Background: Resistance to first-line antibiotics is on the rise globally which led WHO to include fluoroquinolone-resistance in Shigella among serious antimicrobial resistance (AMR) threats. In Europe, circulation of extensively resistant Shigella species was recently reported. However, little is known about the apparition and circulation of those isolates in Spain. Our study aimed to describe the epidemiology of fluoroquinolone-resistant S. sonnei and S. flexneri isolates in Spain from 2015 to 2022.

Methods: We selected 30% of all isolates received between January 2015 to July 2022 to be representative of time and place and studied antibiotic resistance by disc-diffusion methods. We obtained AMR profile for 116 and 164 S. flexneri and S. sonnei isolates, respectively. Isolates where considered fluoroquinolone-resistant if they showed resistance to one of the following antibiotics: ciprofloxacin, pefloxacin, or nalidixic acid. Epidemiological data were collected through petition forms filled by the hospitals.

Results: We observed a progressive increase in the percentage of fluoroquinolone-resistance isolates from 2015 to 2022, when 45% and 88% of S. flexneri and S. sonnei were fluoroquinolone-resistant, respectively. Isolates from men were more likely to be fluoroquinolone-resistant than isolates from women (OR=2.16 (1.21, 3.84)). Between 2019 and 2022, we also found an increase in multi-drug resistance (resistance to fluoroquinolone, β-lactams and cephalosporins) from 5% to 76% of S. sonnei isolates and from 4% to 18% of S. flexneri isolates.

Conclusion: Although Shigella species mostly causes self-limiting diarrhea, it can lead to severe symptoms in immunocompromised patients, so the circulation of resistant strains to both first and second line of treatment raises concerns about the clinical management of these cases. The spread of extensively resistant Shigella infection, unnoticed before 2021, highlights the need to strengthen surveillance of shigellosis in Spain. Further studies on risk groups are needed for targeted prevention and improved clinical and public health management.