Listeria infection

Etiology

• Species L. monocytogenes• Gr+• Aerobic• Motile with its 1-5 flagella • Non-spore forming• Rodlike

Transmission • L. monocytogenes infects many domestic and wild animals • Transmitted to humans by eating infected animals or animal

products

Pathogenesis

• Enters the human body by ingesting the contaminated food• Has virulence factor listeriolysin O that allows it to escape the

phagolysosomes of macrophages and avoid intracellular killing

Symptoms of Listeriosis • Mild symptoms: • Fever• Muscle aches • Nausea • Diarrhea

• Severe symptoms:• Meningitis • Mental changes• Brain abscess • Death

People at risk of infection • Pregnant women• Fetus and neonate• Elderly and immunocompromised

Infection in pregnant woman

• Usually occurs in third semester when the cell-mediated immunity decreases

• The bacteria infects the fetus and 22% of these infections result in neonatal death

• Surviving babies are often born prematurely with active infection

• Prophylaxis: pregnant women should avoid milk, soft cheeses, butter and deli meals

Infection in fetus and neonate

• Infection is acquired in utero • Can also be contracted from an asymptomatic mother, with

vaginal colonization with Listeria during vaginal birth• This type of infection results in neonatal meningitis presenting

about 2 weeks post-partum• Listeria monocytogenes causes 20% of all neonatal meningitis

Infection in elderly and immunocompromised

• Is the second most common cause of meningitis, after Pneumococcus, in people over 50 years old

• Immunocompromised patients at risk are:• Patients with lymphoma • Patients receiving organ transplantation• Patients on corticosteroids• Patients with AIDS

Infection in immune component hosts

• Listeria monocytogenes is a facultative intracellular organism• In immune component host it is not likely to cause infection

due to cell-mediated immunity

Diagnosis • Confirmed by lumbar puncture• Cerebrospinal fluid analysis reveals a high number of

neutrophils, increased protein level, decreased glucose level • Positive gram stain showing gram-positive rods

Treatment • Fluid 0,9% NaCl• By antibiotics:• Ampicillin

• Children: 75 mg/kg/day• Adults: 150 mg/kg/day

• Trimethoprimsulfamethoxazole • Children: 2x100mg/day• Adults: 2x400mg/day

Prevention • Cook food properly at high temperature• Treating/pasteurizing fluids • Avoid food or fluids that might have been in contact with

animals or human waste

Sources • http://www.medicinenet.com/listeria/article.htm• Lange: medical microbiology• Andreas Russ: Arzneimittel pocket