Intracellular bacteria in blood smears in patients with central venous catheters

The presence of intracellular bacteria in blood smears is usually associated with overwhelming sepsis and an ominous prognosis. Recently, the hematology laboratory at our institution documented this finding in a group of mostly asymptomatic patients. We studied seven adult patients from a tertiary care university hospital in whom intracellular bacteria were found incidentally on routine manual differential cell counts of 100 white blood cells during a 12-month period. A retrospective review of the clinical and laboratory data was performed. All seven patients were immunosuppressed and had central venous catheters in place. The blood samples positive for intracellular bacteria were all catheter derived. Six patients were asymptomatic at the time of bacteria detection, but they had blood cultures that were positive for coagulase-negative Staphylococcus; five of these patients became symptomatic 1 to 14 days after bacteria detection. Bacteremia persisted in five of these six patients until the eventual removal of the catheters. The one symptomatic patient had Pseudomonas aeruginosa bacteremia and died shortly after admission. The finding of intracellular bacteria in routine differential blood cell counts from a central venous catheter blood specimen most likely indicates active infection. We recommend that central venous catheters be removed in such patients, even if the patient is asymptomatic.