KOH string and Vancomycin susceptibility test as an alternative method to Gram staining

Abstract

Gram staining is a common technique to differentiate Gram positive and Gram negative bacteria. They may be gram variable (incorrectly identified) due to rapid decolorization of Gram positive bacteria and poor decolorization of Gram negative bacteria. There are few alternative techniques. Potassium hydroxide (KOH) string test and Vancomycin susceptibility test were done in addition to Gram stain to differentiate bacteria and were compared. The study was done in Academy of Medical Sciences, Pariyaram, Kannur. Total 300 various isolates were collected and analysed for its bacterial identification; various samples were subjected to Gram stain, KOH string test and Vancomycin susceptibility test. Of all Gram positive cocci, 91(100%) showed KOH string test negative and 89(97.8%) Vancomycin sensitive. Out of all Gram negative bacilli, 209(100%) showed KOH string test negative and Vancomycin resistant. KOH string test and Vancomycin susceptibility tests can be used as alternative or in addition to Gram stain for rapid identification of bacteria and better accuracy.