• Adeel Zafar, Nazia Khursheed, Fareeha Adnan, and Qurat Ul Ain Zahid.
• Department of Pathology (Microbiology), Indus Hospital and Health Network, Karachi, Pakistan.
• J Coll Physicians Surg Pak. 2024 Feb 1; 34 (2): 183186183-186.

ObjectiveTo compare the performance of Vitek2 with the gold standard D test in terms of inducible clindamycin resistance (ICR) detection.Study DesignDescriptive study. Place and Duration of the Study: Indus Hospital and Health Network Karachi, Pakistan, from November 2021 to April 2022.MethodologyStandard 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.ResultsA 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.ConclusionVitek 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.Key WordsMethicillin-resistant Staphylococcus aureus, Inducible clindamycin resistance, D zone, Vitek2.

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