Listeriosis

Listeriosis is an acute infection caused by Listeria monocytogenes, mostly in immunocompromised hosts—neonates, the elderly, pregnant women, and immunodeficient patients. Only L. monocytogenes of the three Listeria species causes human disease; it is most common in neonates and immunodeficient children.

Common Symptoms

Back pain; ataxia; diarrhea; pustule; pyothorax; abdominal pain; disorientation; chills; low fever; nausea

Causes and Pathogenesis

(1) Etiology: L. monocytogenes is a Gram-positive, facultatively anaerobic, non-spore-forming rod 1-3 µm long, motile with flagella; grows on many media, alkali-tolerant but acid-sensitive; optimal growth at 35-37°C, poor below 4°C; ferments sugars (acid without gas); catalase, methyl red, and V-P positive; forms a polysaccharide capsule in serum glucose peptone water; hemolytic on blood agar; in CSF it appears in pairs like cocci (mimicking pneumococci), and over-decolorized slides resemble H. influenzae or diphtheroids—biochemical identification is required. (2) Pathogenesis: The organism invades the gut, is internalized by small-intestinal microvillus epithelium, infects macrophages, and spreads systemically. Listeriolysin binds membrane cholesterol and kills macrophages. Like M. tuberculosis and Salmonella, it is intracellular; iron, catalase, superoxide dismutase, surface components, and listeriolysin affect virulence. Host killing depends on cell-mediated immunity: T-cell blast transformation occurs in spleen/regional nodes; passive transfer of T cells (but not serum) protects mice. Macrophages activated by sensitized T cells mobilize to inflammation and kill bacilli; corticosteroids/cytotoxic drugs suppress this and kill low-dose-infected animals. Maternal infection is mild but transplacental/intrapartum transmission causes severe fetal/neonatal disease; fetal pathology shows disseminated pinpoint yellow-white microabscesses (liver > spleen/adrenal/lung/GI/CNS) with necrosis and neutrophil/monocyte infiltration; meningitis shows purulent leptomeningitis/ependymitis with splenomegaly and focal hepatic/adrenal/pulmonary necrosis.

Treatment

Drug therapy, symptomatic treatment, supportive therapy

Preventive Measures

Listeriosis is food-borne: avoid raw milk, raw vegetables, and undercooked meat; immunocompromised persons should avoid contact with patients; treat maternal listeriosis to prevent fetal/neonatal infection; isolate cases in nurseries. Ampicillin or penicillin is preferred; gentamicin, tetracycline, chloramphenicol, erythromycin, kanamycin, and sulfadiazine are also effective.

Department to Visit

It is recommended to visit the Infectious Diseases department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.