Low-level antibacterial resistance: a gateway to clinical resistance

Antibiotic resistance is on the rise and has become one of the biggest public health challenges of our time. Bacteria are able to adapt to the selective pressure exerted by antibiotics in numerous ways, including the (over)expression of efflux pumps, which represents an ancient bacterial defense mechanism. Several studies show that overexpression of efflux pumps rarely provides clinical resistance but contributes to a low-level resistance, which allows the bacteria to persist at the infection site. Furthermore, recent studies show that efflux pumps, apart from pumping out toxic substances, are also linked to persister formation and increased spontaneous mutation rates, both of which could aid persistence at the infection site. Surviving at the infection site provides the low-level-resistant population an opportunity to evolve by acquiring secondary mutations in antibiotic target genes, resulting in clinical resistance to the treating antibiotic. Thus, this emphasizes the importance and challenge for clinicians to be able to monitor overexpression of efflux pumps before low-level resistance develops to clinical resistance. One possible treatment option could be an efflux pump-targeted approach using efflux pump inhibitors.

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High Cell Selectivity and Low-Level Antibacterial Resistance of Designed Amphiphilic Peptide G(IIKK)3I-NH2

ACS Applied Materials & Interfaces ◽

10.1021/am504973d ◽

2014 ◽

Vol 6 (19) ◽

pp. 16529-16536 ◽

Cited By ~ 35

Author(s):

Cuixia Chen ◽

Jing Hu ◽

Ping Zeng ◽

Yucan Chen ◽

Hai Xu ◽

...

Keyword(s):

Antibacterial Resistance ◽

High Cell ◽

Low Level ◽

Cell Selectivity ◽

Amphiphilic Peptide ◽

Peptide G

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Detection of Low-Level Fosfomycin-Resistant Variants by Decreasing Glucose-6-Phosphate Concentration in Fosfomycin Susceptibility Determination

Antibiotics ◽

10.3390/antibiotics9110802 ◽

2020 ◽

Vol 9 (11) ◽

pp. 802

Author(s):

Guillermo Martín-Gutiérrez ◽

Fernando Docobo-Pérez ◽

Jose Manuel Rodríguez-Martínez ◽

Alvaro Pascual ◽

Jesús Blázquez ◽

...

Keyword(s):

Urinary Tract ◽

Coli Strain ◽

Bacterial Cells ◽

Resistance Development ◽

Minimal Inhibitory Concentrations ◽

E Coli ◽

Low Level ◽

Clinical Resistance ◽

Susceptibility Tests ◽

Chromosomal Mutations

Mutations that confer low-level fosfomycin resistance (LLFR) but not clinical resistance in Escherichia coli are increasingly reported. LLFR strains can become clinically resistant under urinary tract physiological conditions or may act as gateways for highly resistant subpopulations by the selection of additional LLFR mutations. Nevertheless, most LLFR strains are impossible to detect under routine fosfomycin susceptibility determinations. Here, we have explored the possibility of detecting LLFR variants by reducing glucose-6-phosphate (G6P) concentration in fosfomycin susceptibility testing for E. coli strains. As a proof of concept, fosfomycin minimal inhibitory concentrations (MICs) and disk diffusion susceptibility tests were performed for E. coli strain BW25113 and 10 isogenic derivatives carrying the most prevalent LLFR chromosomal mutations (∆uhpT, ∆glpT, ∆cyaA, and ∆ptsI) and their double combinations. Whereas standard G6P concentrations detected only ∆uhpT single and double variants, assays with reduced G6P detected all LLFR variants. In addition, G6P levels were determined to be ≤5 µg/mL in urine samples from 30 patients with urinary tract infection (UTI) caused by E. coli and 10 healthy volunteers, suggesting that most bacterial cells in uncomplicated UTIs are facing fosfomycin under low G6P concentration. Reducing G6P allows for the detection of LLFR variants, which may suppose a risk for future resistance development, especially in UTIs.

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Role of Disputed Mutations in the rpoB Gene in Interpretation of Automated Liquid MGIT Culture Results for Rifampin Susceptibility Testing of Mycobacterium tuberculosis

Journal of Clinical Microbiology ◽

10.1128/jcm.01599-17 ◽

2018 ◽

Vol 56 (5) ◽

Cited By ~ 19

Author(s):

Paolo Miotto ◽

Andrea M. Cabibbe ◽

Emanuele Borroni ◽

Massimo Degano ◽

Daniela M. Cirillo

Keyword(s):

Mycobacterium Tuberculosis ◽

In Silico ◽

Susceptibility Testing ◽

Rpob Gene ◽

Drug Susceptibility ◽

Drug Susceptibility Testing ◽

Missense Mutations ◽

Content Type ◽

Low Level ◽

Clinical Resistance

ABSTRACT Low-level rifampin resistance associated with specific rpoB mutations (referred as “disputed”) in Mycobacterium tuberculosis is easily missed by some phenotypic methods. To understand the mechanism by which some mutations are systematically missed by MGIT phenotypic testing, we performed an in silico analysis of their effect on the structural interaction between the RpoB protein and rifampin. We also characterized 24 representative clinical isolates by determining MICs on 7H10 agar and testing them by an extended MGIT protocol. We analyzed 2,097 line probe assays, and 156 (7.4%) cases showed a hybridization pattern referred to here as “no wild type + no mutation.” Isolates harboring “disputed” mutations (L430P, D435Y, H445C/L/N/S, and L452P) tested susceptible in MGIT, with prevalence ranging from 15 to 57% (overall, 16 out of 55 isolates [29%]). Our in silico analysis did not highlight any difference between “disputed” and “undisputed” substitutions, indicating that all rpoB missense mutations affect the rifampin binding site. MIC testing showed that “undisputed” mutations are associated with higher MIC values (≥20 mg/liter) compared to “disputed” mutations (4 to >20 mg/liter). Whereas “undisputed” mutations didn't show any delay (Δ) in time to positivity of the test tube compared to the control tube on extended MGIT protocol, “disputed” mutations showed a mean Δ of 7.2 days (95% confidence interval [CI], 4.2 to 10.2 days; P < 0.05), providing evidence that mutations conferring low-level resistance are associated with a delay in growth on MGIT. Considering the proved relevance of L430P, D435Y, H445C/L/N, and L452P mutations in determining clinical resistance, genotypic drug susceptibility testing (DST) should be used to replace phenotypic results (MGIT) when such mutations are found.

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Sensitive Detection of BCR-ABL1 Mutations in Patients With Chronic Myeloid Leukemia After Imatinib Resistance Is Predictive of Outcome During Subsequent Therapy

Journal of Clinical Oncology ◽

10.1200/jco.2011.35.0934 ◽

2011 ◽

Vol 29 (32) ◽

pp. 4250-4259 ◽

Cited By ~ 60

Author(s):

Wendy T. Parker ◽

Rebecca M. Lawrence ◽

Musei Ho ◽

Darryl L. Irwin ◽

Hamish S. Scott ◽

...

Keyword(s):

Mass Spectrometry ◽

Detection Limit ◽

Chronic Myeloid Leukemia ◽

Myeloid Leukemia ◽

Chronic Phase ◽

Imatinib Treatment ◽

Imatinib Resistance ◽

Low Level ◽

Clinical Resistance ◽

The Impact

Purpose BCR-ABL1 mutation analysis is recommended to facilitate selection of appropriate therapy for patients with chronic myeloid leukemia after treatment with imatinib has failed, since some frequently occurring mutations confer clinical resistance to nilotinib and/or dasatinib. However, mutations could be present below the detection limit of conventional direct sequencing. We developed a sensitive, multiplexed mass spectrometry assay (detection limit, 0.05% to 0.5%) to determine the impact of low-level mutations after imatinib treatment has failed. Patients and Methods Mutation status was assessed in 220 patients treated with nilotinib or dasatinib after they experienced resistance to imatinib. Results Mutations were detected by sequencing in 128 patients before commencing nilotinib or dasatinib therapy (switchover). In 64 patients, 132 additional low-level mutations were detected by mass spectrometry alone (50 of 132 mutations were resistant to nilotinib and/or dasatinib). When patients received the inhibitor for which the mutation confers resistance, 84% of the low-level resistant mutations rapidly became dominant clones detectable by sequencing, including 11 of 12 T315I mutations. Subsequent complete cytogenetic response rates were lower for patients with resistant mutations at switchover detected by sequencing (0%) or mass spectrometry alone (16%) compared with patients with other mutations or no mutations (41% and 49%, respectively; P < .001). Failure-free survival among the 100 patients with chronic phase chronic myeloid leukemia when resistant mutations were detected at switchover by sequencing or mass spectrometry alone was 0% and 0% compared with 51% and 45% for patients with other mutations or no mutations (P = .003). Conclusion Detection of low-level mutations after imatinib resistance offers critical information to guide subsequent therapy selection. If an inappropriate kinase inhibitor is selected, there is a high risk of treatment failure with clonal expansion of the resistant mutant.

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Tryptophan-Niacin Metabolism in Rat with Puromycin Aminonucleoside-Induced Nephrosis

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831.76.1.28 ◽

2006 ◽

Vol 76 (1) ◽

pp. 28-33 ◽

Cited By ~ 7

Author(s):

Yukari Egashira ◽

Shin Nagaki ◽

Hiroo Sanada

Keyword(s):

Body Weight ◽

Urinary Excretion ◽

Enzyme Activities ◽

Treated Group ◽

Control Group ◽

Puromycin Aminonucleoside ◽

Low Level ◽

Key Enzyme

We investigated the change of tryptophan-niacin metabolism in rats with puromycin aminonucleoside PAN-induced nephrosis, the mechanisms responsible for their change of urinary excretion of nicotinamide and its metabolites, and the role of the kidney in tryptophan-niacin conversion. PAN-treated rats were intraperitoneally injected once with a 1.0% (w/v) solution of PAN at a dose of 100 mg/kg body weight. The collection of 24-hour urine was conducted 8 days after PAN injection. Daily urinary excretion of nicotinamide and its metabolites, liver and blood NAD, and key enzyme activities of tryptophan-niacin metabolism were determined. In PAN-treated rats, the sum of urinary excretion of nicotinamide and its metabolites was significantly lower compared with controls. The kidneyα-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) activity in the PAN-treated group was significantly decreased by 50%, compared with the control group. Although kidney ACMSD activity was reduced, the conversion of tryptophan to niacin tended to be lower in the PAN-treated rats. A decrease in urinary excretion of niacin and the conversion of tryptophan to niacin in nephrotic rats may contribute to a low level of blood tryptophan. The role of kidney ACMSD activity may be minimal concerning tryptophan-niacin conversion under this experimental condition.

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