Narrow-spectrum Antimicrobials Research Articles

Comparison of fidaxomicin, thuricin CD, vancomycin and nisin highlights the narrow spectrum nature of thuricin CD

ABSTRACT Vancomycin and metronidazole are commonly used treatments for Clostridioides difficile infection (CDI). However, these antibiotics have been associated with high levels of relapse in patients. Fidaxomicin is a new treatment for CDI that is described as a narrow spectrum antibiotic that is minimally active on the commensal bacteria of the gut microbiome. The aim of this study was to compare the effect of fidaxomicin on the human gut microbiome with a number of narrow (thuricin CD) and broad spectrum (vancomycin and nisin) antimicrobials. The spectrum of activity of each antimicrobial was tested against 47 bacterial strains by well-diffusion assay. Minimum inhibitory concentrations (MICs) were calculated against a select number of these strains. Further, a pooled fecal slurry of 6 donors was prepared and incubated for 24 h with 100 µM of each antimicrobial in a mini-fermentation system together with a no-treatment control. Fidaxomicin, vancomycin, and nisin were active against most gram positive bacteria tested in vitro, although fidaxomicin and vancomycin produced larger zones of inhibition compared to nisin. In contrast, the antimicrobial activity of thuricin CD was specific to C. difficile and some Bacillus spp. The MICs showed similar results. Thuricin CD exhibited low MICs (<3.1 µg/mL) for C. difficile and Bacillus firmus, whereas fidaxomicin, vancomycin, and nisin demonstrated lower MICs for all other strains tested when compared to thuricin CD. The narrow spectrum of thuricin CD was also observed in the gut model system. We conclude that the spectrum of activity of fidaxomicin is comparable to that of the broad-spectrum antibiotic vancomycin in vitro and the broad spectrum bacteriocin nisin in a complex community.

Long-Term Co-Circulation of Host-Specialist and Host-Generalist Lineages of Group B Streptococcus in Brazilian Dairy Cattle with Heterogeneous Antimicrobial Resistance Profiles.

Group B Streptococcus (GBS) is a major cause of contagious bovine mastitis (CBM) in Brazil. The GBS population is composed of host-generalist and host-specialist lineages, which may differ in antimicrobial resistance (AMR) and zoonotic potential, and the surveillance of bovine GBS is crucial to developing effective CBM control and prevention measures. Here, we investigated bovine GBS isolates (n = 156) collected in Brazil between 1987 and 2021 using phenotypic testing and whole-genome sequencing to uncover the molecular epidemiology of bovine GBS. Clonal complex (CC) 61/67 was the predominant clade in the 20th century; however, it was replaced by CC91, with which it shares a most common recent ancestor, in the 21st century, despite the higher prevalence of AMR in CC61/67 than in CC91, and high selection pressure for AMR from indiscriminate antimicrobial use in the Brazilian dairy industry. CC103 also emerged as a dominant CC in the 21st century, and a considerable proportion of herds had two or more GBS strains, suggesting poor biosecurity and within-herd evolution due to the chronic nature of CBM problems. The majority of bovine GBS belonged to serotype Ia or III, which was strongly correlated with CCs. Ninety-three isolates were resistant to tetracycline (≥8 μg/mL; tetO = 57, tetM = 34 or both = 2) and forty-four were resistant to erythromycin (2.0 to >4 μg/mL; ermA = 1, ermB = 38, mechanism unidentified n = 5). Only three isolates were non-susceptible to penicillin (≥8.0 μg/mL), providing opportunities for improved antimicrobial stewardship through the use of narrow-spectrum antimicrobials for the treatment of dairy cattle. The common bovine GBS clades detected in this study have rarely been reported in humans, suggesting limited risk of interspecies transmission of GBS in Brazil. This study provides new data to support improvements to CBM and AMR control, bovine GBS vaccine design, and the management of public health risks posed by bovine GBS in Brazil.

Knowledge, attitudes, and practices on antimicrobial use and antimicrobial resistance among poultry practitioner veterinarians.

Antimicrobial resistance (AMR) poses a serious global threat to human and animal health. In the context of antimicrobial usage (AMU) in livestock production, veterinarians are key stakeholders. However, there is a lack of comprehensive situational analysis regarding the current Knowledge, Attitudes, and Practices (KAP) among veterinarians concerning AMU and AMR in poultry production in Nepal. The primary objective of this study was to evaluate the situation of AMU and KAP regarding AMU and AMR of among poultry practitioner veterinarians in Nepal. A total of 327 respondents from 56 districts across seven provinces participated. Demographic information and AMU situation were collected and analyzed using descriptive statistics, and factors affecting KAP on AMU and AMR were performed using logistic regression analysis. Nearly half of veterinarians (49.2%) were from Bagmati, followed by Lumbini (16.5%) and Gandaki (8.9%) provinces. Most of the respondents (85.0%) identified themselves as male with a mean age of 31.9 ± 7.8 years, with a range of 24-74 years. A large proportion of veterinarians held a master's degree (43.8%). Regarding reasons for AMR, 51.1% of them attributed it to the irrational use of antimicrobials. Other identified reasons for AMR, including over-the-counter sales (27.8%), low-dose administration (12.3%), and low-quality antimicrobials (6.7%). Based on antibiotic prescription rates, most veterinarians (50.8%) prescribed antimicrobials at a rate of 20-40%, while 25.9% prescribed at a rate of less than 20.0 and 18.9% at a rate of 40-60%. Approximately 89.0% of veterinarians agreed that vaccination could reduce the use of antimicrobials in poultry, and 75.6% preferred narrow-spectrum antimicrobials than broad-spectrum antimicrobials. A combination of broad-spectrum antimicrobials such as colistin with amoxicillin, gentamicin, tylosin, and tetracycline was commonly used in poultry production. In logistic regression analysis, it was observed that veterinarians aged 45-60 years demonstrated significantly higher levels of knowledge concerning AMU and AMR (p = 0.02) compared to those in the 24-30 age group. This study indicates that the need for robust regulatory mechanisms in veterinary drug administration and increased awareness among veterinarians to address the AMR issue livestock production.

In Vitro Influence of Specific Bacteroidales Strains on Gut and Liver Health Related to Metabolic Dysfunction-Associated Fatty Liver Disease.

Metabolic dysfunction-associated fatty liver disease (MAFLD) has become a major health risk and a serious worldwide issue. MAFLD typically arises from aberrant lipid metabolism, insulin resistance, oxidative stress, and inflammation. However, subjacent causes are multifactorial. The gut has been proposed as a major factor in health and disease, and over the last decade, bacterial strains with potentially beneficial effects on the host have been identified. In vitro cell models have been commonly used as an early step before in vivo drug assessment and can confer complementary advantages in gut and liver health research. In this study, several selected strains of the order Bacteroidales were used in a three-cell line in vitro analysis (HT-29, Caco-2, and HepG2 cell lines) to investigate their potential as new-generation probiotics and microbiota therapeutics. Antimicrobial activity, a potentially useful trait, was studied, and the results showed that Bacteroidales can be a source of either wide- or narrow-spectrum antimicrobials targeting other closely related strains. Moreover, Bacteroides sp. 4_1_36 induced a significant decrease in gut permeability, as evidenced by the high TEER values in the Caco-2 monolayer assay, as well as a reduction in free fatty acid accumulation and improved fatty acid clearance in a steatosis HepG2 model. These results suggest that Bacteroidales may spearhead the next generation of probiotics to prevent or diminish MAFLD.

Metabolic modeling predicts unique drug targets in Borrelia burgdorferi.

Lyme disease is often treated using long courses of antibiotics, which can cause side effects for patients and risks the evolution of antimicrobial resistance. Narrow-spectrum antimicrobials would reduce these risks, but their development has been slow because the Lyme disease bacterium, Borrelia burgdorferi, is difficult to work with in the laboratory. To accelerate the drug discovery pipeline, we developed a computational model of B. burgdorferi's metabolism and used it to predict essential enzymatic reactions whose inhibition prevented growth in silico. These predictions were validated using small-molecule enzyme inhibitors, several of which were shown to have specific activity against B. burgdorferi. Although the specific compounds used are not suitable for clinical use, we aim to use them as lead compounds to develop optimized drugs targeting the pathways discovered here.

"AMP plus": Immunostimulant-Inspired Design Based on Chemotactic Motif-(PhHAhPH)n.

Ability to stimulate antimicrobial immunity has proven to be a useful therapeutic strategy in treating infections, especially in the face of increasing antibiotic resistance. Natural antimicrobial peptides (AMPs) exhibiting immunomodulatory functions normally encompass complex activities, which make it difficult to optimize their therapeutic benefits. Here, a chemotactic motif was harnessed as a template to design a series of AMPs with immunostimulatory activities plus bacteria-killing activities ("AMP plus"). An amphipathic peptide ((PhHAhPH)n) was employed to improve the antimicrobial impact and expand the therapeutic potential of the chemotactic motif that lacked obvious bacteria-killing properties. A total of 18 peptides were designed and evaluated for their structure-activity relationships. Among the designed, KWH2 (1) potently killed bacteria and exhibited a narrow antimicrobial spectrum against Gram-negative bacteria and (2) activated macrophages (i.e., inducing Ca2+ influx, cell migration, and reactive oxygen species production) as a macrophage chemoattractant. Membrane permeabilization is the major antimicrobial mechanism of KWH2. Furthermore, the mouse subcutaneous abscess model supported the dual immunomodulatory and antimicrobial potential of KWH2 in vivo. The above results confirmed the efficiency of KWH2 in treating bacterial infection and provided a viable approach to develop immunomodulatory antimicrobial materials with desired properties.

Novel leaderless bacteriocin geobacillin 6 from thermophilic bacterium Parageobacillus thermoglucosidasius.

Bacterial resistance to conventional antibiotics has urged us to develop alternative strategies against bacterial pathogens. Moreover, a demand for food products containing no chemical preservatives has led us to search for new alternative technologies for food preservation. Bacteriocins - ribosomally synthesized antimicrobial peptides - have been proposed as a new alternative to conventional antibiotics or chemicals for food preservation. This study describes biosynthesis and characterization of a novel leaderless bacteriocin, geobacillin 6, which was identified in the thermophilic bacterium Parageobacillus thermoglucosidasius. Its amino acid sequence shows low similarity to other bacteriocins and it is the first leaderless-type bacteriocin identified in thermophilic bacteria. Based on structure assessment, the bacteriocin forms a multi-helix bundle. Geobacillin 6 exhibits a relatively narrow antimicrobial spectrum, it is active in the μM range and against Gram-positive bacteria, mostly thermophilic species closely related to the producer strain. Bacteriocin demonstrates stability over pH 3-11 and is highly thermostable, retaining 100% of its activity after incubation at 95°C for 6 h. Geobacillin 6 has potential in the food industry and biotechnological processes where contamination with thermophilic bacteria is undesirable.

Avidumicin, a novel cyclic bacteriocin, produced by Cutibacterium avidum shows anti-Cutibacterium acnes activity.

The prevalence of antimicrobial-resistant Cutibacterium acnes in acne patients has increased owing to inappropriate antimicrobial use. Commensal skin bacteria may play an important role in maintaining the balance of the skin microbiome by producing antimicrobial substances. Inhibition of Cu. acnes overgrowth can prevent the development and exacerbation of acne vulgaris. Here, we evaluated skin bacteria with anti-Cu. acnes activity. Growth inhibition activity against Cu. acnes was tested using 122 strains isolated from the skin of healthy volunteers and acne patients. Comparative genomic analysis of the bacterium with or without anti-Cu. acnes activity was conducted. The anti-Cu. acnes activity was confirmed by cloning an identified gene cluster and chemically synthesized peptides. Cu. avidum ATCC25577 and 89.7% of the Cu. avidum clinical isolates (26/29 strains) inhibited Cu. acnes growth. The growth inhibition activity was also found against other Cutibacterium, Lactiplantibacillus, and Corynebacterium species, but not against Staphylococcus species. The genome sequence of Cu. avidum showed a gene cluster encoding a novel bacteriocin named avidumicin. The precursor protein encoded by avdA undergoes post-translational modifications, supposedly becoming a circular bacteriocin. The anti-Cu. acnes activity of avidumicin was confirmed by Lactococcus lactis MG1363 carrying avdA. The C-terminal region of the avidumicin may be essential for anti-Cu. acnes activity. A commensal skin bacterium, Cu. avidum, producing avidumicin has anti-Cu. acnes activity. Therefore, avidumicin is a novel cyclic bacteriocin with a narrow antimicrobial spectrum. These findings suggest that Cu. avidum and avidumicin represent potential alternative agents in antimicrobial therapy for acne vulgaris.

Antimicrobial function of yeast against pathogenic and spoilage microorganisms via either antagonism or encapsulation: A review.

Contaminations of pathogenic and spoilage microbes on foods are threatening food safety and quality, highlighting the importance of developing antimicrobial agents. According to different working mechanisms, the antimicrobial activities of yeast-based agents were summarized from two aspects: antagonism and encapsulation. Antagonistic yeasts are usually applied as biocontrol agents for the preservation of fruits and vegetables via inactivating spoilage microbes, usually phytopathogens. This review systematically summarized various species of antagonistic yeasts, potential combinations to improve the antimicrobial efficiency, and the antagonistic mechanisms. The wide applications of the antagonistic yeasts are significantly limited by undesirable antimicrobial efficiency, poor environmental resistance, and a narrow antimicrobial spectrum. Another strategy for achieving effective antimicrobial activity is to encapsulate various chemical antimicrobial agents into a yeast-based carrier that has been previously inactivated. This is accomplished by immersing the dead yeast cells with porous structure in an antimicrobial suspension and applying high vacuum pressure to allow the agents to diffuse inside the yeast cells. Typical antimicrobial agents encapsulated in the yeast carriers have been reviewed, including chlorine-based biocides, antimicrobial essential oils, and photosensitizers. Benefiting from the existence of the inactive yeast carrier, the antimicrobial efficiencies and functional durability of the encapsulated antimicrobial agents, such as chlorine-based agents, essential oils, and photosensitizers, are significantly improved compared with the unencapsulated ones.

3-Amino-Substituted Analogues of Fusidic Acid as Membrane-Active Antibacterial Compounds.

Fusidic acid (FA) is an antibiotic with high activity against Staphylococcus aureus; it has been used in clinical practice since the 1960s. However, the narrow antimicrobial spectrum of FA limits its application in the treatment of bacterial infections. In this regard, this work aims both at the study of the antimicrobial effect of a number of FA amines and at the identification of their potential biological targets. In this way, FA analogues containing aliphatic and aromatic amino groups and biogenic polyamine, spermine and spermidine, moieties at the C-3 atom, were synthesized (20 examples). Pyrazinecarboxamide-substituted analogues exhibit a high antibacterial activity against S. aureus (MRSA) with MIC ≤ 0.25 μg/mL. Spermine and spermidine derivatives, along with activity against S. aureus, also inhibit the growth and reproduction of Gram-negative bacteria Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa, and have a high fungicidal effect against Candida albicans and Cryptococcus neoformans. The study of the membrane activity demonstrated that the spermidine- and spermine-containing compounds are able to immerse into membranes and disorder the lipidsleading to a detergent effect. Moreover, spermine-based compounds are also able to form ion-permeable pores in the lipid bilayers mimicking the bacterial membranes. Using molecular docking, inhibition of the protein synthesis elongation factor EF-G was proposed, and polyamine substituents were shown to make the greatest contribution to the stability of the complexes of fusidic acid derivatives with biological targets. This suggests that the antibacterial effect of the obtained compounds may be associated with both membrane activity and inhibition of the elongation factor EF-G.

Therapeutic beta-lactam dosages and broad-spectrum antibiotics are associated with reductions in microbial richness and diversity in persons with cystic fibrosis

Persons with cystic fibrosis (PwCF) suffer from pulmonary exacerbations (PEx) related in part to lung infection. While higher microbial diversity is associated with higher lung function, the data on the impact of short-term antibiotics on changes in microbial diversity is conflicting. Further, Prevotella secretes beta-lactamases, which may influence recovery of lung function. We hypothesize that sub-therapeutic and broad spectrum antibiotic exposure leads to decreasing microbial diversity. Our secondary aim was to evaluate the concerted association of beta-lactam pharmacokinetics (PK), antibiotic spectrum, microbial diversity, and antibiotic resistance on lung function recovery using a pathway analysis. This was a retrospective observational study of persons with CF treated with IV antibiotics for PEx between 2016 and 2020 at Children’s National Hospital; respiratory samples and clinical information were collected at hospital admission for PEx (E), end of antibiotic treatment (T), and follow-up (F). Metagenomic sequencing was performed; PathoScope 2.0 and AmrPlusPlus were used for taxonomic assignment of sequences to bacteria and antibiotic resistance genes (ARGs). M/W Pharm was used for PK modeling. Comparison of categorical and continuous variables and pathway analysis were performed in STATA. Twenty-two PwCF experienced 43 PEx. The study cohort had a mean age of 14.6 years. Only 12/43 beta-lactam courses had therapeutic PK, and 18/43 were broad spectrum. A larger decrease in richness between E and T was seen in the therapeutic PK group (sufficient − 20.1 vs. insufficient − 1.59, p = 0.025) and those receiving broad spectrum antibiotics (broad − 14.5 vs. narrow − 2.8, p = 0.030). We did not detect differences in the increase in percent predicted forced expiratory volume in one second (ppFEV1) at end of treatment compared to PEx based on beta-lactam PK (sufficient 13.6% vs. insufficient 15.1%) or antibiotic spectrum (broad 11.5% vs. narrow 16.6%). While both therapeutic beta-lactam PK and broad-spectrum antibiotics decreased richness between PEx and the end of treatment, we did not detect longstanding changes in alpha diversity or an association with superior recovery of lung function compared with subtherapeutic PK and narrow spectrum antimicrobials.

Ligand and structure-based approaches for the exploration of structure-activity relationships of fusidic acid derivatives as antibacterial agents.

Introduction: Fusidic acid (FA) has been widely applied in the clinical prevention and treatment of bacterial infections. Nonetheless, its clinical application has been limited due to its narrow antimicrobial spectrum and some side effects. Purpose: Therefore, it is necessary to explore the structure-activity relationships of FA derivatives as antibacterial agents to develop novel ones possessing a broad antimicrobial spectrum. Methods and result: First, a pharmacophore model was established on the nineteen FA derivatives with remarkable antibacterial activities reported in previous studies. The common structural characteristics of the pharmacophore emerging from the FA derivatives were determined as those of six hydrophobic centers, two atom centers of the hydrogen bond acceptor, and a negative electron center around the C-21 field. Then, seven FA derivatives have been designed according to the reported structure-activity relationships and the pharmacophore characteristics. The designed FA derivatives were mapped on the pharmacophore model, and the Qfit values of all FA derivatives were over 50 and FA-8 possessed the highest value of 82.66. The molecular docking studies of the partial target compounds were conducted with the elongation factor G (EF-G) of S. aureus. Furthermore, the designed FA derivatives have been prepared and their antibacterial activities were evaluated by the inhibition zone test and the minimum inhibitory concentration (MIC) test. The derivative FA-7 with a chlorine group as the substituent group at C-25 of FA displayed the best antibacterial property with an MIC of 3.125µM. Subsequently, 3D-QSAR was carried on all the derivatives by using the CoMSIA mode of SYBYL-X 2.0. Conclusion: Hence, a computer-aided drug design model was developed for FA, which can be further used to optimize FA derivatives as highly potent antibacterial agents.

Trend of oral antimicrobial use after removal of broad-spectrum antimicrobials from the formulary at a pediatric primary emergency medical center

IntroductionWhile the effects of the Japanese action plan formulated in 2016 have gradually appeared, the appropriate use of antimicrobials in outpatient settings is still important. We conducted a previous study to recommend appropriate antimicrobial use via monthly newsletters at a pediatric primary emergency medical center (PEC). As a result, the rate of inappropriate prescription of oral third-generation cephalosporins (3GCs) decreased by 67.2%. This decrease prompted our institution to change the antimicrobials adopted from 3GCs to first-generation cephalosporins. There have been no reports on the prescribing trend of narrow-spectrum antimicrobials after the discontinuation of 3GCs in pediatric PECs. MethodsWe conducted a single-center, observational study at one pediatric PEC between April 2020 and March 2022. We recorded the total number of patients and oral antimicrobial prescriptions, diagnoses, and descriptions of the electronic health records and evaluated the prescription trends and appropriateness of antimicrobial use after removal of cefditoren-pivoxil and fosfomycin from the formulary. ResultsThe total number of patients was 22,744 during the study period, and antimicrobials were prescribed to 496 (2.2%) patients. The proportion of amoxicillin prescriptions among total antimicrobials was high (53.4%). For each prescription, 85 of 259 prescriptions (32.8%) for amoxicillin, 161 of 185 prescriptions (87.0%) for cephalexin, and 17 of 43 prescriptions (39.5%) for clarithromycin were judged to be appropriate. ConclusionWe suggest that after the removal of broad-spectrum antimicrobials and achieving a reduction in the prescription rate of oral antimicrobials, it is necessary to evaluate whether narrow-spectrum antimicrobials are used properly in pediatric PECs.

Effects of penicillin V on the faecal microbiota in patients with pharyngotonsillitis-an observational study.

The intestinal microbiota functions as a reservoir of antibiotic resistance. To evaluate penicillin V (phenoxymethylpenicillin) effects on the faecal microbiota with focus on beta-lactam resistance. We included 31 primary care patients with group A streptococcal pharyngotonsillitis treated with penicillin V for 5 (800 mg × 4) or 10 days (1000 mg × 3). Twenty-nine patients contributed with three faecal swab samples each. The faecal specimens were collected at the start of penicillin V treatment, after the last dose and at follow-up 7-9 days after completed treatment. Samples were inoculated semiquantitatively on selective screening agar plates to study beta-lactam resistance, species shifts among Enterobacterales and enterococci, and colonization with Candida spp. and Clostridioides difficile. Representative colonies were identified using MALDI-TOF. Results were analysed by non-parametric statistical methods. An increase in the proportion of patients colonized with ampicillin-resistant Enterobacterales, from 52% to 86% (P = 0.007), and Enterobacterales with decreased susceptibility to third-generation cephalosporins, from 32% to 52% (P = 0.034), was observed between the first and second samples. This increase was no longer significant at follow-up. New colonization with ampicillin-resistant Enterobacterales species and non-Enterobacterales Gram-negative species was observed, and persisted at follow-up. Following treatment with penicillin V, we observed decreased susceptibility to ampicillin and third-generation cephalosporins, and prolonged colonization with non-Escherichia coli Gram-negative species. These findings challenge the perception that penicillin V has limited ecological effect on the intestinal microbiota, and emphasizes the importance of avoiding even narrow-spectrum antimicrobials when possible.

Incidence and Susceptibility Patterns of Urine Bacterial Flora in Young Saudi Females

It has been established that the urinary tract is not sterile; however, research related to the study of urinary bacteria is limited. This study aimed to investigate the frequency and patterns of resistance of normal urinary aerobic bacterial flora and clean catch midstream urine specimens collected from 120 young healthy females and cultured. Bacterial identification and antimicrobial susceptibility were performed using the Biomérieux VITEK® 2 automated system. Participants who had undergone antimicrobial treatment within one month were not included. The incidence of positive bacterial cultures was 54.2%, of which 21.5% were polymicrobial. Approximately 107 bacterial isolates that encompass 12 genera and 27 species that were predominated by gram-positive bacteria (72%) were cultivated. Staphylococcaceae (46.1%) and Enterobacteriaceae (17.8%) were the most frequent isolates among gram-positive and gram-negative bacteria, respectively, of which 36 species have been identified as β-lactamase producers. The top four frequently isolated bacteria were Micrococcus spp. (16%), Staphylococcus haemolyticus (13.2%), Staphylococcus aureus (10%), and Klebsiella pneumoniae (10%). Twenty-two bacterial species were subjected to antimicrobial susceptibility testing using broad- and narrow-spectrum antibiotics and antimicrobials, which showed the lowest susceptibility rate against gram-positive bacteria, followed by erythromycin and azithromycin. A lower antimicrobial susceptibility potential among gram-negative bacteria was observed against ampicillin, followed by piperacillin and cefotaxime. Our findings emphasize the importance of highlighting urine bacterial flora in studies, especially those related to susceptibility patterns, by employing more advanced culture methods as multiple drug-resistant bacteria were isolated.

Comparative study on antimicrobial activity of mono-rhamnolipid and di-rhamnolipid and exploration of cost-effective antimicrobial agents for agricultural applications

BackgroundChemical pesticides have defects in crop diseases control, such as narrow antimicrobial spectrum, chemicals residue risk and harm to farmland ecosystem. Antimicrobial agents from microbial sources are highly interested in agriculture. Studies showed that rhamnolipid biosurfactants possessed certain antimicrobial activity. The structural differences in rhamnolipid inevitably affect their activities. But the antimicrobial effect of mono-rhamnolipid and di-rhamnolipid is unknown. Rhamnolipid with unique structure can be produced using specific microbial cell factory.ResultsDifferent types of rhamnolipid were produced from different Pseudomonas aeruginosa strains. Rha-C10-C10 and Rha-Rha-C10-C10 were the main homologues in the separated mono-rhamnolipid and di-rhamnolipid, respectively. Both mono-rhamnolipid and di-rhamnolipid exhibited certain antimicrobial activity against the tested microbial strains, especially the fungi and Gram-positive bacteria. But mono-rhamnolipid was superior to di-rhamnolipid, with inhibition zone diameters larger than 25 mm and inhibition rate higher than 90%. The IC50 values of mono-rhamnolipid were lower than 5 mg/L against the tested bacterium and fungus, whereas the IC50 values of di-rhamnolipid were ranged from 10 mg/L to 20 mg/L. Mono-rhamnolipid stimulated the tested strains to generate higher level of intracellular ROS. Mono-rhamnolipid exhibited better antimicrobial activity to the potential agricultural pathogens, such as Alternaria alternata, Pantoea agglomerans and Cladosporium sp. The mono-rhamnolipid crude extract of strain P. aeruginosa SGΔrhlC can replace the separated mono-rhamnolipid. After 50 times dilution, the fermentation broth of the mono-rhamnolipid producing strain SGΔrhlC exhibited equal antimicrobial effect to mono-rhamnolipid (200 mg/L). Prospects of mono-rhamnolipid were also discussed for antimicrobial applications in agriculture.ConclusionsThis work discovered that mono-rhamnolipid was superior to di-rhamnolipid on antimicrobial activity for agricultural applications. Mono-rhamnolipid is an excellent candidate for agricultural biocontrol. The knockout strain P. aeruginosa SGΔrhlC is an excellent microbial cell factory for high producing mono-rhamnolipid. Its mono-rhamnolipid crude extract and its diluted fermentation broth are cost-effective antimicrobial agents. This work provided new insights to develop green and efficient antimicrobial agents for agricultural applications.

Non-Antibiotic Antimony-Based Antimicrobials.

A series of the eight novel organoantimony(V) cyanoximates of Sb(C6H5)4L composition was synthesized using the high-yield heterogeneous metathesis reaction between solid AgL (or TlL) and Sb(C6H5)4Br in CH3CN at room temperature. Cyanoximes L were specially selected from a large group of 48 known compounds of this subclass of oximes on the basis of their water solubility and history of prior biological activity. The synthesized compounds are well soluble in organic solvents and were studied using a variety of conventional spectroscopic and physical methods. The crystal structures of all reported organometallic compounds were determined and revealed the formation of the distorted trigonal bipyramidal environment of the Sb atom and monodentate axial binding of acido-ligands via the O atom of the oxime group. The compounds are thermally stable in the solid state and in solution molecular compounds. For the first time, this specially designed series of organoantimony(V) compounds is investigated as potential non-antibiotic antimicrobial agents against three bacterial and two fungal human pathogens known for their increasing antimicrobial resistance. Bacterial pathogens included Gram-negative Escherichia coli and Pseudomonas aeruginosa, and Gram-positive Staphylococcus aureus. Fungal pathogens included Cryptococcus neoformans and Candida albicans. The cyanoximates alone showed no antimicrobial impact, and the incorporation of the SbPh4 group enabled the antimicrobial effect. Overall, the new antimony compounds showed a strong potential as both broad- and narrow-spectrum antimicrobials against selected bacterial and fundal pathogens and provide insights for further synthetic modifications of the compounds to increase their activities.

Lactic Acid Bacteria and Bacteriocins: Novel Biotechnological Approach for Biopreservation of Meat and Meat Products.

Meat and meat products are perishable in nature, and easily susceptible to microbial contamination and chemical deterioration. This not only results in an increased risk to health of consumers, but also causes economic loss to the meat industry. Some microorganisms of the lactic acid bacteria (LAB) group and their ribosomal-synthesized antimicrobial peptides—especially bacteriocins—can be used as a natural preservative, and an alternative to chemical preservatives in meat industry. Purified or partially purified bacteriocins can be used as a food additive or incorporated in active packaging, while bacteriocin-producing cells could be added as starter or protective cultures for fermented meats. Large-scale applications of bacteriocins are limited, however, mainly due to the narrow antimicrobial spectrum and varying stability in different food matrixes. To overcome these limitations, bioengineering and biotechnological techniques are being employed to combine two or more classes of bacteriocins and develop novel bacteriocins with high efficacy. These approaches, in combination with hurdle concepts (active packaging), provide adequate safety by reducing the pathogenicity of spoilage microorganisms, improving sensory characteristics (e.g., desirable flavor, texture, aroma) and enhancing the shelf life of meat-based products. In this review, the biosynthesis of different classes of LAB bacteriocins, their mechanism of action and their role in the preservation of meats and meat products are reviewed.

Chronic diseases and variations in rates of antimicrobial use in the community: a population-based analysis of linked administrative data in Quebec, Canada, 2002-2017.

Background:Chronic diseases may increase risk of infection and complications from infections; fear of these risks may lower clinicians’ tolerance threshold for the prescription of antimicrobials, thus increasing the risk of selecting resistant bacteria. We sought to describe rates of antimicrobial use in Quebec and measure the association between chronic diseases and utilization rates.Methods:Using the Quebec Integrated Chronic Disease Surveillance System, we analyzed data of people covered by the public drug insurance plan in 2002–2017. Based on delivered prescriptions, we described trends in antimicrobial use in the population, and per category of select chronic diseases (i.e., none, respiratory, cardiovascular, diabetes, mental disorder), according to age group (0–17 yr, 18–64 yr and ≥ 65 yr). We computed ratios of extended-to-narrow–spectrum antimicrobials in 2014–2017. We used robust Poisson regression to quantify the association between chronic diseases and rates of antimicrobial use among children and adults (≥ 18 yr).Results:Between 2002 and 2017, 4 231 724 prescriptions were received over 6 653 473 individual-years among children; 1 367 492 (20.6%) individual-years had at least 1 chronic disease. Among adults aged 18–64 years, 13 365 577 prescriptions were received over 24 935 592 individual-years; 9 533 493 (38.2%) individual-years had at least 1 chronic disease. Among adults 65 years or older, 11 689 365 prescriptions were received over 15 927 342 individual-years; 12 743 588 (80.0%) individual-years had least 1 chronic disease. Antimicrobial use decreased among children, remained stable among younger adults and increased among older adults. Trends were consistent across chronic disease categories in children and older adults. In 2014–2017, 19.9% of children, 39.1% of younger adults and 79.7% of older adults had at least 1 chronic disease. Claims for extended-spectrum antimicrobials were frequent in all age and chronic disease groups, relative to narrow-spectrum antimicrobials (ratios from 3.1:1 to 14.6:1). Antimicrobial use was higher among people with respiratory diseases (adults: relative rate [RR] 2.09, 95% confidence interval [CI] 2.07–2.10; children: RR 1.62, 95% CI 1.59–1.65), mental health diagnoses (adults: RR 1.48, 95% CI 1.46–1.49; children: RR 1.22, 95% 1.20–1.24), diabetes (adults: RR 1.40, 95% CI 1.28–1.41; children: RR 2.02, 95% CI 1.58–2.57) and cardiovascular diseases (adults: RR 1.31, 95% CI 1.30–1.32), compared with those with none of the studied chronic diseases.Interpretation:During the study period, large proportions of antimicrobial prescriptions were for people with chronic diseases, across the age spectrum. Interventions to reduce antimicrobial use should be tailored for these populations.

Recipient Cell Factors Influence Interbacterial Competition Mediated by Two Distinct Burkholderia dolosa Contact-Dependent Growth Inhibition Systems.

ABSTRACTContact-dependent growth inhibition (CDI) systems mediate interbacterial antagonism between Gram-negative bacteria by delivering the toxic portion of a large surface protein (termed BcpA in Burkholderia species) to the cytoplasm of neighboring bacteria. Translocation of the antibacterial polypeptide into recipient cells requires specific recipient outer and inner membrane proteins, but the identity of these factors outside several model organisms is unknown. To identify genes involved in CDI susceptibility in the Burkholderia cepacia complex member Burkholderia dolosa, a transposon mutagenesis selection approach was used to enrich for mutants resistant to BcpA-1 or BcpA-2. Subsequent analysis showed that candidate regulatory genes contributed modestly to recipient cell susceptibility to B. dolosa CDI. However, most candidate deletion mutants did not show the same phenotypes as the corresponding transposon mutants. Whole-genome resequencing revealed that these transposon mutants also contained unique mutations within a three gene locus (wabO, BDAG_01006, and BDAG_01005) encoding predicted lipopolysaccharide (LPS) biosynthesis enzymes. B. dolosa wabO, BDAG_01006, or BDAG_01005 mutants were resistant to CDI and produced LPS with altered core oligosaccharide and O-antigen. Although BcpA-1 and BcpA-2 are dissimilar and expected to utilize different outer membrane receptors, intoxication by both proteins was similarly impacted by LPS changes. Together, these findings suggest that alterations in cellular regulation may indirectly impact the efficiency of CDI-mediated competition and demonstrate that LPS is required for intoxication by two distinct B. dolosa BcpA proteins.IMPORTANCEContact-dependent growth inhibition (CDI) system proteins, produced by many Gram-negative bacteria, are narrow spectrum antimicrobials that inhibit the growth of closely related neighboring bacteria. Here, we use the opportunistic pathogen Burkholderia dolosa to identify genes required for intoxication by two distinct CDI system proteins. Our findings suggest that B. dolosa recipient cells targeted by CDI systems are only intoxicated if they produce full-length lipopolysaccharide. Understanding the mechanisms underlying antagonistic interbacterial interactions may contribute to future therapeutic development.