Eliciting antibiotics active against the ESKAPE pathogens in a collection of actinomycetes isolated from mountain soils

The rapid emergence of multidrug-resistant (MDR) bacterial pathogens poses a major threat for human health. In recent years, genome sequencing has unveiled many poorly expressed antibiotic clusters in actinomycetes. Here, we report a well-defined ecological collection of >800 actinomycetes obtained from sites in the Himalaya and Qinling mountains, and we used these in a concept study to see how efficiently antibiotics can be elicited against MDR pathogens isolated recently from the clinic. Using 40 different growth conditions, 96 actinomycetes were identified – predominantly Streptomyces – that produced antibiotics with efficacy against the MDR clinical isolates referred to as ESKAPE pathogens: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and/or Enterobacter cloacae. Antimicrobial activities that fluctuated strongly with growth conditions were correlated with specific compounds, including borrelidin, resistomycin, carbomethoxy-phenazine, and 6,7,8- and 5,6,8-trimethoxy-3-methylisocoumarin, of which the latter was not described previously. Our work provided insights into the potential of actinomycetes as producers of drugs with efficacy against clinical isolates that have emerged recently and also underlined the importance of targeting a specific pathogen.

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Forging new antibiotic combinations under iron-limiting conditions

10.1101/775445 ◽

2019 ◽

Author(s):

Derek C. K. Chan ◽

Irene Guo ◽

Lori L. Burrows

Keyword(s):

Antibacterial Agents ◽

Iron Chelator ◽

Multidrug Resistant ◽

Antimicrobial Activities ◽

Clinical Isolates ◽

Gallium Nitrate ◽

Triple Combination ◽

Nosocomial Pathogen ◽

Iron Sequestration ◽

Spectrophotometric Data

ABSTRACTPseudomonas aeruginosa is a multidrug-resistant nosocomial pathogen. We showed previously that thiostrepton (TS), a gram-positive thiopeptide antibiotic, was imported via pyoverdine receptors and synergized with iron chelator deferasirox (DSX) to inhibit the growth of P. aeruginosa and Acinetobacter baumannii clinical isolates. A small number of P. aeruginosa and A. baumannii isolates were resistant to the combination, prompting us to search for other compounds that could synergize with TS against those strains. From literature surveys we selected 14 compounds reported to have iron-chelating activity, plus one iron analogue, and tested them for synergy with TS. Doxycycline (DOXY), ciclopirox olamine (CO), tropolone (TRO), clioquinol (CLI), and gallium nitrate (GN) synergized with TS. Individual compounds were bacteriostatic but the combinations were bactericidal. Our spectrophotometric data and chrome azurol S agar assay confirmed that the chelators potentate TS activity through iron sequestration rather than through their innate antimicrobial activities. A triple combination of TS + DSX + DOXY had the most potent activity against P. aeruginosa and A. baumannii isolates. One P. aeruginosa clinical isolate was resistant to the triple combination, but susceptible to a triple combination containing higher concentrations of CLI, CO, or DOXY. All A. baumannii isolates were susceptible to the triple combinations. Our data reveal a diverse set of compounds with dual activity as antibacterial agents and TS adjuvants, allowing combinations to be tailored for resistant clinical isolates.

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Engineered Cationic Antimicrobial Peptides To Overcome Multidrug Resistance by ESKAPE Pathogens

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.03937-14 ◽

2014 ◽

Vol 59 (2) ◽

pp. 1329-1333 ◽

Cited By ~ 63

Author(s):

Berthony Deslouches ◽

Jonathan D. Steckbeck ◽

Jodi K. Craigo ◽

Yohei Doi ◽

Jane L. Burns ◽

...

Keyword(s):

Multidrug Resistance ◽

Antimicrobial Peptides ◽

De Novo ◽

Multidrug Resistant ◽

Clinical Isolates ◽

Resistant Bacteria ◽

Clinical Settings ◽

Eskape Pathogens ◽

Antibiotic Peptides

ABSTRACTMultidrug resistance constitutes a threat to the medical achievements of the last 50 years. In this study, we demonstrated the abilities of twode novoengineered cationic antibiotic peptides (eCAPs), WLBU2 and WR12, to overcome resistance from 142 clinical isolates representing the most common multidrug-resistant (MDR) pathogens and to display a lower propensity to select for resistant bacteriain vitrocompared to that with colistin and LL37. The results warrant an exploration of eCAPs for use in clinical settings.

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Validation of a Novel Murine Wound Model of Acinetobacter baumannii Infection

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01944-13 ◽

2013 ◽

Vol 58 (3) ◽

pp. 1332-1342 ◽

Cited By ~ 36

Author(s):

Mitchell G. Thompson ◽

Chad C. Black ◽

Rebecca L. Pavlicek ◽

Cary L. Honnold ◽

Matthew C. Wise ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Surgical Site Infections ◽

Multidrug Resistant ◽

Content Type ◽

Wound Model ◽

Community Profiling ◽

Specific Pathogen ◽

Uninoculated Control ◽

Eskape Pathogens

ABSTRACTPatients recovering from traumatic injuries or surgery often require weeks to months of hospitalization, increasing the risk for wound and surgical site infections caused by ESKAPE pathogens, which includeA. baumannii(the ESKAPE pathogens areEnterococcus faecium,Staphylococcus aureus,Klebsiella pneumoniae,Acinetobacter baumannii,Pseudomonas aeruginosa, andEnterobacterspecies). As new therapies are being developed to counterA. baumanniiinfections, animal models are also needed to evaluate potential treatments. Here, we present an excisional, murine wound model in which a diminutive inoculum of a clinically relevant, multidrug-resistantA. baumanniiisolate can proliferate, form biofilms, and be effectively treated with antibiotics. The model requires a temporary, cyclophosphamide-induced neutropenia to establish an infection that can persist. A 6-mm-diameter, full-thickness wound was created in the skin overlying the thoracic spine, and after the wound bed was inoculated, it was covered with a dressing for 7 days. Uninoculated control wounds healed within 13 days, whereas infected, placebo-treated wounds remained unclosed beyond 21 days. Treated and untreated wounds were assessed with multiple quantitative and qualitative techniques that included gross pathology, weight loss and recovery, wound closure, bacterial burden, 16S rRNA community profiling, histopathology, peptide nucleic acid-fluorescencein situhybridization, and scanning electron microscopy assessment of biofilms. The range of differences that we are able to identify with these measures in antibiotic- versus placebo-treated animals provides a clear window within which novel antimicrobial therapies can be assessed. The model can be used to evaluate antimicrobials for their ability to reduce specific pathogen loads in wounded tissues and clear biofilms. Ultimately, the mouse model approach allows for highly powered studies and serves as an initial multifacetedin vivoassessment prior to testing in larger animals.

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Novel and potent antimicrobial effects of caspofungin on drug-resistant Candida and bacteria

Scientific Reports ◽

10.1038/s41598-020-74749-8 ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Makoto Sumiyoshi ◽

Taiga Miyazaki ◽

Juliann Nzembi Makau ◽

Satoshi Mizuta ◽

Yoshimasa Tanaka ◽

...

Keyword(s):

Conformational Changes ◽

Drug Exposure ◽

Growth Conditions ◽

Multidrug Resistant ◽

Antimicrobial Activities ◽

Ion Concentration ◽

Candida Auris ◽

Fungal Cell ◽

Ionic Solutions ◽

Glucose Water

Abstract Echinocandins, including caspofungin, micafungin, and anidulafungin, are first-line antifungal agents for the treatment of invasive candidiasis. They exhibit fungicidal activity by inhibiting the synthesis of β-1,3-d-glucan, an essential component of the fungal cell wall. However, they are active only against proliferating fungal cells and unable to completely eradicate fungal cells even after a 24 h drug exposure in standard time-kill assays. Surprisingly, we found that caspofungin, when dissolved in low ionic solutions, had rapid and potent antimicrobial activities against multidrug-resistant (MDR) Candida and bacteria cells even in non-growth conditions. This effect was not observed in 0.9% NaCl or other ion-containing solutions and was not exerted by other echinocandins. Furthermore, caspofungin dissolved in low ionic solutions drastically reduced mature biofilm cells of MDR Candida auris in only 5 min, as well as Candida-bacterial polymicrobial biofilms in a catheter-lock therapy model. Caspofungin displayed ion concentration-dependent conformational changes and intracellular accumulation with increased reactive oxygen species production, indicating a novel mechanism of action in low ionic conditions. Importantly, caspofungin dissolved in 5% glucose water did not exhibit increased toxicity to human cells. This study facilitates the development of new therapeutic strategies in the management of catheter-related biofilm infections.

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Thiostrepton hijacks pyoverdine receptors to inhibit growth ofPseudomonas aeruginosa

10.1101/567990 ◽

2019 ◽

Cited By ~ 1

Author(s):

Michael R. Ranieri ◽

Derek C. K. Chan ◽

Luke Yaeger ◽

Madeleine Rudolph ◽

Sawyer Karabelas-Pittman ◽

...

Keyword(s):

Biofilm Formation ◽

Opportunistic Pathogen ◽

Growth Conditions ◽

Multidrug Resistant ◽

Clinical Isolates ◽

23S Rrna ◽

Dependent Manner ◽

Peptide Antibiotics ◽

Iron Starvation ◽

Gram Negative

ABSTRACTPseudomonas aeruginosais a biofilm-forming opportunistic pathogen and intrinsically resistant to many antibiotics. In a high-throughput screen for molecules that modulate biofilm formation, we discovered that the thiopeptide antibiotic, thiostrepton (TS) - considered inactive against Gram-negative bacteria - stimulatedP. aeruginosabiofilm formation in a dose-dependent manner. This phenotype is characteristic of exposure to antimicrobial compounds at sub-inhibitory concentrations, suggesting that TS was active againstP. aeruginosa. Supporting this observation, TS inhibited growth of a panel of 96 multidrug-resistant (MDR)P. aeruginosaclinical isolates at low micromolar concentrations. TS also had activity againstAcinetobacter baumanniiclinical isolates. Expression of Tsr - a 23S rRNA-modifying methyltransferase - in trans conferred TS resistance, confirming that the drug acted via its canonical mode of action, inhibition of ribosome function. Deletion of oligopeptide permease systems used by other peptide antibiotics for uptake failed confer TS resistance. TS susceptibility was inversely proportional to iron availability, suggesting that TS exploits uptake pathways whose expression is increased under iron starvation. Consistent with this finding, TS activity againstP. aeruginosaandA. baumanniiwas potentiated by FDA-approved iron chelators deferiprone and deferasirox. Screening ofP. aeruginosamutants for TS resistance revealed that it exploits pyoverdine receptors FpvA and FpvB to cross the outer membrane. Our data show that the biofilm stimulation phenotype can reveal cryptic sub-inhibitory antibiotic activity, and that TS has activity against select multidrug resistant Gram-negative pathogens under iron-limited growth conditions, similar to those encountered at sites of infection.

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Antimicrobial Activities of Ceragenins against Clinical Isolates of Resistant Staphylococcus aureus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01325-06 ◽

2007 ◽

Vol 51 (4) ◽

pp. 1268-1273 ◽

Cited By ~ 62

Author(s):

Judy N. Chin ◽

Michael J. Rybak ◽

Chrissy M. Cheung ◽

Paul B. Savage

Keyword(s):

Staphylococcus Aureus ◽

Multidrug Resistant ◽

Antimicrobial Activities ◽

Curve Analysis ◽

Clinical Isolates ◽

Resistant Bacteria ◽

Inoculum Effect ◽

Kill Curve ◽

Time Required ◽

Time Kill

ABSTRACT The rise in the rates of glycopeptide resistance among Staphylococcus aureus isolates is concerning and underscores the need for the development of novel potent compounds. Ceragenins CSA-8 and CSA-13, cationic steroid molecules that mimic endogenous antimicrobial peptides, have previously been demonstrated to possess broad-spectrum activities against multidrug-resistant bacteria. We examined the activities of CSA-8 and CSA-13 against clinical isolates of vancomycin-intermediate S. aureus (VISA), heterogeneous vancomycin-intermediate S. aureus (hVISA), as well as vancomycin-resistant S. aureus (VRSA) and compared them to those of daptomycin, linezolid, and vancomycin by susceptibility testing and killing curve analysis. We also examined CSA-13 for its concentration-dependent activity, inoculum effect, postantibiotic effect (PAE), and synergy in combination with various antimicrobials. Overall, the MICs and minimal bactericidal concentrations of CSA-13 were fourfold lower than those of CSA-8. Time-kill curve analysis of the VRSA, VISA, and hVISA clinical isolates demonstrated concentration-dependent bactericidal killing. An inoculum effect was also observed when a higher starting bacterial density was used, with the time required to achieve 99.9% killing reaching 1 h with a 6-log10-CFU/ml starting inoculum, whereas it was ≥24 h with a 8- to 9-log10-CFU/ml starting inoculum with 10× the MIC (P ≤ 0.001). A concentration-dependent PAE was demonstrated with CSA-13, nearly doubling from 2× to 4× the MIC (P = 0.03). With respect to the CSA-13 antimicrobial combinations, time-kill curve analysis showed no difference in the log10 CFU/ml at 24 h for the majority of the organisms tested. However, early synergy at 4 to 8 h was detected against the VRSA Pennsylvania strain (2002) when CSA-13 was tested in combination with gentamicin, while early additivity was demonstrated against all of the other organisms.

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Forging New Antibiotic Combinations under Iron-Limiting Conditions

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01909-19 ◽

2020 ◽

Vol 64 (3) ◽

Cited By ~ 2

Author(s):

Derek C. K. Chan ◽

Irene Guo ◽

Lori L. Burrows

Keyword(s):

Antibacterial Agents ◽

Iron Chelator ◽

Multidrug Resistant ◽

Antimicrobial Activities ◽

Clinical Isolates ◽

Gallium Nitrate ◽

Triple Combination ◽

Content Type ◽

Iron Sequestration ◽

Spectrophotometric Data

ABSTRACT Pseudomonas aeruginosa is a multidrug-resistant nosocomial pathogen. We showed previously that thiostrepton (TS), a Gram-positive thiopeptide antibiotic, is imported via pyoverdine receptors and synergizes with iron chelator deferasirox (DSX) to inhibit the growth of P. aeruginosa and Acinetobacter baumannii clinical isolates. A small number of P. aeruginosa and A. baumannii isolates were resistant to the combination, prompting us to search for other compounds that could synergize with TS against those strains. From literature surveys, we selected 14 compounds reported to have iron-chelating activity, plus one iron analogue, and tested them for synergy with TS. Doxycycline (DOXY), ciclopirox olamine (CO), tropolone (TRO), clioquinol (CLI), and gallium nitrate (GN) synergized with TS. Individual compounds were bacteriostatic, but the combinations were bactericidal. Our spectrophotometric data and chrome azurol S agar assay confirmed that the chelators potentiate TS activity through iron sequestration rather than through their innate antimicrobial activities. A triple combination of TS plus DSX plus DOXY had the most potent activity against P. aeruginosa and A. baumannii isolates. One P. aeruginosa clinical isolate was resistant to the triple combination but susceptible to a triple combination containing higher concentrations of CLI, CO, or DOXY. All A. baumannii isolates were susceptible to the triple combinations. Our data reveal a diverse set of compounds with dual activity as antibacterial agents and TS adjuvants, allowing combinations to be tailored for resistant clinical isolates.

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Ocimum gratissimum Capped Sulfur Nanoparticles and Antibacterial Efficacy against Multidrug-Resistant Microbes

Asian Journal of Research in Biochemistry ◽

10.9734/ajrb/2020/v7i430151 ◽

2020 ◽

pp. 85-95

Author(s):

Owolabi M. Bankole ◽

Oludare Temitope Osuntokun ◽

Adedapo Adeola ◽

Afolabi Owoeye

Keyword(s):

Staphylococcus Aureus ◽

Oxalic Acid ◽

Plant Extract ◽

Research Work ◽

Multidrug Resistant ◽

Antimicrobial Activities ◽

Clinical Isolates ◽

Ocimum Gratissimum ◽

Salmonella Pullorum ◽

Sulfur Nanoparticles

This manuscript reports for the first time synthesis of sulfur nanoparticles prepared from thiosulphatepentahydrate ( ) using either oxalic acid alone ( ), or mixture of oxalic acid and aqueous solution of Ocimum gratissimum ( ). The synthesized sulfur nanoparticles were obtained in satisfactory yields, and characterized with techniques such asUV-Vis, XRD, SEM, EDX, TEM, and FT-IR. Presence of capping agents: Oxalic acid and biomolecule contents of Ocimum gratissimum were confirmed by FTIR. Crystallinity, morphology, shapes and elemental compositions of as-prepared nanoparticles were confirmed by XRD, SEM, TEM and EDX, respectively. Antimicrobial activities of the prepared sulfur nanoparticles against five (5) multidrug-resistant microbes were used for this research work. This included Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Salmonella pullorum. The zone of inhibition of the sulfur nanoparticles tested against selected clinical isolates. Staphylococcus aureus was observed to have the highest susceptibility to sulfur nanoparticles ( ) mediated with Ocimum gratissimum plant extract with diameter of 21.0mm; E.coli and Salmonella P. aeruginosa showed resistance. All tested clinical isolates were resistant to the other sulfur nanoparticles (SNP1) synthesized in the absence of Ocimum gratissimum plant extract.

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