Abstract
BackgroundTigecycline (TIG) is an antibiotic belonging to the glycylcyclines class and appears to be a good choice to fight infections caused by Staphylococcus aureus. To date, TIG exhibits good activity against this microorganism. The aim of this work was to obtain in vitro mutants of S. aureus resistant to TIG and evaluate possible changes in their susceptibility patterns to other antibiotics.ResultsTwo mutants of S. aureus resistant to TIG (MIC = 16 µg/mL) were selected in vitro from clinical isolates of methicillin-resistant S. aureus. In both mutants, corresponding to different lineage (ST5 and ST239), an increase of efflux activity against TIG was detected. One mutant also showed a reduced susceptibility to vancomycin, corresponding to the VISA phenotype (MIC = 4 µg/mL), with a loss of functionality of the agr locus. The emergence of the VISA phenotype was accompanied by an increase in oxacillin and cefoxitin MICs.ConclusionsThis study demonstrates that, under selective pressure, the increase of efflux activity in S. aureus is one of the mechanisms that may be involved in the emergence of tigecycline resistance. The emergence of this phenotype may eventually be associated to changes in susceptibility to other antibiotics such oxacillin and vancomycin.
Highlights
Tigecycline (TIG) is an antibiotic belonging to the glycylcyclines class and appears to be a good choice to fight infections caused by Staphylococcus aureus
*Correspondence: jdiconza@gmail.com 3 Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje “El Pozo”, CC 242, Santa Fe, Argentina Full list of author information is available at the end of the article of S. aureus have exhibited good activity of this antibiotic, with 99.9 % of isolates found to be susceptible [5]
Mutant stability was evaluated by determining the TIG minimum inhibitory concentration (MIC) after 10 consecutive passages in antibiotic-free Tryptic-Soy Agar (Britania, Argentina)
Summary
Tigecycline (TIG) is an antibiotic belonging to the glycylcyclines class and appears to be a good choice to fight infections caused by Staphylococcus aureus. *Correspondence: jdiconza@gmail.com 3 Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Ciudad Universitaria, Paraje “El Pozo”, CC 242, Santa Fe, Argentina Full list of author information is available at the end of the article of S. aureus have exhibited good activity of this antibiotic, with 99.9 % of isolates found to be susceptible [5]. The aim of this work was to select and characterize in vitro tigecycline-resistant mutants from MRSA clinical isolates.
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