Approach

Treatment is based on individual characteristics such as pregnancy, immune deficiency, knowledge of responsiveness to each antibiotic, and specific site of infection.[1]

Prospective controlled trials to guide duration of treatment or drug choice are limited.[1]

gastroenteritis

Listeria gastroenteritis is typically self-limited and usually requires no antibiotic treatment.[1][2][6][38]​​[46]​​

Maintenance of fluid status and supportive treatment as needed are recommended.

If the patient is at increased risk of invasive disease or bacteremia (i.e., immunocompromised, age over 60 years, or pregnant), oral antibiotic therapy (e.g., amoxicillin, trimethoprim/sulfamethoxazole) may be started before blood culture results are known, depending on local practice. If Listeria is found in the blood culture, standard antimicrobial treatment for systemic infection is recommended (see below).[38]

Systemic infection (excluding meningitis/meningoencephalitis)

Ampicillin is considered the drug of choice in patients with systemic infection.[38]​​ Consideration of combination therapy with gentamicin for 14-21 days is indicated in bacteremia and severe infections.[7][38]​​​​ Gentamicin should be used with caution because of the association with renal failure in two retrospective studies.[7][47]

Penicillin allergy or intolerance

In patients with a penicillin allergy or intolerance, trimethoprim/sulfamethoxazole is effective.[1][2]​​[48] Meropenem may also be used, but it is associated with higher treatment failure and mortality rate.[49][50] Trimethoprim/sulfamethoxazole should be avoided during the first trimester of pregnancy due to its effect on folic acid metabolism.[2][7]

Brain abscess or endocarditis

Treatment duration for brain abscess is at least 6 weeks.[51][52]​​ Recommended duration of therapy for native valve endocarditis is 2-6 weeks, or at least 6 weeks in prosthetic valve endocarditis.[53]​ Duration of treatment in immunocompromised patients is variable and depends upon the individual case.

Consultation with specialists and adjunctive surgical considerations may be necessary for syndromes such as brain abscess or endocarditis. Repeat blood cultures may be done to help document and confirm clearance of infection in bacteremia and endocarditis. Repeat brain imaging may also help document improvement in CNS abscess treatment.

Meningitis/meningoencephalitis

It is estimated that meningitis occurs in 30% of patients with invasive listeriosis.[54] Delay in the initiation of antibiotic treatment is associated with poor outcomes.[55][56]

Empiric antibiotic treatment for suspected meningitis

For all patients with suspected meningitis empiric antibiotic treatment is recommended.[57] See Bacterial Meningitis.

Antibiotic treatment for confirmed meningitis

Ampicillin is recommended as first-line therapy.[1][38]​​​​ Gentamicin can be added but should be used with caution because of the association with renal failure in two retrospective studies.[7][47]​ If the patient is allergic to penicillin, trimethoprim/sulfamethoxazole is recommended.[57] The treatment course is 21 days.[1][57][58]​ See Bacterial meningitis.

Consultation with specialists and adjunctive surgical considerations may be necessary for syndromes such as brain abscess or endocarditis. Repeat blood cultures may be done to help document and confirm clearance of infection in bacteremia and endocarditis. Repeat brain imaging may also help document improvement in CNS abscess treatment.

Considerations during pregnancy

It is challenging to identify pregnant women who need testing and treatment due to the frequent presence of non-specific symptoms. However, due to the high mortality and morbidity risk for the fetus and neonate, there should be a low threshold for treating a systemic Listeria infection in pregnant women.[16][59][60]

There is limited evidence to define the optimal choice and duration of antibiotic therapy for pregnant women, and drug choice is based on clinical experience.[61] Penicillins are generally considered to be safe in pregnancy; amoxicillin or ampicillin are the drugs of choice.[7] Trimethoprim/sulfamethoxazole is an alternative in patients with a penicillin allergy or intolerance, however it should be avoided is unsafe during the first trimester due to its effect on folic acid metabolism.[2][7]

Aminoglycosides should be avoided unless the benefits outweigh the risks, in which case gentamicin may be used due to lesser likelihood of auditory or vestibular nerve damage than with other aminoglycosides. Gentamicin is used only rarely during pregnancy, and only in consultation with an infectious diseases specialist.

Alternatives such as meropenem, vancomycin, fluoroquinolones, macrolides, and tetracyclines may be used, but the benefits should outweigh any risks. If a safe second-line therapy is needed due to penicillin allergy in a pregnant woman with listeriosis, consult an infectious disease specialist, a fetal-medicine specialist, or both.[7]

The treatment approach should be individualized for each patient, and consultation with infectious disease specialists is recommended. Expert consultation is strongly recommended for pregnant women with systemic illness.

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