<Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> biofilms subjected to phage phiIBB-PF7A

Background  

Pseudomonas fluorescens is an important food spoilage organism, usually found in the form of biofilms. Bacterial biofilms are inherently resistant to a variety of antimicrobial agents, therefore alternative methods to biofilm control, such as bacteriophages (phages) have been suggested. Phage behavior on biofilms is still poorly investigated and needs further understanding. Here we describe the application of phage ϕIBB-PF7, a newly isolated phage, to control P. fluorescens biofilms. The biofilms were formed under static or dynamic conditions and with or without renewal of medium.     

Antimicrobial peptides effectively kill a broad spectrum of <Emphasis Type="Italic">Listeria monocytogenes</Emphasis> and <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> strains independently of origin,sub-type,or virulence factor expression

Background  

Host defense peptides (HDPs), or antimicrobial peptides (AMPs), are important components of the innate immune system that bacterial pathogens must overcome to establish an infection and HDPs have been suggested as novel antimicrobial therapeutics in treatment of infectious diseases. Hence it is important to determine the natural variation in susceptibility to HDPs to ensure a successful use in clinical treatment regimes.     

Robustness analysis of culturing perturbations on <Emphasis Type="Italic">Escherichia coli</Emphasis> colony biofilm beta-lactam and aminoglycoside antibiotic tolerance

Background  

Biofilms are ubiquitous. For instance, the majority of medical infections are thought to involve biofilms. However even after decades of investigation, the in vivo efficacy of many antimicrobial strategies is still debated suggesting there is a need for better understanding of biofilm antimicrobial tolerances. The current study's goal is to characterize the robustness of biofilm antibiotic tolerance to medically and industrially relevant culturing perturbations. By definition, robust systems will return similar, predictable responses when perturbed while non-robust systems will return very different and potentially unpredictable responses. The predictability of an antibiotic tolerance response is essential to developing, testing, and employing antimicrobial strategies.     

The lantibiotic mersacidin is a strong inducer of the cell wall stress response of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

Background  

The lantibiotic mersacidin is an antimicrobial peptide of 20 amino acids that is ribosomally produced by Bacillus sp. strain HIL Y-85,54728. Mersacidin acts by complexing the sugar phosphate head group of the peptidoglycan precursor lipid II, thereby inhibiting the transglycosylation reaction of peptidoglycan biosynthesis.     

<Emphasis Type="Italic">Streptomyces coelicolor</Emphasis> increases the production of undecylprodigiosin when interacted with <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

Purpose of work  

Undecylprodigiosin has antimicrobial, immunosuppressive and anticancer properties. Pure cultures of Streptomyces coelicolor produce only low concentrations of undecylprodigiosin. We have therefore sought to increase this by interacting the cells with a bacterium.     

Anti‐Campylobacter and resistance‐modifying activity of Alpinia katsumadai seed extracts

Aims

We tested extracts from Alpinia katsumadai seeds for anti‐Campylobacter activity and investigated the roles of the CmeABC and CmeDEF efflux pumps in Campylobacter resistance to these natural phenolics. Additionally, we investigated an A. katsumadai ethanolic extract (AlpE) and other plant extracts as putative efflux pump inhibitors on Campylobacter isolates and mutants in efflux pump genes.

Methods and Results

AlpE showed antimicrobial activity against sensitive and multidrug‐resistant Campylobacter isolates. CmeB inactivation resulted in the greatest reduction in resistance, while cmeF and cmeR mutations produced only moderate effects on minimal inhibitory concentrations (MICs). The chemical efflux pump inhibitors additionally reduced MICs in isolates and mutants, confirming that active efflux is an important mechanism in resistance to AlpE, with additional contributions of other efflux systems. A notable decrease in resistance to tested antimicrobials in the presence of subinhibitory concentrations of AlpE confirms its modifying activity in Campylobacter spp.

Conclusions

AlpE is important anti‐Campylobacter source of antimicrobial compounds with resistance‐modifying activity. At least two of the efflux systems are involved in the resistance to A. katsumadai antimicrobial seed extracts.

Significance and Impact of the Study

This is the first report of antimicrobial and resistance‐modifying activity of AlpE from A. katsumadai seeds, demonstrating its potential in the control of Campylobacter in the food chain.     

Vv-AMP1, a ripening induced peptide from <Emphasis Type="Italic">Vitis vinifera</Emphasis> shows strong antifungal activity

Background  

Latest research shows that small antimicrobial peptides play a role in the innate defense system of plants. These peptides typically contribute to preformed defense by developing protective barriers around germinating seeds or between different tissue layers within plant organs. The encoding genes could also be upregulated by abiotic and biotic stimuli during active defense processes. The peptides display a broad spectrum of antimicrobial activities. Their potent anti-pathogenic characteristics have ensured that they are promising targets in the medical and agricultural biotechnology sectors.     

Crystal structures of <Emphasis Type="Italic">Burkholderia cenocepacia</Emphasis> dihydropteroate synthase in the apo-form and complexed with the product 7,8-dihydropteroate

Background  

The enzyme dihydropteroate synthase (DHPS) participates in the de novo synthesis of folate cofactors by catalyzing the formation of 7,8-dihydropteroate from condensation of p-aminobenzoic acid with 6-hydroxymethyl-7,8-dihydropteroate pyrophosphate. DHPS is absent from humans, who acquire folates from diet, and has been validated as an antimicrobial therapeutic target by chemical and genetic means. The bacterium Burkholderia cenocepacia is an opportunistic pathogen and an infective agent of cystic fibrosis patients. The organism is highly resistant to antibiotics and there is a recognized need for the identification of new drugs against Burkholderia and related Gram-negative pathogens. Our characterization of the DHPS active site and interactions with the enzyme product are designed to underpin early stage drug discovery.     

Carvacrol and <Emphasis Type="Italic">p</Emphasis>-cymene inactivate <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7 in apple juice

Background  

Outbreaks of food poisoning associated with drinking un-pasteurised apple juice contaminated with enterohaemorrhagic Escherichia coli O157:H7 are a cause of serious illness and occasionally death. Whilst a well-established heat process (pasteurisation) will readily eliminate the pathogen, some consumers are demanding more fresh-like foods that have not been subjected to processing methods that are perceived as severe and may lead to loss of flavour and vitamins. Therefore, alternative methods are being investigated to replace pasteurisation and improve the safety of minimally-processed juices. The addition of natural antimicrobial substances such as the phenolic substances carvacrol and p-cymene (derived from the essential oils of herbs and spices) provides a potential new route to assure safety and extend the shelf-life of raw fruit juices.     

Nucleotide diversity and linkage disequilibrium in 11 expressed resistance candidate genes in <Emphasis Type="Italic">Lolium perenne</Emphasis>

Background  

Association analysis is an alternative way for QTL mapping in ryegrass. So far, knowledge on nucleotide diversity and linkage disequilibrium in ryegrass is lacking, which is essential for the efficiency of association analyses.     

Contribution of SecDF to <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>resistance and expression of virulence factors

Background  

SecDF is an accessory factor of the conserved Sec protein translocation machinery and belongs to the resistance-nodulation-cell division (RND) family of multidrug exporters. SecDF has been shown in Escherichia coli and Bacillus subtilis to be involved in the export of proteins. RND proteins can mediate resistance against various substances and might be of relevance in antimicrobial therapy. The role of RND proteins in Staphylococcus aureus has not yet been determined.     

Genetic elements associated with antimicrobial resistance in enteropathogenic <Emphasis Type="Italic">Escherichia coli</Emphasis> (EPEC) from Brazil

Background  

We recently observed an association of resistance with a certain enteropathogenic Escherichia coli (EPEC) serotypes and identified a conjugative plasmid, similar to plasmid pED208, that was conserved among archival O111:H2/NM and O119:H2 strains of diverse geographical origin. In this study, we sought to determine the prevalence and distribution of this plasmid among a collection of EPEC isolates from Brazil, as well as to study the susceptibilities of these isolates to antimicrobial agents.     

<Emphasis Type="Italic">Escherichia coli</Emphasis> genes that reduce the lethal effects of stress

Background  

The continuing emergence of antimicrobial resistance requires the development of new compounds and/or enhancers of existing compounds. Genes that protect against the lethal effects of antibiotic stress are potential targets of enhancers. To distinguish such genes from those involved in drug uptake and efflux, a new susceptibility screen is required.     

Evaluation of Petrifilm™ Select <Emphasis Type="Italic">E. coli</Emphasis> Count Plate medium to discriminate antimicrobial resistant <Emphasis Type="Italic">Escherichia coli</Emphasis>

Background  

Screening and enumeration of antimicrobial resistant Escherichia coli directly from samples is needed to identify emerging resistant clones and obtain quantitative data for risk assessment. Aim of this study was to evaluate the performance of 3M™ Petrifilm™ Select E. coli Count Plate (SEC plate) supplemented with antimicrobials to discriminate antimicrobial-resistant and non-resistant E. coli.     

Antimicrobial resistance and virulence factors in <Emphasis Type="Italic">Escherichia coli</Emphasis> from swedish dairy calves

Background  

In Sweden, knowledge about the role of enteropathogenic Escherichia coli in neonatal calf diarrhea and the occurrence of antimicrobial resistance in E. coli from young calves is largely unknown. This has therapeutic concern and such knowledge is also required for prudent use of antimicrobials.     

Fed-batch process for the psychrotolerant marine bacterium <Emphasis Type="Italic">Pseudoalteromonas haloplanktis</Emphasis>

Background  

Pseudoalteromonas haloplanktis is a cold-adapted γ-proteobacterium isolated from Antarctic sea ice. It is characterized by remarkably high growth rates at low temperatures. P. haloplanktis is one of the model organisms of cold-adapted bacteria and has been suggested as an alternative host for the soluble overproduction of heterologous proteins which tend to form inclusion bodies in established expression hosts. Despite the progress in establishing P. haloplanktis as an alternative expression host the cell densities obtained with this organism, which is unable to use glucose as a carbon source, are still low. Here we present the first fed-batch cultivation strategy for this auspicious alternative expression host.     

A combination of silver nanoparticles and visible blue light enhances the antibacterial efficacy of ineffective antibiotics against methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (MRSA)

Background

Silver nanoparticles (AgNPs) are potential antimicrobials agents, which can be considered as an alternative to antibiotics for the treatment of infections caused by multi-drug resistant bacteria. The antimicrobial effects of double and triple combinations of AgNPs, visible blue light, and the conventional antibiotics amoxicillin, azithromycin, clarithromycin, linezolid, and vancomycin, against ten clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were investigated.

Methods

The antimicrobial activity of AgNPs, applied in combination with blue light, against selected isolates of MRSA was investigated at 1/2–1/128 of its minimal inhibitory concentration (MIC) in 24-well plates. The wells were exposed to blue light source at 460 nm and 250 mW for 1 h using a photon emitting diode. Samples were taken at different time intervals, and viable bacterial counts were determined. The double combinations of AgNPs and each of the antibiotics were assessed by the checkerboard method. The killing assay was used to test possible synergistic effects when blue light was further combined to AgNPs and each antibiotic at a time against selected isolates of MRSA.

Results

The bactericidal activity of AgNPs, at sub-MIC, and blue light was significantly (p < 0.001) enhanced when both agents were applied in combination compared to each agent alone. Similarly, synergistic interactions were observed when AgNPs were combined with amoxicillin, azithromycin, clarithromycin or linezolid in 30–40 % of the double combinations with no observed antagonistic interaction against the tested isolates. Combination of the AgNPs with vancomycin did not result in enhanced killing against all isolates tested. The antimicrobial activity against MRSA isolates was significantly enhanced in triple combinations of AgNPs, blue light and antibiotic, compared to treatments involving one or two agents. The bactericidal activities were highest when azithromycin or clarithromycin was included in the triple therapy compared to the other antibiotics tested.

Conclusions

A new strategy can be used to combat serious infections caused by MRSA by combining AgNPs, blue light, and antibiotics. This triple therapy may include antibiotics, which have been proven to be ineffective against MRSA. The suggested approach would be useful to face the fast-growing drug-resistance with the slow development of new antimicrobial agents, and to preserve last resort antibiotics such as vancomycin.

     

The structure of <Emphasis Type="Italic">Mycobacteria</Emphasis> 2<Emphasis Type="Italic">C</Emphasis>-methyl-D-erythritol-2,4-cyclodiphosphate synthase,an essential enzyme,provides a platform for drug discovery

Background  

The prevalence of tuberculosis, the prolonged and expensive treatment that this disease requires and an increase in drug resistance indicate an urgent need for new treatments. The 1-deoxy-D-xylulose 5-phosphate pathway of isoprenoid precursor biosynthesis is an attractive chemotherapeutic target because it occurs in many pathogens, including Mycobacterium tuberculosis, and is absent from humans. To underpin future drug development it is important to assess which enzymes in this biosynthetic pathway are essential in the actual pathogens and to characterize them.     

The proline-rich peptide Bac7(1-35) reduces mortality from <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> in a mouse model of infection

Background  

Bac7 is a proline-rich peptide with a potent in vitro antimicrobial activity against Gram-negative bacteria. Here we investigated its activity in biological fluids and in vivo using a mouse model of S. typhimurium infection.     

Differential activity of innate defense antimicrobial peptides against <Emphasis Type="Italic">Nocardia</Emphasis> species

Background  

Members of the genus Nocardia are ubiquitous environmental saprophytes capable to cause human pulmonary, disseminated and cutaneous nocardiosis or bovine mastitis. Innate immunity appears to play an important role in early defense against Nocardia species. To elucidate the contribution of antimicrobial peptides (AMPs) in innate defense against Nocardia, the activity of human α-defensins human neutrophil peptides (HNPs) 1-3, human β-defensin (hBD)-3 and cathelicidin LL-37 as well as bovine β-defensins lingual and tracheal antimicrobial peptides (LAP, TAP) and bovine neutrophil-derived indolicidin against four important Nocardia species was investigated.