Age of Antibiotic Resistance in MDR/XDR Clinical Pathogen of Pseudomonas aeruginosa.

Antibiotic resistance in Pseudomonas aeruginosa remains one of the most challenging phenomena of everyday medical science. The universal spread of high-risk clones of multidrug-resistant/extensively drug-resistant (MDR/XDR) clinical P. aeruginosa has become a public health threat. The P. aeruginosa bacteria exhibits remarkable genome plasticity that utilizes highly acquired and intrinsic resistance mechanisms to counter most antibiotic challenges. In addition, the adaptive antibiotic resistance of P. aeruginosa, including biofilm-mediated resistance and the formation of multidrug-tolerant persisted cells, are accountable for recalcitrance and relapse of infections. We highlighted the AMR mechanism considering the most common pathogen P. aeruginosa, its clinical impact, epidemiology, and save our souls (SOS)-mediated resistance. We further discussed the current therapeutic options against MDR/XDR P. aeruginosa infections, and described those treatment options in clinical practice. Finally, other therapeutic strategies, such as bacteriophage-based therapy and antimicrobial peptides, were described with clinical relevance.

Insights into Antimicrobial and Anti-Inflammatory Applications of Plant Bioactive Compounds.

Plants have long been thought to contribute to health promotion due to their fiber and phenolic content, as well as their inherent biological potential. The bioactive derivatives of medicinal plants are a valuable resource in the fight against serious diseases all around the world. The present review focuses on the current state of knowledge on the usage and medicinal applications of plant bioactives. Issues concerning the effect of aromatic plant derivatives on human gut microbiota and their antimicrobial and anti-inflammatory potentials are discussed and worth further exploring.

Resistance, Tolerance, Virulence and Bacterial Pathogen Fitness-Current State and Envisioned Solutions for the Near Future.

The current antibiotic crisis and the global phenomena of bacterial resistance, inherited and non-inherited, and tolerance-associated with biofilm formation-are prompting dire predictions of a post-antibiotic era in the near future. These predictions refer to increases in morbidity and mortality rates as a consequence of infections with multidrug-resistant or pandrug-resistant microbial strains. In this context, we aimed to highlight the current status of the antibiotic resistance phenomenon and the significance of bacterial virulence properties/fitness for human health and to review the main strategies alternative or complementary to antibiotic therapy, some of them being already clinically applied or in clinical trials, others only foreseen and in the research phase.

Towards Advances in Medicinal Plant Antimicrobial Activity: A Review Study on Challenges and Future Perspectives.

The increasing incidence of drug- resistant pathogens raises an urgent need to identify and isolate new bioactive compounds from medicinal plants using standardized modern analytical procedures. Medicinal plant-derived compounds could provide novel straightforward approaches against pathogenic bacteria. This review explores the antimicrobial activity of plant-derived components, their possible mechanisms of action, as well as their chemical potential. The focus is put on the current challenges and future perspectives surrounding medicinal plants antimicrobial activity. There are some inherent challenges regarding medicinal plant extracts and their antimicrobial efficacy. Appropriate and optimized extraction methodology plant species dependent leads to upgraded and selective extracted compounds. Antimicrobial susceptibility tests for the determination of the antimicrobial activity of plant extracts may show variations in obtained results. Moreover, there are several difficulties and problems that need to be overcome for the development of new antimicrobials from plant extracts, while efforts have been made to enhance the antimicrobial activity of chemical compounds. Research on the mechanisms of action, interplay with other substances, and the pharmacokinetic and/or pharmacodynamic profile of the medicinal plant extracts should be given high priority to characterize them as potential antimicrobial agents.

Resistencia enzimática en Pseudomonas aeruginosa, aspectos clínicos y de laboratorio / Enzymatic resistance in Pseudomonas aeruginosa, clinical and laboratory aspects

Resumen Pseudomonas aeruginosa es uno de los principales patógenos que causa infecciones asociadas a la atención en salud (IAAS). Su capacidad de adaptación, diseminación, resistencia intrínseca a los antimicrobianos y de adquirir nuevos mecanismos a través de elementos genéticos móviles, hacen que el tratamiento de las infecciones por este microorganismo sea un desafío para el médico clínico. Intrínsecamente, P. aeruginosa, presenta una reducida permeabilidad en la membrana externa, debido a la expresión de bombas de expulsión, y una cefalosporinasa tipo AmpC inducible. Además, P. aeruginosa es capaz de adquirir nuevos determinantes de resistencia por transferencia horizontal en forma de casetes situados en integrones, y a su vez, localizados en transposones o plásmidos. Dentro de la resistencia enzimática que presenta P. aeruginosa destacan las β-lactamasas, incluyendo aquellas de espectro extendido (BLEE) y las carbapenemasas. Pero también enzimas modificadoras de los aminoglucósidos, haciendo que este microorganismo pueda presentar fenotipos de multi-resistencia (MDR), resistencia extrema (XDR) y panresistencia (PDR) a los antimicrobianos denominados antipseudomonas, incluyendo a las nuevas cefalosporinas con inhibidores de beta-lactamasas.

Abstract Pseudomonas aeruginosa is one of the major pathogens causing healthcare-associated infections (HAI). Its capacity of adaptation, dissemination, intrinsic resistance to antimicrobials and of acquiring new mechanisms through mobile genetic elements, make the treatment of infections by this microorganism a challenge for the clinician. Intrinsically, P. aeruginosa, presents a reduced permeability in the external membrane, due to the expression of efflux pumps, and an inducible AmpC-type cephalosporinase. In addition, P. aeruginosa is able to acquire new resistance determinants by horizontal transfer in the form of cassettes located in integrons, and in turn located in transposons or plasmids. Within the enzymatic resistance that P. aeruginosa presents, betalactamases, including extended spectrum (ESBL) and carbapenemases. But also aminoglycoside modifying enzymes, stand out, causing this microorganism to present multi-resistance phenotypes (MDR), extreme resistance (XDR) and pan-resistance (PDR) to the called antipseudomonal antibiotics, including the new cephalosporins with betalactamase inhibitors.

Optimization of the In Vitro Bactericidal Effect of a Mixture of Chlorine and Sodium Gallate against Campylobacter spp. and Arcobacter butzleri.

ABSTRACT: Campylobacter spp. and Arcobacter butzleri are foodborne pathogens associated with the consumption of contaminated raw chicken meat. At the industry level, the combination of new and common antimicrobials could be used as a strategy to control the presence of pathogens in chicken carcasses. The objective of this study was to determine the bacteriostatic and bactericidal effects of a mixture of chlorine (Cl) and sodium gallate (SG) on a mixture of two Campylobacter species (Campylobacter jejuni and Campylobacter coli) and A. butzleri. Using a central composite experimental design, it was established that the optimum inhibitory SG-Cl concentration for Campylobacter spp. was 44 to 45 ppm. After 15 h of incubation, Campylobacter species growth was reduced by 37.5% and the effect of Cl was potentiated by SG at concentrations above 45 ppm. In the case of A. butzleri, optimum levels of 28 and 41 ppm were observed for SG and Cl, respectively; no synergism was reported, as this bacterium was more sensitive to lower Cl concentrations than Campylobacter. After a 20-min pretreatment with peracetic acid (50 ppm), the optimum condition to achieve a >1.0-Log CFU/mL reduction of Campylobacter spp. was exposure to 177 ppm of Cl and 44 ppm of SG for 56 min. As A. butzleri showed lower resistance to the bacteriostatic effect of the Cl-SG combination, it was assumed that optimum bactericidal conditions for Campylobacter spp. were effective to control the former; this was confirmed with subsequent validation of the model. The SG-Cl combination has bactericidal properties against Campylobacter and A. butzleri, and it may be a useful strategy to improve sanitary practices applied in the poultry industry.

Anti-Staphylococcus aureus Methicillin-Resistant (MRSA) activity of a novel 3-Chalcogenyl Indole / Atividade Anti-Staphylococcus aureus Meticilina Resistente (MRSA) de um novo composto 3-Calcogenil Indol

Objective: the development of new drugs against Methicillin-resistant Staphylococcus aureus is a priority to the World Health Organization. So, the objective of this study was to evaluate the antibacterial activity and toxicity of 5-bromo-3-((4-methoxyphenyl) sulfenyl)-1H-indole (3b) against MRSA. Methods: minimum inhibitory concentration (MIC) of 3b was determined against S. aureus ATCC 29213 and 43 clinical isolates. The time-kill assay was performed for 9 isolates. Analysis of variance followed by the post hoc Bonferroni test was used for the statistical tests. Results and conclusions: the MIC50 and MIC90 of 3b were 4 µg.mL-1 and 16 µg.mL-1 respectively. In time-kill assay, the 3b showed bactericidal activity to all evaluated isolates at concentrations of 1xMIC and 2xMIC and the re-growth effect was not observed. About the toxicity tests, 3b has not presented cytotoxicity, mutagenicity, or allergenicity. 3b had particularly good activity against MRSA demonstrating high potential for the development of new antimicrobials products.

Objetivo: o desenvolvimento de novos antimicrobianos contra Staphylococcus aureus resistentes à meticilina (MRSA) é uma prioridade para a Organização Mundial da Saúde. Então, o objetivo desse estudo foi avaliar a atividade antibacteriana e a toxicidade do 5-bromo-3-((4-metoxifenil) sulfenil)-1H-indol (3b) contra MRSA. Métodos: a concentração inibitória minima de 3b foi determinada contra S. aureus ATCC 29213 e 43 isolados clínicos. O ensaio de curva de morte foi realizado para nove isolados. Análise de variância seguida pelo teste post hoc Bonferroni foi usada para testes estatísticos. Resultados e conclusões: a MIC50 e MIC90 do 3b foi 4 µg.mL-1 e 16 µg.mL-1, respectivamente. No ensaio de curva de morte, o 3b demonstrou atividade bactericida contra todos os isolados avaliados na concentração de 1xMIC e 2xMIC e o recrescimento não foi observado. Em relação aos testes de toxicidade, 3b não apresentou citotoxicidade, mutagenicidade ou alergenicidade. 3b apresentou atividade particularmente interessante contra MRSA, demonstrando alto potencial para o desenvolvimento de novos produtos antimicrobianos.

New perspectives of purple starthistle (Centaurea calcitrapa) leaf extracts: phytochemical analysis, cytotoxicity and antimicrobial activity.

Ethnobotanical and ethnopharmacological studies of many Centaurea species indicated their potential in folk medicine so far. However, investigations of different Centaurea calcitrapa L. extracts in terms of cytotoxicity and antimicrobial activity against phytopathogens are generally scarce. The phenolic profile and broad antimicrobial activity (especially towards bacterial phytopathogens) of methanol (MeOH), 70% ethanol (EtOH), ethyl-acetate (EtOAc), 50% acetone (Me2CO) and dichloromethane: methanol (DCM: MeOH, 1: 1) extracts of C. calcitrapa leaves and their potential toxicity on MRC-5 cell line were investigated for the first time. A total of 55 phenolic compounds were identified: 30 phenolic acids and their derivatives, 25 flavonoid glycosides and aglycones. This is also the first report of the presence of centaureidin, jaceidin, kaempferide, nepetin, flavonoid glycosides, phenolic acids and their esters in C. calcitrapa extracts. The best results were obtained with EtOAc extract with lowest MIC values expressed in µg/mL ranging from 13 to 25, while methicillin resistant Staphylococcus aureus was the most susceptible strain. The most susceptible phytopathogens were Pseudomonas syringae pv. syringae, Xanthomonas campestris pv. campestris and Agrobacterium tumefaciens. The highest cytotoxicity was recorded for EtOAc and Me2CO extracts with the lowest relative and absolute IC50 values between 88 and 102 µg/mL, while EtOH extract was the least toxic with predicted relative IC50 value of 1578 µg/mL. Our results indicate that all tested extracts at concentration considered as non-toxic can be one of great importance in combat towards phytopathogenic and human pathogenic strains, as well as natural sources of antimicrobials.

Dalbavancin is a novel antimicrobial against Gram-positive pathogens: clinical experience beyond labelled indications.

Very limited labelled indications have been approved for the newer antimicrobials. Data on the clinical uses, efficacy and safety of dalbavancin are scarce, thus here we sought to describe our clinical experience. 16-month observational prospective study was performed. 19 (86%) were used under off-label indications. 10 (46%) for osteoarticular infections, 5 (23%) bloodstream infections and 3 (14%) endocarditis. To highlight, one patient received dalbavancin as long-term suppressive therapy. Most frequent use reasons were promptly hospital discharge, 11 (65%), and the presence of resistant organisms involving limited treatment options, 5 (23%). Successful outcome was observed in >95% of the patients and only 1 (4.5%) adverse event was reported. Further evidence beyond labelled indications is urgently needed. Despite the limitations, dalbavancin appears to be a safe and efficient option for adult patients who have tried and/or failed other therapies due to multidrug-resistant Gram-positive organisms.

Chemical, Metabolic, and Cellular Characterization of a FtsZ Inhibitor Effective Against Burkholderia cenocepacia.

There is an urgent need for new antimicrobials to treat the opportunistic Gram-negative Burkholderia cenocepacia, which represents a problematic challenge for cystic fibrosis patients. Recently, a benzothiadiazole derivative, C109, was shown to be effective against the infections caused by B. cenocepacia and other Gram-negative and-positive bacteria. C109 has a promising cellular target, the cell division protein FtsZ, and a recently developed PEGylated formulation make it an attractive molecule to counteract Burkholderia infections. However, the ability of efflux pumps to extrude it out of the cell represents a limitation for its use. Here, more than 50 derivatives of C109 were synthesized and tested against Gram-negative species and the Gram-positive Staphylococcus aureus. In addition, their activity was evaluated on the purified FtsZ protein. The chemical, metabolic and cellular stability of C109 has been assayed using different biological systems, including quantitative single-cell imaging. However, no further improvement on C109 was achieved, and the role of efflux in resistance was further confirmed. Also, a novel nitroreductase that can inactivate the compound was characterized, but it does not appear to play a role in natural resistance. All these data allowed a deep characterization of the compound, which will contribute to a further improvement of its properties.

Improving short antimicrobial peptides despite elusive rules for activity.

Antimicrobial peptides (AMPs) can effectively kill a broad range of life threatening multidrug-resistant bacteria, a serious threat to public health worldwide. However, despite great hopes novel drugs based on AMPs are still rare. To accelerate drug development we studied different approaches to improve the antibacterial activity of short antimicrobial peptides. Short antimicrobial peptides seem to be ideal drug candidates since they can be synthesized quickly and easily, modified and optimized. In addition, manufacturing a short peptide drug will be more cost efficient than long and structured ones. In contrast to longer and structured peptides short AMPs seem hard to design and predict. Here, we designed, synthesized and screened five different peptide libraries, each consisting of 600 9-mer peptides, against Pseudomonas aeruginosa. Each library is presenting a different approach to investigate effectiveness of an optimization strategy. The data for the 3000 peptides were analyzed using models based on fuzzy logic bioinformatics and plausible descriptors. The rate of active or superior active peptides was improved from 31.0% in a semi-random library from a previous study to 97.8% in the best new designed library. This article is part of a Special Issue entitled: Antimicrobial peptides edited by Karl Lohner and Kai Hilpert.

Efflux-mediated resistance to a benzothiadiazol derivative effective against Burkholderia cenocepacia.

Burkholderia cenocepacia is a major concern for people suffering from cystic fibrosis as it contributes to serious respiratory tract infections. The lack of drugs effective against this opportunistic pathogen, along with the high level of resistance to multiple antibiotics, render the treatment of these infections particularly difficult. Here a new compound, belonging to the 2,1,3-benzothiadiazol-5-yl family (10126109), with a bactericidal effect and a minimal inhibitory concentration (MIC) of 8 µg/ml against B. cenocepacia, is described. The compound is not cytotoxic and effective against B. cenocepacia clinical isolates and members of all the known B. cepacia complex species. Spontaneous mutants resistant to 10126109 were isolated and mutations in the MerR transcriptional regulator BCAM1948 were identified. In this way, a mechanism of resistance to this new molecule was described, which relies on the overexpression of the RND-9 efflux pump. Indeed, rnd-9 overexpression was confirmed by quantitative reverse transcription PCR, and RND-9 was identified in the membrane fractions of the mutant strains. Moreover, the increase in the MIC values of different drugs in the mutant strains, together with complementation experiments, suggested the involvement of RND-9 in the efflux of 10126109, thus indicating again the central role of efflux transporters in B. cenocepacia drug resistance.

[Ceftaroline, a new broad-spectrum cephalosporin in the era of multiresistance]. / Ceftarolina, un nuevo antimicrobiano de amplio espectro en la era de las multirresistencias.

Antimicrobial resistance has increased during the last few years, representing a public health concern. Among Gram-positive organisms, methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pneumoniae are paradigms of resistance and of the dispersion of multiresistant clones. Ceftaroline, a broad-spectrum cephalosporin that includes MRSA and penicillin-resistant S. pneumoniae, is the first ß-lactam antibiotic useful in infections due to MRSA. Phase-III clinical trials have demonstrated its efficacy in the treatment of community-acquired pneumonia and in skin and soft tissue infections, which are the current indications for ceftaroline. Due to its microbiological and pharmacological (PK/PD) profiles, these indications could be expanded to include bacteremia, endocarditis, and even osteoarticular infections. Another notable feature is the activity of this drug against Gram-negative bacilli susceptible to third generation cephalosporins, indicating that ceftaroline could be useful when these organisms are suspected or demonstrated in polymicrobial infections. Clinical follow-up of ceftaroline use will more clearly define future ceftaroline indications.

New antibiotic agents in the pipeline and how they can help overcome microbial resistance.

Bacterial resistance is a growing threat and yet few new antibiotics active against multi-resistant bacteria are being explored. A combination of falling profits, regulatory mechanisms and irrational and injudicious use of antibiotics has led to an alarming situation where some infections have no cure. In this article, we summarize the new developments that have been suggested to incentivize the pharmaceutical industries toward the field of infections. We also briefly mention the new compounds on the horizon and some newly approved compounds that might help us tide over this crisis.