The immunocompetent mother suffers at worst a brief, flu-like febrile illness, but the fetus, whose defense system is still immature, becomes seriously ill. Depending on the stage of gestation, the fetus is either stillborn or born with signs of congenital infection. Diagnosis Listeria monocytogenes is implicated when monocytosis is observed in the peripheral blood as well as the cerebrospinal fluid. Early diagnosis may be obtained by finding pleocytosis with Gram-positive rods in a Gram stain of smears of the cerebrospinal fluid. Final proof is obtained by culture.
Serologic tests are highly unreliable.
Control Hygienic food processing and storage may reduce the risk of listeriosis. Even an attenuated living vaccine is dangerous for persons with impaired defenses, the proper target group. Completely avirulent live bacteria do not trigger an effective, cell-mediated immune response. Antimicrobial agents are the mainstay of treatment. Most of the common antibiotics, except cephalosporins, are active against L monocytogenes in vitro.