Impact of Hyperglycemia on Streptococcus pneumoniae Virulence: Insights into Capsular Dynamics and Clinical...

Hyperglycemia, a diabetic condition, profoundly affects the pathogenicity of Streptococcus pneumoniae ( S. pneumoniae ), a leading etiologic pathogen of pneumonia. This review addresses a systematic understanding of how hyperglycemia affects the pathogenicity of S. pneumoniae , especially by immune dysfunction, cytokine dysregulation, and oxidative stress. Although the length of the capsular polysaccharide (CPS) chain plays a role in immune evasion and survival of bacteria, hyperglycemia also affects host immune responses, leading to increased severity of infection in diabetic patients. CPS length polymorphism, whose wzy gene regulation in the majority of instances is under strict control, avoids immunity by phagocytosis and complement inhibition mechanisms. Metabolic dysregulation secondary to hyperglycemia caused by diabetes with activation of the stress pathways and modifications of the availability of nucleotide sugars potentially results in aberrant CPS polymerization with subsequent augmentation of capsule elongation lengths. These changes facilitate the survival of the bacterium, increase immune dysregulation, and aggravate disease severity in diabetes. Determination of the interaction among hyperglycemia, immune dysfunction, and pneumococcal virulence factors positions the demand for focused therapy to reduce infection risks. This review facilitates awareness of bacterial pathogenesis and public health policy to improve clinical outcomes in high-risk diabetic patients with complicated pneumococcal infection.