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Diagnosis of listeriosis
Last reviewed: 23.04.2024
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Diagnosis of listeriosis according to clinical and epidemiological data is difficult because of the polymorphism of clinical manifestations and the impossibility in some cases to identify the source of infection, so the crucial importance is acquired by laboratory diagnostics. Preliminary conclusion can be given on the basis of the results of a bacterioscopic examination of Gram stained smears of the sediment of the cerebrospinal fluid and amniotic fluid. However, Listeria spp. in Gram stained smears, cerebrospinal fluid should be differentiated from streptococcus cells, coryneocoaters and decolorized Haemophilus influenzae cells , which is not always easy due to their morphological similarity.
Finally, the diagnosis of "listeriosis" can be determined only by a bacteriological method. Listeria can be isolated from patients from the blood, spinal fluid, tonsils from the tonsils, punctate lymph nodes, swabs from the vagina and cervical canal, feces, purulent discharge from the eyes, synovial fluid, etc. When suspected of listeriosis sepsis, blood is sown, with meningitis and meningoencephalitis - the cerebrospinal fluid, with the disease of the newborns - meconium. A woman who has given birth to a dead child or with signs of a child's listeriosis is examined by the amniotic fluid, the placenta, separated by the birth canal.
In addition, it is possible to isolate listeria in smears from the oropharynx and feces of healthy people, which is regarded as asymptomatic carriage.
To isolate listeria from sterile biological substrates (blood, cerebrospinal fluid, amniotic fluid), no special media or culture conditions are required: listeria grow well on blood and chocolate agar, tryptose broth with glucose, in commercial vials for blood cultures. Other types of clinical material (detachable tonsils, eyes, female reproductive tract, feces) are contaminated with a diverse microflora, and the number of listeria in them can be negligible, and they can be isolated only through selective culture media or enrichment procedures.
The grown up colonies are identified as Listeria monocytogenes for a combination of morphological and biochemical tests.
Express diagnosis of listeriosis is based on the use of immunochemical methods (RIF, EIA), as well as PCR. Serological diagnosis of listeriosis is not detailed. In the determination of specific antibodies currently available methods, both false-negative and false-positive results of the research take place.
[Differential diagnosis of listeriosis
Differential diagnosis of listeriosis is carried out with various diseases, depending on the clinical form (version) of listeriosis. In particular, the anginosa-ferruginous variant must be differentiated first of all from the viral infectious mononucleosis Epstein-Barr, which is characterized by subacute development, the combination of exudative pharyngitis, tonsillitis, polyadenopathy (mainly the cervical group) and changes in the hemogram: neutropenia, a significant increase in the number of mononuclear cells, appearance of atypical mononuclear cells and plasma cells, antibodies of heterophilic (in particular, to horse erythrocytes) and to the capsid antigen of EBV. In some cases, adenovirus disease, cytomegalovirus infection, toxoplasmosis should also be excluded.
The gastroenteric form of listeriosis is distinguished from acute intestinal infections of a different etiology by a more severe course, the predominance of symptoms of intoxication over signs of gastrointestinal lesion, a simultaneous, as a rule, disease of a large number of people who used the same product.
The nervous form is differentiated from purulent (less often serous) bacterial forms of meningitis of another etiology.
The septic form of listeriosis is indistinguishable from clinical data from sepsis. Caused by other microbes, sometimes resembles typhoid paratyphoid diseases, iersiniosis, etc.
Differential diagnosis of listeriosis in pregnant women is carried out with banal infections of the urinary tract, and listeriosis of the newborns - from congenital cytomegalovirus infection, toxoplasmosis, streptococcal sepsis, syphilis. Presuming the presence of listeriosis in a pregnant woman allows "habitual" spontaneous abortions in an anamnesis, unmotivated fever, a critical drop in body temperature after abortion (spontaneous abortion, childbirth), the death of a child soon after birth.