Anders Skyrud Danielsen

This study aimed to describe temporal changes in the incidence and microbial composition of bacteraemia in Norway from 2005 to 2024. Using national surveillance data from all microbiology laboratories, combined with contextual indicators such as population size, hospital activity, immunosuppression, and cancer incidence, we conducted an ecological analysis of annual aggregated data. The number of isolates from blood cultures increased from 10,964 in 2005 to 22,679 in 2024, or from 238.0 to 408.6 per 100,000 people, while the estimated blood culture positivity rate remained stable at approximately 6%. Escherichia coli , Staphylococcus aureus , and Klebsiella spp. were the most frequent pathogens in 2024, while the proportion of Streptococcus pneumoniae declined by nearly 40%. The apparent rise in the Gram-negative to Gram-positive ratio was largely explained by this decline in pneumococci. Regression models showed a steady increase in incidence of bacteraemia over time, with minimal impact of age adjustment. Increased diagnostic activity is probably driven by a larger share of inpatients meeting criteria for blood culture, consistent with a frailer and more complex case-mix. The relative stability of estimated positivity rate and the proportion of coagulase-negative staphylococci support that the rise reflects a real increase in the underlying burden of bloodstream infections.

Objectives We investigated the epidemiology and impact on mortality of antimicrobial resistance (AMR) in cancer patients with bacteraemia at Oxford University Hospitals (OxUH), UK, and Oslo University Hospital (OsUH), Norway, during 2008–2018. Design Historical cohort study. Setting Regional hospital trusts with multiple sites in OxUH and OsUH. Methods Patients with cancer and blood cultures positive for one of six pathogen groups during a hospital stay within 3 years following their first cancer diagnosis were followed for 30 days after their first bacteraemia episode. We determined the number of cases and the proportion of infections with an AMR phenotype. Excess mortality and the population-attributable fraction (PAF) due to AMR were estimated by contrasting observed mortality at the end of follow-up with an estimated counterfactual scenario where AMR was absent from all bacteraemias, using inverse probability weighting. Main outcome measure 30-day all-cause mortality following the first bacteraemia episode. Main exposure measure A resistant phenotype of the causative pathogen. Results The study included 1929 patients at OxUH and 1640 patients at OsUH. The highest resistance proportions were found for vancomycin resistance in enterococci (85/314, 27.1%) and carbapenem-resistance in Pseudomonas aeruginosa (63/260, 24.2%) at OxUH, and third-generation cephalosporin resistance in Escherichia coli (62/743, 8.3%) and Klebsiella pneumoniae (14/223, 6.3%) at OsUH. Observed mortality for all infections was 26.4% at OxUH, with an estimated counterfactual mortality without AMR of 24.7%, yielding an excess mortality of 1.7% (95% CI: 0.8 to 2.5%). The PAF was 6.3% (95% CI: 2.9 to 9.6%), meaning an estimated 32 of 509 deaths could be attributed to AMR. Limited events at OsUH precluded a similar estimate. Conclusions Despite estimating modest excess mortality, the mortality attributable to resistance in these two high-income, low-prevalence settings highlights the potential for escalation if global resistance trends continue to worsen.

Background: Candida auris is an emerging fungal pathogen that is often multidrug‐resistant. It can persist on skin and in hospital environments, leading to outbreaks and severe infections for patients at risk. Several countries and institutions are working on establishing guidelines and recommendations for prevention. This review aims to assess the evidence on factors associated with C. auris colonisation or infection, the duration of such colonisation, possible colonisation sites, and the risk of secondary cases to inform screening recommendations.Methods: We systematically searched five databases for primary studies and systematic reviews of our four outcomes. We excluded studies on treatment, management, laboratory methods, drug resistance, and environmental screening. From each paper, we extracted relevant data and summarised them in tables. Main findings were described narratively.Findings: We selected 117 studies for inclusion. Most of the studies were observational studies. Without taking the method of testing into account, the duration of C. auris colonisation varied, with up to and beyond a year being common. The predominant sites of colonisation were the axillae and groin, with the nares and rectum being less common sites. The risk of secondary cases saw considerable variation across the studies, and the secondary cases primarily involved patients and not healthcare workers. Critical care settings, invasive medical devices, recent antimicrobial use, and comorbidities were often associated with C. auris colonisation and infection.Conclusion: Our review highlights that, despite relevant findings on factors influencing C. auris colonisation and infection, substantial gaps remain in the evidence supporting screening practices. Most studies were conducted reactively, in outbreak settings, and lack systematic protocols. Given these limitations, screening guidelines are likely to be more successful if grounded in medical theory and yeast microbiology rather than relying solely on current studies. Rigorous, well‐designed research is urgently needed to inform future C. auris screening and control efforts.

Background: Candida auris is an emerging fungal pathogen that is often multidrug-resistant. It can persist on skin and in hospital environments, leading to outbreaks and severe infections for patients at risk. Several countries and institutions are working on establishing guidelines and recommendations for prevention. This review aims to assess the evidence on factors associated with C. auris colonisation or infection, the duration of such colonisation, possible colonisation sites, and the risk of secondary cases to inform screening recommendations. Methods: We systematically searched five databases for primary studies and systematic reviews of our four outcomes. We excluded studies on treatment, management, laboratory methods, drug resistance, and environmental screening. From each paper, we extracted relevant data and summarised them in tables. Main findings were described narratively. Findings: We selected 117 studies for inclusion. Most of the studies were observational studies. Without taking the method of testing into account, the duration of C. auris colonisation varied, with up to and beyond a year being common. The predominant sites of colonisation were the axillae and groin, with the nares and rectum being less common sites. The risk of secondary cases saw considerable variation across the studies, and the secondary cases primarily involved patients and not health care workers. Critical care settings, invasive medical devices, recent antimicrobial use, and comorbidities were often associated with C. auris colonisation and infection. Conclusion: Our review highlights that, despite relevant findings on factors influencing C. auris colonisation and infection, substantial gaps remain in the evidence supporting screening practices. Most studies were conducted reactively, in outbreak settings, and lack systematic protocols. Given these limitations, screening guidelines are likely to be more successful if grounded in medical theory and yeast microbiology rather than relying solely on current studies. Rigorous, well- designed research is urgently needed to inform future C. auris screening and control efforts.

Objectives: We investigated the epidemiology and impact on mortality of antimicrobial resistance (AMR) in cancer patients with bacteraemia at Oxford University Hospitals (OxUH), UK, and Oslo University Hospital (OsUH), Norway, during 2008-2018. Design: Historical cohort study. Setting: Regional hospital trusts with multiple sites in OxUH and OsUH. Methods: Patients with cancer and blood cultures positive for one of six pathogen groups during a hospital stay within three years following their first cancer diagnosis were followed for 30 days after their first bacteraemia episode. We determined the number of cases and the proportion of infections with an AMR phenotype. Excess mortality and the population-attributable fraction (PAF) due to AMR were estimated by contrasting observed mortality at the end of follow-up with an estimated counterfactual scenario where AMR was absent from all bacteraemias, using inverse probability weighting. Main outcome measure: 30-day all-cause mortality following the first bacteraemia episode. Main exposure measure: A resistant phenotype of the causative pathogen. Results: The study included 1929 patients at OxUH and 1640 patients at OsUH. The highest resistance proportions were found for vancomycin-resistance in enterococci (85/314, 27.1%) and carbapenem-resistance in Pseudomonas aeruginosa (63/260, 24.2%) at OxUH, and third-generation cephalosporin-resistance in Escherichia coli (62/743, 8.3%) and Klebsiella pneumoniae (14/223, 6.3%) at OsUH. Observed mortality for all infections was 26.4% at OxUH, with an estimated counterfactual mortality without AMR of 24.7%, yielding an excess mortality of 1.7% (95% CI: 0.8-2.5%). The PAF was 6.3% (95% CI: 2.9-9.6%), meaning an estimated 32 of 509 deaths could be attributed to AMR. Limited events at OsUH precluded a similar estimate. Conclusions: Despite estimating modest excess mortality, the mortality attributable to resistance in these two high-income, low-prevalence settings highlights the potential for escalation if global resistance trends continue to worsen.

Surveillance has revealed an increase of multidrug-resistant organisms (MDROs), even in low-prevalent settings such as Norway. MDROs pose a particular threat to at-risk populations, including persons with cancer. It is necessary to include such populations in future infection surveillance. By combining existing data sources, we aimed to describe the epidemiology of MDROs in persons diagnosed with cancer in Norway from 2008 to 2018. A cohort was established using data from the Cancer Registry of Norway, which was then linked to notifications of methicillin-resistant Staphylococcus aureus (MRSA), vancomycin- and/or linezolid-resistant enterococci (V/LRE), and carbapenemase-producing Gram-negative bacilli (CP-GNB) from the Norwegian Surveillance System for Communicable Diseases, and laboratory data on third-generation cephalosporin-resistant Enterobacterales (3GCR-E) from Oslo University Hospital (OUH). We described the incidence of MDROs and resistance proportion in Enterobacterales from 6 months prior to the person’s first cancer diagnosis and up to 3 years after. The cohort included 322,005 persons, of which 0.3% (878) were diagnosed with notifiable MDROs. Peak incidence rates per 100,000 person-years were 60.9 for MRSA, 97.2 for V/LRE, and 6.8 for CP-GNB. The proportion of 3GCR-E in Enterobacterales in blood or urine cultures at OUH was 6% (746/12,534). Despite overall low MDRO incidence, there was an unfavourable trend in the incidence and resistance proportion of Gram-negative bacteria. To address this, there is a need for effective infection control and surveillance. Our study demonstrated the feasibility of expanding the surveillance of MDROs and at-risk populations through the linkage of existing laboratory and register data.

Background: Infections are major causes of disease in cancer patients and pose a major obstacle to the success of cancer care. The global rise of antimicrobial resistance threatens to make these obstacles even greater and hinder continuing progress in cancer care. To prevent and handle such infections, better models of clinical outcomes building on current knowledge are needed. This internally funded systematic review (PROSPERO registration: CRD42021282769) aimed to review multivariable models of resistant infections/colonisations and corresponding mortality, what risk factors have been investigated, and with what methodological approaches. Methods: We employed two broad searches of antimicrobial resistance in cancer patients, using terms associated with antimicrobial resistance, in MEDLINE and Embase through Ovid, in addition to Cinahl through EBSCOhost and Web of Science Core Collection. Primary, observational studies in English from January 2015 to November 2021 on human cancer patients that explicitly modelled infection/colonisation or mortality associated with antimicrobial resistance in a multivariable model were included. We extracted data on the study populations and their malignancies, risk factors, microbial aetiology, and methods for variable selection, and assessed the risk of bias using the NHLBI Study Quality Assessment Tools. Results: Two searches yielded a total of 27,151 unique records, of which 144 studies were included after screening and reading. Of the outcomes studied, mortality was the most common (68/144, 47%). Forty-five per cent (65/144) of the studies focused on haemato-oncological patients, and 27% (39/144) studied several bacteria or fungi. Studies included a median of 200 patients and 46 events. One-hundred-and-three (72%) studies used a p-value-based variable selection. Studies included a median of seven variables in the final (and largest) model, which yielded a median of 7 events per variable. An in-depth example of vancomycin-resistant enterococci was reported. Conclusions: We found the current research to be heterogeneous in the approaches to studying this topic. Methodological choices resulting in very diverse models made it difficult or even impossible to draw statistical inferences and summarise what risk factors were of clinical relevance. The development and adherence to more standardised protocols that build on existing literature are urgent.

Background Infections are major causes of disease in cancer patients and pose a major obstacle to the success of cancer care. The global rise of antimicrobial resistance threatens to make these obstacles even greater and hinder continuing progress in cancer care. To prevent and handle such infections, a better understanding of the risk factors are needed. This internally funded systematic review (PROSPERO registration: CRD42021282769) aims to review what risk factors for resistant infections and deaths due to resistant infections have been investigated, and with what methodological approaches. Methods We employed two broad searches of antimicrobial resistance in cancer patients, using terms associated with antimicrobial resistant infections, in MEDLINE and Embase through Ovid, in addition to Cinahl through EBSCOhost and Web of Science Core Collection. Primary, observational studies in English from January 2015 to November 2021 on human cancer patients that explicitly modelled infection or mortality associated with antimicrobial resistance in a multivariable model were included. We extracted data on the study populations and their malignancies, risk factors, the microbial aetiology, methods for variable selection, and assessed the risk of bias using the NHLBI Study Quality Assessment Tools. Results Two searches yielded a total of 27151 unique records, of which 144 studies were included after screening and reading. Of the outcomes studied, mortality was the most common (68/144, 47%). Forty-five percent (65/144) of the studies focused on haemato-oncological patients, and 27% (39/144) studied several bacteria or fungi. Studies included a median of 200 patients and 46 events. One-hundred-and-three (72%) studies used a p-value-based variable selection. Studies included a median of seven variables in the final (and largest) model, which yielded a median of 6.9 events per variable. An in-depth example of vancomycin-resistant enterococci was reported. Conclusions We found the current research on this topic to be heterogeneous, in both the methodological and epidemiological approach. Methodological choices resulting in very diverse models made it difficult or even impossible to draw statistical inferences and summarise what risk factors were of clinical relevance. The development and adherence to more standardised protocols that build on existing literature is urgent.

Background Infections are major causes of disease in cancer patients and pose a major obstacle to the success of cancer care. The global rise of antimicrobial resistance threatens to make these obstacles even greater and hinder continuing progress in cancer care. To prevent and handle such infections, a better understanding of the risk factors are needed. This internally funded systematic review (PROSPERO registration: CRD42021282769) aims to review what risk factors for resistant infections and deaths due to resistant infections have been investigated, and with what methodological approaches. Methods We employed two broad searches of antimicrobial resistance in cancer patients, using terms associated with antimicrobial resistant infections, in MEDLINE and Embase through Ovid, in addition to Cinahl through EBSCOhost and Web of Science Core Collection. Primary, observational studies in English from January 2015 to November 2021 on human cancer patients that explicitly modelled infection or mortality associated with antimicrobial resistance in a multivariable model were included. We extracted data on the study populations and their malignancies, risk factors, the microbial aetiology, methods for variable selection, and assessed the risk of bias using the NHLBI Study Quality Assessment Tools. Results Two searches yielded a total of 27151 unique records, of which 144 studies were included after screening and reading. Of the outcomes studied, mortality was the most common (68/144, 47%). Forty-five percent (65/144) of the studies focused on haemato-oncological patients, and 27% (39/144) studied several bacteria or fungi. Studies included a median of 200 patients and 46 events. One-hundred-and-three (72%) studies used a p-value-based variable selection. Studies included a median of seven variables in the final (and largest) model, which yielded a median of 6.9 events per variable. An in-depth example of vancomycin-resistant enterococci was reported. Conclusions We found the current research on this topic to be heterogeneous, in both the methodological and epidemiological approach. Methodological choices resulting in very diverse models made it difficult or even impossible to draw statistical inferences and summarise what risk factors were of clinical relevance. The development and adherence to more standardised protocols that build on existing literature is urgent.