Symptoms of Listeria (Listeriosis)
Listeria monocytogenes infection produces several distinct clinical syndromes including stillbirth, neonatal listeriosis, meningitis, bacteremia, and localized infections, with symptoms varying significantly based on immune status and patient population. 1
Clinical Presentations by Population
Invasive Listeriosis (High-Risk Patients)
The most severe manifestations occur in immunocompromised individuals, pregnant women, and elderly patients:
- Meningitis and encephalitis - characterized by fever, headache, altered mental status, and neck stiffness 1
- Bacteremia/sepsis - presenting with fever and systemic signs of infection 1, 2
- Rhombencephalitis - a distinctive brainstem infection that mimics "circling disease" in animals 3
- Altered consciousness or stupor - particularly in elderly patients with multiple comorbidities 4
Pregnancy-Related Listeriosis
- Maternal symptoms may be mild or absent, but infection can lead to stillbirth, spontaneous abortion, or neonatal infection 1, 2, 3
- Early-onset neonatal sepsis results from maternal chorioamnionitis 3
- Late-onset neonatal meningitis occurs through passage through a colonized birth canal 3
Gastroenteritis Form (Milder Presentation)
In immunocompetent individuals, listeriosis typically presents as self-limiting gastroenteritis:
- Fever - common presenting symptom 2, 4
- Diarrhea - can be severe (up to 14 episodes in 24 hours reported) 4
- Nausea and vomiting - typically occurring within 7 days post-exposure 2
- Abdominal pain 4, 5
Important Clinical Characteristics
Variable Presentation Patterns
- Fever may be absent - approximately half of patients with listeriosis do not present with fever 5
- Headache, fatigue, and localized pain are common non-specific symptoms 5
- Laboratory findings include elevated white blood cell count, increased neutrophil ratio, elevated C-reactive protein and procalcitonin, and accelerated erythrocyte sedimentation rate 5
High-Risk Populations Most Affected
- Pregnant women have 10-17 times higher risk of invasive listeriosis 6
- Immunocompromised patients including those with HIV (especially low CD4+ counts), cancer patients on chemotherapy, organ transplant recipients on immunosuppressive therapy, and patients on prolonged corticosteroids 1, 6
- Elderly patients are more likely to present with altered consciousness and less likely to have neck stiffness or fever compared to younger patients 1
- Patients with chronic liver disease including cirrhosis or hemochromatosis 6
Critical Diagnostic Considerations
The time from symptom onset to diagnosis ranges from 5-36 days, contributing to frequent misdiagnosis or delayed diagnosis 5. The incubation period varies with the form of infection 7. Clinical suspicion must remain high in at-risk populations presenting with compatible symptoms, as listeriosis carries the third highest mortality rate among all foodborne infections 4.
Listeria is resistant to third-generation cephalosporins, making empiric monotherapy with these agents inappropriate in high-risk groups 1. This resistance pattern is a critical pitfall that can lead to treatment failure and poor outcomes if not recognized early.