The right antibiotic in septic shock makes a massive difference

A retrospective review of appropriate vs inappropriate antimicrobial therapy was undertaken in over four thousand septic shock patients from multiple centres. In terms of definitions, the authors state:

Appropriate antimicrobial therapy was considered to have been initiated if an antimicrobial with in vitro activity appropriate for the isolated pathogen or pathogens (or in the case of culture-negative septic shock, an antimicrobial or antimicrobial agent concordant with accepted international norms for empiric therapy and modified to local flora) was either the first new antimicrobial agent with which therapy was started after the onset of recurrent or persistent hypotension or was initiated within 6 h of the administration of the first new antimicrobial agent. Otherwise, inappropriate therapy was considered to have been initiated.”

The results are striking: survival rates after appropriate and inappropriate initial therapy were 52.0% and 10.3%, respectively (odds ratio [OR], 9.45; 95% CI, 7.74 to 11.54; p < 0.0001).
A multivariable logistic regression analysis of possible factors that may affect outcome showed the appropriateness of the initial antimicrobial therapy remained most strongly associated with outcome (OR, 8.99; 95% CI, 6.60 to 12.23; p < 0.0001) among all the risk factors assessed.

Initiation of Inappropriate Antimicrobial Therapy Results in a Fivefold Reduction of Survival in Human Septic Shock
Chest. 2009 Nov;136(5):1237-48

N.B. This work was done by the same authors who brought us the study that showed the earlier antibiotics were given to hypotensive septic patients, the better the outcome:
Kumar A, Roberts D, Wood KE, et al. Duration of hypotension before initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock. Crit Care Med 2006; 34:1589-1596