Staphylococcus aureus is the causative agent of a diverse array of acute and chronic infections, and some these infections, including infective endocarditis, joint infections, and medical device-associated bloodstream infections, depend upon its capacity to form tenacious biofilms on surfaces. Inserted medical devices such as intravenous catheters, pacemakers, and artificial heart valves save lives, but unfortunately, they can also serve as a substrate on which S. aureus can form a biofilm, attributing S. aureus as a leading cause of medical device-related infections. The major aim of this work was take compounds to which S. aureus would be exposed during infection and to investigate their effects on its capacity to form a biofilm. More specifically, the project investigated the effects of serum, and thereafter of catheter lock solutions on biofilm formation by S. aureus. Pre-coating polystyrene with serum is frequently used as a method to augment biofilm formation. The effect of pre-coating with serum is due to the deposition of extracellular matrix components onto the polystyrene, which are then recognized by MSCRAMMs. We therefore hypothesized that the major component of blood, serum, would induce biofilm formation. Surprisingly, serum actually inhibited biofilm formation. The inhibitory activity was due to a small molecular weight, heat-stable, non-proteinaceous component/s of serum. Serum-mediated inhibition of biofilm formation may represent a previously uncharacterized aspect of host innate immunity that targets the expression of a key bacterial virulence factor: the ability to establish a resistant biofilm. Metal ion chelators like sodium citrate are frequently chosen to lock intravenous catheters because they are regarded as potent inhibitors of bacterial biofilm formation and viability. We found that, while chelating compounds abolished biofilm formation in most strains of S. aureus, they actually augmented the phenotype in a subset of strains. We investigated the molecular basis of this phenomenon. Deletion and complementation analysis and thereafter antibody based inhibition assays confirmed a functional role for the surface adhesin clumping factor B as the causative determinant associated with the increased biofilm phenotype. Finally, we investigated the regulation of clumping factor B-mediated biofilm formation and the basis for the strain dependence. Regulation was determined to occur via two novel post-translational networks- one affecting ClfB activity, mediated by Ca2+ binding to the EF-Hand domain, and the other affecting protein stability, mediated by the enzymatic activity of the metalloprotease-aureolysin. Polymorphisms within the aureolysin gene sequence, between strains, was identified as the basis for some strains forming robust biofilms within chelated media versus other than do not exhibit this phenotype.

Resistência hidráulica é altamente prevalente em cateteres venosos centrais de longa permanência. Selos de heparina são comumente utilizados para manter evitar o problema, mas mostram pouca efetividade. O objetivo do presente estudo foi avaliar a efetividade e segurança de dois selos quanto à redução de ocorrência de incidência de baixo fluxo. Setenta e cinco pacientes com doença renal crônica no estágio 5D em hemodiálise de alta eficiência no Centro Integrado de Nefrologia (Guarulhos, Brasil) foram randomizados na proporção de 1:1:1 para receber selo contendo a combinação de minociclina 3 mg/ml com o anticoagulante/quelante EDTA 30 mg/ml (M-EDTA), heparina 1.000 U/mL (Heparina) ou citrato trissódico 30% (Citrato) por 15 semanas. Sessenta e oito pacrticipantes terminaram o estudo no qual ambos participantes e investigadores foram cegos quanto à alocação do tratamento. O desfecho primátio de efetividade foi ocorrência de resistência hidráulica e o desfecho secundário de segurança foi ocorrência de reações adversas a selos. A incidência de resistência hidráulica foi significantemente maior em cateteres selados com Heparina (18/23) comparado com os selos Citrato (4/22) e M-EDTA (2/23) (p< 0.001). O estudo clínico sugere que o Citrato e M-EDTA mantem a patência de cateteres melhor que a heparina 1.000 UI/ml, sendo altamente custo-efetivos em comparação com heparina 1.000 UI/ml. Ainda, o Citrato pode ser a melhor opção de selo por não se associar com resistência antimicrobiana a longo prazo. / Hydraulic Resistance is highly prevalent among long-term central venous catheters. Heparin catheter lock solutions are commonly used to maintain catheter patency, however this problem remains high. The purpose of the CLOCK Trial was to evaluate two catheter lock solutions as to their effectiveness and safety. Seventy-five CKD 5D patients on high-efficiency hemodialysis at the Integrated Centre of Nephrology (Guarulhos, Brazil) were randomized 1:1:1 to receive a lock solution combining minocycline 3 mg/ml with the anticoagulant/chelation agent EDTA 30 mg/ml (M-EDTA) or heparin 1,000 IU/ml (Heparin) or trisodium citrate 30% (Citrate) versus Heparin for 15 weeks. A total of 68 patients completed the trial in which both investigators and patients were blinded to treatment allocation. The primary end-point was the occurrence of hydraulic resistance and secondary safety end-point was adverse drug reactions related to the lock solutions. The incidence of hydraulic resistance was significantly higher among patients on Heparin (18/23) compared to Citrate (4/22) and M-EDTA (2/23) lock solutions, (p< 0.001). The trial suggests Citrate and M-EDTA may preserve catheter patency better than Heparin and they may show higher cost-effectiveness when compared to heparin. Citrate may be a better option due the lack of association with longterm antimicrobial resistance.

Resistência hidráulica é altamente prevalente em cateteres venosos centrais de longa permanência. Selos de heparina são comumente utilizados para manter evitar o problema, mas mostram pouca efetividade. O objetivo do presente estudo foi avaliar a efetividade e segurança de dois selos quanto à redução de ocorrência de incidência de baixo fluxo. Setenta e cinco pacientes com doença renal crônica no estágio 5D em hemodiálise de alta eficiência no Centro Integrado de Nefrologia (Guarulhos, Brasil) foram randomizados na proporção de 1:1:1 para receber selo contendo a combinação de minociclina 3 mg/ml com o anticoagulante/quelante EDTA 30 mg/ml (M-EDTA), heparina 1.000 U/mL (Heparina) ou citrato trissódico 30% (Citrato) por 15 semanas. Sessenta e oito pacrticipantes terminaram o estudo no qual ambos participantes e investigadores foram cegos quanto à alocação do tratamento. O desfecho primátio de efetividade foi ocorrência de resistência hidráulica e o desfecho secundário de segurança foi ocorrência de reações adversas a selos. A incidência de resistência hidráulica foi significantemente maior em cateteres selados com Heparina (18/23) comparado com os selos Citrato (4/22) e M-EDTA (2/23) (p< 0.001). O estudo clínico sugere que o Citrato e M-EDTA mantem a patência de cateteres melhor que a heparina 1.000 UI/ml, sendo altamente custo-efetivos em comparação com heparina 1.000 UI/ml. Ainda, o Citrato pode ser a melhor opção de selo por não se associar com resistência antimicrobiana a longo prazo. / Hydraulic Resistance is highly prevalent among long-term central venous catheters. Heparin catheter lock solutions are commonly used to maintain catheter patency, however this problem remains high. The purpose of the CLOCK Trial was to evaluate two catheter lock solutions as to their effectiveness and safety. Seventy-five CKD 5D patients on high-efficiency hemodialysis at the Integrated Centre of Nephrology (Guarulhos, Brazil) were randomized 1:1:1 to receive a lock solution combining minocycline 3 mg/ml with the anticoagulant/chelation agent EDTA 30 mg/ml (M-EDTA) or heparin 1,000 IU/ml (Heparin) or trisodium citrate 30% (Citrate) versus Heparin for 15 weeks. A total of 68 patients completed the trial in which both investigators and patients were blinded to treatment allocation. The primary end-point was the occurrence of hydraulic resistance and secondary safety end-point was adverse drug reactions related to the lock solutions. The incidence of hydraulic resistance was significantly higher among patients on Heparin (18/23) compared to Citrate (4/22) and M-EDTA (2/23) lock solutions, (p< 0.001). The trial suggests Citrate and M-EDTA may preserve catheter patency better than Heparin and they may show higher cost-effectiveness when compared to heparin. Citrate may be a better option due the lack of association with longterm antimicrobial resistance.