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- Salmonella spp. isolates in Portugal, 2024Publication . Silveira, Leonor; Caeiro, Raquel; Henriques, Ana Margarida; Tomás, Alexandra; Pista, ÂngelaBackground: Salmonella spp. remains one of the main causes of gastrointestinal infections in the European Union, only preceded by Campylobacter spp. The most common serovars of Salmonella spp. causing illness are Salmonella enterica enterica serovar Enteritidis, Typhimurium and the monophasic variant of Typhimurium (4,[5]:i:-). The aim of this study was to evaluate the Salmonella spp. isolates circulating in Portugal in 2024, accounting the number of cases, evaluating the available epidemiological data, and analysing the phenotypic and genotypic data gathered. Methods: The National Reference Laboratory received isolates from public and private hospitals and laboratories across Portugal for serotyping using the Kauffman-White-Le Minor scheme. Isolates were also subjected to antimicrobial susceptibility testing (AST) according to EUCAST recommendations, by the disc diffusion method for 18 antibiotics. Genomes of Salmonella isolates of serovars of interest were sequenced, either on a Miseq or Nextseq Illumina platform, and raw reads were submitted to Enterobase and to several CGE tools. Results: In 2024, a total of 873 isolates were received corresponding to an increase of approximately 40%, comparing to the previous year. Most cases belonged to children (n=409; 46.8%) and in residents of Lisbon and Tagus Valley (25.3%). The most common serotypes were S. monophasic Typhimurium (32.2%; n=281), S. Enteritidis (27.4%; n=281), and S. Typhiumurium (17.3%; n=151). In total, 510 isolates (58.4%) were resistant to at least one antibiotic tested. Multi-drug resistance was observed in 20.3% (177/873) of isolates, with the most common MDR serovars being S. Typhimurium (n=98; 55.4%) and its monophasic variant (n=55; 31.1%). Four isolates were ESBL producers, presenting blaDHA-1, blaCTX-M-65, blaCTX-M -9, and blaOXA-1, and one was also a carbapenemase producer, presenting both blaOXA-1 and blaOXA -48. WGS revealed several clusters, namely among the top three serovars. Conclusions: The considerable increase in cases was intrinsically connected to several clusters of the most frequent serovars, most specially of MDR isolates. To our knowledge, this was the first time a carbapenemase producer Salmonella, isolated from a human clinical sample, was detected in Portugal. Salmonella continued laboratory surveillance and antimicrobial resistance monitoring are essential for disease prevention and control.
- Antimicrobial resistance of Salmonella Typhi and Paratyphi isolates in Portugal, January 1994 - June 2025Publication . Pista, Ângela; Henriques, Ana Margarida; Caeiro, Raquel; Tomás, Alexandra; Silveira, LeonorIntrodution: Typhoid and paratyphoid fever are severe systemic infections caused by Salmonella (S.) enterica subspecies enterica serovars Typhi and Paratyphi A, B and C. Transmission occurs primarily through ingestion of food or water contamined with faeces from infected individuals or via direct person-to person contact. In Europe, enteric fever is rare and mainly associated with travel to endemic countries. The increasing prevalence of multidrug resistance (MDR), particularly in S. Typhi, poses significant therapeutic challenges. Aim: Characterization of antibiotic resistance profiles of S. Typhi and Paratyphi A, B, and C isolates received in Jan 94-Jun 25