4 research outputs found
Detection of Heavy Metal Tolerance among different MLSB Resistance Phenotypes of Methicillin-Resistant S. aureus (MRSA)
Methicillin-resistant Staphylococcus aureus (MRSA) strains are widespread globally. Besides their virulence factors, the co-occurrence of antimicrobial and metal resistance has been reported. This study was designed to evaluate the antibiotic resistance and resistance phenotypes, investigate the occurrence of virulence factors, and detect heavy metal tolerance among MRSA strains. Antibiogram profiling was done as recommended by CLSI instructions. Resistance phenotypes were detected by D test, followed by characterization of enzymatic activities and biofilm formation assay. Antibacterial activity of different heavy metals was tested, and predictable synergistic assay was performed. Among MRSA strains collected, high resistance to ampicillin and amoxicillin/clavulanate (100%) and high susceptibility to clindamycin (70%) were obtained. Resistance phenotypes were detected as S, constitutive MLSB, inducible MLSB, and MS by percentages of 10%, 30%, 30% and 30% respectively. Virulence factors like lipolytic (50%) and hemolytic (70%) activity, and biofilm formation ability (100%) were detected. High resistance towards potassium and magnesium was observed. MTC of 500 ppm was detected for all isolates in case of cobalt and iron. In case of zinc and copper, MTC was detected as 500 ppm except for one isolate which was highly resistant, and 500 ppm for all isolates except for two isolates which were highly sensitive respectively. Magnesium in different concentrations (500 and 2000 ppm) showed synergistic activity with erythromycin and clindamycin. Results reveal high heavy metal tolerance among antibiotic resistant MRSA strains, in addition to the presence of virulence factors. Upcoming studies must be focused on the combination of sub-inhibitory concentration of different heavy metals with the available antibiotics
Ancestral Absence of Electron Transport Chains in Patescibacteria and DPANN
Recent discoveries suggest that the candidate superphyla Patescibacteria and DPANN constitute a large fraction of the phylogenetic diversity of Bacteria and Archaea. Their small genomes and limited coding potential have been hypothesized to be ancestral adaptations to obligate symbiotic lifestyles. To test this hypothesis, we performed cell–cell association, genomic, and phylogenetic analyses on 4,829 individual cells of Bacteria and Archaea from 46 globally distributed surface and subsurface field samples. This confirmed the ubiquity and abundance of Patescibacteria and DPANN in subsurface environments, the small size of their genomes and cells, and the divergence of their gene content from other Bacteria and Archaea. Our analyses suggest that most Patescibacteria and DPANN in the studied subsurface environments do not form specific physical associations with other microorganisms. These data also suggest that their unusual genomic features and prevalent auxotrophies may be a result of ancestral, minimal cellular energy transduction mechanisms that lack respiration, thus relying solely on fermentation for energy conservation. © Copyright © 2020 Beam, Becraft, Brown, Schulz, Jarett, Bezuidt, Poulton, Clark, Dunfield, Ravin, Spear, Hedlund, Kormas, Sievert, Elshahed, Barton, Stott, Eisen, Moser, Onstott, Woyke and Stepanauskas