Comparative epidemiology of bacteraemia in two ageing populations: Singapore and Denmark.

Burden of bacteraemia is rising due to increased average life expectancy in developed countries. This study aimed to compare the epidemiology and outcomes of bacteraemia in two similarly ageing populations with different ethnicities in Singapore and Denmark. Historical cohorts from the second largest acute-care hospital in Singapore and in the hospitals of two Danish regions included patients aged 15 and above who were admitted from 1 January 2006 to 31 December 2016 with at least 1 day of hospital stay and a pathogenic organism identified. Among 13 144 and 39 073 bacteraemia patients from Singapore and Denmark, similar 30-day mortality rates (16.5%; 20.3%), length of hospital stay (median 14 (IQR: 9-28) days; 11 (6-21)), and admission rate to ICU (15.5%; 15.6%) were observed, respectively. Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus ranked among the top four in both countries. However, Singaporeans had a higher proportion of patients with diabetes (46.8%) and renal disease (29.5%) than the Danes (28.0% and 13.7%, respectively), whilst the Danes had a higher proportion of patients with chronic pulmonary disease (18.0%) and malignancy (35.3%) than Singaporeans (9.7% and 16.2%, respectively). Our study showed that top four causative organisms and clinical outcomes were similar between the two cohorts despite pre-existing comorbidities differed.

The ESCMID Study Group for Clostridioides difficile: History, Role, and Perspectives.

Clostridioides difficile (C. difficile) is a major nosocomial pathogen but is also increasingly recognised as an important diarrhoeal pathogen in the community, not always associated with antibiotics. The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for C. difficile (ESGCD) is a group of clinicians, scientists, and others from many European countries and further afield, who share a common interest in C. difficile. The aims of the Study Group are centred around raising the profile of  C. difficile infection (CDI) in humans and animals, fostering collaboration amongst centres in different European countries and providing a forum for discussing and disseminating information. One of the principal aims of the Study Group is to raise awareness of C. difficile infections in Europe. ESGCD has a particular interest in the development and dissemination of European guidance on prevention, diagnosis, and treatment of CDI. This chapter will discuss the organisation of ESGCD within the ESCMID Study Group structure, the origins of the Study Group, the aims, and objectives of the group, and will highlight some of the past and present activities of ESGCD in relation to these.

Low protection from breakthrough SARS-CoV-2 infection and mild disease course in ocrelizumab-treated patients with multiple sclerosis after three mRNA vaccine doses.

BACKGROUND: Our study investigated the rate of breakthrough SARS-CoV-2 infection and clinical outcomes in a cohort of multiple sclerosis (MS) patients who were treated with the anti-CD20 monoclonal antibody (Ab), ocrelizumab, before first, second and third BNT162b2 mRNA vaccinations. To correlate clinical outcomes with the humoral and cellular response. METHODS: The study was a prospective non-randomised controlled multicentre trial observational study. Participants with a diagnosis of MS who were treated for at least 12 months with ocrelizumab prior to the first BNT162b2 mRNA vaccination were prospectively followed up from January 2021 to June 2022. RESULTS: Out of 54 participants, 32 (59.3%) developed a positive SARS-CoV-2 PCR test in the study period. Mild infection was observed in all infected participants. After the third vaccination, the non-infected participants had higher mean Ab levels compared to the infected participants (54.3 binding antibody unit (BAU)/mL vs 26.5 BAU/mL, p=0.030). The difference in reactivity between spike-specific CD4+ and CD8+ T lymphocytes in the two groups was not significant. CONCLUSION AND RELEVANCE: The study results demonstrate rates of 59% in breakthrough infections after the third SARS-CoV-2 mRNA vaccination in ocrelizumab-treated patients with MS, without resulting in critical disease courses. These findings suggest the need for continuous development of prophylactic treatments when proved important in the protection of severe breakthrough infection.

Imported spring onions related to the first recorded outbreak of enteroinvasive Escherichia coli in Denmark, November to December 2021.

Between November and December 2021, the first ever recorded outbreak of enteroinvasive Escherichia coli in Denmark occurred at national scale. We describe the investigation of this outbreak, which was initially recognised in early December 2021. A total of 88 cases (58 female; 30 male) with a median age of 52 years (range: 0-91) were detected by PCR-based diagnostic methods. Case ascertainment was complicated by current culture-free diagnostic procedures, with only 34 cases confirmed by culture, serotyping and whole genome sequencing. Isolates from cases grouped into two serotypes (O136:H7 and O96:H19), which was supported by whole-genome-sequence-phylogeny, also yielding two clusters. Interviews of 42 cases and traceback investigation pointed towards consumption of ready-to-eat salads as the outbreak cause. While the ready-to-eat salads comprised different vegetables, imported spring onions were the only common ingredient and thus the likely source. Environmental investigations failed to recover outbreak strains. This report highlights the value of fast typing (here O-typing) to confirm cases in an outbreak situation. Timely communication and data sharing are also important, and were facilitated by the national collaboration between relevant laboratories, the public health institute and the veterinary and food administration. High hygiene standards for imported fresh vegetables intended for ready-to-eat products are essential.

Bacteremia With Anaerobic Bacteria and Association With Colorectal Cancer: A Population-based Cohort Study.

BACKGROUND: There is a well-described association between bacteremia with bovis group streptococci or Clostridium septicum and an increased probability of a colorectal cancer (CRC) diagnosis. We wanted to investigate the existence of a similar association between CRC and bacteremia with other bacteria belonging to the gut microbiota.. METHODS: A population based cohort study in a population about 2 million people including 45 774 bacteremia episodes and 231 387 blood culture negative cases was performed in the Region of Southern Denmark and Region Zealand from 2007-2016. Episodes of bacteremia were combined with the Danish central register for CRC. We performed Cox's regression analysis with hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS: The study results confirmed previous findings of an increased risk of a CRC diagnosis after bacteremia with the bovis group streptococci (risk within a year: 4.3%; HR [95% CI]: 8.46 [3.51-20.4]) or C. septicum (20.8%; 76.2 [42.0-138]). Furthermore, Bacteroides ovatus (6.7%; 20.3 [5.04-81.8]), Bacteroides uniformis (5.4%; 16.2 [4.02-65.7]), Clostridium tertium (3.6 %; 13.9 [1.96-99.4]), Fusobacterium spp. (excluding F. necrophorum) (3.0 %; 8.51 [2.73-26.5]), and Gram-positive anaerobic cocci (3.6 %; 10.9 [4.50-26.3]) were also associated with an increased risk of a CRC diagnosis compared to patients with negative blood cultures (0.4%). CONCLUSIONS: Bacteremia with specific gut microbiota anaerobic bacteria is associated with a high risk of a diagnosis of CRC, indicating the need for colorectal workup. Importantly, this strategy also holds the possible additional benefit of detecting adenomas or other premalignant conditions, which were not included in the present study.

Sentinel surveillance and epidemiology of Clostridioides difficile in Denmark, 2016 to 2019.

BackgroundSince 2008, Danish national surveillance of Clostridioides difficile has focused on binary toxin-positive strains in order to monitor epidemic types such as PCR ribotype (RT) 027 and 078. Additional surveillance is needed to provide a more unbiased representation of all strains from the clinical reservoir.AimSetting up a new sentinel surveillance scheme for an improved understanding of type distribution relative to time, geography and epidemiology, here presenting data from 2016 to 2019.MethodsFor 2─4 weeks in spring and autumn each year between 2016 and 2019, all 10 Danish Departments of Clinical Microbiology collected faecal samples containing toxigenic C. difficile. Isolates were typed at the national reference laboratory at Statens Serum Institut. The typing method in 2016-17 used tandem-repeat-sequence typing, while the typing method in 2018-19 was whole genome sequencing.ResultsDuring the study period, the sentinel surveillance scheme included ca 14-15% of all Danish cases of C. difficile infections. Binary toxin-negative strains accounted for 75% and 16 of the 20 most prevalent types. The most common sequence types (ST) were ST2/13 (RT014/020) (19.5%), ST1 (RT027) (10.8%), ST11 (RT078) (6.7%), ST8 (RT002) (6.6%) and ST6 (RT005/117) (5.1%). The data also highlighted geographical differences, mostly related to ST1 and temporal decline of ST1 (p = 0.0008) and the increase of ST103 (p = 0.002), ST17 (p = 0.004) and ST37 (p = 0.003), the latter three binary toxin-negative.ConclusionSentinel surveillance allowed nationwide monitoring of geographical differences and temporal changes in C. difficile infections in Denmark, including emerging types, regardless of binary toxin status.

Herpes Simplex Virus Type 1 Pneumonia-A Review.

BACKGROUND: Pneumonia due to herpes simplex virus (HSV) is uncommon but can be seen in immunocompromised patients and has been associated with poor prognosis in this population. AIM: The aim was to study the results, outcome and mortality of HSV pneumonia in immunocompromised patients and patients receiving mechanical ventilation. Furthermore, it has been unclear whether to initiate prophylactic treatment with acyclovir or not. METHODS: We have conducted a literature search using the keywords herpes simplex pneumonia, critically ill patients and intensive care unit for identification of relevant publications. FINDINGS: HSV pneumonia can cause severe infection or even death in immunocompromised patients and critically ill patients. A clear diagnosis of HSV pneumonia can be difficult to establish. Respiratory condition may improve after initiation of acyclovir but data is scarce. CONCLUSION: HSV pneumonia should be considered in the immunocompromised patient and/or the intensive care patient who continues to deteriorate despite appropriate treatment. The value of prophylactic treatment with acyclovir is unproven but should be considered.

Longitudinal trajectory patterns of plasma albumin and C-reactive protein levels around diagnosis, relapse, bacteraemia, and death of acute myeloid leukaemia patients.

BACKGROUND: No study has evaluated C-reactive protein (CRP) and plasma albumin (PA) levels longitudinally in patients with acute myeloid leukaemia (AML). METHODS: We studied defined events in 818 adult patients with AML in relation to 60,209 CRP and PA measures. We investigated correlations between CRP and PA levels and daily CRP and PA levels in relation to AML diagnosis, AML relapse, or bacteraemia (all ±30 days), and death (─30-0 days). RESULTS: On the AML diagnosis date (D0), CRP levels increased with higher WHO performance score (PS), e.g. patients with PS 3/4 had 68.1 mg/L higher CRP compared to patients with PS 0, adjusted for relevant covariates. On D0, the PA level declined with increasing PS, e.g. PS 3/4 had 7.54 g/L lower adjusted PA compared to PS 0. CRP and PA levels were inversely correlated for the PA interval 25-55 g/L (R = - 0.51, p < 10-5), but not for ≤24 g/L (R = 0.01, p = 0.57). CRP increases and PA decreases were seen prior to bacteraemia and death, whereas no changes occurred up to AML diagnosis or relapse. CRP increases and PA decreases were also found frequently in individuals, unrelated to a pre-specified event. CONCLUSIONS: PA decrease is an important biomarker for imminent bacteraemia in adult patients with AML.

Surveillance of vancomycin-resistant enterococci reveals shift in dominating clones and national spread of a vancomycin-variable vanA Enterococcus faecium ST1421-CT1134 clone, Denmark, 2015 to March 2019.

We describe clonal shifts in vanA Enterococcus faecium isolates from clinical samples obtained from patients in Denmark from 2015 to the first quarter (Q1) of 2019. During Q1 2019, the vancomycin-variable enterococci (VVE) ST1421-CT1134 vanA E. faecium became the most dominant vanA E. faecium clone and has spread to all five regions in Denmark. Among 174 E. faecium isolates with vanA, vanB or vanA/vanB genes in Q1 2019, 44% belonged to this type.

The ESCMID Study Group for Clostridium difficile: History, Role and Perspectives.

C. difficile is a major nosocomial pathogen, but is also increasingly recognised as an important diarrhoeal pathogen in the community, not always associated with antibiotics. The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Clostridium difficile (ESGCD) is a group of clinicians and scientists from many European countries and further afield, who share a common interest in C. difficile. The aims of the Study Group are centred around raising the profile of CDI in humans and animals, fostering collaboration amongst centres in different European countries and providing a forum for discussing and disseminating information. One of the principal aims of the Study Group is to raise awareness of C. difficile infections in European hospitals. ESGCD has a particular interest in the development and dissemination of European guidance on prevention, diagnosis and treatment of CDI. This chapter will discuss the organisation of ESGCD within the ESCMID Study Group structure, the origins of the Study Group, the aims and objectives of the group, and will highlight some of the past and present activities of ESGCD in relation to these.

Impact of recurrent Clostridium difficile infection: hospitalization and patient quality of life.

Objectives: Data quantifying outcomes of recurrent Clostridium difficile infection (rCDI) are lacking. We sought to determine the UK hospital resource use and health-related quality of life (HRQoL) associated with rCDI hospitalizations. Patients and methods: A non-interventional study in six UK acute hospitals collected retrospective clinical and resource use data from medical records of 64 adults hospitalized for rCDI and 64 matched inpatient controls with a first episode only (f)CDI. Patients were observed from the index event (date rCDI/fCDI confirmed) for 28 days (or death, if sooner); UK-specific reference costs were applied. HRQoL was assessed prospectively in a separate cohort of 30 patients hospitalized with CDI, who completed the EQ-5D-3L questionnaire during their illness. Results: The median total management cost (post-index) was £7539 and £6294 for rCDI and fCDI, respectively (cost difference, P = 0.075); median length of stay was 21 days and 15.5 days, respectively (P = 0.269). The median cost difference between matched rCDI and fCDI cases was £689 (IQR=£1873-£3954). Subgroup analysis demonstrated the highest median costs (£8542/patient) in severe rCDI cases. CDI management costs were driven primarily by hospital length of stay, which accounted for >85% of costs in both groups. Mean EQ-5D index values were 46% lower in CDI patients compared with UK population values (0.42 and 0.78, respectively); EQ visual analogue scale scores were 38% lower (47.82 and 77.3, respectively). Conclusions: CDI has considerable impact on patients and healthcare resources. This multicentre study provides a contemporaneous estimate of the real-world UK costs associated with rCDI management, which are substantial and comparable to fCDI costs.

Carbapenemase-producing Enterobacteriaceae in the UK: a national study (EuSCAPE-UK) on prevalence, incidence, laboratory detection methods and infection control measures.

OBJECTIVES: To estimate UK prevalence and incidence of clinically significant carbapenemase-producing Enterobacteriaceae (CPE), and to determine epidemiological characteristics, laboratory methods and infection prevention and control (IPC) measures in acute care facilities. METHODS: A 6 month survey was undertaken in November 2013-April 2014 in 21 sentinel UK laboratories as part of the European Survey on Carbapenemase-Producing Enterobacteriaceae (EuSCAPE) project. Up to 10 consecutive, non-duplicate, clinically significant and carbapenem-non-susceptible isolates of Escherichia coli or Klebsiella pneumoniae were submitted to a reference laboratory. Participants answered a questionnaire on relevant laboratory methods and IPC measures. RESULTS: Of 102 isolates submitted, 89 (87%) were non-susceptible to ≥1 carbapenem, and 32 (36%) were confirmed as CPE. CPE were resistant to most antibiotics, except colistin (94% susceptible), gentamicin (63%), tigecycline (56%) and amikacin (53%). The prevalence of CPE was 0.02% (95% CI = 0.01%-0.03%). The incidence of CPE was 0.007 per 1000 patient-days (95% CI = 0.005-0.010), with north-west England the most affected region at 0.033 per 1000 patient-days (95% CI = 0.012-0.072). Recommended IPC measures were not universally followed, notably screening high-risk patients on admission (applied by 86%), using a CPE 'flag' on patients' records (70%) and alerting neighbouring hospitals when transferring affected patients (only 30%). Most sites (86%) had a laboratory protocol for CPE screening, most frequently using chromogenic agar (52%) or MacConkey/CLED agars with carbapenem discs (38%). CONCLUSIONS: The UK prevalence and incidence of clinically significant CPE is currently low, but these MDR bacteria affect most UK regions. Improved IPC measures, vigilance and monitoring are required.

Salmonella infection in grey seals (Halichoerus grypus), a marine mammal sentinel species: pathogenicity and molecular typing of Salmonella strains compared with human and livestock isolates.

Microbial pollution of the marine environment through land-sea transfer of human and livestock pathogens is of concern. Salmonella was isolated from rectal swabs of free-ranging and stranded grey seal pups (21.1%; 37/175) and compared with strains from the same serovars isolated from human clinical cases, livestock, wild mammals and birds in Scotland, UK to characterize possible transmission routes using pulsed-field gel electrophoresis and multi-locus variable number of tandem repeat analyses. A higher prevalence of Salmonella was found in pups exposed to seawater, suggesting that this may represent a source of this pathogen. Salmonella Bovismorbificans was the most common isolate (18.3% pups; 32/175) and was indistinguishable from isolates found in Scottish cattle. Salmonella Typhimurium was infrequent (2.3% pups; 4/175), mostly similar to isolates found in garden birds and, in one case, identical to a highly multidrug resistant strain isolated from a human child. Salmonella Haifa was rare (1.1% pups; 2/175), but isolates were indistinguishable from that of a human clinical isolate. These results suggest that S. Bovismorbificans may circulate between grey seal and cattle populations and that both S. Typhimurium and S. Haifa isolates are shared with humans, raising concerns of microbial marine pollution.

Sentinel community Clostridium difficile infection (CDI) surveillance in Scotland, April 2013 to March 2014.

Surveillance of Clostridium difficile infection (CDI) in Scotland does not currently distinguish between CDI cases from hospitals and the community. Therefore, the incidence of CDI in the community is unknown, and the burden of disease and the relationship with the hospital/healthcare setting is not well understood. A one-year sentinel community surveillance programme was initiated in collaboration with five Scottish health boards in 2013 (representing 36% of all CDI cases reported in Scotland). Inclusion criteria were all cases aged ≥15 years with a CDI diagnosis in the community or within 48 h following admission to hospital. CDI cases were categorised according to definitions used by the European Centre for Disease Prevention and Control. 256 CDI cases met the inclusion criteria, of which 158 (62%) were community-associated cases (CA-CDI). This represented 26% of all cases reported during the surveillance period by the participating health boards (n = 614). The overall CA-CDI incidence rate was 9.9 per 100 000 population per year. CA-CDI cases were more likely to be female and younger, compared to hospital acquired cases (HA-CDI). The total proportion of cases that had onset in the community was 27%. Ribotypes 015, 002, 078 and 005 were the most common types isolated from both CA-CDI and HA-CDI cases. There were no statistically significant differences between the proportion of types that were either CA-CDI or HA-CDI. Of the CA-CDI cases, 37% had not received antibiotics in the 12 weeks preceding CDI diagnosis, 4% were resident in care homes, and the case-fatality rate for CA-CDI cases was 5.6% (with a 30-day mortality rate for CA-CDI of 0.44 per 100 000 population per year). This study has shown that a substantial proportion of CDI cases reported in Scotland are community associated and that there are close links between the community and healthcare settings. It is therefore essential to monitor the trends in CDI in the community at a national level. The study also provides evidence for the need to examine the feasibility for development of interventions to reduce the burden in the community in addition to hospitals.

Synergistic efficacy of 405 nm light and chlorinated disinfectants for the enhanced decontamination of Clostridium difficile spores.

The ability of Clostridium difficile to form highly resilient spores which can survive in the environment for prolonged periods causes major contamination problems. Antimicrobial 405 nm light is being developed for environmental decontamination within hospitals, however further information relating to its sporicidal efficacy is required. This study aims to establish the efficacy of 405 nm light for inactivation of C. difficile vegetative cells and spores, and to establish whether spore susceptibility can be enhanced by the combined use of 405 nm light with low concentration chlorinated disinfectants. Vegetative cells and spore suspensions were exposed to increasing doses of 405 nm light (at 70-225 mW/cm(2)) to establish sensitivity. A 99.9% reduction in vegetative cell population was demonstrated with a dose of 252 J/cm(2), however spores demonstrated higher resilience, with a 10-fold increase in required dose. Exposures were repeated with spores suspended in the hospital disinfectants sodium hypochlorite, Actichlor and Tristel at non-lethal concentrations (0.1%, 0.001% and 0.0001%, respectively). Enhanced sporicidal activity was achieved when spores were exposed to 405 nm light in the presence of the disinfectants, with a 99.9% reduction achieved following exposure to 33% less light dose than required when exposed to 405 nm light alone. In conclusion, C. difficile vegetative cells and spores can be successfully inactivated using 405 nm light, the sporicidal efficacy can be significantly enhanced when exposed in the presence of low concentration chlorinated disinfectants. Further research may lead to the potential use of 405 nm light decontamination in combination with selected hospital disinfectants to enhance C. difficile cleaning and infection control procedures.

Gram-negative bacteraemia in haemodialysis.

BACKGROUND: Patients on renal replacement therapy experience higher rates of morbidity and mortality, infection being the second commonest cause of death. In our haemodialysis population, we identify the pathogens, sensitivity patterns, sources of infection and outcomes of Gram-negative bacteraemia. METHODS: Data from the NHS Greater Glasgow & Clyde and NHS Forth Valley haemodialysis population were collected July 2011 to April 2014 through an interrogation of the renal unit electronic patient record, and confirmed by an independent search of the Microbiology database. RESULTS: Over 544 377 haemodialysis days, 84 patients experienced 95 Gram-negative bacteraemia events, a rate of 0.175 events per 1000 haemodialysis days, which varied with dialysis modality: non-tunnelled central venous catheters 4.77, arteriovenous grafts 0.24, tunnelled central venous catheters 0.21, and arteriovenous fistulae 0.11 per 1000 haemodialysis days. The commonest sources of bacteraemia were central venous catheters (CVCs) (16.8%, n = 16), infected ulcers (14.7%, n = 14), urinary (10.5%, n = 10), biliary (9.5%, n = 9) and intra-abdominal (9.5%, n = 9).The principal organisms were Escherichia coli (49.5%, n = 47), Enterobacter spp. (13.1%, n = 13), Klebsiella spp. (11.1%, n = 11), Proteus mirabilis (6.1%, n = 6) and Pseudomonas aeruginosa (5.1%, n = 5). Of the Enterobacteriaceae (n = 84), 88% were sensitive to gentamicin, 81% to ciprofloxacin, 91% to piperacillin-tazobactam and 100% were sensitive to meropenem.Three-month case mortality was 25.3% (n = 24). Ten patients (11.9%) had more than one Gram-negative bacteraemia; of these, nine patients (90.0%) were the same causative organism, predominantly E. coli. CONCLUSIONS: CVCs and diabetic foot ulcers remain significant risk factors for Gram-negative bacteraemia, highlighting the importance of vascular access planning. Despite good levels of antibiotic sensitivity, the early mortality following Gram-negative bacteraemia remains high, supporting aggressive treatment of such pathogens.

Use of respiratory and facial protection.

Infectious microorganisms can be transmitted by various routes. Respiratory and facial protection is needed to prevent infection with organisms that are usually transmitted through the droplet/airborne route, or when airborne particles have been artificially created, for example during aerosol-generating procedures. Recent experiences with severe acute respiratory syndrome and pandemic (H1N1) influenza in 2009 highlighted that health professionals may have difficulty in choosing the correct facial and respiratory protection. The Scientific Development Committee of the Healthcare Infection HealtSociety established a working group to develop guidance addressing this issue.

Impact of COVID-19 Restrictions on Incidence of Enteropathogenic Bacteria, Virus, and Parasites in Denmark: A National, Register-Based Study.

Diarrheal diseases caused by enteric pathogens are a significant public health concern. It is widely considered that close contact between persons, poor hygiene, and consumption of contaminated food are the primary causes of gastroenteritis. Clinical microbiology laboratory observations indicate that the incidence of enteropathogenic microorganisms may have been reduced in Denmark during the COVID-19 pandemic. All Departments of Clinical Microbiology in Denmark provided data on the monthly incidence of Salmonella spp., Escherichia coli, Campylobacter spp., Clostridioides difficile, Norovirus GI+GII, Giardia duodenalis, and Cryptosporidium from March 2018 to February 2021. The data were divided into three periods as follows: Control Period 1 (March 2018 to February 2019); Control Period 2 (March 2019 to February 2020); and the Restriction (pandemic) Period (March 2020 to February 2021). The incidences of pathogenic Salmonella spp.-, Escherichia coli-, and Campylobacter spp.-positive samples decreased by 57.3%, 48.1%, and 32.9%, respectively, during the restriction period. No decrease in C. difficile was observed. Norovirus GI+GII-positive samples decreased by 85.6%. Giardia duodenalis-positive samples decreased by 66.2%. Cryptosporidium species decreased by 59.6%. This study demonstrates a clear decrease in the incidence of enteropathogenic bacteria (except for C. difficile), viruses, and parasites during the SARS-CoV-2 restriction period in Denmark.

Colorectal cancer and association with anaerobic bacteraemia: a Danish nationwide population-based cohort study.

OBJECTIVES: We aimed to identify specific anaerobic bacteria causing bacteraemia and a subsequent diagnosis of colorectal cancer. METHODS: A nationwide population-based cohort study, which included all episodes of defined specific anaerobic bacteraemia from 2010 (5,534,738 inhabitants) through 2020 (5,822,763 inhabitants) and all cases of colorectal cancer diagnosed from 2010 through 2021 in Denmark. We calculated the incidence and risk of colorectal cancer after bacteraemia with specific anaerobic bacteria using Escherichia coli bacteraemia as reference. RESULTS: Nationwide data on colorectal cancer and specific anaerobic bacteraemia (100% complete, representing 11,124 episodes). The frequencies of colorectal cancer within one year following anaerobic bacteraemia were higher for species, which almost exclusively reside in the colon, such as Phocaeicola vulgatus/dorei (5.5%), Clostridium septicum (24.2%), and Ruminococcus gnavus (4.6%) compared to 0.6% in 50,650 E. coli bacteraemia episodes. Bacteroides spp. had a subhazard ratio for colorectal cancer of 3.9 (95% confidence interval [CI], 3.0 to 5.1) and for Clostridium spp. it was 8.9 (95% CI, 6.7 to 11.8, with C. septicum 50.0 [95% CI, 36.0 to 69.5]) compared to E. coli (reference). CONCLUSION: This nationwide study identified specific colorectal cancer-associated anaerobic bacteria, which almost exclusively reside in the colon. Bacteraemia with these bacteria could be an indicator of colorectal cancer.