Corynebacterium jeikeium: Difference between revisions
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Revision as of 19:41, 18 August 2010
A Microbial Biorealm page on the genus Corynebacterium jeikeium
Classification
Higher order taxa
Domain: Bacteria
Phylum: Actinobacteria
Class: Actinobacteria
Sub-Class: Actinobacteridae
Order: Actinomycetales
Family: Corynebacterineae
Genus: Corynebacterium
Species: jeikeium
Genus
Corynebacterium jeikeium strain K411
Description and significance
Corynebacteria are gram positive, catalase-positive, aerobic, mostly non-motile rods. Corynebacterium jeikeium, an opportunistic pathogen, commonly colonizes in the skin, especially in immunocompromised hosts. Because of its broad-spectrum resistance to antimicrobial agents, the susceptibility of C. jeikeium strains is studied to a wide range of antibiotics. The strains were separated into two groups depending on the susceptibility to erythromycin, with one group representing resistant organism and the other representing susceptible organisms.
Genome structure
The genome of C. jeikeium K411 consists of a circular chromosome of 2,462,499 base pairs, and around 14,000 of them are bacteriocin-producing plasmids. Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strains. The chromosome of C. jeikeium K411 contains more than two thousand predicted coding sequences, 52% of which were considered to originate from the same ancestor as in the Corynebacterium glutamicum, Corynebacterium efficiens, and Corynebacterium diphtheriae genomes.
Cell structure and metabolism
Corynebacterium jeikeium is a "lipophilic" bacterial species, meaning its growth is generally enhanced by the presence of lipids. Anaylyses of the genome sequence indicated that this feature most likely originated from the absence of fatty acid synthase, which leads to lipids becoming an essential nutritional requirement.
Fatty acids are building blocks for the synthesis of cell walls, which are organized with other lipids to form a permeable barrier that contributes to the natural resistance of C. jeikeium to different types of antibiotics. Another special metabolic feature in C. jeikeium is their utilization of carbohydrates. Since the components of phosphotranferase systems (PTS) are not encoded by C. jeikeium, carbohydrate uptake may be mediated by a putative sodium:solute symporter, or by putative sugar-specific ATP-binding cassette(ABC) transporter. The restricted carbohydrate use reflects their adaptation to the availability of nutrients in the predominantly colonized areas of human skin.
Ecology
Corynebacterium jeikeium is commonly found in the human skin flora. Over colonization of C. jeikeium occurs in severely immunocompromised hosts, which cause infections, especially in patients with skin disruption.
Pathology
Corynebacterium jeikeium is a multidrug-resistant bacteria of the human skin flora that causes infection in severely immunocompromised patients with indwelling medical devices. This pathogenic characteristic is particularly common in neutropenic patients with intravasular catheter, prolonged neutropenia, and/or those undergoing multiple antibiotic regiments.
Patients who are diagnosed with Corynebacterium jeikeium show signs of normal bacterial infection such as fever. The predicted virulence factors of Corynebacterium jeikeium are mainly involved in ensuring the availability of exogenous fatty acids by damaging the host tissue. Studies done on the presence of plasmids in C. jeikeium have shown that, instead of extrachromosomal DNA, it's the bacterial chromosome that encode most of the multiresistance phenotype.
Application to Biotechnology
Reasearch has not found any useful compounds or enzymes produced by C. jeikeium; however, its metabolic features have provided the fundamental understanding of multidrug-resistant bacteria.
Current Research
1. The most current research done in 2005 by Tauch et al. presented "the complete genome sequence and bioinformatics analysis of multiresistant clinical isolate C. jeikeium K411" from bone marrow transplant patients who received immunosuppressive therapy and broad-spectrum antibiotics. The results allowed us to understand not only the physiology and lifestyle of C. jeikeium, but also "the molecular and biochemical basis for multiresistance as well as the pathogenic potential of this clinically important species".
2. Another study on the multidrug-resistant characteristic of C. jeikeium was done by Rosato et al. in 2001. This study focused on the susceptibility of clinical strains to a range of antimicrobial agents. "The strains were separated into two groups depending on the susceptibility to erythromycin (ERY)." Even though the molecular basis was not completely understood, the results of the study indicated that the phenotype of multidrug resistance was a result of the accumulation of individual genetic events.
3. C C Wang et al. also studied C. jeikeium bacteremia in bone marrow transplant patients who had indwelling catheters. The results showed that removal is not necessary to rid the infection as long as patients are treated with vancomycin.
References
Edited by Michelle Ku, student of Rachel Larsen and Kit Pogliano
