RESUMO
Persistent and viable but non-culturable (VBNC) Pseudomonas aeruginosa cells are mainly responsible for the recurrence and non-responsiveness to antibiotics of cystic fibrosis (CF) lung infections. The sub-inhibitory antibiotic concentrations found in the CF lung in between successive therapeutic cycles can trigger the entry into the VBNC state, albeit with a strain-specific pattern. Here, we analyzed the VBNC cell induction in the biofilms of two CF P. aeruginosa isolates, exposed to starvation with/without antibiotics, and investigated the putative genetic determinants involved. Total viable bacterial cells were quantified by the validated ecfX-targeting qPCR protocol and the VBNC cells were estimated as the difference between qPCR and cultural counts. The isolates were both subjected to whole genome sequencing, with attention focused on their carriage of aminoglycoside resistance genes and on identifying mutated toxin-antitoxin and quorum sensing systems. The obtained results suggest the variable contribution of different antibiotic resistance mechanisms to VBNC cell abundance, identifying a major contribution from tobramycin efflux, mediated by MexXY efflux pump overexpression. The genome analysis evidenced putative mutation hotspots, which deserve further investigation. Therefore, drug efflux could represent a crucial mechanism through which the VBNC state is entered and a potential target for anti-persistence strategies.
Assuntos
Fibrose Cística , Infecções por Pseudomonas , Humanos , Tobramicina/farmacologia , Pseudomonas aeruginosa , Infecções por Pseudomonas/microbiologia , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Aminoglicosídeos/farmacologia , Fibrose Cística/tratamento farmacológico , Testes de Sensibilidade MicrobianaRESUMO
This study shows that Escherichia coli can be temporarily enriched in zooplankton under natural conditions and that these bacteria can belong to different phylogroups and sequence types (STs), including environmental, clinical, and animal isolates. We isolated 10 E. coli strains and sequenced the genomes of two of them. Phylogenetically, the two isolates were closer to strains isolated from poultry meat than to freshwater E. coli, albeit their genomes were smaller than those of the poultry isolates. After isolation and fluorescent protein tagging of strains ED1 and ED157, we show that Daphnia sp. can take up these strains and release them alive again, thus becoming a temporary host for E. coli. In a chemostat experiment, we show that this association does not prolong bacterial long-term survival, but at low abundances it also does not significantly reduce bacterial numbers. We demonstrate that E. coli does not belong to the core microbiota of Daphnia, suffers from competition by the natural Daphnia microbiota, but can profit from its carapax to survive in water. All in all, this study suggests that the association of E. coli with Daphnia is only temporary, but the cells are viable therein, and this might allow encounters with other bacteria for genetic exchange and potential genomic adaptation to the freshwater environment. IMPORTANCE The contamination of freshwater with feces-derived bacteria is a major concern regarding drinking water acquisition and recreational activities. Ecological interactions promoting their persistence are still very scarcely studied. This study, which analyses the survival of E. coli in the presence of zooplankton, is thus of ecological and water safety relevance.
Assuntos
Água Potável , Escherichia coli , Animais , Bactérias , Daphnia/microbiologia , Escherichia coli/genética , Fezes/microbiologia , Água Doce/microbiologia , Zooplâncton/microbiologiaRESUMO
Linezolid is a last-resort antibiotic for the treatment of severe infections caused by multidrug-resistant Gram-positive organisms; although linezolid resistance remains uncommon, the number of linezolid-resistant enterococci has increased in recent years due to worldwide spread of acquired resistance genes (cfr, optrA, and poxtA) in clinical, animal, and environmental settings. In this study, we investigated the occurrence of linezolid-resistant enterococci in marine samples from two coastal areas in Italy. Isolates grown on florfenicol-supplemented Slanetz-Bartley agar plates were investigated for their carriage of optrA, poxtA, and cfr genes; optrA was found in one Enterococcus faecalis isolate, poxtA was found in three Enterococcus faecium isolates and two Enterococcus hirae isolates, and cfr was not found. Two of the three poxtA-carrying E. faecium isolates and the two E. hirae isolates showed related pulsed-field gel electrophoresis (PFGE) profiles. Two E. faecium isolates belonged to the new sequence type 1710, which clustered in clonal complex 94, encompassing nosocomial strains. S1 PFGE/hybridization assays showed a double (chromosome and plasmid) location of poxtA and a plasmid location of optrA Whole-genome sequencing revealed that poxtA was contained in a Tn6657-like element carried by two plasmids (pEfm-EF3 and pEh-GE2) of similar size, found in different species, and that poxtA was flanked by two copies of IS1216 in both plasmids. In mating experiments, all but one strain (E. faecalis EN3) were able to transfer the poxtA gene to E. faecium 64/3. The occurrence of linezolid resistance genes in enterococci from marine samples is of great concern and highlights the need to improve practices aimed at limiting the transmission of linezolid-resistant strains to humans from environmental reservoirs.IMPORTANCE Linezolid is one of the few antimicrobials available to treat severe infections due to drug-resistant Gram-positive bacteria; therefore, the emergence of linezolid-resistant enterococci carrying transferable resistance determinants is of great concern for public health. Linezolid resistance genes (cfr, optrA, and poxtA), often plasmid located, can be transmitted via horizontal gene transfer and have the potential to spread globally. This study highlights the detection of enterococci carrying linezolid resistance genes from sediment and zooplankton samples from two coastal urban areas in Italy. The presence of clinically relevant resistant bacteria, such as linezolid-resistant enterococci, in marine environments could reflect their spillover from human and/or animal reservoirs and could indicate that coastal seawaters also might represent a source of these resistance genes.
Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana/genética , Enterococcus/isolamento & purificação , Sedimentos Geológicos/microbiologia , Linezolida/farmacologia , Zooplâncton/microbiologia , Animais , Enterococcus/efeitos dos fármacos , Enterococcus/genética , Monitoramento Ambiental , Genes Bacterianos , ItáliaRESUMO
The eradication of recurrent Pseudomonas aeruginosa (PA) lung infection in cystic fibrosis (CF) patients may be hampered by the development of persistent bacterial forms, which can tolerate antibiotics through efflux pump overexpression. After demonstrating the efflux pump inhibitory effect of the alkaloid berberine on the PA MexXY-OprM efflux pump, in this study, we tested its ability (80/320 µg/mL) to enhance tobramycin (20xMIC/1000xMIC) activity against PA planktonic/biofilm cultures. Preliminary investigations of the involvement of MexY in PA tolerance to tobramycin treatment, performed on the isogenic pair PA K767 (wild type)/K1525 (ΔmexY) growing in planktonic and biofilm cultures, demonstrated that the ΔmexY mutant K1525 produced a lower (100 and 10â¯000 times, respectively) amount of tolerant cells than that of the wild type. Next, we grew broth cultures of PAO1, PA14, and 20 PA clinical isolates (of which 13 were from CF patients) in the presence of 20xMIC tobramycin with and without berberine 80 µg/mL. Accordingly, most strains showed a greater (from 10- to 1000-fold) tolerance reduction in the presence of berberine. These findings highlight the involvement of the MexXY-OprM system in the tobramycin tolerance of PA and suggest that berberine may be used in new valuable therapeutic combinations to counteract persister survival.
Assuntos
Berberina/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Sequência de Aminoácidos , Proteínas de Bactérias , Biofilmes/efeitos dos fármacos , Fibrose Cística/microbiologia , Farmacorresistência Bacteriana , Humanos , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Estrutura Quaternária de Proteína , Infecções por Pseudomonas/tratamento farmacológico , Tobramicina/farmacologiaRESUMO
AIMS: Extensively-drug-resistant Pseudomonas aeruginosa constitutes a serious threat to patients suffering from Cystic Fibrosis (CF). In these patients, P. aeruginosa lung infection is commonly treated with aminoglycosides, but treatments are largely unsuccessful due a variety of resistance mechanisms. Here we investigate the prevalence of resistance to gentamicin, amikacin and tobramycin and the main aminoglycoside resistance genes found in P. aeruginosa strains isolated at a regional CF centre. RESULTS: A total number of 147 randomly selected P. aeruginosa strains isolated from respiratory samples sent by the Marche regional Cystic Fibrosis Centre to the Microbiology lab, were included in this study. Of these, 78 (53%) were resistant to at least one of the three aminoglycosides tested and 27% were resistant to all three antibiotics, suggesting a major involvement of a chromosome-encoded mechanism, likely MexXY-OprM efflux pump overexpression. A specific pathogenic clone (found in 7/78 of the aminoglycoside resistant strains) carrying ant(2â³)-Ia was isolated over time from the same patient, suggesting a role for this additional resistance gene in the antibiotic unresponsiveness of CF patients. CONCLUSIONS: The MexXY-OprM efflux pump is confirmed as the resistance determinant involved most frequently in P. aeruginosa aminoglycoside resistance of CF lung infections, followed by the ant(2â³)-Ia-encoded adenylyltransferase. The latter may prove to be a novel target for new antimicrobial combinations against P. aeruginosa.
Assuntos
Fibrose Cística , Pseudomonas aeruginosa , Aminoglicosídeos/farmacologia , Antibacterianos/farmacologia , Proteínas de Bactérias , Fibrose Cística/tratamento farmacológico , Fibrose Cística/genética , Humanos , Itália , Testes de Sensibilidade Microbiana , Pseudomonas aeruginosa/genéticaRESUMO
The occurrence of Pseudomonas aeruginosa (PA) persisters, including viable but non-culturable (VBNC) forms, subpopulations of tolerant cells that can survive high antibiotic doses, is the main reason for PA lung infections failed eradication and recurrence in Cystic Fibrosis (CF) patients, subjected to life-long, cyclic antibiotic treatments. In this paper, we investigated the role of subinhibitory concentrations of different anti-pseudomonas antibiotics in the maintenance of persistent (including VBNC) PA cells in in vitro biofilms. Persisters were firstly selected by exposure to high doses of antibiotics and their abundance over time evaluated, using a combination of cultural, qPCR and flow cytometry assays. Two engineered GFP-producing PA strains were used. The obtained results demonstrated a major involvement of tobramycin and bacterial cell wall-targeting antibiotics in the resilience to starvation of VBNC forms, while the presence of ciprofloxacin and ceftazidime/avibactam lead to their complete loss. Moreover, a positive correlation between tobramycin exposure, biofilm production and c-di-GMP levels was observed. The presented data could allow a deeper understanding of bacterial population dynamics during the treatment of recurrent PA infections and provide a reliable evaluation of the real efficacy of the antibiotic treatments against the bacterial population within the CF lung.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/metabolismo , Biofilmes/crescimento & desenvolvimento , Pseudomonas aeruginosa/fisiologia , Tobramicina/farmacologia , Compostos Azabicíclicos/farmacologia , Biofilmes/efeitos dos fármacos , Ceftazidima/farmacologia , Parede Celular/efeitos dos fármacos , Ciprofloxacina/farmacologia , GMP Cíclico/análogos & derivados , GMP Cíclico/metabolismo , Combinação de Medicamentos , Farmacorresistência Bacteriana Múltipla , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Técnicas In Vitro , Testes de Sensibilidade Microbiana , Pseudomonas aeruginosa/efeitos dos fármacos , Transformação BacterianaRESUMO
The natural alkaloid berberine has been demonstrated to inhibit the Pseudomonas aeruginosa multidrug efflux system MexXY-OprM, which is responsible for tobramycin extrusion by binding the inner membrane transporter MexY. To find a structure with improved inhibitory activity, we compared by molecular dynamics investigations the binding affinity of berberine and three aromatic substituents towards the three polymorphic sequences of MexY found in P. aeruginosa (PAO1, PA7, and PA14). The synergy of the combinations of berberine or berberine derivatives/tobramycin against the same strains was then evaluated by checkerboard and time-kill assays. The in silico analysis evidenced different binding modes depending on both the structure of the berberine derivative and the specific MexY polymorphism. In vitro assays showed an evident MIC reduction (32-fold and 16-fold, respectively) and a 2-3 log greater killing effect after 2 h of exposure to the combinations of 13-(2-methylbenzyl)- and 13-(4-methylbenzyl)-berberine with tobramycin against the tobramycin-resistant strain PA7, a milder synergy (a 4-fold MIC reduction) against PAO1 and PA14, and no synergy against the ΔmexXY strain K1525, confirming the MexY-specific binding and the computational results. These berberine derivatives could thus be considered new hit compounds to select more effective berberine substitutions and their common path of interaction with MexY as the starting point for the rational design of novel MexXY-OprM inhibitors.
Assuntos
Antibacterianos/química , Antibacterianos/farmacologia , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/química , Berberina/química , Berberina/farmacologia , Pseudomonas aeruginosa/efeitos dos fármacos , Sequência de Aminoácidos , Proteínas de Bactérias/genética , Berberina/análogos & derivados , Sítios de Ligação , Técnicas de Química Sintética , Sinergismo Farmacológico , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Estrutura Molecular , Polimorfismo Genético , Ligação Proteica , Pseudomonas aeruginosa/genética , Relação Estrutura-AtividadeRESUMO
NorA is the most studied efflux pump of Staphylococcus aureus and is responsible for high level resistance towards fluoroquinolone drugs. Although along the years many NorA efflux pump inhibitors (EPIs) have been reported, poor information is available about structure-activity relationship (SAR) around their nuclei and reliability of data supported by robust assays proving NorA inhibition. In this regard, we focussed efforts on the 2-phenylquinoline as a promising chemotype to develop potent NorA EPIs. Herein, we report SAR studies about the introduction of different aryl moieties on the quinoline C-2 position. The new derivative 37a showed an improved EPI activity (16-fold) with respect to the starting hit 1. Moreover, compound 37a exhibited a high potential in time-kill curves when combined with ciprofloxacin against SA-1199B (norA+). Also, 37a exhibited poor non-specific effect on bacterial membrane polarisation and showed an improvement in terms of "selectivity index" in comparison to 1.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/antagonistas & inibidores , Proteínas Associadas à Resistência a Múltiplos Medicamentos/antagonistas & inibidores , Quinolinas/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Antibacterianos/síntese química , Antibacterianos/química , Proteínas de Bactérias/metabolismo , Testes de Sensibilidade Microbiana , Estrutura Molecular , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Quinolinas/síntese química , Quinolinas/química , Staphylococcus aureus/metabolismo , Relação Estrutura-AtividadeRESUMO
Tackling antimicrobial resistance (AMR) represents a social responsibility aimed at renewing the antimicrobial armamentarium and identifying novel therapeutical approaches. Among the possible strategies, efflux pumps inhibition offers the advantage to contrast the resistance against all drugs which can be extruded. Efflux pump inhibitors (EPIs) are molecules devoid of any antimicrobial activity, but synergizing with pumps-substrate antibiotics. Herein, we performed an in silico scaffold hopping approach starting from quinolin-4-yloxy-based Staphylococcus aureus NorA EPIs by using previously built pharmacophore models for NorA inhibition activity. Four scaffolds were identified, synthesized, and modified with appropriate substituents to obtain new compounds, that were evaluated for their ability to inhibit NorA and synergize with the fluoroquinolone ciprofloxacin against resistant S. aureus strains. The two quinoline-4-carboxamide derivatives 3a and 3b showed the best results being synergic (4-fold MIC reduction) with ciprofloxacin at concentrations as low as 3.13 and 1.56 µg/mL, respectively, which were nontoxic for human THP-1 and A549 cells. The NorA inhibition was confirmed by SA-1199B ethidium bromide efflux and checkerboard assays against the isogenic pair SA-K2378 (norA++)/SA-K1902 (norA-). These in vitro results indicate the two compounds as valuable structures for designing novel S. aureus NorA inhibitors to be used in association with fluoroquinolones.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/antagonistas & inibidores , Farmacorresistência Bacteriana Múltipla , Proteínas Associadas à Resistência a Múltiplos Medicamentos/antagonistas & inibidores , Quinolinas/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Células A549 , Antibacterianos/síntese química , Humanos , Quinolinas/síntese química , Staphylococcus aureus/metabolismo , Relação Estrutura-Atividade , Células THP-1RESUMO
OBJECTIVES: To evaluate the transferability of antibiotic resistance from an MDR clade B Enterococcus faecium and to characterize the genetic elements involved. METHODS: The erm(B)-positive strain E. faecium 37BA (donor) and strains E. faecium 64/3 and Listeria welshimeri 11857RF (recipients) were used in mating experiments. Donors and transconjugants were characterized using MIC assays, PFGE, Southern blotting and hybridization, quantitative RT-PCR (RT-qPCR), next-generation sequencing and PCR mapping. RESULTS: One E. faecium and one L. welshimeri transconjugant were selected for in-depth investigation. Both acquired an â¼40 kb plasmid carrying erm(B). An additional plasmid of â¼200 kb, encoding the full conjugation machinery, was detected in the donor and in the E. faecium transconjugant. Next-generation sequencing revealed a new 40 396 bp plasmid that was designated pEf37BA; it contained 10 antibiotic resistance genes, tet(M), tet(L), erm(B), aadE, sat4, aphA, spw, lsa(E), lnu(B) and pbp5, resulting from the recombination of pM7M2 of E. faecium with an MDR chromosomal region of Erysipelothrix rhusiopathiae. A pbp5-carrying circular form was also detected. The PBP5 amino acid sequence differed from the C46 variant by two mutations (S39T and D644N). Its expression was documented in both transconjugants. pEf37BA persisted in the absence of selective pressure. CONCLUSIONS: The MDR clade B E. faecium plasmid, deriving from the recombination of two different resistance regions, carried a pbp5 element and was transferable to different bacterial species. This finding further documents the dissemination of ampicillin resistance among community-associated E. faecium and the key role of commensal strains in the spread of antibiotic resistance.
Assuntos
Farmacorresistência Bacteriana Múltipla , Enterococcus faecium/efeitos dos fármacos , Enterococcus faecium/genética , Transferência Genética Horizontal , Genótipo , Proteínas de Ligação às Penicilinas/genética , Plasmídeos , Antibacterianos/farmacologia , Southern Blotting , Mapeamento Cromossômico , Conjugação Genética , Eletroforese em Gel de Campo Pulsado , Enterococcus faecium/classificação , Enterococcus faecium/isolamento & purificação , Genes Bacterianos , Voluntários Saudáveis , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Listeria/genética , Metiltransferases/genética , Testes de Sensibilidade Microbiana , Reação em Cadeia da Polimerase em Tempo RealRESUMO
The multidrug efflux system MexXY-OprM, inside the resistance-nodulation-division family, is a major determinant of aminoglycoside resistance in Pseudomonas aeruginosa. In the fight aimed to identify potential efflux pump inhibitors among natural compounds, the alkaloid berberine emerged as a putative inhibitor of MexXY-OprM. In this work, we elucidated its interaction with the extrusor protein MexY and assessed its synergistic activity with aminoglycosides. In particular, we built an in silico model for the MexY protein in its trimeric association using both AcrB (E. coli) and MexB (P. aeruginosa) as 3D templates. This model has been stabilized in the bacterial cytoplasmic membrane using a molecular dynamics approach and used for ensemble docking to obtain the binding site mapping. Then, through dynamic docking, we assessed its binding affinity and its synergism with aminoglycosides focusing on tobramycin, which is widely used in the treatment of pulmonary infections. In vitro assays validated the data obtained: the results showed a 2-fold increase of the inhibitory activity and 2-4 log increase of the killing activity of the association berberine-tobramycin compared to those of tobramycin alone against 13/28 tested P. aeruginosa clinical isolates. From hemolytic assays, we preliminarily assessed berberine's low toxicity.
Assuntos
Aminoglicosídeos/farmacologia , Antibacterianos/farmacologia , Berberina/farmacologia , Farmacorresistência Bacteriana/efeitos dos fármacos , Pseudomonas aeruginosa/efeitos dos fármacos , Berberina/química , Simulação por Computador , Testes de Sensibilidade Microbiana , Simulação de Dinâmica MolecularRESUMO
BACKGROUND: Routine culture-based diagnosis of Pseudomonas aeruginosa lung infection in Cystic Fibrosis (CF) patients can be hampered by the phenotypic variability of the microorganism, including its transition to a Viable But Non-Culturable (VBNC) state. The aim of this study was to validate an ecfX-targeting qPCR protocol developed to detect all viable P. aeruginosa bacteria and to identify VBNC forms in CF sputum samples. METHODS: The study involved 115 P. aeruginosa strains of different origins and 10 non-P. aeruginosa strains and 88 CF sputum samples, 41 Culture-Positive (CP) and 47 Culture-Negative (CN). Spiking assays were performed using scalar dilutions of a mixture of live and dead P. aeruginosa ATCC 9027 and a pooled P. aeruginosa-free sputum batch. Total DNA from sputum samples was extracted by a commercial kit, whereas a crude extract was obtained from the broth cultures. Extracellular DNA (eDNA) interference was evaluated by comparing the qPCR counts obtained from DNase-treated and untreated aliquots of the same samples. The statistical significance of the results was assessed by the Wilcoxon test and Student's t test. RESULTS: The newly-developed qPCR protocol identified 96.6% of the P. aeruginosa isolates; no amplification was obtained with strains belonging to different species. Spiking assays supported protocol reliability, since counts always matched the amount of live bacteria, thus excluding the interference of dead cells and eDNA. The protocol sensitivity threshold was 70 cells/ml of the original sample. Moreover, qPCR detected P. aeruginosa in 9/47 CN samples and showed higher bacterial counts compared with the culture method in 10/41 CP samples. CONCLUSIONS: Our findings demonstrate the reliability of the newly-developed qPCR protocol and further highlight the need for harnessing a non-culture approach to achieve an accurate microbiological diagnosis of P. aeruginosa CF lung infection and a greater understanding of its evolution.
Assuntos
Fibrose Cística/microbiologia , Viabilidade Microbiana , Técnicas Microbiológicas , Infecções por Pseudomonas/diagnóstico , Pseudomonas aeruginosa , Reação em Cadeia da Polimerase em Tempo Real/métodos , Fibrose Cística/complicações , Feminino , Humanos , Limite de Detecção , Pulmão/microbiologia , Masculino , Técnicas Microbiológicas/normas , Infecções por Pseudomonas/complicações , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa/citologia , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/isolamento & purificação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Escarro/microbiologiaRESUMO
The MexXY-OprM multidrug efflux pump (EP) in aminoglycosides resistant Pseudomonas aeruginosa is one of the major resistance mechanisms, which is often overexpressed in strains isolated from pulmonary chronic disease such as cystic fibrosis.[1-3] In this research, we focused on the design of potential efflux pumps inhibitors, targeting MexY, the inner membrane component, in an allosteric site. Berberine[4] has been considered as lead molecule since we previously demonstrated its effectiveness in targeting MexY in laboratory reference strains.[5,6] Since this protein is often present in polymorphic variants in clinical strains, we sequenced and modeled all the mutated forms and we synthesized and evaluated by computational techniques, some berberine derivatives carrying an aromatic functionalization in its 13-C ring position. These compounds were tested inâ vitro against clinical P. aeruginosa strains for antimicrobial and antibiofilm activity. In conclusion, the results demonstrated the importance of the aromatic moiety functionalization in exerting the EP inhibitory activity in synergy with the aminoglycoside tobramycin. More, we found that aminoacidic composition of MexY in different strains must be considered for predicting potential binding site and affects the different activity of berberine derivatives. Finally, the antibiofilm effect of these new EPIs is promising, particularly for o-CH3-berberine derivative.
Assuntos
Berberina , Pseudomonas aeruginosa , Berberina/farmacologia , Transporte Biológico , Antibacterianos/farmacologia , Sítio AlostéricoRESUMO
BACKGROUND: Lung infections antibiotic treatment in Cystic Fibrosis patients (pwCF) is often complicated by bacterial persisters, including the so-called Viable but Non Culturable (VBNC) forms, live cells undetected by the routine cultural microbiological methods. This study investigated the occurrence of VBNC cells of five CF bacterial pathogens in 94 pwCF over one year and the possible associations with the patients' clinical features. METHODS: Sputum samples, recovered at routine visits and during exacerbation episodes, were analyzed for the presence of the five pathogens by both routine culture-based assays and species-specific qPCR. VBNC cells were estimated as the difference between molecular and cultural counts and their presence was matched with the clinical data in particular the therapeutic regimens. RESULTS: All but ten pwCF showed the presence of VBNC cells at least once during the study. Pseudomonas aeruginosa and methicillin-susceptible Staphylococcus aureus were the species most frequently found in the VBNC state. Only the former showed a significant association between chronic infection and VBNC cells presence; VBNC-MSSA positive patients significantly increased overtime. The presence of non culturable bacteria was generally concurrent with poor lung functionality and more frequent pulmonary exacerbations. No significant association with modulator treatment was evidenced. CONCLUSIONS: The obtained data demonstrated the overwhelming occurrence of bacterial VBNC cells in CF lung infections, warranting a constant monitoring of pwCF and underlining the need of implementing the routine culture-based assays with culture-independent techniques. This is pivotal to understand the CF bacterial population dynamics and to efficiently contrast the lung infection progression and worsening.
Assuntos
Antibacterianos/farmacologia , Biofilmes/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Vancomicina/farmacologia , Virginiamicina/análogos & derivados , Carga Bacteriana , Perfilação da Expressão Gênica , Viabilidade Microbiana/efeitos dos fármacos , Staphylococcus aureus/genética , Staphylococcus aureus/fisiologia , Virginiamicina/farmacologiaRESUMO
Swine farms are considered a hotspot of antimicrobial resistance and may contribute to the spread of antibiotic-resistant and/or pathogenic bacteria into the environment as well as to farm workers. In this study, swine fecal samples have been collected over the primary production, selecting three categories, i.e., "Suckling piglets", "Weaning pigs" and "Fatteners", in six intensive swine farms, for two years. Feces were analysed for the detection and abundance of class 1 integrons (used as proxy of antibiotic resistance and of anthropogenic pollution), and of enterococci [fecal indicator bacteria (FIB) and potentially pathogenic for humans] by quantitative Real Time PCR. Furthermore, Enterococcus faecalis and Enterococcus faecium were isolated, analysed for the presence of the intI1 gene by Real Time PCR and genetically typed by Pulsed-Field Gel Electrophoresis. Both enterococci and class 1 integrons were significantly more abundant in the Suckling piglets (p = 0.0316 and 0.0242, respectively). About 8% of the isolated enterococci were positive for the intI1 gene by Real Time PCR. E. faecalis and E. faecium were found genetically heterogeneous and no specific pattern could be identified as the driver for their presence along the pig primary production. These findings suggest that the "Suckling piglets" category of production represents the key point where to mitigate the risk of transmission of enterococci and class 1 integrons with associated antibiotic resistance genes to humans and spread into the environment.
Assuntos
Enterococcus faecium , Enterococcus , Humanos , Suínos , Animais , Integrons/genética , Fazendas , Antibacterianos/farmacologia , Fezes/microbiologia , Testes de Sensibilidade Microbiana/veterinária , Farmacorresistência Bacteriana/genéticaRESUMO
Antimicrobial resistance (AMR) represents a global health issue threatening our social lifestyle and the world economy. Efflux pumps are widely involved in AMR by playing a primary role in the development of specific mechanisms of resistance. In addition, they seem to be involved in the process of biofilm formation and maintenance, contributing to enhance the risk of creating superbugs difficult to treat. Accordingly, the identification of non-antibiotic molecules able to block efflux pumps, namely efflux pump inhibitors (EPIs), could be a promising strategy to counteract AMR and restore the antimicrobial activity of ineffective antibiotics. Herein, we enlarge the knowledge about the structure-activity relationship of 2-phenylquinoline Staphylococcus aureus NorA EPIs by reporting a new series of very potent C-6 functionalized derivatives. Best compounds significantly inhibited ethidium bromide efflux in a NorA-overexpressing S. aureus strain (SA-1199B) and strongly synergized at very low concentrations (0.20-0.78 µg/mL) with ciprofloxacin (CPX) against CPX-resistant S. aureus strains (SA-1199B and SA-K2378), as proved by checkerboard and time-kill experiments. In addition, some of these EPIs (9b and 10a) produced a post-antibiotic effect of 1.2 h and strongly enhanced antibiofilm activity of CPX against SA-1199B strain. Interestingly, at the concentrations used to reach synergy with CPX against resistant S. aureus strains, most of the EPI compounds did not show any human cell toxicity. Finally, by exploiting the recent released crystal structure of NorA, we observed that best EPI 9b highlighted a favourable docking pose, establishing some interesting interactions with key residues.
Assuntos
Staphylococcus aureus Resistente à Meticilina , Infecções Estafilocócicas , Antibacterianos/química , Antibacterianos/farmacologia , Proteínas de Bactérias , Biofilmes , Ciprofloxacina/farmacologia , Humanos , Staphylococcus aureus Resistente à Meticilina/metabolismo , Testes de Sensibilidade Microbiana , Proteínas Associadas à Resistência a Múltiplos Medicamentos , Plâncton/metabolismo , Staphylococcus aureusRESUMO
Antibiotic resistance breakers, such as efflux pump inhibitors (EPIs), represent a powerful alternative to the development of new antimicrobials. Recently, by using previously described EPIs, we developed pharmacophore models able to identify inhibitors of NorA, the most studied efflux pump of Staphylococcus aureus. Herein we report the pharmacophore-based virtual screening of a library of new potential NorA EPIs generated by an in-silico scaffold hopping approach of the quinoline core. After chemical synthesis and biological evaluation of the best virtual hits, we found the quinazoline core as the best performing scaffold. Accordingly, we designed and synthesized a series of functionalized 2-arylquinazolines, which were further evaluated as NorA EPIs. Four of them exhibited a strong synergism with ciprofloxacin and a good inhibition of ethidium bromide efflux on resistant S. aureus strains coupled with low cytotoxicity against human cell lines, thus highlighting a promising safety profile.
Assuntos
Antibacterianos/farmacologia , Proteínas de Bactérias/antagonistas & inibidores , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Proteínas Associadas à Resistência a Múltiplos Medicamentos/antagonistas & inibidores , Quinazolinas/farmacologia , Quinolinas/farmacologia , Antibacterianos/síntese química , Antibacterianos/química , Proteínas de Bactérias/metabolismo , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Humanos , Staphylococcus aureus Resistente à Meticilina/metabolismo , Testes de Sensibilidade Microbiana , Estrutura Molecular , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Quinazolinas/síntese química , Quinazolinas/química , Quinolinas/síntese química , Quinolinas/química , Relação Estrutura-AtividadeRESUMO
Methicillin resistant Staphylococcus aureus (MRSA) infections represent a major global healthcare problem. Therapeutic options are often limited by the ability of MRSA strains to grow as biofilms on medical devices, where antibiotic persistence and resistance is positively selected, leading to recurrent and chronic implant-associated infections. One strategy to circumvent these problems is the co-administration of adjuvants, which may prolong the efficacy of antibiotic treatments, by broadening their spectrum and lowering the required dosage. The marine bisindole alkaloid 2,2-bis(6-bromo-1H-indol-3-yl)ethanamine (1) and its fluorinated analogue (2) were tested for their potential use as antibiotic adjuvants and antibiofilm agents against S. aureus CH 10850 (MRSA) and S. aureus ATCC 29213 (MSSA). Both compounds showed antimicrobial activity and bisindole 2 enabled 256-fold reduction (ΣFICs = 0.5) in the minimum inhibitory concentration (MIC) of oxacillin for the clinical MRSA strain. In addition, these molecules inhibited biofilm formation of S. aureus strains, and compound 2 showed greater eradicating activity on preformed biofilm compared to 1. None of the tested molecules exerted a viable but non-culturable cells (VBNC) inducing effect at their MIC values. Moreover, both compounds exhibited no hemolytic activity and a good stability in plasma, indicating a non-toxic profile, hence, in particular compound 2, a potential for in vivo applications to restore antibiotic treatment against MRSA infections.