ABPC12g ± GM
Listeria monocytogenes is susceptible to common antimicrobial agents, such as ampicillin, penicillin, gentamicin, and trimethoprim-sulfamethoxazole, and in vitro resistance to these drugs is rare. Ampicillin or penicillin G are the drugs of choice. However, these antibiotics demonstrate delayed in vitro bactericidal activity at concentrations attainable in the cerebrospinal fluid (CSF). As a result, gentamicin is often added to achieve synergy for listerial central nervous system (CNS) infections, endocarditis, and infections in immunocompromised patients. Drug doses are described above．
●Penicillin-allergic patients can be skin tested and desensitized if necessary or treated with trimethoprim-sulfamethoxazole. The usual dose ranges from 10 to 20 mg/kg (based on the trimethoprim component) intravenously (IV) per day divided every 6 to 12 hours, with the higher end of the dosing range used in patients who are severely ill.
●Early diagnosis and initiation of appropriate antibiotic therapy are important.
●All patients with invasive listerial infection should be treated with antibiotics, since much higher mortality rates have been reported in untreated patients.
●Among patients treated with immunosuppressive drugs (eg, because of renal transplantation), we recommend decreasing the level of immunosuppression if there is not a prompt clinical response to initial antimicrobial therapy (Grade 1C).
Type of infection
●For patients with listerial CNS infection, bacteremia, endocarditis, or infection in immunocompromised hosts, we treat with ampicillin. We suggest adding gentamicin to achieve synergy (Grade 2C).
●For neonates with listerial infection, we suggest treatment with ampicillin and gentamicin (Grade 2C).
●Among immunocompetent patients with listerial febrile gastroenteritis, we suggest not treating since it is almost always a self-limited illness (Grade 2C).
●We suggest that oral ampicillin or trimethoprim-sulfamethoxazole be given for several days in immunocompromised, pregnant, or older adult patients with listerial febrile gastroenteritis, particularly if they are still symptomatic or have ingested a food implicated in an outbreak (Grade 2C).
●Among pregnant women with isolated listerial bacteremia, we suggest treatment with ampicillin alone (2 g IV every four hours) (Grade 2C). Although trimethoprim-sulfamethoxazole is an alternative in penicillin-allergic patients, it should be avoided in the first trimester, since folic acid metabolism may be affected, or the last month of pregnancy to avoid kernicterus in the fetus. Vancomycin is an alternative agent among pregnant patients who become infected during a period when trimethoprim-sulfamethoxazole cannot be given and who have a history of serious allergy to penicillin but cannot be desensitized.
●In immunocompetent patients, we suggest a minimum of two weeks of antibiotic therapy for bacteremia and two to four weeks for CNS infection. In immunocompromised patients, we suggest three to six weeks for bacteremia and four to eight weeks for CNS infection. The longer duration particularly applies to patients with cerebritis or brain abscess.
●When gentamicin is added to ampicillin for synergy, we suggest it be continued until the patient improves (usually 7 to 14 days) or, in poor responders, for up to three weeks if there are no signs of nephrotoxicity or ototoxicity.
●After antibiotics are discontinued, the patient is monitored for signs of clinical relapse. We suggest that end-of-treatment CSF examination is not necessary if a previously negative CSF culture was documented while on therapy.
●The response to therapy is monitored clinically (temperature, clinical signs, and symptoms). In patients who remain persistently febrile or who have other signs or symptoms suggesting a poor response after several days of therapy, we repeat blood cultures and, in patients with CNS infection, CSF cultures and, if initially abnormal, magnetic resonance imaging (MRI).
●Patients with no underlying disease generally do well. In comparison, the mortality rate is high in patients with an underlying disease that predisposes to more serious infection (eg, malignancy, diabetes mellitus, or renal transplantation). CNS infection in immunocompromised patients carries a particularly high mortality. In addition, survivors of cerebritis (particularly cerebral abscess) or rhombencephalitis have a high rate of persistent neurologic sequelae.