Final answer:
The main causative agent of puerperal sepsis is Streptococcus pyogenes. This bacterium is adept at attaching to host tissues and evading immune response, leading to serious infections in new mothers after childbirth. Proper diagnosis and treatment rely on identifying the pathogen and its susceptibility to antibiotics.
Step-by-step explanation:
The principle causative agent of puerperal sepsis is Streptococcus pyogenes. This bacterium is known for its ability to attach to host tissues using M protein and produce a carbohydrate capsule that helps it avoid phagocytosis. S. pyogenes also releases exotoxins that contribute to its virulence. Although S. pyogenes is a common cause, it's important to note that there are various other bacteria that can cause puerperal sepsis, including Staphylococcus aureus, Escherichia coli, and Clostridium perfringens. Diagnosis of puerperal fever is based on clinical symptoms and the isolation and identification of the etiologic agent, followed by antimicrobial susceptibility testing to determine the best treatment.