8 Resistance in human pathogens

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Report Highlights 2023:

Resistance in human pathogens

Invasive infections. After years of increasing invasive infections, the numbers stagnated with a total of 12,205 cases. However, invasive infections with Klebsiella pneumoniae (1,399 cases) and Staphylococcus aureus (2,559 cases) continued to rise. Invasive infections with Streptococcus pneumoniae (602 cases) saw a steep decline after the introduction of vaccinations for young children and during the COVID-19 pandemic, but have since risen to near pre-pandemic levels.

Escherichia coli. Resistance levels have generally been stable over the past decade. However, resistance to piperacillin/tazobactam in invasive infections climbed from 4.8% in 2014 to 6.3% in 2023 for Denmark as a whole. These increases were driven by rising trends in the Capital Region, Region Zealand and the Central Denmark Region, whereas the North Denmark Region had a decreasing trend. Combined resistance to 3rd generation cephalosporins, ciprofloxacin and gentamicin remained low at 1.2%. Combined resistance to ampicillin and gentamicin was at 4.1% in 2023, decreasing from 6.9% in 2014. Carbapenem-resistance remained below 1% with no noticeable trend.

Klebsiella pneumoniae. While resistance levels have been decreasing for the past decade, piperacillin/tazobactam-resistance in invasive infection in 2023 surpassed 10% for Denmark as a whole and in four out of five regions. Combined resistance to 3rd generation cephalosporins, ciprofloxacin and gentamicin increased from 1.1% in 2015 to 1.9% in 2023. Additionally, cefuroxime-resistance increased from 7.7% to 9.8% from 2022 to 2023. The rising resistance coupled with an increase in invasive infections with K. pneumoniae warrants increased efforts to curb the development.

Carbapenemase-producing organisms/Enterobacterales (CPO/CPE). CPE were increasingly spreading in Danish hospitals, with cases rising 43% from 2022 to 2023, reaching 436 individual cases. CPE, historically linked to travel, are now increasingly found domestically. CPE outbreaks increased in hospitals despite extensive screening and cleaning efforts. 138 new CPO patients were associated with outbreaks in Denmark in 2023. Although bloodstream infections remained rare, the rise in hospital-acquired CPE indicates the emergence of domestic reservoirs. For non-outbreak related cases, 86 patients reported travelling outside Nordic countries, however, the number of cases with no travel information reported was high (130 cases). Additionally, 36 cases were patients from Ukraine.

Staphylococcus aureus. The number of S. aureus bacteraemia cases was 2,571 in 2023 and at the same level as in 2022. Of these, 39 cases (1.5%) were caused by methicillinresistant S. aureus (MRSA) with nine being livestock-associated-MRSA (LA-MRSA). Resistance to penicillin continued to decrease and was 68% in 2023. There were 3,649 cases of MRSA from both screening (45% of cases) and infections (55%), which was a 20% increase compared to 2022. Forty-one MRSA outbreaks were registered at hospitals, nursing homes and other institutions for a total of 199 cases with 80 being infections.

Neisseria gonorrhoeae. Over the decade the number of received isolates and of reported cases increased significantly. In 2023, the reference laboratory at SSI received 2,653 isolates from 2,152 unique cases. Ciprofloxacin resistance was at 45%. Azithromycin-resistance was found in 6% of tested isolates in 2023 compared to 2.9% of tested isolates in 2022.