Salmonella enteritidis
1. What is Salmonella enteritidis
Salmonella enteritidis is a serotype of the bacterium Salmonella enterica. It is a common cause of foodborne illness, often resulting in gastroenteritis in humans. This bacterium typically resides in the intestines of animals and humans and is shed through feces1.
2. Transmission of Salmonella enteritidis
Transmission primarily occurs through the consumption of contaminated food or water. Common sources include raw or undercooked meat, poultry, eggs, and unpasteurized milk. Person-to-person transmission can also occur via the fecal-oral route2.
3. Epidemiology of Salmonella enteritidis
Salmonella enteritidis is one of the most frequently reported serotypes causing human salmonellosis globally. It accounts for a significant number of foodborne illnesses each year. In the United States alone, it causes about 1.35 million infections annually34.
4. Pathology, Disease, and Infection Caused by Salmonella enteritidis
Infection with Salmonella enteritidis typically leads to gastroenteritis, characterized by symptoms such as diarrhea, abdominal cramps, fever, nausea, and vomiting. In severe cases, it can cause dehydration and may spread beyond the intestines, leading to more serious conditions15.
5. Laboratory Tests for Salmonella enteritidis
- Gram Stain: Gram-negative rods.
- Cell Shape: Rod-shaped.
- Cell Arrangement: Single or in pairs.
- Culture Media: Grows on standard media like MacConkey agar, producing colorless colonies.
- Selective Culture Media: XLD agar, Hektoen enteric agar.
- Biochemical Tests: Positive for H2S production, lysine decarboxylase, and citrate utilization; negative for lactose fermentation67.
6. List of Specimen Types for Salmonella enteritidis
Specimens for testing can include stool, blood, urine, and other body tissues or fluids8.
7. List of Sites for Specimen Collection for Salmonella enteritidis Isolation
Common sites for specimen collection include:
- Stool: For detecting gastrointestinal infections.
- Blood: For detecting systemic infections.
- Urine: In cases where the infection has spread to the urinary tract9.
8. Colony Morphology of Salmonella enteritidis
- Edge: Smooth.
- Elevation: Raised.
- Surface: Smooth.
- Size: Medium-sized colonies.
- Form: Circular.
- Opacity: Opaque.
- Colour: Colorless to pale.
- Consistency: Moist.
- Effect on the Media: May produce black centers on Hektoen enteric agar due to H2S production.
- Pigment: None1011.
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9. Treatment Guidelines for Salmonella enteritidis
1. General Management:
- Hydration: Ensure adequate fluid and electrolyte replacement to prevent dehydration, especially in cases of severe diarrhea1.
- Diet: Maintain a bland diet and avoid dairy products, caffeine, and alcohol until symptoms improve.
2. Antibiotic Therapy:
- Indications for Antibiotics: Antibiotics are generally reserved for severe cases, those with a weakened immune system, infants, elderly patients, or when the infection spreads beyond the intestines12.
- Common Antibiotics Used: Ciprofloxacin, azithromycin, and ceftriaxone are commonly prescribed1.
3. Hospitalization:
- Criteria for Hospitalization: Patients with severe dehydration, persistent high fever, or systemic infection may require hospitalization for intravenous fluids and antibiotics1.
4. Symptomatic Relief:
- Antipyretics: Use of medications like acetaminophen to reduce fever.
- Antidiarrheal Agents: Generally not recommended as they can prolong the infection by slowing down the elimination of bacteria from the intestines3.
5. Preventive Measures:
- Hygiene: Emphasize proper handwashing, especially after using the bathroom and before handling food.
- Food Safety: Ensure thorough cooking of meat, poultry, and eggs, and avoid consuming unpasteurized milk or products made from it1.
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1. Purpose of AST: Antimicrobial Susceptibility Testing (AST) is crucial for determining the effectiveness of antibiotics against Salmonella enteritidis. It helps guide appropriate antibiotic therapy and monitor resistance patterns1.
2. Common Methods:
- Disk Diffusion Method (Kirby-Bauer Test): This involves placing antibiotic-impregnated disks on an agar plate inoculated with the bacteria. The zones of inhibition around the disks are measured to determine susceptibility2.
- Broth Microdilution: This method tests various concentrations of antibiotics in a liquid medium to find the minimum inhibitory concentration (MIC) that prevents bacterial growth3.
- Agar Dilution: Similar to broth microdilution but performed on solid media1.
3. Interpretation Standards:
- Clinical and Laboratory Standards Institute (CLSI): Provides guidelines for interpreting AST results, categorizing bacteria as susceptible, intermediate, or resistant based on the size of inhibition zones or MIC values2.
4. Commonly Tested Antibiotics:
- Fluoroquinolones (e.g., Ciprofloxacin)
- Third-generation Cephalosporins (e.g., Ceftriaxone)
- Macrolides (e.g., Azithromycin)
- Aminoglycosides (e.g., Gentamicin)
- Sulfonamides (e.g., Trimethoprim/Sulfamethoxazole)4.
5. Resistance Patterns:
- Salmonella enteritidis has shown resistance to several antibiotics, including ampicillin and trimethoprim/sulfamethoxazole. Multidrug-resistant (MDR) strains are also emerging4.
6. Importance of AST:
- Guiding Treatment: Ensures the use of effective antibiotics, reducing the risk of treatment failure.
- Monitoring Resistance: Helps track the development of antibiotic resistance, informing public health strategies5.
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