Is Shigella sonnei pathogenic?

Is Shigella sonnei Pathogenic?

Yes, Shigella sonnei is definitively pathogenic and is a major cause of infectious diarrhea globally, capable of causing shigellosis characterized by bloody diarrhea, fever, and abdominal pain. 1, 2

Pathogenicity and Disease Characteristics

• Shigella sonnei is an emerging pathogen globally, being the second most common cause of shigellosis in low- and middle-income countries and the leading cause in developed countries 2
• It causes proctocolitis, which is associated with symptoms of proctitis, diarrhea, abdominal cramps, and inflammation of the colonic mucosa 1
• Shigella sonnei is transmitted through the fecal-oral route via contaminated food, water, or direct person-to-person contact 3
• The bacteria can be transmitted with low inocula, resulting in secondary transmission, contributing to its significant disease burden 1

Clinical Manifestations

Shigella sonnei infection can present in three major clinical syndromes:

• Self-limited gastroenteritis 1
• More severe and prolonged diarrheal disease with fever, bloody diarrhea, weight loss, and possible bacteremia 1
• Septicemia, which can exhibit extra-intestinal involvement with or without concurrent or preceding gastrointestinal illness 1

Risk Factors and High-Risk Populations

• Crowded living conditions such as refugee camps and institutional settings increase the risk of transmission 3
• Children in childcare settings are at higher risk due to close contact and developing hygiene practices 3
• Travelers to endemic areas face increased risk of infection 3
• Sexual transmission can occur through oral-anal contact, particularly among men who have sex with men (MSM) 3, 4
• Immunocompromised individuals are at higher risk for more severe illness and complications 1

Diagnostic Considerations

• Stool testing should be performed for Shigella in people with diarrhea accompanied by fever, bloody or mucoid stools, severe abdominal cramping or tenderness, or signs of sepsis 1
• Blood cultures should be obtained from infants <3 months of age, people with signs of septicemia, and immunocompromised individuals 1
• Diagnostic approaches that detect Shiga toxin (or the genes that encode them) should be applied when clinical or epidemic history suggests a possible Shiga toxin-producing organism 1

Treatment and Antimicrobial Resistance

• Ciprofloxacin is FDA-approved for treating infectious diarrhea caused by Shigella sonnei 5
• However, increasing antimicrobial resistance is a significant concern, with studies showing resistance to ciprofloxacin and fluoroquinolones 2, 4
• In Bangladesh, studies have shown high resistance rates to nalidixic acid (>60%), sulfamethoxazole-trimethoprim (89%), and ampicillin (9.5%) 6
• Recent outbreaks of extensively drug-resistant S. sonnei have been reported internationally, particularly among MSM populations 4

Prevention Strategies

• Proper handwashing with soap and water, especially after using the toilet and before handling food, is essential 3
• Access to clean drinking water and proper sewage disposal is crucial in preventing outbreaks 3
• Isolation of infected individuals is particularly important in institutional settings to prevent outbreaks 3
• Food handlers and healthcare workers with confirmed Shigella infection should have two consecutive negative stool samples taken 24 hours apart and at least 48 hours after resolution of symptoms before returning to work 1

Microbiome Interactions

• Studies show that Shigella sonnei infection decreases alpha diversity in the gut microbiome, with greater perturbations in individuals who develop shigellosis 7
• Individuals who develop shigellosis show persistent changes in their microbiomes after recovery, including a decrease in beneficial bacteria like Faecalibacterium 7
• Those who don't develop shigellosis tend to have greater abundance of taxa associated with short-chain fatty acid production, suggesting potential protective factors 7

Shigella sonnei's pathogenicity is well-established, with its ability to cause significant morbidity through various mechanisms, including its virulence factors, low infectious dose, and increasing antimicrobial resistance. Public health surveillance and control measures are essential to limit its spread and impact.