Bacterial Multidrug Resistance Research Articles

Design and synthesis of benzochromene derivatives as AcrB inhibitors for the reversal of bacterial multidrug resistance

A series of novel benzo[h]chromene compounds were designed, synthesized and evaluated for their biological activity as AcrB inhibitors. The compounds were assessed for their ability to potentiate the effect of antibiotics. Compounds with antibiotic-potentiating effects were then evaluated for inhibition of Nile Red efflux, and for off-target effects including activity on the outer and inner bacterial membranes and toxicity. Six compounds were identified to reduce the MIC values of at least one of the tested antibiotics by at least 4-fold, and further reduced the MICs in the presence of a membrane permeabilizer. The identified compounds were also able to inhibit Nile Red efflux at concentrations between 50 μM and 200 μM. The compounds did not disrupt the bacterial outer membrane nor display toxicity in a nematode model (Caenorhabditis elegans). The 4-methoxyphenoxy)propoxy derivative compound G6 possessed the most potent antibacterial potentiation with erythromycin by 8-fold even without the presence of a membrane permeabilizer. Furthermore, H6, G6, G10 and G11 completely abolished the Nile Red efflux at a concentration of 50 μM. The 3,4-dihydro-2H-benzo[h]chromen-5-yl)(morpholino)methanone core appears to be a promising chemical skeleton to be further studied in the discovery of more putative AcrB inhibitors.

Repurposing Antidepressants and Phenothiazine Antipsychotics as Efflux Pump Inhibitors in Cancer and Infectious Diseases.

Multidrug resistance (MDR) is a major obstacle in the therapy of infectious diseases and cancer. One of the major mechanisms of MDR is the overexpression of efflux pumps (EPs) that are responsible for extruding antimicrobial and anticancer agents. EPs have additional roles of detoxification that may aid the development of bacterial infection and the progression of cancer. Therefore, targeting EPs may be an attractive strategy to treat bacterial infections and cancer. The development and discovery of a new drug require a long timeline and may come with high development costs. A potential alternative to reduce the time and costs of drug development is to repurpose already existing drugs. Antidepressants and antipsychotic agents are widely used in clinical practice in the treatment of psychiatric disorders and some somatic diseases. Antidepressants and antipsychotics have demonstrated various beneficial activities that may be utilized in the treatment of infections and cancer. This review aims to provide a brief overview of antibacterial and anticancer effects of selective serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs) and phenothiazine antipsychotics, while focusing on EPs. However, it should be noted that the antimicrobial activity of a traditionally non-antibiotic drug may have clinical implications regarding dysbiosis and bacterial MDR.

Late-onset neonatal infections and bacterial multidrug resistance

This study aims to describe bacterial and antimicrobial sensibilities in late-onset healthcare-associated infections (HAIs) with laboratory confirmation in a Neonatal Intensive Care Unit (NICU) of a public hospital in Ceará. This was a cross-sectional study conducted from January 2013 to December 2017. The bacterial types involved in late-onset HAIs, their sensitivity to antimicrobials, and their multidrug resistance were evaluated. The latter was classified according to the criteria revised by the Pan-American Health Organization as multidrug resistance (MDR), extended drug resistance (XDR), or pandrug resistance (PDR). The description of the variables was performed through proportions and frequency distribution depicted in tables. Of the 427 patients with late-onset HAIs, 47 (11.0%) had bacterial infections confirmed by blood cultures, and 7 (14.9%) had infections caused by MDR bacteria. Among the types of bacteria, 26 (55.3%) were Gram-negative bacteria, and 21 (44.7%) were Gram-positive bacteria. Among the Gram-negative bacteria, 92.3% (n=24) showed resistance to more than one antimicrobial, especially to ampicillin (81.2%), cefepime (33.1%), gentamicin (19.4%), and piperacillin/tazobactam (17.2%). Among the MDR ones, three cases had Klebsiella pneumoniae, and three had Pseudomonas aeruginosa, classified as two MDR and one XDR, and three XDR, respectively. Gram-positive resistance to penicillin was the most common one (80.0%), and approximately half of the strains being resistant to oxacillin. Susceptibility was high to vancomycin (97.5%), but one microorganism was resistant to oxacillin and vancomycin. The emergence of MDR strains is a reality in NICUs, carrying the risk of therapeutic failure and requiring continuous prevention protocols aimed at minimizing the risks of contamination by bacteria with high morbidity and mortality.

Dendritic systems for bacterial outer membrane disruption as a method of overcoming bacterial multidrug resistance.

The alarming rise of multi-drug resistant microorganisms has increased the need for new approaches through the development of innovative agents that are capable of attaching to the outer layers of bacteria and causing permanent damage by penetrating the bacterial outer membrane. The permeability (disruption) of the outer membrane of Gram-negative bacteria is now considered to be one of the main ways to overcome multidrug resistance in bacteria. Natural and synthetic permeabilizers such as AMPs and dendritic systems seem promising. However, due to their advantages in terms of biocompatibility, antimicrobial capacity, and wide possibilities for modification and synthesis, highly branched polymers and dendritic systems have gained much more interest in recent years. Various forms of arrangement, and structure of the skeleton, give dendritic systems versatile applications, especially the possibility of attaching other ligands to their surface. This review will focus on the mechanisms used by different types of dendritic polymers, and their complexes with macromolecules to enhance their antimicrobial effect, and to permeabilize the bacterial outer membrane. In addition, future challenges and potential prospects are illustrated in the hope of accelerating the advancement of nanomedicine in the fight against resistant pathogens.

Multidrug-Resistant Escherichia coli Causing Urinary Tract Infections among Controlled and Uncontrolled Type 2 Diabetic Patients at Laquintinie Hospital in Douala, Cameroon.

Urinary tract infections (UTIs) in patients with diabetes are a major public health problem worldwide, particularly in developing countries. This study assessed the resistance profile of Escherichia coli and biochemical abnormalities in controlled and uncontrolled type 2 diabetic patients. A cross-sectional study was conducted at the Douala Laquintinie Hospital from January, 2020, to July, 2021, on the diabetic and nondiabetic participants. The clinical symptoms and biochemical parameters of patient having UTIs were measured using standard methods. E. coli was isolated from urine and an antibiotic susceptibility test was performed using the Kirby-Bauer Agar diffusion method. A total of 851 participants were included with a mean age of 48.54 years. Three hundred and forty-six (40.67%) were nondiabetic, 226 (26.56%) were diabetic patients with balanced blood sugar levels (i.e., glycosylated haemoglobin (HbA1c) is normal), and 279 (32.78%) were diabetic patients with unbalanced blood sugar levels (i.e., patients having an abnormal HbA1c). The prevalence of UTI caused by E. coli was significantly (p < 0.001) higher in diabetics with unbalanced blood sugar levels (15.41%) and diabetics with balanced blood sugar levels (9.73%) compared to nondiabetics (0.87%). Significant (p < 0.001) high frequencies of polyuria (48.39%), proteinuria (29.75%), leukocyturia (27.96%), and polyphagia (8.24%) were observed in diabetic participants with unbalanced blood sugar levels. Significantly (p < 0.001) high average values of aspartate transaminase (25.34; 27.07; 29.93), alanine transaminase (26.08; 27.38; 28.20), creatininemia (8.15; 9.67; 11.31), total cholesterol (1.57; 1.83; 2.63), and atherogenic index (3.81; 6.56; 11.73) were noted in nondiabetics, balanced, and unbalanced blood glucose diabetics, respectively. E. coli showed a high level of resistance to ciprofloxacin (30%), amoxicillin (10.8%), and ofloxacin (9.3%) in diabetic participants with unbalanced blood sugar levels. The antibiotic resistance patterns of the E. coli to triple, quadruple, and quintuple antibiotics were higher when participants had diabetes and even more when diabetes was not controlled. The present findings underline an increased susceptibility of diabetic patients with unbalanced blood sugar levels to multidrug resistant E. coli. Further studies should be conducted to determine the causal association between uncontrolled diabetes and bacterial multidrug resistance.

Cotransfer of resistance to cephalosporins, colistin, and fosfomycin mediated by an IncHI2/pSH16G4928-like plasmid in ESBL-producing monophasic Salmonella Typhimurium strains of pig origin.

To assess the co-transmission risk of phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin in Salmonella strains collected along the whole pork production chain. From a total of 107 Salmonella isolates from samples collected in pig slaughterhouses and markets, 15 ESBL-producing Salmonella strains resistant to cefotaxime were identified by broth microdilution method and clavulanic acid inhibition test, including 14 monophasic Salmonella Typhimurium strains and one Salmonella Derby strain. Whole genome sequence analysis showed that nine monophasic S. Typhimurium strains coresistant to colistin and fosfomycin carried the resistance genes blaCTX-M-14, mcr-1, and fosA3. Conjugational transfer tests demonstrated that the phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin could cotransfer back and forth between Salmonella and Escherichia coli via an IncHI2/pSH16G4928-like plasmid. This study reports the cotransmission of phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin via an IncHI2/pSH16G4928-like plasmid in Salmonella strains of animal origin, giving an alarm for the prevention of the development and spread of bacterial multidrug resistance.

Biomass-derived carbon dots as an emergent antibacterial agent

The biomass-derived Cdots have several advantages over chemically routed synthesized Cdots for promising biological applications. Biomass-derived Cdots are synthesized from medicinally important natural products, suitable for sustainable applications, and biomass offers an excellent carbon source. The bacterial multi-drug resistance has become a serious threat to human health. Hence, the development of biomass-derived Cdots as potential antibacterial agents could be an alternative to presently available antibiotics (or metallodrugs and metal nanoparticles) in primary and secondary care. Herein, we report a rapid microwave-mediated synthesis method of figs-derived (Ficus religiosa tree) red emissive Cdots as a bactericidal agent. The formation of figs-derived Cdots was characterized using various techniques such as Uv-visible spectroscopy, photoluminescence spectroscopy, TRPL, FTIR, TEM, and XPS. The figs-derived Cdots showed superior antibacterial activity against ampicillin-resistant Gram-negative strain of E. coli (DH5α) and tetracyclin-resistant Gram-positive strain of B. subtilis (MTCC 121) than the figs extracted product which has inherent antibacterial activity. The NBT assay revealed that the bacterial cell death might be due to ROS-mediated, which was further confirmed by the SEM study. This study might provide an opportunity to develop biomass-derived Cdots as a novel antibacterial agent to treat drug-resistant bacterial infections.

Harnessing the Role of Bacterial Plasma Membrane Modifications for the Development of Sustainable Membranotropic Phytotherapeutics.

Membrane-targeted molecules such as cationic antimicrobial peptides (CAMPs) are amongst the most advanced group of antibiotics used against drug-resistant bacteria due to their conserved and accessible targets. However, multi-drug-resistant bacteria alter their plasma membrane (PM) lipids, such as lipopolysaccharides (LPS) and phospholipids (PLs), to evade membrane-targeted antibiotics. Investigations reveal that in addition to LPS, the varying composition and spatiotemporal organization of PLs in the bacterial PM are currently being explored as novel drug targets. Additionally, PM proteins such as Mla complex, MPRF, Lpts, lipid II flippase, PL synthases, and PL flippases that maintain PM integrity are the most sought-after targets for development of new-generation drugs. However, most of their structural details and mechanism of action remains elusive. Exploration of the role of bacterial membrane lipidome and proteome in addition to their organization is the key to developing novel membrane-targeted antibiotics. In addition, membranotropic phytochemicals and their synthetic derivatives have gained attractiveness as popular herbal alternatives against bacterial multi-drug resistance. This review provides the current understanding on the role of bacterial PM components on multidrug resistance and their targeting with membranotropic phytochemicals.

The piperazine scaffold for novel drug discovery efforts: the evidence to date

ABSTRACT Introduction . Piperazine is a structural element present in drugs belonging to various chemical classes and used for numerous different therapeutic applications; it has been considered a privileged scaffold for drug design. Areas covered The authors have searched examples of piperazine-containing compounds among drugs recently approved by the FDA, and in some research fields (nicotinic receptor modulators, compounds acting against cancer and bacterial multi-drug resistance), looking in particular to the design behind the insertion of this moiety. Expert opinion Piperazine is widely used due to its peculiar characteristics, such as solubility, basicity, chemical reactivity, and conformational properties. This moiety has represented an important tool to modulate pharmacokinetic and pharmacodynamic properties of drugs.

Silica-Coated Magnetic Nanoparticles for Vancomycin Conjugation.

Drug resistance is a global health challenge with thousands of deaths annually caused by bacterial multidrug resistance (MDR). Efforts to develop new antibacterial molecules do not meet the mounting needs imposed by the evolution of MDR. An alternative approach to overcome this challenge is developing targeted formulations that can enhance the therapeutic efficiency and limit side effects. In this aspect, vancomycin is a potent antibacterial agent that has inherent bacterial targeting properties by binding to the D-Ala-D-Ala moiety of the bacterial peptidoglycan. However, the use of vancomycin is associated with serious side effects that limit its clinical use. Herein, we report the development of vancomycin-conjugated magnetic nanoparticles using a simple conjugation method for targeted antibacterial activity. The nanoparticles were synthesized using a multistep process that starts by coating the nanoparticles with a silica layer, followed by binding an amide linker and then binding the vancomycin glycopeptide. The developed vancomycin-conjugated magnetic nanoparticles were observed to exhibit a spherical morphology and a particle size of 16.3 ± 2.6 nm, with a silica coating thickness of 5 nm and a total coating thickness of 8 nm. The vancomycin conjugation efficiency on the nanoparticles was measured spectrophotometrically to be 25.1%. Additionally, the developed formulation retained the magnetic activity of the nanoparticles, where it showed a saturation magnetization value of 51 emu/g, compared to 60 emu/g for bare magnetic nanoparticles. The in vitro cell biocompatibility demonstrated improved safety where vancomycin-conjugated nanoparticles showed IC50 of 183.43 μg/mL, compared to a much lower value of 54.11 μg/mL for free vancomycin. While the antibacterial studies showed a comparable activity of the developed formulation, the minimum inhibitory concentration was 25 μg/mL, compared to 20 μg/mL for free vancomycin. Accordingly, the reported formulation can be used as a platform for the targeted and efficient delivery of other drugs.

Transmembrane peptide effects on bacterial membrane integrity and organization

As the bacterial multidrug resistance crisis continues, membrane-active antimicrobial peptides are being explored as an alternate treatment to conventional antibiotics. In contrast to antimicrobial peptides, which function by a nonspecific membrane disruption mechanism, here we describe a series of transmembrane (TM) peptides that are designed to act as drug efflux inhibitors by aligning with and out-competing a conserved TM4-TM4 homodimerization motif within bacterial small multidrug resistance proteins. The peptides contain two terminal tags: a C-terminal lysine tag to direct the peptides toward the negatively charged bacterial membrane, and an uncharged N-terminal sarcosine (N-methyl-glycine) tag to promote membrane insertion. While effective at inhibiting efflux activity, ostensibly through their designed mechanism of action, the impact of the peptides on the bacterial inner membrane remains undetermined. To evaluate the extant peptide-membrane interactions, we performed a series of biophysical measurements. Circular dichroism spectroscopy and Trp fluorescence showed that the peptides insert into the membrane generally in helical form. Interestingly, differential scanning calorimetry of the peptides added to bacterial-like membranes (POPE:POPG 3:1) revealed the peptides’ ability to demix the POPE and POPG lipids, creating two pools, one of which is likely a peptide-POPG conglomerate, and the other a POPE-rich component where the native POPG content has been depleted. However, dye leakage assays confirmed that these events occur without causing significant membrane disruption both in vitro and in vivo, indicating that the peptides can target the small multidrug resistance TM4-TM4 motif without nonspecific membrane disruption. In related studies, DiOC2(3) fluorescence indicated moderate peptide-mediated reduction of the proton motive force for all peptides, including control peptides that did not display inhibitory activity. The overall findings suggest that peptides designed with suitable tags, sequence hydrophobicity, and charge distribution can be directed more generally to impact proteins whose function involves membrane-embedded protein-protein interactions.

Research Progress on the Correlation Between Bacterial Biofilm Microenvironment and Charge Regulation

A bacterial biofilm (BF) is composed of microbial communities growing on the surface and extracellular substances secreted by itself, which is one of the main reasons for bacterial multidrug resistance. Analysis and treatment methods based on different principles have been widely used in BF research. Studies have proved that the communication behavior in bacterial BF is also controlled by electrochemical flow. Therefore, it is very effective to study the treatment strategy of new charge regulated anti-BF. Based on the electrical characteristics of bacteria and BF microenvironment, this article summarizes the progress of charge regulation in BF control and prospects the control methods based on the combination of charge regulation and other technologies.

Role of the Two-Component System CiaRH in the Regulation of Efflux Pump SatAB and Its Correlation with Fluoroquinolone Susceptibility.

ABSTRACTStreptococcus suis is an important pathogen in both pigs and humans. Although the diseases associated with S. suis can typically be treated with antibiotics, such use has resulted in a sustained increase in drug resistance. Bacteria can sense and respond to antibiotics via two-component systems (TCSs). In this study, the TCS CiaRH was identified as playing an important role in the susceptibility of S. suis to fluoroquinolones (FQs). We found that a ΔciaRH mutant possessed lower susceptibility to FQs than the wild-type strain, with no observed growth defects at the tested concentrations and lower levels of intracellular drugs and dye. Proteomic data revealed that the levels of SatA and SatB expression were upregulated in the ΔciaRH mutant compared with their levels in the wild-type strain. The satA and satB genes encode a narrow-spectrum FQ efflux pump. The phenomena associated with combined ciaRH-and-satAB deletion mutations almost returned the ΔciaRH ΔsatAB mutant to the phenotype of the wild-type strain compared to the phenotype of the ΔciaRH mutant, suggesting that the resistance of the ΔciaRH strain to FQs could be attributed to satAB overexpression. Moreover, SatAB expression was regulated by CiaR (a response regulator of CiaRH) and SatR (a regulator of the MarR family). The ciaRH genes were consistently downregulated in response to antibiotic stress. The results of electrophoretic mobility shift assays (EMSAs) and affinity assays revealed that both regulator proteins directly controlled the ABC transporter proteins SatAB. Together, the results show that cascade-mediated regulation of antibiotic export by CiaRH is crucial for the ability of S. suis to adapt to conditions of antibiotic pressure. Our study may provide a new target for future antibiotic research and development.IMPORTANCE Streptococcus suis is a zoonotic pathogen with high incidence and mortality rates in both swine and humans. Following antibiotic treatment, the organism has evolved many resistance mechanisms, among which efflux pump overexpression can promote drug extrusion from the cell. This study clarified the role of CiaRH in fluoroquinolone resistance. A mutant with the ciaRH genes deleted showed decreased susceptibility to the antibiotics tested, an invariant growth rate, and reduced intracellular efflux pump substrates. This research also demonstrated that overexpression of the efflux pump SatAB was the main cause of ΔciaRH resistance. In addition, CiaR could combine with the promoter region of satAB to further directly suppress target gene transcription. Simultaneously, satAB was also directly regulated by SatR. Our findings may provide novel insights for the development of drug targets and help to exploit corresponding inhibitors to combat bacterial multidrug resistance.

Antimicrobial, Multidrug Resistance Reversal and Biofilm Formation Inhibitory Effect of Origanum majorana Extracts, Essential Oil and Monoterpenes.

Origanum majorana L. is a widely used medicinal plant; its distilled oil and preparations are extensively utilised in the phytotherapy and food industries. The objective of this study is to evaluate the extracts and the essential oil (EO) of Origanum majorana L, and its monoterpenes for antimicrobial, bacterial multidrug resistance reversing, and biofilm formation inhibitory potency. The composition of EO and n-hexane extract was characterized by GC-MS. In the essential oil terpinen-4-ol (24.92%), trans-sabinene hydrate (25.18%), γ-terpinene (6.48%), cis-sabinene hydrate (5.44%), p-cymene (4.72%), sabinene (4.53%), α-terpineol (4.43%), and α-terpinene (3.00%) were found as the main constituents while trans-sabinene hydrate (1.43%), and terpinen-4-ol (0.19%) were detected in the n-hexane extract besides a series of hydrocarbons. The antibacterial activity of EO and terpinen-4-ol, α-terpinene, and linalool was also assessed against sensitive and drug-resistant S. aureus, and E. coli strains with MIC values of 0.125–0.250% and 30–61 µM, respectively. In the efflux pump (EP) inhibitory assay, made by the ethidium bromide accumulation method in E. coli ATCC 25922, and AG100 and S. aureus ATCC 25923, and MRSA ATCC 43300 strains, EO exhibited substantial activity, especially in the E. coli ATCC 25922 strain. Among the EO constituents, only sabinene was an EP inhibitor in sensitive Escherichia strain. In the case of S. aureus strains, EO and sabinene hydrate exhibited moderate potency on the drug-resistant phenotype. The antibiofilm effects of the samples were tested by crystal violet staining at sub-MIC concentration. γ-Terpinene, terpinen-4-ol, sabinene, sabinene hydrate and linalool were found to be effective inhibitors of biofilm formation (inhibition 36–86%) on E. coli ATCC 25922 and S. aureus MRSA ATCC 43300, while EO was ineffective on these strains. In contrast to this, biofilms formed by E. coli AG100 and S. aureus ATCC 25923 were significantly inhibited by the EO; however, it was not affected by any of the monoterpenes. This observation suggests that the antibiofilm effect might be altered by the synergism between the components of the essential oil.

A Resistome Roadmap: From the Human Body to Pristine Environments

A comprehensive characterization of the human body resistome [sets of antibiotic resistance genes (ARGs)] is yet to be done and paramount for addressing the antibiotic microbial resistance threat. Here, we study the resistome of 771 samples from five major body parts (skin, nares, vagina, gut, and oral cavity) of healthy subjects from the Human Microbiome Project (HMP) and addressed the potential dispersion of ARGs in pristine environments. A total of 28,714 ARGs belonging to 235 different ARG types were found in the HMP proteome dataset (n = 9.1 × 107 proteins analyzed). Our study reveals a distinct resistome profile (ARG type and abundance) between body sites and high interindividual variability. Nares had the highest ARG load (≈5.4 genes/genome) followed by the oral cavity, whereas the gut showed one of the highest ARG richness (shared with nares) but the lowest abundance (≈1.3 genes/genome). The fluroquinolone resistance genes were the most abundant in the human body, followed by macrolide–lincosamide–streptogramin (MLS) or tetracycline. Most ARGs belonged to common bacterial commensals and multidrug resistance trait were predominant in the nares and vagina. Many ARGs detected here were considered as low risk for human health, whereas only a few of them, such as BlaZ, dfrA14, dfrA17, or tetM, were classified as high-risk ARG. Our data also provide hope, since the spread of common ARG from the human body to pristine environments (n = 271 samples; 77 Gb of sequencing data and 2.1 × 108 proteins analyzed) thus far remains very unlikely (only one case found in an autochthonous bacterium from a pristine environment). These findings broaden our understanding of ARG in the context of the human microbiome and the One-Health Initiative of WHO uniting human host–microbes and environments as a whole.

Prevention and control of antimicrobial resistance using CRISPR-Cas system: a review

Bacterial multi-drug resistance (MDR) is a global challenge in the fields of medicine and health, agriculture and fishery, ecology and environment. The cross-region spread of antibiotic resistance genes (ARGs) among different species is one of the main cause of bacterial MDR. However, there is no effective strategies for addressing the intensifying bacterial MDR. The CRISPR-Cas system, consisting of clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR associated proteins, can targetedly degrade exogenous nucleic acids, thus exhibiting high application potential in preventing and controlling bacterial MDR caused by ARGs. This review briefly introduced the working mechanism of CRISPR-Cas systems, followed by discussing recent advances in reducing ARGs by CRISPR-Cas systems delivered through mediators (e.g. plasmids, bacteriophages and nanoparticle). Moreover, the trends of this research field were envisioned, providing a new perspective on preventing and controlling MDR.

In vitro lytic efficacy of bacteriophages against multidrug-resistant pathogenic bacterial species isolated from pyogenic skin infections

Bacterial multidrug resistance has worsened the situation by adding to economic burden but also poses a greater risk of patient death. The aim of the study was to characterize the multidrug resistance (MDR) properties of the bacterial isolates from skin infections and then to isolate and evaluate lytic efficacy of bacteriophages against the pathogenic bacteria. Antimicrobial susceptibilities of the isolates (n=84) from pyogenic skin infections against 14 antibiotics was studied using CLSI guidelines. Phylogenetic analyses of the MDR strains from each species was performed. Lytic efficacy of the sewage-derived phages was assessed by spot test. was the most predominant (57, 68%) of the total of 84 isolates. The number of Gram-negative isolates that were resistant to all antibiotics (except amikacin) were significantly higher (P&amp;#60;0.05). On the other hand, significant number of strains were susceptible only to clindamycin and erythromycin (P&amp;#60;0.05). Phylogenetic analysis based on the 16S rRNA gene revealed close relatedness of the strains with MDR strains previously reported. analysis of select MDR strains (n=20) showed that the bacteriophages ΦDMSA-2, ΦDMEC-1 and ΦDMPA-1 against , , and , respectively, showed lytic efficacy against 4 of 5 MDR strains tested from each species. These preliminary, but still important results emphasize the potential of phages as an effective alternative therapy against MDR bacteria. Further, the lytic efficacy of phages underscores the importance of developing need-based and locally isolated bacteriophages as potential antimicrobial therapy alternative to antibiotics.

Crystal structures of bacterial small multidrug resistance transporter EmrE in complex with structurally diverse substrates.

Proteins from the bacterial small multidrug resistance (SMR) family are proton-coupled exporters of diverse antiseptics and antimicrobials, including polyaromatic cations and quaternary ammonium compounds. The transport mechanism of the Escherichia coli transporter, EmrE, has been studied extensively, but a lack of high-resolution structural information has impeded a structural description of its molecular mechanism. Here, we apply a novel approach, multipurpose crystallization chaperones, to solve several structures of EmrE, including a 2.9 Å structure at low pH without substrate. We report five additional structures in complex with structurally diverse transported substrates, including quaternary phosphonium, quaternary ammonium, and planar polyaromatic compounds. These structures show that binding site tryptophan and glutamate residues adopt different rotamers to conform to disparate structures without requiring major rearrangements of the backbone structure. Structural and functional comparison to Gdx-Clo, an SMR protein that transports a much narrower spectrum of substrates, suggests that in EmrE, a relatively sparse hydrogen bond network among binding site residues permits increased sidechain flexibility.

Infectious complications of induction treatment for acute myeloid leukaemia using the "7 + 3" protocol without antibiotic prophylaxis - 15 years of experience of one clinical site.

Infectious complications during induction chemotherapy of acute myeloid leukaemia are very common. Prophylactic use of antibiotics however is an ongoing challenge in this situation due to bacterial multi-drug resistance. The aim of this study was to provide a comprehensive overview of the incidence of infectious complications in patients with AML undergoing induction therapy using the "7+3" protocol without routine antibiotic prophylaxis at one clinical site providing specialised haematological care in the Czech Republic, over a period of 15 years. The study also evaluates the aetiological spectrum of causative agents and the development of antibiotic resistance in the context of the use of the various classes of antibiotics. The analysis includes evaluation of the importance of risk factors for infectious complications and their impact on treatment of the underlying disease. The data are compared with published figures for similar cohorts of patients. This study presents a retrospective analysis of infectious complications in 242 patients with acute myeloid leukaemia undergoing the first cycle of induction therapy without routine antibiotic prophylaxis in one clinical site in Czech Republic during years 2006-2020. A total of 363 febrile episodes (FE) were recorded. At least 1 FE during the induction was detected in 229 (94.6%) patients. Clinically defined infection was the cause in 96 (26.4%) FEs and blood stream infection in 69 (19.0%) FEs. Both complications occurred simultaneously in 29 (8.0%) FEs. 169 (46.6%) FEs were evaluated as fever of unknown origin (FUO). The achievement of complete remission had a significant effect on the duration of the FE (6 vs. 9 days, P=0.0005) and on the overall survival duration (79.3 vs. 6.5 months, P<0.0001). Patients diagnosed with infection or FUO at diagnosis were significantly more likely to suffer from colonisation by multi-drug resistant bacterial strains at discharge (29.2% vs. 16.3%, P=0.022). This group of patients used antibiotic therapy for a significantly longer time (35 vs. 23 days, P<0.0001). Infection was a contributing cause of death in 18 (7.4%) patients. Mortality was significantly related to the failure to achieve complete remission (P<0.0001). Infectious mortality during induction treatment without routine antibiotic prophylaxis was comparable to the published cohorts with prophylaxis. Regular microbiology surveillance with adequate initial antibiotic treatment can compensate routine antibiotic prophylaxis with slower development of antibiotic resistance.

Inactivation of Opportunistic Pathogens Acinetobacter baumannii and Stenotrophomonas maltophilia by Antimicrobial Photodynamic Therapy.

Acinetobacter baumannii and Stenotrophomonas maltophilia are opportunistic pathogens causing hospital infections with limited treatment options due to bacterial multidrug resistance. Here, we report that antimicrobial photodynamic therapy (aPDT) based on the natural photosensitizers riboflavin and chlorophyllin inactivates A. baumannii and S. maltophilia. The riboflavin and chlorophyllin photostability experiments assessed the photomodifications of photosensitizers under the conditions subsequently used to inactivate A. baumannii and S. maltophilia. A. baumannii planktonic cells were more sensitive to riboflavin-aPDT, while biofilm bacteria were more efficiently inactivated by chlorophyllin-aPDT. S. maltophilia planktonic and biofilm cells were more susceptible to chlorophyllin-aPDT compared to riboflavin-aPDT. The results suggest that riboflavin- and chlorophyllin-aPDT can be considered as a potential antimicrobial treatment for A. baumannii and S. maltophilia inactivation.