Cluster of cases due to Shigella flexneri producing CTX-M-15 in Spain

Area of Science:

• Microbiology
• Epidemiology
• Infectious Diseases

Background:

• Gastroenteritis outbreaks pose a significant public health challenge.
• Shigella flexneri is a common cause of bacterial dysentery.
• The emergence of antibiotic-resistant strains necessitates ongoing surveillance.

Purpose of the Study:

• To investigate an outbreak of gastroenteritis in Bilbao, Spain, caused by Shigella flexneri.
• To characterize the antibiotic resistance profile and genetic elements of the outbreak strains.
• To identify the source and transmission route of the infection.

Main Methods:

• Clinical case analysis and epidemiological investigation.
• Microbiological culture and identification of Shigella flexneri.
• Antimicrobial susceptibility testing (minimum inhibitory concentrations).
• Molecular techniques including PCR, serotyping, pulsed-field gel electrophoresis (PFGE), and plasmid analysis.

Main Results:

• Sixteen individuals were affected by Shigella flexneri gastroenteritis linked to a single kebab shop.
• All isolates were identified as serotype 2 and produced extended-spectrum beta-lactamase (ESBL).
• The strains harbored blaCTX-M-15 and blaOXA-1 genes, conferring resistance to certain antibiotics, but remained susceptible to carbapenems, fluoroquinolones, tigecycline, colistin, and co-trimoxazole.
• PFGE confirmed a single source outbreak, and plasmid analysis revealed blaCTX-M-15 on a 230 kb plasmid.

Conclusions:

• This represents the first reported outbreak of CTX-M-15-producing Shigella flexneri in Spain and Europe.
• The findings highlight the importance of food safety and surveillance for antibiotic-resistant pathogens.
• Travel history of a food handler to Pakistan suggests a potential link to international spread of resistant strains.