What Is Listeriosis;Diagnosis,Treatment,Prognosis,Prevention

Listeriosis is an infectious disease of animals and man with exceptionally protean manifestations, including meningitis, dissemi­nated granulomas, lymphadenopathy, respiratory symptoms, and ill-defined acute febrile illness. It can produce abortion and fetal or neonatal death. The infection is caused by a gram-positive bacil­lus called Listeria monocytogenes and is world­wide in distribution.


Infection of the human being with Listeria monocytogenes was identified in 1929 by Nyfelt. The micro-organism was first charac­terized, however, by Murray, Webb, and Swann in 1926 during an epizootic among rabbits and guinea pigs. Subsequently the micro-organism has been identified as a cause of disease in fox, raccoon, goat, lemming, mouse, rat, hamster, pig, horse, cow,.dog, domestic fowl and wild birds, and other animals. L. monocytogenes is a gram-positive, non-spore-forming, aerobic or microaerophilic, motile bacillus. It ferments a number of sugars, with formation of acid but no gas.

It can be grown on nutrient agar or broth, preferably containing 1 per cent glucose, and produces beta hemolysis on blood agar. L. monocytogenes resembles Erysipelothrix rhusiopathiae and diphtheroids, but can be differentiated from these bacteria by its motility (best at 20 to 30° C.), its specific antigenicity, and its animal pathogenicity. Listeria regularly — and Erysipelothrix occasionally —produces puru­lent keratoconjunctivitis in rabbits following in­oculation into the conjunctival space, whereas diphtheroids do not.

Incidence and Prevalence.

Listeriosis in man and animals has been observed throughout the world. It has been recognized more frequently in humans in recent years, but its true incidence is not known. Confusion in bacteriologic differentiation accounts largely for inadequate recognition of listeriosis. In addition, the diverse manifestations of the dis­ease render it difficult to identify clinically.


Listeriosis may develop follow­ing inhalation, ingestion, or direct contact with contaminated food or animal products. The dis­ease is more common in persons living in rural areas. Although infection with Listeria occurs in many domesticated and wild animals, there are only rare instances of epizootics or outbreaks in animals other than man; Transmission of infec­tion from person to person probably does not occur. Women can carry

Listeria in the. vagina, and in­fection may be transmitted venereally. Whether or not man can be an asymptomatic carrier of Listeria under other’ conditions is not known.

Pathology and Pathogenesis

Human listeriosis is characterized by disseminated granulomas and focal necrosis or suppuration in involved tissues. Lesions may develop in liver, intestinal tract, skin, mucous membranes of the respiratory tract, lung, heart, spleen, lymph nodes, placenta, and brain. The fetus may be infected transplacentally through the umbilical vein, with production of septicemia. Debilitating diseases such as chronic infection and cancer predispose to the occurrence of listeriosis. Pregnancy may increase suscepti­bility to infection, but the disease in pregnant women may be less severe than in other persons. Administration of adrenal cortical steroids may also increase susceptibility to listeriosis.

Clinical Manifestations of Listeriosis.


Meningitis is the most commonly recognized form of listeriosis in the United States. It is characterized at onset by symptoms of headache, myalgia, fever, chills, nausea, vomiting, and photophobia, followed by the development of stiff neck, stupor, convulsions, somnolence, and, finally, death. The onset may be abrupt or gradual, and the initial symptoms may be those of gastrointestinal or respiratory ill­ness. Examination reveals manifestations of meningitis or encephalitis in varying degrees of severity. There may be pharyngitis, rhinitis, otitis media, neck rigidity, ocular palsy, and signs of depressed cerebral function. Leukocytosis is the rule, with granulocytosis and, occasionally, monocytosis, in the early_phase of the disease. The cerebrospinal fluid, with decreased sugar, elevated protein, and cell counts of 150 to 3000 per cubic ‘millimeter, is indistinguishable from that in many purulent meningitides. Early, the cells in the fluid may be principally granulocytes, but later there may be a predominance of mononuclear cells.

Febrile pharyngitis with cervical and general­ized lymphadenopathy can be caused by Listeria, and may be difficult to differentiate from infectious mononucleosis. Patients with this type of illness, however, may have an abrupt onset of fever, chills, headache, myalgia, conjunctivitis, macular rash, and sore throat. Lymph nodes in the neck and elsewhere may enlarge, and there may be hepatosplenomegaly. Blood leukocytes occasional­ly increase in number with a more or less pro­nounced monocytosis. The absorbed heterophil serologic test for infectious mononucleosis is negative, Listeria can be isolated from blood and pharynx, and there will be a rising serum agglutinin titer for Listeria.

Lymph node enlargement in the neck and else­where without respiratory symptoms may also be attributed to listeriosis. In addition, lymph node enlargement associated only with conjunctivitis may occur. Isolated acute upper respiratory ill­ness may be attributable to listeriosis, although for obvious reasons this diagnosis is seldom es-established. Chronic urethritis in men has been described, and possibly may be responsible for subclinical or occult infection, demonstrable by culture of the bacillus from bone marrow.Papular skin lesions associated with dissemi­nated listeriosis have been seen in infants, but adults may acquire primary cutaneous infection after direct contact with infected animal tissues.

Disseminated listeriosis in infants has been reported frequently in Europe, but infrequently in the United States. The disease may arise by transplacental infection of the fetus, causing abor­tion, fetal death, or serious illness within several days after birth. The disease is characterized by disseminated visceral granulomas and abscesses. When it manifests itself in infants a few weeks old, it often begins as a mild febrile illness with cough, coryza, gastrointestinal symptoms, and pneu­monia. Granulomas may be formed on the poste­rior pharyngeal wall. Granulocytosis and occa­sionally mononucleosis are present. Pleural and pericardial effusions may develop. Listeriosis has been reported as a common cause of neonatal death and fetal damage in Europe.

Listeriosis in pregnancy may be subclinical or may be associated with an acute febrile illness resembling influenza and occasionally pyeloneph­ritis; it is rarely severe. Its occurrence after the fifth month of pregnancy, however, is likely to affect the fetus seriously. A woman may become a vaginal carrier of Listeria and may possibly in­fect her infant at birth.

Disseminated listeriosis in adults has an abrupt onset with chill and fever. Meningitis can occur, as well as bacterial endocarditis. Blood cultures are usually positive, and there may be a consump­tive coagulopathy. This type of listeriosis is ob­served most often in patients with carcinoma or debilitating disease, and its aevelopment may have been facilitated by adrenal steroid therapy.

Listeriosis Diagnosis.

There are no pathognomonic clini­cal features of human listeriosis. The diagnosis rests on isolation of the micro-organism or rising agglutinin titers in the serum. It is likely that the recognition of listeriosis has been difficult because of the failure to differentiate Listeria from diphtheroid bacilli in culture. The isolation of micro-organisms resembling diphtheroids from infectious material or blood should alert one to the necessity for -further bacteriologic characteri­zation.

Listeriosis may resemble influenza, miliary tuberculosis, typhoid fever, mycotic infections, and several bacterial infections with septicemia. Infectious mononucleosis is most often confused with listeriosis in adults, for the two diseases may be clinically alike. However, listeriosis is infre­quently associated with monocytosis, does not produce a positive absorbed heterophil serologic test, and in systemic disease the bacillus can be isolated from blood, bone marrow, urine, or upper respiratory tract.    ,

Being A Doctor You Must Know Listeriosis Treatment.

Listeria monocytogenes is suscep­tible in vitro to-sulfonamides, penicillin, tetra­cycline, chloramphenicol, erythromycin, novo­biocin, and occasionally streptomycin. Penicillin is the drug of choice, but the tetracyclines and erythromycin are also effective. Treatment should be continued for a period of several days, depend­ing upon the characteristics of the disease.


Listeria meningitis has a fatality rate of 70 per cent in untreated patients. The fatality rate in treated patients has not been de­fined, but is considerably lower. The prognosis in adults with pharyngitis and lymph node enlarge­ment is good, whether treated or not, but meningi­tis may supervene. Recovery from meningitis may leave residual symptoms of central nervous sys­tem damage. Infection of the newborn is very seri­ous; the fatality rate and the incidence of congeni­tal defects are high. Untreated, disseminated listeriosis is usually a fatal disease.


Listeriosis must be regarded as a contagious disease of animals; prevention of hu­man infection would require elimination of ani­mal reservoirs. Pasteurization prevents trans­mission of the disease by contaminated milk. Animal products, including meat, should be declared unfit for consumption if the disease is found in slaughtered animals. Better recognition of the disease should clarify its epidemiology and indirectly facilitate control measures. There are no effective agents for immunization.

by Abdullah Sam
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