Campylobacter jejuni

A Microbial Biorealm page on the genus Campylobacter jejuni

Classification

Higher order taxa

Kingdom: Bacteria, Phylum: Proteobacteria, Class: Epsilon Proteobacteria, Order: Campylobacterales, Family: Campylobacteraceae.

Species

Genus: Campylobacter, Species: C. jejuni.

Description and significance

Campylobacter jejuni is a gram negative bacteria that is curved and rod-shaped. It is most commonly found in animal feces, especially in wombat, kangaroo and bird feces. Campylobacter jejuni is a microaerophilic organism, this means that it requires an environment that contains reduced concentration of oxygen (~3-5% of oxygen and ~2-10% of carbon dioxide). Because of this requirement, it is very sensitive to stress in the environment. For example, too much oxygen, acidic condition, heating, and drying. Campylobacter jejuni is the number one cause of foodborn illness in the United States. Therefore, it is very important to sequence its genome to determine its role in these foodborne illnesses and effective treatments can be developed. Campylobacter jejuni is present in high levels in diarrhea stools of an infected individual as well as animal feces. This bacteria can be isolated from humans and animals. Isolation requires special antibiotic-containing media and an environment that contains optimal level of oxygen for microaerophilic organims.

Genome structure

The genome of Campylobacter jejuni consists of circular DNA and 1,616,554 nucleotides. It has 1707 genes and 1653 coding proteins. The GC content of Campylobacter jejuni is about 30% and the percentage coding of the bacteria is about 93%. The sequence of Campylobacter jejuni is variable. The eight distribution of variable sequences showed that they can use alternative terminal electron acceptor for oxygen. This represents the diverse life sources for Campylobacter jejuni. According to MLST type, the correlation of clonal complex and distribution of the genes is strong. However, these distribution of genes showed no evidence for their host preferences. Therefore, widespread horizontal gene transfer between clonal complexes is not supported.

Cell structure and metabolism

Campylobacter jejuni is a gram negative bacteria like bacilli. It is microaerophilic and non-fermentive organism. Its structure is similar to most gram negative bacteria. It has one flagellum at one pole or both poles of the cell. The cell contains an outer membrane and an inner membrane with periplasm in between the two membranes. The outer membrane consist of lipopolysaccharide which are endotoxic. Membrane proteins are embedded on the outer membrane surface, they are antigenic and are used for invation of the host. Campylobacter jejuni uses oxygen as its final electron acceptor. This is expected since it is a microaerophilic organism and it gows in its optimal rate with ~5% of oxygen level plus ~10% carbon dioxide. The bacteria is very sensitive to environmental stress such as heating, drying and over concentrated levels of oxygen.

Ecology

Campylobacter jejuni is an interesting bacteria because it resembles some eukaryotic-like system for N-linked protein glycosylation. The disease Camylobacter jejuni caused is known as campylobacer enteritis or gasteroenteritis. The illness leads to severe diarrhea and fecal leukocytes. These symptoms are usually combined with fever, headaches and muscle pain. Children under 5 and young adults are more vulnerable to get the disease more than other groups. Although Campylobacter is the number one cause of foodborne illness, it is the least deadly. The case/fatality ratio is about 1/1000 which is very low.

Pathology

Campylobacter is a bacteria that is found in intestines of many animals and some humans. They cycle through in the intestine environment and lead to diarrhea. Clinical evidence suggests that the site of Campylobacter infection seems to be the ileum and jejunum in the small intestines rather than in the large intestines. Although it is the leading cause of foodborne illness in the United States, Campylobacter can be easily killed by cooking or heating. In most cases, Campylobacter can contaminate water, milk or undercooked meat, especially chicken. It only takes a small amount of bacteria to cause infection. The illness usually lasts 2 to 5 days, and most of these cases will disappear without treatment. However, 25% of these patients are likely to have a relaspse. The early symptom of Campylobacter infection is usually abnormal abdominal pain and is then followed by bloody diarrhea. Other common accompanying symptoms are fever, headache, musle pain, sometimes vomiting and dehydration may occur. Although vomiting and dehydration are not usually prominent, they may be severe enough to lead to death. Complication of Campylobacter infection may also contribute to mortality. For example, deaths have occured in patients who also have cirrhosis, malnutrition, and lymphoma.

Application to Biotechnology

Campylobacter jejuni is not known of producing any useful compounds or enzymes. It is mainly known as a pathogen that causes most foodborne illness in the United States. However, Campylobacter jejuni produce an enzyme called Beta-lactamase that is associated with its antibiotic-resistance, mostly to ampicillin and penicillin. The mechanism of Beta-lactamase in Campylobacter jejuni is still unknown, but effective antibodies are developed to treat Campylobacter jejuni infected illness. For example, the most effective antibody for the treatment is erythromycin. Clinical treatments have suggested that patients treated with erythromycin have significantly reduced the presence of Campylobacter jejuni in their stools, although little is known about its mechanism. Despite erythromycin's effectiveness, moderate erythromycin resistance of Campylobacter jejuni is still present(~5%). However, because the patient is usually recovered without treatment, erythromycin resistance of Campylobacter jejuni is insignificant. Therefore, erythromycin is still the most preferred antibiotics for the treatment of this illness.

Current Research

Enter summaries of the most recent research here--at least three required

References

1) [http://en.wikipedia.org/wiki/Campylobacter_jejuni, "Campylobacter Jejuni" Wekipedia

2) [http://www.cfsan.fda.gov/~ebam/bam-7.html, Jan M. Hunt, Carlos Abeyta and Tony Tran, "Bacteriological Analytical Manual, 8th Edition, Revision A, 1998 Chapter 7" March 2001

3) [http://www.cfsan.fda.gov/~mow/chap4.html, "Foodborne Pathogenic Microorganisms and Natural Toxins Handbook" January 1992

4) Hepworth PJ, Leatherbarrow H, Hart CA, Winstanley C. "Use of suppression subtractive hybridisation to extend our knowledge of genome diversity in Campylobacter jejuni" April 2007; 8(1):110 [PubMed

Edited by LiJie Shi student of Rachel Larsen[lshi@ucsd.edu]