Characterization of Mutations in the
            <i>rpoB</i>
            Gene Associated with Rifampin Resistance in
            <i>Rhodococcus equi</i>
            Isolated from Foals

Fines, Marguerite; Pronost, Stéphane; Maillard, Karine; Taouji, Saı̈d; Leclercq, Roland

doi:10.1128/jcm.39.8.2784-2787.2001

Cited by 55 publications

(47 citation statements)

References 20 publications

(16 reference statements)

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“…A mutation in the rpoB gene (codon 526, His526Asp) associated with rifampin resistance was confirmed by partial sequencing (6). An A-to-G mutation at position 2063 in domain V of the 23S rRNA gene of R. equi resulted in the high-level macrolide resistance of the isolated strains (7).…”

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confidence: 92%

Appearance of Multidrug-Resistant Virulent Rhodococcus equi Clinical Isolates Obtained in China

et al. 2014

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Rhodococcus equi is a major cause of pneumonia in domestic animals, especially foals, and an opportunistic pathogen of immunocompromised humans (1). Control of R. equi infections in horses has relied on early detection of subclinical pulmonary disease and treatment with antimicrobial drugs before development of clinical signs (2). However, the onset of clinical signs of R. equi pneumonia in foals is often insidious, and delay in diagnosis and treatment tends to increase the morbidity and mortality. The combination of erythromycin and rifampin has been the treatment of choice since the 1980s and has improved survival rates considerably (3,4). In China, data on the antimicrobial sensitivity of R. equi are sparse. In the present study, an R. equi strain isolated from a racehorse in China was found to be multidrug resistant.From June through August 2013, 108 (20%) of 903 horses showed symptoms of pneumonia on an English thoroughbred racehorse breeding farm in Beijing, China. They were treated by injection with erythromycin, ampicillin, and ceftiofur for 1 month, but the treatment was unsuccessful. Thirty-eight horses (35.2%) aged 1.5 to 3 months died of pneumonia, and postmortem examination revealed multiple pyogranulomas in all regions of the lungs. The 152 samples, including trachea secretions and tissues of lung, liver, and intestine, were collected under aseptic conditions and plated on Trypticase soy agar supplemented with 5% sheep blood. R. equi was isolated from 76 (50%) of 152 samples and identified by the Phoenix 100 identification system (BD, USA).According to a nucleotide-by-nucleotide GenBank search by using BLAST (http://blast.ncbi.nlm.nih.gov/), the 16S rRNA gene sequence of the isolated strain was 100% identical to the sequences of 16S rRNA genes of R. equi. Further confirmation of R. equi was accomplished by amplification of the choE gene and detection of the virulence plasmid by amplification of the vapA gene by using multiplex PCR (5).The susceptibilities of the strain to erythromycin, clarithromycin, azithromycin, and rifampin were determined with the Phoenix 100 antimicrobial susceptibility testing system (BD, USA). In accordance with CLSI guidelines, the virulent R. equi strain was considered resistant to macrolides and rifampin, with MIC values of Ն25 g/ml (azithromycin, clarithromycin, and erythromycin) and Ն128 g/ml (rifampin).To determine whether macrolide and rifampin resistance was caused by mutations in the V domain, we amplified and sequenced the 23S rRNA gene and rpoB gene of the R. equi isolate. A mutation in the rpoB gene (codon 526, His526Asp) associated with rifampin resistance was confirmed by partial sequencing (6). An A-to-G mutation at position 2063 in domain V of the 23S rRNA gene of R. equi resulted in the high-level macrolide resistance of the isolated strains (7). DNA sequencing results were compared to the GenBank sequences of the R. equi reference strain ATCC 33701.Our finding that the isolated strain from a racehorse breeding farm was resistant to macrolides and rifampin ...

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Appearance of Multidrug-Resistant Virulent Rhodococcus equi Clinical Isolates Obtained in China

et al. 2014

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“…PCR and DNA sequencing in the rpoB gene were performed for eight R. equi isolates from eight AIDS patients with pneumonia or lung abscess caused by R. equi between 1998 and 2001 as described previously (5). A set of primers, MF (5Ј-CGACCACTTCGGCAACCG-3Ј) and MR (5Ј-T CGATCGGGCACATCCGG-3Ј), was chosen to amplify a portion of the rpoB region of R. equi that includes the rifampin resistance-determining region.…”

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confidence: 99%

“…However, the emergence of rifampin resistance in R. equi has been reported (10,17), although it is still rare. Recently, Fines et al reported that several mutations in the rpoB gene are associated with rifampin resistance in R. equi isolated from foals, as well as in Mycobacterium tuberculosis, Escherichia coli, and Staphylococcus aureus (5).…”

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Emergence of Rifampin-Resistant Rhodococcus equi with Several Types of Mutations in the rpoB Gene among AIDS Patients in Northern Thailand

et al. 2003

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The antimicrobial susceptibilities of 30 Rhodococcus equi isolates obtained from 30 patients between 1993 and 2001 in northern Thailand were investigated. The MICs showed a tendency toward resistance to various antibiotics but sensitivity to imipenem, minocycline, vancomycin, and teicoplanin (MICs, <0.5 g/ml) and relative sensitivity to meropenem, clarithromycin, and ciprofloxacin (MICs, <2 g/ml). Of the 30 isolates, 26 were susceptible (MICs, <1 g/ml), 1 showed low-level resistance (MIC, 8 g/ml), and 3 showed high-level resistance (MICs, >64 g/ml) to rifampin. PCR amplification and DNA sequencing of the rpoB gene and molecular typing by pulsed-field gel electrophoresis (PFGE) were performed for eight R. equi isolates from eight AIDS patients with pneumonia or lung abscess caused by R. equi between 1998 and 2001, including one low-and three highlevel rifampin-resistant isolates. As a result, two high-level rifampin-resistant strains with PFGE pattern A had a Ser531Trp (Escherichia coli numbering) mutation, and one high-level rifampin-resistant strain with PFGE pattern B had a His526Tyr mutation, whereas one low-level rifampin-resistant strain with PFGE pattern C had a Ser509Pro mutation. Four rifampin-susceptible strains with PFGE patterns D and E showed an absence of mutation in the rpoB region. Our results indicate the presence of several types of rifampin-resistant R. equi strains among AIDS patients in northern Thailand.

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“…A combination of rifampin and erythromycin remains the treatment of choice for foals, but no optimal drug regimen has been established for human infections and relapse is a significant problem (52). Moreover, rifampin-resistant phenotypes of R. equi have been identified (1,12,49), and the use of erythromycin in foals may have side effects (13, 46). There thus remains a need to identify physiological features of R. equi that contribute to the ability of this organism to thrive within macrophages and which might provide targets for the implementation of novel therapeutic strategies.…”

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The Cell Wall of the Pathogenic Bacterium Rhodococcus equi Contains Two Channel-Forming Proteins with Different Properties

et al. 2003

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We have identified in organic solvent extracts of whole cells of the gram-positive pathogen Rhodococcus equi two channel-forming proteins with different and complementary properties. The isolated proteins were able to increase the specific conductance of artificial lipid bilayer membranes made from phosphatidylcholine-phosphatidylserine mixtures by the formation of channels able to be permeated by ions. The channel-forming protein PorA Req (R. equi pore A) is characterized by the formation of cation-selective channels, which are voltage gated. PorA Req has a single-channel conductance of 4 nS in 1 M KCl and shows high permeability for positively charged solutes because of the presence of negative point charges. According to the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the protein has an apparent molecular mass of about 67 kDa. The analysis (using the effect of negative charges on channel conductance) of the concentration dependence of the single-channel conductance suggested that the diameter of the cell wall channel is about 2.0 nm. The second channel (formed by PorB Req [R. equi pore B]) shows a preferred movement of anions through the channel and is not voltage gated. This channel shows a single-channel conductance of 300 pS in 1 M KCl and is characterized by the presence of positive point charges in or near the channel mouth. Based on SDS-PAGE, the apparent molecular mass of the channel-forming protein is about 11 kDa. Channel-forming properties of the investigated cell wall porins were compared with those of others isolated from mycolic acid-containing actinomycetes. We present here the first report of a fully characterized anion-selective cell wall channel from a member of the order Actinomycetales.Rhodococcus equi (formerly Corynebacterium equi) is recognized as a significant cause of disease in foals between the ages of 1 and 6 months and is responsible for ca. 3% of global foal mortality (13,33). This organism was first reported as a cause of human disease in 1967 (14), since which time it has emerged as an opportunistic pathogen, notably (but not exclusively) of patients with compromised immunity (25,27,33,52). Moreover, it is likely that the incidence of human infection by R. equi has been underestimated through either misdiagnosis or unwarranted dismissal of the organism as a contaminant diphtheroid (52).In both foals and humans, R. equi disease is typically characterized by bronchopneumonia, although extrapulmonary manifestations are also found (13, 33, 52). R. equi is an intracellular pathogen of alveolar macrophages, and the bacterium is known to enter macrophages via complement receptors following deposition of complement component C3 (25). Once within the macrophage, the bacteria resist the host's killing mechanisms and multiply. However, there is currently little information concerning the specific bacterial factors which facilitate entry into or subsequent survival within macrophages. Persistence within macrophages most likely contributes to the in vivo ...

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Characterization of Mutations in the rpoB Gene Associated with Rifampin Resistance in Rhodococcus equi Isolated from Foals

Cited by 55 publications

References 20 publications

Appearance of Multidrug-Resistant Virulent Rhodococcus equi Clinical Isolates Obtained in China

Appearance of Multidrug-Resistant Virulent Rhodococcus equi Clinical Isolates Obtained in China

Emergence of Rifampin-Resistant Rhodococcus equi with Several Types of Mutations in the rpoB Gene among AIDS Patients in Northern Thailand

The Cell Wall of the Pathogenic Bacterium Rhodococcus equi Contains Two Channel-Forming Proteins with Different Properties

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