Name two pus-forming bacteria commonly identified in infections.

• A. Staphylococci and Streptococci
• B. Escherichia coli and Salmonella
• C. Mycobacterium and Pseudomonas
• D. Bacillus and Clostridium

Answer: (A)

The main idea here is identifying pus-forming (pyogenic) bacteria. In most infections that produce noticeable pus, the common culprits are the staphylococci and the streptococci. These bacteria—staphylococcus species like Staphylococcus aureus, and various Streptococcus species—tend to trigger a strong neutrophilic inflammatory response that results in pus, the thick, yellowish or white material made up of dead white blood cells, bacteria, and tissue debris. They’re classic agents in skin infections, abscesses, boils, impetigo, and wound infections, where pus is a common feature.

Other pairs don’t fit this common pattern as neatly. Enteric bacteria like Escherichia coli and Salmonella are mainly linked to gastrointestinal and systemic infections rather than the textbook pus-forming skin infections. Mycobacterium and Pseudomonas can cause purulent infections in some contexts, but Mycobacterium tends to form granulomas with less pus, and the combination isn’t the standard pairing taught for pus-forming bacteria. Bacillus and Clostridium include organisms that can cause foul discharge in certain severe conditions, but they’re not the classic duo described for widespread pus formation in typical infections.

So, the best-known pus-forming pair in infections is the combination of staphylococci and streptococci.