Rapid detection of ceftriaxone resistance in clinical isolates of extensively drug resistant Salmonella enterica serovar Typhi

Objective: To see the efficacy of rapid colour test for the sensitivity of ceftriaxone against clinical isolates of salmonella typhi.

Methods: The cross-sectional validation study was conducted at the Department of Microbiology, Pakistan Navy Ship Shifa Hospital, Karachi, from Nov 2018 to April 2019, and comprised clinical isolates of salmonella typhi that were obtained from five different hospitals in Karachi and Hyderabad. The isolates were tested using the rapid colour test. All the isolates were also tested using the conventional disc diffusion method and minimum inhibitory concentrations on the Vitek-2 version 8.01.

Results: Of the 97 isolates, 83(85.5%) were ceftriaxone-resistant and 14(14.4%) were ceftriaxone-sensitive. Sensitivity and specificity of the rapid colour test were 100% when compared with the results of the other methods. All the results were readable within 2 hours on the colour test.

Conclusions: The colour test was found to be a rapid, accurate and inexpensive tool to screen for ceftriaxone resistance in typhoid-endemic areas.