scholarly journals Evaluation of Reduced Susceptibility to Quaternary Ammonium Compounds and Bisbiguanides in Clinical Isolates and Laboratory-Generated Mutants of Staphylococcus aureus

2013 ◽  
Vol 57 (8) ◽  
pp. 3488-3497 ◽  
Author(s):  
Leonardo Furi ◽  
Maria Laura Ciusa ◽  
Daniel Knight ◽  
Valeria Di Lorenzo ◽  
Nadia Tocci ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Promoter Region ◽  
Benzalkonium Chloride ◽  
Galleria Mellonella ◽  
Efflux Pump ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Content Type ◽  
Ammonium Compounds

ABSTRACTThe MICs and minimum bactericidal concentrations (MBCs) for the biocides benzalkonium chloride and chlorhexidine were determined against 1,602 clinical isolates ofStaphylococcus aureus. Both compounds showed unimodal MIC and MBC distributions (2 and 4 or 8 mg/liter, respectively) with no apparent subpopulation with reduced susceptibility. To investigate further, all isolates were screened forqacgenes, and 39 of these also had the promoter region of the NorA multidrug-resistant (MDR) efflux pump sequenced. The presence ofqacA,qacB,qacC, andqacGgenes increased the mode MIC, but not MBC, to benzalkonium chloride, while onlyqacAandqacBincreased the chlorhexidine mode MIC. Isolates with a wild-typenorApromoter or mutations in thenorApromoter had similar biocide MIC distributions; notably, not all clinical isolates withnorAmutations were resistant to fluoroquinolones.In vitroefflux mutants could be readily selected with ethidium bromide and acriflavine. Multiple passages were necessary to select mutants with biocides, but these mutants showed phenotypes comparable to those of mutants selected by dyes. All mutants showed changes in the promoter region ofnorA, but these were distinct from this region of the clinical isolates. Still, none of thein vitromutants displayed fitness defects in a killing assay inGalleria mellonellalarvae. In conclusion, our data provide an in-depth comparative overview on efflux inS. aureusmutants and clinical isolates, showing also that plasmid-encoded efflux pumps did not affect bactericidal activity of biocides. In addition, currentin vitrotests appear not to be suitable for predicting levels of resistance that are clinically relevant.

scholarly journals Tigecycline Nonsusceptibility Occurs Exclusively in Fluoroquinolone-Resistant Escherichia coli Clinical Isolates, Including the Major Multidrug-Resistant Lineages O25b:H4-ST131-H30R and O1-ST648

2016 ◽  
Vol 61 (2) ◽  
Author(s):  
Toyotaka Sato ◽  
Yuuki Suzuki ◽  
Tsukasa Shiraishi ◽  
Hiroyuki Honda ◽  
Masaaki Shinagawa ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Parental Strain ◽  
Efflux Pump ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Content Type ◽  
E Coli ◽  
Line Drug

ABSTRACT Tigecycline (TGC) is a last-line drug for multidrug-resistant Enterobacteriaceae. We investigated the mechanism(s) underlying TGC nonsusceptibility (TGC resistant/intermediate) in Escherichia coli clinical isolates. The MIC of TGC was determined for 277 fluoroquinolone-susceptible isolates (ciprofloxacin [CIP] MIC, <0.125 mg/liter) and 194 fluoroquinolone-resistant isolates (CIP MIC, >2 mg/liter). The MIC50 and MIC90 for TGC in fluoroquinolone-resistant isolates were 2-fold higher than those in fluoroquinolone-susceptible isolates (MIC50, 0.5 mg/liter versus 0.25 mg/liter; MIC90, 1 mg/liter versus 0.5 mg/liter, respectively). Two fluoroquinolone-resistant isolates (O25b:H4-ST131-H30R and O125:H37-ST48) were TGC resistant (MICs of 4 and 16 mg/liter, respectively), and four other isolates of O25b:H4-ST131-H30R and an isolate of O1-ST648 showed an intermediate interpretation (MIC, 2 mg/liter). No TGC-resistant/intermediate strains were found among the fluoroquinolone-susceptible isolates. The TGC-resistant/intermediate isolates expressed higher levels of acrA and acrB and had lower intracellular TGC concentrations than susceptible isolates, and they possessed mutations in acrR and/or marR. The MICs of acrAB-deficient mutants were markedly lower (0.25 mg/liter) than those of the parental strain. After continuous stepwise exposure to CIP in vitro, six of eight TGC-susceptible isolates had reduced TGC susceptibility. Two of them acquired TGC resistance (TGC MIC, 4 mg/liter) and exhibited expression of acrA and acrB and mutations in acrR and/or marR. In conclusion, a population of fluoroquinolone-resistant E. coli isolates, including major extraintestinal pathogenic lineages O25b:H4-ST131-H30R and O1-ST648, showed reduced susceptibility to TGC due to overexpression of the efflux pump AcrAB-TolC, leading to decreased intracellular concentrations of the antibiotics that may be associated with the development of fluoroquinolone resistance.

scholarly journals Carbapenem-Resistant Klebsiella pneumoniae Clinical Isolates: In Vivo Virulence Assessment in Galleria mellonella and Potential Therapeutics by Polycationic Oligoethyleneimine

Antibiotics ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 56
Author(s):  
Dalila Mil-Homens ◽  
Maria Martins ◽  
José Barbosa ◽  
Gabriel Serafim ◽  
Maria J. Sarmento ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Galleria Mellonella ◽  
Multidrug Resistant ◽  
In Vitro Models ◽  
Clinical Isolates ◽  
In Vivo Model ◽  
Virulence Potential ◽  
Hospital Acquired

Klebsiella pneumoniae, one of the most common pathogens found in hospital-acquired infections, is often resistant to multiple antibiotics. In fact, multidrug-resistant (MDR) K. pneumoniae producing KPC or OXA-48-like carbapenemases are recognized as a serious global health threat. In this sense, we evaluated the virulence of K. pneumoniae KPC(+) or OXA-48(+) aiming at potential antimicrobial therapeutics. K. pneumoniae carbapenemase (KPC) and the expanded-spectrum oxacillinase OXA-48 isolates were obtained from patients treated in medical care units in Lisbon, Portugal. The virulence potential of the K. pneumonia clinical isolates was tested using the Galleria mellonella model. For that, G. mellonella larvae were inoculated using patients KPC(+) and OXA-48(+) isolates. Using this in vivo model, the KPC(+) K. pneumoniae isolates showed to be, on average, more virulent than OXA-48(+). Virulence was found attenuated when a low bacterial inoculum (one magnitude lower) was tested. In addition, we also report the use of a synthetic polycationic oligomer (L-OEI-h) as a potential antimicrobial agent to fight infectious diseases caused by MDR bacteria. L-OEI-h has a broad-spectrum antibacterial activity and exerts a significantly bactericidal activity within the first 5-30 min treatment, causing lysis of the cytoplasmic membrane. Importantly, the polycationic oligomer showed low toxicity against in vitro models and no visible cytotoxicity (measured by survival and health index) was noted on the in vivo model (G. mellonella), thus L-OEI-h is foreseen as a promising polymer therapeutic for the treatment of MDR K. pneumoniae infections.

scholarly journals Activity of Telavancin against Staphylococcus aureus Isolates, Including Those with Decreased Susceptibility to Ceftaroline, from Cystic Fibrosis Patients

2018 ◽  
Vol 62 (9) ◽  
Author(s):  
Melanie Roch ◽  
Maria Celeste Varela ◽  
Agustina Taglialegna ◽  
Warren E. Rose ◽  
Adriana E. Rosato
Keyword(s):  
Cystic Fibrosis ◽  
Staphylococcus Aureus ◽  
Galleria Mellonella ◽  
Therapeutic Option ◽  
The United States ◽  
Infection Model ◽  
Content Type ◽  
Complicated Skin ◽  
Hospital Acquired

ABSTRACT Methicillin-resistant Staphylococcus aureus (MRSA) acquisition in cystic fibrosis (CF) patients confers a clinical outcome worse than that in non-CF patients with an increased rate of declined lung function. Telavancin, an approved lipoglycopeptide used to treat infections due to S. aureus, has a dual mode of action causing inhibition of peptidoglycan synthesis and membrane depolarization. MRSA infections in CF patients remain an important problem with no foreseeable decline in prevalence rates. Although telavancin is currently in clinical use for the treatment of complicated skin infections and hospital-acquired pneumonia, the activity against S. aureus infections in CF patients has not been investigated. In this work, we studied the activity of telavancin against CF patient-derived S. aureus strains collected from geographically diverse CF centers in the United States. We found that the telavancin MIC90 was 0.06 μg/ml, 8-fold lower than the ceftaroline or daptomycin MIC90 and 25-fold lower than the linezolid and vancomycin MIC90. We demonstrate that telavancin at serum free concentrations has rapid bactericidal activity, with a decrease of more than 3 log10 CFU/ml being achieved during the first 4 to 6 h of treatment, performing better in this assay than vancomycin and ceftaroline, including against S. aureus strains resistant to ceftaroline. Telavancin resistance was infrequent (0.3%), although we found that it can occur in vitro in both CF- and non-CF patient-derived S. aureus strains by progressive passages with subinhibitory concentrations. Genetic analysis of telavancin-resistant in vitro mutants showed gene polymorphisms in cell wall and virulence genes and increased survival in a Galleria mellonella infection model. Thus, we conclude that telavancin represents a promising therapeutic option for infections in CF patients with potent in vitro activity and a low resistance development potential.

scholarly journals In Vitro Activity of Sulbactam-Durlobactam against Acinetobacter baumannii-calcoaceticus Complex Isolates Collected Globally in 2016 and 2017

2020 ◽  
Vol 64 (4) ◽  
Author(s):  
Sarah M. McLeod ◽  
Samir H. Moussa ◽  
Meredith A. Hackel ◽  
Alita A. Miller
Keyword(s):  
Acinetobacter Baumannii ◽  
Antibacterial Activities ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Single Amino Acid ◽  
Content Type ◽  
Level Of Activity ◽  
Severe Infections ◽  
Sources Of Infection

ABSTRACT Acinetobacter baumannii-calcoaceticus complex (ABC) organisms cause severe infections that are difficult to treat due to preexisting antibiotic resistance. Sulbactam-durlobactam (formerly sulbactam-ETX2514) (SUL-DUR) is a β-lactam–β-lactamase inhibitor combination antibiotic designed to treat serious infections caused by ABC organisms, including multidrug-resistant (MDR) strains. The in vitro antibacterial activities of SUL-DUR and comparator agents were determined by broth microdilution against 1,722 clinical isolates of ABC organisms collected in 2016 and 2017 from 31 countries across Asia/South Pacific, Europe, Latin America, the Middle East, and North America. Over 50% of these isolates were resistant to carbapenems. Against this collection of global isolates, SUL-DUR had a MIC50/MIC90 of 1/2 μg/ml compared to a MIC50/MIC90 of 8/64 μg/ml for sulbactam alone. This level of activity was found to be consistent across organisms, regions, sources of infection, and subsets of resistance phenotypes, including MDR and extensively drug-resistant isolates. The SUL-DUR activity was superior to those of the tested comparators, with only colistin having similar potency. Whole-genome sequencing of the 39 isolates (2.3%) with a SUL-DUR MIC of >4 μg/ml revealed that these strains encoded either the metallo-β-lactamase NDM-1, which durlobactam does not inhibit, or single amino acid substitutions near the active site of penicillin binding protein 3 (PBP3), the primary target of sulbactam. In summary, SUL-DUR demonstrated potent antibacterial activity against recent, geographically diverse clinical isolates of ABC organisms, including MDR isolates.

scholarly journals The Ancestral N-Terminal Domain of Big Defensins Drives Bacterially Triggered Assembly into Antimicrobial Nanonets

mBio ◽  
2019 ◽  
Vol 10 (5) ◽  
Author(s):  
Karine Loth ◽  
Agnès Vergnes ◽  
Cairé Barreto ◽  
Sébastien N. Voisin ◽  
Hervé Meudal ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antimicrobial Activity ◽  
Bactericidal Activity ◽  
Multidrug Resistant ◽  
High Salt ◽  
Clinical Isolates ◽  
Host Defense Peptides ◽  
Hydrophobic Domain ◽  
Content Type ◽  
Terminal Domain

ABSTRACT Big defensins, ancestors of β-defensins, are composed of a β-defensin-like C-terminal domain and a globular hydrophobic ancestral N-terminal domain. This unique structure is found in a limited number of phylogenetically distant species, including mollusks, ancestral chelicerates, and early-branching cephalochordates, mostly living in marine environments. One puzzling evolutionary issue concerns the advantage for these species of having maintained a hydrophobic domain lost during evolution toward β-defensins. Using native ligation chemistry, we produced the oyster Crassostrea gigas BigDef1 (Cg-BigDef1) and its separate domains. Cg-BigDef1 showed salt-stable and broad-range bactericidal activity, including against multidrug-resistant human clinical isolates of Staphylococcus aureus. We found that the ancestral N-terminal domain confers salt-stable antimicrobial activity to the β-defensin-like domain, which is otherwise inactive. Moreover, upon contact with bacteria, the N-terminal domain drives Cg-BigDef1 assembly into nanonets that entrap and kill bacteria. We speculate that the hydrophobic N-terminal domain of big defensins has been retained in marine phyla to confer salt-stable interactions with bacterial membranes in environments where electrostatic interactions are impaired. Those remarkable properties open the way to future drug developments when physiological salt concentrations inhibit the antimicrobial activity of vertebrate β-defensins. IMPORTANCE β-Defensins are host defense peptides controlling infections in species ranging from humans to invertebrates. However, the antimicrobial activity of most human β-defensins is impaired at physiological salt concentrations. We explored the properties of big defensins, the β-defensin ancestors, which have been conserved in a number of marine organisms, mainly mollusks. By focusing on a big defensin from oyster (Cg-BigDef1), we showed that the N-terminal domain lost during evolution toward β-defensins confers bactericidal activity to Cg-BigDef1, even at high salt concentrations. Cg-BigDef1 killed multidrug-resistant human clinical isolates of Staphylococcus aureus. Moreover, the ancestral N-terminal domain drove the assembly of the big defensin into nanonets in which bacteria are entrapped and killed. This discovery may explain why the ancestral N-terminal domain has been maintained in diverse marine phyla and creates a new path of discovery to design β-defensin derivatives active at physiological and high salt concentrations.

scholarly journals Daptomycin-Nonsusceptible Vancomycin-Intermediate Staphylococcus aureus Vertebral Osteomyelitis Cases Complicated by Bacteremia Treated with High-Dose Daptomycin and Trimethoprim-Sulfamethoxazole

2012 ◽  
Vol 56 (11) ◽  
pp. 5990-5993 ◽  
Author(s):  
Lisa M. Avery ◽  
Molly E. Steed ◽  
Ashley E. Woodruff ◽  
Muhammad Hasan ◽  
Michael J. Rybak
Keyword(s):  
Staphylococcus Aureus ◽  
Bactericidal Activity ◽  
Vertebral Osteomyelitis ◽  
Clinical Isolates ◽  
High Dose ◽  
Content Type ◽  
Post Hoc

ABSTRACTWe report two cases of daptomycin (DAP)-nonsusceptible (DNS) vancomycin-intermediateStaphylococcus aureus(VISA) vertebral osteomyelitis cases complicated by bacteremia treated with high-dose daptomycin and trimethoprim-sulfamethoxazole. Both patients responded rapidly and favorably to this combination. The clinical isolates from the two patients were testedpost hocin anin vitropharmacokinetic/pharmacodynamic (PK/PD) model to confirm the bactericidal activity and enhancement of daptomycin and trimethoprim-sulfamethoxazole. The combination of high-dose daptomycin and trimethoprim-sulfamethoxazole should be explored further for the treatment of DNS VISA strains.

scholarly journals d-Amino Acids Enhance the Activity of Antimicrobials against Biofilms of Clinical Wound Isolates of Staphylococcus aureus and Pseudomonas aeruginosa

2014 ◽  
Vol 58 (8) ◽  
pp. 4353-4361 ◽  
Author(s):  
Carlos J. Sanchez ◽  
Kevin S. Akers ◽  
Desiree R. Romano ◽  
Ronald L. Woodbury ◽  
Sharanda K. Hardy ◽  
...  
Keyword(s):  
Amino Acids ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Clinical Isolates ◽  
Chronic Infections ◽  
Content Type ◽  
Log Reduction ◽  
Viable Bacteria ◽  
Biofilm Bacteria

ABSTRACTWithin wounds, microorganisms predominantly exist as biofilms. Biofilms are associated with chronic infections and represent a tremendous clinical challenge. As antibiotics are often ineffective against biofilms, use of dispersal agents as adjunctive, topical therapies for the treatment of wound infections involving biofilms has gained interest. We evaluatedin vitrothe dispersive activity ofd-amino acids (d-AAs) on biofilms from clinical wound isolates ofStaphylococcus aureusandPseudomonas aeruginosa; moreover, we determined whether combinations ofd-AAs and antibiotics (clindamycin, cefazolin, oxacillin, rifampin, and vancomycin forS. aureusand amikacin, colistin, ciprofloxacin, imipenem, and ceftazidime forP. aeruginosa) enhance activity against biofilms.d-Met,d-Phe, andd-Trp at concentrations of ≥5 mM effectively dispersed preformed biofilms ofS. aureusandP. aeruginosaclinical isolates, an effect that was enhanced when they were combined as an equimolar mixture (d-Met/d-Phe/d-Trp). When combined withd-AAs, the activity of rifampin was significantly enhanced against biofilms of clinical isolates ofS. aureus, as indicated by a reduction in the minimum biofilm inhibitory concentration (MBIC) (from 32 to 8 μg/ml) and a >2-log reduction of viable biofilm bacteria compared to treatment with antibiotic alone. The addition ofd-AAs was also observed to enhance the activity of colistin and ciprofloxacin against biofilms ofP. aeruginosa, reducing the observed MBIC and the number of viable bacteria by >2 logs and 1 log at 64 and 32 μg/ml in contrast to antibiotics alone. These findings indicate that the biofilm dispersal activity ofd-AAs may represent an effective strategy, in combination with antimicrobials, to release bacteria from biofilms, subsequently enhancing antimicrobial activity.

scholarly journals Contribution of Resistance-Nodulation-Division Efflux Pump OperonsmeU1-V-W-U2-Xto Multidrug Resistance of Stenotrophomonas maltophilia

2011 ◽  
Vol 55 (12) ◽  
pp. 5826-5833 ◽  
Author(s):  
Chao-Hsien Chen ◽  
Chiang-Ching Huang ◽  
Tsao-Chuen Chung ◽  
Rouh-Mei Hu ◽  
Yi-Wei Huang ◽  
...  
Keyword(s):  
Stenotrophomonas Maltophilia ◽  
Efflux Pump ◽  
Acquired Resistance ◽  
Type Systems ◽  
Resistant Mutant ◽  
Multidrug Resistant ◽  
Content Type ◽  
Membrane Fusion Protein ◽  
Resistance Nodulation Division

ABSTRACTKJ09C, a multidrug-resistant mutant ofStenotrophomonas maltophiliaKJ, was generated byin vitroselection with chloramphenicol. The multidrug-resistant phenotype of KJ09C was attributed to overexpression of a resistance nodulation division (RND)-type efflux system encoded by an operon consisting of five genes:smeU1,smeV,smeW,smeU2, andsmeX. Proteins encoded bysmeV,smeW, andsmeXwere similar to the membrane fusion protein, RND transporter, and outer membrane protein, respectively, of known RND-type systems. The proteins encoded bysmeU1andsmeU2were found to belong to the family of short-chain dehydrogenases/reductases. Mutant KJ09C exhibited increased resistance to chloramphenicol, quinolones, and tetracyclines and susceptibility to aminoglycosides; susceptibility to β-lactams and erythromycin was not affected. The expression of thesmeU1-V-W-U2-Xoperon was regulated by the divergently transcribed LysR-type regulator genesmeRv. Overexpression of the SmeVWX pump contributed to the acquired resistance to chloramphenicol, quinolones, and tetracyclines. Inactivation ofsmeVandsmeWcompletely abolished the activity of the SmeVWX pump, whereas inactivation ofsmeXalone decreased the activity of the SmeVWX pump. The enhanced aminoglycoside susceptibility observed in KJ09C resulted from SmeX overexpression.

scholarly journals Antistaphylococcal Activity of TD-1792, a Multivalent Glycopeptide-Cephalosporin Antibiotic

2011 ◽  
Vol 56 (3) ◽  
pp. 1584-1587 ◽  
Author(s):  
Johanne Blais ◽  
Stacey R. Lewis ◽  
Kevin M. Krause ◽  
Bret M. Benton
Keyword(s):  
Staphylococcus Aureus ◽  
Multidrug Resistant ◽  
Postantibiotic Effect ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Highly Active ◽  
Antistaphylococcal Activity ◽  
Cephalosporin Antibiotic ◽  
Time Kill

ABSTRACTTD-1792 is a new multivalent glycopeptide-cephalosporin antibiotic with potent activity against Gram-positive bacteria. Thein vitroactivity of TD-1792 was tested against 527Staphylococcus aureusisolates, including multidrug-resistant isolates. TD-1792 was highly active against methicillin-susceptibleS. aureus(MIC90, 0.015 μg/ml), methicillin-resistantS. aureus, and heterogeneous vancomycin-intermediateS. aureus(MIC90, 0.03 μg/ml). Time-kill studies demonstrated the potent bactericidal activity of TD-1792 at concentrations of ≤0.12 μg/ml. A postantibiotic effect of >2 h was observed after exposure to TD-1792.

scholarly journals Topical Antibiotic Use Coselects for the Carriage of Mobile Genetic Elements Conferring Resistance to Unrelated Antimicrobials in Staphylococcus aureus

2017 ◽  
Vol 62 (2) ◽  
Author(s):  
Glen P. Carter ◽  
Mark B. Schultz ◽  
Sarah L. Baines ◽  
Anders Gonçalves da Silva ◽  
Helen Heffernan ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
New Zealand ◽  
Single Molecule ◽  
Antibiotic Use ◽  
Multidrug Resistant ◽  
Topical Antibiotic ◽  
Content Type ◽  
Topical Antibiotics ◽  
The Impact

ABSTRACTTopical antibiotics, such as mupirocin and fusidic acid, are commonly used in the prevention and treatment of skin infections, particularly those caused by staphylococci. However, the widespread use of these agents is associated with increased resistance to these agents, potentially limiting their efficacy. Of particular concern is the observation that resistance to topical antibiotics is often associated with multidrug resistance, suggesting that topical antibiotics may play a role in the emergence of multidrug-resistant (MDR) strains. New Zealand (NZ) has some of the highest globally recorded rates of topical antibiotic usage and resistance. Using a combination of Pacific Biosciences single-molecule real-time (SMRT) whole-genome sequencing, Illumina short-read sequencing, and Bayesian phylogenomic modeling on 118 new multilocus sequence type 1 (ST1) communityStaphylococcus aureusisolates from New Zealand and 61 publically available international ST1 genome sequences, we demonstrate a strong correlation between the clinical introduction of topical antibiotics and the emergence of MDR ST1S. aureus. We also providein vitroexperimental evidence showing that exposure to topical antibiotics can lead to the rapid selection of MDRS. aureusisolates carrying plasmids that confer resistance to multiple unrelated antibiotics, from within a mixed population of competitor strains. These findings have important implications regarding the impact of the indiscriminate use of topical antibiotics.

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