What is a common characteristic of quaternary ammonium compounds?

Quaternary ammonium compounds, commonly referred to as "quats," are known for their use as disinfectants and antiseptics. A defining characteristic is that they are not effective against certain resistant microorganisms, particularly Mycobacterium tuberculosis (TB). This is due to the structure of the TB organism, which has a waxy cell wall that inhibits the penetration by many common disinfectants, including quats.

While quaternary ammonium compounds are effective against a range of bacteria, fungi, and some viruses, their limited efficacy against TB makes them unsuitable for situations where the disinfection of TB-contaminated surfaces or materials is required. This characteristic is crucial for healthcare environments where infection control is vital.

In contrast, sporicidal action is typically associated with other disinfectants, such as bleach or hydrogen peroxide, which can kill bacterial spores. The notion that quats are only effective in diluted form does not reflect their practicality, as they can be effective at certain dilutions, but this is not their primary characteristic. Additionally, while they serve as antiseptics, they are not classified as the best in comparison to other antiseptics that demonstrate efficacy against a broader range of pathogens, including TB.