Evaluation of Coli-ID and MUG Plus media for recovering Escherichia coli and other coliform bacteria from groundwater samples

Several chromogenic media for detecting coliform bacteria in water are comm ercially available including Coli ID medium (ID) (bioMerieux) and MUG Plus cefsulodin agar (MP) (Laboratorios Microkit, S.L.). Since little is known a bout the performance of these media, we have evaluated their usefulness for recovering Escherichia coli and other coliform organisms in groundwaters u sed for direct human consumption. Variance analysis of obtained data showed that no statistically significant differences in counts of E. coli and oth er coliforms on ID and MP media compared with reference methods. However, t he evaluation of sensitivity and recovery efficiency of both media showed t hat the two chromogenic media were more sensitive and significantly more ef ficient (P = <0.05) than reference medium for detecting coliforms in ground water. However, the identification of 400 typical and atypical colonies iso lated from ID and MP media demonstrated a higher specificity when using ID for coliforms and E. coli. In summary, the two chromogenic media evaluated could be used as alternative methods to reference media for detecting and r ecovering coliform bacteria in groundwater samples. MP agar was more sensit ive and efficient than ID agar whereas the latter was more specific and sel ective.