Shigella boydii

1. What is Shigella boydii

Figure 51.1. Colony morphology of four Shigella species cultured on different media for 24 h. (i) Columbia blood agar plate; (ii) MacConkey agar plate; and (iii) Salmonella-Shigella agar medium.

Shigella boydii is a Gram-negative, non-motile, non-spore-forming, rod-shaped bacterium belonging to the genus Shigella. It is one of the four species of Shigella, which are known to cause dysentery in humans¹.

2. Transmission of Shigella boydii

Shigella boydii is primarily transmitted through the fecal-oral route. This can occur via:

• Contaminated food and water
• Direct person-to-person contact
• Contact with contaminated surfaces or objects²

3. Epidemiology of Shigella boydii

Shigella boydii is mainly found in the Indian subcontinent and is less common in other parts of the world. It is responsible for causing shigellosis, a type of dysentery¹.

4. Pathology, Disease, and Infection Caused by Shigella boydii

Shigella boydii causes shigellosis, which is characterized by:

• Diarrhea (which can be bloody)
• Fever
• Stomach cramps
• Tenesmus (a feeling of needing to pass stools even when the bowels are empty)

The infection can lead to severe dehydration and complications, especially in young children and the elderly².

5. Laboratory Tests for Shigella boydii

• Gram Stain: Gram-negative
• Cell Shape: Rod-shaped (bacilli)
• Cell Arrangement: Single or in pairs
• Culture Media: Grows on MacConkey agar, Hektoen enteric agar, and XLD agar
• Selective Culture Media: Hektoen enteric agar, XLD agar
• Biochemical Tests:
• Indole negative
• Urease negative
• Lactose non-fermenter
• Hydrogen sulfide negative¹

6. List of Specimen Types for Shigella boydii

• Stool samples
• Rectal swabs²

7. List of Specimen Collection Sites

• Rectum (via rectal swabs)
• Feces (stool samples)²

8. Colony Morphology of Shigella boydii

• Edge: Entire (smooth and even)
• Elevation: Low convex
• Surface: Smooth
• Size: Small to medium-sized colonies (1-2 mm in diameter after 24 hours of incubation)
• Form: Circular
• Opacity: Translucent to semi-opaque
• Colour: Pale or colorless on MacConkey agar (non-lactose fermenting)
• Consistency: Moist
• Effect on the media: Does not cause significant changes, no hemolysis on blood agar
• Pigment: Non-pigmented (no pigment production)

If you have any more questions or need further details, feel free to ask!

Learn more

1en.wikipedia.org2cdc.gov3vi.wikipedia.org4microbewiki.kenyon.edu5en.wikipedia.org

 

9. The treatment guidelines 

The treatment guidelines for Shigella flexneri focus on managing symptoms, preventing dehydration, and using antibiotics in severe cases. Here are the key points:

General Management

1. Hydration: Ensure adequate fluid intake to prevent dehydration. Oral rehydration solutions (ORS) are recommended, especially for children¹.
2. Avoid Anti-diarrheal Medications: Do not use anti-diarrheal medicines like loperamide (Imodium) or diphenoxylate with atropine (Lomotil) as they can worsen symptoms¹.

Antibiotic Treatment

• Mild Cases: Often resolve without antibiotics within 5 to 7 days¹.
• Severe Cases: Antibiotics may be prescribed to shorten the duration of illness and reduce bacterial shedding. Commonly used antibiotics include:
  • Ciprofloxacin
  • Azithromycin
  • Ceftriaxone (for multi-resistant strains)¹²

Special Considerations

• Children and Immunocompromised Individuals: More likely to require antibiotics due to higher risk of complications¹.
• Empirical Treatment: In areas with high resistance, empirical treatment may be guided by local antibiotic susceptibility patterns².

Monitoring and Follow-up

• Symptom Monitoring: If symptoms persist or worsen, further medical evaluation is necessary.
• Antibiotic Resistance: Laboratory tests can help determine the most effective antibiotic if initial treatment fails¹.

For more detailed guidelines, you can refer to the CDC and Médecins Sans Frontières resources.

If you have any more questions or need further details, feel free to ask!

Learn more

1cdc.gov2tandfonline.com3uptodate.com4bestpractice.bmj.com

10. Antimicrobial Susceptibility Testing (AST) for Shigella flexneri 

Antimicrobial Susceptibility Testing (AST) for Shigella flexneri is crucial for guiding effective treatment, especially given the rising concern of antibiotic resistance. Here are the key points:

Commonly Tested Antibiotics

• Azithromycin
• Ciprofloxacin
• Ceftriaxone
• Trimethoprim-sulfamethoxazole (TMP-SMX)
• Ampicillin¹²

Resistance Patterns

• Multidrug-resistant (MDR) Shigella: Resistant to three or more of the five established antibiotics¹.
• Extensively drug-resistant (XDR) Shigella: Resistant to all five established antibiotics¹.

Testing Methods

• Disk Diffusion: Measures the inhibition zone around antibiotic disks placed on an agar plate inoculated with the bacteria³.
• Etest: Uses a gradient method to determine the minimum inhibitory concentration (MIC) of antibiotics³.
• Vitek 2: An automated system that provides rapid AST results³.

Recommendations

• Empirical Treatment: Should be guided by local resistance patterns and adjusted based on AST results².
• Culture and Sensitivity Testing: Essential for accurate diagnosis and effective treatment⁴.

Emerging Resistance

• Increasing resistance to azithromycin and ciprofloxacin has been reported²⁵.
• Continuous monitoring and updating of treatment guidelines are necessary to address these changes⁵.

If you need more detailed information or have specific questions, feel free to ask!

Learn more

1publichealthontario.ca2cdc.gov3frontiersin.org4emergency.cdc.gov5academic.oup.com6academic.oup.com7publichealth.lacounty.gov8annalsmicrobiology.biomedcentral.com9doi.org10doi.org