Highly Reproducible Bactericidal Activity Test Results by Using a Modified National Committee for Clinical Laboratory Standards Broth Macrodilution Technique

Hacek, Donna M.; Dressel, Dana C.; Peterson, Lance R.

doi:10.1128/jcm.37.6.1881-1884.1999

Cited by 40 publications

(19 citation statements)

References 21 publications

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“…Killing by microbicidal antibiotics is typically biphasic for a wide range of species and compounds. The presence of a residual fraction of cells that die slowly or not at all has been largely ignored, in part due to the definition of MBC‐death of ≥3 log of cells [9,13]. In most cases studied, persisters will fall beyond this threshold and are not reported.…”

Section: Discussionmentioning

confidence: 99%

Persister cells and tolerance to antimicrobials

Keren

Kaldalu

Spoering

et al. 2004

FEMS Microbiology Letters

955

948

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Bacterial populations produce persister cells that neither grow nor die in the presence of microbicidal antibiotics. Persisters are largely responsible for high levels of biofilm tolerance to antimicrobials, but virtually nothing was known about their biology. Tolerance of Escherichia coli to ampicillin and ofloxacin was tested at different growth stages to gain insight into the nature of persisters. The number of persisters did not change in lag or early exponential phase, and increased dramatically in mid-exponential phase. Similar dynamics were observed with Pseudomonas aeruginosa (ofloxacin) and Staphylococcus aureus (ciprofloxacin and penicillin). This shows that production of persisters depends on growth stage. Maintaining a culture of E. coli at early exponential phase by reinoculation eliminated persisters. This suggests that persisters are not at a particular stage in the cell cycle, neither are they defective cells nor cells created in response to antibiotics. Our data indicate that persisters are specialized survivor cells. ß

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Section: Discussionmentioning

confidence: 99%

Persister cells and tolerance to antimicrobials

Keren

Kaldalu

Spoering

et al. 2004

FEMS Microbiology Letters

955

948

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“…(ii) Broth microdilution method. MIC values of selected antibiotics was determined by macrodilutions in LB as previously described (56), with minor modifications. Briefly, overnight cultures were diluted to an OD 600 of 0.1 and added to 96-well plates at a final dilution of 1:200 (vol/vol).…”

Section: Discussionmentioning

confidence: 99%

The Mla Pathway Plays an Essential Role in the Intrinsic Resistance of Burkholderia cepacia Complex Species to Antimicrobials and Host Innate Components

2018

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Antibiotic resistance is a threat to our modern society, and new strategies leading to the identification of new molecules or targets to combat multidrug-resistant pathogens are needed. Species of the genus , including the complex (Bcc), , and, can be highly pathogenic and are intrinsically resistant to multiple classes of antibiotics. Bcc species are nonetheless sensitive to extracellular products released by in interspecies competition. We screened for transposon mutants with increased sensitivity to spent medium and identified multiple mutants in genes sharing homology with the Mla pathway. Insertional mutants in representative genes of the Bcc Mla pathway had a compromised cell membrane and were more sensitive to various extracellular stresses, including antibiotics and human serum. More precisely, mutants in the Bcc species and were more susceptible to Gram-positive antibiotics (i.e., macrolides and rifampin), fluoroquinolones, tetracyclines, and chloramphenicol. Genetic complementation of insertional mutants restored cell permeability and resistance to Gram-positive antibiotics. Importantly, Bcc mutants were not universally weaker strains since their susceptibilities to other classes of antibiotics were unaffected. Although cell permeability of homologous mutants in or was also impaired, they were not more sensitive to Gram-positive antibiotics or other antimicrobials as was observed in Bcc mutants. Together, the data suggest that the Mla pathway in may play a different biological role, which could potentially represent a-specific drug target in combination therapy with antibiotic adjuvants. The outer membrane of Gram-negative bacteria acts as an effective barrier against toxic compounds, and therefore compromising this structure could increase sensitivity to currently available antibiotics. In this study, we show that the Mla pathway, a system involved in maintaining the integrity of the outer membrane, is genetically and functionally different in complex species compared to that in other proteobacteria. Mutants in genes of or were sensitive to Gram-positive antibiotics, while this effect was not observed in or The Mla pathway in species may represent an ideal genus-specific target to address their intrinsic antimicrobial resistances.

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“…MIC values of small molecules and spent media were determined by macrodilutions in LB as previously described (Hacek et al, 1999 ) with minor modifications. FICI values were determined as previously described (Odds, 2003 ; Pillai et al, 2005 ).…”

Section: Methodsmentioning

confidence: 99%

Cyanide Toxicity to Burkholderia cenocepacia Is Modulated by Polymicrobial Communities and Environmental Factors

Bernier

Workentine

et al. 2016

Front. Microbiol.

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Microbes within polymicrobial communities can establish positive and negative interactions that have the potential to influence the overall behavior of the community. Pseudomonas aeruginosa and species of the Burkholderia cepacia complex (Bcc) can co-exist in the lower airways, however several studies have shown that P. aeruginosa can effectively kill the Bcc in vitro, for which hydrogen cyanide (HCN) was recently proposed to play a critical role. Here we show that modification of the environment (i.e., culture medium), long-term genetic adaptation of P. aeruginosa to the cystic fibrosis (CF) lung, or the addition of another bacterial species to the community can alter the sensitivity of Burkholderia cenocepacia to P. aeruginosa toxins. We specifically demonstrate that undefined rich media leads to higher susceptibility of B. cenocepacia to P. aeruginosa toxins like cyanide as compared to a synthetic medium (SCFM), that mimics the CF lung nutritional content. Overall, our study shows that the polymicrobial environment can have profound effects on negative interactions mediated by P. aeruginosa against B. cenocepacia. In fact, evolved P. aeruginosa or the presence of other species such as Staphylococcus aureus can directly abolish the direct competition mediated by cyanide and consequently maintaining a higher level of species diversity within the community.

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Highly Reproducible Bactericidal Activity Test Results by Using a Modified National Committee for Clinical Laboratory Standards Broth Macrodilution Technique

Cited by 40 publications

References 21 publications

Persister cells and tolerance to antimicrobials

Persister cells and tolerance to antimicrobials

The Mla Pathway Plays an Essential Role in the Intrinsic Resistance of Burkholderia cepacia Complex Species to Antimicrobials and Host Innate Components

Cyanide Toxicity to Burkholderia cenocepacia Is Modulated by Polymicrobial Communities and Environmental Factors

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