Understanding microbial interactions in infectious diseases to improve diagnostic and therapeutic success

The human microbiome project changed the fundamental understanding of how microorganism interact with the human host, wherein synergistic and antagonistic interactions can be observed. Classical biomedical research focused on understanding how bacterial-host interactions could influence disease progression. Yet less explored, bacterial-bacterial interactions can also contribute to disease progression and to therapeutic failure. Examples of microbial interactions leading to disease include cystic fibrosis, dental caries or bacterial vaginosis. While the first two are currently easily diagnosed, bacterial vaginosis presents an increased challenge, mainly because its etiology is yet fully understood. Bacterial vaginosis is the most frequent cause of vaginal discomfort worldwide, and is also linked to serious medical conditions, including preterm birth and increased risk of acquisition of HIV. The bacterial interactions occurring during bacterial vaginosis are thought to be responsible for therapeutic failure, leading to very high recurrence rates. Despite the worldwide prevalence and the significant economic cost, researchers havent yet identified bacterial vaginosis etiology, but current consensus is that a polymicrobial biofilm is involved. During this talk, I will highlight two projects wherein my research group is aiming to (i) provide a better picture of how these bacterial species interactions enhance protection against current and/or potential novel antimicrobial agents or (ii) using the presence of key bacterial interactions as a mean to develop robust molecular diagnosis methods.info:eu-repo/semantics/publishedVersio

Synergistic effects of combinations of antibiotics on coagulase negative staphylococcal (CoNS) biofilms

Background. Previous studies examining synergistic effects of antibiotics against CoNS biofilms often relied on drug concentrations higher than the peak serum (PS) concentration, as determined by MIC assays, therefore having little clinical applicability. Other studies investigated synergistic effects of a wide range of antibiotics, however many are not routinely used in a clinical setting. Dicloxacillin is the major antibiotic used in Portugal to treat staphylococci infections, and we evaluated the synergistic effect of antibiotics with different mechanisms of action combined with dicloxacillin and other cell wall synthesis inhibitors. Methods. We used combinations of 5 antibiotic agents (cefazolin, vancomycin, dicloxacillin, tetracycline and rifampicin) at the PS concentration of each agent, and evaluated the killing rate over a 24 h period using biofilms made by 10 CoNS clinical isolates. Results from all of the assays were compared using ANOVA. Results. Among all of the combinations tested there was an increase in the killing rate of the antibiotics when compared to the killing rates when only one antibiotic was used. However, only the combination of dicloxacillin with rifampicin resulted in a true synergistic effect for most CoNS strains. When tetracycline was used in combination with any other antibiotic, a decrease in the killing rate was obtained. Conclusions. Our results indicate that dicloxacillin could be useful against CoNS biofilms when combined with a small amount of rifampicin (10 μg/ml). Antibiotics highly effective against planktonic cells, like vancomycin, were minimally effective against cells in biofilms, even after adding more antibiotics with distinct mechanisms of action. Also, except for dicloxacillin, adding more antibiotics to the biofilm did not result in an increase in killing efficiency, and there were even antagonistic in some instances. Screening for synergistic effects of different combinations of antibiotics might be a useful tool to determine a therapeutic approach to infections involving CoNS biofilms

BV and non-BV associated Gardnerella vaginalis establish similar synergistic interactions with other BV-associated microorganisms in dual-species biofilms

Dual-species biofilm formation between Gardnerella vaginalis strains isolated from women with or without bacterial vaginosis (BV) and other 24 BV-associated microorganisms support that the key difference in virulence potential between BV-negative and BV-positive G. vaginalis strains seems not to be related with biofilm maturation.FCT Strategic Project of UID/BIO/04469/2013 unit and the project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462

Profiling antimicrobial tolerance by planktonic, biofilms and biofilm-released cells of Staphylococcus epidermidis

Microbiotec'17 - Congress of Microbiology and Biotechnology 2017Background Worldwide, Staphylococcus epidermidis has been recognized as leading cause of several clinically relevant infections, especially in neonates and immunocompromised patients. Its ability to form biofilms, particularly in the surface of indwelling medical devices, is the primary cause of healthcar e associated infections. On the last stage of biofilm lifecycle - disassembly, cells are released to the surrounding environment, being able to spread the infection and cause systemic diseases. These cells may be defined as biofilm-released cells (Brc). It is well known that planktonic cells (PLA) are more susceptible to antibiotics than biofilm cells (BF). So far, little is known regarding Brc tolerance to antibiotics. The main goal of this work was to compare the susceptibility of Brc, PLA and BF of S. epidermidis clinical isolates, to 10 distinct antibiotics. Method Brc, PLA and BF cells were obtained using a previously developed method (França et al, 2016), with different S. epidermidis clinical isolates. The susceptibility of all populations of S. epidermidis 9142 to peak serum concentrations (PSC) of Dicloxacillin, Imipenem, Teicoplanin, Vancomycin, Ciprofloxacin, Rifampicin, Erythromycin, Gentamicin, Linezolid and Tetracycline was assessed after 2 hours of incubation, by CFU counting. Furthermore, 11 additional isolates were studied upon incubation with PSC of Vancomycin, to determine whether the results are transversal to distinct isolates among the same species. Results & Conclusions Our results demonstrated that Brc present a distinct tolerance profile when exposed to some antibiotics. While studying isolate 9142, Brc had a distinct tolerance phenotype with 6 out of 10 antibiotics. Regarding vancomycin assays, Brc presented an intermediate susceptibility to vancomycin when compared with other po pulations with 11 out of 12 isolates. Thus, this study outlines the impact of Brc on pathogenesis by demonstrating that the metabolic state and cell physiology of Brc present a distinct antibiotic tolerance profile, and might influence antimicrobial therapies against Staphylococcal infections(FCT) by the strategic project of UID/BIO/04469/2013 and by BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by European Regional Development Fund under the scope of Norte2020info:eu-repo/semantics/publishedVersio