Comparison of morbidity and mortality after bloodstream infection with vancomycin-resistant versus -susceptible Enterococcus faecium: a nationwide cohort study in Denmark, 2010-2019

The emergence of bloodstream infections (BSI) caused by vancomycin-resistant Enterococci (VRE) has caused concern. Nonetheless, it remains unclear whether these types are associated with an excess risk of severe outcomes when compared with infections caused by vancomycin-susceptible Enterococci (VSE). This cohort study included hospitalized patients in Denmark with Enterococcus faecium-positive blood cultures collected between 2010 and 2019 identified in the Danish Microbiology Database. We estimated 30-day hazard ratio (HR) of death or discharge among VRE compared to VSE patients adjusted for age, sex, and comorbidity. The cohort included 6071 patients with E. faecium BSI (335 VRE, 5736 VSE) among whom VRE increased (2010-13, 2.6%; 2014-16, 6.3%; 2017-19; 9.4%). Mortality (HR 1.08, 95%CI 0.90-1.29; 126 VRE, 37.6%; 2223 VSE, 37.0%) or discharge (HR 0.89, 95%CI 0.75-1.06; 126 VRE, 37.6%; 2386 VSE, 41.6%) was not different between VRE and VSE except in 2014 (HR 1.87, 95% CI 1.18-2.96). There was no interaction between time from admission to BSI (1-2, 3-14, and >14 days) and HR of death (P = 0.14) or discharge (P = 0.45) after VRE compared to VSE, despite longer time for VRE patients (17 vs. 10 days for VSE, P < 0.0001). In conclusion, VRE BSI was not associated with excess morbidity and mortality. The excess mortality in 2014 only may be attributed to improved diagnostic- and patient-management practices after 2014, reducing time to appropriate antibiotic therapy. The high level of mortality after E. faecium BSI warrants further study.

Surgery in patients with infective endocarditis and prognostic importance of patient frailty

PURPOSE

Surgery is required in 20-50% of patients with infective endocarditis (IE). Frailty increases surgical risk; however, the prognostic implications of frailty in patients undergoing IE-related surgery remain poorly understood. We aimed to assess the association between frailty and all-cause mortality or rehospitalization after discharge (≥ 14 days).

METHODS

We identified all IE patients who underwent surgery during admission (2010-2020) in Denmark. The Hospital Frailty Risk Score was used to categorize patients into two frailty risk groups, patients with low frailty scores (< 5 points) and frail patients (≥ 5 points). We analyzed time hospitalized after discharge and all-cause mortality from the date of surgery with a one-year follow-up. Statistical analyses utilized the Kaplan-Meier estimator, Aalen-Johansen estimator, and the Cox regression model.

RESULTS

We identified 1282 patients who underwent surgery during admission, of whom 967 (75.4%) had low frailty scores, and 315 (24.6%) were frail. Frail patients were characterized by advanced age, a lower proportion of males, and a higher burden of comorbidities. Frail patients were more hospitalized (> 14 days) in the first post-discharge year (19.1% vs.12.3%) compared to patients with low frailty scores. Additionally, frail patients had higher rates of all-cause mortality including in-hospital deaths (27% vs. 15%) and rehospitalizations (43.5% vs 26.1%) compared to patients with low frailty scores. This was also evident in the adjusted analysis (hazard ratio 1.36 [CI 95% 1.09-1.71]).

CONCLUSION

Frailty was associated with an ≈40% increased rate of rehospitalization (≥ 14 days) or death. Further studies are needed to assess the effectiveness of surgery with a focus on frailty to improve prognostic outcomes in these patients.

Sex differences in infective endocarditis: a Danish nationwide study

PURPOSE

Sex differences in infective endocarditis (IE) are reported, but patient characteristics are sparse and conflicting findings on the association between sex and short-term outcomes demand further research. We aimed to characterize sex differences in IE in terms of patient characteristics, frailty, microbiology, socioeconomic status, management and outcome on a nationwide scale.

METHODS

Between 2010 and 2020, we used Danish national registries to characterize patients with IE according to sex using ICD codes and microbiological lab reports. Frailty was assessed with the Hospital Frailty Risk Score. Mortality was reported with Kaplan-Meier estimates. Logistic regression and Cox regression were used for adjusted analyses.

RESULTS

We included 6259 patients with IE with 2047 (32.7%) female patients and 4212 (67.3%) male patients. Female patients were older (median age 75.0 years (64.3-82.2) vs. 71.7 (61.7-78.9)) and more frail (Intermediate frailty: 36.5% vs. 33.1%, High frailty: 11.4% vs. 9.2%). Staphylococcus aureus-IE were most common in both sexes (34.6% vs. 28.8%), but fewer female patients had Enterococcus-IE (10.5% vs. 18.1%). Female patients were less surgically treated (14.0% vs. 21.2%). Female sex was associated with increased in-hospital mortality (adj. OR 1.33, 95% CI 1.16-1.52), but no statistically significant difference in associated 1- and 5-year mortality from hospital discharge were identified (adj. HR 1.09, 95% CI 0.95-1.24 and 1.02, 95% CI 0.92-1.12, respectively).

CONCLUSION

Female sex is associated with increased in-hospital mortality, but not in long-term mortality as compared with male patients. Female patients have a lower prevalence of Enterococcus-IE and rates of surgery. Further research is needed to understand these differences.

Patient Characteristics, Microbiology, and Mortality of Infective Endocarditis After Transcatheter Aortic Valve Implantation

BACKGROUND

Infective endocarditis (IE) after transcatheter aortic valve implantation (TAVI) is associated with high mortality and surgery is rarely performed. Thus, to inform on preventive measures and treatment strategies, we investigated patient characteristics and microbiology of IE after TAVI.

METHODS

Using Danish nationwide registries, we identified patients with IE after TAVI, IE after non-TAVI prosthetic valve (nTPV), and native valve IE. Patient characteristics; overall, early (≤12 m), and late IE (>12 m) microbiology; and unadjusted and adjusted mortality were compared.

RESULTS

We identified 273, 1022, and 5376 cases of IE after TAVI, IE after nTPV, and native valve IE. Age and frailty were highest among TAVI IE (4.8%; median age: 82 y; 61.9% frail). Enterococcus spp. were common for IE after TAVI (27.1%) and IE after nTPV (21.2%) compared with native valve IE (11.4%). Blood culture-negative IE was rare in IE after TAVI (5.5%) compared with IE after nTPV (15.2%) and native valve IE (13.5%). The unadjusted 90-day mortality was comparable, but the 5-year mortality was highest for IE after TAVI (75.2% vs 57.2% vs 53.6%). In Cox models adjusted for patient characteristics and bacterial etiology for 1-90 days and 91-365 days, there was no significant difference in mortality rates.

CONCLUSIONS

Patients with IE after TAVI are older and frailer, enterococci and streptococci are often the etiologic agents, and are rarely blood culture negative compared with other IE patients. Future studies regarding antibiotic prophylaxis strategies covering enterococci should be considered in this setting.

Recurrence of bacteremia and infective endocarditis according to bacterial species of index endocarditis episode

PURPOSE

In patients surviving infective endocarditis (IE) recurrence of bacteremia or IE is feared. However, knowledge is sparse on the incidence and risk factors for the recurrence of bacteremia or IE.

METHODS

Using Danish nationwide registries (2010-2020), we identified patients with first-time IE which were categorized by bacterial species (Staphylococcus aureus, Enterococcus spp., Streptococcus spp., coagulase-negative staphylococci [CoNS], 'Other' microbiological etiology). Recurrence of bacteremia (including IE episodes) or IE with the same bacterial species was estimated at 12 months and 5 years, considering death as a competing risk. Cox regression models were used to compute adjusted hazard ratios of the recurrence of bacteremia or IE.

RESULTS

We identified 4086 patients with IE; 1374 (33.6%) with S. aureus, 813 (19.9%) with Enterococcus spp., 1366 (33.4%) with Streptococcus spp., 284 (7.0%) with CoNS, and 249 (6.1%) with 'Other'. The overall 12-month incidence of recurrent bacteremia with the same bacterial species was 4.8% and 2.6% with an accompanying IE diagnosis, while this was 7.7% and 4.0%, respectively, with 5 years of follow-up. S. aureus, Enterococcus spp., CoNS, chronic renal failure, and liver disease were associated with an increased rate of recurrent bacteremia or IE with the same bacterial species.

CONCLUSION

Recurrent bacteremia with the same bacterial species within 12 months, occurred in almost 5% and 2.6% for recurrent IE. S. aureus, Enterococcus spp., and CoNS were associated with recurrent infections with the same bacterial species.

Hemodialysis and its impact on patient characteristics, microbiology, cardiac surgery, and mortality in infective endocarditis

BACKGROUND

Patients with chronic renal failure on hemodialysis carry a significant risk of infective endocarditis (IE), but data on whether these patients differ from other patients with IE in terms of comorbidity, microbiology, rates of surgery and mortality are sparse.

METHODS

Using Danish nationwide registries, all patients with IE diagnosed between February 1, 2010, and May 14, 2018 were identified and categorized into a "hemodialysis group" and a "non-hemodialysis group." Patient groups were compared by comorbidities, microbiological etiology, cardiac surgery, and mortality. Risk factors associated with mortality were assessed in multivariable Cox regression analysis.

RESULTS

In total, 4,366 patients with IE were included with 226 (5.2%) patients in the hemodialysis group. Patients in the hemodialysis group were younger (66.0 years [IQR 53.8-74.9] vs 72.2 years [IQR 62.2-80.0]), had more comorbidities and were surgically treated less often (10.6% vs 20.8%), compared with patients from the nonhemodialysis group. Staphylococcus aureus was more than twice as prevalent (58.0% vs 26.5%). No difference in in-hospital mortality was found between the 2 groups (20.8% vs 18.5%), but 1- and 5-year mortality were significantly higher in the hemodialysis group than in the nonhemodialysis group (37.7% vs 17.7% and 72.1% vs 42.5%, respectively). In adjusted analysis, hemodialysis was associated with higher 1-year (HR = 2.71, 95% CI 2.07-3.55) and 5-year mortality (HR = 2.72, 95% CI 2.22-3.34) CONCLUSIONS: Patients with IE on chronic hemodialysis were younger, had more comorbidity, a higher prevalence of Staphylococcus aureus IE, and a higher mortality than patients without hemodialysis.

Microbiological Etiology in Patients with IE Undergoing Surgery and for Patients with Medical Treatment Only: A Nationwide Study from 2010 to 2020

Microbiological etiology has been associated with surgery for infective endocarditis (IE) during admission, especially Staphylococcus aureus. We aimed to compare patient characteristics, microbiological characteristics, and outcomes by treatment choice (surgery or not). We identified patients with first-time IE between 2010 and 2020 and examined the microbiological etiology of IE according to treatment choice. To identify factors associated with surgery during initial admission, we used the Aalen-Johansen estimator and an adjusted cause-specific Cox model. One-year mortality stratified by microbiological etiology and treatment choice was assessed using unadjusted Kaplan-Meier estimates and an adjusted Cox proportional hazard model. A total of 6255 patients were included, of which 1276 (20.4%) underwent surgery during admission. Patients who underwent surgery were younger (65 vs. 74 years) and less frequently had cerebrovascular disease, cardiovascular disease, diabetes, and chronic kidney disease. Patients with Staphylococcus aureus IE were less likely to undergo surgery during admission (13.6%) compared to all other microbiological etiologies. One-year mortality according to microbiological etiology in patients who underwent surgery was 7.0%, 5.3%, 5.5%, 9.6%, 13.2, and 11.2% compared with 24.2%, 19.1%, 27,6%, 25.2%, 21%, and 16.9% in patients who received medical therapy for Staphylococcus aureus, Streptococcus spp., Enterococcus spp., coagulase-negative Staphylococci, "other microbiological etiologies", and blood culture-negative infective endocarditis, respectively. Patients with IE who underwent surgery differed in terms of microbiology, more often having Streptococci than those who received medical therapy. Contrary to expectations, Staphylococcus aureus was more common among patients who received medical therapy only.

Increase in invasive group A streptococcal infections and emergence of novel, rapidly expanding sub-lineage of the virulent Streptococcus pyogenes M1 clone, Denmark, 2023

A highly virulent sub-lineage of the Streptococcus pyogenes M1 clone has been rapidly expanding throughout Denmark since late 2022 and now accounts for 30% of the new invasive group A streptococcal infections. We aimed to investigate whether a shift in variant composition can account for the high incidence rates observed over winter 2022/23, or if these are better explained by the impact of COVID-19-related restrictions on population immunity and carriage of group A Streptococcus.

Correlation of High Seawater Temperature with Vibrio and Shewanella Infections, Denmark, 2010-2018

During 2010-2018 in Denmark, 638 patients had Vibrio infections diagnosed and 521 patients had Shewanella infections diagnosed. Most cases occurred in years with high seawater temperatures. The substantial increase in those infections, with some causing septicemia, calls for clinical awareness and mandatory notification policies.

The perinatal health challenges of emerging and re-emerging infectious diseases: A narrative review

The world has seen numerous infectious disease outbreaks in the past decade. In many cases these outbreaks have had considerable perinatal health consequences including increased risk of preterm delivery (e.g., influenza, measles, and COVID-19), and the delivery of low birth weight or small for gestational age babies (e.g., influenza, COVID-19). Furthermore, severe perinatal outcomes including perinatal and infant death are a known consequence of multiple infectious diseases (e.g., Ebola virus disease, Zika virus disease, pertussis, and measles). In addition to vaccination during pregnancy (where possible), pregnant women, are provided some level of protection from the adverse effects of infection through community-level application of evidence-based transmission-control methods. This review demonstrates that it takes almost 2 years for the perinatal impacts of an infectious disease outbreak to be reported. However, many infectious disease outbreaks between 2010 and 2020 have no associated pregnancy data reported in the scientific literature, or pregnancy data is reported in the form of case-studies only. This lack of systematic data collection and reporting has a negative impact on our understanding of these diseases and the implications they may have for pregnant women and their unborn infants. Monitoring perinatal health is an essential aspect of national and global healthcare strategies as perinatal life has a critical impact on early life mortality as well as possible effects on later life health. The unpredictable nature of emerging infections and the potential for adverse perinatal outcomes necessitate that we thoroughly assess pregnancy and perinatal health implications of disease outbreaks and their public health interventions in tandem with outbreak response efforts. Disease surveillance programs should incorporate perinatal health monitoring and health systems around the world should endeavor to continuously collect perinatal health data in order to quickly update pregnancy care protocols as needed.

Prevalence and Mortality of Infective Endocarditis in Community-Acquired and Healthcare-Associated Staphylococcus aureus Bacteremia: A Danish Nationwide Registry-Based Cohort Study

BACKGROUND

Staphylococcus aureus bacteremia (SAB) can be community-acquired or healthcare-associated, and prior small studies have suggested that this mode of acquisition impacts the subsequent prevalence of infective endocarditis (IE) and patient outcomes.

METHODS

First-time SAB was identified from 2010 to 2018 using Danish nationwide registries and categorized into community-acquired (no healthcare contact within 30 days) or healthcare-associated (SAB >48 hours of hospital admission, hospitalization within 30 days, or outpatient hemodialysis). Prevalence of IE (defined from hospital codes) was compared between groups using multivariable adjusted logistic regression analysis. One-year mortality of S aureus IE (SAIE) was compared between groups using multivariable adjusted Cox proportional hazard analysis.

RESULTS

We identified 5549 patients with community-acquired SAB and 7491 with healthcare-associated SAB. The prevalence of IE was 12.1% for community-acquired and 6.6% for healthcare-associated SAB. Community-acquired SAB was associated with a higher odds of IE as compared with healthcare-associated SAB (odds ratio, 2.12 [95% confidence interval {CI}, 1.86-2.41]). No difference in mortality was observed with 0-40 days of follow-up for community-acquired SAIE as compared with healthcare-associated SAIE (HR, 1.07 [95% CI, .83-1.37]), while with 41-365 days of follow-up, community-acquired SAIE was associated with a lower mortality (HR, 0.71 [95% CI, .53-.95]).

CONCLUSIONS

Community-acquired SAB was associated with twice the odds for IE, as compared with healthcare-associated SAB. We identified no significant difference in short-term mortality between community-acquired and healthcare-associated SAIE. Beyond 40 days of survival, community-acquired SAIE was associated with a lower mortality.

Association between hemodialysis and patient characteristics, microbiological etiology, cardiac surgery, and mortality in patients with infective endocarditis: a nationwide study

Background

Hemodialysis and infective endocarditis are both associated with poor patient outcome. However, despite high mortality rates for each disease entity, little attention is given to patients on hemodialysis who develop infective endocarditis.

Purpose

To examine patient characteristics, microbiological etiology, cardiac surgery, and outcome among patients on hemodialysis with infective endocarditis compared with patients with infective endocarditis without hemodialysis treatment.

Methods

With Danish nationwide registries, we identified patients with infective endocarditis between 2010–2018 and linked them to microbiological data from a nationwide microbiological registry with complete blood culture data. We included patients in the hemodialysis group if they received hemodialysis treatment within 6 months prior to their first-time infective endocarditis admission. Patients not meeting this criteria were put in the non-hemodialysis group. We used Kaplan-Meier estimates for difference in mortality and Cox regression for adjusted analysis.

Results

We included 4,106 patients with infective endocarditis of which 265 (6.5%) patients were also in hemodialysis treatment (66.8% men). Patients on hemodialysis were younger (median age 66 years [IQR=54.2–74.9] vs. 72.3 years [IQR=62.3–80.4]) and had a higher burden of comorbidities including hypertension (68.7 vs. 56.9%), diabetes (47.2% vs. 18.8%), and ischemic heart disease (41.1% vs. 32.2%) compared to patients without hemodialysis treatment, all p-values &lt;0.01. Cardiac surgery was less frequently performed in patients in the hemodialysis group than in the non-hemodialysis group (11.9% vs. 19.4%, respectively, p&lt;0.001) and Staphylococcus aureus was more frequently the microbiological etiology of infective endocarditis in the hemodialysis group than in the non-hemodialysis group (57.0% vs. 25.3%, respectively, p&lt;0.0001). No statistically significant difference for in-hospital mortality was found. Figure 1 shows difference in mortality between the two groups. 1- and 5-year mortality were significantly higher in the hemodialysis group than in the non-hemodialysis group (34.3% vs. 17.2% and 50.5% vs. 33.9%, respectively, p&lt;0.00001) and in adjusted analysis hemodialysis was associated with higher 1- and 5-year mortality (hazard ratio of 2.41, 95% CI 1.85–3.13 and 2.50, 95% CI 2.05–3.05, respectively), as compared with patients in the non-hemodialysis group.

Conclusion

Patients on hemodialysis with infective endocarditis are younger, sicker and have Staphylococcus aureus as causing agent more than twice as often as patients with infective endocarditis without hemodialysis treatment. This patient group have a higher mortality and by 5 years, 75% of patients in our hemodialysis group were dead.

Funding Acknowledgement

Type of funding sources: None.

Temporal Changes, Patient Characteristics, and Mortality, According to Microbiological Cause of Infective Endocarditis: A Nationwide Study

Background

Monitoring of microbiological cause of infective endocarditis (IE) remains key in the understanding of IE; however, data from large, unselected cohorts are sparse. We aimed to examine temporal changes, patient characteristics, and in‐hospital and long‐term mortality, according to microbiological cause in patients with IE from 2010 to 2017.

Methods and Results

Linking Danish nationwide registries, we identified all patients with first‐time IE. In‐hospital and long‐term mortality rates were assessed according to microbiological cause and compared using multivariable adjusted logistic regression analysis and Cox proportional hazard analysis, respectively. A total of 4123 patients were included. Staphylococcus aureus was the most frequent cause (28.1%), followed by Streptococcus species (26.0%), Enterococcus species (15.5%), coagulase‐negative staphylococci (6.2%), and “other microbiological causes” (5.3%). Blood culture–negative IE was registered in 18.9%. The proportion of blood culture–negative IE declined during the study period, whereas no significant changes were seen for any microbiological cause. Patients with Enterococcus species were older and more often had a prosthetic heart valve compared with other causes. For Streptococcus species IE, in‐hospital and long‐term mortality (median follow‐up, 2.3 years) were 11.1% and 58.5%, respectively. Compared with Streptococcus species IE, the following causes were associated with a higher in‐hospital mortality: S aureus IE (odds ratio [OR], 3.48 [95% CI, 2.74–4.42]), Enterococcus species IE (OR, 1.48 [95% CI, 1.11–1.97]), coagulase‐negative staphylococci IE (OR, 1.79 [95% CI, 1.21–2.65]), “other microbiological cause” (OR, 1.47 [95% CI, 0.95–2.27]), and blood culture–negative IE (OR, 1.99 [95% CI, 1.52–2.61]); and the following causes were associated with higher mortality following discharge (median follow‐up, 2.9 years): S aureus IE (hazard ratio [HR], 1.39 [95% CI, 1.19–1.62]), Enterococcus species IE (HR, 1.31 [95% CI, 1.11–1.54]), coagulase‐negative staphylococci IE (HR, 1.07 [95% CI, 0.85–1.36]), “other microbiological cause” (HR, 1.45 [95% CI, 1.13–1.85]), and blood culture–negative IE (HR, 1.05 [95% CI, 0.89–1.25]).

Conclusions

This nationwide study showed that S aureus was the most frequent microbiological cause of IE, followed by Streptococcus species and Enterococcus species. Patients with S aureus IE had the highest in‐hospital mortality.

Risk of hospitalisation associated with infection with SARS-CoV-2 omicron variant versus delta variant in Denmark: an observational cohort study

BACKGROUND

Estimates of the severity of the SARS-CoV-2 omicron variant (B.1.1.529) are crucial to assess the public health impact associated with its rapid global dissemination. We estimated the risk of SARS-CoV-2-related hospitalisations after infection with omicron compared with the delta variant (B.1.617.2) in Denmark, a country with high mRNA vaccination coverage and extensive free-of-charge PCR testing capacity.

METHODS

In this observational cohort study, we included all RT-PCR-confirmed cases of SARS-CoV-2 infection in Denmark, with samples taken between Nov 21 (date of first omicron-positive sample) and Dec 19, 2021. Individuals were identified in the national COVID-19 surveillance system database, which included results of a variant-specific RT-PCR that detected omicron cases, and data on SARS-CoV-2-related hospitalisations (primary outcome of the study). We calculated the risk ratio (RR) of hospitalisation after infection with omicron compared with delta, overall and stratified by vaccination status, in a Poisson regression model with robust SEs, adjusted a priori for reinfection status, sex, age, region, comorbidities, and time period.

FINDINGS

Between Nov 21 and Dec 19, 2021, among the 188 980 individuals with SARS-CoV-2 infection, 38 669 (20·5%) had the omicron variant. SARS-CoV-2-related hospitalisations and omicron cases increased during the study period. Overall, 124 313 (65·8%) of 188 980 individuals were vaccinated, and vaccination was associated with a lower risk of hospitalisation (adjusted RR 0·24, 95% CI 0·22-0·26) compared with cases with no doses or only one dose of vaccine. Compared with delta infection, omicron infection was associated with an adjusted RR of hospitalisation of 0·64 (95% CI 0·56-0·75; 222 [0·6%] of 38 669 omicron cases admitted to hospital vs 2213 [1·5%] of 150 311 delta cases). For a similar comparison by vaccination status, the RR of hospitalisation was 0·57 (0·44-0·75) among cases with no or only one dose of vaccine, 0·71 (0·60-0·86) among those who received two doses, and 0·50 (0·32-0·76) among those who received three doses.

INTERPRETATION

We found a significantly lower risk of hospitalisation with omicron infection compared with delta infection among both vaccinated and unvaccinated individuals, suggesting an inherent reduced severity of omicron. Our results could guide modelling of the effect of the ongoing global omicron wave and thus health-care system preparedness.

FUNDING

None.

Evaluation of diagnostic test procedures for SARS-CoV-2 using latent class models

Polymerase chain reaction (PCR) and antigen tests have been used extensively for screening during the severe acute respiratory syndrome coronavirus 2 pandemics. However, the real‐world sensitivity and specificity of the two testing procedures in the field have not yet been estimated without assuming that the PCR constitutes a gold standard test. We use latent class models to estimate the in situ performance of both tests using data from the Danish national registries. We find that the specificity of both tests is very high (>99.7%), while the sensitivities are 95.7% (95% confidence interval [CI]: 92.8%–98.4%) and 53.8% (95% CI: 49.8%–57.9%) for the PCR and antigen tests, respectively. These findings have implications for the use of confirmatory PCR tests following a positive antigen test result: we estimate that serial testing is counterproductive at higher prevalence levels.

A Nationwide Observational Study of Chlamydia trachomatis Infections in Denmark during the COVID-19 Pandemic

The aim of this study was to determine whether COVID-19 restrictions had an impact on Chlamydia trachomatis infections compared with 2018 and 2019. A retrospective nationwide observational study was performed using monthly incidences of laboratory-confirmed chlamydia cases and number of tests, obtained from Danish national surveillance data. Testing rates and positivity rates were compared using Poisson and logistic regression. The first Danish COVID-19 lockdown (12 March to 14 April 2020) resulted in a reduction in the number of chlamydia tests performed (rate ratio 0.72, 95% confidence interval  0.71–0.73) and a consequent reduction in the number of laboratory-identified cases (66.5 vs 88.3 per 100,000 population during the same period in 2018 to 2019). This period was followed by a return of testing and test positivity close to the level seen in 2018 to 2019. The second Danish COVID-19 lockdown (17 December to 31 March 2021) resulted in crude incidence rates of laboratory-confirmed chlamydia infection that were similar to the crude incidence rates seen during same period in 2018 to 2019. In conclusion, the Danish COVID-19 restrictions have had negligible effects on laboratory-confirmed C. trachomatis transmission.

Increased transmissibility of SARS-CoV-2 lineage B.1.1.7 by age and viral load

New lineages of SARS-CoV-2 are of potential concern due to higher transmissibility, risk of severe outcomes, and/or escape from neutralizing antibodies. Lineage B.1.1.7 (the Alpha variant) became dominant in early 2021, but the association between transmissibility and risk factors, such as age of primary case and viral load remains poorly understood. Here, we used comprehensive administrative data from Denmark, comprising the full population (January 11 to February 7, 2021), to estimate household transmissibility. This study included 5,241 households with primary cases; 808 were infected with lineage B.1.1.7 and 4,433 with other lineages. Here, we report an attack rate of 38% in households with a primary case infected with B.1.1.7 and 27% in households with other lineages. Primary cases infected with B.1.1.7 had an increased transmissibility of 1.5-1.7 times that of primary cases infected with other lineages. The increased transmissibility of B.1.1.7 was multiplicative across age and viral load.

Risk of hospitalisation associated with infection with SARS-CoV-2 lineage B.1.1.7 in Denmark: an observational cohort study

BACKGROUND

The more infectious SARS-CoV-2 lineage B.1.1.7 rapidly spread in Europe after December, 2020, and a concern that B.1.1.7 could cause more severe disease has been raised. Taking advantage of Denmark's high RT-PCR testing and whole genome sequencing capacities, we used national health register data to assess the risk of COVID-19 hospitalisation in individuals infected with B.1.1.7 compared with those with other SARS-CoV-2 lineages.

METHODS

We did an observational cohort study of all SARS-CoV-2-positive cases confirmed by RT-PCR in Denmark, sampled between Jan 1 and March 24, 2021, with 14 days of follow-up for COVID-19 hospitalisation. Cases were identified in the national COVID-19 surveillance system database, which includes data from the Danish Microbiology Database (RT-PCR test results), the Danish COVID-19 Genome Consortium, the National Patient Registry, the Civil Registration System, as well as other nationwide registers. Among all cases, COVID-19 hospitalisation was defined as first admission lasting longer than 12 h within 14 days of a sample with a positive RT-PCR result. The study population and main analysis were restricted to the proportion of cases with viral genome data. We calculated the risk ratio (RR) of admission according to infection with B.1.1.7 versus other co-existing lineages with a Poisson regression model with robust SEs, adjusted a priori for sex, age, calendar time, region, and comorbidities. The contribution of each covariate to confounding of the crude RR was evaluated afterwards by a stepwise forward inclusion.

FINDINGS

Between Jan 1 and March 24, 2021, 50 958 individuals with a positive SARS-CoV-2 test and at least 14 days of follow-up for hospitalisation were identified; 30 572 (60·0%) had genome data, of whom 10 544 (34·5%) were infected with B.1.1.7. 1944 (6·4%) individuals had a COVID-19 hospitalisation and of these, 571 (29·4%) had a B.1.1.7 infection and 1373 (70·6%) had an infection with other SARS-CoV-2 lineages. Although the overall number of hospitalisations decreased during the study period, the proportion of individuals infected with B.1.1.7 increased from 3·5% to 92·1% per week. B.1.1.7 was associated with a crude RR of hospital admission of 0·79 (95% CI 0·72-0·87; p<0·0001) and an adjusted RR of 1·42 (95% CI 1·25-1·60; p<0·0001). The adjusted RR was increased in all strata of age and calendar period-the two covariates with the largest contribution to confounding of the crude RR.

INTERPRETATION

Infection with SARS-CoV-2 lineage B.1.1.7 was associated with an increased risk of hospitalisation compared with that of other lineages in an analysis adjusted for covariates. The overall effect on hospitalisations in Denmark was lessened due to a strict lockdown, but our findings could support hospital preparedness and modelling of the projected impact of the epidemic in countries with uncontrolled spread of B.1.1.7.

FUNDING

None.

COVID-19 versus influenza A/B supeRInfectionS in the IntenSive care unit (CRISIS): Protocol for a Danish nationwide cohort study

BACKGROUND

Superinfection following viral infection is a known complication, which may lead to longer hospitalisation and worse outcome. Empirical antibiotic therapy may prevent bacterial superinfections, but may also lead to overuse, adverse effects and development of resistant pathogens. Knowledge about the incidence of superinfections in intensive care unit (ICU) patients with severe Coronavirus Disease 2019 (COVID-19) is limited.

METHODS

We will conduct a nationwide cohort study comparing the incidence of superinfections in patients with severe COVID-19 admitted to the ICU compared with ICU patients with influenza A/B in Denmark. We will include approximately 1000 patients in each group from the time period of 1 October 2014 to 30 April 2019 and from 10 March 2020 to 1 March 2021 for patients with influenza and COVID-19, respectively. The primary outcome is any superinfection within 90 days of admission to the ICU. We will use logistic regression analysis comparing COVID-19 with influenza A/B after adjustment for relevant predefined confounders. Secondarily, we will use unadjusted and adjusted logistic regression analyses to assess six potential risk factors (sex, age, cancer [including haematological], immunosuppression and use of life support on day 1 in the ICU) for superinfections and compare outcomes in patients with COVID-19 with/without superinfections, and present descriptive data regarding the superinfections.

CONCLUSION

This study will provide important knowledge about superinfections in ICU patients with severe COVID-19.

Spotlight influenza: Influenza surveillance before and after the introduction of point-of-care testing in Denmark, season 2014/15 to 2018/19

Background

In Denmark, influenza surveillance is ensured by data capturing from existing population-based registers. Since 2017, point-of-care (POC) testing has been implemented outside the regional clinical microbiology departments (CMD).

Aim

We aimed to assess influenza laboratory results in view of the introduction of POC testing.

Methods

We retrospectively observed routine surveillance data on national influenza tests before and after the introduction of POC testing as available in the Danish Microbiological Database. Also, we conducted a questionnaire study among Danish CMD about influenza diagnostics.

Results

Between the seasons 2014/15 and 2018/19, 199,744 influenza tests were performed in Denmark of which 44,161 were positive (22%). After the introduction of POC testing, the overall percentage of positive influenza tests per season did not decrease. The seasonal influenza test incidence was higher in all observed age groups. The number of operating testing platforms placed outside a CMD and with an instrument analytical time ≤ 3 h increased after 2017. Regionally, the number of tests registered as POC in the Danish Microbiological Database and the number of tests performed with an instrument analytical time ≤ 3 h or outside a CMD partially differed. Where comparable (71% of tests), the relative proportion of POC tests out of all tests increased from season 2017/18 to 2018/19. In both seasons, the percentage of positive POC tests resulted slightly lower than for non-POC tests.

Conclusion

POC testing integrated seamlessly into national influenza surveillance. We propose the use of POC results in the routine surveillance of seasonal influenza.

Proton-Pump Inhibitor Use and the Risk of Community-Associated Clostridium difficile Infection

Background

Proton-pump inhibitors (PPIs) have been reported to increase the risk of community-associated Clostridium difficile infection (CDI), but the association remains disputed.

Methods

A nationwide cohort study among adults in Denmark, 2010–2013, linking register data on C. difficile testing, filled prescriptions, and patient characteristics. All incident episodes of community-associated CDI (ie, positive culture, molecular assay, or toxin test in individuals without previous hospitalization in the prior 12 weeks and without a positive test for C. difficile in the prior 8 weeks) were identified in the Danish National Microbiological Database. Self-controlled case-series analyses were used to estimate incidence rate ratios (IRRs) for community-associated CDI, comparing periods with and without exposure to PPIs. By design, models took fixed confounders such as chronic disease, genetics, and socioeconomic status into account; further, time-varying confounders, including hospital stay and antibiotic and corticosteroid use were adjusted for.

Results

3583 episodes of community-associated CDI were identified, of which 964 occurred during current use of PPIs, 324 occurred 0–6 months after treatment cessation, 123 occurred 6–12 months after treatment cessation, and 2172 occurred during time periods without use of PPIs. The adjusted IRR was 2.03 (95% confidence interval, 1.74–2.36), comparing use of PPI with nonuse. The increased risk remained elevated in later time periods: 1.54 (1.31–1.80) for 0–6 months, 1.24 (1.00–1.53) for 6–12 months after current use.

Conclusions

Use of PPIs was associated with moderately increased risk of community-associated CDI. The risk remained elevated up to 1 year after PPI treatment had ended.

Electronic reporting of diagnostic laboratory test results from all healthcare sectors is a cornerstone of national preparedness and control of COVID-19 in Denmark

The COVID‐19 pandemic has led to an unprecedented demand for real‐time surveillance data in order to inform critical decision makers regarding the management of the pandemic. The aim of this review was to describe how the Danish national microbiology database, MiBa, served as a cornerstone for providing data to the real‐time surveillance system by linkage to other nationwide health registries. The surveillance system was established on an existing IT health infrastructure and a close network between clinical microbiologists, information technology experts, and public health officials. In 2020, testing capacity for SARS‐CoV‐2 was ramped up from none to over 10,000 weekly PCR tests per 100,000 population. The crude incidence data mirrored this increase in testing. Real‐time access to denominator data and patient registries enabled adjustments for fluctuations testing activity, providing robust data on crude SARS‐CoV‐2 incidence during the changing diagnostic and management strategies. The use of the same data for different purposes, for example, final laboratory reports, information to the public, contact tracing, public health, and science, has been a critical asset for the pandemic response. It has also raised issues concerning data protection and critical capacity of the underlying technical systems and key resources. However, even with these limitations, the setup has enabled decision makers to adopt timely interventions. The experiences from COVID‐19 may motivate a transformation from traditional indicator‐based public health surveillance to an all‐encompassing information system based on access to a comprehensive set of data sources, including diagnostic and reference microbiology.

SARS-CoV-2 infection and adverse outcomes in users of ACE inhibitors and angiotensin-receptor blockers: a nationwide case-control and cohort analysis

OBJECTIVE

To examine the impact of ACE inhibitor (ACE-I)/angiotensin receptor blocker (ARB) use on rate of SARS-CoV-2 infection and adverse outcomes.

METHODS

This nationwide case-control and cohort study included all individuals in Denmark tested for SARS-CoV-2 RNA with PCR from 27 February 2020 to 26 July 2020. We estimated confounder-adjusted ORs for a positive test among all SARS-CoV-2 tested, and inverse probability of treatment weighted 30-day risk and risk ratios (RRs) of hospitalisation, intensive care unit (ICU) admission and mortality comparing current ACE-I/ARB use with calcium channel blocker (CCB) use and with non-use.

RESULTS

The study included 13 501 SARS-CoV-2 PCR-positive and 1 088 695 PCR-negative individuals. Users of ACE-I/ARB had a marginally increased rate of a positive PCR when compared with CCB users (aOR 1.17, 95% CI 1.00 to 1.37), but not when compared with non-users (aOR 1.00 95% CI 0.92 to 1.09).Among PCR-positive individuals, 1466 (11%) were ACE-I/ARB users. The weighted risk of hospitalisation was 36.5% in ACE-I/ARB users and 43.3% in CCB users (RR 0.84, 95% CI 0.70 to 1.02). The risk of ICU admission was 6.3% in ACE-I/ARB users and 5.4% in CCB users (RR 1.17, 95% CI 0.64 to 2.16), while the 30-day mortality was 12.3% in ACE-I/ARB users and 13.9% in CCB users (RR 0.89, 95% CI 0.61 to 1.30). The associations were similar when ACE-I/ARB users were compared with non-users.

CONCLUSIONS

ACE-I/ARB use was associated neither with a consistently increased rate nor with adverse outcomes of SARS-CoV-2 infection. Our findings support the current recommendation of continuing use of ACE-Is/ARBs during the SARS-CoV-2 pandemic.

TRIAL REGISTRATION NUMBER

EUPAS34887.

Temporal changes in the incidence of infective endocarditis in Denmark 1997-2017: A nationwide study

BACKGROUND

Infective endocarditis (IE) remains a life-threatening disease, yet substantial variation in reported incidences of the disease exist. We aimed to conduct a contemporary, nationwide study of the temporal changes in incidence of IE.

METHODS

We included all Danish cases of first-time IE (1997-2017) using nationwide registries. Patients were grouped into three seven-year intervals (1997-2003, 2004-2010, 2011-2017). Crude annual incidence rates (IR) per 100,000 person-years (PY) were examined overall and per subgroups: age, sex, patients without prior prosthetic heart valve or a cardiac implantable electronic device (CIED). Incidence rate ratios (IRR) were calculated adjusting for age-group, sex and diabetes.

RESULTS

We identified 8675 patients with IE. Over time, patients were older at diagnosis with a median age of 66.2 years (interquartile range, IQR: 51.5-76.5) and 72.2 years (IQR 62.2-79.9) in 1997-2003 and 2011-2017, respectively. The overall IR increased from 5.0/100,000 PY (95% CI: 4.4-5.6) to 10.5/100,000 PY (95% CI: 9.6-11.3) from 1997 to 2017. IR for patients without prior prosthetic heart valve or a CIED increased from 4.9/100,000 PY (95% CI: 4.3-5.5) to 6.4/100,000 PY (95% CI: 5.8-7.1) (P ≤ 0.0001 for interaction). The IR in males increased from 5.6/100,000 PY (95% CI: 4.7-6.5) to 14.2/100,000 PY (95% CI: 12.9-15.6). The IR in females increased from 4.3/100,000 PY (95% CI: 3.6-5.2) to 6.7/100,000 PY (95% CI: 5.8-7.7). IRR (adjusted for age-groups, sex and diabetes) increased over time (IRR = 1.60 (1.39-1.85) in 2017 vs 1997).

CONCLUSION

The incidence of IE more than doubled during the study period. The increase was mainly seen among men and elderly patients only partly explained by the increase in patients with prior heart valve prosthesis or a CIED.

Prevalence of infective endocarditis in patients with positive blood cultures: a Danish nationwide study

AIMS

Increasing attention has been given to the risk of infective endocarditis (IE) in patients with certain blood stream infections (BSIs). Previous studies have been conducted on selected patient cohorts, yet unselected data are sparse. We aimed to investigate the prevalence of IE in BSIs with bacteria typically associated with IE.

METHODS AND RESULTS

By crosslinking nationwide registries from 2010 to 2017, we identified patients with BSIs typically associated with IE: Enterococcus faecalis (E. faecalis), Staphylococcus aureus (S. aureus), Streptococcus spp., and coagulase negative staphylococci (CoNS) and examined the concurrent IE prevalence. A trend test was used to examine temporal changes in the prevalence of IE. In total 69 021, distributed with 15 350, 16 726, 19 251, and 17 694 BSIs were identified in the periods of 2010-2011, 2012-2013, 2014-2015, and 2016-2017, respectively. Patients with E. faecalis had the highest prevalence of IE (16.7%) followed by S. aureus (10.1%), Streptococcus spp. (7.3%), and CoNS (1.6%). Throughout the study period, the prevalence of IE among patients with E. faecalis and Streptococcus spp. increased significantly (P = 0.0005 and P = 0.03, respectively). Male patients had a higher prevalence of IE for E. faecalis, Streptococcus spp., and CoNS compared with females. A significant increase in the prevalence of IE was seen for E. faecalis, Streptococcus spp., and CoNS with increasing age.

CONCLUSION

For E. faecalis BSI, 1 in 6 had IE, for S. aureus BSI 1 in 10 had IE, and for Streptococcus spp. 1 in 14 had IE. Our results suggest that screening for IE seems reasonable in patients with E. faecalis BSI, S. aureus BSI, or Streptococcus spp. BSI.

Characteristics and predictors of hospitalization and death in the first 11 122 cases with a positive RT-PCR test for SARS-CoV-2 in Denmark: a nationwide cohort

BACKGROUND

Population-level knowledge on individuals at high risk of severe and fatal coronavirus disease 2019 (COVID-19) is urgently needed to inform targeted protection strategies in the general population.

METHODS

We examined characteristics and predictors of hospitalization and death in a nationwide cohort of all Danish individuals tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from 27 February 2020 until 19 May 2020.

RESULTS

We identified 11 122 SARS-CoV-2 polymerase chain reaction-positive cases of whom 80% were community-managed and 20% were hospitalized. Thirty-day all-cause mortality was 5.2%. Age was strongly associated with fatal disease {odds ratio [OR] 15 [95% confidence interval (CI): 9-26] for 70-79 years, increasing to OR 90 (95% CI: 50-162) for ≥90 years, when compared with cases aged 50-59 years and adjusted for sex and number of co-morbidities}. Similarly, the number of co-morbidities was associated with fatal disease [OR 5.2 (95% CI: 3.4-8.0), for cases with at least four co-morbidities vs no co-morbidities] and 79% of fatal cases had at least two co-morbidities. Most major chronic diseases were associated with hospitalization, with ORs ranging from 1.3-1.4 (e.g. stroke, ischaemic heart disease) to 2.6-3.4 (e.g. heart failure, hospital-diagnosed kidney disease, organ transplantation) and with mortality with ORs ranging from 1.1-1.3 (e.g. ischaemic heart disease, hypertension) to 2.5-3.2 (e.g. major psychiatric disorder, organ transplantation). In the absence of co-morbidities, mortality was <5% in persons aged ≤80 years.

CONCLUSIONS

In this nationwide population-based COVID-19 study, increasing age and multimorbidity were strongly associated with hospitalization and death. In the absence of co-morbidities, the mortality was, however, <5% until the age of 80 years.

Existing Data Sources in Clinical Epidemiology: The Danish COVID-19 Cohort

Background

To facilitate research on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a prospective cohort of all Danish residents tested for SARS-CoV-2 in Denmark is established.

Data Structure

All Danish residents tested by reverse transcriptase polymerase chain reactions (RT-PCR) for SARS-CoV-2 in Denmark are included. The cohort is identified using the Danish Microbiology Database. Individual-level record linkage between administrative and health-care registries is facilitated by the Danish Civil Registration System. Information on outcomes related to SARS-CoV-2 infection includes hospital admission, intensive care unit admission, mechanical ventilation, and death and is retrieved from the five administrative Danish regions, the Danish National Patient Registry, and the Danish Register of Causes of Death. The Patient Registry further provides a complete hospital contact history of somatic and psychiatric conditions and procedures. Data on all prescriptions filled at community pharmacies are available from the Danish National Prescription Registry. Health-care authorization status is obtained from the Danish Register of Healthcare Professionals. Finally, selected laboratory values are obtained from the Register of Laboratory Results for Research. The cohort is governed by a steering committee with representatives from the Danish Medicines Agency, Statens Serum Institut, the Danish Health Authority, the Danish Health Data Authority, Danish Patients, the Faculties of Health Sciences at the Danish universities, and Danish regions. The steering committee welcomes suggestions for research studies and collaborations. Research proposals will be prioritized based on timeliness and potential clinical and public health implications. All research protocols assessing specific hypotheses for medicines will be made publicly available using the European Union electronic Register of Post-Authorisation Studies.

Conclusion

The Danish COVID-19 cohort includes all Danish residents with an RT-PCR test for SARS-CoV-2. Through individual-level linkage with existing Danish health and administrative registries, this is a valuable data source for epidemiological research on SARS-CoV-2.

Association of Nonsteroidal Anti-inflammatory Drug Use and Adverse Outcomes Among Patients Hospitalized With Influenza

IMPORTANCE

During the ongoing coronavirus disease 2019 pandemic, case reports have suggested that the use of nonsteroidal anti-inflammatory drugs (NSAIDs) may lead to adverse outcomes.

OBJECTIVE

To study the association of NSAID use with adverse outcomes in patients hospitalized with influenza or influenza pneumonia.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used propensity score matching among 7747 individuals aged 40 years or older who were hospitalized with influenza, confirmed by polymerase chain reaction or antigen testing, between 2010 and 2018. Data were collected using Danish nationwide registers. All analyses reported were performed on May 29, 2020.

EXPOSURES

Prescription fill of an NSAID within 60 days before admission.

MAIN OUTCOMES AND MEASURES

Risk ratio (RR) and risk difference (RD) with 95% CIs for intensive care unit admission and death within 30 days of admission.

RESULTS

A total of 7747 patients (median [interquartile range] age, 71 [59-80] years, 3980 [51.4%] men) with confirmed influenza were identified. Of these, 520 (6.7%) were exposed to NSAIDs. In the unmatched cohorts, 104 of 520 patients (20.0%) who used NSAIDs and 958 of 7227 patients (13.3%) who did not use NSAIDs were admitted to the intensive care unit. For death within 30 days of admission, we observed 37 events (7.1%) among those who used NSAIDs compared with 563 events (7.8%) among those who did not. Current NSAID use was associated with intensive care unit admission (RR, 1.51; 95% CI, 1.26 to 1.81; RD, 6.7%; 95% CI, 3.2% to 10.3%), while NSAID use was not associated with death (RR, 0.91; 95% CI, 0.66 to 1.26; RD, -0.7%; 95% CI, -3.0% to 1.6%). In the matched cohorts, risks were unchanged for patients who used NSAIDs, while 83 ICU admissions (16.0%) and 36 deaths (6.9%) were observed among matched individuals who did not use NSAIDs. Matched (ie, adjusted) analyses yielded attenuated risk estimates for intensive care unit admission (RR, 1.25; 95% CI, 0.95 to 1.63; RD, 4.0%; 95% CI, -0.6% to 8.7%) and death (RR, 1.03; 95% CI, 0.66 to 1.60; RD, 0.2%; 95% CI, -2.9% to 3.3%). Associations were more pronounced among patients who used NSAIDs for a longer period (eg, for intensive care unit admission: RR, 1.90; 95% CI, 1.19 to 3.06; RD, 13.4%; 95% CI, 4.0% to 22.8%).

CONCLUSIONS AND RELEVANCE

In this cohort study of adult patients hospitalized with influenza, the use of NSAIDs was not associated with 30-day intensive care unit admission or death in adjusted analyses. There was an association between long-term use of NSAIDs and intensive care unit admission.

Primary Epstein-Barr virus infection with and without infectious mononucleosis

Background

Infectious mononucleosis (IM) is a common adverse presentation of primary infection with Epstein-Barr virus (EBV) in adolescence and later, but is rarely recognized in early childhood where primary EBV infection commonly occurs. It is not known what triggers IM, and also not why IM risk upon primary EBV infection (IM attack rate) seemingly varies between children and adolescents. IM symptoms may be severe and persist for a long time. IM also markedly elevates the risk of Hodgkin lymphoma and multiple sclerosis for unknown reasons. The way IM occurrence depends on age and sex is incompletely described and hard to interpret etiologically, because it depends on three quantities that are not readily observable: the prevalence of EBV-naϊve persons, the hazard rate of seroconverting and the attack rate, i.e. the fraction of primary EBV infections that is accompanied by IM. We therefore aimed to provide these quantities indirectly, to obtain epidemiologically interpretable measures of the dynamics of IM occurrence to provide etiological clues.

Methods and findings

We used joint modeling of EBV prevalence and IM occurrence data to provide detailed sex- and age-specific EBV infection rates and IM attack rates and derivatives thereof for a target population of all Danes age 0–29 years in 2006–2011. We demonstrate for the first time that IM attack rates increase dramatically rather precisely in conjunction to typical ages of puberty onset. The shape of the seroconversion hazard rate for children and teenagers confirmed a priori expectations and underlined the importance of what happens at age 0–2 years. The cumulative risk of IM before age 30 years was 13.3% for males and 22.4% for females. IM is likely to become more common through delaying EBV infection in years to come.

Conclusions

The change in attack rate at typical ages of puberty onset suggests that the immunologic response to EBV drastically changes over a relatively short age-span. We speculate that these changes are an integrated part of normal sexual maturation. Our findings may inform further etiologic research into EBV-related diseases and vaccine design. Our methodology is applicable to the epidemiological study of any infectious agent that establishes a persistent infection in the host and the sequelae thereof.

P3661Two-fold increase in incidence of infective endocarditis in the period 1997–2016: a Danish nationwide study

Background

Infective Endocarditis (IE) is a disease with high mortality. Previous studies have shown considerable differences and contradicting trends in overall incidence and mortality why data from an unselected nationwide cohort is needed.

Purpose

We investigated temporal trends in the incidence rate and in-hospital mortality of IE in Denmark in the period of 1997–2016.

Methods

We included cases of first-time IE (1997–2016) using Danish nationwide registries. Crude incidence rates were given for each calendar year. Further, incidence rates were reported for subgroups of age and sex. For the analysis of patient characteristics and in-hospital mortality, the study cohort was grouped into four 5-year intervals (1997–2001, 2002–2006, 2007–2011, 2012–2016). Multivariable adjusted Cox proportional hazard model was used to compare in-hospital mortality between groups.

Results

A total of 8,147 patients with IE were identified in the period of 1997–2016. The median age and proportion of males increased from 64.3 years (P25-P75: 48–75.5) and 59.1% to 71.8 years (P25-P75: 62.1–79.9) and 67.1% in 1997–2001 and 2012–2016, respectively. The overall incidence rate (Figure 1) increased from 4.68/100.000-person-years (PY) (CI95: 4.17–5.26) to 8.23/100.000 PY (CI95: 7.53–8.99) in 1997 and 2016, respectively. Male incidence increased from 5.35/100.000 PY (CI95: 4.59–6.23) to 11.03/100.000 PY (CI95: 9.9–12.29) and female incidence increased from 4.03/100.000 PY (CI95: 3.38–4.8) to 5.44/100.000 PY (CI95: 4.67–6.35) in 1997 and 2016 respectively. Incidence rates increased more than seven-fold for the oldest age group (≥80 years) from 1997 to 2016 (6.95/100.000 PY [CI95: 5.32–9.08] to 51.19/100.000 PY [CI95: 43.41–60.38], respectively). In-hospital mortality was significantly lower for patients with IE in the period of 2011–2016 compared with 1997–2001 HR: 0.8 (CI95: 0.69–0.92).

Figure 1

Conclusion

Infective endocarditis incidences are increasing mostly among men and elderly patients. In order to prevent this disease as best as possible, we need more knowledge on causes for this increasing incidence.

P3665Prevalence of infective endocarditis in patients with positive blood cultures: a Danish nationwide study

Background

Increasing attention has been given to the risk of infective endocarditis (IE) in patients with certain blood stream infections (BSI). Previous studies have been conducted on selected patient cohorts, yet unselected data are sparse.

Purpose

To investigate the nationwide prevalence of diagnosed IE in BSIs with bacteria typically associated with IE.

Methods

By crosslinking nationwide registries from 2010–2016, we identified patients with BSIs typically associated with IE: Enterococcus faecalis, Staphylococcus, Streptococcus spp., and coagulase negative staphylococci (CoNS) and examined the concurrent IE prevalence. A trend test was used to examine temporal changes in the prevalence of IE.

Results

In total 60,119 BSIs, distributed with 15,407, 16,790, and 27,922 BSIs were identified in the periods of 2010–2011, 2012–2013, and 2014–2016, respectively.

Patients with E. Faecalis had the highest prevalence of diagnosed IE (16.3%) followed by S. aureus (10.2%), Streptococcus spp. (7.3%), and CoNS (1.6%) (Figure). During the study period, the prevalence of IE among patients with E. faecalis increased significantly (p=0.003), Male patients had higher prevalence of IE for all microorganisms investigated compared with females. A significant increase in the prevalence of IE was seen for E. faecalis, Streptococcus spp., and CoNS with increasing age.

Percent with endocarditis

Conclusion

For E. faecalis BSI, 1 in 6 had IE, for S. aureus BSI 1 in 10 had IE, and for Streptococcus spp. 1 in 14 had IE. Our results support screening for IE in patients with E. faecalis, S. aureus, or Streptococcus spp. BSI in order to offer appropriate therapy.

P3663Prevalence of infective endocarditis in patients with a left-sided heart valve prosthesis: a nationwide study

Background

Increasing attention has been given to patients with blood stream infection (BSI) and the concurrent prevalence of infective endocarditis (IE). However, there exist a gap in knowledge on the prevalence of IE among patients with a left-sided heart valve prosthesis and BSI.

Purpose

To examine the prevalence between different BSI and IE in patients with a left-sided heart valve prosthesis.

Methods

By linking Danish nationwide registries, we were able to identify patients with a left-sided prosthetic heart valve and first-time BSI of interest (Enterococcus faecalis, Staphylococcsus aureus, streptococci species (spp.), and coagulase negative staphylococci [CoNS]) in the period of 2010–2016. Concurrent admission for IE was identified from the Danish National Patient Registry in a period of up to 14 days after the BSI.

Results

A total of 1,465 patients with BSI were included (1,319 patients with an aortic valve prosthesis [82.6% bioprosthetic] and 146 patients with a mitral valve prosthesis [48.6% bioprosthetic]). Among the included patients, 244 had E. faecalis (median age: 78.3 years, 77.0% male), 301 had S. aureus (median age: 76.9 years, 69.1% male), 401 had streptococci spp. (median age: 78.0 years, 69.1% male) and 519 had CoNS (median age: 76.4 years, 64.2% male). The percentage of patients with a diagnosis of IE in relation to the BSI was 44.3%, 33.6%, 34.4%, and 7.9% for E. faecalis, S. aureus, streptococci spp., and CoNS, respectively. No difference in the overall results was seen by type of valve prosthesis, sex, or age group.

Percentage of patients with endocarditis

Conclusion

In patients with a left-sided heart valve prosthesis, IE was diagnosed in almost half of the patients with E. faecalis, in 1/3 with S. aureus or streptococci spp. and in 1 in 12 with CoNS BSI. Future studies may try to explain why some microbes are more likely to cause prosthetic heart valve endocarditis, than others are.

P2754Streptococcal infective endocarditis: distribution of species and their prognosis

Background

Infective endocarditis (IE) is frequently caused by streptococcal species. However, there is limited knowledge about the relationship between different streptococcal species and IE, and their associated outcomes.

Purpose

To examine the prevalence of streptococci at species level in IE, and to relate these different species to outcomes.

Methods

From 2002–2012 we prospectively collected consecutive patients with IE admitted to two tertiary heart centres covering a catchment area of 2.4 million people. The registry comprises 915 IE patients, 366 (40%) with streptococcal IE. Based on phylogenetic relationship, streptococcal species were classified into seven main groups: Mitis, Bovis, Mutans, Anginosus, Salivarius, Pyogenic and Nutritionally Variant Streptococcus (NVS). Classification at species level was not possible in 51 patients, who were excluded. Complications and prognosis of streptococcal IE were compared between the subgroups, and at species level.

Results

We included 315 patients with streptococcal IE. Mean age was 63 (IQR 52–76) years, and most were men (67%). A total of 115 patients (37%) had a previous heart valve disease, 58 (18%) had a prosthetic valve, 22 (7%) had previously had IE and 29 (9%) had a cardiac electronic device. With 148 episodes (47%) the Mitis group was the most common cause of IE. Other frequent groups were the Pyogenic group and the Bovis group, accounting for 66 (21%) and 51 (16%) of the cases, respectively. Surgery was carried out in 55% (n=173) of all cases. Patients infected with S. pneumoniae or S. agalactiae had a significantly higher rate of surgery, 72.2% (n=13) and 71.9% (n=23) respectively, whereas the Bovis group had a significantly lower rate, 35.5% (n=18) (p=0.048). The aortic valve was infected in 137 patients (43.5%), mitral valve in 105 patients (33.3%) and both valves were infected in 53 patients (16.8%). Twenty patients (6.3%) had right-sided IE, including pacemaker lead IE. There was no significant difference between the species subgroups regarding type of infected valve. Embolization and osteitis were observed in 76 (24.1%) and 30 (9.5%) patients, respectively. There was no significant difference between the species groups, as was the case with mortality: 23 patients (7.3%) died in-hospital and the one-year mortality was 16% (n=50).

Distribution of streptococcal IE

Conclusion

Species of the Mitis group were the most frequent Streptococci causing IE. Patients infected with S. pneumonia or S. agalactiae had significantly higher rate of surgery, and patients infected with S. bovis group had lower rate of surgery. There was no significant difference in rate of complications such as abscesses, embolization, osteitis or mortality between the streptococcal species.

Acknowledgement/Funding

Supported by grants from Herlev-Gentofte University Hospital Research Foundation

Incidence and seasonality of respiratory syncytial virus hospitalisations in young children in Denmark, 2010 to 2015

For future decisions on respiratory syncytial virus (RSV)-vaccination strategies and implementation into national immunisation-programmes, we used national registry data (hospitalisation, microbiology and vital statistics) to determine the age-specific incidence and direct medical costs of annual RSV-associated admissions in children < 5 years-old for the period of 2010–2015. We identified ca 2,500 RSV-associated hospitalisations annually amounting to total direct medical-costs of ca EUR 4.1 million per year. The incidence of RSV-associated hospitalisations peaked in infants 1–2 months of age followed by infants 2–3 months of age, and infants < 1 month of age, respectively. Infant boys were at higher risk of severe RSV infection as compared to infant girls: male-to-female ratio peaked with 1.4 at four months of age and gradually levelled out with increasing age to 1.0 at 4 years of age. Five RSV-associated deaths were identified. Our findings demonstrate that in a western country as Denmark, RSV constitutes a considerable burden on childhood health. Furthermore, the best approach to reduce the high incidence of RSV-associated hospitalisations in young infants < 3 months of age may be maternal vaccination due to general challenges in achieving sufficient and protective immune responses in young infants.

Incidence of HACEK bacteraemia in Denmark: A 6-year population-based study

OBJECTIVES

Bacteria with common microbiological and clinical characteristics are often recognized as a particular group. The acronym HACEK stands for five fastidious genera associated with infective endocarditis (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella). Data on the epidemiology of HACEK are sparse. This article reports a 6-year nationwide study of HACEK bacteraemia in Denmark.

METHODS

Cases of HACEK bacteraemia occurring during the years 2010-2015 were retrieved from the national Danish microbiology database, covering an average surveillance population of 5.6 million per year.

RESULTS

A total of 147 cases of HACEK bacteraemia were identified, corresponding to an annual incidence of 0.44 per 100000 population. The annual incidence for males was 0.56 per 100000 and for females was 0.31 per 100000. The median age was 56 years (range 0-97 years), with variation among the genera. One hundred and forty-three isolates were identified to the species level and six to the genus level: Haemophilus spp, n=55; Aggregatibacter spp, n=37; Cardiobacterium spp, n=9; Eikenella corrodens n=21; and Kingella spp, n=27.

CONCLUSIONS

This is the first study on the incidence of HACEK bacteraemia in a large surveillance population and may inspire further studies on the HACEK group. Haemophilus spp other than Haemophilus influenzae accounted for most cases of HACEK bacteraemia in Denmark, with Aggregatibacter spp in second place.

Storage time of platelet concentrates and risk of a positive blood culture: a nationwide cohort study

BACKGROUND

Concern of transfusion-transmitted bacterial infections has been the major hurdle to extend shelf life of platelet (PLT) concentrates. We aimed to investigate the association between storage time and risk of positive blood cultures at different times after transfusion.

STUDY DESIGN AND METHODS

We performed a nationwide cohort study among PLT transfusion recipients in Denmark between 2010 and 2012, as recorded in the Scandinavian Donations and Transfusions (SCANDAT2) database. Linking with a nationwide database on blood cultures (MiBa), we compared the incidence of a positive blood culture among recipients of PLTs stored 6 to 7 days (old) to those receiving fresh PLTs (1-5 days), using Poisson regression models. We considered cumulative exposures in windows of 1, 3, 5, and 7 days.

RESULTS

A total of 9776 patients received 66,101 PLT transfusions. The incidence rate ratio (IRR) of a positive blood culture the day after transfusion of at least one old PLT concentrate was 0.77 (95% confidence interval [CI], 0.54-1.09) compared to transfusion of fresh PLT concentrates. The incidence rate of a positive blood culture was lower the day after receiving one old compared to one fresh PLT concentrate (IRR, 0.57; 95% CI, 0.37-0.87). Three, 5, or 7 days after transfusion, storage time was not associated with the risk of a positive blood culture.

CONCLUSION

Storage of buffy coat-derived PLT concentrates in PAS-C up to 7 days seems safe regarding the risk of a positive blood culture. If anything, transfusion of a single old PLT concentrate may decrease this risk the following day.

Microbiological diagnosis in revision of infected knee arthroplasties in Denmark

BACKGROUND

Revision of infected knee arthroplasties is associated with high failure rates (30-40%). An understanding of the microbiology is important to optimize treatment and outcome. We describe microbiological diagnostic practice and diagnosis in revision of infected knee arthroplasties.

METHODS

One hundred and two partial revisions (open debridement and exchange of tibial insert) and 213 two-stage procedures performed due to infection in 275 patients from 1 July 2011 to 30 June 2013 were included and analysed by linkage to data from a nationwide registry on microbiological test results.

RESULTS

78 (24.8%) revisions were culture negative, 192 (60.9%) showed monomicrobial growth and 43 (14.3%) polymicrobial growth. Staphylococcus aureus was the most frequent isolate in mono-culture in 70 (22.2%) revisions and in polymicrobial culture in 15 revisions with a total frequency of 27.0%. Only one case (1.4%) of methicillin-resistance was registered. Coagulase-negative staphylococci (CoNS) were frequent, sole pathogen in 65 revisions and in polymicrobial cultures in 28 revisions with a total frequency of 29.5%. A pre-operative knee aspiration was performed in 50% and preoperative blood cultures were performed in 22% of cases. In 73% of the preoperative knee-aspirations bacteriological findings were fully or partially in accordance with intraoperative cultures. In 54% of the later re-revisions due to infection (treatment-failures) the cultured species differed from or was not detected at index revision surgery.

CONCLUSIONS

The 25% culture negative cases in combination with only 50% preoperative knee aspirations and prevailing high failure rates confirm the need for improvement of diagnostic practice and treatment of infected knee arthroplasties.

Evaluation of the enterovirus laboratory surveillance system in Denmark, 2010 to 2013

The primary aim of the Danish enterovirus (EV) surveillance system is to document absence of poliovirus infection. The conflict in Syria has left many children unvaccinated and movement from areas with polio cases to Europe calls for increased awareness to detect and respond to virus-transmission in a timely manner. We evaluate the national EV laboratory surveillance, to generate recommendations for system strengthening. The system was analysed for completeness of viral typing analysis and clinical information and timeliness of specimen collection, laboratory results and reporting of clinical information. Of 23,720 specimens screened, 2,202 (9.3%) were EV-positive. Submission of cerebrospinal fluid and faecal specimens from primary diagnostic laboratories was 79.5% complete (845/1,063), and varied by laboratory and patient age. EV genotypes were determined in 68.5% (979/1,430) of laboratory-confirmed cases, clinical information was available for 63.1% (903/1,430). Primary diagnostic results were available after a median of 1.4 days, typing results after 17 days, detailed clinical information after 33 days. The large number of samples typed demonstrated continued monitoring of EV-circulation in Denmark. The system could be strengthened by increasing the collection of supplementary faecal specimens, improving communication with primary diagnostic laboratories, adapting the laboratory typing methodology and collecting clinical information with electronic forms.

Fusobacterium necrophorum findings in Denmark from 2010 to 2014 using data from the Danish microbiology database

Fusobacterium necrophorum findings in Denmark and estimation of the incidence of F. necrophorum bacteraemia was described using data from the nationwide Danish microbiology database (MiBa). All microbiological reports on any Fusobacterium species in Denmark were extracted for a period of 5 years from 2010 to 2014 from MiBa and from the local department of clinical microbiology. The overall incidence of F. necrophorum bacteraemia from 2010 to 2014 was 2.8 cases per million/year vs 9.4 in the age group 15-24 years. F. necrophorum was rare in blood cultures from children and middle-aged patients and then raised again. However, 48 of 232 cases of Fusobacterium bacteraemia were not identified to species level, so the incidences of F. necrophorum bacteraemia may be underestimated in our study. F. necrophorum was found in throat swabs in the age group between 13 and 40 years and in otitis media in children below 2 years in those departments which performed anaerobic culture. The incidence of F. necrophorum bacteraemia found was comparable to earlier reported figures for Lemierre's syndrome. Fusobacterium bacteraemia should always be identified to species level.

Improving national surveillance of Lyme neuroborreliosis in Denmark through electronic reporting of specific antibody index testing from 2010 to 2012

Our aim was to evaluate the results of automated surveillance of Lyme neuroborreliosis (LNB) in Denmark using the national microbiology database (MiBa), and to describe the epidemiology of laboratory-confirmed LNB at a national level. MiBa-based surveillance includes electronic transfer of laboratory results, in contrast to the statutory surveillance based on manually processed notifications. Antibody index (AI) testing is the recommend laboratory test to support the diagnosis of LNB in Denmark. In the period from 2010 to 2012, 217 clinical cases of LNB were notified to the statutory surveillance system, while 533 cases were reported AI positive by the MiBa system. Thirty-five unconfirmed cases (29 AI-negative and 6 not tested) were notified, but not captured by MiBa. Using MiBa, the number of reported cases was increased almost 2.5 times. Furthermore, the reporting was timelier (median lag time: 6 vs 58 days). Average annual incidence of AI-confirmed LNB in Denmark was 3.2/100,000 population and incidences stratified by municipality ranged from none to above 10/100,000. This is the first study reporting nationwide incidence of LNB using objective laboratory criteria. Laboratory-based surveillance with electronic data-transfer was more accurate, complete and timely compared to the surveillance based on manually processed notifications. We propose using AI test results for LNB surveillance instead of clinical reporting.

Cryptosporidium infections in Denmark, 2010-2014

INTRODUCTION

The incidence of cryptosporidiosis in Denmark is unknown. Here, we present the number of cases detected in the 2010-2014 period along with data on species and subtypes.

METHODS

Complete national data retrieved from the Danish Microbiology Database and Statens Serum Institut (SSI) comprised test results on cryptosporidia detected by microscopy or polymerase chain reaction (PCR) between 1 January 2010 and 30 April 2014. Samples that tested positive at the SSI were submitted to species and subtype analysis by conventional PCR and sequencing of ribosomal and gp60 genes, respectively.

RESULTS

A total of 689 Cryptosporidium-positive stool samples were submitted by 387 patients. Limiting case episodes to two months (60 days), a total of 388 case episodes representing 387 patients were identified. Cryptosporidiosis was most common among infants and toddlers. Moreover, a peak in incidence was observed among younger adults aged 23-24 years. In 43 Cryptosporidium-positive faecal samples, identification was performed to species and subtype level. Cryptosporidium parvum was found in 34 samples, C. hominis in eight, and C. meleagridis in one sample; C. parvum subtypes IIaA15G2R1 (n = 10) and IIaA16G3R1 (n = 5) were predominating.

CONCLUSION

Cryptosporidia are a significant cause of diarrhoea in Denmark. Outbreaks may not be detected due to continued use of diagnostic tests of limited sensitivity and due to lack of surveillance. With molecular methods now being introduced in many Danish laboratories, we propose establishing national surveillance of cryptosporidiosis.

FUNDING

not relevant.

TRIAL REGISTRATION

not relevant.

The Danish Microbiology Database (MiBa) 2010 to 2013

The Danish Microbiology Database (MiBa) is a national database that receives copies of reports from all Danish departments of clinical microbiology. The database was launched in order to provide healthcare personnel with nationwide access to microbiology reports and to enable real-time surveillance of communicable diseases and microorganisms. The establishment and management of MiBa has been a collaborative process among stakeholders, and the present paper summarises lessons learned from this nationwide endeavour which may be relevant to similar projects in the rapidly changing landscape of health informatics.

Low vaccine effectiveness against influenza A(H3N2) virus among elderly people in Denmark in 2012/13 – a rapid epidemiological and virological assessment

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Low vaccine effectiveness against influenza A(H3N2) virus among elderly people in Denmark in 2012/13--a rapid epidemiological and virological assessment

In Denmark, the 2012/13 influenza season has been dominated by influenza A(H3N2). We estimated the vaccine effectiveness (VE) of the trivalent influenza vaccine by linking national registers in a test-negative case-control study of patients tested for influenza aged ≥65 years. The adjusted VE against laboratory-confirmed influenza A and B was -11% (95% CI: -41 to 14) and 69% (95% CI: 26 to 87), respectively. Genetic characterisation of the influenza A(H3N2) viruses indicated genetic drift, with seven substitutions at key antigenic sites.

Real-time surveillance of laboratory confirmed influenza based on the Danish microbiology database (MiBa)

The Danish microbiology database (MiBa) is a national database that automatically accumulates patient test results from all Danish Departments of Clinical Microbiology. As an example for use of MiBa, we describe the real-time surveillance of laboratory confirmed influenza established in October 2012. It functions without any extra burdens of reporting by laboratories or clinicians. This is an important improvement of the existing surveillance for influenza like illness (ILI) which includes only limited virological testing. The MiBa based surveillance adds complete national virological data which are specific for influenza, in contrast to ILI, and serves as a tool for regional and national preparedness and planning.

Increased incidence of Mycoplasma pneumoniae infections detected by laboratory-based surveillance in Denmark in 2010

In Denmark recurrent epidemics of Mycoplasma pneumoniae infections have been described since the 1950s at intervals of approximately four to six years. The latest epidemic occurred in 2004/05 followed by two years of high incidence and more than three years of low incidence. Due to a recent increase in diagnosed cases since late summer 2010, we conducted a survey of positive M. pneumoniae PCR tests performed by clinical microbiology departments in Denmark, which indicated that a new epidemic may be underway.

Increased incidence of Mycoplasma pneumoniae infections detected by laboratory-based surveillance in Denmark in 2010

In Denmark recurrent epidemics of Mycoplasma pneumoniae infections have been described since the 1950s at intervals of approximately four to six years. The latest epidemic occurred in 2004/05 followed by two years of high incidence and more than three years of low incidence. Due to a recent increase in diagnosed cases since late summer 2010, we conducted a survey of positive M. pneumoniae PCR tests performed by clinical microbiology departments in Denmark, which indicated that a new epidemic may be underway.