Evaluation of a chromogenic medium for rapid detection of extended spectrum beta-lactamase producing Salmonella spp.

BACKGROUND & OBJECTIVES Salmonella spp. resistant to second- and third-generation cephalosporins and related antibiotics by production of various extended-spectrum beta-lactamases (ESBLs) are on the rise in Turkey. Early detection of ESBL producing Salmonella is important to institute appropriate treatment in time. In this study rapid detection of ESBL production among clinical isolates of Salmonella was evaluated using double-disk synergy test in a new chromogenic medium. The colour of the medium changes from red to yellow with bacterial growth and red circular inhibition zones are produced around disks containing antibacterials. METHODS A total of 182 clinical isolates of Salmonella were evaluated in this study. The presence of ESBLs in clinical isolates was determined by double-disk synergy test using Mueller-Hinton (MH) agar and Quicolor E&S agar plates. RESULTS Six isolates were shown to harbour ESBL enzymes with double disk synergy test by Mueller Hinton agar. The same results were obtained using Quicolor E&S agar after 4-6 h by changing its colour in response to the metabolic activity of growing bacteria. INTERPRETATION & CONCLUSION Our findings showed that with this new medium, the results can be evaluated rapidly within 4-6 h and the enhancement of inhibition zones can be easily detected with the colour changes thus enabling the treating physician to institute the right treatment regimen immediately.