Comparison of Reasoner’s 2A Agar and Muller Hinton Agar Media for Microbiological Monitoring of Dialysis Water

Microbiological culture of dialysis water is a routine safety measure. In, Khorramabad laboratories perform these cultures on Muller Hinton Agar (MHA) at 35–378C for 48 h, not on the Reasoner’s 2A agar (R2A agar) at 17–238ºC for 7 days recommended by international standards, the objective of the present study was the comparison of the efficiency of R2A and MHA media in the counting of heterotrophic bacteria in the samples of water collected in dialysis centers from 2 hospitals in Khorramabad, from September to November 2019.

A total of 165 samples of treated water in dialysis centers were collected aseptically and then transported in ice‑packs to the Department of Medical Microbiology of the Lorestan University of Medical Sciences and the pour plate technique was carried out for the enumerating of heterotrophic bacteria. Finally, bacterial colonies were counted after incubation at 34±2ºC for 48 hours on MHA and 25ºC for 1 week on R2A.

Results showed heterotrophic bacterial counts in R2A were greater than those in MHA in 89% of the samples, so enumeration of heterotrophic bacteria should be carried out in R2A agar associated with longer incubation times, because of the greater sensitivity. The proportion of water samples yielding colony counts ≥200 CFU/mL by R2A -7d was significantly different from the proportion by MHA-48h (p<0.001).

The results proposed using R2A agar combined with relative low culture temperature (20-25°C), and an extended incubation time (7-10 days) is more efficient. However, as the spectrum of bacterial contamination is not similar for dialysis centers and countries, many studies using different media and culture parameters are required to confirm this.