In vitro activity of antimicrobial agents against Legionella isolated from environmental water systems: first results from Turkey

Abstract

We evaluated the in vitro activity of antimicrobial agents against Legionella obtained from hotel and hospital water systems in three different regions of Turkey. Sixty-five Legionella strains (Legionella pneumophila serogroup 6 [n=32], L. pneumophila serogroup 1 [n=27], L. pneumophila serogroup 3 [n=2], and Legionella spp. [n=4]) were tested against levofloxacin, ciprofloxacin, clarithromycin, azithromycin, and rifampicin. The minimum inhibitory concentration (MIC) values of each antimicrobial agent for these strains was determined by the microdilution method using buffered yeast extract medium supplemented with 0.1% ketoglutarate broth. L. pneumophila ATCC 33152, Staphylococcus aureus ATCC 29213, and Escherichia coli ATCC 25922 were used as controls. Minimum inhibitory concentration values were in the following ranges: clarithromycin 0.001-0.5 mg/L, azithromycin 0.001-0.5 mg/L, levofloxacin 0.001-0.5 mg/L, ciprofloxacin 0.001-0.125 mg/L, and rifampicin 0.001- 0.5 mg/L. The MIC(90) for rifampicin, levofloxacin, ciprofloxacin, azithromycin, and clarithromycin were 0.015, 0.125, 0.06, 0.125, and 0.06 mg/L, respectively. To the best of our knowledge, this is the first study to determine in vitro activities of antimicrobial agents against Legionella species in Turkey. Rifampicin had the lowest MIC(90) value. It would seem that azithromycin and clarithromycin exhibit good activity as well as levofloxacin and ciprofloxacin against Legionella isolated from environmental water systems in Turkey.

Assessment of antibiotic susceptibility of <i>Legionella pneumophila</i> isolated from water systems in Poland

“…has usually been based on the determination of MIC values by micro-broth dilution, agar dilution, E-test methods, cell culture models (e. g. human monocytes), and animal models. Another method is the disc diffusion method [7,9,22]. None of these methods, however, are a gold standard for the susceptibility testing of L. pneumophila [12].…”

“…The use of agar and broth dilution methods are limited because of the intracellular location of the bacteria of the genus Legionella [9]. Another limitation of the susceptibility testing methods are the specific nutritional requirements of this microorganism [14].…”

“…has not been yet documented [9,11]. Only in vitro studies showed antibiotic-resistance variants [12].…”

“…They have a superior in vitro activity and greater intracellular penetration [8,9]. Also, rifampicin is used in severe cases of Legionella infection, especially in immunocompromised patients and patients with comorbidities (e.g.…”

“…obstructive lung disease, or diabetes mellitus) [10]. In clinical practice, this drug is used most often in combination with other antimicrobial drugs because of the possibility of developing resistance [8,9].…”