Campylobacter

Campylobacter (meaning 'curved bacteria') is a genus of Gram-negative bacteria. Campylobacter typically appear comma- or s-shaped, and are motile. Most Campylobacter species can infect humans and other animals, causing disease. The bacterium's main natural reservoir is poultry; humans can contract the disease from eating food contaminated with Campylobacter species. Another source of infection is contact with infected animals, which often carry Campylobacter asymptomatically. At least a dozen species of Campylobacter have been implicated in human disease, with C. jejuni and C. coli being the most common. C. jejuni is now recognized as one of the main causes of bacterial foodborne disease in many developed countries. C. jejuni infection can also spread to the blood in individuals with AIDS, while C. lari is a known cause of recurrent diarrhea in children. C. fetus is a cause of spontaneous abortions in cattle and sheep, as well as an opportunistic pathogen in humans. This genus has been found to be part of the salivary microbiome. Campylobacter species generally appear as curved or comma-shaped rods, and are able to move via unipolar or bipolar flagella. They generally survive in environments with low oxygen. When exposed to atmospheric oxygen, C. jejuni is able to change into a coccal form They are positive by the oxidase test and catalase test. Campylobacter spp. are nonfermentative, and are best cultured at 42 °C. Survival at room temperature is poor, but they can survive for a short time at refrigeration temperatures – up to 15 times longer at 2 °C than at 20 °C. The bacterium dies out slowly at freezing temperatures and is heat sensitive: the cells are destroyed at temperatures above 48 °C. The symptoms of Campylobacter infection were described in 1886 in infants by Theodor Escherich. These infections were named cholera infantum, or summer complaint. The species was first isolated by Sir John McFadyean, of the Royal Veterinary College in London, in 1906. The genus was further defined in 1963. The genomes of several Campylobacter species have been sequenced, beginning with C. jejuni in 2000. These genome studies have identified molecular markers specific to members of Campylobacter. Additionally, several markers were found in all Campylobacter species except for C. fetus, the most distantly related species. Many markers were also found which were conserved only between C. jejuni and C. coli, indicating a close relationship between these two species. Similar studies have investigated the genes responsible for motility in Campylobacter species. All Campylobacter species contain two flagellin genes in tandem for motility, flaA and flaB. These genes undergo intergenic recombination, further contributing to their virulence.