Nosocomial bacteremia due to Acinetobacter baumannii: epidemiology, clinical features and treatment

Acinetobacter baumannii is an important cause of nosocomial infections in many hospitals. It is difficult to control and infection caused is difficult to treat due to its high resistance in the environment and its ability to develop resistance to antimicrobials. Bacteremia, followed by respiratory tract and surgical wound infections, is the most significant infection caused by A. baumannii. The known risk factors for A. baumannii bacteremia are invasive procedures and the use of broad-spectrum antimicrobials. Consequently, episodes of bacteremia due to A. baumannii occur most frequently in critically-ill patients admitted to an intensive care unit. The clinical manifestations of bacteremia by A. baumannii are not specific. The most common sources of bacteremia are intravascular catheters and the respiratory tract. A. baumannii bacteremia is associated with a high crude mortality rate, but it is difficult to distinguish morbidity and mortality attributable to A. baumannii from that attributable to the common and severe co-morbidity in these patients. A. baumannii is a bacterium that appears to have a propensity for developing multiple antimicrobial resistance extremely rapidly. These data are disturbing because the therapeutic possibilities decrease while inappropriate antimicrobial treatment contributes to patient mortality. Generally, imipenem is the most active agent against A. baumannii. However, the description of imipenem-resistant A. baumannii strains is becoming increasingly common. The usual treatment for A. baumannii bacteremia is an active beta-lactam alone, preferably one with a limited spectrum. Before beginning treatment of a bacteremia by A. baumannii, it is very important to carry out a clinical evaluation of the patient to eliminate the possibility of a pseudobacteremia, and thereby avoid unnecessary treatment.