The Interpretative Categorization based on Conventional Disk -Diffusion and MIC Determination for VRSA - A Report

A female child aged about 11 years from rural area got admitted to our hospital with a history of swelling over the dorsum of (R) forearm for the last 10 days and fever for 2 days. A diagnosis of abscess was made and the abscess was incised and drained, sent the pus for culture and sensitivity. On culture Staphylococcus aureus was isolated. The antibiogram showed Vancomycin resistance and indistinct zone of inhibition around the Oxacillin disk on Mueller-Hinton agar. The isolate was tested for purity and tested for CDC algorithm as the report of Vancomycin resistance to clinicians bears significant public health concern. On subjecting the isolate for the same, it was found to be sensitive to Oxacillin (MIC) by E-Test, also Vancomycin sensitive by Stroke's method on Mueller-Hinton agar using ATCC-12600 as Staphylococcus aureus strain as sensitive control. We concluded that zones of inhibition on Mueller-Hinton agar disk diffusion are not fully reliable especially when reporting Vancomycin resistance as evidenced by many studies. The isolate is stored in the Laboratory.