Is airborne transmission of Acinetobacter baumannii possible: A prospective molecular epidemiologic study in a...

Understanding the dynamics of aerial spread of Acinetobacter may provide useful information for production of effective control measurements. We investigated genetic relationships between air and clinical isolates of Acinetobacter baumannii in an intensive care unit (ICU) setting.

We conducted a prospective surveillance study in a tertiary care hospital for 8 months. A total of 186 air samples were taken from 2 ICUs. Clonal characteristics of air isolates were compared with the prospective clinical strains and the previously isolated strains of ICU patients over a 23-month period.

Twenty-six (11.4%) air samples yielded A baumannii, of which 24 (92.3%) isolates were carbapenem-resistant. The Acinetobacter concentration was the highest in bedside sampling areas of infected patients (0.39 CFU/m³). Air isolates were clustered in 13 genotypes, and 7 genotypes (including 18 air strains) were clonally related to the clinical strains of 9 ICU patients. One clone continued to be cultured over 27 days in ICU air, and air isolates could be clonally related to 7-week retrospective and approximately 15-week prospective clinical strains.

The results of this study suggest that infected patients could spread significant amounts of Acinetobacter to ICU air. These strains could survive in air for some weeks and could likely still infect new patients after some months. Special control measurements may be required against the airborne spread of Acinetobacter in ICUs.