Minimum inhibitory concentration distribution in environmental Legionella spp. isolates

Abstract

In Greece standard tests are performed in the watering and cooling systems of hotels' units either as part of the surveillance scheme or following human infection. The purpose of this study was to establish the minimum inhibitory concentration (MIC) distributions of environmental Legionella isolates for six antimicrobials commonly used for the treatment of Legionella infections, by MIC-test methodology. Water samples were collected from 2004 to 2011 from 124 hotels from the four prefectures of Crete (Greece). Sixty-eight (68) Legionella isolates, comprising L. pneumophila serogroups 1, 2, 3, 5, 6, 8, 12, 13, 15, L. anisa, L. rubrilucens, L. maceachernii, L. quinlivanii, L. oakridgensis, and L. taurinensis, were included in the study. MIC-tests were performed on buffered charcoal yeast extract with α-ketoglutarate, L-cysteine, and ferric pyrophosphate. The MICs were read after 2 days of incubation at 36 ± 1 °C at 2.5% CO2. A large distribution in MICs was recorded for each species and each antibiotic tested. Rifampicin proved to be the most potent antibiotic regardless of the Legionella spp.; tetracycline appeared to have the least activity on our environmental isolates. The MIC-test approach is an easy, although not so cost-effective, way to determine MICs in Legionella spp. These data should be kept in mind especially since these Legionella species may cause human disease.

Antibiotic Resistance of Legionella pneumophila in Clinical and Water Isolates—A Systematic Review

“…In another Italian study [ 41 ], the authors revealed that rifampicin was the most active antibiotic followed by levofloxacin, tigecycline and doxycycline. These results coincide with the results of previous studies [ 28 , 29 , 38 , 42 , 43 , 44 ]. Furthermore, all the Legionella strains were inhibited by low concentrations of macrolides and fluoroquinolones, while between the macrolides, clarithromycin was, overall, the most active drug compared to azithromycin.…”

“…In deciding which antibiotics should be selected to work with, the following criteria were considered: (a) the most cited antibiotics in the revised articles included in the study ( Table S1 raw data), (b) the guidelines of the Sanford Guide to Antimicrobial Therapy [ 24 ], and (c) the antibiotics administered in Greece [ 25 , 26 , 27 , 28 ]. This process resulted in the inclusion of seven (7) antibiotics in the search, these being ciprofloxacin (CIP), erythromycin (ERM), azithromycin (AZM), doxycycline (DOX), levofloxacin (LEV), rifampicin (RIF) and clarithromycin (CL).…”

Legionella spp. Risk Assessment in Recreational and Garden Areas of Hotels

“…It should be noticed however, that it turns out that it not just the presence of a WSP that will ensure the diminishing of the danger for a human infection by water-borne pathogens (including Legionella ); its proper implementation is sometimes a more crucial factor [ 45 ]. In fact, it is possible that the improper implementation or the complete absence of a WSP (leading sometimes to temperature and pH values out of range) may provide the ideal stress conditions for the Legionella bacteria to develop a decreased sensitivity to antibiotics [ 46 ]. Of course, this is a huge aspect that needs further investigation.…”

Tea polyphenols suppress growth and virulence-related factors of <i>Haemophilus parasuis</i>

“…The MIC and MBC of tea polyphenols against H. parasuis were determined as previously described [ 9 , 20 ]. The MIC of tea polyphenols was defined as the minimum concentration at which no bacterial growth can be observed.…”