ACINETOBACTER

Acinetobacter

Acinetobacter

Acinetobacter

Acinetobacter is the most relevant human pathogen within the Acinetobacter genus. Most Acinetobacter isolates are multi-resistant, containing in their genome small, isolated islands of alien (meaning transmitted genetically from other organisms) DNA and other cytological and genetic material; this has led to more virulence. Acinetobacter have no flagellum; the name is Greek for motionless (Dijkshoorn, 2008).

The knowledge of the biology or ecology of acinetobacters at species level is limited. This is due to the fact that identification of acinetobacters at species level is difficult (Dijkshoorn, 2008). A variety of genotypic methods has been explored and applied to investigate the diversity or phylogeny in the genus. These methods include high resolution fingerprinting with AFLP, PCR-RFLP with digestion of PCR amplified sequences, and analysis of various DNA sequences (Brussow, 2007). Of these, AFLP analysis and amplified 16SrDNA ribosomal DNA restriction analysis have been validated with large numbers of strains of all described species. Nucleotide sequence based methods are expected to be the standard for identification in the near future, but a prerequisite for their successful application is the availability of libraries of sequences of strains of all described genomic species. For each species, the sequences should cover the intra-species diversity. Sequence comparisons will also provide a valuable tool to study the phylogenetic relatedness of species (Dijkshoorn, 2008).

Acinetobacter is a gram-negative coccobacillus that during the past three decades has emerged from an organism of questionable pathogenicity to an infectious agent of importance to hospitals worldwide (Brussow, 2007). Acinetobacter infections have long been clinically prominent in tropical countries, have been a recurrent problem during wars and natural disasters, and have recently caused multi-hospital outbreaks in temperate climates. It can cause superlative infections in any organ system (Wood, 2002). It is often an opportunist in hospitalized patients. The significance of isolates from clinical specimens is difficult to determine because they often represent colonization (Brussow, 2007). The respiratory system is the most common site for infection. Acinetobacter easily colonizes tracheostomy sites. Acinetobacter causes community-acquired bronchiolitis and tracheobronchitis in healthy children and tracheobronchitis in immunocompromised adults (Wood, 2002). Spread in ICUs has been attributed to colonized health care practitioners, contaminated common equipment, and contaminated parenteral nutrition solutions. Hospital-acquired Acinetobacter pneumonias are frequently multi-lobar and complicated. Secondary bacteremia and septic shock are associated with a poor prognosis (Wood, 2002).

Acinetobacter tends to be resistant to many antimicrobials. Typically, imipenem can be used. However, outbreaks of imipenem-resistant Acinetobacter have occurred. ...