Antimicrobial agent susceptibilities of Legionella pneumophila MLVA-8 genotypes

Abstract

Legionella pneumophila causes human lung infections resulting in severe pneumonia. High-resolution genotyping of L. pneumophila isolates can be achieved by multiple-locus variable-number tandem-repeat analysis (MLVA-8). Legionella infections in humans occur as a result of inhalation of bacteria-containing aerosols, thus, our aim was to study the antimicrobial susceptibilities of different MLVA-8 genotypes to ten commonly used antimicrobial agents in legionellosis therapy. Epidemiological cut-off values were determined for all antibiotics. Significant differences were found between the antimicrobial agents’ susceptibilities of the three studied environmental genotypes (Gt4, Gt6, and Gt15). Each genotype exhibited a significantly different susceptibility profile, with Gt4 strains (Sequence Type 1) significantly more resistant towards most studied antimicrobial agents. In contrast, Gt6 strains (also Sequence Type 1) were more susceptible to six of the ten studied antimicrobial agents compared to the other genotypes. Our findings show that environmental strains isolated from adjacent points of the same water system, exhibit distinct antimicrobial resistance profiles. These differences highlight the importance of susceptibility testing of Legionella strains. In Israel, the most extensively used macrolide for pneumonia is azithromycin. Our results point at the fact that clarithromycin (another macrolide) and trimethoprim with sulfamethoxazole (SXT) were the most effective antimicrobial agents towards L. pneumophila strains. Moreover, legionellosis can be caused by multiple L. pneumophila genotypes, thus, the treatment approach should be the use of combined antibiotic therapy. Further studies are needed to evaluate specific antimicrobial combinations for legionellosis therapy.

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

“…The effectiveness of quinolones—ciprofloxacin, this time—was recorded in a later study by Sikora A. et al [ 46 ]. Contrary to these findings, it was Sharaby et al [ 30 ] who revealed some slight resistance against quinolones but an effectiveness of doxycycline, clarithromycin, rifampicin and trimethoprim sulphamethoxazole (SXT). Nevertheless, despite the finding of the potency of rifampicin, it should be noted that this antibiotic is not suggested for monotherapy due to the rapid appearance of resistance [ 47 ].…”

“…However, it was, again, one of the less active agents. By contrast, Sharaby et al [ 30 ] studied several environmental and clinical genotypes and revealed a discrepancy in antimicrobial agents’ susceptibilities, even in environmental strains that were isolated from adjacent points of the same water system. This is of importance considering that in some cases, the pneumonia caused by Legionella infection may hide a mixture of L. pneumophila strains [ 49 , 50 ].…”

“…These were the ECOFF value guidelines proposed but not yet officially established by the European Society of Clinical Microbiology and Infectious Diseases (EUCAST) and the ones proposed by Bruin et al [ 29 ], a reference used in many of the review papers. A recent publication by Sharaby [ 30 ] has also dealt with the important matter of the ECOFF lines. Sharaby [ 30 ] and Bruin et al [ 29 ] suggest similar ECOFF lines; however, they differ from the ECOFF lines for the seven antibiotics included in the review, shown in Table 3 .…”

“…A recent publication by Sharaby [ 30 ] has also dealt with the important matter of the ECOFF lines. Sharaby [ 30 ] and Bruin et al [ 29 ] suggest similar ECOFF lines; however, they differ from the ECOFF lines for the seven antibiotics included in the review, shown in Table 3 . At present, the EUCAST has not set ECOFF values for all the antibiotics of interest here and that are widely used in the treatment of LD [ 31 ].…”

Characterization of Legionella pneumophila Populations by Multilocus Variable Number of Tandem Repeats (MLVA) Genotyping from Drinking Water and Biofilm in Hospitals from Different Regions of the West Bank

“…For clinical reasons, genotyping should allow for a distinction with respect to virulence traits and antibiotic resistance [80]. Sharaby et al [81,82] showed that L. pneumophila isolates from Israel had MLVA-8 genotype-specific virulence traits. Even their resistance to antibiotics showed a strong correlation with the MLVA-genotypes.…”