Related Experiment Video
Updated: Jul 2, 2026
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Phenotypic detection of inducible clindamycin resistance among Staphylococcus aureus isolates by using the lower
G S Ajantha1, Raghavendra D Kulkarni, Jeevan Shetty
1Department of Microbiology, SDM College of Medical Sciences and Hospital, Sattur, Dharwad - 580 009, Karnataka, India. ajju_dwd@rediffmail.com
Context:
Clindamycin is one of the important alternative antibiotics in the therapy of Staphylococcus aureus, particularly in methicillin-resistant S. aureus (MRSA) infections. Inducible clindamycin resistance (iMLS B--inducible Macrolide-Lincosamide-Streptogramin B resistance) is a critical factor in antimicrobial susceptibility testing.
Aims:
To know the rate of inducible clindamycin resistance among clinical isolates of Staphylococcus aureus in our hospital by Disk approximation test (D-test) using the average recommended inter-disk distance and comparing the results with that of D-test using the lower limit of recommended inter-disk distance.
Materials And Methods:
A total of 51 erythromycin-resistant and clindamycin-susceptible S. aureus isolates were subjected to disk approximation testing with 21 +/- 1 mm and 15 mm edge-to-edge distance between the clindamycin and erythromycin disks.
Statistical Methods:
Z-test levels.
Results:
Among 51 erythromycin-resistant and clindamycin-susceptible S. aureus isolates, 25 (49%) were recorded as inducible clindamycin resistant by D-test with 21 +/- 1 mm edge-to-edge distance between the clindamycin and erythromycin disks. When we re-tested all the 51 strains by D-test with 15 mm inter-disk distance, we identified 14% more iMLS B strains previously reported as D-test negative. Z-test for MRSA indicates that 15 mm edge-to-edge distance has significant advantage.
Conclusions:
Since the incidence of inducible clindamycin resistance is high (63% in our study), accurate identification of inducible clindamycin resistance is important to prevent therapeutic failure in infections caused by these strains. We suggest the use of D-test with 15 mm edge-to-edge inter-disk distance for detecting iMLS B .
Insights
A closer D-test disk distance (15 mm) significantly improves the detection of inducible clindamycin resistance (iMLS B) in Staphylococcus aureus. This enhanced detection is crucial for preventing treatment failures in MRSA infections.
Area of Science:
- Clinical microbiology
- Antimicrobial resistance
- Infectious diseases
Background:
- Clindamycin is a key antibiotic for Staphylococcus aureus, including MRSA.
- Inducible clindamycin resistance (iMLS B) impacts treatment efficacy.
- Accurate detection of iMLS B is vital for antimicrobial susceptibility testing.
Purpose of the Study:
- To determine the rate of inducible clindamycin resistance in S. aureus isolates.
- To compare the D-test using average vs. lower limit inter-disk distances.
- To optimize the D-test for iMLS B detection.
Main Methods:
- Evaluated 51 erythromycin-resistant, clindamycin-susceptible S. aureus isolates.
- Performed Disk approximation test (D-test) with 21±1 mm and 15 mm inter-disk distances.
- Utilized Z-test for statistical analysis.
Main Results:
- The 21±1 mm D-test identified 49% inducible clindamycin resistance.
- The 15 mm D-test detected 14% more iMLS B strains.
- The 15 mm distance showed a significant advantage for iMLS B detection.
Conclusions:
- High incidence of inducible clindamycin resistance (63%) necessitates accurate detection.
- The 15 mm inter-disk distance D-test is recommended for reliable iMLS B identification.
- Optimized D-test use prevents therapeutic failures in S. aureus infections.
