TABLE 10.
qac genes and susceptibility of S. aureus strains to some antiseptics and disinfectants
| qac genea | MIC
ratiosb ofc:
|
|||||||
|---|---|---|---|---|---|---|---|---|
| Proflavine | CHG | Pt | Pi | CTAB | BZK | CPC | DC | |
| qacA | >16 | 2.5 | >16 | >16 | 4 | >3 | >4 | 2 |
| qacB | 8 | 1 | >4 | 2 | 2 | >3 | >2 | 2 |
| qacC | 1 | 1 | ca. 1 | 1 | 6 | >3 | >4 | 1 |
| qacD | 1 | 1 | ca. 1 | 1 | 6 | >3 | >4 | 1 |
| MIC (μg/ml) for sensitive strain | 40 | 0.8 | <50 | 50d | 1 | <2 | <1 | 4 |
qac genes are otherwise known as nucleic acid binding (NAB) compound resistance genes (88).
Calculated from the data in reference 289. Ratios are MICs for strains of S. aureus carrying various qac genes divided by the MIC for a strain carrying no gene (the actual MIC for the test strain is shown in the bottom row).
CHG, chlorhexidine diacetate; Pt, pentamidine isethionate; Pi, propamidime isethionate; CTAB, cetyltrimethylammonium bromide; BZK, benzalkonium chloride; CPC, cetylpyridinium chloride; DC, dequalinium chloride.
The MIC of propamidine isethionate for the sensitive S. aureus is considerably higher than the normal quoted value (ca. 2 μg/ml [Table 6]).