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Effectiveness of a novel selective medium ‘Modified MacConkey Agar for Burkholderia’ for isolation of Burkholderia pseudomallei from contaminated specimen

Year: 2025

Type: article

Abstract: Melioidosis is a potentially fatal disease caused by the saprophytic bacterium Burkholderia pseudomallei . Culture remains gold standard for isolating B. pseudomallei from environmental specimens like soil. To facilitate its isolation, a novel selective medium- ‘Modified MacConkey agar for Burkholderia ’ (MMB) was developed previously by incorporating four antimicrobials into the widely available MacConkey agar medium. The present study evaluated the effectiveness of MMB medium in supporting the growth of B. pseudomallei compared to the well-established Ashdown medium. A total of 500 soil samples were collected from five selected districts of Bangladesh. Initial enrichment was performed by inoculating 20 g of soil into 20 ml of modified Ashdown broth. After 48 h of incubation, 1 ml of cultured broth was inoculated into 9 ml of fresh broth. Following seven days of incubation, each sample was sub-cultured onto both MMB and Ashdown media in parallel. Both media successfully grew 21 (4.20 %) isolates of B. pseudomallei , among 500 samples tested, showing equal sensitivity for isolating the organism (p = 1.00). The isolates were confirmed by specific latex agglutination test and real time PCR. Growth of contaminating soil bacteria was observed in 155 (31.00 %) soil samples on MMB medium in contrast to 185 (37.00 %) samples on Ashdown agar. In 30 (6.00 %) soil specimens, competing bacteria were effectively suppressed on MMB medium, but Ashdown medium was unable to inhibit their growth. Therefore, MMB medium may be more selective than Ashdown agar in inhibiting other soil saprophytes (p = .04). MMB medium represents a reliable and easy-to-prepare alternative to Ashdown medium for isolating B. pseudomallei from soil in resource-limited settings where melioidosis is most prevalent. Additional studies should be conducted to assess the medium’s effectiveness in recovering the organism from non-sterile clinical specimens as well.

Source: The Microbe

DOI: 10.1016/j.microb.2025.100507