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Methodology for the Study of Horizontal Gene Transfer in Staphylococcus aureus
Published on: March 10, 2017
Practical disk diffusion method for detection of inducible clindamycin resistance in Staphylococcus aureus at a
Abstract:
The increase in incidence of variety of infections due to Staphylococcus aureus and especially methicillin resistant Staphylococcus aureus has highlighted on the need for better agents to treat such infections. Also the resistance to antimicrobial agents among staphylococci is an increasing problem. The macrolide-lincosamide-streptogramin B (MLS(B)) groups of antibiotics are commonly used in the treatment of staphylococcal infections with clindamycin being the preferred agent. This study demonstrates a simple phenotypic method (D-test) for detecting inducible clindamycin resistance in erythromycin resistant strains of staphylococcus aureus & coagulase negative Staphylococcus. A total of 181 erythromycin resistant staphylococcal isolates were obtained from various clinical specimens. Among the Staphylococcus aureus isolates, 38 (25.4%) were methicillin resistant Staphylococcus aureus (MRSA) and 112 (74.6%) were methicillin sensitive staphylococcus aureus (MSSA). Constitutive resistance was seen in 56 (37.3%) of isolates. Of these 18 (47.4%) were MRSA and 38 (33.9%) were MSSA. Inducible resistance was seen in 25 (16.6%) isolates, in which 11(28.9%) were methicillin resistant Staphylococcus aureus & 14 (12.6%) were methicillin sensitive staphylococcus aureus. It is likely that the true percentage of clindamycin resistance is being underestimated, since testing for inducible resistance is not being routinely performed. So the test should be done routinely in all the labs to avoid therapeutic failures.
Insights
The D-test can detect inducible clindamycin resistance in Staphylococcus aureus, which is often missed by standard methods. Routine use of this test is crucial for effective treatment of staphylococcal infections.
Area of Science:
- Medical Microbiology
- Antimicrobial Resistance
- Clinical Diagnostics
Background:
- Increasing incidence of Staphylococcus aureus infections, including methicillin-resistant strains (MRSA).
- Growing problem of antimicrobial resistance among staphylococci, particularly to commonly used antibiotics like clindamycin.
- Macrolide-lincosamide-streptogramin B (MLS(B)) antibiotics are vital for treating staphylococcal infections.
Purpose of the Study:
- To demonstrate a simple phenotypic D-test for detecting inducible clindamycin resistance in erythromycin-resistant Staphylococcus species.
- To evaluate the prevalence of inducible and constitutive clindamycin resistance in clinical isolates of Staphylococcus aureus.
- To highlight the potential underestimation of clindamycin resistance due to the lack of routine inducible resistance testing.
Main Methods:
- Phenotypic D-test used to identify inducible clindamycin resistance.
- Analysis of 181 erythromycin-resistant staphylococcal isolates from clinical specimens.
- Differentiation of Staphylococcus aureus into methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) strains.
Main Results:
- Constitutive clindamycin resistance observed in 37.3% of isolates (47.4% MRSA, 33.9% MSSA).
- Inducible clindamycin resistance detected in 16.6% of isolates (28.9% MRSA, 12.6% MSSA).
- A significant proportion of erythromycin-resistant strains exhibited inducible clindamycin resistance.
Conclusions:
- The D-test is an effective method for detecting inducible clindamycin resistance in Staphylococcus species.
- Routine implementation of the D-test is recommended to avoid underestimation of clindamycin resistance.
- Accurate detection of clindamycin resistance is essential to prevent therapeutic failures in staphylococcal infections.
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