The curved bacterium hiding on nearly half of packaged Canadian chicken
Campylobacter is one of the world's commonest bacterial causes of stomach upsets, and raw or undercooked poultry is a major route in. Canadian testing found it on nearly half of packaged chicken breasts. Stomach acid usually protects people, so it typically takes more than 10,000 of the spiral-shaped cells to cause illness.
The name joins Greek for curved with Latin for rod, describing slender comma- or S-shaped cells that usually whip themselves along with flagella at one or both ends. They prefer low oxygen, and the main human culprit, C. jejuni, grows best between 37 and 42 degrees; stressed by air, it can round itself into a ball-like form. Many animals carry the bacteria harmlessly in their guts, while C. fetus causes fertility problems in cattle. Genomes are compact, between 1.60 and 1.90 million base pairs, but studded with hypervariable regions that differ sharply between strains.
Theodor Escherich spotted the organisms in 1886 in stool samples from infants who had died of a diarrhoeal illness he called cholera infantum. For decades they were lumped in with Vibrio bacteria, until Sebald and Veron gave them their own genus in 1963 on the basis of shape and oxygen needs. C. jejuni's genome was sequenced in 2000. Viruses that attack Campylobacter were first isolated from cattle and pigs in the 1960s and are now studied as a possible alternative as antibiotic resistance spreads.
Illness begins one to three days after exposure, with cramps, fever and diarrhoea that can be bloody, and usually clears in five to seven days. Most strains make a toxin that halts cell division in the gut lining. Rarely the bacteria enter the bloodstream, especially in older or immunocompromised people; a review of 2,480 such patients found about 5 per cent died. Infection is also the commonest trigger of Guillain-Barre syndrome. Because antacids neutralise stomach acid, people taking them can fall ill from smaller doses.
Contaminated water causes big outbreaks: in 2016 more than 8,000 people in Havelock North, a New Zealand town of about 13,000, fell sick, and in 2019 horse faeces in a Norwegian reservoir sickened around 2,000 in Askoy. An Italian survey found high resistance to ciprofloxacin but low resistance to macrolide antibiotics.
Source: Campylobacter
