S typhimurium atcc14028

To test the potency of rifamycin analogs of the disclosure in vitro, a broth growth inhibition assay was developed. For the assay, S. aureus NRS384 (BEI Resources), S. typhimurium AR-0031 (CDC & FDA Antibiotic Resistance Isolate Bank, Atlanta (GA): CDC 2018) (and S. typhimurium ATCC 14028 (American Type Culture Collection) were grown in Tryptic Soy Broth (TSB, Teknova) overnight, then sub-cultured 1:50 in fresh TSB and grown for an additional 2 h. The cultures were then pelleted via centrifugation and washed twice in PBS (Gibco). The cultures were then diluted to 1 × 10⁶ cfu/ml in TSB and 100 µl of the suspension was added per well to a 2 ml dilution plate in triplicate (Greiner Bio one). A dilution series of the indicated antibiotic was added 1:1 for a final starting concentration of 1 × 10⁻⁵M, then a 1:10 dilution for 1 × 10⁻⁶M, followed with 1:4 dilutions to include 2.5 × 10⁻⁷M, 6.25 × 10⁻⁸M, 1.56 × 10⁻⁸M, 3.91 × 10⁻⁹M, 9.77 × 10⁻¹⁰M, 2.44 × 10⁻¹⁰M, 6.1 × 10⁻¹¹M, 1.53 × 10⁻¹¹M, and 3.81 × 10⁻¹²M for a total of 11 points repeated 3 times. The plates were sealed and incubated at 37 °C with shaking for 24 h, then 150 µl of each sample was added to 96 well microtiter plates and OD₆₀₀ was read on a Spectramax i3 Minimax 300.

The strains of E. tarda and A. veronii were clinically isolated from the diseased flounders in our laboratory. S. hyicus 437-2 and 15095 strains were isolated from infected pigs in Tianjin Animal Husbandry and Veterinary Research Institute. S. typhimurium ATCC14028 and S. aureus (ATCC43300, ATCC546 and ATCC25923) were from American Type Culture Collection (ATCC). Other S. typhimurium and E. coli strains were purchased from China Veterinary Culture Collection Center (CVCC). P. aeruginosa CICC21630 was obtained from China Center of Industrial Culture Collection (CICC).

S. aureus ATCC25923, ATCC29213, ATCC43300, L. monocytogenes ATCCbaa751, B. cereus ATCC11788, E. coli ATCC25922, P. aeruginosa ATCC9027, and S. typhimurium ATCC14028 were obtained from the American Type Culture Collection (ATCC; Rockville, MD, USA). Mueller Hinton broth was purchased from Merck (Darmstadt, Germany).