Growth of Different Bacteria on Thiosulfate Citrate Bile Salts Sucrose Agar

Dear Editors, Thiosulfate citrate bile salts sucrose agar (TCBS agar) is a kind of selective agar culture plate used in microbiology laboratories to isolate Vibrio species.[1,2] In addition to other Vibrio species, Vibrio cholerae and Vibrio parahaemolyticus may be isolated using TCBS agar.[3,4] The current study aimed to evaluate bacterial and candida growth on TCBS as well as Vibrio spp. In this study, a total of 73 pathogens were isolated clinically from patients in different sites. Gram stain, colony morphology, and biochemical tests were done for microbial identification. After growth on culture media, a subculture on TCBS agar (HIMEDIA, India) was done for all isolates. Twenty isolates of Aeromonas hydrophila with positive growth as golden colony on TCBS. As well as 10 isolates of Enterococcus spp that grew on TCBS also with golden yellow colonies. Ten isolates of Proteus mirabilis revealed positive growth with yellow colonies and H2S production on TCBS. All three bacteria of Staphylococcus aureus also gave yellow colonies whereas all three Staphylococcus epidermidis were inhibited without growth on TCBS agar. All 20 Escherichia coli isolates were inhibited as well as two isolates of Klebsiella spp were also inhibited without growth. Three Pseudomonas aeruginosa bacteria and two Candida albicans yeasts gave no growth on TCBS agar [Table 1].Table 1: Bacterial and candida growth on thiosulfate citrate bile salts sucrose agarTCBS agar contains high concentrations of sodium citrate and sodium thiosulfate to inhibit the growth of Enterobacteriaceae. Hence, both E. coli and Klebsiella spp were fully inhibited on TCBS agar but P. mirabilis isolates were grown with yellow colonies. Another study mentioned that peptone special and yeast extract provide vitamin B complex, nitrogenous compounds, and other essential nutrients. Bile and sodium citrate inhibit Gram-positive bacteria and coliforms.[5] TCBS Agar is highly selective for Vibrio species. However, occasional isolates of Pseudomonas and Aeromonas may also form blue-green colonies on TCBS Agar.[6] In conclusion, TCBS can be considered a presumptive positive diagnosis for Vibrio spp but other bacteria such as Aeromonas hydrophila, Enterococcus spp, P. mirabilis, and S. aureus can grow and give yellow colonies so this media may be utilized as a good selective media for identification these bacteria as well as to V. cholerae. These bacteria that can give the same color and colony morphology on TCBS agar can confuse V. cholerae diagnosis so studying the characteristics of these bacteria is important for accurate diagnosis. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.