Biology subjects

Miragaia, M.

Publications and source records attributed to Miragaia, M..

4 recordsLinked to original sources

bioRxiv2026

In Vitro Activity of a Novel Metal-Based Antimicrobial against Multidrug-Resistant Klebsiella pneumoniae

Multidrug-resistant (MDR) Klebsiella pneumoniae, classified by the World Health Organization (WHO) as a critical priority pathogen, represents a global health thereat requiring novel antimicrobials urgently. Here we evaluated the in vitro antimicrobial activity of a novel iridium-based compound (OMKP-3), against MDR K. pneumoniae. OMKP-3 exhibited robust antimicrobial activity in M9 minimal media (MIC=6.25{micro}g/mL) and rapid bactericidal effect (MBC=12.5{micro}g/mL) against the tested MDR K. pneumoniae strains. OMKP-3 showed antibiofilm ability and was active against multiple MDR Gram-negative pathogens, including Escherichia coli, Enterobacter cloacae, Pseudomonas aeruginosa and Serratia marcescens (MIC range:6.25-25{micro}g/mL). Importantly, OMKP-3 showed no cytotoxicity against mammalian cells after 24 hours of exposure. When combined with polymyxin B, OMKP-3 acted as an adjuvant, enhancing polymyxin B activity (FIC[≤]0.5). OMKP-3 was less prone to induce high-level resistance in MDR K. pneumoniae compared to ciprofloxacin, and supressed the growth of resistant bacteria at a low and non-cytotoxic concentration (4xMIC). K. pneumoniae strains harboring truncated Ompk35/36 porin genes exhibited higher OMKP-3 MICs, indicating that these porins may serve as an important entry pathway. Spectrometry analysis revealed that OMKP-3 was able to accumulate intracellularly (1.57{micro}g/mL), with minimal Resistance-Nodulation-Division (RND) efflux pump extrusion involvement. Furthermore, analysis of the resistant mutant, harboring a mutation in the outer membrane protein DegS, together with fluorescence microscopy, suggests that OMKP-3 induces membrane-associated damage. No cross-resistance between OMKP-3 and commonly used antibiotics was observed. Collectively, these findings identify OMKP-3 as a promising novel antimicrobial agent against MDR K. pneumoniae, likely acting through an unexplored bacterial target. ImportanceMultidrug-resistant (MDR) Klebsiella pneumoniae is a critical global health threat and is among the leading causes of hospital0hyphenorendash;associated mortality, largely due to the scarcity of effective therapeutic options. Alarmingly, the current antimicrobial pipeline fails to address this issue, relying largely on derivatives of existing scaffolds that offer only short-term clinical benefit due to rapid resistance emergence. Developing antibiotics against Gram-negative pathogens is particularly challenging because of their highly impermeable outer membrane and efficient efflux systems, limiting intracellular drug accumulation. Metal-based antimicrobials emerge as a promising alternative. Our findings showed that OMKP-3, an iridium complex, exhibits potent bactericidal activity against MDR K. pneumoniae without selecting for high-level resistance, suggesting the potential for sustained therapeutic efficacy. Additionally, it demonstrated to accumulate intracellularly with minimal efflux involvement. Together, these features position OMKP-3 as a valuable and underexplored novel antimicrobial strategy for addressing the escalating threat of MDR K. pneumoniae infections.

microbiology↗

bioRxiv2025

Lauric acid: a promising antimicrobial for the selective inhibition of Staphylococcus epidermidis strains associated with infection

Staphylococcus epidermidis, a human skin colonizer and opportunistic pathogen associated with medical device infections, comprises two phylogenetic lineages: A/C (infection and colonization strains) and B (primarily colonization strains). Given the need for antibiotic alternatives, we investigated the antimicrobial activity of skin-derived fatty acids--lauric, palmitoleic, and linoleic acids--against representative strains from both lineages. Fatty acids reduced exponential growth rate and maximum population, with greater effects on the A/C strain. Lauric and palmitoleic acids decreased colony radius in the B strain. Importantly, lauric acid showed no cytotoxicity on a 3D reconstructed human epidermis model. Our findings demonstrate differential susceptibility between lineages, with A/C strains showing greater sensitivity to all tested fatty acids than B strains. These results highlight the potential of lauric acid as a topical formulation for selective inhibition of S. epidermidis growth, offering a promising approach for preventing pathogenic strain proliferation while preserving beneficial skin colonizers.

microbiology↗

bioRxiv2025

Dynamic exometabolomics reveals metabolic adaptations of Staphylococcus epidermidis to pH-mimicking skin and bloodstream

Staphylococcus epidermidis (SE) is a common human skin coloniser, which is often the cause of medical device-associated infections. SE population is composed of two clonal lineages, A/C and B, with distinct pathogenic potential. Although pH is known to change during infection when SE crosses the host skin to access the bloodstream, the impact of this pH alteration on SE pathogenicity is poorly understood. Recognizing how SE deals with pH increments will help designing effective prevention and treatment strategies against SE infections. To investigate the metabolic adaptations of representative A/C and B strains to different pH, we mimicked skin and blood pH conditions (5.5 and 7.4) and followed biomass formation, growth media pH and exometabolites over time. Although both strains share some metabolic patterns, specificities were identified for each strain and pH condition. The B strain was better adapted to use diverse carbon sources and at blood pH has a more active TCA cycle and amino acid catabolism. At blood pH, the B strain depletes formate from the extracellular media, while its extracellular accumulation by the A/C strain could work as a host invasion strategy. For both SE strains, TCA cycle regulation, purine biosynthesis and glutamate uptake could be associated with virulence, particularly biofilm production, especially relevant for ICE25 which is able to produce high adherence biofilm. The uptake and consumption of saccharides follow similar profiles and seem to be pH-regulated by both strains. The dynamic study of SE exometabolome has contributed to understanding the intracellular processes and their relationship with virulence.

microbiology↗

bioRxiv2022

Spontaneous genomic variation as a survival strategy of nosocomial S. haemolyticus

Staphylococcus haemolyticus is one of the most important nosocomial human pathogens frequently isolated in bloodstream and medical devices related infections. This species is notorious for its multidrug resistance and genome plasticity. However, its mechanisms of evolution and adaptation are still poorly explored. In this study we aimed to characterize the strategies of genetic and phenotypic diversity in S. haemolyticus. Here, we analyzed an invasive S. haemolyticus strain, recovered from a bloodstream infection, for genetic and phenotypic stability after serial passage in vitro (>400 generations) in the absence and presence of sub-inhibitory concentrations of a beta-lactam antibiotic. We performed PFGE of the culture and five colonies at seven time points during stability assays were analyzed for beta-lactams susceptibility, hemolysis, mannitol fermentation and biofilm production. We compared their whole genome regarding chromosomal structure, gene content and mutations and preformed phylogenetic analysis based on core SNPs. We observed a high instability in the PFGE profiles at the different time points during serial passage in vitro in the absence of antibiotic. However, no variation was observed in PFGE patterns in the presence of beta-lactams. Analysis of WGS data for individual colonies collected at different time points showed the occurrence of six large-scale genomic deletions within the oriC environ (36 kbp-348 kbp) in the cell populations analyzed, smaller deletions in non-OriC environ region as well as non-synonymous mutations in clinically relevant genes. The regions of deletion and point mutations included genes encoding amino acid and metal transporters, resistance to environmental stress and beta-lactams, virulence, mannitol fermentation, metabolic processes and IS elements. A parallel variation was additionally detected in clinically significant phenotypic traits such as mannitol fermentation, beta-lactams resistance, hemolysis and biofilm formation. All the genetic variants analyzed were closely related in their core genome (13-292 SNPs). Our results suggest that S. haemolyticus populations are composed of subpopulations of genetic and phenotypic variants that might be affected in antibiotic and stress resistance, specific metabolic processes and virulence. The maintenance of subpopulations in different physiological states might be a strategy to adapt rapidly to a stress situation imposed by the host particularly in the hospital environment.

microbiology↗