Characterization of mutations in the rpoB gene associated with rifampin resistance in Rhodococcus equi isolated from foals

Citation
M. Fines et al., Characterization of mutations in the rpoB gene associated with rifampin resistance in Rhodococcus equi isolated from foals, J CLIN MICR, 39(8), 2001, pp. 2784-2787
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Clinical Immunolgy & Infectious Disease",Microbiology
Journal title
JOURNAL OF CLINICAL MICROBIOLOGY
ISSN journal
0095-1137 → ACNP
Volume
39
Issue
8
Year of publication
2001
Pages
2784 - 2787
Database
ISI
SICI code
0095-1137(200108)39:8<2784:COMITR>2.0.ZU;2-U
Abstract
Treatment with a combination of erythromycin and rifampin has considerably improved survival rates of foals and immunocompromised patients suffering f rom severe pneumonia caused by Rhodococcus equi. Frequently, because of mon otherapy, emergence of rifampin-resistant strains has been responsible for treatment failure. Using consensus oligonucleotides, we have amplified and sequenced the rifampin resistance (Rif)determining regions of 12 rifampin-r esistant R. equi strains isolated from three foals and of mutants selected in vitro from R. equi ATCC 3701, a rifampin-susceptible strain. The deduced amino acid sequences compared to those of four rifampin-susceptible R. equ i strains showed several types of mutations. In 3 of the 10 strains isolate d from one foal, His526Asn (Escherichia coli numbering) and Asp516Val mutat ions were associated with low-level resistance (rifampin MIC, 2 to 8 mug/ml ), whereas His526Asp conferred high-level resistance (rifampin MIC, 128 mug /ml) in the 7 remaining strains. In strains from the two other foals, His52 6Asp and Ser531Leu mutations were found to be associated with high-level an d low-level resistance, respectively. The in vitro mutants, highly resistan t to rifampin, harbored His526Tyr and His526Arg substitutions. As described in other bacterial genera, His526, Ser531, and Asp516 are critical residue s for rifampin resistance in R. equi, and the resistance levels are depende nt on both the location and the nature of the substitution.