Comparison of molecular typing methods for the analyses of Acinetobacter baumannii from ICU patients

- PFGE and MLVA are highly discriminatory when used for typing A. baumannii.
- Use MLVA or MLST to assess relatedness of isolates from different time periods.
- PFGE and MLVA isolate genotypes confirm many genetic lineages in a single patient.
- Using more than one molecular method increases the discriminatory power.

Acinetobacter baumannii has emerged as an important cause of healthcare-associated infections causing great morbidity and mortality. Despite its clinical importance, it is still unknown which molecular typing method is the best to determine or confirm institutional outbreaks as well as to identify epidemiologically related isolates from different geographical areas. To determine the most discriminatory molecular typing method, we isolated A. baumannii from perianal swabs collected from intensive care unit (ICU) patients in a cohort study during 2002 and 2008. Strains from each year were analyzed by pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST), and multi-locus variable-number tandem repeat analysis (MLVA). Genetic relatedness of the isolates was consistent between PFGE and MLST as well as between analyses of loci containing MLVA and MLST. Our data show that PFGE and MLVA are similar when discriminating between isolates and are both good methods to use when questioning whether two isolates are indistinguishable.