30 May 2021

Legionella AST - guidance updated

The EUCAST guidance document on susceptibility testing on L.pneumophila is updated.

Acquired antimicrobial resistance in L. pneumophila is rare [1-6]. However, a clinical isolate resistant to ciprofloxacin due to a single point mutation in the gyrA gene has been reported [7] and fluoroquinolone resistance have been described from patients during therapy [8]. An efflux pump (LpeAB) has been demonstrated to be responsible for elevated MICs (0.125-2 mg/L) for azithromycin [1]. The efflux pump is found in clinical isolates of L. pneumophila, related to specific sequence types [1,4,9]. Any clinical significance of reduced susceptibility to azithromycin has not been demonstrated. These findings also suggest erythromycin to be a poor predictor of macrolide-decreased susceptibility caused by this efflux pump.