TABLE 2.
Mutations in topoisomerase IV (parC and parE) and gyrase (gyrA and gyrB) genes before and after cyclic exposure to levofloxacin or either of these drugs plus cefotaxime in two penicillin-resistant pneumoccocal strains
| Straina | Mutation(s)
|
|||
|---|---|---|---|---|
| ParC | ParE | GyrA | GyrB | |
| WB4 | None | None | None | None |
| WB4 L | Ser79→Tyr | None | Glu85→Lys | None |
| WB4 CTX+L | Lys137→Asn | None | None | None |
| KR4 | None | None | None | None |
| KR4 L | Ser79→Tyr | None | Glu85→Lys | None |
| Asp83→Tyr | ||||
| KR4 CTX+L | None | None | Pro162→Thr | None |
a
WB4 and KR4, quinolone-susceptible but penicillin-resistant parent pneumococci; WB4 L and KR4 L, levofloxacin-resistant derivative selected by passages on this drug; WB4 CTX+L and KR4 CTX+L, same as WB4 L and KR4 L, respectively, cycled in the presence of subinhibitory concentrations of cefotaxime (one-eighth of the MIC).