Eurosurveillance - Volume 29, Issue 49, 05 December 2024

Since April 2024, a pertussis epidemic has been ongoing in Finland with 2,215 notified cases by end October. Of them, 30.1% (n = 667) were aged 10–14 years. Of the 462 Bordetella pertussis isolates characterised, one was macrolide-resistant (minimum inhibitory concentration (MIC) of erythromycin, azithromycin and clarithromycin > 256 μg/mL). The resistant isolate was serotype FIM2, vaccine antigen pertactin-deficient and harboured ptxP3 allele. The emergence of macrolide-resistant B. pertussis in Europe is worrisome and its rapid identification is important.

In 2016–2019, hospital A’s haematology ward experienced an outbreak of OXA-48-producing ST-22 Citrobacter freundii strains, with toilets identified as source of transmission. Between 2020 and 2022, 28 strains of OXA-48-producing ST-22 C. freundii were isolated on other wards. This study aimed to determine whether all OXA-48-producing ST-22 C. freundii strains belonged to the same clone and to investigate the persistence of this clone using whole genome sequencing. OXA-48-producing ST-22 C. freundii strains collected from patients (n = 33) and from the hospital environment (n = 20) of seven wards were sequenced using Illumina technology and clonal relationships were determined using single nucleotide polymorphism (SNP). Phylogenetic analyses were performed on 53 strains from hospital A and on 240 epidemiologically unrelated carbapenem-resistant ST-22 C. freundii isolated from elsewhere in France. SNP analysis suggested long-lasting persistence of the same clone for more than 6 years. Phylogenetic analysis showed that 52 of 53 strains isolated in hospital A belonged to the same cluster and were different from the 240 epidemiologically unrelated C. freundii ST-22. Our data suggest that this clone can persist in hospital environments for years, representing a risk for hospital-acquired infections and outbreaks. Reservoir management is essential to prevent further transmission.

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathogen associated with illness ranging from mild diarrhoea to haemolytic uremic syndrome (HUS) or even death. Cross-sectoral data sharing provides an opportunity to gain insight in reservoirs and sources of human infections and starting points for pro-active measures. Nevertheless, phylogenetic clustering of STEC strains from animals, food and human cases is low in the Dutch surveillance system. This is partly due to the substantial contribution of international travel and person-to-person spread in the STEC epidemiology. Furthermore, some STEC strains causing disease in humans may have a human reservoir. Although the main reservoirs and sources are included in the Dutch monitoring programmes, some animals and food products may be under-recognised as potential sources of human infections. More effort in investigating the role of other reservoirs beyond the well-known can provide a better understanding on STEC ecology in general, improving surveillance and source attribution, and ultimately provide better guidance for monitoring and source finding. This also implies having good diagnostics in place and isolates available for typing. Therefore, on the human side of the surveillance, the decision has been made to start isolating STEC at national level.