Etiology

Common Causes

Sepsis, a life-threatening organ dysfunction due to a dysregulated host response to infection, is commonly caused by a variety of infections. The most prevalent primary cause of sepsis is related to abdominal infections, with urinary tract infections, pneumonia, skin and soft tissue infections, and bacteremia also being significant contributors. The severity of sepsis can range from sepsis to severe sepsis and septic shock, depending on the extent of organ dysfunction and the body’s response to the infection (Saleh, Khodaie, & Mohtadi, 2020).

Microbial Pathogens

The most common microbial pathogens causing sepsis in adults in the US are Gram-negative rods and Gram-positive cocci. Gram-negative rods were isolated in 55% of patients with blood culture-positive sepsis (Critical Care Medicine 2023). Among the Gram-negative rods, Escherichia coli, Klebsiella species, Proteus species, and Pseudomonas aeruginosa were associated with lower in-hospital mortality (Ohnuma et al., 2023). Gram-positive cocci were isolated in 47% of patients with blood culture-positive sepsis (Tsou et al., 2021). Methicillin-resistant Staphylococcus aureus (MRSA) was present in 11% of cases (Gatica et al., 2023). Other pathogens associated with higher in-hospital mortality were Acinetobacter species and MRSA (Pfaff, 2023). The incidence of Gram-negative pathogens has increased over time, surpassing Gram-positives as the leading cause of sepsis in the US. Anaerobes have also shown an increasing trend in incidence.

Microorganisms: The causative organisms in sepsis vary:

1. Gram-negative bacteria (44-59%)
2. Gram-positive bacteria (37-52%)
3. Anaerobic organisms (5%)
4. Fungi (4-10%) However, in approximately 70% of cases, a specific causal microorganism is not documented​​. Common sources of infection include the lungs, intra-abdominal space, and genitourinary tract​​.

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