Disinfectants and the Kirby-Bauer Method


Disinfectantsand the Kirby-Bauer Method

Disinfectantsand the Kirby-Bauer Method

Disinfectantswork through the application of three mechanisms. Cross-linking isthe first mechanism where the disinfectant interlinks with thephysiological structure of the microbe, causing its death. Clumpingis the action of the disinfectant to cause the microbe’s tissues toform a mass, thereby dying off (Walsh,2003). Thirdly,Coagulation is a disinfectant mechanism where the antibiotic causesthe intracellularconstituents ofthe bacteria to change from a liquid environment to a gel (McDonnell1&amp Russell, 1999). This causes the death of the microbes bydamaging its physiological functioning.

TheGram-negative Bacteria are the microbes that are most resistant todisinfectants. This is because their Burkholderiaand Pseudomonasgive them their abilityto adapt to the disinfectant and create a resistance to disinfection(Walsh,2003). TheVegetable bacteria are the microbes that are most susceptibleto disinfectants. Other microbes that are most susceptible areviruses, molds and fungi since they are the most commonmicroorganisms found in the environment.

Indisinfecting using the Kirby-Bauermethod,the abilityof the disinfecting agent to diffuse, and the size of the inoculumsare the main factors that influence the inhibition size and the zone.The size of the zone is dependent on the effectiveness of theantibiotic to stop the multiplication of the bacteria (Walsh,2003). Otherfactors include the type of the medium used and the level ofresistance mechanisms of the microbe being disinfected against.

TheKirby-Bauertesting methodcan be used to determine whetheran antimicrobial agent is bactericidal or bacteriostatic by applyingdisk diffusing antibiotic sensitivity (Chart, 1994) testing. Thismethod helps in indicating the population change of the microbesafter the action of the agent. The Kirby-Bauermethod is applied by using antibiotic-impregnatedwafers to assess the ability of the antibiotic to affect the targetedbacteria


McDonnell1,G., &amp Russell, D. A. (1999). Antisepticsand Disinfectants: Activity, Action, and Resistance. RetrievedFrom, &lthttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC88911&gtOctober 14, 2014

Chart,H. (1994). Methodsin Practical Laboratory Bacteriology.New York: CRC Press

Walsh,C. (2003). Antibiotics:Actions, Origins, Resistance.Washington: ASM Press