TABLE 2.
PCR analysis of isolates and presence of biocide or heavy metal tolerance-mediating genes
| Biocide or heavy metal | MIC (μg/ml) | No. of isolates investigateda | No. of isolates positive for geneb | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Quaternary ammonium compounds | lmrS | mepA | norA | sepA | qacA/B | qacG | qacH | qacJ | smr | ||
| Benzalkonium chloride | ≥4 | 12 | 11 | 12 | 9 | 3 | 2 | 1 | |||
| Benzethonium chloride | ≥4 | 16 | 16 | 16 | 11 | 4 | 1 | 2 | 1 | 2 | |
| Acriflavine | ≥16 | 27 | 21 | 27 | 21 | 19 | 2 | ||||
| Bisbiguanides | lmrS | mepA | norA | sepA | qacA/B | qacG | qacH | qacJ | smr | ||
| Chlorhexidine | ≥2 | 9 | 8 | 9 | 5 | 3 | |||||
| Heavy metal ions | copA | mco | czrC | ||||||||
| Copper sulfate | ≥4,096 | 7 | 1 | 5 | NT | ||||||
| Zinc chloride | >8,192 | 3 | NT | NT | 3 | ||||||
a
Some isolates were included in PCR screening for more than one biocide or heavy metal ion and may therefore be listed repeatedly in this table.
b
NT, isolates were not tested for the tolerance-mediating genes listed above.