In vitro exotoxin expression of wildtype S. aureus isolates. JKD6159 (ST93-IV [2B]) compared with non-ST93 CA-MRSA strains FPR 3757 USA300 (ST8-IV [2B]), JKD6177 (ST30-IV [2B]), and JKD6272 (ST1-IV [2B]); Hospital-associated MRSA strain JKD6009 (ST239-III [3A]), wildtype ST93 strains TPS3104 (ST93-IV [2B]), TPS3105 (ST93-IV [2B]), and TPS3106 (ST93-V [5C2&5]). (A) LukF-PV expression measured by quantitative Western blot. RN4220 was included as a negative control because it does not contain lukF-PV. All PVL negative strains did not express LukF-PV. There was no significant difference in the amount of LukF-PV expressed by the S. aureus strains containing lukSF-PV. Data shown are mean intensity of bands in arbitrary units and SEM. (B) PSMα3 expression measured by HPLC. JKD6177 did not produce PSMα3. JKD6272 (p = 0.0003), JKD6009 (p = 0.0003), TPS3105 (p < 0.0001) and TPS3106 (p = 0.0100) produced less deformylated and N-formylated PSMα3 compared to JKD6159. There was no difference between PSMα3 production by JKD6159 and USA300. TPS3104 expressed more PSMα3 than JKD6159 (p = 0.0029). Data shown are mean concentration (μg/ml), presented as vertical stacked bars and SEM. Deformylated PSMα3 is shown in grey bars. N-formylated PSMα3 is shown in white bars. (C) Hla expression measured by quantitative Western blot. RN4220 was included as a negative control because it does not express Hla. JKD6159 expressed more Hla compared to all non-ST93 wildtype strains (p < 0.0001 for all strains except JKD6177 p = 0.0107). TPS3105 and TPS3106 produced significantly less Hla (p < 0.0001). There was no difference in Hla production between JKD6159 and TPS3104. Data shown are mean intensity of bands in arbitrary units and SEM. Note, ***p < 0.001, **p < 0.01, *p < 0.05.
Chua et al. BMC Microbiology 2014 14:31 doi:10.1186/1471-2180-14-31