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Nationwide surveillance of antimicrobial susceptibility of 509 rapidly growing mycobacteria strains isolated from clinical specimens in Japan.

ABSTRACT: This study aimed to identify effective treatments against rapidly growing mycobacteria (RGM) infections by investigating the minimum inhibitory concentrations (MIC) of 24 antimicrobial agents and their molecular mechanisms of resistance. In total, 509 clinical RGM isolates were identified by analyzing the sequences of three housekeeping genes (hsp65, rpoB, and sodA), and their susceptibilities to 24 antimicrobial agents were tested. We also performed sequencing analysis of antimicrobial resistance genes (rrl, rrs, gyrA, and gyrB). To identify Mycobacteroides abscessus group subspecies, we performed PCR-based typing and determined the sequevar of erm(41). We identified 15 RGM species, most of which were susceptible to amikacin and linezolid. Among these species, arbekacin and sitafloxacin had the lowest MIC among the same class of antimicrobials. The MIC of rifabutin for M. abscessus subsp. abscessus (MAB) was lower than that for M. abscessus subsp. massiliense (MMA). The proportion of MAB isolates with MIC ≤ 2 mg/L for rifabutin was significantly higher than that of MMA [MAB: 50/178 (28.1%) vs. MMA: 23/130 (17.7%); p = 0.041]. In summary, our study revealed the antimicrobial susceptibility profile of 15 RGM species isolated in Japan and indicated that arbekacin, sitafloxacin, and rifabutin may be possible therapeutic options for RGM infections.

SUBMITTER: Kamada K

PROVIDER: S-EPMC8190260 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Nonpigmented and late-pigmenting rapidly growing mycobacteria (RGM) are increasingly isolated in clinical microbiology laboratories. Their accurate identification remains problematic because classification is labor intensive work and because new taxa are not often incorporated into classification databases. Also, 16S rRNA gene sequence analysis underestimates RGM diversity and does not distinguish between all taxa. We determined the complete nucleotide sequence of the rpoB gene, which encodes the bacterial beta subunit of the RNA polymerase, for 20 RGM type strains. After using in-house software which analyzes and graphically represents variability stretches of 60 bp along the nucleotide sequence, our analysis focused on a 723-bp variable region exhibiting 83.9 to 97% interspecies similarity and 0 to 1.7% intraspecific divergence. Primer pair Myco-F-Myco-R was designed as a tool for both PCR amplification and sequencing of this region for molecular identification of RGM. This tool was used for identification of 63 RGM clinical isolates previously identified at the species level on the basis of phenotypic characteristics and by 16S rRNA gene sequence analysis. Of 63 clinical isolates, 59 (94%) exhibited <2% partial rpoB gene sequence divergence from 1 of 20 species under study and were regarded as correctly identified at the species level. Mycobacterium abscessus and Mycobacterium mucogenicum isolates were clearly distinguished from Mycobacterium chelonae; Mycobacterium mageritense isolates were clearly distinguished from "Mycobacterium houstonense." Four isolates were not identified at the species level because they exhibited >3% partial rpoB gene sequence divergence from the corresponding type strain; they belonged to three taxa related to M. mucogenicum, Mycobacterium smegmatis, and Mycobacterium porcinum. For M. abscessus and M. mucogenicum, this partial sequence yielded a high genetic heterogeneity within the clinical isolates. We conclude that molecular identification by analysis of the 723-bp rpoB sequence is a rapid and accurate tool for identification of RGM.

Project description:Some naturally occurring compounds, known for their antimicrobial activities, have been employed as food additives. However, their efficacy in treating infections caused by antibiotic-resistant bacteria is yet to be fully explored. Rapidly growing mycobacteria (RGM), a category within nontuberculous mycobacteria (NTM), are prevalent in various environments and can lead to infections in humans. The rise of antimicrobial resistance within RGM is a documented concern. In this study, we reported that four specific natural compounds effectively inhibited the growth and biofilm formation of three key RGM pathogens M. abscessus, M. fortuitum, and M. chelonae. We screened 12 natural compounds for their effectiveness against antibiotic-resistant clinical strains of RGM. Four compounds showed significant inhibitory effects from the most effective to least: trans-cinnamaldehyde, carvacrol, gentisaldehyde, and phloroglucinaldehyde. In the analysis of time-killing kinetics, gentisaldehyde and phloroglucinaldehyde displayed bactericidal activity while trans-cinnamaldehyde and carvacrol exhibited bacteriostatic effects. At 1× minimal inhibition concentrations, these compounds significantly reduced biofilm formation in all three RGM species to levels between 2.9% and 20.5% relative to controls. Checkerboard assays indicated synergistic interactions between these four compounds and antibiotics such as amikacin, clarithromycin, and linezolid. Of these 12 compound-antibiotic combinations, the pairs of carvacrol-linezolid, carvacrol-amikacin, and gentisaldehyde-clarithromycin demonstrated the most synergy against multiple RGM strains. Moreover, two other compounds citral and geraniol showed synergism with all three test antibiotics. Time-killing assays further confirmed most of synergistic combinations identified in the checkerboard tests. Our research suggests the potential of these essential oils and phenolic aldehydes, both individually and in combination with antibiotics, in treating RGM infections. In addition, this work illuminates applications of these natural compounds in environmental remediation to mitigate bacterial persistence for the control of infectious diseases.ImportanceThe emergence of antimicrobial resistance within rapidly growing mycobacteria (RGM) poses a significant threat to public health. This study investigates the potential of naturally occurring compounds to combat infections caused by antibiotic-resistant RGM including M. abscessus, M. fortuitum, and M. chelonae. We identified four specific natural compounds showing impressive inhibitory effects against antibiotic-resistant clinical strains. These compounds not only inhibited the growth and biofilm formation but also exhibited synergistic interactions with antibiotics against key RGM pathogens. Our findings highlight the alternative treatment strategies for RGM infections and potential environmental applications of these natural compounds in mitigating microbial persistence and controlling infectious diseases.

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Nationwide surveillance of antimicrobial susceptibility of 509 rapidly growing mycobacteria strains isolated from clinical specimens in Japan.

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