Abstract
The parC and gyrA genes of 73 ciprofloxacin-resistant and 6 ciprofloxacin-susceptible Enterococcus faecium clinical isolates were partly sequenced. Alterations in ParC and GyrA, possibly in combination with other resistance mechanisms, severely restricted the in vitro activities of the nine quinolones tested. For all isolates, clinafloxacin and sitafloxacin showed the best activities.
Highlights
Different FluoroquinolonesThese results demonstrate an association between protein alterations and increased MICs. for isolates with no identifiable mutations, MICs were lower than those for isolates with only a single amino acid change in ParC
Eight different single or combined amino acid changes were detected in 42 of the 73 ciprofloxacin-resistant isolates of E
Since ciprofloxacin is still the most commonly used quinolone, our finding of six isolates with alterations only in ParC, together with the fact that no isolate with just GyrA alterations was found, suggests that topoisomerase IV is the primary target of ciprofloxacin in E. faecium
Summary
These results demonstrate an association between protein alterations and increased MICs. for isolates with no identifiable mutations, MICs were lower than those for isolates with only a single amino acid change in ParC. Our data indicate a limited impact of additional GyrA alterations on ciprofloxacin resistance in E. faecium, in contrast to their proposed importance in S. aureus and S. pneumoniae [4, 7, 14, 26].
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