Gram-hegative bacillemia.

Members of the Klebsiella-Enterobacter-Serratia group now appear to be the most common cuase of gram-negative bacillemia, followed in order of frequency by E. coli, Bacteroides, polymicrobic infection, Pseudomonas aeruginosa, and miscellaneous pathogens. However, E coli continues to be the organism most frequently responsilbe for bacteremia arising from the urinary tract. Although the urinary tract remains the most common portal of entry for gram-negative bacillemia, a wide variety of extraurinary lesions have assumed increased importance in the pathogenesis of this condition. There is marked variability in the clinical course and outcome of gram-negative bacillemia. Grade of underlying disease and grade of illness cuased by infection are major determinants of fatal outcome. When the patient with gram-negative bacillemia has severe illness due to infection, prompt and decisive action is necessary to prevent death. Antimicrobiol drugs are administered on the basis of a presumptive etiologic diagnosis after appropriate smears and cultures are obtained, but before the causal organism is definitively identified or its in vitro susceptibility is determined. The presumptive etiologic diagnosis is based upon knowledge of the anatomic location of the infection, the circujstances involved in its development, and certain clinical clues. Knowledge of the antimicrobial drugs most likely to be effective against the suspected pathogen(s) will provide a rational basis for selection of antimicrobial agents until the results of definitive microbiologic studies are available. Using this approach, the mortality of gram-negative bacillemia arising from the urinary tract has been reduced markedly from the mortality reported in earlier years.