Scientists in the United States conducted a retrospective cohort study to assess the effect of late onset of antibiotic therapy on mortality in patients with nosocomial bacteremia caused by Staphylococcus aureus ( BSA). During the study, it was planned to determine the duration of the delay in prescribing adequate therapy, which is reflected in the increased risk of unsuccessful treatment, and to assess the effect of premature initiation of a antibiotic therapy on the clinical results of the disease, the length of hospital stay and mortality.

The study included 167 patients who, from 1999 to 2001, had episodes of SAB that developed no earlier than 2 days after their admission to hospital.

The delay in starting treatment, calculated using the classification and regression trees algorithm (CART, classification and regression trees), was 44.75 hours, compared to the group of patients who started treatment on time.

The CART algorithm was also used to determine the difference in mortality between the early and premature treatment groups. Mortality in the early treatment group was 19%, while in the premature treatment group, it was 33%. Patients with a high-risk source of infection, as well as patients with a high score on the APACHE II scale, have shown the most pronounced reduction in mortality from early administration of antibiotics. Thus, in patients with an APACHE II score greater than 15.5 and a “high risk” source of infection (mainly not related to intravenous catheters), the mortality was 87% in the premature treatment group and 45 % in the early treatment group.

After performing a multiple analysis, it was found that delay in initiating antibiotic therapy was an independent predictor of increased mortality (odds ratio 3.8; 95% confidence interval 1.3-11 , 0; p = 0.01) and increases the length of hospital stay (20.2 days vs 14.3 days; p = 0.05) compared to rapid treatment.

The results of the study confirm the hypothesis that late antibiotic treatment worsens the clinical results of the disease. Measures must be taken to ensure the early administration of broad-spectrum antibacterial drugs to patients at risk of infections caused by methicillin-resistant strains of S.aureus (especially MRSA) severe patients and patients with a high risk source of infection.