D-Test Method for Inducible Clindamycin Resistance in Staphylococcus Aureus from Clinical Samples of Children at a Tertiary Care Hospital

Abstract

Background: Inducible clindamycin resistance in Staphylococcus aureus is an evolving problem, which may cause treatment failure if not routinely detected by the D-test.

Objective: To investigate the frequency of inducible clindamycin resistance in Staphylococcus aureus from various clinical specimens by D-Test.

Methodology: The cross-sectional study was conducted from September 2023 to December 2023 in the Department of Microbiology, Children Hospital and University of Child Health Sciences, Lahore. The samples were taken and cultured on blood agar and MacConkey agar. Gram staining, catalase and coagulase tests were performed for the identification of Staphylococcus aureus (S.aureus). Isolates from all the samples were tested for antibiotic sensitivity by using Kirby Bauer’s disc diffusion method. The cefoxitin (30 µg) disc was used to detect methicillin-resistance. D-Test was conducted by putting the discs of Clindamycin and Erythromycin at a distance of 15-26mm (edge to edge) on Mueller Hinton agar and D-Test results were recorded. SPSS-23 was used for statistical analysis. The frequencies and percentages were computed; Chi square test and Fisher's Exact Test were used to find the association with p value of <0.05 considered significant.

Results: Out of 164 Staphylococcus aureus 117(71.3%) were Methicillin resistant Staphylococcus aureus (MRSA) and 47(28.7%) were Methicillin sensitive Staphylococcus aureus (MSSA). Out of 164 Staphylococcus only 14(8.5%) were D-Test positive i.e.inducible clindamycin resistance. Of these 14 D-Test positive 12(85.7%) were MRSA and only 2(14.3%) were MSSA

Conclusion: Inducible clindamycin resistance is seen in Staphylococcus aureus, mostly MRSA. D-Test should be included as part of routine microbiology laboratory practice to get an idea about efficacy of Clindamycin in infections caused by S.aureus.