Campylobacter jejuni infection

Previous authors: M L VAN DER WALT

Current authors:
E DI GIANNATALE - Head of the Bacteriology Department and National Reference Laboratory of Campylobacter, Microbiologist, via Campo Boario, Teramo, 64100, Italy

GENERAL INTRODUCTION: AEROBIC/MICRO-AEROPHILIC, MOTILE, HELICAL/VIBROID GRAM-NEGATIVE BACTERIA

Introduction

Campylobacter jejuni is a common human pathogen and an important cause of diarrhoea worldwide.^{28, 77, 89} It is isolated frequently from the intestine of healthy animals and considered to be part of the normal intestinal flora. Birds and domestic ruminants play an integral role in the ecology of C. jejuni and may serve as a source of infection resulting in outbreaks of disease or sporadic cases in humans.^{34, 62} Poultry and cattle are the most important animal reservoirs. Infection in humans can be acquired via multiple routes, including direct contact with these animals, consumption of contaminated animal products, and environmental contamination such as water.¹⁷ Campylobacter jejuni alone, or in combination with other pathogens, may cause enteritis and diarrhoea in calves⁸⁷ and sheep,^{83, 91} but its significance in such cases should be interpreted with care.^{64, 97} For many years it was considered to be the aetiological agent of ‘winter dysentery’ (caused by bovine coronavirus), characterized by profuse watery diarrhoea of sudden onset and short duration in adult cattle.^{57, 76} Campylobacter jejuni is also an occasional cause of mastitis in cattle^{41, 42, 52, 61} and abortion⁹⁰ in cattle, sheep,^{20, 40, 92} goats⁵ and blesbok (Damaliscus dorcas).⁶

Aetiology

Campylobacter jejuni is micro-aerophilic and grows optimally in an atmosphere containing 5 per cent O₂, 10 per cent CO₂ and 85 per cent N₂ and at 37-42°C. It is   unable to ferment or oxidize carbohydrates.   The organisms are slender, spirally curved, Gram-negative rods 0,2 - 0,8 μm wide and 0,5-6,0 μm long. They vary in morphology and may have an increased number of spirals or may be gull-wing-shaped, while coccoid forms occur in older cultures in response to deleterious conditions. The bacteria are motile, the movement being characteristically darting or corkscrew-like. Motility is caused by polar flagella at one or both ends of the organism^{51, 81} that propel it through viscous solutions, such as the mucus layer of the gastrointestinal tract.⁵³

Campylobacter jejuni can survive in a moist environment for several weeks at 4 °C and maintain its metabolic activities³⁹ but it tends to die more rapidly at ambient temperatures. It survives in bovine faeces for at least 20 days at 25 °C and for eight weeks at 4 °C.¹⁹ In cows’ milk or water C. jejuni survives for two to five weeks when kept at 4 °C.^{72, 94} The bacterium is sensitive to dehydration at room temperature,²⁸ while freezing drastically reduces the number of organisms on meat.⁸⁴ It does not proliferate below 30°C,⁶⁸ perhaps due to the absence of cold shock proteins.³⁹

The organism is inactivated by iodine udder washes within eight minutes and is rapidly killed by hydrochloric acid at pH 2,3.¹¹ Campylobacters do not survive the temperatures of pasteurization:  inactivation in skimmed milk and beef cubes requires 50 seconds at 92 °C and 40 seconds at 95,7 °C, respectively.¹⁹

Epidemiology

The organism is widely distributed particularly in avian species, farm animals, pets such as dogs and cats, and humans. Food animals, especially poultry, are reservoirs of C. jejuni. Fifty to 80 per cent of cases of campylobacteriosis in humans are attributed to chickens as the source of infection.^{7, 22, 28, 65, 80}

Campylobacter jejuni is shed in the faeces of both diarrhoeic and healthy animals.^{63, 70, 86} Faecal shedding by healthy animals is intermittent and only few organisms are shed. There appears to be no difference in the carrier rates between healthy cattle, horses, pigs and dogs. Carrier rates do vary within a species and between animals from different sources.⁶⁹

Organisms are commonly present in the rumen of calves and less so in adult cattle. In healthy sheep C. jejuni is frequently carried in the intestinal tract.^{1, 79}

Isolation levels are five times higher from fresh than from frozen tissue.   Refrigeration or frozen storage alone do not add a significant safety margin and therefore poultry contaminated with C. jejuni can cause infection if not properly handled and sufficiently cooked.¹⁰ In humans it is estimated that handling and consumption of broiler meat may account for 20 to 30 per cent of human cases of campylobacteriosis.²² Apart from chicken products, infection may follow consumption of untreated surface water, unpasteurized and incompletely cooked milk,³⁷ and other contaminated food products such as meat from farm animals.^{24, 78} Carcasses of feedlot-fed cattle are more likely to be contaminated than those of pasture-fed cattle.²⁷ Apart from milk no other dairy products act as a source of C. jejuni. ³⁷

Flies may be important in the transmission of the bacterium, particularly to humans. On poultry and pig farms, 50 and 43 per cent respectively of Musca domestica may contain C. jejuni.⁷³

Pathogenesis

Although C. jejuni mainly colonizes the gastrointestinal tract in animals, it may cross the intestinal epithelial barrier leading to bacteraemia.⁸⁵ In pregnant animals C. jejuni may reach the gravid uterus, resulting in subsequent placentitis, foetal infection and abortion.^{14, 79}

During a brief period...