What bacteria cause sepsis?

Sepsis is a life-threatening whole-body inflammatory response to infection that can be caused by many different bacteria, but most cases are caused by a relatively small group of common pathogens that enter bloodstream from lungs, urinary tract, abdomen, or skin. The most common bacteria that cause sepsis include Escherichia coli, which is the leading cause of sepsis from urinary tract infections, Staphylococcus aureus including MRSA which causes sepsis from skin wounds and bloodstream infections, Streptococcus pneumoniae which causes sepsis from pneumonia, Klebsiella pneumoniae and other Klebsiella species from lungs and urinary tract, Pseudomonas aeruginosa especially in hospitals and immunocompromised patients, and Group A Streptococcus and Group B Streptococcus. Other causes include Enterococcus, Acinetobacter, and Neisseria meningitidis which causes rapid meningococcal sepsis. Any bacteria can cause sepsis if it reaches blood, including bacteria from bowel perforation where many gut bacteria spill into abdomen. Risk factors include older age, infants, weakened immune system, diabetes, cancer chemotherapy, indwelling catheters, and antibiotic-resistant bacteria which make treatment harder. Sepsis occurs when immune response to bacteria becomes dysregulated, damaging own organs, leading to low blood pressure and organ failure. Rapid antibiotics within one hour, IV fluids, and source control like draining abscess are critical, as mortality is 20 to 40 percent. Prevention includes vaccination for pneumonia, handwashing, wound care, and good ventilation with HEPA filtration to reduce airborne bacterial transmission in hospitals.