Journal of Bioterrorism & Biodefense
Open Access

Shigella; Shigellosis; Dysentery; Diarrheal disease; Antimicrobial resistance; Pathogenesis; Vaccine development

Introduction

Shigella is a leading cause of bacterial diarrhea, responsible for an estimated 80–165 million cases and over 200,000 deaths globally each year [1]. The disease is especially prevalent in low-income settings with poor sanitation and limited clean water access. The genus comprises four major species: S. dysenteriae, S. flexneri, S. boydii, and S. sonnei, with varying geographical and epidemiological significance.

Despite its global burden, shigellosis is often underreported, as many cases go unconfirmed in laboratories, particularly in resource-limited settings [2]. This review consolidates current insights into the microbiology, pathogenesis, clinical presentation, diagnosis, management, and control strategies for Shigella infections.

Microbiology and classification

Shigella species are non-spore-forming, non-motile bacilli belonging to the family Enterobacteriaceae. The four species include:

• S. dysenteriae (Group A)
• S. flexneri (Group B)
• S. boydii (Group C)
• S. sonnei (Group D)

Each species has multiple serotypes; S. flexneri predominates in low-income countries, while S. sonnei is more common in industrialized nations [3].

Epidemiology

Shigellosis disproportionately affects children under five and is common in regions of Africa, Asia, and Latin America. Transmission occurs through direct contact with infected individuals or via contaminated food, water, and surfaces. Outbreaks are common in crowded conditions like refugee camps, schools, and childcare centers [4].

Pathogenesis

Infection begins with ingestion of as few as 10–100 organisms. Shigella invades the colonic mucosa, primarily through M cells, leading to macrophage apoptosis and intense inflammation. The Type III secretion system encoded on the virulence plasmid (pINV) facilitates this invasion. Some strains, notably S. dysenteriae type 1, produce Shiga toxin, which inhibits protein synthesis and can lead to hemolytic uremic syndrome (HUS) [5].

Clinical manifestations

Symptoms typically arise 1–3 days post-infection and include:

• Profuse watery diarrhea, often progressing to dysentery
• Fever and abdominal cramps
• Tenesmus
• Stool with blood and mucus

Complications such as dehydration, seizures (in children), toxic megacolon, and HUS may occur, particularly in severe cases [6].

Diagnosis

Stool culture remains the gold standard for diagnosis and antimicrobial susceptibility testing. However, PCR and antigen-based rapid diagnostics are increasingly used for timely identification, especially during outbreaks [7].

Treatment

Most cases are self-limiting, but moderate to severe infections benefit from antimicrobial therapy to reduce illness duration and transmission. Recommended antibiotics include:

• Ciprofloxacin
• Azithromycin
• Ceftriaxone

Resistance to first-line antibiotics like fluoroquinolones and macrolides is rising, complicating treatment choices [8].

Prevention and control

Control measures involve:

• Improved sanitation and water access
• Hand hygiene promotion
• Safe food practices
• Public health education
• Surveillance systems

No vaccine is currently licensed, though several live attenuated and inactivated whole-cell candidates are in clinical trials [9].

Results

Surveillance reports from Asia and Africa reveal growing trends of multidrug-resistant S. flexneri and S. sonnei strains, with reduced susceptibility to azithromycin and ciprofloxacin. Point-of-use water treatment and hygiene interventions have demonstrated efficacy in reducing disease incidence in outbreak settings. Several vaccine platforms—including live attenuated oral vaccines and conjugate polysaccharide vaccines—are under investigation, with promising results in early-phase clinical trials but limited cross-serotype coverage and durability [10].

Discussion

The persistence of shigellosis reflects inequities in global health infrastructure. Antimicrobial resistance adds urgency to developing novel treatment approaches and effective vaccines. Investment in water, sanitation, and hygiene (WASH) infrastructure remains a cornerstone of prevention. Coordinated surveillance and stewardship programs are critical to address antibiotic resistance and support rational prescribing [10].

Conclusion

Shigellosis continues to burden global health, especially in vulnerable populations. While preventive strategies and diagnostic advancements offer hope, antibiotic resistance and the absence of an effective vaccine highlight the need for sustained research and global cooperation.