3. Discussion
In this case report, a premature infant was infected in utero with L. monocytogenes from her mother. The mother experienced headaches at 6 months gestation, then developed symptoms of fever and abdominal pain at 33 weeks. These symptoms were consistent with maternal antenatal symptoms presented in a report of 12 cases of perinatal listeriosis: mothers had clear neutropenia during their illness, which was also present in the case reported here [5]. Therefore, cases of antepartum fever with abdominal pain should be treated cautiously.
The infant in this case had early onset listeriosis; she was born prematurely at 33 weeks and died 72 hours after birth. The clinical features were typical of early-onset neonatal listeriosis, including preterm delivery and sepsis at birth [6]. The causes of death included sepsis, secondary meningitis, necrotizing enterocolitis, and septic shock.
We administered emergency treatment for perinatal infection, but the L. monocytogenes was not detected early enough. We made the judgment that neonatal infection was likely on the basis of the clinical symptoms of neonatal respiratory distress, lethargy, and poor responsiveness. Because most of the pathogenic bacteria responsible for early neonatal sepsis are Gram-positive cocci [7], we administered flomoxef because of its wide antibacterial spectrum and safety [8]. After L. monocytogenes was suspected, antimicrobial therapy was switched to amoxicillin and sulbactam combined with imipenem/cilastatin. Although the infant died 10 hours later, the mother improved significantly within 1 to 2 days of treatment with piperacillin and sulbactam following the identification of L. monocytogenes in the infant’s blood culture. Generally, early diagnosis of mother-to-child Listeria infection is challenging. In this case, the mother’s blood cultures were twice as negative. In a retrospective case study, only 36% of 11 pregnant women with perinatal listeriosis had positive blood cultures [9]; thus, false negatives are very common. We speculate that the high false negative rate may be related to the collection conditions of blood cultures. In principle, blood samples should be collected at the patient’s body temperature above 38.5 °C without using antibiotics and submitted for testing within 30 min. However, this condition is not easy to achieve in most situations.
Several factors may explain the different results of treatment of the infant and mother with antibiotics effective against Listeria . Most importantly, neonatal immune function is poor, the disease progresses faster, the complications are critical, and the mortality rate is high. Moreover, in clinical diagnosis, a negative blood culture should not be interpreted as non-septicemia. When neonatal infection progresses rapidly and accurate results of blood cultures are unavailable, empirical diagnosis is more important. Ampicillin can simultaneously cover L. monocytogenes, beta-hemolytic streptococci, andE. coli , the latter two bacteria are the most common and harmful pathogens associated with neonatal early-onset sepsis [10].
In the treatment of this case, a multi-pronged approach was applied in addition to antimicrobial therapy that included the use of an incubator, sterilization, ventilator-assisted breathing, heart-brain protection, and so on. These interventions are vital to ensure the operation of the organs and maintain circulation. Before the onset of complications (e.g., 24 hours after birth, Table 1), the infant’s condition improved slightly.
There were some limitations to this retrospective case report that require clarification. First, Listeria shows placental tropism and placental specimen culture is the most sensitive method for diagnosing neonatal listeriosis [11]. However, the placenta was not cultured in this case and the results of the mother’s blood culture were twice negative. In this case, the infant was born with symptoms of sepsis, and the mother’s improvement following the administration of antibiotics effective against Listeria along with negative blood cultures was sufficient to demonstrate that the infection was congenital. The failure to identify listeriosis earlier is a major factor preventing the rescue of newborns. Second, without detailed epidemiological information, including the mother’s medical history, it was not possible to determine the source of Listeria infection.
The diagnosis of neonatal Listeria infection has three characteristics. No specific clinical symptoms. The diagnosis of biological samples has different degrees of false negatives [12]. In addition, newborns have experienced circulatory failure, shock, and death before Listeria can be isolated and identified.
Considering our experience with this case, we conclude that although bacterial culture is vital for the diagnosis of listeriosis [13], clinicians should not wait for final confirmation of the pathogen when the infant is in critical condition. Instead, clinicians should assess the medical history of the mother and the infant at the same time and monitor changes in their conditions. Bacterial culture and identification results should be evaluated in combination with clinical experience. Clinicians should remain alert to the possibility of specific bacterial infections and be ready to change antimicrobial therapy in a timely fashion.
4. Conclusions
This pathological report demonstrates that monocytosis caused byListeria monocytogenes poses a significant threat to the lives of newborns. The bacterium can cross the placental barrier, leading to neonatal listeriosis when transmitted from infected mothers. This disease progresses rapidly, has a poor prognosis, and carries an extremely high mortality rate. Furthermore, the empirical use of cephalosporins and carbapenems has shown resistance. These findings highlight the importance of early identification of the pathogen in the treatment of neonatal listeriosis. However, blood culture identification is associated with long turnaround times and a high false-negative rate, necessitating the establishment of an early and sensitive comprehensive testing system for this bacterium. It is particularly crucial to strengthen screening for high-risk pregnant women during the perinatal period. More importantly, healthcare professionals should increase their awareness and attention to rare pathogens that can traverse the placental barrier.
Author Contributions:Xiaoyu Chen - project administration; Jing Li - visualization;Ying Lu, Shuyue Li and Qi Li - original draft preparation; Yakun Luo - review and editing; Fan Wang - original draft preparation;Qingliang Shao - original draft preparation, funding acquisition and supervision.
Funding: This research was funded by Bethune Medical Science Research Foundation (grant number: SCE154EN), Postdoctoral Scientific Research Developmental Fund of Heilongjiang Province of China (grant number: LBH-Q18090).
Conflicts of Interest: The authors have declared that no conflict of interest exists.