Update on the treatment of Pseudomonas aeruginosa pneumonia

Synergy between Lactobacillus murinus and anti-PcrV antibody delivered in the airways to boost protection against Pseudomonas aeruginosa

Therapeutic antibodies (Ab) have revolutionized the management of multiple illnesses including respiratory tract infections (RTIs). However, anti-infectious Ab displayed several limitations including antigen restrictiveness, narrowed therapeutic windows, and limited dose in the vicinity of the target when delivered by parenteral routes. Strategies enhancing further Ab-dependent containment of infection are currently needed. Here we showed that a combination of inhaled anti-infectious Ab and probiotics is an efficient formulation to protect against lung infection. Using a mouse model of Pseudomonas aeruginosa-induced pneumonia, we demonstrated a synergistic effect reducing both bacterial burden and pro-inflammatory response affording protection against primary and secondary infections. This is the first study showing that the local combination in the airways of anti-infective Ab and probiotics subverts suboptimal potency of Ab monotherapy and provides protection against respiratory pathogen.

Pyocins and Beyond: Exploring the World of Bacteriocins in Pseudomonas aeruginosa

Pseudomonas aeruginosa significantly induces health-associated infections in a variety of species other than humans. Over the years, the opportunistic pathogen has developed resistance against commonly used antibiotics. Since most P. aeruginosa strains are multi-drug resistant, regular antibiotic treatment of its infections is becoming a dire concern, shifting the global focus towards the development of alternate antimicrobial approaches. Pyocins are one of the most diverse antimicrobial peptide combinations produced by bacteria. They have potent antimicrobial properties, mainly against bacteria from the same phylogenetic group. P. aeruginosa, whether from clinical or environmental origins, produce several different pyocins that show inhibitory activity against other multi-drug-resistant strains of P. aeruginosa. They are, therefore, good candidates for alternate therapeutic antimicrobials because they have a unique mode of action that kills antibiotic-resistant bacteria by attacking their biofilms. Here, we review pseudomonas-derived antimicrobial pyocins with great therapeutic potential against multi-drug-resistant P. aeruginosa.

Using host-mimicking conditions and a murine cutaneous abscess model to identify synergistic antibiotic combinations effective against Pseudomonas aeruginosa

Antibiotic drug combination therapy is critical for the successful treatment of infections caused by multidrug resistant pathogens. We investigated the efficacy of β-lactam and β-lactam/β-lactamase inhibitor combinations with other antibiotics, against the hypervirulent, ceftazidime/avibactam resistant Pseudomonas aeruginosa Liverpool epidemic strain (LES) B58. Although minimum inhibitory concentrations in vitro differed by up to eighty-fold between standard and host-mimicking media, combinatorial effects only marginally changed between conditions for some combinations. Effective combinations in vitro were further tested in a chronic, high-density murine infection model. Colistin and azithromycin demonstrated combinatorial effects with ceftazidime and ceftazidime/avibactam both in vitro and in vivo. Conversely, while tobramycin and tigecycline exhibited strong synergy in vitro, this effect was not observed in vivo. Our approach of using host-mimicking conditions and a sophisticated animal model to evaluate drug synergy against bacterial pathogens represents a promising approach. This methodology may offer insights into the prediction of combination therapy outcomes and the identification of potential treatment failures.

Detoxified synthetic bacterial membrane vesicles as a vaccine platform against bacteria and SARS-CoV-2

The development of vaccines based on outer membrane vesicles (OMV) that naturally bud off from bacteria is an evolving field in infectious diseases. However, the inherent inflammatory nature of OMV limits their use as human vaccines. This study employed an engineered vesicle technology to develop synthetic bacterial vesicles (SyBV) that activate the immune system without the severe immunotoxicity of OMV. SyBV were generated from bacterial membranes through treatment with detergent and ionic stress. SyBV induced less inflammatory responses in macrophages and in mice compared to natural OMV. Immunization with SyBV or OMV induced comparable antigen-specific adaptive immunity. Specifically, immunization with Pseudomonas aeruginosa-derived SyBV protected mice against bacterial challenge, and this was accompanied by significant reduction in lung cell infiltration and inflammatory cytokines. Further, immunization with Escherichia coli-derived SyBV protected mice against E. coli sepsis, comparable to OMV-immunized group. The protective activity of SyBV was driven by the stimulation of B-cell and T-cell immunity. Also, SyBV were engineered to display the SARS-CoV-2 S1 protein on their surface, and these vesicles induced specific S1 protein antibody and T-cell responses. Collectively, these results demonstrate that SyBV may be a safe and efficient vaccine platform for the prevention of bacterial and viral infections.

The action of phytochemicals in biofilm control

Covering: 2009 to 2021Antimicrobial resistance is now rising to dangerously high levels in all parts of the world, threatening the treatment of an ever-increasing range of infectious diseases. This has becoming a serious public health problem, especially due to the emergence of multidrug-resistance among clinically important bacterial species and their ability to form biofilms. In addition, current anti-infective therapies have low efficacy in the treatment of biofilm-related infections, leading to recurrence, chronicity, and increased morbidity and mortality. Therefore, it is necessary to search for innovative strategies/antibacterial agents capable of overcoming the limitations of conventional antibiotics. Natural compounds, in particular those obtained from plants, have been exhibiting promising properties in this field. Plant secondary metabolites (phytochemicals) can act as antibiofilm agents through different mechanisms of action from the available antibiotics (inhibition of quorum-sensing, motility, adhesion, and reactive oxygen species production, among others). The combination of different phytochemicals and antibiotics have revealed synergistic or additive effects in biofilm control. This review aims to bring together the most relevant reports on the antibiofilm properties of phytochemicals, as well as insights into their structure and mechanistic action against bacterial pathogens, spanning December 2008 to December 2021.

Identification of Efflux Pump Mutations in Pseudomonas aeruginosa from Clinical Samples

Efflux pumps are a specialized tool of antibiotic resistance used by Pseudomonas aeruginosa to expel antibiotics. The current study was therefore conducted to examine the expression of MexAB-OprM and MexCD-OprJ efflux pump genes. In this study, 200 samples were collected from Khyber Teaching Hospital (KTH) and Hayatabad Medical Complex (HMC) in Peshawar, Pakistan. All the isolates were biochemically identified by an Analytical Profile Index kit and at the molecular level by Polymerase Chain Reaction (PCR) utilizing specific primers for the OprL gene. A total of 26 antibiotics were tested in the current study using the guidelines of the Clinical and Laboratory Standard Institute (CLSI) and high-level resistance was shown to amoxicillin-clavulanic acid (89%) and low-level to chloramphenicol (1%) by the isolates. The antibiotic-resistant efflux pump genes MexA, MexB, OprM, MexR, MexC, MexD, OprJ, and NfxB were detected in 178 amoxicillin-clavulanic acid-resistant isolates. Mutations were detected in MexA, MexB, and OprM genes but no mutation was found in the MexR gene as analyzed by I-Mutant software. Statistical analysis determined the association of antibiotics susceptibility patterns by ANOVA: Single Factor p = 0.05. The in silico mutation impact on the protein structure stability was determined via the Dynamut server, which revealed the mutations might increase the structural stability of the mutants. The docking analysis reported that MexA wild protein showed a binding energy value of −6.1 kcal/mol with meropenem and the mexA mutant (E178K) value is −6.5 kcal/mol. The mexB wild and mutant binding energy value was −5.7 kcal/mol and −8.0 kcal/mol, respectively. Efflux pumps provide resistance against a wide range of antibiotics. Determining the molecular mechanisms of resistance in P. aeruginosa regularly will contribute to the efforts against the spread of antibiotic resistance globally.

Prevalence of metallo-β-lactamases as a correlate of multidrug resistance among clinical Pseudomonas aeruginosa isolates in Nepal

Pseudomonas aeruginosa is an opportunistic human pathogen that has developed antibiotic resistance (AR) and causes a range of illnesses, including respiratory pneumonia, gastrointestinal infections, keratitis, otitis media and bacteremia in patients with compromised immune system. The production of metallo-β-lactamases (MBLs) is one of the major mechanisms of AR in this bacterium with ensuing infections difficult to treat. The main goal of this study was to provide a quantitative estimate of MBLs producing clinical P. aeruginosa isolates among the Nepalese patients and determine if MBL correlates with multi-drug resistance (MDR). Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guideline was followed for meta-analysis of relevant literature using PubMed, Research4Life, and Google Scholar. The prevalence of MBLs in P. aeruginosa from clinical samples was determined using R 4.1.2 for data pooled from studies published until 2021. The meta-analysis of a total of 19 studies selected (of 6038 studies for which titles and abstracts were reviewed) revealed the prevalence of MBLs producing P. aeruginosa (MBL-PA) was 14 % (95 % CI: 0.10-0.19) while MDR isolates among P. aeruginosa was 42 % (95 % CI: 0.30-0.55) in Nepal. Combined Disc Test was predominantly used phenotypic method for confirming MBLs phenotypes among the studies. Sputum was the most common specimen from which MBL-PA was recovered. A significant positive correlation was observed between MDR and MBL production in P. aeruginosa. We conclude that MBL producing strains are widespread among the clinical isolates of P. aeruginosa in Nepal and responsible for emerging MDR strains. It is paramount that antibiotics prescription against the bacterium should be monitored closely and alternative therapeutic modalities against MBL-PA explored.

Treatment Heterogeneity in Pseudomonas aeruginosa Pneumonia

We have previously identified substantial antibiotic treatment heterogeneity, even among organism-specific and site-specific infections with treatment guidelines. Therefore, we sought to quantify the extent of treatment heterogeneity among patients hospitalized with P. aeruginosa pneumonia in the national Veterans Affairs Healthcare System from Jan-2015 to Apr-2018. Daily antibiotic exposures were mapped from three days prior to culture collection until discharge. Heterogeneity was defined as unique patterns of antibiotic treatment (drug and duration) not shared by any other patient. Our study included 5300 patients, of whom 87.5% had unique patterns of antibiotic drug and duration. Among patients receiving any initial antibiotic/s with a change to at least one anti-pseudomonal antibiotic (n = 3530, 66.6%) heterogeneity was 97.2%, while heterogeneity was 91.5% in those changing from any initial antibiotic/s to only anti-pseudomonal antibiotics (n = 576, 10.9%). When assessing heterogeneity of anti-pseudomonal antibiotic classes, irrespective of other antibiotic/s received (n = 4542, 85.7%), 50.5% had unique patterns of antibiotic class and duration, with median time to first change of three days, and a median of two changes. Real-world evidence is needed to inform the development of treatment pathways and antibiotic stewardship initiatives based on clinical outcome data, which is currently lacking in the presence of such treatment heterogeneity.

Colistin conditioning surfaces combined with antimicrobial treatment to prevent ventilator-associated infections

Biofilm formation on endotracheal tubes (ETT) is an important factor in the development of ventilator-associated pneumonia (VAP). This work aimed to investigate the effectiveness of colistin (COL) against the early stages of biofilm formation by Pseudomonas aeruginosa. Two strategies were used: pre-conditioning the adhesion surfaces with COL before biofilm formation and growing biofilms in its presence. The combined effect of treating P. aeruginosa 24-hours old biofilms with Ciprofloxacin (CIP) or colistin (COL) on clean and COL-conditioned surfaces was also assessed. Random deposition of COL residues altered the physico-chemical properties of the adhesion surfaces and impaired biofilm formation. Moreover, as a consequence of the reduced amount of biofilms attached to COL conditioned surfaces, adhered cells became more exposed to the subsequent action of CIP or COL, suggesting a combined outcome of prophylactic and therapeutic COL-based strategies. Results highlighted the promising use of COL to prevent the establishment of biofilms on ETT.

A novel fully human recombinant antibody neutralizing the α-hemolysin of Staphylococcus aureus

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to almost all β-lactam antibiotics. Hence, new ways to control MRSA infection, such as antibacterial antibodies, need to be explored. α-hemolysin is the most important virulence factor widely expressed in S. aureus. This study aimed to develop a new fully human antibody against α-hemolysin of S. aureus and research its neutralizing effect.

RESULTS

The single-chain antibody fragments(scFvs)against S. aureus were screened from a fully human scFv library using phage display technology. The selected scFvs had good binding affinities to α-hemolysin and S. aureus. The IgG-like scFv-Fc inserted into the pcDNA3.1 or pMH3 vector was expressed in HEK293F suspension cells to extend the half-life and restore Fc function. The size of purified scFv-Fc was about 55 kDa. The functions of expressed scFv-Fcs against α-hemolysin were validated. The cytotoxicity assays showed that scFv555-Fc had better protective effects on A549 cells than other scFv-Fcs. The results of anti-rabbit erythrocyte lysis and A549 cell apoptosis assay confirmed that scFv555-Fc had a significant neutralizing effect on α-hemolysin. The scFv555-Fc was used to construct the docking model of antigen-antibody complexes using Discovery Studio software. It predicted that the key binding sites of α-hemolysin were TYR28, LYS37, PHE39, ARG56, and LYS58, which might be the key toxic sites of α-hemolysin.

CONCLUSION

A novel fully human scFv-Fc antibody neutralizing the α-hemolysin toxin of S. aureus was successfully developed. The findings might provide a new theoretical basis and treatment method for preventing MRSA infection.

Impact of the immune response modification by lysophosphatidylcholine in the efficacy of antibiotic therapy of experimental models of peritoneal sepsis and pneumonia by Pseudomonas aeruginosa: LPC therapeutic effect in combined therapy

INTRODUCTION

Immune response stimulation may be an adjuvant to antimicrobial treatment. Here, we evaluated the impact of immune response modification by lysophosphatidylcholine (LPC), combined with imipenem or ceftazidime, in murine models of peritoneal sepsis (PS) and pneumonia induced by Pseudomonas aeruginosa.

METHODS

The imipenem and ceftazidime-susceptible strain (Pa39) and imipenem and ceftazidime-resistant strain (Pa238) were used. Ceftazidime pharmacokinetic and pharmacodynamic parameters were determined. The therapeutic efficacy and TNF-α and IL-10 levels were determined in murine models of PS and pneumonia induced by Pa39 and Pa238 and treated with LPC, imipenem or ceftazidime, alone or in combination.

RESULTS

In the PS model, LPC+ceftazidime reduced spleen and lung Pa238 concentrations (-3.45 and -3.56log₁₀CFU/g; P<0.05) to a greater extent than ceftazidime monotherapy, while LPC+imipenem maintained the imipenem efficacy (-1.66 and -1.45log₁₀CFU/g; P>0.05). In the pneumonia model, LPC+ceftazidime or LPC+imipenem reduced the lung Pa238 concentrations (-2.37log₁₀CFU/g, P=0.1, or -1.35log₁₀CFU/g, P=0.75). For Pa39, no statistically significant difference was observed in the PS and pneumonia models between combined therapy and monotherapy. Moreover, LPC+imipenem and LPC+ceftazidime significantly decreased and increased the TNF-α and IL-10 levels, respectively, in comparison with the untreated controls and monotherapies.

CONCLUSIONS

These results demonstrate the impact of immune response modification by LPC plus antibiotics on the prognosis of infections induced by ceftazidime-resistant P. aeruginosa.

Aptamer-Based Antibacterial and Antiviral Therapy against Infectious Diseases

Nucleic acid aptamers are single-stranded DNA or RNA molecules selected in vitro that can bind to a broad range of targets with high affinity and specificity. As promising alternatives to conventional anti-infective agents, aptamers have gradually revealed their potential in the combat against infectious diseases. This article provides an overview on the state-of-art of aptamer-based antibacterial and antiviral therapeutic strategies. Diverse aptamers targeting pathogen-related components or whole pathogenic cells are summarized according to the species of microorganisms. These aptamers exhibited remarkable in vitro and/or in vivo inhibitory effect for pathogenic invasion, enzymatic activities, or viral replication, even for some highly drug-resistant strains and biofilms. Aptamer-mediated drug delivery and controlled drug release strategies are also included herein. Critical technical barriers of therapeutic aptamers are briefly discussed, followed by some future perspectives for their implementation into clinical utility.

Genomic Characterization of Imipenem- and Imipenem-Relebactam-Resistant Clinical Isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen and a major cause of nosocomial infections. The global spread of carbapenem-resistant strains is growing rapidly and has become a major public health challenge. Imipenem-relebactam (I/R) is a novel carbapenem-beta-lactamase inhibitor combination that can overcome carbapenem resistance. In this study, we aimed to understand the mechanism underlying resistance to imipenem and imipenem-relebactam. For this purpose, we performed a genomic comparison of 40 new clinical P. aeruginosa strains with different antibiotic sensitivity patterns as well as the presence/absence of carbapenemases. Results indicated the presence of a reduced flexible genome (15% total) mostly represented by phages and defense mechanisms against them, showing an important role in evolution and pathogenicity. We found a high diversity of antibiotic resistance genes grouped in small clusters mobilized via integrative and conjugative elements and facilitated by the high homologous recombination detected. Ortholog genes were found in several pathogenic strains from distantly related taxa in different mobile elements with a global distribution. The microdiversity found in those strains without carbapenemases did not reveal a clear pattern that could be associated with carbapenem resistance, suggesting multiple mechanisms of resistance in the core genome. Our results provide new insight into the dynamics and high genomic plasticity by which clinical strains of P. aeruginosa acquire resistance. This knowledge can be applied to other multidrug-resistant microbes to create predictive frameworks for assessing common molecular mechanisms of antibiotic resistance and integrated into new strategies for their prevention.

IMPORTANCE The growing emergence and spread of carbapenem-resistant pathogens worldwide exacerbate the clinical challenge of treating these infections. Given the importance of carbapenems for the treatment of infections caused by Pseudomonas aeruginosa, this study aimed to investigate the underlying genomic properties of the clinical isolates that exhibited resistance to imipenem and imipenem-relebactam. This information will enhance our ability to forecast traits of resistant strains and design reliable treatments against this important threat. Our results provide new insight into the dynamics and high genomic plasticity by which clinical strains of P. aeruginosa acquire resistance as well as offers a methodology that can be applied to many other opportunistic pathogens with broad antibiotic resistance.

Fluoroquinolone resistance contributing mechanisms and genotypes of ciprofloxacin- unsusceptible Pseudomonas aeruginosa strains in Iran: emergence of isolates carrying qnr/aac(6)-Ib genes

BACKGROUND

Fluoroquinolones (FQs) including ciprofloxacin (CIP) are key antibiotics for the treatment of Pseudomonas aeruginosa infections, but resistance to FQs is developing as a result of chromosomal mutations or efflux pump effects. Plasmid-mediated quinolone resistance (PMQR) has been recently reported in the Enterobacteriaceae family. This study aimed to investigate the mechanisms of CIP insusceptibility in P. aeruginosa isolates from ICU patients and to characterize their genotypes.

METHODS

A total of 40 ciprofloxacin unsusceptible (CIP-US) P. aeruginosa isolates from Tehran hospitals were recruited in this study. A broth microdilution assay was performed to find acquired resistance profiles of the isolates. All isolates were screened for target-site mutations (gyrA and parC), PMQR genes, and efflux pumps (mexB, D, Y, and E) expression. Clonality was determined by random amplified polymorphic DNA (RAPD)-PCR, and genotyping was performed on 5 selected isolates by analyzing 7 loci in the existing multilocus sequence typing scheme.

RESULTS

Thirty-eight out of 40 CIP-US isolates (95%) were categorized as MDR. Seven (17.5%) had gyrA mutation in codons 83, and no mutation was detected in parC; 77.5% of the isolates were positive for PMQR genes. Among PMQR genes, qnrB (30%), qnrC (35%), and qnrD (30%) predominated, while qnrA, qnrS, and aac(6)-Ib genes were harbored by 20.5%, 12.5%, and 15% of the isolates respectively. Efflux pump protein expression was observed in 35% of the isolates. After RAPD-PCR, 19 different genotypes were yielded, and 5 of them were classified into sequence types (STs): 773, 1160, 2011, 2386, and 359.

CONCLUSION

In this first-time study on P. aeruginosa CIP-US strains from Iranian ICU patients, three main CIP unsusceptibility mechanisms were investigated. A single mutation in one CIP target enzyme could explain high CIP resistance. qnr genes in the isolates can be considered as a CIP-unsusceptibility mechanism among studied isolates. Efflux pumps have more contribution in multidrug resistance than CIP susceptibility. CIP-US isolates of this study have not spread from distinct clonal strains and probably emerged from different sources. STs identified for the first time in this study in Iran should be considered as emerging MDR strains.

Pseudomonas aeruginosa Biofilm Formation and Its Control

Microbes are hardly seen as planktonic species and are most commonly found as biofilm communities in cases of chronic infections. Biofilms are regarded as a biological condition, where a large group of microorganisms gets adhered to a biotic or abiotic surface. In this context, Pseudomonas aeruginosa, a Gram-negative nosocomial pathogen is the main causative organism responsible for life-threatening and persistent infections in individuals affected with cystic fibrosis and other lung ailments. The bacteria can form a strong biofilm structure when it adheres to a surface suitable for the development of a biofilm matrix. These bacterial biofilms pose higher natural resistance to conventional antibiotic therapy due to their multiple tolerance mechanisms. This prevailing condition has led to an increasing rate of treatment failures associated with P. aeruginosa biofilm infections. A better understanding of the effect of a diverse group of antibiotics on established biofilms would be necessary to avoid inappropriate treatment strategies. Hence, the search for other alternative strategies as effective biofilm treatment options has become a growing area of research. The current review aims to give an overview of the mechanisms governing biofilm formation and the different strategies employed so far in the control of biofilm infections caused by P. aeruginosa. Moreover, this review can also help researchers to search for new antibiofilm agents to tackle the effect of biofilm infections that are currently imprudent to conventional antibiotics.

In vitro effectiveness of biapenem against IMP-producing Enterobacteriaceae

The options available for treating infections with carbapenemase-producing Enterobacteriaceae (CPE) are limited; with the increasing threat of these infections, new treatments are urgently needed. Biapenem (BIPM) is a carbapenem, and limited data confirming its in vitro killing effect against CPE are available. In this study, we examined the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of BIPM for 14 IMP-1-producing Enterobacteriaceae strains isolated from the Okayama region in Japan. The MICs against almost all the isolates were lower than 0.5 µg ml^-1, indicating susceptibility to BIPM, while approximately half of the isolates were confirmed to be bacteriostatic to BIPM. However, initial killing to a 99.9 % reduction was observed in seven out of eight strains in a time-kill assay. Despite the small data set, we concluded that the in vitro efficacy of BIPM suggests that the drug could be a new therapeutic option against infection with IMP-producing CPE.

Absence of Light Exposure Increases Pathogenicity of Pseudomonas aeruginosa Pneumonia-Associated Clinical Isolates

Pseudomonas aeruginosa can alter its lifestyle in response to changes in environmental conditions. The switch to a pathogenic host-associated lifestyle can be triggered by the luminosity settings, resorting to at least one photoreceptor which senses light and regulates cellular processes. This study aimed to address how light exposure affects the dynamic and adaptability of two P. aeruginosa pneumonia-associated isolates, HB13 and HB15. A phenotypic characterization of two opposing growth conditions, constant illumination and intensity of full-spectrum light and total absence of light, was performed. Given the nature of P. aeruginosa pathogenicity, distinct fractions were characterized, and its inherent pathogenic potential screened by comparing induced morphological alterations and cytotoxicity against human pulmonary epithelial cells (A549 cell line). Growth in the dark promoted some virulence-associated traits (e.g., pigment production, LasA proteolytic activity), which, together with higher cytotoxicity of secreted fractions, supported an increased pathogenic potential in conditions that better mimic the lung microenvironment of P. aeruginosa. These preliminary findings evidenced that light exposure settings may influence the P. aeruginosa pathogenic potential, likely owing to differential production of virulence factors. Thus, this study raised awareness towards the importance in controlling light conditions during bacterial pathogenicity evaluation approaches, to more accurately interpret bacterial responses.

Extract From Tetrastigma hemsleyanum Leaf Alleviates Pseudomonas aeruginosa Lung Infection: Network Pharmacology Analysis and Experimental Evidence

Tetrastigma hemsleyanum Diels & Gilg (T. hemsleyanum) has attracted much attention due to its ability on pneumonia, bronchitis, and immune-related diseases, while its functional components and underlying mechanism of action on pneumonia have not been fully elucidated. Herein, we used a systematic network pharmacology approach to explore the action mechanism of T. hemsleyanum leaf in the treatment of pneumonia. In this study, the results of network pharmacology demonstrated that there were 34 active components and 80 drug-disease targets in T. hemsleyanum leaf, which were strongly in connection with signal transduction, inflammatory response, and the oxidation-reduction process. Subsequently, a mouse model of pneumonia induced by Pseudomonas aeruginosa (P. aeruginosa) was established to validate the predicted results of network pharmacology. In the animal experiments, aqueous extract of T. hemsleyanum leaf (EFT) significantly attenuated the histopathological changes of lung tissue in P. aeruginosa-induced mice and reduced the number of bacterial colonies in BALFs by 96.84% (p < 0.01). Moreover, EFT treatment suppressed the increase of pro-inflammatory cytokines IL-17, IL-6, and TNF-α in lung tissues triggered by P. aeruginosa, which led to the increase of Th17 cells (p < 0.05). High concentration of EFT treatment (2.0 g/kg) obviously increased the anti-inflammatory cytokine levels, accompanied by the enhancement of Treg proportion in a dose-dependent manner and a notable reversal of transcription factor RORγt expression. These findings demonstrated that network pharmacology was a useful tool for TCM research, and the anti-inflammatory effect of EFT was achieved by maintaining Th17/Treg immune homeostasis and thereby suppressing the inflammatory immune response.

A Comparative Review on Current and Future Drug Targets Against Bacteria & Malaria

Long before the discovery of drugs like 'antibiotic and anti-parasitic drugs', the infectious diseases caused by pathogenic bacteria and parasites remain as one of the major causes of morbidity and mortality in developing and underdeveloped countries. The phenomenon by which the organism exerts resistance against two or more structurally unrelated drugs is called multidrug resistance (MDR) and its emergence has further complicated the treatment scenario of infectious diseases. Resistance towards the available set of treatment options and poor pipeline of novel drug development puts an alarming situation. A universal goal in the post-genomic era is to identify novel targets/drugs for various life-threatening diseases caused by such pathogens. This review is conceptualized in the backdrop of drug resistance in two major pathogens i.e. "Pseudomonas aeruginosa" and "Plasmodium falciparum". In this review, the available targets and key mechanisms of resistance of these pathogens have been discussed in detail. An attempt has also been made to analyze the common drug targets of bacteria and malaria parasite to overcome the current drug resistance scenario. The solution is also hypothesized in terms of a present pipeline of drugs and efforts made by scientific community.

Identification, antibiotic resistance, and virulence profiling of Aeromonas and Pseudomonas species from wastewater and surface water

Aquatic environments are hotspots for the spread of antibiotic-resistant bacteria and genes due to pollution caused mainly by anthropogenic activities. The aim of this study was to evaluate the impact of wastewater effluents, informal settlements, hospital, and veterinary clinic discharges on the occurrence, antibiotic resistance profile and virulence signatures of Aeromonas spp. and Pseudomonas spp. isolated from surface water and wastewater. High counts of Aeromonas spp. (2.5 (± 0.8) - 3.3 (± 0.4) log₁₀ CFU mL^-1) and Pseudomonas spp. (0.6 (± 1.0) - 1.8 (± 1.0) log₁₀ CFU mL^-1) were obtained. Polymerase chain reaction (PCR) and MALDI-TOF characterization identified four species of Aeromonas and five of Pseudomonas. The isolates displayed resistance to 3 or more antibiotics (71% of Aeromonas and 94% of Pseudomonas). Aeromonas spp. showed significant association with the antibiotic meropenem (χ² = 3.993, P < 0.05). The virulence gene aer in Aeromonas was found to be positively associated with the antibiotic resistance gene blaOXA (χ² = 6.657, P < 0.05) and the antibiotic ceftazidime (χ² = 7.537, P < 0.05). Aeromonas recovered from both wastewater and surface water displayed high resistance to ampicillin and had higher multiple antibiotic resistance (MAR) indices close to the hospital. Pseudomonas isolates on the other hand exhibited low resistance to carbapenems but very high resistance to the third-generation cephalosporins and cefixime. The results showed that some of the Pseudomonas spp. and Aeromonas spp. isolates were extended-spectrum β-lactamase producing bacteria. In conclusion, the strong association between virulence genes and antibiotic resistance in the isolates shows the potential health risk to communities through direct and indirect exposure to the water.

Emergence of Nosocomial Pneumonia Caused by Colistin-Resistant Escherichia coli in Patients Admitted to Chest Intensive Care Unit

(1) Background: Colistin is a last-resort antibiotic used in treating multidrug-resistant Gram-negative infections. The growing emergence of colistin resistance in Escherichia coli (E. coli) represents a serious health threat, particularly to intensive care unit (ICU) patients. (2) Methods: In this work, we investigated the emergence of colistin resistance in 140 nosocomial E. coli isolated from patients with pneumonia and admitted to the chest ICU over 36 months. Virulence and resistance-related genes and E. coli pathotypes in colistin-resistant and colistin-sensitive isolates were determined. (3) Results: Colistin resistance was observed in 21/140 (15%) of the nosocomial E. coli isolates. The MIC₅₀ of the resistant strains was 4 mg/L, while MIC₉₀ was 16 mg/L. Colistin-resistant isolates were also co-resistant to amoxicillin, amoxicillin/clavulanic, aztreonam, ciprofloxacin, and chloramphenicol. The mechanism of colistin resistance was represented by the presence of mcr-1 in all resistant strains. Respectively, 42.9% and 36.1% of colistin-resistant and colistin-sensitive groups were extended-spectrum β-lactamase (ESBL) producers, while 23.8% and 21% were metallo β-lactamase (MBL) producers. bla_TEM-type was the most frequently detected ESBL gene, while bla_IMP-type was the most common MBL in both groups. Importantly, most resistant strains showed a significantly high prevalence of astA (76.2%), aggR (76.2%), and pic (52.4%) virulence-related genes. Enteroaggregative E. coli (76%) was the most frequently detected genotype among the colistin-resistant strains. (4) Conclusion: The high colistin resistance rate observed in E. coli strains isolated from patients with nosocomial pneumonia in our university hospital is worrisome. These isolates carry different drug resistance and virulence-related genes. Our results indicate the need for careful monitoring of colistin resistance in our university hospital. Furthermore, infection control policies restricting the unnecessary use of extended-spectrum cephalosporins and carbapenems are necessary.

Mobile Carbapenemase Genes in Pseudomonas aeruginosa

Carbapenem-resistant Pseudomonas aeruginosa is one of the major concerns in clinical settings impelling a great challenge to antimicrobial therapy for patients with infections caused by the pathogen. While membrane permeability, together with derepression of the intrinsic beta-lactamase gene, is the global prevailing mechanism of carbapenem resistance in P. aeruginosa, the acquired genes for carbapenemases need special attention because horizontal gene transfer through mobile genetic elements, such as integrons, transposons, plasmids, and integrative and conjugative elements, could accelerate the dissemination of the carbapenem-resistant P. aeruginosa. This review aimed to illustrate epidemiologically the carbapenem resistance in P. aeruginosa, including the resistance rates worldwide and the carbapenemase-encoding genes along with the mobile genetic elements responsible for the horizontal dissemination of the drug resistance determinants. Moreover, the modular mobile elements including the carbapenemase-encoding gene, also known as the P. aeruginosa resistance islands, are scrutinized mostly for their structures.

Cephalosporins Interfere With Quorum Sensing and Improve the Ability of Caenorhabditis elegans to Survive Pseudomonas aeruginosa Infection

Pseudomonas aeruginosa utilizes the quorum sensing (QS) system to strategically coordinate virulence and biofilm formation. Targeting QS pathways may be a potential anti-infective approach to treat P. aeruginosa infections. In the present study, we define cephalosporins' anti-QS activity using Chromobacterium violaceum CV026 for screening and QS-regulated mutants of P. aeruginosa for validation. We quantified the effects of three cephalosporins, cefepime, ceftazidime, and ceftriaxone, on (1) pyocyanin production using spectrophotometric assay, (2) bacterial motility using agar plate assay, and (3) biofilm formation using scanning electron microscopy. We also studied isogenic QS mutant strains of PAO1 (ΔlasR,ΔrhlR,ΔpqsA, and ΔpqsR) to compare and distinguish QS-mediated effects on the motility phenotypes and bacterial growth with and without sub-MIC concentrations of antibiotics. Results showed that cephalosporins have anti-QS activity and reduce bacterial motility, pyocyanin production, and biofilm formation for CV026 and PAO1. Also, sub-MICs of cefepime increased aminoglycosides' antimicrobial activity against P. aeruginosa PAO1, suggesting the advantage of combined anti-QS and antibacterial treatment. To correlate experimentally observed anti-QS effects with the interactions between cephalosporins and QS receptors, we performed molecular docking with ligand binding sites of quorum sensing receptors using Autodock Vina. Molecular docking predicted cephalosporins' binding affinities to the ligand-binding pocket of QS receptors (CviR, LasR, and PqsR). To validate our results using an infection model, we quantified the survival rate of Caenorhabditis elegans following P. aeruginosa PAO1 challenge at concentrations less than the minimum inhibitory concentration (MIC) of antibiotics. C. elegans infected with PAO1 without antibiotics showed 0% survivability after 72 h. In contrast, PAO1-infected C. elegans showed 65 ± 5%, 58 ± 4%, and 49 ± 8% survivability after treatment with cefepime, ceftazidime, and ceftriaxone, respectively. We determined the survival rates of C. elegans infected by QS mutant strains ΔlasR (32 ± 11%), ΔrhlR (27 ± 8%), ΔpqsA (27 ± 10%), and ΔpqsR (37 ± 6%), which suggest essential role of QS system in virulence. In summary, cephalosporins at sub-MIC concentrations show anti-QS activity and enhance the antibacterial efficacy of aminoglycosides, a different class of antibiotics. Thus, cephalosporins at sub-MIC concentrations in combination with other antibiotics are potential candidates for developing therapies to combat infections caused by P. aeruginosa.

Emergent Pneumonia in Children

In recent decades there have been multiple pathogens, viruses and bacteria, which have emerged as causal agents of pneumonia affecting adults, albeit less frequently, to children. For the purposes of this article we have classified emerging pathogens as follows: True emerging, to pathogens identified for the very first time affecting human population (SARS-CoV-1, SARS-CoV-2, MERS-CoV, avian influenza, and hantavirus); Re-emerging, to known pathogens which circulation was controlled once, but they have reappeared (measles, tuberculosis, antimicrobial resistant bacteria such as CA-MRSA, Mycoplasma pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and new serotypes of post-vaccine pneumococcal); and finally, those that we have called old known with new presentations, including common pathogens that, in particular condition, have changed their form of presentation (rhinovirus, and non-SARS coronavirus). We will review for each of them their epidemiology, forms of presentation, therapy, and prognosis in children compared to the adult with the aim of being able to recognize them to establish appropriate therapy, prognostics, and effective control measures.

Potentiation of β-lactam antibiotics and β-lactam/β-lactamase inhibitor combinations against MDR and XDR Pseudomonas aeruginosa using non-ribosomal tobramycin-cyclam conjugates

OBJECTIVES

To develop a multifunctional adjuvant molecule that can rescue β-lactam antibiotics and β-lactam/β-lactamase inhibitor combinations from resistance in carbapenem-resistant Pseudomonas aeruginosa clinical isolates.

METHODS

Preparation of adjuvant was guided by structure-activity relationships, following standard protocols. Susceptibility and chequerboard studies were assessed using serial 2-fold dilution assays. Toxicity was evaluated against porcine erythrocytes, human embryonic kidney (HEK293) cells and liver carcinoma (HepG2) cells via MTS assay. Preliminary in vivo efficacy was evaluated using a Galleria mellonella infection model.

RESULTS

Conjugation of tobramycin and cyclam abrogates the ribosomal effects of tobramycin but confers a potent adjuvant property that restores full antibiotic activity of meropenem and aztreonam against carbapenem-resistant P. aeruginosa. Therapeutic levels of susceptibility, as determined by CLSI susceptibility breakpoints, were attained in several MDR clinical isolates, and time-kill assays revealed a synergistic dose-dependent pharmacodynamic relationship. A triple combination of the adjuvant with ceftazidime/avibactam (approved), aztreonam/avibactam (Phase III) and meropenem/avibactam enhances the efficacies of β-lactam/β-lactamase inhibitors against recalcitrant strains, suggesting rapid access of the combination to their periplasmic targets. The newly developed adjuvants, and their combinations, were non-haemolytic and non-cytotoxic, and preliminary in vivo evaluation in G. mellonella suggests therapeutic potential for the double and triple combinations.

CONCLUSIONS

Non-ribosomal tobramycin-cyclam conjugate mitigates the effect of OprD/OprF porin loss in P. aeruginosa and potentiates β-lactam/β-lactamase inhibitors against carbapenem-resistant clinical isolates, highlighting the complexity of resistance to β-lactam antibiotics. Our strategy presents an avenue to further preserve the therapeutic utility of β-lactam antibiotics.

Impact of the immune response modification by lysophosphatidylcholine in the efficacy of antibiotic therapy of experimental models of peritoneal sepsis and pneumonia by Pseudomonas aeruginosa: LPC therapeutic effect in combined therapy

INTRODUCTION

Immune response stimulation may be an adjuvant to antimicrobial treatment. Here, we evaluated the impact of immune response modification by lysophosphatidylcholine (LPC), combined with imipenem or ceftazidime, in murine models of peritoneal sepsis (PS) and pneumonia induced by Pseudomonas aeruginosa.

METHODS

The imipenem and ceftazidime-susceptible strain (Pa39) and imipenem and ceftazidime-resistant strain (Pa238) were used. Ceftazidime pharmacokinetic and pharmacodynamic parameters were determined. The therapeutic efficacy and TNF-α and IL-10 levels were determined in murine models of PS and pneumonia induced by Pa39 and Pa238 and treated with LPC, imipenem or ceftazidime, alone or in combination.

RESULTS

In the PS model, LPC+ceftazidime reduced spleen and lung Pa238 concentrations (-3.45 and -3.56log10CFU/g; P<0.05) to a greater extent than ceftazidime monotherapy, while LPC+imipenem maintained the imipenem efficacy (-1.66 and -1.45log10CFU/g; P>0.05). In the pneumonia model, LPC+ceftazidime or LPC+imipenem reduced the lung Pa238 concentrations (-2.37log10CFU/g, P=0.1, or -1.35log10CFU/g, P=0.75). For Pa39, no statistically significant difference was observed in the PS and pneumonia models between combined therapy and monotherapy. Moreover, LPC+imipenem and LPC+ceftazidime significantly decreased and increased the TNF-α and IL-10 levels, respectively, in comparison with the untreated controls and monotherapies.

CONCLUSIONS

These results demonstrate the impact of immune response modification by LPC plus antibiotics on the prognosis of infections induced by ceftazidime-resistant P. aeruginosa.

Ceftazidime-Avibactam in Combination With Fosfomycin: A Novel Therapeutic Strategy Against Multidrug-Resistant Pseudomonas aeruginosa

Previously, by targeting penicillin-binding protein 3, Pseudomonas-derived cephalosporinase (PDC), and MurA with ceftazidime-avibactam-fosfomycin, antimicrobial susceptibility was restored among multidrug-resistant (MDR) Pseudomonas aeruginosa. Herein, ceftazidime-avibactam-fosfomycin combination therapy against MDR P. aeruginosa clinical isolate CL232 was further evaluated. Checkerboard susceptibility analysis revealed synergy between ceftazidime-avibactam and fosfomycin. Accordingly, the resistance elements present and expressed in P. aeruginosa were analyzed using whole-genome sequencing and transcriptome profiling. Mutations in genes that are known to contribute to β-lactam resistance were identified. Moreover, expression of blaPDC, the mexAB-oprM efflux pump, and murA were upregulated. When fosfomycin was administered alone, the frequency of mutations conferring resistance was high; however, coadministration of fosfomycin with ceftazidime-avibactam yielded a lower frequency of resistance mutations. In a murine infection model using a high bacterial burden, ceftazidime-avibactam-fosfomycin significantly reduced the P. aeruginosa colony-forming units (CFUs), by approximately 2 and 5 logs, compared with stasis and in the vehicle-treated control, respectively. Administration of ceftazidime-avibactam and fosfomycin separately significantly increased CFUs, by approximately 3 logs and 1 log, respectively, compared with the number at stasis, and only reduced CFUs by approximately 1 log and 2 logs, respectively, compared with the number in the vehicle-treated control. Thus, the combination of ceftazidime-avibactam-fosfomycin was superior to either drug alone. By employing a "mechanism-based approach" to combination chemotherapy, we show that ceftazidime-avibactam-fosfomycin has the potential to offer infected patients with high bacterial burdens a therapeutic hope against infection with MDR P. aeruginosa that lack metallo-β-lactamases.

Emerging Treatment Options for Infections by Multidrug-Resistant Gram-Positive Microorganisms

Antimicrobial agents are currently the mainstay of treatment for bacterial infections worldwide. However, due to the increased use of antimicrobials in both human and animal medicine, pathogens have now evolved to possess high levels of multi-drug resistance, leading to the persistence and spread of difficult-to-treat infections. Several current antibacterial agents active against Gram-positive bacteria will be rendered useless in the face of increasing resistance rates. There are several emerging antibiotics under development, some of which have been shown to be more effective with an improved safety profile than current treatment regimens against Gram-positive bacteria. We will extensively discuss these antibiotics under clinical development (phase I-III clinical trials) to combat Gram-positive bacteria, such as Staphylococcus aureus, Enterococcus faecium and Streptococcus pneumoniae. We will delve into the mechanism of actions, microbiological spectrum, and, where available, the pharmacokinetics, safety profile, and efficacy of these drugs, aiming to provide a comprehensive review to the involved stakeholders.

Human umbilical-cord mesenchymal stem cells inhibit bacterial growth and alleviate antibiotic resistance in neonatal imipenem-resistant Pseudomonas aeruginosa infection

Human umbilical-cord mesenchymal stem cells (hUCMSCs) are a safe and convenient source of MSCs and have shown beneficial effects in neonatal infection and sepsis animal models. However, the factors leading to improved outcomes are still unclear. The aim of this study was to investigate the antibacterial effect and regulation of antimicrobial resistance of hUCMSCs. We separated imipenem-resistant Pseudomonas aeruginosa (PA) from neonates and incubated it with hUCMSCs as well as their culture medium. Assessment of direct inhibition of bacterial growth was done by counting CFUs. The concentration of antibacterial peptides in the culture medium of hUCMSCs was measured. Standard PA was inoculated with a sub-inhibitory concentration of imipenem with and without hUCMSC conditioned medium and antimicrobial peptides. The sensitivity to imipenem was detected until PA showed resistance to imipenem. Outer membrane protein (OprD2) mRNA expression in PA before and after the induction of imipenem resistance was analysed. We found that HUCMSCs possessed direct antimicrobial properties against bacteria and could alleviate antibiotic resistance via reserving OprD2 expression in PA.

The antibacterial properties of phenolic isomers, carvacrol and thymol

Most of the antibacterial activities of essential oils from the Lamiaceae herbaceous plant family thyme and oregano are attributed to their bioactive isomeric monoterpenoid constituents, carvacrol and thymol. Commercially available antibiotics of thymol or carvacrol have not yet been developed but health products have incorporated thymol into their formulations for their antimicrobial properties. Carvacrol and thymol are generally considered safe for consumption and they have been used in dental applications, approved as food flavorings and have been considered as antibacterial additives in food and feed. Many studies have demonstrated that carvacrol and thymol are potent antibacterial agents against both Gram-positive and Gram-negative bacteria. The most frequently reported mechanism of antibacterial action of both isomers involves the disruption of bacterial membrane leading to bacterial lysis and leakage of intracellular contents resulting in death. Other proposed mechanisms of antibacterial action include the inhibition of efflux pumps, prevention in the formation and disruption of preformed biofilms, inhibition of bacterial motility, and inhibition of membrane ATPases. In addition, both isomers have been found to act additively or synergistically with conventional antibiotics important in overcoming the problem of bacteria resistance in food and disease.

Quinolone antibiotics

The quinolone antibiotics arose in the early 1960s, with the first examples possessing a narrow-spectrum of activity with unfavorable pharmacokinetic properties. Over time, the development of new quinolone antibiotics has led to improved analogues with an expanded spectrum and high efficacy. Nowadays, quinolones are widely used for treating a variety of infections. Quinolones are broad-spectrum antibiotics that are active against both Gram-positive and Gram-negative bacteria, including mycobacteria, and anaerobes. They exert their actions by inhibiting bacterial nucleic acid synthesis through disrupting the enzymes topoisomerase IV and DNA gyrase, and by causing breakage of bacterial chromosomes. However, bacteria have acquired resistance to quinolones, similar to other antibacterial agents, due to the overuse of these drugs. Mechanisms contributing to quinolone resistance are mediated by chromosomal mutations and/or plasmid gene uptake that alter the topoisomerase targets, modify the quinolone, and/or reduce drug accumulation by either decreased uptake or increased efflux. This review discusses the development of this class of antibiotics in terms of potency, pharmacokinetics and toxicity, along with the resistance mechanisms which reduce the quinolones' activity against pathogens. Potential strategies for future generations of quinolone antibiotics with enhanced activity against resistant strains are suggested.

Isolation of Phage Lysins That Effectively Kill Pseudomonas aeruginosa in Mouse Models of Lung and Skin Infection

Multidrug resistance (MDR) is rapidly increasing in prevalence among isolates of the opportunistic pathogen Pseudomonas aeruginosa, leaving few treatment options. Phage lysins are cell wall hydrolases that have a demonstrated therapeutic potential against Gram-positive pathogens; however, the outer membrane of Gram-negative bacteria prevents most lysins from reaching the peptidoglycan, making them less effective as therapeutics. Nevertheless, a few lysins from Gram-negative bacterial phage can penetrate the bacterial outer membrane with the aid of an amphipathic tail found in the molecule's termini. In this work, we took a phylogenetic approach to systematically identify those lysins from P. aeruginosa phage that would be most effective therapeutically. We isolated and performed preliminary characterization of 16 lysins and chose 2 lysins, PlyPa03 and PlyPa91, which exhibited >5-log killing activity against P. aeruginosa and other Gram-negative pathogens (particularly Klebsiella and Enterobacter). These lysins showed rapid killing kinetics and were active in the presence of high concentrations of salt and urea and under pH conditions ranging from 5.0 to 10.0. Activity was not inhibited in the presence of the pulmonary surfactant beractant (Survanta). While neither enzyme was active in 100% human serum, PlyPa91 retained activity in low serum concentrations. The lysins were effective in the treatment of a P. aeruginosa skin infection in a mouse model, and PlyPa91 protected mice in a lung infection model, making these lysins potential drug candidates for Gram-negative bacterial infections of the skin or respiratory mucosa.

Antibacterial activity of colistin is resurrected by Stephania suberosa Forman extract against colistin-resistant Enterobacter cloacae

To resurrect antibacterial efficacy of colistin (CLT), ceftazidime (CAZ) and cefotaxime (CTX), Stephania suberosa extract (SSE) was combined with these particular antibiotics to combat CLT-resistant Enterobacter cloacae (CREC) isolates. Disc diffusion assay showed that SSE inhibited E. cloacae strains with the dose-dependent manner. Minimum inhibitory concentrations (MICs) of SSE against all tested strains were 2000 µg ml^-1 . CREC DMST 37480 and 19719 were found to be resistant to CLT with MICs of 64 and 4 µg ml^-1 , respectively, and also resistant to CAZ. These strains showed a minimum bactericidal concentration (MBC) of SSE at 8000 µg ml^-1 . Checkerboard assay showed that CLT resistance was synergistically reversed by SSE against CREC DMST 37480 and 19719 with a fractional inhibitory concentration (FIC) indices of 0·253 and 0·265, respectively. Time-killing assay confirmed synergistic interaction by a decline in the viability combined treated group compared to an individual. CREC DMST 19719 was found to produce AmpC β-lactamase. SSE cannot resurrect CAZ in an AmpC producer. The scanning electron microscopy showed that SSE and CLT induced cell damages at different sites. GC-MS analysis identified 25 known Phyto-compounds. SSE and CLT combination could be further developed as a novel agent for treating multidrug-resistant CREC. SIGNIFICANCE AND IMPACT OF THE STUDY: Resistance to colistin (CLT), an alternative agent for treating multiple drug-resistant Enterobacter cloacae, is among the most serious, life-threatening issues. This study utilizes Stephania suberosa extract (SSE) to revive the antibacterial activity of colistin that has lost its antibacterial effectiveness in inhibiting E. cloacae. The findings support the development of the combined agent between SSE and colistin to conquer colistin-resistant E. cloacae.

In a murine model of acute lung infection, airway administration of a therapeutic antibody confers greater protection than parenteral administration

Due to growing antibiotic resistance, pneumonia caused by Pseudomonas aeruginosa is a major threat to human health and is driving the development of novel anti-infectious agents. Preventively or curatively administered pathogen-specific therapeutic antibodies (Abs) have several advantages, including a low level of toxicity and a unique pharmacological profile. At present, most Abs against respiratory infections are administered parenterally; this may not be optimal for therapeutics that have to reach the lungs to be effective. Although the airways constitute a logical delivery route for biologics designed to treat respiratory diseases, there are few scientific data on the advantages or disadvantages of this route in the context of pneumonia treatment. The objective of the present study was to evaluate the efficacy and fate of an anti-P. aeruginosa Ab targeting pcrV (mAb166) as a function of the administration route during pneumonia. The airway-administered mAb166 displayed a favorable pharmacokinetic profile during the acute phase of the infection, and was associated with greater protection (relative to other delivery routes) of infected animals. Airway administration was associated with lower levels of lung inflammation, greater bacterial clearance, and recruitment of neutrophils in the airways. In conclusion, the present study is the first to have compared the pharmacokinetics and efficacy of an anti-infectious Ab administered by different routes in an animal model of pneumonia. Our findings suggest that local delivery to the airways is associated with a more potent anti-bacterial response (relative to parenteral administration), and thus open up new perspectives for the prevention and treatment of pneumonia with Abs.

Antibiotic resistance in Pseudomonas aeruginosa: mechanisms and alternative therapeutic strategies

Pseudomonas aeruginosa is an opportunistic pathogen that is a leading cause of morbidity and mortality in cystic fibrosis patients and immunocompromised individuals. Eradication of P. aeruginosa has become increasingly difficult due to its remarkable capacity to resist antibiotics. Strains of Pseudomonas aeruginosa are known to utilize their high levels of intrinsic and acquired resistance mechanisms to counter most antibiotics. In addition, adaptive antibiotic resistance of P. aeruginosa is a recently characterized mechanism, which includes biofilm-mediated resistance and formation of multidrug-tolerant persister cells, and is responsible for recalcitrance and relapse of infections. The discovery and development of alternative therapeutic strategies that present novel avenues against P. aeruginosa infections are increasingly demanded and gaining more and more attention. Although mostly at the preclinical stages, many recent studies have reported several innovative therapeutic technologies that have demonstrated pronounced effectiveness in fighting against drug-resistant P. aeruginosa strains. This review highlights the mechanisms of antibiotic resistance in P. aeruginosa and discusses the current state of some novel therapeutic approaches for treatment of P. aeruginosa infections that can be further explored in clinical practice.

Bioresponsive Nanoparticles Targeted to Infectious Microenvironments for Sepsis Management

Sepsis is a life-threatening disease resulted from a dysregulated host immune response to bacterial infections, continuing to cause high morbidity and mortality worldwide. Despite discoveries of many potential therapeutic targets, effective treatments of sepsis are lacking. Here, a strategy is reported to target infectious microenvironments (IMEs) via bioresponsive nanoparticles that simultaneously eliminate bacteria and alleviate the host inflammation response, thus managing sepsis in mice. The nanoparticle is made of copolymers sensitive to pH and bacterial enzymes to self-assemble into a micelle loaded with both an antibiotic (ciprofloxacin) and an anti-inflammatory agent ((2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide). In addition, the nanoparticle is conjugated with intercellular adhesion molecule-1 antibodies to target IMEs. Nanoparticle targeting to IMEs and local cues as triggers to deliver therapeutics in on-demand manners is demonstrated using an acute lung bacterial infection mouse model. In the sepsis mouse model induced by peritonitis at a lethal dose of bacterial invasion, it is shown that concurrently targeting pathogens and excessive inflammation pathways is valuable to manage the sepsis. The study illustrates not only the development of a new delivery system but also the mechanism-based therapy of nanomedicine for infectious diseases.

Immunization with Pseudomonas aeruginosa outer membrane vesicles stimulates protective immunity in mice

Pseudomonas aeruginosa is an opportunistic pathogen responsible for a wide range of severe nosocomial and community acquired infections, these infections are major health problems for cystic fibrosis patients and immune-compromised individuals. The emergence of multidrug-resistant isolates highlights the need to develop alternative strategies for treatment of P. aeruginosa infections. Outer membrane vesicles (OMVs) are spherical nanometer-sized proteolipids that are secreted from numerous of pathogenic Gram-negative bacteria, and a number of studies have confirmed the protective efficacy for use of OMVs as candidate vaccines. In this study, OMVs from P. aeruginosa (PA_OMVs) were isolated, formulated with aluminum phosphate adjuvant and used as a vaccine in a mouse model of acute lung infection. The results confirmed that active immunization with PA_OMVs was able to reduce bacterial colonization, cytokine secretion and tissue damage in the lung tissue, thus protecting mice from lethal challenge of P. aeruginosa. Cytokines assay validated that immunization with PA_OMVs was efficient to induce a mixed cellular immune response in mice. Further, high level of specific antibodies was detected in mice immunized with PA_OMVs, and results from opsonophagocytic killing assay and passive immunization suggested that humoral immune response may be critical for PA_OMVs mediated protection. These findings demonstrated that PA_OMVs may be served as a novel candidate vaccine for the prevention of P. aeruginosa infection.

Lactobacillus salivarius reverse antibiotic-induced lung defense impairment in a ventilator model

Background

Widespread use of antibiotics in the intensive care unit is a potential cause of the emergence of hospital-acquired pneumonia. This study determined whether Lactobacillus salivarius feeding could reverse antibiotic-induced lung defense impairment in a ventilator model.

Methods

C57BL/6 wild-type (WT) mice received mechanical ventilation for 3 h after intramuscular antibiotic treatment for 6 days. Treatment with dead Lactobacillus salivarius and fructo-oligosaccharides (FOS) feeding were used to stimulate antibacterial protein expression in the intestine. Reactive oxygen species (ROS) in the intestinal mucosa was detected using 2ʹ7ʹ-dichlorofluorescein diacetate. The peroxynitrite production of alveolar macrophages (AMs) was measured using dihydrorhodamine 123 oxidation assay. N-acetylcysteine (NAC), an ROS scavenger, was orally administered to mice receiving antibiotics with FOS feeding.

Results

Antibiotic treatment decreased Pseudomonas aeruginosa (PA) phagocytic activity and activity of AMs and protein expression of regenerating islet-derived protein 3β (Reg3β) as well as Toll-like receptor 4 (TLR4) in the intestinal mucosa in the ventilator model. Antibiotic treatment also decreased ROS production in the intestinal mucosa, peroxynitrite production of AMs, and RELMβ expression as well as NF-κB DNA binding activity of the intestinal mucosa in WT mice but not in MyD88^−/− mice. Treatment with dead L. salivarius or FOS feeding increased ROS production, bacterial killing activity, and protein expression of Reg3β as well as TLR4 in the intestinal mucosa and reversed the inhibitory effects of antibiotics on PA phagocytic activity of AMs.

Conclusion

Taken together with the finding that ablation of FOS-induced intestinal ROS using NAC decreased peroxynitrite production as well as PA phagocytic activity of AMs and protein expression of CRP-ductin, IL-17, Reg3β, and RELMβ in the intestinal mucosa, we conclude that commensal microflora plays a key role in stimulating lung immunity. Intestinal ROS plays a role as a predictive indicator and modulator of pulmonary defense mechanisms. Antibiotic treatment reduces lung defense against PA infection through the decrease in intestinal Reg3β and TLR4 expression. Treatment with dead L. salivarius or FOS feeding reverses the antibiotic-induced lung defense impairment through the intestinal ROS/MyD88 pathways.

Coexistence of metallo-beta-lactamase-encoding genes in Pseudomonas aeruginosa

BACKGROUND & OBJECTIVES

The emergence and rapid spread of carbapenem resistance mediated by metallo-beta-lactamase (MBL) in Pseudomonas aeruginosa is of major concern due to limited therapeutic options. This study was aimed at detecting the presence of MBL and its association with integrons in imipenem-resistant P. aeruginosa isolates and to determine their genetic relatedness.

METHODS

A total of 213 P. aeruginosa isolates were collected from two tertiary care centres and tested against anti-pseudomonal antibiotics by antimicrobial susceptibility testing, followed by the detection of MBL production by combined disk method. Minimum inhibitory concentration (MIC) of meropenem was determined by E-test. Multiplex polymerase chain reaction (PCR) was performed for the detection of blaSPM, blaIMP, blaVIM, blaNDM, blaGIM and blaSIM. PCR was carried out to characterize the variable region of class 1 integron. Transcongujation assay was carried out for the confirmation of plasmid-mediated resistance. Enterobacterial repetitive intergenic consensus sequence (ERIC)-PCR was performed for determining the genetic relatedness among P. aeruginosa isolates.

RESULTS

Of the 213 P. aeruginosa isolates, 22 (10%) were found to be carbapenem resistant and these were from pus 18 (82%), urine 2 (9%), sputum 1 (5%) and tracheal wash 1 (5%). Among 22 isolates, 18 (81.8%) were found to be MBL producers by phenotypic method and MIC range of meropenem was 8 to >32 μg/ml. PCR amplification showed that 20 (91%) isolates carried any one of the MBL genes tested: blaVIM and blaNDM in seven (32%) and six (27%) isolates, respectively; blaVIM and blaNDMin three (14%); blaIMP and blaNDM in two (9%); blaVIM and blaIMP in one (5%) isolate. The blaVIM, blaIMP and blaNDM were found to co-exist in one isolate. None of the isolates were positive for blaSPM, blaSIM and blaGIM. All 22 isolates carried class I integron. Of the 20 MBL-positive isolates, transconjugants were obtained for 15 isolates. ERIC-PCR analysis showed all isolates to be clonally independent.

INTERPRETATION & CONCLUSIONS

Our results showed 10.3 per cent of carbapenem resistance among P. aeruginosa isolates, and the coexistence of MBL-encoding genes among P. aeruginosa mediated by class I integron.

Antibiotic combination efficacy (ACE) networks for a Pseudomonas aeruginosa model

The spread of antibiotic resistance is always a consequence of evolutionary processes. The consideration of evolution is thus key to the development of sustainable therapy. Two main factors were recently proposed to enhance long-term effectiveness of drug combinations: evolved collateral sensitivities between the drugs in a pair and antagonistic drug interactions. We systematically assessed these factors by performing over 1,600 evolution experiments with the opportunistic nosocomial pathogen Pseudomonas aeruginosa in single- and multidrug environments. Based on the growth dynamics during these experiments, we reconstructed antibiotic combination efficacy (ACE) networks as a new tool for characterizing the ability of the tested drug combinations to constrain bacterial survival as well as drug resistance evolution across time. Subsequent statistical analysis of the influence of the factors on ACE network characteristics revealed that (i) synergistic drug interactions increased the likelihood of bacterial population extinction-irrespective of whether combinations were compared at the same level of inhibition or not-while (ii) the potential for evolved collateral sensitivities between 2 drugs accounted for a reduction in bacterial adaptation rates. In sum, our systematic experimental analysis allowed us to pinpoint 2 complementary determinants of combination efficacy and to identify specific drug pairs with high ACE scores. Our findings can guide attempts to further improve the sustainability of antibiotic therapy by simultaneously reducing pathogen load and resistance evolution.

Mutations in the gyrA, parC, and mexR genes provide functional insights into the fluoroquinolone-resistant Pseudomonas aeruginosa isolated in Vietnam

Introduction

Pseudomonas aeruginosa has many mechanisms of resistance to fluoroquinolones. The main mechanism is to change the effect of two enzymes that open the DNA helix - the enzyme DNA gyrase (gyrA) and the topoisomerase IV (parC). In addition, mutations that render the MexAB-oprM pump (mexR) dysfunctional, leading to its overexpression, also enhance resistance to fluoroquinolones. In this study, we aim to detect point mutations of gyrA, parC, and mexR genes that are predicted to be associated with fluoroquinolone resistance in 141 fluoroquinolone-resistant clinical isolates of P. aeruginosa isolated in Vietnam during 2013-2016.

Methods

We tested minimum inhibitory concentrations (MICs) of fluoroquinolone antibiotics in 141 clinical isolates of P. aeruginosa using the VITEK 2 Compact System, followed by PCR assay, to detect and clone the fluoroquinolone resistance-determining region (FRDR) of gyrA, parC, and mexR. Point mutations were analyzed through Sanger sequencing, and the correlation between genetic mutations and phenotypic resistance of 141 clinical isolates was undertaken.

Results

Fluoroquinolone-resistant substitution mutations such as Ile for Thr83 and Met for Thr133 in gyrA, Leu for Ser87 in parC, and Val for Glu126 in the repressor of mexR were mainly detected. Comparative analytical data indicated that amino acid alterations within the gyrA and parC genes are highly associated with resistance to ciprofloxacin (CIP) and levofloxacin (LEV) in the isolates, whereas alterations in the efflux regulatory mexR gene are not highly consistent with resistance in these isolates. Moreover, fluoroquinolone-resistant clinical isolates of P. aeruginosa were mainly isolated from pus and sputum specimens.

Conclusion

In clinical isolates of P. aeruginosa, a high correlation was observed between MICs of CIP and LEV and alterations in gyrA and parC genes. However, mutations occurring in mexR did not highly correlate with the antibiotic resistance of the bacterium.

Epidemiology and risk factors of extensively drug-resistant Pseudomonas aeruginosa infections

BACKGROUND

The incidence of nosocomial infections from extensively drug-resistant Pseudomonas aeruginosa (XDR-PA) has been increasing worldwide. We investigated the prevalence and factors associated with XDR-PA infections, including the factors that predict mortality.

METHODS

We retrospectively studied a cohort of adult, hospitalized patients with P. aeruginosa (PA) infections between April and December 2014.

RESULTS

Of the 255 patients with PA infections, 56 (22%) were due to XDR-PA, 32 (12.5%) to multidrug resistant Pseudomonas aeruginosa (MDR-PA), and 167 (65.5%) to non-MDR PA. Receiving total parenteral nutrition (adjusted OR [aOR] 6.21; 95% CI 1.05-36.70), prior carbapenem use (aOR 4.88; 95% CI 2.36-10.08), and prior fluoroquinolone use (aOR 3.38; 95% CI 1.44-7.97) were independently associated with the XDR-PA infections. All XDR-PA remained susceptible to colistin. Factors associated with mortality attributable to the infections were the presence of sepsis/septic shock (aOR 11.60; 95% CI 4.66-28.82), admission to a medical department (aOR 4.67; 95% CI 1.81-12.06), receiving a central venous catheter (aOR 3.78; 95% CI 1.50-9.57), and XDR-PA infection (aOR 2.73; 95% CI 1.05-7.08).

CONCLUSION

The prevalence of XDR-PA infections represented almost a quarter of Pseudomonas aeruginosa hospital-acquired infections and rendered a higher mortality. The prompt administration of an appropriate empirical antibiotic should be considered when an XDR-PA infection is suspected.

Haplotype analysis of the germacrene A synthase gene and association with cynaropicrin content and biological activities in Cynara cardunculus

Cynara cardunculus: L. represents a natural source of terpenic compounds, with the predominant molecule being cynaropicrin. Cynaropicrin is gaining interest since it has been correlated to anti-hyperlipidaemia, antispasmodic and cytotoxicity activity against leukocyte cancer cells. The objective of this work was to screen a collection of C. cardunculus, from different origins, for new allelic variants in germacrene A synthase (GAS) gene involved in the cynaropicrin biosynthesis and correlate them with improved cynaropicrin content and biological activities. Using high-resolution melting, nine haplotypes were identified. The putative impact of the identified allelic variants in GAS protein was evaluated by bioinformatic tools and polymorphisms that putatively lead to protein conformational changes were described. Additionally, cynaropicrin and main pentacyclic triterpenes contents, and antithrombin, antimicrobial and antiproliferative activities were also determined in C. cardunculus leaf lipophilic-derived extracts. In this work we identified allelic variants with putative impact on GAS protein, which are significantly associated with cynaropicrin content and antiproliferative activity. The results obtained suggest that the identified polymorphisms should be explored as putative genetic markers correlated with biological properties in Cynara cardunculus.