Antimicrobial susceptibility testing reveals reduced susceptibility to azithromycin and other antibiotics in Legionella pneumophila serogroup 1 isolates from Portugal

• DOI: 10.1007/s10096-024-04789-9
• Publication Date: 2024-05-02T12:02:02Z
• Authors: Corrado Minetti; Rachael Barton; Caitlin Farley; Owen Brad Spiller; Raquel Rodrigues; Paulo Gonçalves
• Keywords: Medical microbiology; Legionella; Legionnaires' disease

Abstract Backgroud Although not fully investigated, studies show that Legionella pneumophila can develop antibiotic resistance. As there is limited data available for Portugal, we determined the susceptibility profile of Portuguese L. serogroup 1 (LpnSg1) isolates against antibiotics used in clinical practice Portugal. Methods Minimum inhibitory concentrations (MICs) were LpnSg1 ( n = 100) and related environmental 7) isolates, collected between 2006–2022 context National Legionnaire´s Disease Surveillance Programme, azithromycin, clarithromycin, erythromycin, levofloxacin, ciprofloxacin, moxifloxacin, rifampicin, doxycycline, tigecycline, amoxicillin/clavulanic acid, using three different assays. Isolates also PCR-screened presence lpeAB gene. Results Twelve had azithromycin MICs above EUCAST tentative highest WT MIC, 9 which negative; erythromycin all tested within susceptible range. The number with MIC remaining was: ciprofloxacin: 7; levofloxacin: 17; moxifloxacin: 8; rifampicin: 11; doxycycline: 82; tigecycline: 4. breakpoints are acid. We estimated ECOFFs one isolate a eightfold higher than E-test ECOFF. Additionally, generated colonies growing on inhibition zone resulted fourfold parental isolate. Conclusions report, first time, elevated first-line other (including fluoroquinolones acid commonly to treat pneumonia patients Portugal) strains. point towards decreased circulating strains, justifying further investigation.