From the Guidelines
Blood culture is the preferred diagnostic method for suspected enteric fever or invasive salmonellosis, as it has a sensitivity of approximately 50% compared to other methods. When diagnosing salmonella, the choice between blood culture and stool culture depends on the clinical presentation of the patient. For patients with symptoms of septicemia or suspected enteric fever, blood culture should be performed as the initial diagnostic assessment 1. This is because blood culture can detect bacteria that have invaded the bloodstream, which is crucial for diagnosing systemic Salmonella infections like typhoid fever.
Some key points to consider when deciding between blood and stool culture include:
- The sensitivity of blood culture for diagnosing enteric fever is approximately 50% compared to bone marrow culture 1
- Blood culture is recommended as the routine practical conventional diagnostic method for suspected enteric fever or invasive salmonellosis 1
- Stool culture may be helpful in diagnosing intestinal infection, but it is not the primary method for diagnosing systemic Salmonella infections
- The choice between blood and stool culture depends on the clinical presentation of the patient, with blood culture being more appropriate for patients with systemic symptoms and stool culture being more appropriate for patients with primarily gastrointestinal symptoms
In terms of the procedure for collecting blood cultures, two to three 20-mL blood cultures are adequate for detection of bacteremia in adults 1. It is essential to collect blood cultures prior to the administration of antimicrobial agents to maximize sensitivity. Continuously monitored blood culture systems may shorten the time to detection and improve sensitivity compared to manual blood culture methods. Blood cultures may be drawn simultaneously and should be collected prior to administration of antimicrobial agents to maximize sensitivity 1.
From the Research
Diagnosis of Salmonella Infections
- Blood culture and stool culture are two common methods used to diagnose Salmonella infections 2, 3
- Blood cultures are typically used to diagnose typhoidal Salmonella infections, while stool cultures are used to diagnose non-typhoidal Salmonella infections 2
- In some cases, urine cultures may also be used to diagnose Salmonella infections, particularly in patients with urinary tract infections 3
Choice of Diagnostic Test
- The choice of diagnostic test depends on the clinical presentation and suspected type of Salmonella infection 2, 3
- For patients with symptoms of gastroenteritis, a stool culture may be the preferred diagnostic test 2
- For patients with symptoms of typhoid fever or bacteremia, a blood culture may be the preferred diagnostic test 2, 3
Interpretation of Test Results
- A positive blood or stool culture confirms the diagnosis of a Salmonella infection 2, 3
- The results of the culture should be interpreted in conjunction with the patient's clinical presentation and medical history 2, 3
- In some cases, additional testing such as antibiotic susceptibility testing may be necessary to guide treatment decisions 4, 5