Luria bertani lb

E. coli DH5α (BLP-positive, E. coli K-12 derivative) bacteria were stored in our laboratory. The E. coli JE5505 (BLP-negative, E. coli K-12 derivative) strain was obtained from The Coli Genetic Stock Center (CGSC) of Yale University (New Haven, CT; CGSC number 6672). Although the E. coli JE5505 strain lacks BLP, its normal physiological properties of growth and multiplication are not impaired (54 (link)). According to previously reported studies, E. coli DH5α was referenced for E. coli JE5505 during experimental infection (13 (link), 55 (link)). To determine the number of CFU in the bacterial suspension used in this study, 1 mL of bacterial suspension (1 × 10⁷ CFU/mL) was seeded in 100 mL of Luria-Bertani (LB; Oxoid, Basingstoke, UK) broth and incubated with shaking at 37°C for 12 h (optical density at 600 nm [OD₆₀₀] value of approximately 0.9 in the log phase). Thereafter, the cultured bacterial suspension was serially diluted and plated on LB agar plates and incubated at 37°C for 12 h. The colony counting technique was used to determine the total number of CFU (approximately 1 × 10⁸ CFU/mL). At least eight independent experiments were performed, and the results of CFU counting were consistent. C57BL/6J mice were provided by the Model Animal Research Center of Nanjing University, Nanjing, China.

Pseudomonas aeruginosa strain PAO1 (Holloway1C Stanier131) was obtained from the National Collection of Industrial, Food and Marine Bacteria (NCIMB), United Kingdom. PAO1 was grown in Luria-Bertani (LB, Oxoid) broth and on nutrient agar (Oxoid) at 37°C.

Bacterial strains were grown in Mueller Hinton (MH) (non-biofilm forming C. striatum, S. epidermidis, E. coli, K. pneumoniae, P. aeruginosa, S. aureus and clinical isolates CI1–5) and Luria Bertani (LB) (biofilm forming S. aureus ATCC 1167) media (Oxoid, Basingstoke, Hampshire, MA, USA) at 37 °C in aerobic conditions. To obtain a bacterial suspension suitable for antibacterial assays, fresh colonies of each strain, grown on MH and LB agar, were inoculated in MH and LB media, and incubated at 37 °C overnight. The bacterial suspension was resuspended in a fresh medium and further incubated at 37 °C until bacterial growth reached the exponential phase. Serial dilutions were performed to achieve the necessary bacterial load for the tests (1 × 10⁶ CFU/mL).