SaeR as a novel target for antivirulence therapy against Staphylococcus aureus.

Staphylococcus aureus is a major human pathogen responsible for a wide range of clinical infections. SaeRS is one of the two-component systems in S. aureus that modulate multiple virulence factors. Although SaeR is required for S. aureus to develop an infection, inhibitors have not been reported. Using an in vivo knockdown method, we demonstrated that SaeR is targetable for the discovery of antivirulence agent. HR3744 was discovered through a high-throughput screening utilizing a GFP-Lux dual reporter system driven by saeP1 promoter. The antivirulence efficacy of HR3744 was tested using Western blot, Quantitative Polymerase Chain Reaction, leucotoxicity, and haemolysis tests. In electrophoresis mobility shift assay, HR3744 inhibited SaeR-DNA probe binding. WaterLOGSY-NMR test showed HR3744 directly interacted with SaeR's DNA-binding domain. When SaeR was deleted, HR3744 lost its antivirulence property, validating the target specificity. Virtual docking and mutagenesis were used to confirm the target's specificity. When Glu159 was changed to Asn, the bacteria developed resistance to HR3744. A structure-activity relationship study revealed that a molecule with a slight modification did not inhibit SaeR, indicating the selectivity of HR3744. Interestingly, we found that SAV13, an analogue of HR3744, was four times more potent than HR3744 and demonstrated identical antivirulence properties and target specificity. In a mouse bacteraemia model, both HR3744 and SAV13 exhibited in vivo effectiveness. Collectively, we identified the first SaeR inhibitor, which exhibited in vitro and in vivo antivirulence properties, and proved that SaeR could be a novel target for developing antivirulence drugs against S. aureus infections.

Predominance of SCCmec types IV and V among biofilm producing device-associated Staphylococcus aureus strains isolated from tertiary care hospitals in Mysuru, India / Predominio de SCCmec tipos IV y V en las cepas de Staphylococcus aureus productoras de biopelículas aisladas de infecciones de dispositivos médicos en hospitales terciarios de Mysuru, India

INTRODUCTION: Device associated infections caused by Staphylococcus aureus in hospitalised patients is a serious healthcare problem. The present study was designed to determine the prevalence of biofilm-producing MRSA in device-associated infections. METHODS: Device-associated S. aureus strains (n=200) obtained from two tertiary care hospitals in Mysuru city, India were screened for biofilm production, antibiotic resistance, Panton-Valentine Leucocidin genes, SCCmec-types, spa-types, and intercellular adhesion (icaAD) dependent and independent genes. The efficacy of antibiotics (linezolid, vancomycin and rifampicin) on biofilms was studied using MTT assay, and the results were correlated with the occurrence of ica-dependent and independent factors. RESULTS: Multidrug resistance was observed in 155 strains (77.5%), and 124 strains (62%) were identified as biofilm producers. Methicillin resistance was identified in 145 strains (72.5%), and SCCmec typing of these isolates revealed high prevalence of type IV and type V. They also showed increased prevalence of pvl gene. icaAD was identified in 65 isolates, with 37 isolates showing both icaAD and ica-independent genes. spa types t852 and t657 were predominantly observed in MRSA isolates. Those isolates that had both ica-dependent and ica-independent genes showed more resistance to the screened antibiotics than the ica-dependent alone. CONCLUSION: This study reports a high prevalence of SCCmec type IV and V in biofilm producing S. aureus strains isolated from device-associated infections. Increased prevalence of pvl in SCCmec types IV and V strains suggests the role of community associated S. aureus in device-associated infections. The simultaneous presence of ica-dependent and independent genes increased the antibiotic resistance in established biofilms. Thus, S. aureus on medical devices is a potential risk for patients

INTRODUCCIÓN: Las infecciones asociadas a dispositivos médicos causadas por Staphylococcus aureus en pacientes hospitalizados son un problema importante. En el presente trabajo se estudia, en cepas de infecciones asociadas a dispositivos médicos, la prevalencia SARM productores de biopelículas y sus tipos SCCmec. MÉTODOS: Se usaron 200 cepas de S. aureus de infecciones de dispositivos médicos obtenidas de 2 hospitales terciarios de Mysuru, India. Se estudió la producción de biopelículas, los genes de la leucocidina de Panton-Valentine, los tipos SCCmec, los tipos de spa y los genes de adhesión intracelular (icaAD) dependientes e independientes. Se estudió la eficacia de linezolid, vancomicina y rifampicina en las biopelículas por un ensayo MTT y los resultados se correlacionaron con la presencia de genes ica dependientes e independientes. RESULTADOS: Ciento veinticuatro cepas (62%) producían biopelículas y se observó multirresistencia antibiótica en 155 (77,5%). Eran resistentes a meticilina 145 cepas (72,5%) y en su tipificación SCCmec se observó alta prevalencia de los tipos IV y V. Estas cepas tenían una prevalencia superior de gen pvl a las no resistentes a meticilina. icaAD se identificó en 65 aislados, de los que 37 mostraron simultáneamente genes ica dependientes e independientes. Los spa tipos t852 y t657 se observaron predominantemente en las cepas de SARM. Los aislados que tenían a la vez genes ica dependientes e ica independientes presentaban mayor resistencia a los antibióticos probados que los que tenían solo ica dependientes. CONCLUSIÓN: El presente estudio informa de una alta prevalencia de SARM de los SCCmec tipos IV y V en cepas de S. aureus productoras de biopelículas. La elevada prevalencia del gen pvl en las cepas de los SCCmec IV y V sugiere el papel de los S. aureus comunitarios en las infecciones asociadas a estos dispositivos. La presencia simultánea de genes ica dependientes e independientes aumenta la resistencia a antibióticos en las biopelículas establecidas. Por todo ello, las cepas de S. aureus en dispositivos médicos son un riesgo potencial para los pacientes