Adverse effects of antimicrobials via predictable or idiosyncratic inhibition of host mitochondrial components

Zinc Oxide-Based Nanomaterials for Microbiostatic Activities: A Review

The world is fighting infectious diseases. Therefore, effective antimicrobials are required to prevent the spread of microbes and protect human health. Zinc oxide (ZnO) nano-materials are known for their antimicrobial activities. Because of their distinctive physical and chemical characteristics, they can be used in medical and environmental applications. ZnO-based composites are among the leading sources of antimicrobial research. They are effective at killing (microbicidal) and inhibiting the growth (microbiostatic) of numerous microorganisms, such as bacteria, viruses, and fungi. Although most studies have focused on the microbicidal features, there is a lack of reviews on their microbiostatic effects. This review provides a detailed overview of available reports on the microbiostatic activities of ZnO-based nano-materials against different microorganisms. Additionally, the factors that affect the efficacy of these materials, their time course, and a comparison of the available antimicrobials are highlighted in this review. The basic properties of ZnO, challenges of working with microorganisms, and working mechanisms of microbiostatic activities are also examined. This review underscores the importance of further research to better understand ZnO-based nano-materials for controlling microbial growth.

Antibiotic failure: Beyond antimicrobial resistance

Despite significant progress in antibiotic discovery, millions of lives are lost annually to infections. Surprisingly, the failure of antimicrobial treatments to effectively eliminate pathogens frequently cannot be attributed to genetically-encoded antibiotic resistance. This review aims to shed light on the fundamental mechanisms contributing to clinical scenarios where antimicrobial therapies are ineffective (i.e., antibiotic failure), emphasizing critical factors impacting this under-recognized issue. Explored aspects include biofilm formation and sepsis, as well as the underlying microbiome. Therapeutic strategies beyond antibiotics, are examined to address the dimensions and resolution of antibiotic failure, actively contributing to this persistent but escalating crisis. We discuss the clinical relevance of antibiotic failure beyond resistance, limited availability of therapies, potential of new antibiotics to be ineffective, and the urgent need for novel anti-infectives or host-directed therapies directly addressing antibiotic failure. Particularly noteworthy is multidrug adaptive resistance in biofilms that represent 65 % of infections, due to the lack of approved therapies. Sepsis, responsible for 19.7 % of all deaths (as well as severe COVID-19 deaths), is a further manifestation of this issue, since antibiotics are the primary frontline therapy, and yet 23 % of patients succumb to this condition.

Steno-sphere: Navigating the enigmatic world of emerging multidrug-resistant Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen and frequent cause of serious nosocomial infections. Patient populations at greatest risk for these infections include the immunocompromised and those with chronic respiratory illnesses and prior antibiotic exposure, notably to carbapenems. Its complex virulence and resistance profile drastically limit available antibiotics, and incomplete breakpoint and pharmacokinetic/pharmacodynamic (PK/PD) data to inform dose optimization further complicates therapeutic approaches. Clinical comparison data of first-line agents, including trimethoprim-sulfamethoxazole (TMP-SMX), quinolones, and minocycline, are limited to conflicting observational data with no clear benefit of a single agent or combination therapy. Newer antibiotic approaches, including cefiderocol and aztreonam- avibactam, are promising alternatives for extensively drug-resistant isolates; however, clinical outcomes data are needed. The potential clinical utility of bacteriophage for compassionate use in treating S. maltophilia infections remains to be determined since data is limited to in-vitro and sparse in-vivo work. This article provides a review of available literature for S. maltophilia infection management focused on related epidemiology, resistance mechanisms, identification, susceptibility testing, antimicrobial PK/PD, and emerging therapeutic strategies.

Antibiotic resistance of Streptococcus pneumoniae in Vietnamese children with severe pneumonia: a cross-sectional study

Background

Streptococcus pneumoniae is the most common bacterium that causes community-acquired pneumonia (CAP) in children. The rate of S. pneumoniae resistance to antibiotics is increasing, particularly in patients with severe CAP. Therefore, the level of antibiotic resistance of S. pneumoniae causing severe CAP in Vietnamese children requires regular monitoring.

Methods

This was a cross-sectional descriptive study. Nasopharyngeal aspiration specimens from children were cultured, isolated, and examined for S. pneumoniae. Bacterial strains were assessed for antimicrobial susceptibility, and the minimum inhibitory concentration (MIC) was determined.

Results

Eighty-nine strains of S. pneumoniae were isolated from 239 children with severe CAP. The majority of isolates were completely non-susceptible to penicillin (1.1% intermediate, 98.9% resistant) and highly resistant to erythromycin (96.6%) and clarithromycin (88.8%); the rate of resistance to ceftriaxone was 16.9%, with the proportion of intermediate resistance at 46.0%; 100% of strains were susceptible to vancomycin and linezolid. For most antibiotics, MIC₅₀ and MIC₉₀ were equal to the resistance threshold according to the Clinical and Laboratory Standards Institute 2021; penicillin had an eight-fold increase in MIC₉₀ (64 mg/L) and ceftriaxone had a 1.5-fold increase in MIC₉₀ (6 mg/L).

Conclusion

Streptococcus pneumoniae isolates described in this study were resistant to many antibiotics. Penicillin should not be the first-line antibiotic of choice, and ceftriaxone at an enhanced dose should be used instead.

In-Vitro Study of Indium (III) Sulfate-Containing Medium on the Viability and Adhesion Behaviors of Human Dermal Fibroblast on Engineered Surfaces

Tissues and organs consist of cells organized in specified patterns that support their function, as exemplified by tissues such as skin, muscle, and cornea. It is, therefore, important to understand how external cues, such as engineered surfaces or chemical contaminants, can influence the organization and morphology of cells. In this work, we studied the impact of indium sulfate on human dermal fibroblast (GM5565) viability, production of reactive oxygen species (ROS), morphology, and alignment behavior on tantalum/silicon oxide parallel line/trench surface structures. The viability of cells was measured using the alamarBlue™ Cell Viability Reagent probe, while the ROS levels in cells were quantified using cell-permeant 2',7'-dichlorodihydrofluorescein diacetate. Cell morphology and orientation on the engineered surfaces were characterized using fluorescence confocal and scanning electron microscopy. When cells were cultured in media containing indium (III) sulfate, the average cell viability decreased by as much as ~32% and the concentration of cellular ROS increased. Cell geometry became more circular and compact in the presence of indium sulfate. Even though actin microfilaments continue to preferentially adhere to tantalum-coated trenches in the presence of indium sulfate, the cells are less able to orient along the line axes of the chips. Interestingly, the indium sulfate-induced changes in cell alignment behavior are pattern dependent-a larger proportion of adherent cells on structures with line/trench widths in the range of 1 μm and 10 μm lose the ability to orient themselves, compared to those grown on structures with line widths smaller than 0.5 μm. Our results show that indium sulfate impacts the response of human fibroblasts to the surface structure to which they adhere and underscores the importance of evaluating cell behaviors on textured surfaces, especially in the presence of potential chemical contaminants.

Establishment of an unfed strain of Paramecium bursaria and analysis of associated bacterial communities controlling its proliferation

The ciliate Paramecium bursaria harbors several hundred symbiotic algae in its cell and is widely used as an experimental model for studying symbiosis between eukaryotic cells. Currently, various types of bacteria and eukaryotic microorganisms are used as food for culturing P. bursaria; thus, the cultivation conditions are not uniform among researchers. To unify cultivation conditions, we established cloned, unfed strains that can be cultured using only sterile medium without exogenous food. The proliferation of these unfed strains was suppressed in the presence of antibiotics, suggesting that bacteria are required for the proliferation of the unfed strains. Indeed, several kinds of bacteria, such as Burkholderiales, Rhizobiales, Rhodospirillales, and Sphingomonadales, which are able to fix atmospheric nitrogen and/or degrade chemical pollutants, were detected in the unfed strains. The genetic background of the individually cloned, unfed strains were the same, but the proliferation curves of the individual P. bursaria strains were very diverse. Therefore, we selected multiple actively and poorly proliferating individual strains and compared the bacterial composition among the individual strains using 16S rDNA sequencing. The results showed that the bacterial composition among actively proliferating P. bursaria strains was highly homologous but different to poorly proliferating strains. Using unfed strains, the cultivation conditions applied in different laboratories can be unified, and symbiosis research on P. bursaria will make great progress.

β-Lactam Dosing in Critical Patients: A Narrative Review of Optimal Efficacy and the Prevention of Resistance and Toxicity

Antimicrobial prescription in critically ill patients represents a complex challenge due to the difficult balance between infection treatment and toxicity prevention. Underexposure to antibiotics and therapeutic failure or, conversely, drug overexposure and toxicity may both contribute to a worse prognosis. Moreover, changes in organ perfusion and dysfunction often lead to unpredictable pharmacokinetics. In critically ill patients, interindividual and intraindividual real-time β-lactam antibiotic dose adjustments according to the patient's condition are critical. The continuous infusion of β-lactams and the therapeutic monitoring of their concentration have both been proposed to improve their efficacy, but strong data to support their use are still lacking. The knowledge of the pharmacokinetic/pharmacodynamic targets is poor and is mostly based on observational data. In patients with renal or hepatic failure, selecting the right dose is even more tricky due to changes in drug clearance, distribution, and the use of extracorporeal circuits. Intermittent usage may further increase the dosing conundrum. Recent data have emerged linking overexposure to β-lactams to central nervous system toxicity, mitochondrial recovery delay, and microbiome changes. In addition, it is well recognized that β-lactam exposure facilitates resistance selection and that correct dosing can help to overcome it. In this review, we discuss recent data regarding real-time β-lactam antibiotic dose adjustment, options in special populations, and the impacts on mitochondria and the microbiome.

Antibiotic therapy does not alter mitochondrial bioenergetics in lymphocytes of patients with septic shock - A prospective cohort study

Antibiotics may trigger alterations in mitochondrial function, which has been explored in cells culture, and in animal model of sepsis. This study sought to evaluate whether antibiotic therapy affects mitochondrial bioenergetics in a 68-patients clinical study. We studied mitochondrial respiratory rates at two time points: the first day of antibiotic administration and three days after. The Δbasal, ΔCI, ΔCII respiration, and ΔBCE respiratory rates were not different between patients administered with polymyxin, vancomycin, amoxicillin-clavulanate, and azithromycin compared to those who were not administered. Specific beta-lactams are associated with specific modifications in mitochondrial respiratory endpoints - patients who used meropenem had higher delta C2 values compared to those who did not (p = 0.03). Patients who used piperacillin-tazobactam had lower delta C1 (p = 0.03) values than those who did not, but higher delta C2 values (p = 0.02). These mitochondrial metabolic signatures in isolated lymphocytes challenges the proposed effects of antibiotics in mitochondrial bioenergetics of cell cultures, but at current status have an uncertain clinical significance.

Adherence to practice guidelines for the management of febrile neutropenia in patients undergoing hematopoietic stem cell transplantation: An observational study in a referral center in Iran

INTRODUCTION

Patients undergoing hematopoietic stem cell transplantation (HSCT) are suspected to develop febrile neutropenia (FN) and severe infections. Therefore, appropriate prescription of antibiotics in these patients is crucial to reduce the rates of morbidity, mortality, and antimicrobial resistance. The present study aimed to evaluate the physicians' prescription and adherence to the FN clinical guidelines among patients undergoing HSCT.

METHODS

This prospective observational single-center study was conducted during a 15-month period in a tertiary referral hospital in Iran. The patients with at least one episode of FN following HSCT were included in the current study. The physicians' adherence to the Infectious Diseases Society of America (IDSA) and National Comprehensive Cancer Network (NCCN) clinical guidelines for the management of FN was evaluated using prescription data and medical record reviews.

RESULTS

Two hundred and fifteen patients with 297 FN episodes were evaluated. The timing of antibiotics and the selection of the initial regimen were considered guideline-based therapy. However, antibiotic dosing and initial regimen modification were not followed in terms of the guideline recommendations in 58.1% of the patients. In particular, vancomycin was inappropriately given in 83.1% of patients. The overall adherence of physicians to the guidelines was 35.8%.

CONCLUSION

Non-adherence to clinical guidelines is high particularly in initial regimen modification and administration of vancomycin, which affects hospital stay and patient's outcome. Implementation of guideline-review sessions to raise the awareness of the physicians and to improve the rational use of antimicrobial agents may be crucial.

Toxicity induced by ciprofloxacin and enrofloxacin: oxidative stress and metabolism

Ciprofloxacin (CIP) (human use) and enrofloxacin (ENR) (veterinary use) are synthetic anti-infectious medications that belong to the second generation of fluoroquinolones. They have a wide antimicrobial spectrum and strong bactericidal effects at very low concentrations via enzymatic inhibition of DNA gyrase and topoisomerase IV, which are required for DNA replication. They also have high bioavailability, rapid absorption with favorable pharmacokinetics and excellent tissue penetration, including cerebral spinal fluid. These features have made them the most applied antibiotics in both human and veterinary medicine. ENR is marketed exclusively for animal medicine and has been widely used as a therapeutic veterinary antibiotic, resulting in its residue in edible tissues and aquatic environments, as well as the development of resistance and toxicity. Estimation of the risks to humans due to antimicrobial resistance produced by CIP and ENR is important and of great interest. Moreover, in rare cases due to their overdose and/or prolonged administration, the development of CIP and ENR toxicity may occur. The toxicity of these fluoroquinolones antimicrobials is mainly related to reactive oxygen species (ROS) and oxidative stress (OS) generation, besides metabolism-related toxicity. Therefore, CIP is restricted in pregnant and lactating women, pediatrics and elderly similarly ENR do in the veterinary field. This review manuscript aims to identify the toxicity induced by ROS and OS as a common sequel of CIP and ENR. Furthermore, their metabolism and the role of metabolizing enzymes were reported.

Effects of fluoroquinolones and tetracyclines on mitochondria of human retinal MIO-M1 cells

Our goal was to explore the detrimental impacts of ciprofloxacin (CPFX) and tetracycline (TETRA) on human retinal Müller (MIO-M1) cells in vitro. Cells were exposed to 30, 60 and 120 μg/ml of CPFX and TETRA. The cellular metabolism was measured with the MTT assay. The JC-1 and CM-H2DCFDA assays were used to evaluate the levels of mitochondrial membrane potential (MMP) and ROS (reactive oxygen species), respectively. Mitochondrial DNA (mtDNA) copy number, along with gene expression levels associated with apoptotic (BAX, BCL2-L13, BCL2, CASP-3 and CASP-9), inflammatory (IL-6, IL-1β, TGF-α, TGF-β1 and TGF-β2) and antioxidant pathways (SOD2, SOD3, GPX3 and NOX4) were analyzed via Quantitative Real-Time PCR (qRT-PCR). Bioenergetic profiles were measured using the Seahorse® XF Flux Analyzer. Cells exposed 24 h to 120 μg/ml TETRA demonstrated higher cellular metabolism compared to vehicle-treated cells. At each time points, (i) all TETRA concentrations reduced MMP levels and (ii) ROS levels were reduced by TETRA 120 μg/ml treatment. TETRA caused (i) higher expression of CASP-3, CASP-9, TGF-α, IL-1B, GPX3 and SOD3 but (ii) decreased levels of TGF-B2 and SOD2. ATP production and spare respiratory capacity declined with TETRA treatment. Cellular metabolism was reduced with CPFX 120 μg/ml in all cultures and 60 μg/ml after 72 h. The CPFX 120 μg/ml reduced MMP in all cultures and ROS levels (72 h). CPFX treatment (i) increased expression of CASP-3, CASP-9, and BCL2-L13, (ii) elevated the basal oxygen consumption rate, and (iii) lowered the mtDNA copy numbers and expression levels of TGF-B2, IL-6 and IL-1B compared to vehicle-control cells. We conclude that clinically relevant dosages of bactericidal and bacteriostatic antibiotics can have negative effects on the cellular metabolism and mitochondrial membrane potential of the retinal MIO-M1 cells in vitro. It is noteworthy to mention that apoptotic and inflammatory pathways in exposed cells were affected significantly This is the first study showing the negative impact of fluoroquinolones and tetracyclines on mitochondrial behavior of human retinal MIO-M1 cells.

Infectious Diseases Society of America Guidance on the Treatment of AmpC β-lactamase-Producing Enterobacterales, Carbapenem-Resistant Acinetobacter baumannii, and Stenotrophomonas maltophilia Infections

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. A previous guidance document focused on infections caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa). Here, guidance is provided for treating AmpC β-lactamase-producing Enterobacterales (AmpC-E), carbapenem-resistant Acinetobacter baumannii (CRAB), and Stenotrophomonas maltophilia infections.

METHODS

A panel of six infectious diseases specialists with expertise in managing antimicrobial-resistant infections formulated questions about the treatment of AmpC-E, CRAB, and S. maltophilia infections. Answers are presented as suggestions and corresponding rationales. In contrast to guidance in the previous document, published data on optimal treatment of AmpC-E, CRAB, and S. maltophilia infections are limited. As such, guidance in this document is provided as "suggested approaches" based on clinical experience, expert opinion, and a review of the available literature. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment suggestions are provided, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Suggestions apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of September 17, 2021 and will be updated annually. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance-2.0/.

Management of chronic Pseudomonas aeruginosa infection with inhaled levofloxacin in people with cystic fibrosis

People with cystic fibrosis (CF) are highly susceptible to bacterial infections of the airways. By adulthood, chronic Pseudomonas aeruginosa (Pa) is the most prevalent infective organism and is difficult to eradicate owing to its adaptation to the CF lung microenvironment. Long-term suppressive treatment with inhaled antimicrobials is the standard care for reducing exacerbation frequency, improving quality of life and increasing measures of lung function. Levofloxacin (a fluoroquinolone antimicrobial) has been approved as an inhaled solution in Europe and Canada, for the treatment of adults with CF with chronic P. aeruginosa pulmonary infections. Here, we review the clinical principles relating to the use of inhaled antimicrobials and inhaled levofloxacin for the management of P. aeruginosa infections in patients with CF.

MFS1, a Pleiotropic Transporter in Dermatophytes That Plays a Key Role in Their Intrinsic Resistance to Chloramphenicol and Fluconazole

A recently identified Trichophyton rubrum major facilitator superfamily (MFS)-type transporter (TruMFS1) has been shown to give resistance to azole compounds and cycloheximide (CYH) when overexpressed in Saccharomyces cerevisiae. We investigated the roles of MFS1 in the intrinsic resistance of dermatophytes to CYH and chloramphenicol (CHL), which are commonly used to isolate these fungi, and to what extent MFS1 affects the susceptibility to azole antifungals. Susceptibility to antibiotics and azoles was tested in S. cerevisiae overexpressing MFS1 and ΔMFS1 mutants of Trichophyton benhamiae, a dermatophyte that is closely related to T. rubrum. We found that TruMFS1 functions as an efflux pump for CHL in addition to CYH and azoles in S. cerevisiae. In contrast, the growth of T. benhamiae ΔMFS1 mutants was not reduced in the presence of CYH but was severely impaired in the presence of CHL and thiamphenicol, a CHL analog. The suppression of MFS1 in T. benhamiae also increased the sensitivity of the fungus to fluconazole and miconazole. Our experiments revealed a key role of MFS1 in the resistance of dermatophytes to CHL and their high minimum inhibitory concentration for fluconazole. Suppression of MFS1 did not affect the sensitivity to CYH, suggesting that another mechanism was involved in resistance to CYH in dermatophytes.

Drug-related problems of antibiotic use in gastroenteritis related to patient therapy outcomes at Universitas Gadjah Mada Hospital

OBJECTIVES

Gastroenteritis is a disease of digestive system commonly occur among the people. Some cases of gastroenteritis are caused by bacteria, so it is treated by using antibiotics. Inappropriate use of antibiotics can be associated to Drug-Related Problems (DRPs). This study aims to identify patterns of potential DRPs of antibiotic use and analyze the effect of potential DRPs of antibiotic use toward the patient's therapeutic outcomes and length of stay.

METHODS

This is a retrospective cross-sectional study carried out by using patient's medical record. The study population was gastroenteritis patients at the inpatient ward of Universitas Gadjah Mada Hospital during January 2018-June 2019. Then, SPSS was employed to analyze the data and the effect of potential DRPs toward therapeutic outcomes was analyzed by utilizing the chi-square method.

RESULTS

More than half of gastroenteritis patients in Universitas Gadjah Mada Hospital were identified to have potential DRPs of antibiotic use. The most identified of potential DRPs was problems related to drug selection. Based on the chi-square analysis, there was no relationship between potential DRPs of antibiotic use and the therapeutic outcome. In addition, there was also no relationship between potential DRPs of antibiotic use and patient's length of stay.

CONCLUSIONS

The potential DRPs of antibiotics use do not have a significant effect on the therapeutic outcome and length of stay of the gastroenteritis patients in Universitas Gadjah Mada Hospital.

Elucidating the Antimycobacterial Mechanism of Action of Ciprofloxacin Using Metabolomics

In the interest of developing more effective and safer anti-tuberculosis drugs, we used a GCxGC-TOF-MS metabolomics research approach to investigate and compare the metabolic profiles of Mtb in the presence and absence of ciprofloxacin. The metabolites that best describe the differences between the compared groups were identified as markers characterizing the changes induced by ciprofloxacin. Malic acid was ranked as the most significantly altered metabolite marker induced by ciprofloxacin, indicative of an inhibition of the tricarboxylic acid (TCA) and glyoxylate cycle of Mtb. The altered fatty acid, myo-inositol, and triacylglycerol metabolism seen in this group supports previous observations of ciprofloxacin action on the Mtb cell wall. Furthermore, the altered pentose phosphate intermediates, glycerol metabolism markers, glucose accumulation, as well as the reduction in the glucogenic amino acids specifically, indicate a flux toward DNA (as well as cell wall) repair, also supporting previous findings of DNA damage caused by ciprofloxacin. This study further provides insights useful for designing network whole-system strategies for the identification of possible modes of action of various drugs and possibly adaptations by Mtb resulting in resistance.

Binding and Action of Triphenylphosphonium Analog of Chloramphenicol upon the Bacterial Ribosome

Chloramphenicol (CHL) is a ribosome-targeting antibiotic that binds to the peptidyl transferase center (PTC) of the bacterial ribosome and inhibits peptide bond formation. As an approach for modifying and potentially improving the properties of this inhibitor, we explored ribosome binding and inhibitory properties of a semi-synthetic triphenylphosphonium analog of CHL-CAM-C4-TPP. Our data demonstrate that this compound exhibits a ~5-fold stronger affinity for the bacterial ribosome and higher potency as an in vitro protein synthesis inhibitor compared to CHL. The X-ray crystal structure of the Thermus thermophilus 70S ribosome in complex with CAM-C4-TPP reveals that, while its amphenicol moiety binds at the PTC in a fashion identical to CHL, the C4-TPP tail adopts an extended propeller-like conformation within the ribosome exit tunnel where it establishes multiple hydrophobic Van der Waals interactions with the rRNA. The synthesized compound represents a promising chemical scaffold for further development by medicinal chemists because it simultaneously targets the two key functional centers of the bacterial ribosome-PTC and peptide exit tunnel.

Antibacterial Chitosan Nanofiber Thin Films with Bacitracin Zinc Salt

Chitosan nanofiber has a highly uniform structure of 20–50 nm in diameter and shows high dispersibility in water due to its submicron size and high surface-to-volume ratio. The stacked nanofibers film is useful for breathability because it has a gap with a size of several tens of nm or more. However, the chemical bonds between the nanofibers cannot be broken during use. In this study, the thin films were obtained by filtration of chitosan nanofibers and 3-glycidoxypropyltrimethoxysilane (GPTMS) mixture. The addition of GPTMS changed the wettability, mechanical property and stability in water of the thin films. Bacitracin zinc salt (BZ) has been used for the localized dermatological medicines and loaded in the films. BZ interacted electrostatically with the thin films matrix and the release of BZ was controlled by the amount of GPTMS. A higher released amount of BZ showed higher antibacterial effects toward S. aureus. The film was also tested their toxicity by L929 fibroblasts. The release of less than 11.9 μg of BZ showed antibacterial effects, but were not toxic for fibroblast cells.

A stalled-ribosome rescue factor Pth3 is required for mitochondrial translation against antibiotics in Saccharomyces cerevisiae

Mitochondrial translation appears to involve two stalled-ribosome rescue factors (srRFs). One srRF is an ICT1 protein from humans that rescues a "non-stop" type of mitochondrial ribosomes (mitoribosomes) stalled on mRNA lacking a stop codon, while the other, C12orf65, reportedly has functions that overlap with those of ICT1; however, its primary role remains unclear. We herein demonstrated that the Saccharomyces cerevisiae homolog of C12orf65, Pth3 (Rso55), preferentially rescued antibiotic-dependent stalled mitoribosomes, which appear to represent a "no-go" type of ribosomes stalled on intact mRNA. On media containing a non-fermentable carbon source, which requires mitochondrial gene expression, respiratory growth was impaired significantly more by the deletion of PTH3 than that of the ICT1 homolog PTH4 in the presence of antibiotics that inhibit mitochondrial translation, such as tetracyclines and macrolides. Additionally, the in organello labeling of mitochondrial translation products and quantification of mRNA levels by quantitative RT-PCR suggested that in the presence of tetracycline, the deletion of PTH3, but not PTH4, reduced the protein expression of all eight mtDNA-encoded genes at the post-transcriptional or translational level. These results indicate that Pth3 can function as a mitochondrial srRF specific for ribosomes stalled by antibiotics and plays a role in antibiotic resistance in fungi.

A novel nanohybrid antimicrobial based on chitosan nanoparticles and antimicrobial peptide microcin J25 with low toxicity

Bacterial resistance to antibiotics is a critical public health concern. Alternatives of antibiotics are needed urgently. Herein, we designed and engineered a new nano-antimicrobial, chitosan nanoparticles (CNs)-antimicrobial peptide microcin J25 (MccJ25) conjugates (CNMs). The engineered CNMs proved to be highly active against Gram-negative and Gram-positive bacteria, and the activity of CNMs and CNs was stable in various thermal and pH environments. Escherichia coli K88 strain treated with CNMs did not acquire resistance in serial passage assays over a period of 18 days. Risk assessment with cell lines showed that CNMs did not cause toxicity. Additionally, CNMs did not reduce the lifespan of C. elegans. In summary, this study demonstrated that CNMs can serve as an excellent novel antimicrobial agent against multi-drug resistance pathogens.

Ribosome-targeting antibacterial agents: Advances, challenges, and opportunities

Ribosomes, which synthesize proteins, are critical organelles for the survival and growth of bacteria. About 60% of approved antibiotics discovered so far combat pathogenic bacteria by targeting ribosomes. However, several issues, such as drug resistance and toxicity, have impeded the clinical use of ribosome-targeting antibiotics. Moreover, the complexity of the bacteria ribosome structure has retarded the discovery of new ribosome-targeting agents that are considered as the key to the drug-resistance and toxicity. To deal with these challenges, efforts such as medicinal chemistry optimization, combination treatment, and new drug delivery system have been developed. But not enough, the development of structural biology and new screening methods bring powerful tools, such as cryo-electron microscopy technology, advanced computer-aided drug design, and cell-free in vitro transcription/translation systems, for the discovery of novel ribosome-targeting antibiotics. Thus, in this paper, we overview the research on different aspects of bacterial ribosomes, especially focus on discussing the challenges in the discovery of ribosome-targeting antibacterial drugs and advances made to address issues such as drug-resistance and selectivity, which, we believe, provide perspectives for the discovery of novel antibiotics.

Green synthesis of a deep-ultraviolet carbonized nanoprobe for ratiometric fluorescent detection of feroxacin and enrofloxacin in food and serum samples

A sensitive ratiometric fluorescent probe for EFC and FXC detection in milk and bovine serum samples based on the internal filtration effect.

Selective toxicity of antibacterial agents-still a valid concept or do we miss chances and ignore risks?

BACKGROUND

Selective toxicity antibacteribiotics is considered to be due to interactions with targets either being unique to bacteria or being characterized by a dichotomy between pro- and eukaryotic pathways with high affinities of agents to bacterial- rather than eukaryotic targets. However, the theory of selective toxicity oversimplifies the complex modes of action of antibiotics in pro- and eukaryotes.

METHODS AND OBJECTIVE

This review summarizes data describing multiple modes of action of antibiotics in eukaryotes.

RESULTS

Aminoglycosides, macrolides, oxazolidinones, chloramphenicol, clindamycin, tetracyclines, glycylcyclines, fluoroquinolones, rifampicin, bedaquillin, ß-lactams inhibited mitochondrial translation either due to binding to mitosomes, inhibition of mitochondrial RNA-polymerase-, topoisomerase 2ß-, ATP-synthesis, transporter activities. Oxazolidinones, tetracyclines, vancomycin, ß-lactams, bacitracin, isoniazid, nitroxoline inhibited matrix-metalloproteinases (MMP) due to chelation with zinc and calcium, whereas fluoroquinols fluoroquinolones and chloramphenicol chelated with these cations, too, but increased MMP activities. MMP-inhibition supported clinical efficacies of ß-lactams and daptomycin in skin-infections, and of macrolides, tetracyclines in respiratory-diseases. Chelation may have contributed to neuroprotection by ß-lactams and fluoroquinolones. Aminoglycosides, macrolides, chloramphenicol, oxazolidins oxazolidinones, tetracyclines caused read-through of premature stop codons. Several additional targets for antibiotics in human cells have been identified like interaction of fluoroquinolones with DNA damage repair in eukaryotes, or inhibition of mucin overproduction by oxazolidinones.

CONCLUSION

The effects of antibiotics on eukaryotes are due to identical mechanisms as their antibacterial activities because of structural and functional homologies of pro- and eukaryotic targets, so that the effects of antibiotics on mammals are integral parts of their overall mechanisms of action.

A Robust Symbiotic Relationship Between the Ciliate Paramecium multimicronucleatum and the Bacterium Ca. Trichorickettsia Mobilis

Close reciprocal interactions in symbiotic systems have suggested the holobiont concept, in which the host and its microbiota are considered as a single entity. Ciliates are known for their ability to form symbiotic associations with prokaryotes. Relationships between the partners in such systems vary from mutualism to parasitism and differ significantly in their robustness. We assessed the viability of the ciliate Paramecium multimicronucleatum and its ability to maintain its intranuclear endosymbiont Ca. Trichorickettsia mobilis (Rickettsiaceae) after treatment with antibiotics characterized by different mode of action, such as ampicillin, streptomycin, chloramphenicol, tetracycline. The presence of endosymbionts in the host cell was determined by means of living cell observations made using differential interference contrast or fluorescence in situ hybridization with the species-specific oligonucleotide probe (FISH). Administration of antibiotics traditionally used in treatments of rickettsioses, tetracycline and chloramphenicol, depending on the concentration used and the ciliate strain treated, either caused death of both, infected and control cells, or did not affect the ability of the host to maintain the intranuclear endosymbiont. The surviving cells always manifested motile bacteria in the macronucleus. Streptomycin treatment never led to the loss of endosymbionts in any of the four infected strains, and nearly all ciliates remained viable. Ampicillin treatment never caused host cell death, but resulted in formation of filamentous and immobile oval bacterial forms. Under repeated ampicillin treatments, a part of endosymbionts was registered in the host cytoplasm, as evidenced both by FISH and transmission electron microscopy. Endosymbionts located in the host cytoplasm were enclosed in vacuoles, apparently, corresponding to autophagosomes. Nevertheless, the bacteria seemed to persist in this compartment and might cause relapse of the infection. Although the antibiotic sensitivity profile of Trichorickettsia seems to resemble that of other representatives of Rickettsiaceae, causative agents of severe diseases in humans, neither of the antibiotic treatments used in this study resulted in an aposymbiotic cell line, apparently, due to the protists’ sensitivity to tetracyclines, the drugs of preference in rickettsiosis treatment. The observed robustness of this symbiotic system makes it a good model for further elaboration of the holobiont concept.

Antibiotic-induced gut dysbiosis and barrier disruption and the potential protective strategies

The oral antibiotic therapies administered widely to people and animals can cause gut dysbiosis and barrier disruption inevitably. Increasing attention has been directed toward antibiotic-induced gut dysbiosis, which involves a loss of diversity, changes in the abundances of certain taxa and consequent effects on their metabolic capacity, and the spread of antibiotic-resistant bacterial strains. Treatment with beta-lactam, glycopeptide, and macrolide antibiotics is associated with the depletion of beneficial commensal bacteria in the genera Bifidobacterium and Lactobacillus. The gut microbiota is a reservoir for antibiotic resistance genes, the prevalence of which increases sharply after antibiotic ingestion. The intestinal barrier, which comprises secretory, physical, and immunological barriers, is also a target of antibiotics. Antibiotic induced changes in the gut microbiota composition could induce weakening of the gut barrier through changes in mucin, cytokine, and antimicrobial peptide production by intestinal epithelial cells. Reports have indicated that dietary interventions involving prebiotics, probiotics, omega-3 fatty acids, and butyrate supplementation, as well as fecal microbiota transplantation, can alleviate antibiotic-induced gut dysbiosis and barrier injuries. This review summarizes the characteristics of antibiotic-associated gut dysbiosis and barrier disruption, as well as the strategies for alleviating this condition. This information is intended to provide a foundation for the exploration of safer, more efficient, and affordable strategies to prevent or relieve antibiotic-induced gut injuries.

Repurposing of Existing Statin Drugs for Treatment of Microbial Infections: How Much Promising?

Today's microbial infections' resistance to approved drugs, the emergence of new infectious diseases and lack of vaccines, create a huge threat to human health. Thus, there is an urgent need to create novel antimicrobial agents, but the high cost and prolonged timeline of novel drug discovery and development is the major barrier to make new drugs. Therefore, there is a need for specific cost effective approaches in order to identify new drugs for the treatment of various microbial infections. Drug repurposition is an alternative technique to find existing clinically approved drugs for other indications. This approach may enhance the portfolio of Pharmaceutical companies by reducing the time and money required for the development of new chemical entity. In literature, various studies have reported some encouraging results regarding the antimicrobial use of existing statin drugs. Further, some clinical studies have also shown the protective effect of statin drugs in reduction of the morbidity and mortality due to many infectious diseases but complete understanding is still lacking. Thus, there is a need for better understanding of the use of statin drugs, especially in the context of antimicrobial effects. In this review, we try to summarize the use of statin drugs in various infectious diseases and their proposed antimicrobial mechanism of action. Further, current challenges and future perspectives of repurposition of statin drugs as antimicrobial agents have also been discussed.

Bacterial Exposure Mediates Developmental Plasticity and Resistance to Lethal Vibrio lentus Infection in Purple Sea Urchin (Strongylocentrotus purpuratus) Larvae

Exposure to and colonization by bacteria during development have wide-ranging beneficial effects on animal biology but can also inhibit growth or cause disease. The immune system is the prime mediator of these microbial interactions and is itself shaped by them. Studies using diverse animal taxa have begun to elucidate the mechanisms underlying the acquisition and transmission of bacterial symbionts and their interactions with developing immune systems. Moreover, the contexts of these associations are often confounded by stark differences between "wild type" microbiota and the bacterial communities associated with animals raised in conventional or germ-free laboratories. In this study, we investigate the spatio-temporal kinetics of bacterial colonization and associated effects on growth and immune function in larvae of the purple sea urchin (Strongylocentrotus purpuratus) as a model for host-microbe interactions and immune system development. We also compare the host-associated microbiota of developing embryos and larvae raised in natural seawater or exposed to adult-associated bacteria in the laboratory. Bacteria associated with zygotes, embryos, and early larvae are detectable with 16S amplicon sequencing, but 16S-FISH indicates that the vast majority of larval bacterial load is acquired after feeding begins and is localized to the gut lumen. The bacterial communities of laboratory-cultured embryos are significantly less diverse than the natural microbiota but recapitulate its major components (Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes), suggesting that biologically relevant host-microbe interactions can be studied in the laboratory. We also demonstrate that bacterial exposure in early development induces changes in morphology and in the immune system. In the absence of bacteria, larvae grow larger at the 4-arm stage. Additionally, bacteria-exposed larvae are significantly more resistant to lethal infection with the larva-associated pathogen Vibrio lentus suggesting that early exposure to high levels of microbes, as would be expected in natural conditions, affects the immune state in later larvae. These results expand our knowledge of microbial influences on early sea urchin development and establish a model in which to study the interactions between the developing larval immune system and the acquisition of larval microbiota.

Mitochondrial Toxicity of Azithromycin Results in Aerobic Glycolysis and DNA Damage of Human Mammary Epithelia and Fibroblasts

Mitochondria evolved from free-living bacteria via endocytosis within eukaryotic host cells millions of year ago. We hypothesized that antibiotics cause mammalian mitochondrial damage while causing bacterial lethality. Mitochondrial toxicity of azithromycin in human mammary epithelia MCF-12A and fibroblasts were tested by fluorescent and transmission electron microscopy. Gene expression and DNA damage were tested by real-time polymerase chain reaction (qPCR) and ELISA. We found azithromycin suppressed the mitochondrial membrane potential gradient of MCF-12A cells and fibroblasts. Ultrastructure exams showed that the antibiotic caused vacuolated and swollen mitochondria with disrupted cristae in MCF-12A cells and fibroblasts compared to the morphology of mitochondria in the cells without antibiotic treatment. Fluorescent microscopy also showed azithromycin-induced mitochondrial reactive oxygen species (ROS), superoxide, after 3 h of culture. The DNA oxidative damage product, 8-hydroxy-2’-deoxyguanosine (8-OHdG, significantly increased in the media after MCF-12A cells and fibroblasts were cultured in the media containing azithromycin for 24 h. Azithromycin upregulated gene expression of hypoxia inducible factor 1 alpha (HIF1a), glycolytic enzymes including hexokinase 2 (HK2), phosphofructokinase 1 (PFKM), pyruvate kinase muscle isozyme M2 (PKM2), and glucose transporters in MCF-12A cells and fibroblasts. Lactate production also increased in the culture media. After treatment with azithromycin, healthy MCF-12A and fibroblast cells increased aerobic glycolysis—the “Warburg Effect”—to generate energy. In summary, azithromycin caused mitochondrial toxicity, ROS overproduction, DNA oxidative damage, upregulation of the HIF1a gene, and aerobic glycolysis in healthy mammalian cells. Over-usage of antibiotics could contribute to tumorigenesis and neurodegeneration and aggravate existing mitochondria-associated diseases.

Multi-drug-resistant Enterococcus faecium bacteraemia in a liver transplant recipient

Introduction

Enterococcus faecium is a commensal organism commonly colonizing the human gastrointestinal tract. Although it is generally a non-virulent organism, E. faecium can cause significant morbidity and mortality due to its inherent and acquired resistances to commonly used antimicrobials. Patients who are immunosuppressed are particularly vulnerable.

Case presentation

A 65–75-year-old patient with a history of an orthotopic liver transplant for hepatitis C infection and diabetes was re-admitted to the hospital with abdominal pain and fever. The patient had several recent admissions related to the presentation reported here, which included treatment with a prolonged course of broad-spectrum antibiotics. The patient was found to have a recurrent liver abscess and blood cultures grew vancomycin-resistant E. faecium, non-susceptible to all tested agents: ampicillin, penicillin, vancomycin, daptomycin and linezolid. The patient was started initially on chloramphenicol intravenously while awaiting additional susceptibility testing, which ultimately revealed chloramphenicol non-susceptibility. Tigecycline was started but the patient ultimately decided to pursue hospice care.

Conclusion

Multi-drug-resistant organisms are increasingly being recognized and are associated with poorer outcomes, particularly in immunosuppressed patients. We describe a particularly resistant organism and discuss potential therapeutic options.

Mitochondrial Genome Variation Affects Multiple Respiration and Nonrespiration Phenotypes in Saccharomyces cerevisiae

Mitochondrial genome variation and its effects on phenotypes have been widely analyzed in higher eukaryotes but less so in the model eukaryote Saccharomyces cerevisiae Here, we describe mitochondrial genome variation in 96 diverse S. cerevisiae strains and assess associations between mitochondrial genotype and phenotypes as well as nuclear-mitochondrial epistasis. We associate sensitivity to the ATP synthase inhibitor oligomycin with SNPs in the mitochondrially encoded ATP6 gene. We describe the use of iso-nuclear F1 pairs, the mitochondrial genome equivalent of reciprocal hemizygosity analysis, to identify and analyze mitochondrial genotype-dependent phenotypes. Using iso-nuclear F1 pairs, we analyze the oligomycin phenotype-ATP6 association and find extensive nuclear-mitochondrial epistasis. Similarly, in iso-nuclear F1 pairs, we identify many additional mitochondrial genotype-dependent respiration phenotypes, for which there was no association in the 96 strains, and again find extensive nuclear-mitochondrial epistasis that likely contributes to the lack of association in the 96 strains. Finally, in iso-nuclear F1 pairs, we identify novel mitochondrial genotype-dependent nonrespiration phenotypes: resistance to cycloheximide, ketoconazole, and copper. We discuss potential mechanisms and the implications of mitochondrial genotype and of nuclear-mitochondrial epistasis effects on respiratory and nonrespiratory quantitative traits.

Effect of Ciprofloxacin on Susceptibility to Aortic Dissection and Rupture in Mice

Importance

Fluoroquinolones are among the most commonly prescribed antibiotics. Recent clinical studies indicated an association between fluoroquinolone use and increased risk of aortic aneurysm and dissection (AAD). This alarming association has raised concern, especially in patients with AAD with risk of rupture and in individuals at risk for developing AAD.

Objective

To examine the effect of ciprofloxacin on AAD development in mice.

Design, Setting, and Participants

In a mouse model of moderate, sporadic AAD, 4-week-old male and female C57BL/6J mice were challenged with a high-fat diet and low-dose angiotensin infusion (1000 ng/min/kg). Control unchallenged mice were fed a normal diet and infused with saline. After randomization, challenged and unchallenged mice received ciprofloxacin (100 mg/kg/d) or vehicle through daily gavage during angiotensin or saline infusion. Aortic aneurysm and dissection development and aortic destruction were compared between mice. The direct effects of ciprofloxacin on aortic smooth muscle cells were examined in cultured cells.

Results

No notable aortic destruction was observed in unchallenged mice that received ciprofloxacin alone. Aortic challenge induced moderate aortic destruction with development of AAD in 17 of 38 mice (45%) and severe AAD in 9 (24%) but no rupture or death. However, challenged mice that received ciprofloxacin had severe aortic destruction and a significantly increased incidence of AAD (38 of 48 [79%]; P = .001; χ2 = 10.9), severe AAD (32 of 48 [67%]; P < .001; χ2 = 15.7), and rupture and premature death (7 of 48 [15%]; P = .01; χ2 = 6.0). The increased AAD incidence was observed in different aortic segments and was similar between male and female mice. Compared with aortic tissues from challenged control mice, those from challenged mice that received ciprofloxacin showed decreased expression of lysyl oxidase, an enzyme that is critical in the assembly and stabilization of elastic fibers and collagen. These aortas also showed increased matrix metalloproteinase levels and activity, elastic fiber fragmentation, and aortic cell injury. In cultured smooth muscle cells, ciprofloxacin treatment significantly reduced lysyl oxidase expression and activity, increased matrix metalloproteinase expression and activity, suppressed cell proliferation, and induced cell death. Furthermore, ciprofloxacin-a DNA topoisomerase inhibitor-caused nuclear and mitochondrial DNA damage and the release of DNA into the cytosol, subsequently inducing mitochondrial dysfunction, reactive oxygen species production, and activation of the cytosolic DNA sensor STING, which we further showed was involved in the suppression of lysyl oxidase expression and induction of matrix metalloproteinase expression.

Conclusions and Relevance

Ciprofloxacin increases susceptibility to aortic dissection and rupture in a mouse model of moderate, sporadic AAD. Ciprofloxacin should be used with caution in patients with aortic dilatation, as well as in those at high risk for AAD.

Design, synthesis, DFT, docking studies and ADME prediction of some new coumarinyl linked pyrazolylthiazoles: Potential standalone or adjuvant antimicrobial agents

The control of antimicrobial resistance (AMR) seems to have come to a dead end. The major consequences of the use and abuse of antibacterial drugs are the development of resistant strains due to genetic mutability of both pathogenic and nonpathogenic microorganisms. We, herein, report the synthesis, characterization and biological activities of coumarin-thiazole-pyrazole (CTP) molecular hybrids with an effort to explore and overcome the increasing antimicrobial resistance. The compounds were characterized by analyzing their IR, Mass, 1H and13C NMR spectral data and elemental analysis. The in vitro antimicrobial activity of the synthesized compounds was investigated against various pathogenic strains; the results obtained were further explained with the help of DFT and molecular orbital calculations. Compound 1b and 1f displayed good antimicrobial activity and synergistic effects when used with kanamycin and amphotericin B. Furthermore, in vitro cytotoxicity of compounds 1b and 1f were studied against HeLa cells (cervical cancer cell) and Hek-293 cells. The results of molecular docking study were used to better rationalize the action and prediction of the binding modes of these compounds.

Removal of the cecum affects intestinal fermentation, enteric bacterial community structure, and acute colitis in mice

The murine cecum is a major site of fermentation of dietary materials, and production of short chain fatty acids (SCFAs). To examine the role that the cecum plays in acute bacterial infection in mice, the cecum was surgically removed, and changes in bacterial communities and production of SCFAs were analyzed relative to surgical sham animals. To incite bacterial colitis, mice were orally challenged with Citrobacter rodentium. The impact of butyrate administered directly into the colon was also examined. Concentrations of SCFAs in feces were substantially lower in mice with an excised cecum. Bacterial communities were also less diverse in cecectomized mice, and densities of major SCFA-producing taxa including bacteria within the Ruminococcaceae and Lachnospiraceae families were reduced. Colonization of the intestine by C. rodentium was not affected by removal of the cecum, and the bacterium equally incited acute colitis in mice with and without a cecum. However, cecectomized mice exhibited lower body weights at later stages of infection indicating an impaired ability to recover following challenge with C. rodentium. Furthermore, removal of the cecum altered immune and inflammatory responses to infection including increased inflammatory markers in the proximal colon (Tnfα, Il10, βd1), and heightened inflammatory response in the proximal and distal colon (Ifnγ, Tnfα, Relmβ). Exogenous administration of butyrate was insufficient to normalize responses to C. rodentium in cecectomized mice. The murine cecum plays a critical role in maintaining intestinal health, and the murine cecectomy model may be a useful tool in elucidating key aspects of intestine-pathogen-microbiota interactions.

Lumbar hemilaminectomy for treatment of diskospondylitis in an aardvark (Orycteropus afer)

CASE DESCRIPTION A 17-year-old sexually intact male aardvark (Orycteropus afer) was evaluated because of hind limb proprioception deficits and ataxia. CLINICAL FINDINGS Results of examination and CT suggested a diagnosis of intervertebral disk disease and diskospondylitis at the L2-3 intervertebral space. Magnetic resonance imaging of the vertebral column also indicated intervertebral disk rupture with spinal cord compression and inflammation of the adjacent epaxial musculature TREATMENT AND OUTCOME Hemilaminectomy was performed according to the technique described for dogs. Anatomic variations encountered intraoperatively limited the ability to completely remove the affected disk material; however, adequate decompression of the spinal cord was achieved. Microbial culture and susceptibility testing of surgical biopsy specimens yielded a multidrug-resistant Enterococcus faecalis that was treated with a 10-week course of linezolid. Intensive postoperative care required constant rate infusions for adequate sedation, analgesia, and antimicrobial treatment. Dehiscence of the surgical site occurred 3 weeks after surgery and was treated with negative pressure wound therapy. Physical rehabilitation initiated 5 days after surgery progressed from passive range of motion to the use of an underwater treadmill. Despite initial improvement, acute deterioration occurred 5.5 months after surgery. Repeated CT revealed progression of diskospondylitis, which prompted euthanasia. CLINICAL RELEVANCE Postoperative hind limb paresis and paralysis in this species presented considerable challenges for care and rehabilitation. Patient demeanor, size, and anatomy required development of custom mechanical devices. Despite the inability to eliminate the multidrug-resistant bacterial osteomyelitis that resulted in the death of this aardvark, information gained may benefit treatment of subsequent patients.

Binding and Action of Amino Acid Analogs of Chloramphenicol upon the Bacterial Ribosome

Antibiotic chloramphenicol (CHL) binds with a moderate affinity at the peptidyl transferase center of the bacterial ribosome and inhibits peptide bond formation. As an approach for modifying and potentially improving properties of this inhibitor, we explored ribosome binding and inhibitory activity of a number of amino acid analogs of CHL. The L-histidyl analog binds to the ribosome with the affinity exceeding that of CHL by 10 fold. Several of the newly synthesized analogs were able to inhibit protein synthesis and exhibited the mode of action that was distinct from the action of CHL. However, the inhibitory properties of the semi-synthetic CHL analogs did not correlate with their affinity and in general, the amino acid analogs of CHL were less active inhibitors of translation in comparison with the original antibiotic. The X-ray crystal structures of the Thermus thermophilus 70S ribosome in complex with three semi-synthetic analogs showed that CHL derivatives bind at the peptidyl transferase center, where the aminoacyl moiety of the tested compounds established idiosyncratic interactions with rRNA. Although still fairly inefficient inhibitors of translation, the synthesized compounds represent promising chemical scaffolds that target the peptidyl transferase center of the ribosome and potentially are suitable for further exploration.

Sieving through gut models of colonization resistance

The development of innovative high-throughput genomics and metabolomics technologies has considerably expanded our understanding of the commensal microorganisms residing within the human body, collectively termed the microbiota. In recent years, the microbiota has been reported to have important roles in multiple aspects of human health, pathology and host-pathogen interactions. One function of commensals that has attracted particular interest is their role in protection against pathogens and pathobionts, a concept known as colonization resistance. However, pathogens are also able to sense and exploit the microbiota during infection. Therefore, obtaining a holistic understanding of colonization resistance mechanisms is essential for the development of microbiome-based and microbiome-targeting therapies for humans and animals. Achieving this is dependent on utilizing physiologically relevant animal models. In this Perspective, we discuss the colonization resistance functions of the gut microbiota and sieve through the advantages and limitations of murine models commonly used to study such mechanisms within the context of enteric bacterial infection.

Critical illness and flat batteries

An exaggerated, dysregulated host response to insults such as infection (i.e. sepsis), trauma and ischaemia-reperfusion injury can result in multiple organ dysfunction and death. While the focus of research in this area has largely centred on inflammation and immunity, a crucial missing link is the precise identification of mechanisms at the organ level that cause this physiological-biochemical failure. Any hypothesis must reconcile this functional organ failure with minimal signs of cell death, availability of oxygen, and (often) minimal early local inflammatory cell infiltrate. These failed organs also retain the capacity to usually recover, even those that are poorly regenerative. A metabolic-bioenergetic shutdown, akin to hibernation or aestivation, is the most plausible explanation currently advanced. This shutdown appears driven by a perfect storm of compromised mitochondrial oxidative phosphorylation related to inhibition by excessive inflammatory mediators, direct oxidant stress, a tissue oxygen deficit in the unresuscitated phase, altered hormonal drive, and downregulation of genes encoding mitochondrial proteins. In addition, the efficiency of oxidative phosphorylation may be affected by a substrate shift towards fat metabolism and increased uncoupling. A lack of sufficient ATP provision to fuel normal metabolic processes will drive downregulation of metabolism, and thus cellular functionality. In turn, a decrease in metabolism will provide negative feedback to the mitochondrion, inducing a bioenergetic shutdown. Arguably, these processes may offer protection against a prolonged inflammatory hit by sparing the cell from initiation of death pathways, thereby explaining the lack of significant morphological change. A narrow line may exist between adaptation and maladaptation. This places a considerable challenge on any therapeutic modulation to provide benefit rather than harm.

Structural insights into species-specific features of the ribosome from the human pathogen Mycobacterium tuberculosis

Ribosomes from Mycobacterium tuberculosis (Mtb) possess species-specific ribosomal RNA (rRNA) expansion segments and ribosomal proteins (rProtein). Here, we present the near-atomic structures of the Mtb 50S ribosomal subunit and the complete Mtb 70S ribosome, solved by cryo-electron microscopy. Upon joining of the large and small ribosomal subunits, a 100-nt long expansion segment of the Mtb 23S rRNA, named H54a or the ‘handle’, switches interactions from with rRNA helix H68 and rProtein uL2 to with rProtein bS6, forming a new intersubunit bridge ‘B9’. In Mtb 70S, bridge B9 is mostly maintained, leading to correlated motions among the handle, the L1 stalk and the small subunit in the rotated and non-rotated states. Two new protein densities were discovered near the decoding center and the peptidyl transferase center, respectively. These results provide a structural basis for studying translation in Mtb as well as developing new tuberculosis drugs.

An Update on Fluoroquinolones: The Emergence of a Multisystem Toxicity Syndrome

INTRODUCTION

The FDA (U.S. Food and Drug Administration) recently revised the boxed warning on fluoroquinolones to address serious safety concerns. This action was prompted by a growing number of reports involving patients with a constellation of symptoms now called fluoroquinolone associated disability.

METHODS

Internet and literature searches were performed to identify previous reports of quinolone induced multisystem toxicity syndromes. The 3 terms fluoroquinolone toxicity, quinolone toxicity syndrome and fluoroquinolone associated disability were used to query PubMed® and Google's search engine for available information.

RESULTS

Four primary sources emerged, including a recent FDA review, 2 case series and robust social media platforms. The FDA identified 1,122 fluoroquinolone disability reports from November 1, 1997 to May 30, 2015. A total of 178 cases qualified as fluoroquinolone associated disability after applying inclusion and exclusion criteria. Some estimate that there are as many as 45,000 cases of fluoroquinolone toxicity syndrome in the United States. All sources agree the affected population is generally young (mean age 40s to 50s), previously healthy and predominantly female. The FDA analysis revealed that average symptom duration was 14 months and longest duration was 9 years at the time of the review.

CONCLUSIONS

Fluoroquinolone toxicity syndromes do not affect the majority of exposed patients but are likely underappreciated. As providers seeking to heal and avoid harm to our patients, diligent prescribing practices are paramount, as are early recognition and discontinuation of the antibiotic.

Inhibition of the Rumen Ciliate Entodinium caudatum by Antibiotics

Axenic cultures of free-living aerobic ciliates, such as Tetrahymena thermophila and Paramecium aurelia, have been established and routinely used in laboratory research, greatly facilitating, or enabling characterization of their metabolism, physiology, and ecology. Ruminal protozoa are anaerobic ciliates, and they play important roles in feed digestion and fermentation. Although, repeatedly attempted, no laboratory-maintainable axenic culture of ruminal ciliates has been established. When axenic ciliate cultures are developed, antibiotics are required to eliminate the accompanying bacteria. Ruminal ciliates gradually lose viability upon antibiotic treatments, and the resultant axenic cultures can only last for short periods of time. The objective of this study was to evaluate eight antibiotics that have been evaluated in developing axenic cultures of ruminal ciliates, for their toxicity to Entodinium caudatum, which is the most predominant ruminal ciliate species. Scanning and transmission electron microscopy (TEM) showed that the antibiotics damaged both the cell surface and nuclei of E. caudatum and increased accumulation of intracellular glycogen. Combinations of the three least toxic antibiotics failed to eliminate the bacteria that are present in the E. caudatum culture. The combination of ampicillin, carbenicillin, streptomycin, and oxytetracycline was able to eliminate all the bacteria, but the resultant axenic E. caudatum culture gradually lost viability. Adding the bacterial fraction (live) separated from an untreated E. caudatum culture reversed the viability decline and recovered the growth of the treated E. caudatum culture, whereas feeding nine strains of live bacteria isolated from E. caudatum cells, either individually or in combination, could not. Nutritional and metabolic dependence on its associated bacteria, accompanied with direct and indirect inhibition by antibiotics, makes it difficult to establish an axenic culture of E. caudatum. Monoxenic or polyxenic cultures of E. caudatum could be developed if the essential symbiotic partner(s) can be identified.

Anti-microbial Efficacy of Soursop Leaf Extract (Annona muricata) on Oral Pathogens: An In-vitro Study

INTRODUCTION

Annona muricata also called as Soursop is a, flowering evergreen tree native to Mexico, Cuba, Central America and parts of India. The miracle tree as it is widely known as a natural cancer killer that is 10,000 times stronger than chemotherapy. Based on these miraculous claims, the leaves of these plants were used as an extract at varying concentrations as an antibacterial agent against oral pathogens.

AIM

The aim of the study was to assess antimicrobial efficacy of Soursop leaf extarct (Annona muricata) on Streptococcus mutans, Streptococcus mitis, Porphyromonas gingivalis, Prevotella intermedia and Candida albicans using disc diffusion method.

MATERIALS AND METHODS

Extracts of Annona muricata leaves of concentrations of 1%, 5%, 10%, 15% and 20% were prepared. The anti-microbial efficacy was evaluated using disc diffusion method against Streptococcus mutans, Streptococcus mitis, Porphyromonas gingivalis, Prevotella intermedia and Candida albicans on agar plates.

RESULTS

All concentrations of extracts were effective on the microbiota except for the P. Intermedia. The Soursop extract was highly effective on Candida species, with all concentrations exhibiting bactericidal and fungicidal property. The extracts at different concentration were effective when compared to the gold standard controls and the effect was statistically significant (p<0.05). Data obtained was analysed using one way analysis of variance (ANOVA) and Tukey's post-hoc test.

CONCLUSION

The Soursop extracts were efficient for all test organisms expect P. intermedia. The present study demonstrated the in-vitro efficacy of Soursop was highest against S. mutans followed by C. albicans and least on P. intermedia. Hence, this study proves to an extent that the Soursop extract when used against oral microbiota has sufficient anti-microbial and fungicidal property.

Drug induced mitochondrial dysfunction: Mechanisms and adverse clinical consequences

Several commonly used medications impair mitochondrial function resulting in adverse effects or toxicities. Drug induced mitochondrial dysfunction may be a consequence of increased production of reactive oxygen species, altered mitochondrial permeability transition, impaired mitochondrial respiration, mitochondrial DNA damage or inhibition of beta-oxidation of fatty acids. The clinical manifestation depends on the specific drug and its effect on mitochondria. Given the ubiquitous presence of mitochondria and its central role in cellular metabolism, drug-mitochondrial interactions may manifest clinically as hepatotoxicity, enteropathy, myelosuppression, lipodystrophy syndrome or neuropsychiatric adverse effects, to name a few. The current review focuses on specific drug groups which adversely affect mitochondria, the mechanisms involved and the clinical consequences based on the data available from experimental and clinical studies. Knowledge of these adverse drug-mitochondrial interactions may help the clinicians foresee potential issues in individual patients, prevent adverse drug reactions or alter drug regimens to enhance patient safety.

History of antimicrobial drug discovery: Major classes and health impact

The introduction of antibiotics into clinical practice revolutionized the treatment and management of infectious diseases. Before the introduction of antibiotics, these diseases were the leading cause of morbidity and mortality in human populations. This review presents a brief history of discovery of the main antimicrobial classes (arsphenamines, β-lactams, sulphonamides, polypeptides, aminoglycosides, tetracyclines, amphenicols, lipopeptides, macrolides, oxazolidinones, glycopeptides, streptogramins, ansamycins, quinolones, and lincosamides) that have changed the landscape of contemporary medicine. Given within a historical timeline context, the review discusses how the introduction of certain antimicrobial classes affected the morbidity and mortality rates due to bacterial infectious diseases in human populations. Problems of resistance to antibiotics of different classes are also extensively discussed.