Objective To promote Escherichia coli CCPM(A)-P-0000101, Klebsiella pneumoniae CCPM(A)-P-0000102, and Staphylococcus aureus CCPM(A)-P-0000100, which were collected in the Division for Medicinal Microorganisms Related Strains, Chinese Academy of Medical Sciences (CAMS) Collection Center of Pathogenic Microorganisms, to become the standard strains used in the evaluation of antimicrobial activity, their microbiological characteristics were measured and identified according to the Technical Requirements for Evaluation of National Standard Strains of Pathogenic Microorganisms(WS/T 812—2022).
Methods The bacterial morphology, biochemical testing, 16S rDNA sequencing, and susceptibility to antibiotics of the three strains were characterized by observation of the colonies on agar plates, Gram staining, and agar-dilution method. The passage stability of the three bacteria were further determined by comparing and analyzing the differences in bacterial growth curves, susceptibility to antibiotics, and 100% minimum lethal dose (MLD) to experimental mice between G10 and G1 strains.
Results The colony morphology, Gram staining, biochemical testing, and 16S rDNA sequencing identified the strains CCPM(A)-P-0000101, CCPM(A)-P-0000102, and CCPM(A)-P-0000100 with typical characteristics corresponding to E. coli, K. pneumoniae, and S. aureus, respectively. Except for antibiotics such as penicillin and ampicillin, the three bacteria showed a susceptible phenotype to most of the tested antibiotics. There was no significant difference in growth curves, susceptibility to antibiotics, and 100% MLD to experimental animals between the G10 and G1 strain of the three bacteria, indicating that they have good passage stability.
Conclusion The strains CCPM(A)-P-0000101, CCPM(A)-P-0000102, and CCPM(A)-P-0000100 own the typical and stable characteristics of their species, making them suitable as standard strains for the evaluation of antibacterial activity.