Abstract

TSORAEVA, Anna et al. Evaluation of the new CromoCen ECCS medium for detection and identification of enteropathogenic bacteria . Rev Cubana Med Trop [online]. 2008, vol.60, n.2. ISSN 0375-0760.

ABSTRACT Background: In last few years, a wide range of chromogenic cultural media has been developed to provide useful tools for microbiological diagnostic. Objective: To evaluate the efficacy of a new chromogenic/fluorogenic medium _ known as CromoCen ECCS_ for the detection and presumptive identification of Gram-negative bacteria by examining stool specimens. Methods: Ten bacterial cultures from the reference collections and thirty three other isolated clinical strains were used in the inclusivity study. For the performance analysis, 68 stool specimens from one pediatric hospital were used. As a reference, SS agar and MacConkey agar were used as cultural media, with further identification by biochemical and serological tests. Results: It was evidenced that 92.8 % of Salmonella enterica strains, including Typhi and Paratyphi serotypes, developed typical colonies in the chromogenic cultural medium. Diagnostic sensitivity, specificity and efficiency ranged from 97 to 100 % for all target groups, and were better than the values of traditional cultural media. Growth of Salmonella enterica colonies was detected in 14 samples for coproculture and 13 of them were confirmed to be positive in direct culture in CromoCen ECCS for 24 hours. There were not statistically significant differences between the ratio of Salmonella-positive samples detected on CromoCen ECCS and on SS agar. The only sample positive to Escherichia coli O157 was isolated on the CromoCen ECCS. The infection caused by this bacterium was associated with that of Salmonella. Conclusion: This cultural medium was useful for presumptive identification of Gram-negative bacteria such as Escherichia coli O157:H7, Salmonella and Shigella, because the developed colonies had easily distinguished cultural characteristics.

Keywords : Chromogenic culture medium; presumptive identification; clinical samples; Gram-negative bacteria.