Sunday, April 22, 2012

Acinetobacter introduction

Acinetobacter is a genus of Gram-negative bacteria belonging to the Gammaproteobacteria. Acinetobacter species are non-motile and oxidase negative, and occur in pairs with a magnifying glass.

Are important soil organisms, where they contribute to the mineralization of, for example, aromatic compounds. Acinetobacter are a key source of infection in debilitated patients in the hospital, including species of Acinetobacter baumannii. [1]

Contents [hide]
1 Etymology
2 Description
3 Taxonomy
4 Identification
5 natural habitat
6 Clinical Significance
Treatment 7
8 Biotechnology
9 References
10 External links
 EtymologyAcinetobacter is a word composed of "non-motile rod / immobile" Greek scientific means. The first element-Acinetobacter is a transliteration of the Greek ακινητο unusual, the romanization is common in English is akineto-as in akinetic.

DescriptionSpecies the genus Acinetobacter are strictly aerobic nonfermentative gram-negative bacilli. They show a predominantly coccobacilli morphology on nonselective agar. Rods predominate in fluid media, especially during early growth.

The morphology of Acinetobacter sp. can be very variable in gram-stained human clinical specimens and can not be used to differentiate Acinetobacter from other common causes of infection.

Most strains of Acinetobacter, except some of the strain A. lwoffii, grow well on MacConkey agar (without salt). Although officially classified as nonlactose fermentation, which often are partially lactose fermentation when grown on MacConkey agar. They are oxidase-negative, non-motile, and usually negative nitrate.

 TaxonomyThe genus Acinetobacter comprises 17 validly named and 14 unnamed species (genomics). [2] Some unrelated (genomic) species have common names, while some other species appear to be consistent, but have different names. Knowledge of the biology and ecology of acinetobacters at the species level is limited. This is because the identification of species level acinetobacters is difficult. A system of phenotypic identification of species described, and a variety of genotypic methods have been explored and applied to investigate the diversity and phylogeny in the genus. These methods include high resolution fingerprinting with AFLP, PCR-RFLP with digestion of PCR amplified sequences and analysis of different DNA sequences. Of these, the AFLP analysis and restriction analysis 16SrRNA amplified ribosomal DNA have been validated with a large number of strains of all species described. Nucleotide sequence-based methods are expected to be the standard for identification in the near future. [2]

However, because routine identification in clinical microbiology laboratory is not possible (yet), are divided and grouped into three main complexes:

Acinetobacter calcoaceticus-baumanii complex: glucose-oxidising nonhemolytic, (A. baumannii can be identified by OXA-51 typing)
Acinetobacter lwoffii: glucose-negative nonhemolytic
Acinetobacter haemolyticus: hemolytic
IdentificationDifferent bacterial species of this genus can be identified using fluorescence-denitrification lactose medium (FLN) to find the amount of acid produced by metabolism of glucose.

The other reliable proof of identification to genus is chromosomal DNA transformation assay (CTA): In this essay, a tryptophan auxotroph mutant naturally competent Acinetobacter baylyi (BD4 trpE27) is transformed with total DNA of a putative Acinetobacter isolate and the transformation mixture plated in a brain heart infusion agar (BHI). Growth is then harvested after incubation for 24 hours at 30 ° C, plated on minimal agar Acinetobacter (MOA), and incubating at 30 ° C for 108 h. Growth on minimal agar medium indicates a transformation assay confirm the positive and isolated as a member of the genus Acinetobacter. E. coli HB101 and A. MTCC1921T calcoaceticus can be used as positive and negative controls, respectively. [3]

Natural habitatAcinetobacter spp are widely distributed in nature. They are able to survive on various surfaces (both wet and dry) in the hospital setting, which is an important source of infection in debilitated patients. Occasional strains are isolated from foods, and some are able to survive in the various medical equipment and even healthy human skin. In Mythbusters Discovery Channel, hundreds of colonies of Acinetobacter was found in a kitchen sponge every day.

In drinking water, Acinetobacter has shown that bacteria aggregate that otherwise do not form aggregates.

Clinical significanceIn general, Acinetobacter species are considered nonpathogenic to healthy individuals. However, various species persist in hospital environments and cause severe life-threatening infections in immunocompromised patients. The spectrum of antibiotic resistance of these organisms, along with survival skills that are a threat to hospitals, as documented by recurring outbreaks both in highly developed countries and elsewhere. An important factor in their pathogenic potential is, we assume an effective means of horizontal gene transfer.

Most infections occur in immunocompromised individuals, and the strain of A. baumannii is the second most commonly isolated bacteria not fermenting in human samples.

Acinetobacter is frequently isolated in nosocomial infections and is especially prevalent in intensive care units, where both sporadic cases and epidemic and endemic occurrence is common. A. baumannii is a frequent cause of nosocomial pneumonia, especially late-onset ventilator-associated pneumonia. It can cause several other infections, including infections of the skin and the wound, bacteremia and meningitis, but A. lwoffi is primarily responsible for the latter. A. baumannii can survive on human skin or dry surfaces for weeks.

Biofilm formation is an important feature of the majority of clinical isolates of Acinetobacter sp. Biofilms are collections of microbial cells surface are enclosed in an extracellular polymeric matrix. It is clear from the epidemiological evidence that Acinetobacter biofilms play a role in infectious diseases such as cystic fibrosis, periodontitis, bloodstream infections, and urinary tract infections due to its ability to colonize indwelling medical devices. The antibiotic resistance markers are often plasmid-borne, and the plasmids present in strains of Acinetobacter can be transferred to other pathogenic bacteria. The ability of Acinetobacter species to adhere to surfaces, form biofilms, show antibiotic resistance and gene transfer means that there is an urgent need to study the factors responsible for its spread. [4]

Since the beginning of the Iraq war, more than 700 U.S. soldiers have been infected or colonized by A. baumannii. Four civilians being treated for serious illnesses at Walter Reed Army Medical Center in Washington, DC contracted the infections and died. In Landstuhl Regional Medical Center, a U.S. military hospital in Germany, another civilian under treatment, a German woman aged 63, contracted the same strain of A. baumannii infecting troops in the installation and also died. These infections appear to have been acquired in the hospital. Based on genotyping of A. baumannii cultured from patients before the start of the Iraq war, one can assume that it is likely that the soldiers contracted the infection during hospitalization for treatment in Europe.

 TreatmentAcinetobacter species are naturally resistant to many types of antibiotics, including penicillin, chloramphenicol and aminoglycosides often. Fluoroquinolone resistance has been reported during therapy, which has also resulted in increased resistance to other classes of drugs mediated by efflux of active drug. A dramatic increase in antibiotic resistance in Acinetobacter strains has been reported by the CDC and the carbapenems are recognized as the gold standard for treatment of last resort [5] Acinetobacter species are unusual in that they are sensitive to sulbactam; . Sulbactam is most commonly used to inhibit bacterial beta-lactamase, but this is an example of the antibacterial property of sulbactam itself. [6]

In November 2004, the CDC reported an increasing number of bloodstream infections A. baumannii in patients at military medical facilities in which service members injured in the region of Iraq / Kuwait during Operation Iraqi Freedom (OIF) and Afghanistan during Operation Enduring Freedom (OEF) were treated. [7] Most of these were multiresistant. Among a number of isolates from Walter Reed Army Medical Center, 13 (35%) were susceptible to imipenem alone, and two (4%) were resistant to all drugs tested. An antimicrobial agent, colistin (polymyxin E) has been used to treat infections with Acinetobacter baumannii resistant tuberculosis, however, antimicrobial susceptibility testing for colistin was not performed in strains described herein. Because A. baumannii can survive on dry surfaces for up to 20 days, which pose a high risk of spread and contamination in hospitals, which could compromise immunity and other patients at risk of drug-resistant infections that are often fatal and generally expensive to treat.

Reports indicate that this bacterium is susceptible to phage therapy [8] A phage directed against Acinetobacter showed a remarkable lytic activity both in vitro and in vivo .. Only 100 pfu of phage protected mice against Acinetobacter [9]

[Edit] BiotechnologyMany of the characteristics of Acinetobacter ecology, taxonomy, physiology, genetics and point to the possibility of using its unique characteristics for future applications. Acinetobacter strains are often ubiquitous, show metabolic versatility, and are robust. And some providers convenient systems for modern molecular genetic manipulation and subsequent product engineering. These characteristics are exploited in various biotechnological applications including biodegradation and bioremediation, lipids and production of novel peptides, enzyme engineering, biosurfactant, and the production of biopolymers and engineering of novel derivatives of these products. It is anticipated that progress in these fields will expand the range of applications of modern biotechnology for Acinetobacter. [10]

References ↑ Gerischer U (editor). (2008). Acinetobacter Molecular Biology (1st ed.). Caister Academic Press. ISBN 978-1-904455-20-2.
^ A b Dijkshoorn L (2008). "The diversity of the genus Acinetobacter." Acinetobacter Molecular Biology (Gerischer U, ed.). Caister Academic Press. ISBN 978-1-904455-20-2.
^ Rokhbakhsh-Zamin F., D.P. Sachdev, N. Kazemi-Pour, Engineer A., ​​SS Zinjarde, PK and BA Dhakephalkar Chopade. (2011). Characterization of plant growth promoting characteristics of Acinetobacter species isolated from the rhizosphere of Pennisetum glaucum. J Microbiol Biotechnol. 21 (6): 556-566.
^ LC Antunes, imperi F, Carattoli A, P. Visca Deciphering the multifactorial nature of pathogenicity Acinetobacter baumannii. PLoS ONE. 2011, 6 (8): e22674. Epub 2011 August 1.
^ J Rahal (2006). "The new antibiotics against infections of Pseudomonas aeruginosa combinations with almost completely resistant and Acinetobacter species." Clin Infect Dis 43 Suppl 2: S95-9. doi: 10.1086/504486. PMID 16894522.
^ Wood GC, Hanes SD, Cruz MA, Fabian TC, BA Bougher. (2002). "Comparison of ampicillin-sulbactam and imipenem-cilastatin for treatment of Acinetobacter ventilator-associated pneumonia." Clin Infect Dis 34 (11): 1425-30. doi: 10.1086/340055. PMID 12015687.
^ Centers for Disease Control and Prevention (CDC) (2004). "Acinetobacter baumannii infections among patients in the treatment of military medical facilities wounded American soldiers, 2002-2004." MMWR Morb Mortal Wkly Rep 53 (45): 1063-6. PMID 15549020.
^ Matsuzaki S, Rashel M, Uchiyama J, et al. (October 2005). "Bacteriophage therapy: a revitalized therapy against bacterial infectious diseases." J. Infect. Chemother. 11 (5): 211-9. doi: 10.1007/s10156-005-0408-9. PMID 16258815.
^ H Brüssow (2007). "Phage therapy: the Western perspective." Bacteriophage: Genetics and Molecular Biology (Mc Grath S and van Sinderen D, ed.). Caister Academic Press. ISBN 978-1-904455-14-1. ~ ~ V.
^ Gutnick D (2008). "The potential application of Acinetobacter in Biotechnology". Acinetobacter Molecular Biology (Gerischer U, ed.). Caister Academic Press. ISBN 978-1-904455-20-2