Which test determines inducible clindamycin resistance in staphylococci and streptococci?

The D-zone test is a laboratory method specifically designed to identify inducible clindamycin resistance in staphylococci, especially in Staphylococcus aureus and some streptococci. This test is important because certain bacteria can exhibit resistance to clindamycin when exposed to erythromycin, which may not be apparent in standard susceptibility testing.

In performing the D-zone test, a disk of erythromycin and a disk of clindamycin are placed on an agar plate inoculated with the bacteria in question. If the bacteria are sensitive to clindamycin in the absence of erythromycin, you'll see a clear zone around the clindamycin disk. However, if the bacteria exhibit inducible resistance, a flattening or "D" shape will be observed in the clindamycin zone adjacent to the erythromycin disk, indicating that the presence of erythromycin has induced resistance to clindamycin.

This specific nature of the D-zone test makes it an essential tool in the clinical microbiology laboratory for determining appropriate antibiotic therapy, helping clinicians effectively manage infections caused by these bacteria.