Investigating bacteriophages targeting the opportunistic pathogen Acinetobacter baumannii

The multi-drug resistance of the opportunistic pathogen Acinetobacter baumannii is of growing concern, with many clinical isolates proving to be resistant to last resort as well as front line antibiotic treatments. The use of bacteriophages is an attractive alternative to controlling and treating this emerging nosocomial pathogen. In this study, we have investigated bacteriophages collected from hospital wastewater in Thailand and we have explored their activity against clinical isolates of A. baumannii. Bacteriophage vB_AbaM_PhT2 showed 28% host range against 150 multidrug resistant (MDR) isolates and whole genome sequencing did not detect any known virulence factors or antibiotic resistance genes. Purified vB_AbaM_PhT2 samples had endotoxin levels below those recommended for preclinical trials and were not shown to be directly cytotoxic to human cell lines in vitro. The treatment of human brain and bladder cell lines grown in the presence of A. baumannii with this bacteriophage released significantly less lactate dehydrogenase compared to samples with no bacteriophage treatment, indicating that vB_AbaM_PhT2 can protect from A. baumannii induced cellular damage. Our results have also indicated that there is synergy between this bacteriophage and the end line antibiotic colistin. We therefore propose bacteriophage vB_AbaM_PhT2 as a good candidate for future research and for its potential development into a surface antimicrobial for use in hospitals. View Full-Tex

The Pleiotropic CymR Regulator of Staphylococcus aureus Plays an Important Role in Virulence and Stress Response

We have characterized a novel pleiotropic role for CymR, the master regulator of cysteine metabolism. We show here that CymR plays an important role both in stress response and virulence of Staphylococcus aureus. Genes involved in detoxification processes, including oxidative stress response and metal ion homeostasis, were differentially expressed in a ΔcymR mutant. Deletion of cymR resulted in increased sensitivity to hydrogen peroxide-, disulfide-, tellurite- and copper-induced stresses. Estimation of metabolite pools suggests that this heightened sensitivity could be the result of profound metabolic changes in the ΔcymR mutant, with an increase in the intracellular cysteine pool and hydrogen sulfide formation. Since resistance to oxidative stress within the host organism is important for pathogen survival, we investigated the role of CymR during the infectious process. Our results indicate that the deletion of cymR promotes survival of S. aureus inside macrophages, whereas virulence of the ΔcymR mutant is highly impaired in mice. These data indicate that CymR plays a major role in virulence and adaptation of S. aureus for survival within the host

Bacterial laccases: some recent advances and applications

Laccases belong to the large family of multi-copper oxidases (MCOs) that couple the one-electron oxidation of substrates with the four-electron reduction of molecular oxygen to water. Because of their high relative non-specific oxidation capacity particularly on phenols and aromatic amines as well as the lack of requirement for expensive organic cofactors, they have found application in a large number of biotechnological fields. The vast majority of studies and applications were performed using fungal laccases, but bacterial laccases show interesting properties such as optimal temperature above 50 °C, optimal pH at the neutral to alkaline range, thermal and chemical stability and increased salt tolerance. Additionally, bacterial systems benefit from a wide range of molecular biology tools that facilitates their engineering and achievement of high yields of protein production and set-up of cost-effective bioprocesses. In this review we will provide up-to-date information on the distribution and putative physiological role of bacterial laccases and highlight their distinctive structural and biochemical properties, discuss the key role of copper in the biochemical properties, discuss thermostability determinants and, finally, review biotechnological applications with a focus on catalytic mechanisms on phenolics and aromatic amines.info:eu-repo/semantics/publishedVersio

Genome analysis of secondary metabolitebiosynthetic gene clusters of Photorhabdus akhurstii subsp. akhurstii and its antibacterial activity against antibiotic-resistant bacteria

Xenorhabdus and Photorhabdus can produce a variety of secondary metabolites with broad spectrum bioactivity against microorganisms. We investigated the antibacterial activity of Xenorhabdus and Photorhabdus against 15 antibiotic-resistant bacteria strains. Photorhabdus extracts had strong inhibitory the growth of Methicillin-resistant Staphylococcus aureus (MRSA) by disk diffusion. The P. akhurstii s subsp. akhurstii (bNN168.5_TH) extract showed lower minimum inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC). The interaction between either P. akhurstii subsp. akhurstii (bNN141.3_TH) or P. akhurstii subsp. akhurstii (bNN168.5_TH) or P. hainanensis (bNN163.3_TH) extract in combination with oxacillin determined by checkerboard assay exhibited partially synergistic interaction with fractional inhibitory concentration index (FICI) of 0.53. Time-killing assay for P. akhurstii subsp. akhurstii (bNN168.5_TH) extract against S. aureus strain PB36 significantly decreased cell viability from 105 CFU/ml to 103 CFU/ml within 30 min (P < 0.001, t-test). Transmission electron microscopic investigation elucidated that the bNN168.5_TH extract caused treated S. aureus strain PB36 (MRSA) cell membrane damage. The biosynthetic gene clusters of the bNN168.5_TH contained non-ribosomal peptide synthetase cluster (NRPS), hybrid NRPS-type l polyketide synthase (PKS) and siderophore, which identified potentially interesting bioactive products: xenematide, luminmide, xenortide A-D, luminmycin A, putrebactin/avaroferrin and rhizomide A-C. This study demonstrates that bNN168.5_TH showed antibacterial activity by disrupting bacterial cytoplasmic membrane and the draft genome provided insights into the classes of bioactive products. This also provides a potential approach in developing a novel antibacterial agent

A preliminary screening of potentially antimalarial plants against Plasmodium falciparum in vitro

Plasmodium is a blood protozoan parasite that is responsible for malaria. To date, Plasmodium falciparum has shown multi-drug resistance, particularly in Thailand, Myanmar and Malaysia. The aim of the study is to screen the plant extracts that can effectively inhibit P. falciparum 3D7, a common lab strain malaria parasite. Nine plants were collected and processed through maceration using hexane, chloroform and ethanol, resulting in 24 crude plant extracts. Of these, extracts from Artabotrys crassifolius, Pericampylus glacus and Leuconotis eugeniifolia showed promising antiplasmodial activities at IC50 of 15.32 to 39.75 mu g/mL in a modified schizont maturation assay. Further studies are warranted to explore its efficacies and lead compounds of these three plant extracts for the development of antiplasmodial drugs