Heteroresistance is a term used to describe the behavior of certain populations of bacteria to an antibiotic. Several overlapping but different findings may be referred to as heteroresistance. The antibiotic serves to elicit heterogeneity in isolate.
Heteroresistance:
(1) involves a population of bacteria that seems to be isogenic (as opposed to a mixed culture)
(2) the bacteria show a range of susceptibilities to one or more antibiotics, identifying two or more subpopulations
Clinical significance - these bacteria may be associated with:
(1) recurrent or chronic infection
(2) higher morbidity and mortality
(3) emergence of resistant strains
Classification if heteroresistance based on population analysis profiling:
(1) lowest MIC for most susceptible strain
(2) highest MIC for the least susceptible strain
ratio of the MICs =
= (MIC for least susceptible) / (MIC for most susceptible
|
MIC Ratio
|
Interpretation
|
|
<= 4-fold
|
homogeneous
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|
8-fold
|
intermediate
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> 8-fold
|
heteroresistance
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A heteroresistant organism may be:
(1) completely susceptible
(2) classical heteroresistance (spectrum of susceptibility)
(3) completely resistant
