Nontuberculous mycobacterium (NTM) infections are increasing globally. The Mycobacterium avium complex (MAC) and Mycobacterium abscessus are the most frequently encountered NTM among clinical laboratories, and treatment options are extremely limited.
KEYWORDS: benzimidazole, nontuberculous mycobacteria, SPR719
ABSTRACT
Nontuberculous mycobacterium (NTM) infections are increasing globally. The Mycobacterium avium complex (MAC) and Mycobacterium abscessus are the most frequently encountered NTM among clinical laboratories, and treatment options are extremely limited. In this study, the in vitro potency of a novel benzimidazole, SPR719, the microbiologically active form of the orally available prodrug SPR720, was tested against several species of NTM. MICs were determined for 161 isolates of NTM of 13 taxa (seven species, three subspecies, and three groups/complexes) in cation-adjusted Mueller-Hinton Broth, as described and recommended by the Clinical and Laboratory Standards Institute (CLSI M24-A2). Comparator antimicrobials included amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem, linezolid, minocycline, moxifloxacin, tigecycline, and trimethoprim-sulfamethoxazole (TMP-SMX) for the rapidly growing mycobacteria (RGM), amikacin and clarithromycin for the MAC, and amikacin, ciprofloxacin, clarithromycin, doxycycline, linezolid, moxifloxacin, rifabutin, rifampin, and TMP-SMX for the other slowly growing NTM. SPR719 was found to be potent against multiple clinical strains of NTM with an MIC50 range of 0.25 to 4 μg/ml for several species of NTM. These findings support the further advancement of SPR720 for the treatment of NTM disease.
INTRODUCTION
Nontuberculous mycobacterium (NTM) infections are increasing globally. These organisms, once thought to be merely environmental species, are responsible for a wide range of infections, including respiratory, cutaneous, and disseminated disease, highlighting the importance for expanding the antimicrobial armamentarium (1).
SPR719, formerly VXc-486, is a novel aminobenzimidazole which has been shown to inhibit the ATPase activity of gyrase in Mycobacterium tuberculosis (2). Initial studies have shown that this antimicrobial inhibits both drug-susceptible Mycobacterium tuberculosis and multidrug-resistant M. tuberculosis with in vitro MICs of 0.03 to 0.3 μg/ml and 0.08 to 5.48 μg/ml, respectively (2). Additional in vitro studies revealed that multiple isolates of Mycobacterium abscessus, Mycobacterium avium complex (MAC), and Mycobacterium kansasii were also inhibited, with MICs of 0.1 to 2 μg/ml (2).
(A portion of this study was presented at ASM Microbe 2018, Atlanta, GA, 6 to 11 June, 2018 [3].)
RESULTS
Of the total 161 NTM isolates tested, SPR719 MICs were 0.02 to 8 μg/ml. For all rapidly growing mycobacteria (RGM) (n = 93), the range of MIC50 values was 0.06 to 4 μg/ml, with the lowest MICs seen with the M. mucogenicum group (MIC50, 0.06 μg/ml) and the M. fortuitum group (MIC50, 0.25 μg/ml). The highest MIC50 values were seen with the isolates of M. chelonae and M. immunogenum (4 μg/ml). The largest group of RGM was the M. abscessus complex (n = 53). The MIC50 value for all three subspecies, including subspecies M. abscessus subsp. abscessus and M. abscessus subsp. massiliense and the hybrid subspecies, was 2 μg/ml (Table 1).
TABLE 1.
MIC ranges, MIC50 values, and MIC90 values of 161 isolates of 13 taxa of the nontuberculous mycobacteria against antimicrobialsa
| Antimicrobialb | M. abscessus subsp. abscessus | M. abscessus subsp. massiliense | M. abscessus/massiliense hybrid | M. chelonae | M. immunogenum | M. fortuitum group | M. mucogenicum group | M. kansasii | M. marinum | M. simiae | M. avium | M. intracellulare | MAC-X |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of isolates | 33 | 10 | 10 | 10 | 10 | 10 | 10 | 8 | 9 | 10 | 12 | 19 | 10 |
| SPR719 | |||||||||||||
| MIC range | 0.25 to 8 | 0.12 to 4 | 0.06 to 2 | 2 to 4 | 4 to 8 | 0.06 to 1 | 0.015 to 0.25 | 0.002 to 0.03 | 0.12 to 1 | 0.5 to 4 | 0.5 to 2 | 0.12 to 2 | 0.12 to 1 |
| MIC50 | 2 | 2 | 2 | 4 | 4 | 0.25 | 0.06 | 0.015 | 0.5 | 1 | 0.5 | 0.5 | 1 |
| MIC90 | 4 | 2 | 2 | 4 | 8 | 1 | 0.25 | 0.03 | 0.5 | 2 | 2 | 2 | 1 |
| AMK | |||||||||||||
| MIC range | 2 to 64 | 4 to 16 | 8 to 16 | 16 to 32 | 8 to 16 | ≤1 | ≤1 | 2 to 8 | ≤1 to 2 | 8 to 32 | 8 to >64 | 8 to >64 | 8 to 32 |
| MIC50 | 8 | 16 | 16 | 16 | 8 | ≤1 | ≤1 | 4 | ≤1 | 16 | 16 | 16 | 8 |
| MIC90 | 16 | 16 | 16 | 32 | 16 | ≤1 | ≤1 | 8 | 2 | 16 | 64 | >64 | 32 |
| FOX | |||||||||||||
| MIC range | 16 to 64 | 32 to 64 | 32 to 64 | >128 | >128 | 32 to 64 | ≤4 to 16 | ||||||
| MIC50 | 64 | 64 | 32 | >128 | >128 | 64 | 8 | ||||||
| MIC90 | 64 | 64 | 64 | >128 | >128 | 64 | 16 | ||||||
| SXT | |||||||||||||
| MIC range | 4/76 to 8/152 | 4/76 to 8/152 | 4/76 to 8/152 | ≤2/38 to >4/76 | 2/38 to 8/152 | ≤0.25/4.75 to 1/19 | ≤0.25/4.75 to 0.5/9.5 | ≤0.12 to 0.25/4.75 | ≤0.25/4.75 to 1/19 | 1/19 to 4/76 | |||
| MIC50 | 4/76 | 4/76 | 4/76 | ≥4/76 | 4/76 | 0.5/9.5 | ≤0.25/4.75 | 0.25/4.75 | 0.5/9.5 | 2/38 | |||
| MIC90 | 8/152 | 8/152 | 8/152 | ≥4/76 | 8/152 | 1/19 | 0.5/9.5 | 0.25/4.75 | 1/19 | 4/76 | |||
| LZD | |||||||||||||
| MIC range | 2 to 32 | 2 to 16 | 2 to 16 | 2 to 16 | 4 to 32 | ≤1 to 8 | ≤1 to 4 | ≤1 to 4 | ≤1 to 2 | 16 to >64 | 2 to 64 | 8 to >64 | 8 to 64 |
| MIC50 | 8 | 8 | 8 | 8 | 16 | 2 | ≤1 | ≤1 | 2 | 32 | 32 | 32 | 32 |
| MIC90 | 16 | 16 | 16 | 16 | 32 | 4 | 4 | 4 | 2 | 64 | 64 | 64 | 64 |
| CIP | |||||||||||||
| MIC range | 2 to >4 | ≥4 | 4 to >4 | 2 to >4 | 2 to 8 | ≤0.12 | 0.25 to 4 | 2 to 4 | 1 to 16 | 4 to >16 | |||
| MIC50 | >4 | 4 | 4 | 4 | 4 | ≤0.12 | 0.5 | 4 | 8 | 8 | |||
| MIC90 | >4 | >4 | >4 | >4 | 8 | ≤0.12 | 2 | 4 | 16 | >16 | |||
| IPM | |||||||||||||
| MIC range | 8 to 64 | 4 to 32 | 8 to 32 | 16 to 64 | 16 to 64 | 4 to 8 | ≤2 | ||||||
| MIC50 | 16 | 8 | 16 | 16 | 32 | 4 | ≤2 | ||||||
| MIC90 | 32 | 16 | 32 | 32 | 64 | 8 | ≤2 | ||||||
| MXF | |||||||||||||
| MIC range | 2 to >8 | 2 to >8 | 4 to 8 | 4 to >8 | 4 to 8 | ≤0.25 | ≤0.25 to 1 | ≤0.12 to 0.5 | 0.25 to 4 | 1 to 8 | 0.5 to >8 | 1 to >8 | 0.5 to >8 |
| MIC50 | 8 | 8 | 4 | 4 | 4 | ≤0.25 | ≤0.25 | ≤0.12 | 1 | 4 | 1 | 4 | 4 |
| MIC90 | >8 | >8 | >8 | 8 | 8 | ≤0.25 | 0.5 | 0.5 | 4 | 8 | 8 | 8 | >8 |
| DOX | |||||||||||||
| MIC range | >8 | 2 to >16 | >16 | 0.12 to >16 | 8 to >16 | 0.12 to >16 | ≤0.12 to >16 | 1 to 16 | 2 to 16 | ≥16 | |||
| MIC50 | >8 | >16 | >16 | >16 | >16 | 0.25 | ≤0.12 | 8 | 2 | ≥16 | |||
| MIC90 | >8 | >16 | >16 | >16 | >16 | >16 | >16 | 16 | 16 | >16 | |||
| MIN | |||||||||||||
| MIC range | >16 | 4 to >8 | >8 | ≤1 to >8 | >8 | ≤1 to >8 | ≤1 to >8 | ||||||
| MIC50 | >16 | 8 | >8 | >8 | >8 | ≤1 | ≤1 | ||||||
| MIC90 | >16 | >8 | >8 | >8 | >8 | >8 | >8 | ||||||
| TGC | |||||||||||||
| MIC range | 0.06 to 0.5 | 0.06 to 0.5 | 0.06 to 0.25 | 0.06 to 0.5 | 0.06 to 0.25 | 0.03 to 0.12 | ≤0.25 to 0.25 | ||||||
| MIC50 | 0.25 | 0.12 | 0.25 | 0.25 | 0.12 | 0.06 | 0.12 | ||||||
| MIC90 | 0.5 | 0.5 | 0.5 | 0.5 | 0.25 | 0.12 | 0.25 | ||||||
| CLR | |||||||||||||
| MIC range | ≤2 to >16 | ≤2 | 0.12 to 0.25 | ≤2 | ≤2 | ≤0.06 to >16 | ≤2 | 0.12 to 0.5 | 0.5 to 2 | 8 to >64 | 0.25 to >64 | 1 to >64 | 0.5 to 8 |
| MIC50 | ≥16 | ≤2 | 0.06 | ≤2 | ≤2 | 16 | ≤2 | 0.25 | 1 | 8 | 2 | 2 | 2 |
| MIC90 | ≥16 | ≤2 | 0.5 | ≤2 | ≤2 | >16 | ≤2 | 0.5 | 2 | 32 | 8 | >64 | 4 |
| TOB | |||||||||||||
| MIC range | ≤1 to 4 | 8 to 16 | |||||||||||
| MIC50 | ≤2 | 8 | |||||||||||
| MIC90 | ≤2 | 16 | |||||||||||
| RFB | |||||||||||||
| MIC range | ≤0.25 | ≤0.25 | 4 to >8 | ||||||||||
| MIC50 | ≤0.25 | ≤0.25 | 8 | ||||||||||
| MIC90 | ≤0.25 | ≤0.25 | >8 | ||||||||||
| RIF | |||||||||||||
| MIC range | ≤0.12 to 1 | 0.5 to 1 | >8 | ||||||||||
| MIC50 | 0.25 | 0.5 | >8 | ||||||||||
| MIC90 | 1 | 1 | >8 |
All values shown are in μg/ml.
Amk, amikacin; FOX, cefoxitin; SXT, trimethoprim–sulfamethoxazole; LZD, linezolid; CIP, ciprofloxacin; IPM, imipenem; MXF, moxifloxacin; DOX, doxycycline; MIN, minocycline; TGC, tigecycline; CLR, clarithromycin; TOB, tobramycin; RFB, rifabutin, RIF, rifampin.
Among the slowly growing mycobacteria (SGM) (n = 68), the range of MIC50 values was 0.002 to 4 μg/ml. The lowest MICs were seen with the isolates of M. kansasii (0.002 to 0.015 μg/ml); the highest MIC50 values were seen with isolates of M. simiae and the Mycobacterium avium complex X (MAC-X) (each species, 1 μg/ml). Among the 41 isolates of the MAC, SPR719 MIC90 values were ≤2 μg/ml, and the MIC50 values were ≤1 μg/ml (Table 1).
Interestingly, isolates intrinsically resistant to ciprofloxacin and moxifloxacin (e.g., those of M. abscessus complex) had an MIC50 value of 2 μg/ml for SPR719, in contrast to the MIC50 value of ≥4 μg/ml for both ciprofloxacin and moxifloxacin.
Most SPR719 MIC50 values were equivalent to or at least 1 dilution less than the MIC50 values for ciprofloxacin and moxifloxacin. All other MICs for the comparator agent were within expected ranges for the species/subspecies tested (Table 1).
Quality control.
The manufacturer's acceptable range of MICs for Staphylococcus aureus ATCC 29213 with SPR719 was ≤0.015 to 0.12 μg/ml, but it was based on a limited number of runs (n = 5). All 43 replicates of S. aureus ATCC 29213 tested had an SPR719 MIC within the acceptable range (Table 2). Each quality control for the comparator agents was within the CLSI acceptable range for M. peregrinum ATCC 700686, M. marinum ATCC 927, S. aureus ATCC 29213, and E. faecalis ATCC 2912.
TABLE 2.
MICs and MIC ranges of reference strains tested against SPR719
| Reference strain | MIC range (μg/ml) | No. of values at an MIC (μg/ml) of: |
|||||||
|---|---|---|---|---|---|---|---|---|---|
| <0.008 | 0.015 | 0.03 | 0.06 | 0.12 | 0.25 | 0.5 | 1 | ||
| Staphylococcus aureus ATCC 29213 | <0.008 to 0.12 | 26 | 14 | 1 | 1 | 1 | 0 | 0 | 0 |
| Mycobacterium peregrinum ATCC 700686 | 0.12 to 0.5 | 0 | 0 | 0 | 0 | 1 | 11 | 5 | 0 |
| Mycobacterium marinum ATCC 927 | 0.06 to 0.5 | 0 | 0 | 0 | 10 | 7 | 1 | 5 | 0 |
| Escherichia coli ATCC 25922 | 0.5 to 1 | 0 | 0 | 0 | 0 | 0 | 0 | 14 | 2 |
| Enterococcus faecalis ATCC 29212 | 0.015 | 0 | 11 | 0 | 0 | 0 | 0 | 0 | 0 |
Seventeen replicates of M. peregrinum ATCC 700686 had an MIC range for SPR719 of 0.12 to 0.5 μg/ml (mode, 0.25 μg/ml), while 23 replicates of M. marinum ATCC 927 had an MIC range of 0.06 to 0.5 μg/ml (mode, 0.06 μg/ml) (experiments were performed weekly). The additional bacterial reference strains E. coli ATCC 25922 (16 replicates) and E. faecalis ATCC 29212 (11 replicates) had an SPR719 MIC range of 0.5 to 1 μg/ml (modes, 0.5 μg/ml and 0.015 μg/ml, respectively) (Table 2).
DISCUSSION
SPR719 (previously VXc-486) is a novel aminobenzimidazole, which is a class of gyrase inhibitors that target the ATPase subunits, resulting in growth inhibition of M. tuberculosis (2). This compound was previously reported to be active against M. kansasii and M. tuberculosis in a murine model (2).
Importantly, no cross-resistance to the fluoroquinolone class of gyrase inhibitors, including moxifloxacin, has been reported, even in fluoroquinolone-resistant isolates (e.g., from extremely drug-resistant [XDR] M. tuberculosis, which is resistant to fluoroquinolones). The compound is slowly bactericidal for M. tuberculosis, achieving a ≥3-fold reduction in CFU (MIC, 0.06 μg/ml) after 14 days, and slow killing of M. tuberculosis against actively growing cells of M. tuberculosis strain Erdman (2). Additionally, SPR719 has shown activity against drug-susceptible strains of M. tuberculosis in an in vitro model of quiescent mycobacterial survival and was more active than moxifloxacin and gatifloxacin (2).
SPR719 also inhibits the growth of strain H37Ra cultured in human and mouse macrophage-like cell lines. Docking studies using the published crystal structure of the M. tuberculosis gyrase B were used to produce a three-dimensional model of SPR719 interaction or binding. The predicted binding was consistent with experimental studies reported for closely related compounds in complex with the gyrase B enzyme from Staphylococcus aureus, suggesting that the compound binds to gyrase B by altering the hydrogen bonding network and destabilizing the catalytic water present in the active sites (2).
Locher and colleagues also showed the potency of the compound against a small number of M. abscessus, M. avium, M. kansasii, and Nocardia spp. (2). The investigators reported the compound's bactericidal activity against M. kansasii.
The SPR719 MIC50 values of our clinical isolates of NTM in the current study were comparable to those from the preliminary studies by Locher et al. (2). However, the SPR719 MIC50 for all M. abscessus complex isolates in this study (n = 53) was 2 μg/ml compared with 1 μg/ml in the Locher et al. study (n = 22; the Locher et al. study did not differentiate subspecies of the M. abscessus complex). In this study, 33 isolates were M. abscessus subsp. abscessus and 20 isolates were M. abscessus subsp. massiliense or M. abscessus subsp. abscessus/M. abscessus subsp. massiliense hybrid [i.e., M. abscessus subsp. abscessus by sequencing of the rpoβ gene and M. abscessus subsp. massiliense by sequencing of the erm(41) gene].
For the MAC isolates in our study (n = 41, including 12 M. avium, 19 M. intracellulare, and 10 MAC-X strains), the SPR719 MIC50 range was 0.5 to 1.0 μg/ml, 1 to 2 dilutions higher than the MIC50 of 0.23 μg/ml seen in the initial study (n = 3, but only M. avium was tested). In contrast, the 8 isolates of M. kansasii in this study had an SPR719 MIC50 value of 0.015 μg/ml compared with the 22 isolates (including two reference strains) in the Locher et al. study that had an MIC50 value of 0.06 μg/ml (2).
Studies by Shoen et al. showed the efficacy of the prodrug SPR720 in a chronic murine M. tuberculosis infection model with the hypothesis that SPR720 may shorten the duration of treatment for drug-susceptible M. tuberculosis and serve as a potent addition to oral regimens to shorten the length of treatment for multidrug-resistant tuberculosis (MDR-TB) (7). In a 2017 report by Rubio et al., SPR720 (prodrug of SPR719) significantly reduced the mycobacterial burden in the lungs, spleen, and liver of severe combined immunodeficiency (SCID) mice acutely infected with M. abscessus subsp. bolletii (strain 103) after oral dosing of 200, 300, and 400 mg/kg/day after 8 days (8). A subsequent study by Rubio et al., showed the efficacy of SPR720 in a mouse model after oral dosages of 25 to 400 mg/kg/day after 16 days. A daily dosage of 100 mg/kg demonstrated the greatest reduction in bacterial burden of M. abscessus in lung, spleen, and liver compared with that in the control group (9). Another 2018 study by Bermudez et al. showed activity of SPR719/720 in strains of “M. avium subsp. hominissuis” in macrophages, mice, and biofilms (10). The most efficacious regimen with the lowest average organism burden in the lung and the largest number of animals showing clearance of the MAC in the lungs was seen at a daily dosage of 50 mg/kg.
These previous studies along with our study suggest that this compound may be a welcome addition to both the M. tuberculosis and NTM treatment arsenal. Further clinical studies to assess the role and efficacy of SPR720 in drug treatment of NTM infections are warranted.
MATERIALS AND METHODS
Isolates.
The 161 isolates of NTM submitted to the Mycobacteria/Nocardia Research Laboratory at the University of Texas Health Science Center at Tyler between 2016 and 2018 were tested against SPR719 and other comparative antimicrobials (Table 1). One hundred twenty-three (76%) of the isolates were of respiratory origin, while the remaining 38 isolates (24%) were from skin, soft tissue, blood, and fluids.
The rapidly growing mycobacteria (RGM) belonging to 13 taxa of RGM and slowly growing mycobacteria (SGM) included 33 strains from M. abscessus subsp. abscessus, 10 from M. abscessus subsp. massiliense, 10 from M. abscessus subsp. abscessus/M. abscessus subsp. massiliense hybrids (identified as M. abscessus subsp. massiliense by erm gene but M. abscessus subsp. abscessus by rpoβ gene), 10 from M. chelonae, 10 from M. immunogenum, 10 from the Mycobacterium fortuitum group, and 10 from the Mycobacterium mucogenicum group. The SGM strains included 10 from Mycobacterium simiae, 9 from Mycobacterium marinum, 8 from M. kansasii, 12 from Mycobacterium avium, 19 from Mycobacterium intracellulare, and 10 from MAC-X species (including Mycobacterium chimaera).
Identification.
All isolates of NTM were identified by gene sequencing as indicated for each species/group. For the RGM, sequencing of region 5 of the rpoβ gene and the erm(41) gene (for the M. abscessus complex) was performed using previously recommended criteria for identification, including CLSI recommendations (4, 5). The SGM species were identified using partial 16S rRNA gene sequencing along with the CLSI interpretive criteria (4).
Antimicrobial susceptibility testing.
Isolates were tested by broth microdilution in cation-adjusted Mueller-Hinton broth using doubling dilutions of antimicrobials (SPR719 concentrations were 0.008 to 16 μg/ml for RGM and SGM in one set of panels and 0.0002 to 64 μg/ml and 0.0002 to 512 μg/ml in another lot of panels for RGM and SGM, provided by Spero Therapeutics as frozen panels manufactured by Thermo Fisher). MICs for the RGM were read after incubation at 30°C for 3 to 5 days until sufficient growth was evident in the growth control well. The slowly growing NTM were read after incubation at 35°C for 7 to 14 days when sufficient growth was evident in the growth control wells. SPR719 was insoluble at high concentrations (≥32 μg/ml), and, therefore, the MICs of concentrations above this level were not possible. MIC50 was defined as the lowest concentration of the antibiotic at which 50% of the isolates were inhibited.
The comparator antimicrobials included amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem, linezolid, minocycline, moxifloxacin, tigecycline, trimethoprim-sulfamethoxazole (TMP-SMX), and tobramycin (for M. chelonae and M. immunogenum) for the RGM. For the SGM (except the MAC), the antimicrobials included amikacin, ciprofloxacin, clarithromycin, doxycycline, linezolid, moxifloxacin, rifabutin, rifampin, and TMP-SMX. The comparator antimicrobials for MAC included amikacin, clarithromycin, linezolid, and moxifloxacin, as recommended by the Clinical and Laboratory Standards Institute (CLSI) (6). The CLSI-recommended breakpoints are listed in Table 1 (6). All comparator antimicrobial MICs were read on commercial microtiter readers (RAPMYCO and SLOMYCO panels) manufactured by Thermo Fisher.
Quality control.
Quality control of susceptibility testing was performed weekly using the CLSI-recommended strains Mycobacterium peregrinum ATCC 700686 (RGM) and M. marinum ATCC 927 (SGM) for the comparative antimicrobials and Staphylococcus aureus ATCC 29213, as recommended by the manufacturer for SPR719. In search for an alternative quality control strain, additional quality control for SPR179 was performed using Escherichia coli ATCC 25922 and Enterococcus faecalis ATCC 29212 and the abovementioned mycobacterial reference strains (Table 2).
ACKNOWLEDGMENTS
We thank Spero Therapeutics for funding this study.
We also thank the mycobacterial molecular identification team at the University of Texas Health Science Center at Tyler, including Ravikiran Vasireddy, Sruthi Vasireddy, Adrian Almodovar, Elena Iakhiaeva, and Terry Smith, for sequencing the isolates and Megan Ashcraft, Georgie Bush, Amber McKinney, and Kelly Ritter for susceptibility testing. We also thank Katie Shipp and Jacob Mooney for data formatting and strain maintenance and Joanne Woodring for her excellent clerical support.
REFERENCES
- 1.Brown-Elliott BA, Nash KA, Wallace RJ Jr. 2012. Antimicrobial susceptibility testing, drug resistance mechanisms, and therapy of infections with nontuberculous mycobacteria. Clin Microbiol Rev 25:545–582. doi: 10.1128/CMR.05030-11. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Locher CP, Jones SM, Hanzelka BL, Perola E, Shoen CM, Cynamon MH, Ngwane AH, Wiid IJ, van Helden PD, Betoudji F, Nuermberger EL, Thomson JA. 2015. A novel inhibitor of gyrase B is a potent drug candidate for treatment of tuberculosis and nontuberculosis mycobacterial infections. Antimicrob Agents Chemother 59:1455–1465. doi: 10.1128/AAC.04347-14. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Brown-Elliott BA, Ashcraft M, Bush G, McKinney A, Ritter K, Shipp K, Mooney J, Wallace RJ Jr, Rubio A. 2018. In vitro characterization of a novel gyrase inhibitor (SPR719) against nontuberculous mycobacteria, ASM Microbe, Atlanta, GA. [Google Scholar]
- 4.Clinical and Laboratory Standards Institute. 2008. Interpretive criteria for identification of bacteria and fungi by DNA target sequencing; approved guideline. CLSI document MM18-A. Clinical and Laboratory Standards Institute, Wayne, PA. [Google Scholar]
- 5.Adékambi T, Colson P, Drancourt M. 2003. rpo B-based identification of nonpigmented and late pigmented rapidly growing mycobacteria. J Clin Microbiol 41:5699–5708. doi: 10.1128/JCM.41.12.5699-5708.2003. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Clinical and Laboratory Standards Institute. 2011. Susceptibility testing of Mycobacteria, Nocardiae, and other aerobic Actinomycetes: approved Standard, 2nd edition Document no. M24–A2 Clinical and Laboratory Standards Institute, Wayne, PA. [PubMed] [Google Scholar]
- 7.Shoen C, Pucci MJ, DeStefano M, Cynamon M. 2017. Efficacy of SPR 720 and SPR 750 gyrase inhibitors in a mouse Mycobacterium tuberculosis infection model, ASM Microbe 2017, New Orleans, LA. [Google Scholar]
- 8.Rubio A, Verma D, Ordway D, Pucci MJ, Parr TR Jr. 2017. Activity of a novel gyrase inhibitor in vitro and in an acute SCID mouse model of infection caused by Mycobacterium abscessus. ASM Microbe 2017, New Orleans, LA. [Google Scholar]
- 9.Rubio A, Stapleton M, Verman D, Ordway D. 2018. Potent activity of a novel gyrase inhibitor (SPR719/720) in vitro and in a prolonged acute Mycobacterium abscessus mouse model of infection, ASM Microbe 2018, Atlanta, GA. [Google Scholar]
- 10.Bermudez LE, Palmer A, Rubio A. 2018. Treatment of Mycobacterium avium subspecies hominissuis (MAH) infection with a novel gyrase inhibitor (SPR719/SPR720) was associated with a significant decrease in bacterial load as assessed in macrophages, biofilm and in mice, ASM Microbe 2018, Atlanta, GA. [Google Scholar]