SN6 SHORT NOTE 5M ★ High-yield

Describe Campylobacter and Yersinia with their clinical features and complications.

Microbiology · 2nd Professional — Para-Clinical

Campylobacter

Campylobacter jejuni — a gram-negative, curved, S-shaped or "seagull wing" bacillus with a single polar flagellum and rapid darting motility
Microaerophilic (requiring 5% oxygen and 10% carbon dioxide) and thermophilic, growing optimally at 42°C — which is exploited for selective isolation on skirrow or Campy-BAP medium incubated at that temperature
Oxidase positive
A zoonosis — the reservoir is poultry above all, and also cattle, unpasteurised milk and contaminated water; it is one of the commonest causes of bacterial diarrhoea worldwide
Clinical features — a prodrome of fever and malaise, then severe cramping abdominal pain which may mimic appendicitis, followed by diarrhoea that is often bloody. Usually self-limiting over a week
The important complication is guillain-BARRÉ syndrome, arising through molecular mimicry between campylobacter lipo-oligosaccharide and peripheral nerve gangliosides; C. Jejuni is the commonest identified antecedent infection. Reactive arthritis may also follow
Treatment — rehydration; azithromycin if severe or prolonged, since fluoroquinolone resistance is now widespread from their use in poultry farming

CLINICAL PEARL

Campylobacter is a leading cause of Guillain-Barré syndrome, and the link is a chance resemblance. Its surface lipo-oligosaccharide happens to mimic human nerve gangliosides, so antibody raised against a diarrhoeal infection attacks peripheral nerve. The gut illness may be trivial or already forgotten when the weakness begins — which is why an ascending paralysis warrants asking specifically about diarrhoea in the preceding weeks.

Yersinia

Species	Disease and features
Y. Pestis — plague	Non-motile, showing bipolar ("safety pin") staining with Giemsa or Wayson stain. A zoonosis of rodents transmitted by the rat flea (Xenopsylla cheopis), in which a blocked proventriculus makes the flea regurgitate and feed repeatedly. bubonic plague gives a painful suppurating lymph node (the bubo) with fever; septicaemic plague gives shock and gangrene ("black death"); pneumonic plague is transmitted person TO person by droplets, is rapidly fatal, and is the form of greatest public health concern. Treated with streptomycin, gentamicin or doxycycline; notifiable internationally, and a category A bioterrorism agent
Y. Enterocolitica	Grows at 4°C, so cold enrichment is used and it multiplies in refrigerated food. Causes enterocolitis, and mesenteric adenitis with terminal ileitis producing "pseudo-appendicitis" — a well-recognised cause of a normal appendix at operation. Also reactive arthritis and erythema nodosum. Iron overload (as in thalassaemia on desferrioxamine) markedly increases susceptibility
Y. Pseudotuberculosis	Mesenteric adenitis; a scarlatiniform rash

Other Curved and Related Organisms

Vibrio parahaemolyticus — a halophilic vibrio requiring salt; causes food poisoning from raw or undercooked seafood, with an explosive watery diarrhoea; forms green colonies on TCBS as it does not ferment sucrose
Vibrio vulnificus — causes fulminant septicaemia with bullous skin lesions after eating raw shellfish or through a wound in seawater, particularly in those with liver disease or iron overload; mortality is high
Aeromonas and Plesiomonas — oxidase-positive water-associated organisms causing diarrhoea and wound infection
Helicobacter pylori — also a curved microaerophilic organism, but colonising the stomach rather than the intestine

Applied Aspects

Ask about diarrhoea in the preceding weeks in Guillain-Barré syndrome; campylobacter-associated cases tend to be more severe and to have a predominantly axonal pattern
Suspect Campylobacter or Yersinia in "appendicitis" that settles, and in a patient taken to theatre with a normal appendix and inflamed mesenteric nodes
Tell the laboratory to incubate at 42°C microaerophilically when Campylobacter is suspected; routine stool culture will not grow it
Plague persists in rodent reservoirs in parts of India, with outbreaks having occurred in recent decades; a cluster of severe pneumonia with haemoptysis in an endemic area demands immediate notification and isolation
Yersinia enterocolitica thrives in the refrigerator, which overturns the usual assumption about food safety, as does Listeria
Fluoroquinolone resistance in Campylobacter is a direct consequence of use in poultry, and is among the clearest illustrations that agricultural antibiotic use produces human clinical consequences

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