Listeriosis is a zoonotic, clinically polymorphic infectious disease, occurring with a primary lesion of the system of mononuclear phagocytes, nerve tissue or in the form of anginal-septic form.
Brief historical information
The causative agent of the disease was first described by S. Khalfes (1911). He was identified by D. Murray et al. (1926) from sick rabbits and guinea pigs in the nursery of the University of Cambridge; In connection with the ability to cause pronounced monocytosis in the experiment, the causative agent received the species name monocytogenes, the name of the genus Listeria (in honor of Joseph Lister) suggested W. Peary (1927), who studied the causative agent of rodent epizootic in South Africa. In 1929, A. Nifellt isolated bacteria from a person with angina with high monocytosis. Later K. Bern observed cases of the disease caused by them in puerperas and newborns (1935).
Etiology
The causative agent is a mobile aspiring gram-positive bacillus Listeria monocytogenes, a type species of the genus Listeria. It can form a capsule, transform into L-forms and parasitize inside the cells, causing a slow latent development of the infection. Listerias are microaerophilic, unpretentious and grow on ordinary media even at room temperature. They have a set of somatic and flagellated antigens, allowing to distinguish among them 7 major serovars, many of which are divided into subtypes. The most common listeria 1-4th serovars. Bacteria are pronounced saprophytes and highly resistant to the environment. Low temperatures are well tolerated, as psychrophilic microorganisms are able to multiply at 4-6 ° C in various objects (soil, water, on plants, in carcasses and food products). Long endure 6-20% of the concentration of salt. The sun’s rays inactivate them for 2-15 days, 2.5% formalin solution or NaOH – after 20 minutes, bleach solution (100 mg of active chlorine in 1 liter) – after 1 h. At 62 “C die after 35 minutes, at 100 ° C – within 5-10 minutes. Sensitive to broad-spectrum antibiotics, although strains resistant to them are also known.
Epidemiology
The reservoir and sources of listeriosis infection are many species of wild and synanthropic rodents, as well as various objects of the external environment. The disease affects domestic and farm animals (pigs, small and cattle, horses, rabbits, less often cats and dogs), as well as domestic and decorative birds (geese, chickens, ducks, turkeys, pigeons, parrots and canaries). Listerias are found in foxes, minks, raccoons, arctic foxes, wild ungulates, birds, fish and seafood, in many natural environments. Particularly favorable environment for their reproduction are surface layers of poor-quality silage. The pathogen is excreted from the body with various secrets (urine, milk, blood, semen, cerebrospinal fluid, rectal mucus, amniotic fluid, etc.). The period of infectiousness of animals lasts indefinitely. An infected person can be a source of perinatal and neonatal pathology. Pregnant women and newborns can secrete the pathogen within 10-12 days after delivery.
The mechanism of listeriosis transmission is diverse (fecal-oral, contact, airborne, transplacental), the main one being fecal-oral. Animals become infected through water and feed infected with listeria from rodents or their carcasses. Bloodsucking insects, especially pastures mites, play a definite role in maintaining stationary foci of the disease. Being infected by rodents and other sick animals, they contribute to the spread of infection, transferring bacteria to other animals.
The mechanisms of infection of people are diverse. Most often, infection occurs by alimentary through infected water and food products of animal origin, especially in the absence of their reliable heat treatment and long-term storage at relatively low temperatures. Contamination by eating fresh vegetables is possible. The possibility of aerogenic infection occurring during the processing of animal raw materials (wool, bristles, leather, skins, feathers, down) has been established. Known contact transmission path, carried out through cuts and abrasions on the skin when ingested with various secretions of sick animals. The possibility of transmission of bacteria from person to person has been identified, cases of sexually transmitted infections have been described. Listeriosis is especially dangerous for pregnant women due to the perinatal transmission of the pathogen from mother to child (transplacentally or during labor). Cases of postpartum aerogenic, contact and food contamination of newborns from the mother, medical personnel or infected environmental objects are described.
The natural susceptibility of people to listeriosis is low. Diseases occur most often in elderly people, newborns, and people with immunodeficiencies. Post-infectious immunity is mild.
Major epidemiological signs. The disease has all the features of a saproz-infection, it is widespread. Most often it is found in areas with a temperate climate and soils rich in organic fertilizers. The spread of listeriosis contributes to large-scale human activities associated with the introduction of advanced technology of soil cultivation, construction of livestock farms, feed mills, centralized enterprises for the processing and sale of raw materials of animal origin, food warehouses and storage facilities. In Russia, 50-80 cases of listeriosis are recorded annually, which does not reflect the actual incidence rate. Possible sporadic and group diseases. The risk group includes pregnant women and newborns. Occupational morbidity is among workers in livestock and poultry farms, as well as primary processing shops in meat and poultry plants. The incidence is more often recorded in spring and summer. As nosocomial infections, listeriosis is most relevant to obstetric hospitals, where sporadic cases and outbreaks of listeriosis have occurred, and pregnant women and newborns are considered to be at risk.
Pathogenesis
The entrance gate of the infection can be mucous membranes of the gastrointestinal tract and respiratory tract, eyes, as well as damaged skin. With lymphogenous and hematogenous spread of pathogens, an acute febrile state occurs, and Listeria is fixed in the lymph nodes and internal organs – the tonsils, lungs, in the liver and spleen, kidneys and adrenal glands, the central nervous system, etc., where bacteria multiply.
The inflammatory process in the lymph nodes is accompanied by their increase, but suppuration does not develop. In severe cases of listeriosis, the disease acquires the features of listeriosis sepsis; at the same time, in the lymph nodes and internal organs (including the central nervous system), numerous small necrotic nodules (Listeriomas) are formed, which include Listeria, reticular and monocytic cells, nuclear detritus, altered polymorphonuclear leukocytes. During pregnancy, listeriomy can form in the placenta, which subsequently leads to infection of the fetus with the development of a generalized infection in it. The emergence of the disease contribute to immunodeficiency States and tumors.
Those who have been ill develop a persistent post-infectious immunity.
Clinical picture
Listeriosis can become acute, subacute, chronic, and abortive, usually prone to recurrence. The following main clinical forms of listeriosis are distinguished: anginal-septic, nervous, ocular-glandular, septic-granulomatous (in fetuses and newborns), mixed. There are cases of prolonged asymptomatic listeriosis.
Incubation period
Varies from several days to 1.5 months.
Angina-septic form
Meet most often. The main clinical manifestation is sore throat. It can be catarrhal or follicular, clinically indistinguishable from sore throat streptococcal etiology. Usually in such cases, the disease proceeds favorably for 5-7 days and ends in complete recovery.
With ulcerative-lysteric sore throat, body temperature rises to 38.5-39 “C, cough and runny nose are possible, sore throat is characteristic. Patients have a bright hyperemia of the oropharyngeal mucosa, an increase and loosening of the tonsils, the formation of membranous deposits or ulcers on them, covered lymph nodes. Regional lymph nodes are enlarged, painful on palpation. Ulcerative-film angina is characterized by changes in the hemogram – leukocytosis, increased ESR, and especially an increase in the number of mononuclear cells (up to 70% or more). Duration ioza in cases of a favorable course of 12-14 days.
However, ulcer-membranous and much less often follicular listeriosis angina with the progression of the process can lead to the development of sepsis, which is observed mainly in adults. High fever takes remittent nature, marked facial flushing, conjunctivitis, polymorphic skin rash, white plaque on the tonsils. Hepatolienal syndrome develops, in some cases mild meningeal symptoms appear. In the blood, pronounced monocytosis is retained. The outcome of listeriosis sepsis with timely and complete treatment is favorable.
Nervous form
Manifested in the form of listeriosis meningitis, meningoencephalitis, or brain abscess. The clinical characteristics of these conditions are not significantly different from the corresponding nosological forms of a different bacterial etiology. Monocytosis in peripheral blood is noted in the nervous form of the disease only in its early period, and further leukocytosis and granulocytosis are detected. The cerebrospinal fluid usually remains clear, the liquor pressure and protein content are elevated, the cytosis is of a mixed nature, and the glucose and chloride values change only slightly.
Damage to the peripheral nervous system can be observed – paresis and paralysis of certain muscle groups, polyradiculoneuritis.
In immunodeficiency states, including HIV infection, the nervous form of listeriosis manifests itself as an opportunistic infection.
Eye-glandular form
Rarely observed; it is usually caused by contact with infected animals. Patients noted an increase in body temperature, decreased visual acuity. Conjunctivitis develops with conjunctival edema and numerous follicles on it, eyelid edema, narrowing of the palpebral fissure, enlargement and slight tenderness of the parotid and cervical lymph nodes. The cornea remains unchanged. The disease occurs for a long time, from 1 to 3 months.
Septic granulomatous form
Observed in fetuses and newborns. During pregnancy, listeriosis can occur in erased and atypical forms or in the form of asymptomatic carriage and in such cases remains unrecognized. With intrauterine infection of the fetus in the early stages of pregnancy, its death or severe developmental abnormalities (hydrocephalus, microgyria, etc.) are possible.
Listeriosis of newborns is distinguished by a severe course. Manifested by high fever, respiratory and circulatory disorders: dyspnea, cyanosis, deafness of heart tones. Vomiting, mucous stools, rash of a roseolous-papular character are possible. With the development of purulent meningitis, death is most often observed. Clinically, listeriosis of infants is rarely recognized because of its similarity to other intrauterine infections.
In infants, listeriosis begins as ARI with fever, runny nose, cough, then small focal bronchopneumonia or purulent pleurisy develops. In some patients, exanthema of the maculo-papular nature, liver enlargement, jaundice, meningeal symptoms, sometimes convulsions, paralysis are noted. Characteristic monocytosis in the hemogram is rarely seen.
When recovering from this form of listeriosis in 15-20% of children, disorders of the peripheral nervous system and the central nervous system remain.
Chronic listeriosis
It is distinguished by the scarcity of clinical manifestations in acute exacerbations of the disease: short-term fever with catarrhal symptoms is observed, quite often dyspeptic disorders or sometimes symptoms of chronic pyelonephritis.
Differential diagnostics
Complicated due to the clinical polymorphism of listeriosis and the absence of pathognomonic clinical signs. The disease is differentiated from angina, cocci etiology, infectious mononucleosis, acute respiratory viral infections, purulent meningitis, and blood diseases. Various clinical forms of listeriosis in most cases combine the predominant lesion of the system of mononuclear phagocytes.
Laboratory diagnosis
Often in listeriosis, especially in its anginal-septic form, attention is paid to a large number (up to 60-70%) of monocytes in peripheral blood.
Depending on the form of the disease, bacteriological examination of blood, cerebrospinal fluid, mucus from the nasopharynx and pharynx, detachable conjunctiva, punctate lymph nodes, amniotic fluid, placenta, etc., as well as various biological material taken from the bodies of the dead are carried out.
Crops are recommended to do in the first 7-10 days of illness; blood (10 ml) and cerebrospinal fluid (2-5 ml) are seeded in 100-150 ml of glucose, glucose-liver or glucose-glycerin broth; incubated at 37 ° C for 3 weeks. When seeding on glucose-blood agar, typical colonies (transparent or hornlike) are selected, giving hemolysis. You can also sow on tryptose agar and view the plates under a microscope with oblique illumination — the daily colonies of Listeria are blue-green in color.
Apply RA with listeriosny diagnosticum, RNGA and RAC with their formulation in paired sera. Possible false-positive results due to the antigenic relationship of listeria and staphylococcus. Perhaps the use of MFA and biological samples in white mice, keratoconjunctival samples in rabbits.
Complications
In anginal-septic form of listeriosis, endocarditis may develop. In chronic listeriosis, exacerbation of the disease in weakened individuals and immunodeficiency states can lead to the development of a severe generalized septic process.
Treatment
Conducted in accordance with the clinical form of listeriosis. In etiotropic therapy, tetracycline 300 mg 4 times a day, doxycycline 100 mg / day (200 mg on the first day), and erythromycin 30 mg / kg / day by mouth in 4 doses are effective. For meningitis and meningoencephalitis, benzylpenicillin is prescribed sodium salt of 75-100 thousand U / kg intravenously every 4 hours. Alternative drugs are clarithromycin, ciprofloxacin. Antibiotics are prescribed throughout the febrile period and from the 7th to the 21st day of apyrexia, depending on the severity of the disease. Pathogenetic therapy is carried out according to generally accepted principles. In the eye-glandular form, a 20% solution of sodium sulfacyl (albucid), 1% hydrocortisone emulsion is applied topically.
Epidemiological surveillance
Includes analysis of the incidence of animals and people, tracking infection by the pathogen of environmental objects, identifying risk groups and factors contributing to the spread of infection in both domestic and hospital conditions, regulation of L. monocytogenes for raw materials and animal products, poultry and fish as hygienic requirements for the quality and safety of food products and the implementation of current supervision practices. In the surveillance system for the planning, implementation and evaluation of the effectiveness of measures to combat listeriosis, it is necessary to make wider use of serological research methods.
Preventive actions
The variety of sources of listeriosis and the availability of wide possibilities of infection of the population determine the need for a common complex of veterinary-sanitary and sanitary-hygienic measures in settlements, at various facilities related to animal husbandry, storage and processing of raw materials and meat products. Deratization measures, protection of water sources and catering facilities from rodents are also necessary. In farms (livestock farms, farms, departments, herds), unfavorable for listeriosis, conduct a general inspection of animals and the rejection of animals, isolation and treatment in accordance with the relevant instructional and methodological documents. Milk obtained from sick animals is boiled, and leather and fur raw materials are disinfected. For the prevention of listeriosis in pregnant women, complete exclusion from the diet of soft cheeses such as Camembert, Roquefort, sheep cheese, as well as food products of the fast food industry like sausages “hot dog”, hamburgers, etc., have not been recommended for long-term heat treatment before consumption. Measures of specific prophylaxis are not developed.
Activities in the epidemic outbreak
Hospitalization of patients is carried out according to clinical and epidemiological indications. The discharge from the hospital is carried out after clinical recovery and cessation of the excretion of Listeria, established on the basis of bacteriological studies. All patients are subject to follow-up in accordance with the instructions and guidance documents. Disinfection is carried out according to the same scheme as in typhoid fever. In the outbreak, they reinforce measures for the destruction of rodents and the protection of residential and industrial premises from them. Separation and emergency prevention in relation to contact is not carried out.