Sub-inhibitory concentrations of vancomycin prevent quinolone-resistance in a penicillin-resistant isolate of Streptococcus pneumoniae

Table 2 Mutations in topoisomerase IV (ParC and ParE) and gyrase (GyrA and GyrB) genes before and after cyclic exposure to ciprofloxacin, trovafloxacin, or either of these drugs plus vancomycin in a penicillin-resistant pneumococcal strain

Strain	ParC	ParE	GyrA	GyrB
WB4	None	none	none	none
WB4C	Ser79 → Tyr	none	none	Asp435 → Glu
WB4T	Ser79 → Phe	none	Ser81 → Phe	none
WB4 C+V	Ser79 → Tyr	none	none	none
WB4 T+V	None	none	none	none

WB4: quinolone-susceptible but penicillin-resistant parent pneumococcus; WB4 C: ciprofloxacin-resistant derivative selected by passages on this drug; WB4 T: trovafloxacin-resistant derivative selected by passages on this drug; WB4 C+V or WB4 T+V: same as above cycled in presence of subinhibitory concentrations of vancomycin.

ISSN: 1471-2180