Molecular Epidemiology of Acinetobacter species
Harald Seifert and Hilmar Wisplinghoff
from: Acinetobacter Molecular Biology (Edited by: Ulrike Gerischer). Caister Academic Press, U.K. (2008)
Among the three clinically important Acinetobacter species, Acinetobacter baumannii, and unnamed Acinetobacter genomic species 3 and 13TU, A. baumannii is the most significant nosocomial pathogen and predominantly affects patients with impaired host defences in the intensive care unit. It was not until 1986, when major changes in the taxonomy of the genus Acinetobacter and the development of molecular methods to better identify acinetobacters at the species level opened the way for a more detailed study of the epidemiology of these organisms. Some of the methods used for species identification such as ribotyping and AFLP could also be used for strain characterization at the subspecies level. Pulsed-field gel electrophoresis (PFGE) became the gold standard for epidemiological strain typing not only for acinetobacters but for bacteria in general. PCR-based methods giving a lower level of discrimination and reproducibility but easier to perform were devised such as randomly amplified polymorphic DNA-PCR (RAPD-PCR) and repetitive extragenic palindromic (REP) PCR fingerprinting. All these methods are so-called comparative typing methods that require visual or computer-aided side-by-side comparison of molecular fingerprint patterns while multi locus sequence typing (MLST) is a so-called library typing method that was found useful for the study of the population structure of multiple microorganisms including A. baumannii. Using these methods the molecular epidemiology of A. baumannii and of other Acinetobacter species was studied and major insight was gained into the hospital epidemiology of these organisms, their mode of spread, the role of hospital personnel in their transmission and that of environmental surfaces. Spread from one patient to another in the same hospital, spread to another hospital in the same geographical region or spread even to more distantly located regions could be demonstrated. One question that remains to be answered is whether there are a few predominant clonal lineages that are responsible for the epidemic spread of multidrug-resistant A. baumannii within hospitals and across countries read more ...