8 Resistance in human pathogens

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Report Highlights 2024:

Resistance in human pathogens

The incidence of positive blood cultures with pathogenic species increased overall from 474 per 100,000 inhabitants in 2015 to 612 per 100,000 inhabitants in 2024 (an increase of 29 %). The number of individual registered invasive cases per year for the decade increased for E. coli from 4,597 cases to 5,957 cases, for S. aureus from 1,876 to 2,442 cases, for K. pneumoniae from 939 to 1,457 cases and for P. aeruginosa from 441 to 488 cases. Decreasing numbers were observed for S. pneumoniae from 747 to 600 annual cases, for E. faecium from 693 to 584 cases and for E. faecalis from 610 to 594 cases.

Resistance levels for invasive E. coli showed decreasing or stagnating trends for most antimicrobials, including for combined resistance to ciprofloxacin, cephalosporin and gentamicin (2.3% in 2015 to 1.0% in 2024) and combined resistance to ampicillin and gentamicin (6.3% in 2015 to 4.0% in 2024). Resistance to piperacillin-tazobactam increased in three of the five healthcare regions, leading to an overall increase from 4.9% in 2015 to 6.5% in 2024. Resistance to carbapenems remained below 1%.

In invasive K. pneumoniae the resistance level for piperacillin/tazobactam has been increasing steadily since 2021 and has now reached 10.9% (7.5% in 2021). However, combined resistance to 3rd generation cephalosporins, ciprofloxacin and gentamicin remains low at 1.4 %. Additionally, resistance to carbapenem remained below 1%. For K. pneumoniae from hospital urine, resistance to piperacillin/tazobactam is now also at 10.9% mirroring the increasing resistance levels in invasive infections.

Carbapenemase-producing organisms/Enterobacterales (CPO/CPE). CPE were increasingly spreading in Danish hospitals, with cases increasing by 14% from 2023 to 2024, reaching 497 individual cases. CPE, historically linked to travel, are now increasingly found domestically. CPE outbreaks increased in hospitals despite extensive screening and cleaning efforts. 166 new CPO patients were associated with outbreaks in Denmark in 2024. Although bloodstream infections remained rare, the rise in hospital-acquired CPE indicates the emergence of domestic reservoirs. For non-outbreak related cases, 110 patients reported travelling outside Nordic countries, however, the number of cases with no travel information reported was high (256 cases). Additionally, 41 cases were patients from Ukraine.

Staphylococcus aureus. The number of S. aureus bacteraemia cases was 2,461 in 2024 and at the same level as in 2023. Of these, 47 cases (1.9%) were caused by methicillinresistant S. aureus (MRSA) with seven being livestock-associated-MRSA (LA-MRSA). Resistance to penicillin appears stable and was 68% in 2024. There were 3,372 cases of MRSA from both screening (41% of cases) and infections (59%), which was an 8% decrease compared to 2023. Thirty-eight MRSA outbreaks were registered at hospitals, nursing homes and other institutions for a total of 191 cases with 86 being infections.

Neiserria gonorrhoeae. Over the decade the number of received isolates and of reported cases increased significantly. In 2024, the reference laboratory at SSI received 1,852 isolates from 1,803 individual cases. Ciprofloxacin resistance was at 61%. Azithromycin-resistance was found in 3.5% of tested isolates in 2023 compared to 6.0% of tested isolates in 2022.