[Are isolation measures needed in the hospital management of Acinetobacter baumannii colonizations-infections?]

Until 2001, the infection control department of the Besançon university hospital (France) recommended isolation precautions for all patients colonized-infected by Acinetobacter baumannii (Ab) whatever the antibiotic susceptibility of the strain. These systematic isolation procedures were given up at the beginning of 2002 since the number of colonized-infected patients remained stable from 1998 to 2001.

The aim of this study was to evaluate the impact of this decision on the risk of Ab infection.

Incidence rates of colonization-infections that were observed during years 2002 and 2003 were compared with expected incidence rate, based on data from 1998-2001 period. Infection control practices and antibiotics consumption were evaluated for each ward of hospitalisation. Genotyping made it possible to determine diversity of clones inside each unit and the whole hospital.

The expected incidence per 1000 patients-days was 0.22 in comparison with observed data in 2002, 0.34 (CI(95%) [0.28-0.42]), and in 2003, 0.53 (CI(95%) [0.45-0.63]). The expected number of Ab bloodstream infections, about two per year compared with the observed numbers in 2002 and 2003 respectively seven and 17. The number of unit with more than three cases per year increased from seven in 1999 to 18 in 2003. Antibiotics consumption did not change significantly.

Genotyping results show the importance of cross-transmission in these units. Finally, observed results suggest that some measures of isolation precautions in addition to standard precautions are needed to prevent outbreaks of Ab.