Microbiology Practice Exam

Which type of bacteria is associated with endotoxin?

1. Gram positive

2. Gram negative

3. Gram variable

4. Mycobacterial

The correct answer is: Gram negative

The correct response identifies Gram-negative bacteria as being associated with endotoxins, which are components of the outer membrane of these bacteria. Endotoxins are primarily composed of lipopolysaccharides (LPS), which become prominent during bacterial lysis and can trigger strong immune responses in the host organism. When Gram-negative bacteria die or multiply, they release endotoxins that can result in inflammation and other extensive physiological effects, such as fever and septic shock. In contrast, Gram-positive bacteria do not contain endotoxins in the same manner, as their structure lacks the outer membrane characteristic of Gram-negative bacteria. Instead, Gram-positive bacteria may produce exotoxins, which are secreted proteins that can be toxic, but these are fundamentally different from endotoxins. Gram-variable and mycobacterial bacteria also do not produce endotoxins. Gram-variable bacteria may show inconsistent staining due to structural variability, and mycobacteria have a unique cell wall composition that does not include endotoxins. Therefore, Gram-negative bacteria are distinctly recognized for their association with endotoxin production and its clinical significance.