Which of the following tests identifies the presence of bacteria in a sample?

A culture test is specifically designed to identify the presence of bacteria by allowing them to grow in a controlled environment, usually through the use of petri dishes and nutrient media. When a sample suspected of containing bacteria is introduced into the culture, the bacteria can multiply, enabling further analysis and identification based on their characteristics.

The Gram stain, while primarily a method for classifying bacteria based on their cell wall structure, also allows for the visualization of bacteria under a microscope. By applying certain reagents, the Gram stain indicates whether the bacteria are Gram-positive or Gram-negative, which can provide critical information about the type of bacteria that may be present.

Since both the culture test and the Gram stain provide information about the presence of bacteria, the correct answer encompasses the capabilities of both tests, indicating that both methods are relevant for identifying bacteria in a sample. Therefore, the choice that includes both options is accurate in reflecting the methods used for diagnosing bacterial infections.