusion, we suggest that disk diffusion is an option for antimicrobial susceptibility testing of C. difficile.