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Bacteriacan becomeresistanttoantibiotics, disinfectants and antisepticsas a result of spontaneous changes in
theirDNA(mutations) or a gene transfer from
anotherbacterium. When different
exposed toantibiotics, those that haveresistancegenessurvive
while the others are killed. Over time, this can lead to the selective survival
and to an increase of resistance. One method to test bacteria for
resistance to antibiotic is: Resistance may also be established through tests
that directly detect the existence of a specific resistance mechanism.
For instance, beta lactamase detection can be done with the use of an assay for
example the chromogenic cephalosporinase test (Cefinase disk by BD Microbiology
Systems, Cockeysville, MD and BBL DrySlide Nitrocefin, Becton Dickinson,
Sparks, MD) and detection for chloramphenicol modifying enzyme chloramphenicol
acetyltransferase (CAT) may employ commercial colorimetric assays for instance
a CAT reagent kit (Remel, Lenexa, Kansas).