What D zone means in clindamycin testing?
What D zone means in clindamycin testing?
A flattening of the zone of inhibition around the Clindamycin disk proximal to the Erythromycin disk (producing a zone of inhibition shaped like the letter D) is considered a positive result and indicates that the Erythromycin has induced Clindamycin resistance (a positive “D-zone test”).
What does the D test test for?
A vitamin D blood test measures the level of 25(OH)D in your blood. Abnormal levels of vitamin D can indicate bone disorders, nutrition problems, organ damage, or other medical conditions.
What test is used for inducible clindamycin resistance?
Inducible clindamycin resistance can be detected with a simple disk approximation test, commonly referred as the D test [14]. For this test, an erythromycin disk is placed 15 mM to 26 mM (edge to edge) from a clindamycin disk in a standard disk diffusion test.
Why do we need to do the D test for MRSA isolates?
MRSA isolates with inducible clindamycin resistance (iCR) are resistant to erythromycin and sensitive to clindamycin on routine testing. D-test can help to determine whether clindamycin could be used as a therapeutic option2.
What does a negative D test mean?
A test result that shows the substance or condition the test is supposed to find is not present at all or is present, but in normal amounts. In genetics, a negative test result usually means that a person does not have a mutation (change) in the gene, chromosome, or protein that is being tested.
Is MRSA resistant to clindamycin?
Erythromycin and clindamycin resistance was seen in 54.4% (147/270) and 41.8% (113/270) isolates respectively. Resistance to erythromycin and clindamycin were higher in MRSA as compared to MSSA (erythromycin-resistance: 88.2% Vs 39.1% and clindamycin-resistance: 79.4% Vs 41.8%).
Can MRSA become resistant to clindamycin?
A prospective study conducted during 2001–2004 in Texas, USA, found a significant increase in resistance to clindamycin over the 3 years of the study. The prevalence of clindamycin resistance in MSSA and MRSA was found to be 11% and 6%, respectively, mostly constitutive.
How are bacteria resistant to clindamycin?
Most aerobic gram-negative bacteria, such as Pseudomonas spp and H. influenzae, are inherently resistant to clindamycin because of poor permeability of the cellular outer envelope to the drug.
How is MRSA resistant to clindamycin?
MRSA strains that are susceptible to clindamycin but resistant to erythromycin, however, may have the phenotype of in vitro inducible macrolide-lincosamide-streptogramin B (MLSB) resistance (iMLS) due to the presence of erythromycin ribosomal methylase (erm) genes.
Is clindamycin still effective if the D-Zone test is positive?
Despite positive results for inducible clindamycin resistance, clindamycin may still be effective in some patients. The D-zone test is only standardized to detect inducible clindamycin resistance for Staphylococcus spp., S.pneumoniae, and beta-hemolytic Streptococcus.
How do you test for inducible clindamycin resistance?
Routine antibiotic susceptibility tests cannot identify these strains. The D (inducible clindamycin resistance) test is employed to detect inducible clindamycin resistance. Procedure for Inducible Clindamycin Resistance (D) Test: Prepare 0.5 McFarland standard suspension of Erythromycin resistant Staphylococcus aureus isolates.
How do you test for erythromycin and clindamycin interaction?
In this test, erythromycin (macrolide) and clindamycin (lincosamide derivative) discs are placed adjacent to each other over the Mueller Hinton agar medium inoculated with the test organism.
Why is erythromycin resistant to clindamycin in Zone 1?
As a result, as erythromycin diffuses outward into Zone 1 bacterial resistance to clindamycin is induced prior to its diffusion from the neighboring disk.
