Advanced Dental Admission Test (ADAT) 2025 – 400 Free Practice Questions to Pass the Exam

Streptococcus pneumoniae is classified as Gram-positive and catalase negative, which reflects key characteristics of its cellular structure and biochemical properties.

Being Gram-positive means that the bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain used during the Gram staining procedure, resulting in a purple appearance under a microscope. This structural feature is significant because it often influences the organism's susceptibility to certain antibiotics and its overall virulence.

The fact that it is catalase negative means that Streptococcus pneumoniae does not produce the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen. This characteristic is typical of many streptococci and helps differentiate them from other bacteria, such as staphylococci, which are catalase positive.

This classification aids healthcare professionals in identifying the bacterium in laboratory settings and deciding on appropriate treatment options for infections caused by Streptococcus pneumoniae.