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In vitro activity of antimicrobial agents against Legionella isolated from environmental water systems: first results
Haluk Erdogan1, Fusun Can, Muge Demirbilek
1Department of Infectious Diseases and Clinical Microbiology, Baskent University Faculty of Medicine, Ankara, Turkey. erdoganhaluk@hotmail.com
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.
Insights
This study assessed antimicrobial effectiveness against Legionella bacteria from Turkish water systems. Rifampicin showed the lowest MIC(90), indicating strong activity against these environmental Legionella strains.
Area of Science:
- Microbiology
- Infectious Diseases
- Environmental Health
Background:
- Legionella bacteria are a significant cause of pneumonia, often found in man-made water systems.
- Controlling Legionella in healthcare and hotel environments is crucial for public health.
- Limited data exists on antimicrobial resistance patterns of Legionella in Turkey.
Purpose of the Study:
- To evaluate the in vitro antimicrobial activity of five agents against Legionella strains from Turkish water systems.
- To determine the minimum inhibitory concentration (MIC) values for key antibiotics.
- To identify the most effective antimicrobial agent for treating Legionella infections originating from these sources.
Main Methods:
- Sixty-five Legionella strains were isolated from hotel and hospital water systems across Turkey.
- Microdilution method was used to determine MIC values for levofloxacin, ciprofloxacin, clarithromycin, azithromycin, and rifampicin.
- Standardized bacterial strains (L. pneumophila ATCC 33152, S. aureus ATCC 29213, E. coli ATCC 25922) were used as controls.
Main Results:
- All tested antimicrobial agents demonstrated activity against the isolated Legionella strains.
- Rifampicin exhibited the lowest MIC(90) value (0.015 mg/L), suggesting potent efficacy.
- Azithromycin, clarithromycin, levofloxacin, and ciprofloxacin also showed significant activity with MIC(90) values ranging from 0.06 to 0.125 mg/L.
Conclusions:
- Rifampicin is a highly effective antimicrobial agent against Legionella species found in Turkish environmental water systems.
- Azithromycin, clarithromycin, levofloxacin, and ciprofloxacin are also effective options for treating Legionella infections.
- This study provides valuable data on antimicrobial susceptibility for Legionella in Turkey, informing clinical and public health strategies.
