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.
Etiology.
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.
Epidemiology.
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.
Prognosis
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.
Prevention.
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.
