Listeria monocytogenes infections are described in ten confirmed cases encountered over a period of four years. Six adults had central nervous system involvement (meningitis, meningoencephalitis, encephalitis or cerebral abscess), with simultaneous blood stream invasion in four, including evidence of endocarditis in one. Two patients had neurologic manifestations without septicemia, another had septicemia without neurologic involvement. Two premature infants were born with the syndrome of granulomatosis infantiseptica. A primagravida was found to have a listeric uterine infection at term but delivered a viable infant free of infection. Listeria has a predilection for patients suffering from lymphoreticular diseases. Factors contributing to infection are associated immunologic deficiency states and treatment of the underlying diseases with cytolytic drugs and corticosteroids. Premature infants, pregnant women, diabetic and alcoholic subjects are also prone to listeriosis. The infrequent diagnosis of listeric infection is partially due to mistaking the isolated organism for a contaminating diphtheroid. A short gram-positive rod that is hemolytic and motile, recovered from the blood or spinal fluid of a symptomatic patient, is for all practical purposes Listeria. Definitive and differential diagnosis rests upon six additional bacteriologic characteristics, namely, positive catalase and methyl red reactions; acid fermentation of glucose and salicin but not mannitol; and the induction of conjunctivitis when instilled into the conjunctiva of a rabbit. L. monocytogenes is sensitive to a wide variety of antimicrobial agents but strains of Listeria may be encountered which are resistant to penicillin, streptomycin, methicillin, kanamycin and sulfonamides, and moderately resistant to penicillin, oxacillin, methicillin, cephalothin and lincomycin. Both susceptibility testing and clinical experience indicate that tetracycline is the drug of choice. Treatment with this antibiotic should be started immediately whenever the possibility of listeric infection is entertained. Person to person transmission has rarely been documented and isolated cases of listeriosis are the rule. In most instances the source of infection is not found although a large reservoir of infection is known to exist among animals. Rural cases predominate in some countries but most cases in the United States are reported from urban areas. Unpasteurized milk is the only food for which a relationship to human listeriosis has been proved. © 1968.
