Determination of Inducible Clindamycin Resistance and Correlation with Vitek2 Inducible Clindamycin Resistance Test in Staphylococcus aureus Isolated from Clinical Samples

Objective: To compare the performance of Vitek2 with the gold standard D test in terms of inducible clindamycin resistance (ICR) detection. Study Design: Descriptive study. Place and Duration of the Study: Indus Hospital and Health Network Karachi, Pakistan, from November 2021 to April 2022. Methodology: Standard operating procedures of the laboratory were followed for processing of clinical samples. Methicillin-resistant Staphylococcus aureus (MRSA) isolates were included. The isolates from the same patient within two-week time period were excluded. Clinical laboratory standards institute guidelines were followed for performing and interpreting D test. The results of the D test were compared with Vitek2 results for ICR. Results: A total of 313 isolates were MRSA, of which 93 isolates tested positive for ICR on both the D test and Vitek2. Nine isolates were positive for ICR on Vitek2 and negative on the Kirby-Bauer disk diffusion method. One isolate tested positive on the disk method and negative on Vitek2. Conclusion: Vitek 2 appeared to give false positive results. Reporting false susceptibility of clindamycin can cause therapeutic failure which can markedly affect the patient's outcome. This discordance needs to be investigated further with a large sample size and stringent observation of D-test results to pick laboratory error.