Identification
Listeriosis is a mild febrile condition, but which may cause meningoencephalitis and/or sepsis in newborns and adults.
In adults
In adults the overall mortality rate reaches up to 30% being higher in people over 50 years of age. Adults may experience sepsis, meningitis or meningoencephalitis.
To the pregnant woman
The pregnant woman infection can cause:
- Premature birth
- Fetal infections
- Spontaneous abortions
The transmission shall be:
- Transplacental
- Contamination due to the infection of the vaginal level.
Pregnant women have greater susceptibility to Listeria monocytogenes due to progesterone-induced low cellular immune response. Listeriosis occurs primarily in the third trimester of pregnancy, but because of the lack of cultures in the fetal tissue resulting from abortion, there is the possibility of subdiagnosis of Listeriosis at the small age of pregnancy.
Symptoms
Listeriosis to the pregnant woman is manifested with flu-like symptoms:
1/3 of cases are asymptomatic. Even if the mother is asymptomatic at birth, may be born dead foetuses or infants with sepsis, who may develop meningitis during the neonatal period.
Listeria infection was associated with spontaneous abortions. The post partum evolution of mother is usually uneventful. Listeriosis in pregnant women is hard to diagnose due to non-specific clinical forms, however, any febrile episode occurring during pregnancy must be suspected and investigated for listeriosis by blood cultures (unless there is an evident cause).
In newborn
The mortality rate in the newborn reaches up to 50%.
The Listeriosis prognosis for the fetus is very poor, especially if the transmission takes place at a small age of pregnancy, when it balances with abortion.
In newborn there are frequently two distinct clinical forms.
- The early postpartum congenital Listeriosis manifests on average at 36 hours after birth. Newborns are premature and present septicemia (81-88%), respiratory distress syndrome or pneumonia (38%), meningitis (24%) and rarely, “Granulomatosis infant septicum”, characteristic for listeriosis. Most of the time they associate with chorioamnionitis. The prognosis is severe, with mortality of 75%.
- The late postpartum neonatal listeriosis occurs between 5 days and 2-3 weeks after birth, in newborn from asymptomatic mothers, it manifests with sepsis and meningitis and suggests a nosocomial transmission.
Diagnosis
Laboratory diagnosis in Listeria monocytogenes infections is bacteriological, directly, by isolating and identifying the bacterium.
To the pregnant woman
Due to the absence of digestive manifestations, the diagnosis of Listeriozei in pregnant women can be difficult. Blood counts can highlight leukocytosis, but this is an unspecified change.
The isolation and identification of the bacterium is made of blood, cerebrospinal fluid, amniotic fluid, placenta, fetal tissue, or contaminated pathological products: faeces, genital secretions, food, depending on the case. The Centre for Disease Control and Prevention in the United States of America (Centers for Disease Control and Prevention, CDC) does not recommend the use of contaminated pathological samples.
In newborn
In the case of suspicion of neonatal listeriosis will be collected meconium immediately after birth, prior to the occurrence of intestinal polymicrobial colonization.
Both the pregnant women and newborn, in the bacteriological laboratory diagnosis, are carried out the microscopic examination of smears in the pathological product, but in most cases identification of L. monocytogenes is difficult due to its intracellular location. The identification of the micro-organism after cultivation by suitable culture media will be carried out.
Two techniques can be used to achieve a faster result:
- Immunological technique, using monoclonal antibodies to identify monocytogenes according to somatic or caning antigens.
- The technique of identifying bacterial DNA by amplification reaction (Polymerase Chain Reaction, PCR).
After L. monocytogenes identification must be performed antibiogram to know the sensitivity to antibiotics, useful in determining the treatment.
An extremely important and sometimes overlooked aspect is that during pregnancy any febrile episode should be investigated by performing hemocultures. If the listeriosis is suspected, the laboratory physician should be informed of this (e.g. The colonies of Listeria monocytogenes can be confused with those of Corynebacterium Diphteriae).
If pregnant is febrile at birth, the bacteriological examination of the placenta and of the pathological products collected from the newborn will be performed.
An error commonly encountered in the current medical practice is the use of serological tests for the determination of anti L. IgG and IgM antibody monocytogenes for “screening and diagnosis of Listeriosis” in pregnant woman. There are “cross” reactions, false positive reactions, false negative reactions, and in this context it is not advisable to perform this test.
Infectious agent
Listeria monocytogenes, species-type of Listeria genus, pathogenic to humans and animals, is a Gram positive bacillus, optional intracellular (can be multiplied in macrophages, monocytes). Human infections are usually determined by serotypes 1/2a; 1/2b; 1/2c and 4b.
In Romania a circulating serotype is 1/2a, while 4b serotype is met in West.
About Corneliu Zaharia
