scholarly journals Identification of Novel Genes Responsible for Overexpression ofampCin Pseudomonas aeruginosa PAO1

2013 ◽  
Vol 57 (12) ◽  
pp. 5987-5993 ◽  
Author(s):  
Yuko Tsutsumi ◽  
Haruyoshi Tomita ◽  
Koichi Tanimoto
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Real Time Pcr ◽  
Nadh Dehydrogenase ◽  
Clinical Importance ◽  
The Other ◽  
Content Type ◽  
Pseudomonas Aeruginosa Pao1 ◽  
Development Of Resistance ◽  
Expression Of Genes ◽  
Resistant Mutants

ABSTRACTThe development of resistance to antipseudomonal penicillins and cephalosporins mediated by the chromosomalampCgene inPseudomonas aeruginosais of clinical importance. We isolated piperacillin-resistant mutants derived fromP. aeruginosaPAO1 and analyzed two mutants that had an insertion inmplandnuoN. One mutant, YT1677, was resistant to piperacillin and ceftazidime and had an insertion inmpl, which encodes UDP-N-acetylmuramate:l-alanyl-γ-d-glutamyl-meso-diaminopimelate ligase. The other mutant, YT7988, showed increased MICs of piperacillin, ceftazidime, cefepime, and cefoperazone, and the insertion was mapped tonuoN, which encodes NADH dehydrogenase I chain N. Complementation experiments demonstrated that these mutations resulted in higher levels of resistance to β-lactams. The expression of genes reported to be involved in β-lactam resistance was examined by real-time PCR in YT1677 and YT7988 mutants. Overexpression was observed for onlyampC, and other genes were expressed normally. Deletion of theampRgene in YT1677 and YT7988 resulted in decreased expression ofampC, indicating that the mutations in YT1677 and YT7988 affected the expression ofampCthrough the function of AmpR.

Antimicrobial and antioxidant activity of pulp extracts from three populations of Ziziphus lotus L.

2019 ◽  
Vol 49 (6) ◽  
pp. 1014-1028 ◽  
Author(s):  
Chaimae Rais ◽  
Asmae Driouch ◽  
Chaimae Slimani ◽  
Aymane Bessi ◽  
Mounyr Balouiri ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antioxidant Activity ◽  
Enterococcus Faecalis ◽  
Methanol Extract ◽  
The Other ◽  
Aqueous Extracts ◽  
Bacteriostatic Effect ◽  
Content Type ◽  
Ethanol Extracts ◽  
Antimicrobial And Antioxidant Activity

Purpose This paper aims to evaluate the antimicrobial and antioxidant activity of ethanol, methanol and aqueous extracts of the jujube fruit. Design/methodology/approach The fruit samples were harvested from Ziziphus lotus L. in three regions of Morocco: Aïn Chifae (Immouzer), Saiss (Fez) and Guercif. The fruit extracts were obtained by Soxhlet method using ethanol, methanol and water, and then a phytochemical screening was done for each extract. Total phenolic and total flavonoids contents were also determined. Afterward, the antimicrobial activity of the studied extracts was evaluated using the broth microdilution method. To estimate the total antioxidant effect of these extracts, the DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging and phosphomolybdate tests were performed. Findings Results showed that the highest content of polyphenols and flavonoids was found for ethanol and methanol extracts, while the lowest content was found in the aqueous extracts for all populations studied. Thus, results showed that the highest content of phenolic compounds was recorded in the population of Fez. Methanol extract of this population was the richest in polyphenols (30.36 mg/g) and in flavonoids (13.03 mg/g). The antimicrobial tests showed that Enterococcus faecalis and Pseudomonas aeruginosa were the most sensitive (6.25 mg/ml), compared to the other tested strains. Based on the minimal bactericidal concentrations/minimal fungicidal concentration or MFC/MIC ratio, it seems that ethanol extracts showed a bactericidal effect against Escherichia coli, Staphylococcus aureus and Bacillus subtillis, and a bacteriostatic effect against Enterococcus faecalis. On the other hand, the methanol extract showed bacteriostatic effect against Enterococcus faecalis and Pseudomonas aeruginosa. In addition, methanol extracts of Ziziphus lotus have significant antioxidant potent. Originality/value Methanol and ethanol extracts of Ziziphus lotus fruit have demonstrated strong antimicrobial effect. Moreover, the authors were able to show that the extract of Ziziphus lotus fruit has a very important antioxidant power.

Efficacy of a ciprofloxacin/amikacin combination against planktonic and biofilm cultures of susceptible and low-level resistant Pseudomonas aeruginosa

2019 ◽  
Vol 74 (11) ◽  
pp. 3252-3259 ◽  
Author(s):  
Anaïs Soares ◽  
Kévin Alexandre ◽  
Fabien Lamoureux ◽  
Ludovic Lemée ◽  
François Caron ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Bacterial Biofilm ◽  
The Other ◽  
Clinical Strain ◽  
Bacterial Reduction ◽  
Low Level ◽  
Mechanical Dispersion ◽  
Resistant Mutants ◽  
High Level

Abstract Background Eradicating bacterial biofilm without mechanical dispersion remains a challenge. Combination therapy has been suggested as a suitable strategy to eradicate biofilm. Objectives To evaluate the efficacy of a ciprofloxacin/amikacin combination in a model of in vitro Pseudomonas aeruginosa biofilm. Methods The antibacterial activity of ciprofloxacin and amikacin (alone, in combination and successively) was evaluated by planktonic and biofilm time–kill assays against five P. aeruginosa strains: PAO1, a WT clinical strain and three clinical strains overexpressing the efflux pumps MexAB-OprM (AB), MexXY-OprM (XY) and MexCD-OprJ (CD), respectively. Amikacin MIC was 16 mg/L for XY and ciprofloxacin MIC was 0.5 mg/L for CD. The other strains were fully susceptible to ciprofloxacin and amikacin. The numbers of total and resistant cells were determined. Results In planktonic cultures, regrowth of high-level resistant mutants was observed when CD was exposed to ciprofloxacin alone and XY to amikacin alone. Eradication was obtained with ciprofloxacin or amikacin in the other strains, or with the combination in XY and CD strains. In biofilm, bactericidal reduction after 8 h followed by a mean 4 log10 cfu/mL plateau in all strains and for all regimens was noticed. No regrowth of resistant mutants was observed whatever the antibiotic regimen. The bacterial reduction obtained with a second antibiotic used simultaneously or consecutively was not significant. Conclusions The ciprofloxacin/amikacin combination prevented the emergence of resistant mutants in low-level resistant strains in planktonic cultures. Biofilm persister cells were not eradicated, either with monotherapy or with the combination.

scholarly journals High-Level Pacidamycin Resistance in Pseudomonas aeruginosa Is Mediated by an Opp Oligopeptide Permease Encoded by theopp-fabIOperon

2013 ◽  
Vol 57 (11) ◽  
pp. 5565-5571 ◽  
Author(s):  
Anita Mistry ◽  
Mark S. Warren ◽  
John K. Cusick ◽  
RoxAnn R. Karkhoff-Schweizer ◽  
Olga Lomovskaya ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
High Frequency ◽  
Cross Resistance ◽  
Peptide Antibiotics ◽  
Content Type ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance ◽  
Resistance Mutants

ABSTRACTPacidamycins (or uridyl peptide antibiotics) possess selectivein vivoactivity againstPseudomonas aeruginosa. An important limitation for the therapeutic use of pacidamycins withP. aeruginosais the high frequency (10−6to 10−7) at which resistant mutants emerge. To elucidate the mechanism(s) of this resistance, pacidamycin-resistantP. aeruginosamutants were isolated. Two types of mutants were obtained. Type 1, or high-level resistance mutants with a pacidamycin MIC of 512 μg/ml, were more abundant, with a frequency of ∼2 × 10−6, and did not show cross-resistance with other antibiotics. Type 2, low-level resistance mutants, were isolated with a frequency of ∼10−8and had a pacidamycin MIC of 64 μg/ml (the MIC for the wild-type strain was 4 to 16 μg/ml). These mutants were cross-resistant to levofloxacin, tetracycline, and erythromycin and were shown to overexpress either the MexAB-OprM or MexCD-OprJ multidrug resistance efflux pumps. High-level resistant mutants were isolated by transposon mutagenesis and one insertion was localized tooppB, one of two periplasmic binding protein components of an oligopeptide transport system which is encoded by theopp-fabIoperon. The Opp system is required for uptake of pacidamycin across the inner membrane, since variousopp, but notfabI, mutants were resistant to high levels of pacidamycin. Both of the two putative Opp periplasmic binding proteins, OppA and OppB, were required for pacidamycin uptake. Although both impaired uptake into and efflux from the cell can cause pacidamycin resistance inP. aeruginosa, our data suggest that impaired uptake is the primary reason for the high-frequency and high-level pacidamycin resistance.

scholarly journals Activities of Mutant Prevention Concentration-Targeted Moxifloxacin and Levofloxacin against Streptococcus pneumoniae in an In Vitro Pharmacodynamic Model

2003 ◽  
Vol 47 (8) ◽  
pp. 2606-2614 ◽  
Author(s):  
George P. Allen ◽  
Glenn W. Kaatz ◽  
Michael J. Rybak
Keyword(s):  
Streptococcus Pneumoniae ◽  
Pharmacodynamic Model ◽  
The Other ◽  
Time Curve ◽  
Development Of Resistance ◽  
Concentration Time ◽  
Mutant Prevention Concentration ◽  
Resistant Mutants ◽  
Selection Of

ABSTRACT The differential effects of moxifloxacin and levofloxacin on the development of resistance in four Streptococcus pneumoniae isolates were examined by using an in vitro pharmacodynamic model. Therapeutic regimens (moxifloxacin: peak, 4.5 μg/ml; half-life [t 1/2], 12 h; and levofloxacin: peak, 6 μg/ml; t 1/2, 6 h) were tested against two fluoroquinolone-susceptible isolates (strains 79 and ATCC 49619) and KD2138 and KD2139 (parC and gyrA mutants, respectively, of ATCC 49619). Mutant prevention concentration (MPC)-targeted regimens with modified pharmacokinetics of each drug were simulated to match the area under the concentration-time curve (AUC) above the MPC for the two fluoroquinolones. Moxifloxacin MICs and MPCs (MIC/MPC) for isolates 79, ATCC 49619, KD2138, and KD2139, respectively, were 0.125 and 0.5, 0.125 and 0.5, 0.25 and 8, and 0.25 and 4 μg/ml. Levofloxacin MICs and MPCs for the same isolates were 1 and 4, 0.5 and 2, 1 and 64, and 0.5 and 32 μg/ml, respectively. Therapeutic levofloxacin concentrations led to isolation of mutants of ATCC 49619 (S79Y in ParC), KD2138 (S81Y in GyrA), and KD2139 (S79Y in ParC). Therapeutic moxifloxacin concentrations against the gyrA mutant KD2139 resulted in outgrowth of a mutant with a ParC substitution (S79Y) but caused no emergence of mutants of the other three isolates. MPC-targeted moxifloxacin (lower-than-normal peak = 0.75 to 1.5 μg/ml, administered at levofloxacin's t 1/2) caused growth of a GyrA variant (S81Y) of KD2138 and a ParC variant (S79Y) of KD2139, while no mutants of ATCC 49619 were recovered. MPC-targeted levofloxacin (higher-than-normal peak = 14.5 to 29.5 μg/ml, administered at moxifloxacin's t 1/2) against KD2138 and KD2139 did not prevent the development of the mutations observed in therapeutic regimens, but resistance in the fluoroquinolone-susceptible ATCC 49619 was no longer noted. Normalization of the respective AUC/MPC ratios of moxifloxacin and levofloxacin did not eliminate differences in resistance selectivity of the two agents in all cases. We conclude that the reduced recovery of resistant mutants of S. pneumoniae following moxifloxacin exposure compared to levofloxacin may be due to intrinsic differences between the drugs. Increasing the concentration and exposure (t 1/2) to exceed the MPC may prevent mutations from occurring in fluoroquinolone-susceptible strains. However, this strategy did not prevent the selection of secondary mutants in strains with preexisting mutations. Further study of the MPC concept to evaluate these relationships is warranted.

scholarly journals Class D β-Lactamases: Are They All Carbapenemases?

2014 ◽  
Vol 58 (4) ◽  
pp. 2119-2125 ◽  
Author(s):  
Nuno T. Antunes ◽  
Toni L. Lamoureaux ◽  
Marta Toth ◽  
Nichole K. Stewart ◽  
Hilary Frase ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Clinical Importance ◽  
Kinetic Studies ◽  
Resistance Pattern ◽  
Content Type ◽  
Narrow Spectrum ◽  
Class D ◽  
Life Threatening

ABSTRACTCarbapenem-hydrolyzing class D β-lactamases (CHDLs) are enzymes of the utmost clinical importance due to their ability to produce resistance to carbapenems, the antibiotics of last resort for the treatment of various life-threatening infections. The vast majority of these enzymes have been identified inAcinetobacterspp., notably inAcinetobacter baumannii. The OXA-2 and OXA-10 enzymes predominantly occur inPseudomonas aeruginosaand are currently classified as narrow-spectrum class D β-lactamases. Here we demonstrate that when OXA-2 and OXA-10 are expressed inEscherichia colistrain JM83, they produce a narrow-spectrum antibiotic resistance pattern. When the enzymes are expressed inA. baumanniiATCC 17978, however, they behave as extended-spectrum β-lactamases and confer resistance to carbapenem antibiotics. Kinetic studies of OXA-2 and OXA-10 with four carbapenems have demonstrated that their catalytic efficiencies with these antibiotics are in the same range as those of some recognized class D carbapenemases. These results are in disagreement with the classification of the OXA-2 and OXA-10 enzymes as narrow-spectrum β-lactamases, and they suggest that other class D enzymes that are currently regarded as noncarbapenemases may in fact be CHDLs.

scholarly journals Sequential Treatment of Biofilms with Aztreonam and Tobramycin Is a Novel Strategy for Combating Pseudomonas aeruginosa Chronic Respiratory Infections

2016 ◽  
Vol 60 (5) ◽  
pp. 2912-2922 ◽  
Author(s):  
Estrella Rojo-Molinero ◽  
María D. Macià ◽  
Rosa Rubio ◽  
Bartolomé Moyà ◽  
Gabriel Cabot ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Laser Scanning ◽  
Bactericidal Effect ◽  
Cell System ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Antibiofilm Activity ◽  
Content Type ◽  
Inhaled Antibiotics ◽  
Resistant Mutants

ABSTRACTTraditional therapeutic strategies to control chronic colonization in cystic fibrosis (CF) patients are based on the use of a single nebulized antibiotic. In this study, we evaluated the therapeutic efficacy and dynamics of antibiotic resistance inPseudomonas aeruginosabiofilms under sequential therapy with inhaled aztreonam (ATM) and tobramycin (TOB). Laboratory strains PAO1, PAOMS (hypermutable), PAOMA (mucoid), and PAOMSA (mucoid and hypermutable) and two hypermutable CF strains, 146-HSE (Liverpool epidemic strain [LES-1]) and 1089-HSE (ST1089), were used. Biofilms were developed using the flow cell system. Mature biofilms were challenged with peak and 1/10-peak concentrations of ATM (700 mg/liter and 70 mg/liter), TOB (1,000 mg/liter and 100 mg/liter), and their alternations (ATM/TOB/ATM and TOB/ATM/TOB) for 2 (t= 2), 4 (t= 4), and 6 days (t= 6). The numbers of viable cells (CFU) and resistant mutants were determined. Biofilm structural dynamics were monitored by confocal laser scanning microscopy and processed with COMSTAT and IMARIS software programs. TOB monotherapy produced an intense decrease in CFU that was not always correlated with a reduction in biomass and/or a bactericidal effect on biofilms, particularly for the CF strains. The ATM monotherapy bactericidal effect was lower, but effects on biofilm biomass and/or structure, including intense filamentation, were documented. The alternation of TOB and ATM led to an enhancement of the antibiofilm activity against laboratory and CF strains compared to that with the individual regimens, potentiating the bactericidal effect and/or the reduction in biomass, particularly at peak concentrations. Resistant mutants were not documented in any of the regimens at the peak concentrations and only anecdotally at the 1/10-peak concentrations. These results support the clinical evaluation of sequential regimens with inhaled antibiotics in CF, as opposed to the current maintenance treatments with just one antibiotic in monotherapy.

scholarly journals Dynamics of Mutations during Development of Resistance by Pseudomonas aeruginosa against Five Antibiotics

2016 ◽  
Vol 60 (7) ◽  
pp. 4229-4236 ◽  
Author(s):  
Yanfang Feng ◽  
Martijs J. Jonker ◽  
Ioannis Moustakas ◽  
Stanley Brul ◽  
Benno H. ter Kuile
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quantitative Relationship ◽  
Opportunistic Pathogen ◽  
Cellular Systems ◽  
Beta Lactam ◽  
Cellular Functions ◽  
Lower Growth ◽  
Content Type ◽  
Development Of Resistance ◽  
Considerable Morbidity

ABSTRACTPseudomonas aeruginosais an opportunistic pathogen that causes considerable morbidity and mortality, specifically during intensive care. Antibiotic-resistant variants of this organism are more difficult to treat and cause substantial extra costs compared to susceptible strains. In the laboratory,P. aeruginosarapidly developed resistance to five medically relevant antibiotics upon exposure to stepwise increasing concentrations. At several time points during the acquisition of resistance, samples were taken for whole-genome sequencing. The increase in the MIC of ciprofloxacin was linked to specific mutations ingyrA,parC, andgyrB, appearing sequentially. In the case of tobramycin, mutations infusA,HP02880,rplB, andcapDwere induced. The MICs of the beta-lactam compounds meropenem and ceftazidime and the combination of piperacillin and tazobactam correlated linearly with beta-lactamase activity but not always with individual mutations. The genes that were mutated during the development of beta-lactam resistance differed for each antibiotic. A quantitative relationship between the frequency of mutations and the increase in resistance could not be established for any of the antibiotics. When the adapted strains are grown in the absence of the antibiotic, some mutations remained and others were reversed, but this reversal did not necessarily lower the MIC. The increased MIC came at the cost of moderately reduced cellular functions or a somewhat lower growth rate. In all cases except ciprofloxacin, the increase in resistance seems to be the result of complex interactions among several cellular systems rather than individual mutations.

scholarly journals Dynamics of Mutator and Antibiotic-Resistant Populations in a Pharmacokinetic/Pharmacodynamic Model of Pseudomonas aeruginosa Biofilm Treatment

2011 ◽  
Vol 55 (11) ◽  
pp. 5230-5237 ◽  
Author(s):  
María D. Macià ◽  
José L. Pérez ◽  
Soeren Molin ◽  
Antonio Oliver
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Laser Scanning ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Resistance Development ◽  
Antibiotic Resistant ◽  
Content Type ◽  
Mutant Prevention Concentration ◽  
Resistant Mutants

ABSTRACTBiofilm growth, antibiotic resistance, and mutator phenotypes are key components of chronic respiratory infections byPseudomonas aeruginosain cystic fibrosis patients. We examined the dynamics of mutator and antibiotic-resistant populations inP. aeruginosaflow-cell biofilms, using fluorescently tagged PAO1 and PAOMS (mutator [mutS] derivative) strains. Two-day-old biofilms were treated with ciprofloxacin (CIP) for 4 days (t4) at 2 μg/ml, which correlated with the mutant prevention concentration (MPC) and provided an AUC/MIC ratio of 384 that should predict therapeutic success. Biofilms were monitored by confocal laser scanning microscopy (CLSM), and the numbers of viable cells and resistant mutants (4- and 16-fold MICs) were determined. Despite optimized pharmacokinetic/pharmacodynamic (PK/PD) parameters, CIP treatment did not suppress resistance development inP. aeruginosabiofilms. One-step resistant mutants (MexCD-OprJ or MexEF-OprN overexpression) were selected for both strains, while two-step resistant mutants (additional GyrA or GyrB mutation) were readily selected only from the mutator strain. CLSM analysis of competition experiments revealed that PAOMS, even when inoculated at a 0.01 proportion, took over the whole biofilm after only 2 days of CIP treatment outnumbering PAO1 by 3 log at t4. Our results show that mutational mechanisms play a major role in biofilm antibiotic resistance and that theoretically optimized PK/PD parameters fail to suppress resistance development, suggesting that the increased antibiotic tolerance driven by the special biofilm physiology and architecture may raise the effective MPC, favoring gradual mutational resistance development, especially in mutator strains. Moreover, the amplification of mutator populations under antibiotic treatment by coselection with resistance mutations is for the first time demonstratedin situforP. aeruginosabiofilms.

scholarly journals Activity of and Development of Resistance to Corallopyronin A, an Inhibitor of RNA Polymerase

2011 ◽  
Vol 55 (5) ◽  
pp. 2413-2416 ◽  
Author(s):  
Katherine Mariner ◽  
Martin McPhillie ◽  
Rachel Trowbridge ◽  
Catriona Smith ◽  
Alex J. O'Neill ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Antibacterial Activity ◽  
Rna Polymerase ◽  
Inhibitory Concentration ◽  
Drug Candidate ◽  
Antibacterial Drug ◽  
Content Type ◽  
Development Of Resistance ◽  
Bacterial Rna ◽  
Resistant Mutants

ABSTRACTWe explored the properties of corallopyronin A (CorA), a poorly characterized inhibitor of bacterial RNA polymerase (RNAP). It displayed a 50% inhibitory concentration of 0.73 μM against RNAP, compared with 11.5 nM for rifampin. The antibacterial activity of CorA was also inferior to rifampin, and resistant mutants ofStaphylococcus aureuswere easily selected. The mutations conferring resistance resided in therpoBandrpoCsubunits of RNAP. We conclude that CorA is not a promising antibacterial drug candidate.

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