scholarly journals In VitroStudies Indicate a High Resistance Potential for the Lantibiotic Nisin in Staphylococcus aureus and Define a Genetic Basis for Nisin Resistance

2011 ◽  
Vol 55 (5) ◽  
pp. 2362-2368 ◽  
Author(s):  
Katy L. Blake ◽  
Chris P. Randall ◽  
Alex J. O'Neill
Keyword(s):  
Staphylococcus Aureus ◽  
Bacterial Infections ◽  
Fold Increase ◽  
Peptide Antibiotics ◽  
Uncharacterized Protein ◽  
Content Type ◽  
Development Of Resistance ◽  
Genes Encoding ◽  
Bacterial Fitness

ABSTRACTLantibiotics such as nisin (NIS) are peptide antibiotics that may have a role in the chemotherapy of bacterial infections. A perceived benefit of lantibiotics for clinical use is their low propensity to select resistance, although detailed resistance studies with relevant bacterial pathogens are lacking. Here we examined the development of resistance to NIS inStaphylococcus aureus, establishing that mutants, including small-colony variants, exhibiting substantial (4- to 32-fold) reductions in NIS susceptibility could be selected readily. Comparative genome sequencing of a single NISrmutant exhibiting a 32-fold increase in NIS MIC revealed the presence of only two mutations, leading to the substitutions V229G in the purine operon repressor, PurR, and A208E in an uncharacterized protein encoded by SAOUHSC_02955. Independently selected NISrmutants also harbored mutations in the genes encoding these products. Reintroduction of these mutations into theS. aureuschromosome alone and in combination revealed that SAOUHSC_02955(A208E) made the primary contribution to the resistance phenotype, conferring up to a 16-fold decrease in NIS susceptibility. Bioinformatic analyses suggested that this gene encodes a sensor histidine kinase, leading us to designate it “nisin susceptibility-associated sensor (nsaS).” Doubling-time determinations and mixed-culture competition assays between NISrand NISsstrains indicated that NIS resistance had little impact on bacterial fitness, and resistance was stable in the absence of selection. The apparent ease with whichS. aureuscan develop and maintain NIS resistancein vitrosuggests that resistance to NIS and other lantibiotics with similar modes of action would arise in the clinic if these agents are employed as chemotherapeutic drugs.

scholarly journals Bacteriocins of Non-aureus Staphylococci Isolated from Bovine Milk

2017 ◽  
Vol 83 (17) ◽  
Author(s):  
Domonique A. Carson ◽  
Herman W. Barkema ◽  
Sohail Naushad ◽  
Jeroen De Buck
Keyword(s):  
Staphylococcus Aureus ◽  
Bacterial Infections ◽  
Genome Mining ◽  
Bovine Milk ◽  
Gene Clusters ◽  
Antibiotic Use ◽  
Content Type ◽  
Treatment And Prevention ◽  
Whole Genomes

ABSTRACT Non-aureus staphylococci (NAS), the bacteria most commonly isolated from the bovine udder, potentially protect the udder against infection by major mastitis pathogens due to bacteriocin production. In this study, we determined the inhibitory capability of 441 bovine NAS isolates (comprising 26 species) against bovine Staphylococcus aureus. Furthermore, inhibiting isolates were tested against a human methicillin-resistant S. aureus (MRSA) isolate using a cross-streaking method. We determined the presence of bacteriocin clusters in NAS whole genomes using genome mining tools, BLAST, and comparison of genomes of closely related inhibiting and noninhibiting isolates and determined the genetic organization of any identified bacteriocin biosynthetic gene clusters. Forty isolates from 9 species (S. capitis, S. chromogenes, S. epidermidis, S. pasteuri, S. saprophyticus, S. sciuri, S. simulans, S. warneri, and S. xylosus) inhibited growth of S. aureus in vitro, 23 isolates of which, from S. capitis, S. chromogenes, S. epidermidis, S. pasteuri, S. simulans, and S. xylosus, also inhibited MRSA. One hundred five putative bacteriocin gene clusters encompassing 6 different classes (lanthipeptides, sactipeptides, lasso peptides, class IIa, class IIc, and class IId) in 95 whole genomes from 16 species were identified. A total of 25 novel bacteriocin precursors were described. In conclusion, NAS from bovine mammary glands are a source of potential bacteriocins, with >21% being possible producers, representing potential for future characterization and prospective clinical applications. IMPORTANCE Mastitis (particularly infections caused by Staphylococcus aureus) costs Canadian dairy producers $400 million/year and is the leading cause of antibiotic use on dairy farms. With increasing antibiotic resistance and regulations regarding use, there is impetus to explore bacteriocins (bacterially produced antimicrobial peptides) for treatment and prevention of bacterial infections. We examined the ability of 441 NAS bacteria from Canadian bovine milk samples to inhibit growth of S. aureus in the laboratory. Overall, 9% inhibited growth of S. aureus and 58% of those also inhibited MRSA. In NAS whole-genome sequences, we identified >21% of NAS as having bacteriocin genes. Our study represents a foundation to further explore NAS bacteriocins for clinical use.

scholarly journals Amikacin-Fosfomycin at a Five-to-Two Ratio: Characterization of Mutation Rates in Microbial Strains Causing Ventilator-Associated Pneumonia and Interactions with Commonly Used Antibiotics

2014 ◽  
Vol 58 (7) ◽  
pp. 3708-3713 ◽  
Author(s):  
A. Bruce Montgomery ◽  
Paul R. Rhomberg ◽  
Tammy Abuan ◽  
Kathie-Anne Walters ◽  
Robert K. Flamm
Keyword(s):  
Fold Increase ◽  
Serial Passage ◽  
Multidrug Resistant ◽  
Adjunctive Treatment ◽  
Ventilator Associated Pneumonia ◽  
Bacterial Strains ◽  
Content Type ◽  
Development Of Resistance

ABSTRACTThe amikacin-fosfomycin inhalation system (AFIS), a combination of antibiotics administered with an in-line nebulizer delivery system, is being developed for adjunctive treatment of ventilator-associated pneumonia (VAP). Thein vitrocharacterization of amikacin-fosfomycin (at a 5:2 ratio) described here included determining resistance selection rates for pathogens that are representative of those commonly associated with VAP (including multidrug-resistant strains) and evaluating interactions with antibiotics commonly used intravenously to treat VAP. Spontaneous resistance to amikacin-fosfomycin (5:2) was not observed for most strains tested (n, 10/14). Four strains had spontaneously resistant colonies (frequencies, 4.25 × 10−8to 3.47 × 10−10), for which amikacin-fosfomycin (5:2) MICs were 2- to 8-fold higher than those for the original strains. After 7 days of serial passage, resistance (>4-fold increase over the baseline MIC) occurred in fewer strains (n, 4/14) passaged in the presence of amikacin-fosfomycin (5:2) than with either amikacin (n, 7/14) or fosfomycin (n, 12/14) alone. Interactions between amikacin-fosfomycin (5:2) and 10 comparator antibiotics in checkerboard testing against 30 different Gram-positive or Gram-negative bacterial strains were synergistic (fractional inhibitory concentration [FIC] index, ≤0.5) for 6.7% (n, 10/150) of combinations tested. No antagonism was observed. Synergy was confirmed by time-kill methodology for amikacin-fosfomycin (5:2) plus cefepime (againstEscherichia coli), aztreonam (againstPseudomonas aeruginosa), daptomycin (againstEnterococcus faecalis), and azithromycin (againstStaphylococcus aureus). Amikacin-fosfomycin (5:2) was bactericidal at 4-fold the MIC for 7 strains tested. The reduced incidence of development of resistance to amikacin-fosfomycin (5:2) compared with that for amikacin or fosfomycin alone, and the lack of negative interactions with commonly used intravenous antibiotics, further supports the development of AFIS for the treatment of VAP.

scholarly journals Staphylococcus aureus Protein A Promotes Immune Suppression

mBio ◽  
2013 ◽  
Vol 4 (5) ◽  
Author(s):  
Scott D. Kobayashi ◽  
Frank R. DeLeo
Keyword(s):  
Staphylococcus Aureus ◽  
B Cell ◽  
Immune Evasion ◽  
Bacterial Infections ◽  
Binding Capacity ◽  
Protein A ◽  
Strong Support ◽  
The United States ◽  
Content Type

ABSTRACTStaphylococcus aureusis a prominent cause of human infections worldwide and is notorious for its ability to acquire resistance to antibiotics. Methicillin-resistantS. aureus(MRSA), in particular, is endemic in hospitals and is the most frequent cause of community-associated bacterial infections in the United States. Inasmuch as treatment options for severe MRSA infections are limited, there is need for a vaccine that protects against such infections. However, recent efforts to generate a staphylococcal vaccine have met with little success in human clinical trials. These failures are somewhat puzzling, since the vaccine antigens tested promote opsonophagocytosisin vitroand confer protection in animal infection models. One possibility is that the pathogen inhibits (and/or fails to elicit) the development of protective immunity in humans. Indeed,S. aureusproduces numerous molecules that can potentially promote immune evasion, including protein A (SpA), an immunoglobulin (Ig)-binding protein present on the bacterial surface and freely secreted into the extracellular environment. SpA binds the Fc region of antibody and the Fab regions of the B-cell receptor, processes that are known to block opsonophagocytosis and cause B-cell deathin vitro. In a recent study, Falugi et al. [F. Falugi, H. K. Kim, D. M. Missiakas, and O. Schneewind, mBio 4(5):e00575-13, 2013] showed that vaccination withspamutantS. aureusstrains lacking antibody Fc- and/or Fab-binding capacity protects against subsequent challenge with the USA300 epidemic strain. The findings provide strong support for the idea that SpA promotesS. aureusimmune evasionin vivoand form the foundation for a new approach in our efforts to develop a vaccine that prevents severeS. aureusinfections.

scholarly journals Classical β-Lactamase Inhibitors Potentiate the Activity of Daptomycin against Methicillin-Resistant Staphylococcus aureus and Colistin against Acinetobacter baumannii

2016 ◽  
Vol 61 (2) ◽  
Author(s):  
George Sakoulas ◽  
Warren Rose ◽  
Andrew Berti ◽  
Joshua Olson ◽  
Jason Munguia ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Acinetobacter Baumannii ◽  
Murine Model ◽  
Methicillin Resistant Staphylococcus Aureus ◽  
Peptide Antibiotic ◽  
Peptide Antibiotics ◽  
Methicillin Resistant ◽  
Content Type ◽  
Host Defense Peptide

ABSTRACT We asked whether beta-lactamase inhibitors (BLIs) increased the activity of daptomycin (DAP) against methicillin-resistant Staphylococcus aureus (MRSA), the peptide antibiotic colistin (COL) against the emerging Gram-negative nosocomial pathogen Acinetobacter baumannii, and the human host defense peptide cathelicidin LL37 against either pathogen. DAP and LL37 kill curves were performed with or without BLIs against MRSA, vancomycin-intermediate S. aureus (VISA), and heterogeneous VISA (hVISA). COL and LL37 kill curves were performed against A. baumannii. Boron-dipyrromethene (BODIPY)-labeled DAP binding to MRSA grown with the BLI tazobactam (TAZ) was assessed microscopically. The combination of COL plus TAZ was studied in a murine model of A. baumannii pneumonia. TAZ alone lacked in vitro activity against MRSA or A. baumannii. The addition of TAZ to DAP resulted in a 2- to 5-log10 reduction in recoverable MRSA CFU at 24 h compared to the recoverable CFU with DAP alone. TAZ plus COL showed synergy by kill curves for 4 of 5 strains of A. baumannii tested. Growth with 20 mg/liter TAZ resulted in 2- to 2.5-fold increases in the intensity of BODIPY-DAP binding to MRSA and hVISA strains. TAZ significantly increased the killing of MRSA and A. baumannii by LL37 in vitro. TAZ increased the activity of COL in a murine model of A. baumannii pneumonia. Classical BLIs demonstrate synergy with peptide antibiotics. Since BLIs have scant antimicrobial activity on their own and are thus not expected to increase selective pressure toward antibiotic resistance, their use in combination with peptide antibiotics warrants further study.

scholarly journals Cathelicidins Mitigate Staphylococcus aureus Mastitis and Reduce Bacterial Invasion in Murine Mammary Epithelium

2020 ◽  
Vol 88 (7) ◽  
Author(s):  
Paloma Araujo Cavalcante ◽  
Cameron G. Knight ◽  
Yi-Lin Tan ◽  
Ana Paula Alves Monteiro ◽  
Herman W. Barkema ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Epithelial Cells ◽  
Mammary Epithelial Cells ◽  
Mammary Epithelium ◽  
Immune Defense ◽  
Host Cells ◽  
Bacterial Invasion ◽  
Content Type ◽  
Development Of Resistance

ABSTRACT Staphylococcus aureus, an important cause of mastitis in mammals, is becoming increasingly problematic due to the development of resistance to conventional antibiotics. The ability of S. aureus to invade host cells is key to its propensity to evade immune defense and antibiotics. This study focuses on the functions of cathelicidins, small cationic peptides secreted by epithelial cells and leukocytes, in the pathogenesis of S. aureus mastitis in mice. We determined that endogenous murine cathelicidin (CRAMP; Camp) was important in controlling S. aureus infection, as cathelicidin knockout mice (Camp−/−) intramammarily challenged with S. aureus had higher bacterial burdens and more severe mastitis than did wild-type mice. The exogenous administration of both a synthetic human cathelicidin (LL-37) and a synthetic murine cathelicidin (CRAMP) (8 μM) reduced the invasion of S. aureus into the murine mammary epithelium. Additionally, this exogenous LL-37 was internalized into cultured mammary epithelial cells and impaired S. aureus growth in vitro. We conclude that cathelicidins may be potential therapeutic agents against mastitis; both endogenous and exogenous cathelicidins conferred protection against S. aureus infection by reducing bacterial internalization and potentially by directly killing this pathogen.

scholarly journals A Human Biofilm-Disrupting Monoclonal Antibody Potentiates Antibiotic Efficacy in Rodent Models of both Staphylococcus aureus and Acinetobacter baumannii Infections

2017 ◽  
Vol 61 (10) ◽  
Author(s):  
Yan Q. Xiong ◽  
Angeles Estellés ◽  
L. Li ◽  
W. Abdelhady ◽  
R. Gonzales ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Monoclonal Antibody ◽  
Acinetobacter Baumannii ◽  
Bacterial Infections ◽  
Bacterial Species ◽  
Human Monoclonal Antibody ◽  
Extracellular Dna ◽  
Content Type

ABSTRACT Many serious bacterial infections are antibiotic refractory due to biofilm formation. A key structural component of biofilm is extracellular DNA, which is stabilized by bacterial proteins, including those from the DNABII family. TRL1068 is a high-affinity human monoclonal antibody against a DNABII epitope conserved across both Gram-positive and Gram-negative bacterial species. In the present study, the efficacy of TRL1068 for the disruption of biofilm was demonstrated in vitro in the absence of antibiotics by scanning electron microscopy. The in vivo efficacy of this antibody was investigated in a well-characterized catheter-induced aortic valve infective endocarditis model in rats infected with a methicillin-resistant Staphylococcus aureus (MRSA) strain with the ability to form thick biofilms, obtained from the blood of a patient with persistent clinical infection. Animals were treated with vancomycin alone or in combination with TRL1068. MRSA burdens in cardiac vegetations and within intracardiac catheters, kidneys, spleen, and liver showed significant reductions in the combination arm versus vancomycin alone (P < 0.001). A trend toward mortality reduction was also observed (P = 0.09). In parallel, the in vivo efficacy of TRL1068 against a multidrug-resistant clinical Acinetobacter baumannii isolate was explored by using an established mouse model of skin and soft tissue catheter-related biofilm infection. Catheter segments infected with A. baumannii were implanted subcutaneously into mice; animals were treated with imipenem alone or in combination with TRL1068. The combination showed a significant reduction of catheter-adherent bacteria versus the antibiotic alone (P < 0.001). TRL1068 shows excellent promise as an adjunct to standard-of-care antibiotics for a broad range of difficult-to-treat bacterial infections.

scholarly journals Evaluation of Ceftaroline Activity against Heteroresistant Vancomycin-Intermediate Staphylococcus aureus and Vancomycin-Intermediate Methicillin-Resistant S. aureus Strains in anIn VitroPharmacokinetic/Pharmacodynamic Model: Exploring the “Seesaw Effect”

2013 ◽  
Vol 57 (6) ◽  
pp. 2664-2668 ◽  
Author(s):  
Brian J. Werth ◽  
Molly E. Steed ◽  
Glenn W. Kaatz ◽  
Michael J. Rybak
Keyword(s):  
Staphylococcus Aureus ◽  
Pharmacokinetic Parameters ◽  
Bacterial Killing ◽  
Methicillin Resistant ◽  
Content Type ◽  
Penicillin Binding Proteins ◽  
Development Of Resistance ◽  
Mutant Strains ◽  
Mrsa Strains

ABSTRACTA “seesaw effect” in methicillin-resistantStaphylococcus aureus(MRSA) has been demonstrated, whereby susceptibility to β-lactam antimicrobials increases as glyco- and lipopeptide susceptibility decreases. We investigated this effect by evaluating the activity of the anti-MRSA cephalosporin ceftaroline against isogenic pairs of MRSA strains with various susceptibilities to vancomycin in anin vitropharmacokinetic/pharmacodynamic (PK/PD) model. The activities of ceftaroline at 600 mg every 12 h (q12h) (targeted free maximum concentration of drug in serum [fCmax], 15.2 μg/ml; half-life [t1/2], 2.3 h) and vancomycin at 1 g q12h (targetedfCmax, 18 μg/ml;t1/2, 6 h) were evaluated against 3 pairs of isogenic clinical strains of MRSA that developed increased MICs to vancomycin in patients while on therapy using a two-compartment hollow-fiber PK/PD model with a starting inoculum of ∼107CFU/ml over a 96-h period. Bacterial killing and development of resistance were evaluated. Expression of penicillin-binding proteins (PBPs) 2 and 4 was evaluated by reverse transcription (RT)-PCR. The achieved pharmacokinetic parameters were 98 to 119% of the targeted values. Ceftaroline and vancomycin were bactericidal against 5/6 and 1/6 strains, respectively, at 96 h. Ceftaroline was more active against the mutant strains than the parent strains, with this difference being statistically significant for 2/3 strain pairs at 96 h. The level of PBP2 expression was 4.4× higher in the vancomycin-intermediateS. aureus(VISA) strain in 1/3 pairs. The levels of PBP2 and PBP4 expression were otherwise similar between the parent and mutant strains. These data support the seesaw hypothesis that ceftaroline, like traditional β-lactams, is more active against strains that are less susceptible to vancomycin even when the ceftaroline MICs are identical. Further research to explore these unique findings is warranted.

scholarly journals Combining the FtsZ-Targeting Prodrug TXA709 and the Cephalosporin Cefdinir Confers Synergy and Reduces the Frequency of Resistance in Methicillin-Resistant Staphylococcus aureus

2016 ◽  
Vol 60 (7) ◽  
pp. 4290-4296 ◽  
Author(s):  
Malvika Kaul ◽  
Lilly Mark ◽  
Ajit K. Parhi ◽  
Edmond J. LaVoie ◽  
Daniel S. Pilch
Keyword(s):  
Staphylococcus Aureus ◽  
Bacterial Infections ◽  
Drug Dose ◽  
Drug Induced ◽  
Methicillin Resistant ◽  
Content Type ◽  
Vancomycin Resistant ◽  
Emergence Of Resistance

ABSTRACTCombination therapy of bacterial infections with synergistic drug partners offers distinct advantages over monotherapy. Among these advantages are (i) a reduction of the drug dose required for efficacy, (ii) a reduced potential for drug-induced toxicity, and (iii) a reduced potential for the emergence of resistance. Here, we describe the synergistic actions of the third-generation oral cephalosporin cefdinir and TXA709, a new, FtsZ-targeting prodrug that we have developed with improved pharmacokinetics and enhancedin vivoefficacy against methicillin-resistantStaphylococcus aureus(MRSA) relative to earlier agents. We show that the active product of TXA709 (TXA707) acts synergistically with cefdinirin vitroagainst clinical isolates of MRSA, vancomycin-intermediateS. aureus(VISA), vancomycin-resistantS. aureus(VRSA), and linezolid-resistantS. aureus(LRSA). In addition, relative to TXA707 alone, the combination of TXA707 and cefdinir significantly reduces or eliminates the detectable emergence of resistance. We also demonstrate synergyin vivowith oral administration of the prodrug TXA709 and cefdinir in mouse models of both systemic and tissue (thigh) infections with MRSA. This synergy reduces the dose of TXA709 required for efficacy 3-fold. Viewed as a whole, our results highlight the potential of TXA709 and cefdinir as a promising combination for the treatment of drug-resistant staphylococcal infections.

scholarly journals Effects of Phage Endolysin SAL200 Combined with Antibiotics on Staphylococcus aureus Infection

2018 ◽  
Vol 62 (10) ◽  
Author(s):  
Nak-Hyun Kim ◽  
Wan Beom Park ◽  
Jeong Eun Cho ◽  
Yoon Jeong Choi ◽  
Su Jin Choi ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Bacterial Infections ◽  
Galleria Mellonella ◽  
Synergistic Effects ◽  
Splenic Tissue ◽  
Bacterial Density ◽  
Content Type ◽  
Time Kill

ABSTRACT Phages and their derivatives are increasingly being reconsidered for use in the treatment of bacterial infections due to the rising rates of antibiotic resistance. We assessed the antistaphylococcal effect of the endolysin SAL200 in combination with standard-of-care (SOC) antibiotics. The activity of SAL200 when it was combined with SOC antibiotics was assessed in vitro by checkerboard and time-kill assays and in vivo with murine bacteremia and Galleria mellonella infection models. SAL200 reduced the SOC antibiotic MICs and showed a ≥3-log10-CFU/ml reduction of Staphylococcus aureus counts within 30 min in time-kill assays. Combinations of SAL200 and SOC antibiotics achieved a sustained decrease of >2 log10 CFU/ml. SAL200 significantly lowered the blood bacterial density within 1 h by >1 log10 CFU/ml in bacteremic mice (P < 0.05 versus untreated mice), and SAL200 and SOC antibiotic combinations achieved the lowest levels of bacteremia. The bacterial density in splenic tissue at 72 h postinfection was the lowest in mice treated with SAL200 and SOC antibiotic combinations. SAL200 combined with SOC antibiotics also improved Galleria mellonella larva survival at 96 h postinfection. The combination of the phage endolysin SAL200 with SOC antistaphylococcal antibiotics showed synergistic effects in vitro and in vivo. The combination of SAL200 with SOC antibiotics could help in the treatment of difficult-to-treat S. aureus infections.

scholarly journals A Tick Antivirulence Protein Potentiates Antibiotics against Staphylococcus aureus

2017 ◽  
Vol 61 (7) ◽  
Author(s):  
Nabil M. Abraham ◽  
Lei Liu ◽  
Brandon L. Jutras ◽  
Kristen Murfin ◽  
Ali Acar ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Bacterial Infections ◽  
Repeat Region ◽  
Methicillin Resistant ◽  
Content Type ◽  
Antifreeze Glycoprotein ◽  
Infection Models ◽  
New Strategies

ABSTRACT New strategies are needed to combat antibiotic resistance, especially against pathogens such as methicillin-resistant Staphylococcus aureus. A tick antifreeze glycoprotein, IAFGP, possesses potent antibiofilm properties against a variety of clinical pathogens, including S. aureus. Synergy between IAFGP, or a peptide (P1) representative of a repeat region of the protein, with different antibiotics was assessed in vitro. Antibiotics that synergized with either IAFPG or P1 were further evaluated in vivo using vertebrate and invertebrate infection models. IAFGP readily enhanced the efficacy of antibiotics against S. aureus. Synergy with daptomycin, an antibiotic used to treat methicillin-resistant S. aureus, was observed in vitro and in vivo using iafgp-transgenic mice and flies. Furthermore, synergy with ciprofloxacin or gentamicin, antibiotics not generally used to treat S. aureus, was also perceived. The combined effect of the antibiotic and IAFGP was associated with improved permeation of the antibiotic into the cell. Our results highlight that synergy of IAFGP with antibiotics traditionally used to treat this pathogen, and enhancement of the potency of antibiotics not commonly used against this microbe, can provide novel alternative therapeutic strategies to combat bacterial infections.

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