An outbreak of streptococcal pharyngitis has occurred in a remote village. In order to carry out the epidemiological investigations of the outbreak it is necessary to perform the culture of the throat swab of the patients suffering from the disease. The transport media of choice would be:
Streptococcal pharyngitis is caused by Group A Streptococcus (GAS), which is a fastidious organism. I remember that when transporting specimens, especially for fastidious organisms, the media needs to preserve the viability of the bacteria until they can be cultured.
Common transport media include Stuart's medium, Amies medium, and others. Amies is often used for specimens that need to be transported for a longer time because it has a buffer and a preservative. Stuart's medium is another option, but I think it's more for anaerobic bacteria. However, for throat swabs, which are usually aerobic, Amies might be better.
Wait, but sometimes they use selective media like blood agar for culturing, but the question is about transport media. So the correct answer is probably Amies. Let me check: Amies medium is recommended for transporting specimens like throat swabs for respiratory pathogens, including streptococci. It prevents drying and contamination, maintaining the bacteria's viability during transport.
The other options might be incorrect because, for example, some media are for specific organisms like anaerobes or viruses. If one of the options is a selective culture media like blood agar, that's not transport media. Also, Stuart's medium might not be ideal for aerobic organisms. So the key is to choose the transport media that best preserves the specimen for the specific pathogen in question here, which is GAS.
**Core Concept**
Transport media are designed to maintain the viability and purity of clinical specimens during transit to the lab. For *Streptococcus pyogenes* (Group A Streptococcus), a fastidious organism, the medium must prevent desiccation and inhibit overgrowth of contaminants while preserving bacterial integrity.
**Why the Correct Answer is Right**
**Amies medium** is the transport medium of choice for throat swabs in this scenario. It contains a buffer (glucose) and a preservative (thimerosal) to maintain pH and prevent microbial overgrowth. Its isotonic saline base prevents cell lysis, and the gelatinous matrix keeps the specimen moist. This ensures optimal recovery of *S. pyogenes* during transit, especially in remote settings where delayed processing is likely.
**Why Each Wrong Option is Incorrect**
**Option A:** *Stuart’s medium* is suitable for anaerobic organisms like *Clostridium* but not for aerobic streptococci. It lacks buffering capacity, risking pH shifts that kill *S. pyogenes*.
**Option B:** *Saline without preservatives* fails to inhibit contaminants and allows rapid bacterial death due to desiccation.
**Option C:** *Blood agar* is a *culture* medium, not transport media. It supports growth but not preservation during transit.
**Clinical Pearl / High-Yield Fact**
Remember: **"Amies for airway, Stuart for anaerobe"**. Amies is ideal for respiratory specimens (e.g., throat swabs, sputum) for aerobic pathogens like *S. pyogenes