Impact of microbiology and antimicrobial treatment on mortality in septic shock

Introduction

Infectious characteristics, the infection source, and appropriate antibiotics are analyzed in relation to mortality in a cohort of patients with severe sepsis and septic shock.

Methods

An observational and prospective cohort study over 1 year of all patients admitted to one of the adult ICUs of the three major university hospitals in Beirut. Demographics, appropriate ICU therapies within 48 hours of admission, appropriate antibiotic prescription within 48 hours of admission, antibiotic duration and number were registered. Infections were defined as definite or suspected. The infectious source, microbial agents and anti-biograms were identified. Data were collected only during the ICU stay, and outcome was recorded at hospital discharge (alive or dead).

Results

One hundred and twenty-seven patients with an average age of 65 years were enrolled, 52% of admissions were from the emergency room and 83% were medical patients. Fifty-eight percent of the patients had severe sepsis within 48 hours of admission. The average APACHE II and Sequential Organ Failure Assessment scores were 21 and 7, respectively. Immuno-deficiency was present in 30%. Overall mortality was 45%. Definite infection was diagnosed in 61% of the patients and bacteremia in 31.5%. Appropriate antibiotic prescription was significantly higher in patients with less severe sepsis compared with severe sepsis (>1 organ failure). Mortality was significantly higher in patients prescribed a higher number of antibiotics while the length of antibiotic prescription was not different between survivors and nonsurvivors. Escherichia coli (n = 14) was the most common isolate in blood cultures, followed by Candida (n = 5). Fungal pathogens were significantly more associated with nosocomial infections and with mortality. Multiresistant pseudomonas was significantly more associated to mortality compared with extended spectrum beta lactamase or methicillin-resistant Staphylococcus aureus. Positive urine culture was protective of a higher organ failure score. In multivariate analysis, Gram-negative bacteria, a nosocomial source and immuno-deficiency were all associated with an increased risk of death.

Conclusion

Inappropriate antibiotic prescription is associated with more severe sepsis. Mortality is higher in nosocomial sepsis. Candida is a serious nosocomial agent in severe sepsis and is associated with increased mortality as well as multiresistant pseudomonas aeruguinosa.