Enhanced platelets aggregation and coagulation of methicillin-resistant Staphylococcus aureus compared to methicillin-sensitive Staphylococcus aureus

Staphylococcus aureus (S. aureus) is well known for its ability to activate platelets and to induce plasma coagulation through different pathways. Enhanced human platelet aggregation and plasma coagulation by methicillin-resistant S. aureus (MRSA) have not been reported. This study aims to investigate platelets and coagulation activities of MRSA strains compared to methicillin-sensitive strains of S. aureus (MSSA). Well-characterized bacterial strains of Coagulase-negative Staphylococci (CoNS) (n = 25), and Coagulase-positive Staphylococci (CoPS) including MRSA (n = 25) and MSSA (n = 25) using phenotype and genotype analysis were compared for their coagulation and aggregation abilities. Isolates were tested for slide and tube coagulase test, mixed with human plasma and investigated for coagulation ability using manual and automated prothrombin time (PT), partial thromboplastin time (PTT), clotting time (CT), and thrombin time (TT) or mixed with human platelet rich plasma (PRP) and analyzed for reduced platelets count (aggregation) and for platelets aggregations using chrono-log aggregometer. MRSA isolates have faster, and stronger tube coagulase test compared to MSSA isolates. MRSA isolates compared to MSSA isolates have significantly reduced manual PT (7.2 ± 1.2 s vs. 10.5 ± 2 s, P < 0.0001), significantly reduced PTT (16.1 ± 1.5 s vs. 23.8 ± 2 s, P < 0.0001), and significantly reduced CT (84 ± 117.2 min vs. 148.3 ± 195 min, P < 0.0001). Similarly, MRSA isolates have significantly reduced PT, PTT, and TT compared to MSSA (P < 0.0001) using an automated coagulation analyzer. MRSA isolates induce a significant decrease in platelet count compared to MSSA (90.3 ± 35.9 vs. 121.1 ± 42.6, P < 0.001). MRSA isolates have significantly increased PRP aggregation compared to MSSA isolates indicated by increased aggregation maximum amplitude, aggregation slope, and area under the curve (P < 0.0001). PT test distinguishes CoPS from CoNS with 100% sensitivity and 98% specificity. Enhanced plasma coagulation and platelet aggregation of MRSA compared to MSSA strains is another virulence factor that increases MRSA protection, decreases antibiotics diffusion, and leads to thrombotic/clotting complications. PT is a useful diagnostic test for distinguishing CoPS from CoNS.