<i>In vitro</i> competitive growth cultures.

<p>The MRSA clones ST22-IV (variant A, strain 54 isolated from sputum) and ST228-I (variant B5, strain 67 isolated from blood) were grown in pure culture (A) and in co-culture after inoculation in BHI broth at equal ratio (B and C). Growth rate was monitored for 24 hours by colony count after plating and normalizing the output value obtained at each time (t) to the input value at time 0 (t0). CFU: colony forming unit; statistically significant differences are indicated by symbols when present: * indicates a p value <0,05; **: p<0,01; ***: p<0,001. The competition index for mixed culture (D) was calculated at the different time points as the ST22-IV/ST228-I CFU ratio for the output (time t) divided by the corresponding ratio for the input (inoculum at time t = 0).