The concept of septicemia should probably be separated from that of bacteremia, although in many studies the two are not clearly separated. In bacteremia, a few bacteria from a focal area of infection escape from time to time into the peripheral blood. However, the main focus remains localized, and symptoms are primarily those that are caused by infection in the particular organ or tissues involved. Bacteremia may occur without infection following certain procedures, such as dental extraction (18%-85%), periodontal surgery (32%-88%), tooth brushing (0%-26%), bronchoscopy (15%), tonsillectomy (28%-38%), upper GI endoscopy (8%-12%), sigmoidoscopy (0%-10%), urethral dilatation (18%-33%), cystoscopy (0%-17%), and prostate transurethral resection (12%-46%). In one representative series, E. coli was isolated in about 20% of patients with bacteremia; S. aureus, 10%; and Klebsiella, pneumococcus, Streptococcus viridans, Bacteroides, and Pseudomonas, about 6% each. The percentage of S. epidermidis isolated varies greatly (3%-34%), probably depending on how many were considered contaminants. Polymicrobial bacteremia is reported in about 7% of cases (range, 0.7%-17%). In septicemia there is widespread and relatively continuous peripheral blood involvement. The characteristic symptoms are systemic, such as marked weakness and shock or near shock. Shock has been reported in 16%-44% of patients with gramegative bacteremia. These symptoms are usually accompanied by high fever and leukocytosis. However, septic patients may be afebrile in 10% (range, 4%-18%) of cases. Leukocytosis occurs in 60%-65% of patients (range, 42%-76%), leukopenia in 10% (range, 7%–17%), bands increased in 70%-75% (range, 62%-84%), and total neutrophils are increased in about 75% (range, 66%-92%). Any bacteria may cause septicemia. More than 50% of cases are due to gramegative rod organisms, with E. coli being the most frequent. Staphylococcus aureus probably is next most common. (In one literature review of seven studies of sepsis published in 1990 and 1991, four studies had predominance of gramegative organisms and three had predominance of gram-positive. In four of the seven studies, the percentage of gramegative and gram-positive organisms was within 10% of each other). The portal of entry of the gramegative organisms is usually from previous urinary tract infection. Many cases of septicemia follow surgery or instrumentation. The source of Staphylococcus septicemia is often very difficult to trace, even at autopsy. However, pneumonia and skin infections (sometimes very small) are the most frequent findings.

Diagnosis. Blood cultures are the mainstay of bacteremia or septicemia diagnosis. Strict aseptic technique must be used when cultures are obtained, since contamination from skin bacteria may give false or confusing results. In cases of bacteremia or in septicemia with spiking fever, the best time to draw blood cultures is just before or at the rise in temperature. Three culture sets, one drawn every 3 hours, are a reasonable compromise among the widely diverging recommendations in the literature.

Antibiotics and blood cultures. Blood should be drawn for culture before antibiotic therapy is begun, although a substantial number of cultures are positive despite antibiotics. Certain antibiotic removal devices are commercially available that can be of considerable help in these patients. It is essential that the culture request contain the information that antibiotics have been given, unless they have been stopped for more than 1 week. If penicillin has been used, some laboratories add the antipenicillin enzyme penicillinase to the culture medium. However, others believe that penicillinase is of little value and might actually be a potential source of contamination.