Table 3. Effect of the single point mutations and spx on the emergence of teicoplanin resistance.
| No. bacteria under non-selective conditions T0 | No. bacteria under selective conditions T2 | Frequency of emergence1 | |||||
| Strain | Relevant genotype | Mean (n = 7) | SEM | Mean (n = 7) | SEM | T2/T0 | % |
| ISP794 | ISP794, rsbU − | 7.82×10+7 | 2.01×10+7 | 255 | 79 | 3.26×10−6 | 1003 |
| AR1079 | ISP794, yjbH(K23stop) eryr nearby | 6.98×10+7 | 1.95×10+7 | 895 | 201 | 1.28×10−5 | 394 |
| AR774 | ISP794, vraS(G45R) kan r nearby | 1.25×10+7 | 2.24×10+6 | >10002 | 8.00×10−5 | >1000 | |
| AR826 | ISP794, stp1(Q12stop) kanr nearby | 2.80×10+7 | 5.73×10+6 | >10002 | 3.50×10−5 | >1000 | |
1
Frequency of emergence expressed as the ratio of colony forming units (CFU) under selective (Teicoplanin 2 µg/ml) and non-selective conditions (No teicoplanin). Colony forming units were counted at 48 h, 37°C.
2
Viable counts on agar containing 2 µg/ml of teicoplanin were too high to accurately measure using these conditions. More than 1000 CFU were estimated in each experiment.
3
The effect of rsbU + on glycopeptide emergence is discussed in Galbusera et al [(30)]. ISP794 emergence frequency was set equal to 100% for normalization and comparison.
4
The emergence frequency was set equal to 100% for normalization and comparison with its derivative Δspx.