AUTHOR=Cruz Carolina , Rodrigues Lúcia , Fernandes Filipa , Santos Ricardo , Paixão Paulo , Chasqueira Maria Jesus 

TITLE=Antibiotic susceptibility pattern of Portuguese environmental Legionella isolates

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=13

YEAR=2023

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1141115

DOI=10.3389/fcimb.2023.1141115

ISSN=2235-2988

ABSTRACT=<sec><title>Introduction</title><p>Legionnaires’ Disease is a pneumonia caused by <italic>Legionella</italic> spp., currently treated empirically with fluoroquinolones and macrolides. In this study, we aim to describe the antibiotic susceptibility pattern of environmental <italic>Legionella</italic> recovered in the south of Portugal.</p></sec><sec><title>Methods</title><p>Minimal inhibitory concentration (MIC) determination of 57 <italic>Legionella</italic> isolates (10 Lp sg 1, 32, Lp sg 2-14 15 L. spp) was achieved by broth microdilution, as described by EUCAST, for azithromycin, clarithromycin, ciprofloxacin, levofloxacin, and doxycycline. </p></sec><sec><title>Results</title><p>Fluoroquinolones were the most active antibiotic, displaying the lowest MIC values in contrast to doxycycline which had the highest. MIC90 and epidemiological cut-off (ECOFF) values were, respectively, 0.5/1 mg/L for azithromycin, 0.125/0.25 mg/L for clarithromycin, 0.064/0.125 mg/L for ciprofloxacin, 0.125/0.125 mg/L for levofloxacin and 16/32 mg/L for doxycycline.</p></sec><sec><title>Discussion</title><p>MIC distributions were higher than reported by EUCAST for all antibiotics. Interestingly, two phenotypically resistant isolates with high-level quinolone resistance were identified. This is the first time that MIC distributions, <italic>lpeAB</italic> and tet56 genes have been investigated in Portuguese environmental isolates of <italic>Legionella</italic>. </p></sec>