Gram-negative bacteria are generally more resistant
than gram-positive bacteria to disinfectants and antiseptics.
Pseudomonas and Burkholderia have porins in the cell wall with
characteristics that make them resistant to a lot of chemicals and
antibiotics. They can actually grow in some disinfectants and antiseptics
due to this resistance combined with the ability to metabolize some
unusual molecules.
Mycobacteria, endospores, and protozoan cysts and
oocysts are very resistant to disinfectants and antiseptics.
Nonenveloped viruses are generally more resistant
than enveloped viruses to disinfectants and antiseptics.
Lipid envelope is a target for chemical injury
Prions (infectious proteins that cause spongiform
encephalopathies) resist disinfection and autoclaving - CDC and WHO
now recommend a combination of sodium hydroxide and autoclaving at
134º C,
although research has shown that an
hour soak in sodium hydroxide followed by an hour of autoclaving at
136º C is "fairly effective". Proteases
have been used with some success in cleaning solutions to inactivate
prions.
3. Physiological State
Actively growing more susceptible.
Endospores least susceptible.
4. Environment
Organic material inhibits chemicals by binding them
and can insulate microorganisms against heat.
