Fig. 7
CST-heteroresistant phenotype of phoPQ-, eptA-, and arnT-deleted mutants derived from various species of ECC. Deletion mutants were prepared for the following seven representative species of ECC clinical isolates: SMEnt819 (E. asburiae by ANI, hsp60 cluster I), SMEnt494 (E. cancerogenus, hsp60 cluster I), SMEnt1102 (E. cloacae subsp. cloacae, hsp60 cluster XI), SMEnt835 (E. cloacae subsp. dissolvens, hsp60 cluster XII), SMEnt513 (E. kobei, hsp60 cluster II), SMEnt1062 (E. roggenkampii, hsp60 cluster IV), and SMEnt1003 [E. chuandaensis (ANI value 94.1%), hsp60 cluster IX]. A Heat maps representing bacterial growth and occurrence of CST-resistant subpopulations in the presence of CST. Bacterial growth was measured by assessing turbidity (OD600) after cultivation for 20 h based on the broth microdilution method in 96-well plates. OD600 < 0.1 was defined as no growth. A CST MIC ≥ 4 mg/L was defined as CST resistance. The occurrence frequencies of CST-resistant subpopulations were measured in the presence of 1 or 8 mg/L CST. Color shading was used to visualize the turbidities (OD600) and frequencies of CST-resistant subpopulations at each CST concentration. Turbidities (OD600) decrease from yellow to purple and occurrence frequencies of CST-resistant subpopulations in PAP decrease from red to blue. B Comparison of arnT mRNA expression levels in the presence of CST (16 mg/L) between parent strains and their phoPQ-deleted mutants. The y axis shows relative mRNA expression levels normalized by those in the absence of CST in each strain (set to 1.0). *p = 0.002