Hui Gao, Ming-Ming Zhou, Juan-Juan Liu, Dan Chi, Hong-Qiang Shen?

1. Department of Clinical Laboratory, The Children's Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310051, China 2. Department of Infectious disease, The Children's Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310051, China

Keywords:Listeria monocytogene Meningitis Children

ABSTRACT Objective: To summarize the clinical characteristics and treatment outcome of 3 cases of Listeria monocytogenes (Lm) meningitis in immunocompetent children , improve clinicians' awareness of the disease. Methods: The clinical features and treatment of Lm meningitis in children admitted to Children's Hospital of Zhejiang University School of Medicine from January 2016 to May 2019 were analyzed retrospectively. We summarized related literatures, and compared the selection of antibiotics in children with Lm meningitis reported in cases. Results: All patients had fever, vomiting and other symptoms, CSF as purulent meningitis performance, Ampicillin is currently the first choice of treatment, while meropenem and Linezolid could be administered as alternative drugs for Lm meningitis. Conclusions: For children with meningitis, when the empirical antibiotics treatment fill, the possibility of Lm meningitis should be considered, and antibiotics that can effectively cover Lm should be adjusted in time.

1. Introduction

Listeria monocytogenes (Lm) is a Gram-positive and facultative intracellular pathogen, which is mostly transmitted to humans through contaminated food. Pregnant women, newborns, the elderly and patients with impaired immune function are susceptible population. Listeria infection mainly leads to central nervous system infection, endocarditis and septicemia in patients with impaired immune function [1]. We learned that the disease of Listeria meningitis rarely occurrs in the healthy and immunocompetent children from the published articles domestic and overseas. However, the condition of this disease changes rapidly, often accompanied by serious complications and high mortality [2]. Because of its characteristics, Listeria meningitis should be attracted enough attention by clinicians. The clinical symptoms of Listeria meningitis are similar to those of other bacterial meningoencephalitis, except that it has a prolonged course. Owing to the third generation cephalosporins don’t have an effect in the treatment, the choice of antibiotics is special[3]. Therefore, it is important to reinforce the knowledge of this pathogen, so as to find out the appropriate antibiotic treatment in time and achieve the desired effect. In this article, we reported 3 cases of Listeria monocytogenes meningitis in the healthy children, and discussed the clinical manifestations, diagnosis, treatment and prognosis of the disease. Due to the medication restriction to the children, the choice of antibiotics is different at home and abroad. So we reviewed the domestic cases of Listeria meningitis in the immunocompetent children (except newborn), and analyzed the use of antibiotics in order to provide help for clinical practice.

2. Clinical data

3 children (except newborn) diagnosed as Listeria monocytogenes meningitis were recruited from the Children's Hospital of Zhejiang University School of Medicine from January 2016 to May 2019. Based on the diagnostic criteria of the disease, the patient should have the clinical manifestations of central nervous system with at least one of the following requirements: ①Lm was found in CSF culture or smear; ②Lm was found in blood culture, and the number of leukocyte in CSF was more than 100 106/L or CSF protein is increased. The cure standards include no recurrence of clinical symptoms, normal CSF cytology and negative CSF bacterial culture 1 month after discontinuation of antibiotics.

All the 3 children with Lm were female, between 2 to 7 years old. They were all healthy previously, with no exact underlying diseases. The common clinical features are fever, vomiting and varying degrees of consciousness. 3 children showed different degrees of cervical resistance, and two of them were positive for pasteurization sign on the right side. Laboratory examination showed that Lm was positive in CSF culture of 3 cases, and Lm was also detected in blood culture of 2 cases. During the first lumbar puncture, the total number of CSF leukocytes was moderately increased in 1 case while it was significantly increased in 2 cases. And the monocytes were dominant in the elevated leukocytes. The protein level increased significantly in all 3 cases, and the chlorine and glucose levels were decreased in 2 cases except that the glucose level were slightly increased in Case 1. All 3 cases were diagnosed as bacterial meningitis at first, and cephalosporins were used before confirmation of pathogen. After admission, case 1 was initially given ceftriaxone, pimpiman and vancomycin for anti-infection treatment, and then adjusted to ampicillin and vancomycin for intravenous. The total treatment course for case 1 was 4 weeks. For case 2, ceftriaxone, vancomycin, meropenem, penicillin G and linezolid were given intravenously for 26 days. In case 3, ampicillin, meropenem and linezolid were respectively used for 46 days, 19 days and 18 days. All of the 3 cases were normal in the last examination of cerebrospinal fluid and no sequelae were seen in all 3 cases after 3-month followed-up.

3. Discussion

3.1 Literature review

In recent decade, there are few cases of Listeria meningitis in children in China. The Chinese journal full text database (CNKI), Wan Fang digital journal full text database (Wan Fang) and Chinese science and technology journal full text database(VIP)were respectively used to search the key words, including Listeria, children and meningitis. Among the papers published from January 2010 to June 2019, 8 articles with comprehensive clinical data reported 11 patients. In addition, there were 3 cases in this article. Thus, 14 cases were confirmed as patients with Listeria monocytogenes meningitis.The age of the patients ranged from 8 months to 14 years old and the median age was 4 years and 5 months. The gender ratio (male to female) was 5:2. All the patients had fever and headache. The percentages of patients with vomiting, neck stiffness and meningitis triad syndrome were respectively 43% (6/14), 57% (8/14), 29% (5/14). Among the 14 cases, 5 were positive in blood culture and 13 were positive in cerebrospinal fluid culture. The number of whole blood leukocyte was 18.1 (12.28, 28.54) 109/L, and neutrophils was elevated dominantly which increased to 79% (51.2%, 90.0%). CSF examination showed that the number of leukocytes was 834.2 (962252) 106/L while the percentage of multinuclear cells was 65% (18%, 92%). Furthermore, the levels of chlorine, glucose and total protein were respectively 112.5 (97,126) mmol/L, 2.13 (0.23, 5.43) mmol/L, and 1.4 (0.21, 4.67). Only one case of 14 patients adopted penicillin in the early treatment while all 14 patients used cephalosporin. and middle stage of 14 cases. The target antibiotic treatments and durations of the all 14 patients were shown in table bellow.

3.2 Clinical features, diagnosis and treatment

Listeria compromise 2 floras and 7 species, of which Listeria monocytogenes (Lm) is the main pathogenic bacterium. Lm is a Gram-positive and facultative intracellular bacterium, which can exist in foods with low water content and high salt content. Different from other foodborne pathogens, the growth temperature of Lm ranges from 1.5℃ to 45.0℃. This ability to grow and reproduce in extreme food environments makes Listeriosis difficult to control. The main symptom is febrile gastroenteritis if the healthy adults get infected with Lm, and it is self-limiting. Lm was mainly eliminated through the immune response of cells, especially T lymphocytes. Therefore, the deficiency of cellular immune function is the main predisposing factor of the disease, such as patients with malignant tumor, immune deficiency disease, long-term application of hormone or immunosuppressant, the presence of underlying diseasesand so on. Pregnant women, the eldly and newborns are the high risk population of Lm infection. The level of T/B/NK cell subsets and cytokine profiles were normal in all 3 children of our hospital. According to the data of patients in foreign literature published from 1990 to 2012, perinatal and non-perinatal infection separately accounted for 20.7% and 79.3%, and the total mortality of nonperinatal infection accounted for 25.9% [12].It was reported in China that Lm can rarely cause central nervous system infection in children with normal immune function. However, the disease often progresses rapidly and has a high mortality rate, which may be related to severe complications such as acute hydrocephalus [2]. A summary incorporating 92 patients infected with Lm in China from 2000 to 2009 showed that the number of perinatal and non-perinatal infection were respectively 54 and 38. The percentage of central nervous system infection was 27%, and the average mortality was 21% [13].

Table 1 Listeria meningitis in immunocompetent children

Due to the lack of specificity in clinical features and CSF examination of Lm meningitis, the misdiagnosis rate in early stage is high. Its clinical manifestations are similar to those of other bacterial or viral meningitis, including fever, headache, nausea, diarrhea and disturbance of consciousness, which are consistent with the three cases reported in our article. It is necessary to consider the possibility of central nervous system infection caused by Lm, in the case of prolonged illness and unsatisfactory effect of empirical anti infection treatment. At present, the positive Lm bacteria culture in blood and CSF is still the gold standard for diagnosis. In the patients diagnosed as Lm meningitis, the probability to detect the pathogenic bacteria in CSF smear by Gram staining is less than 50% [14]. Although CSF culture was positive in 3 children, no pathogenic bacteria was found in direct smear of CSF. Lumbar puncture is necessary for early diagnosis and evaluation of antibiotic treatment In consideration that the positive rate of blood culture of Lm meningitis is low. Castellazzi [15] summarized that only 5 of 16 cases were positive in blood culture after analysing the cases of Lm meningitis in children from 1996 to 2018. In our article, there was only 1 case with blood culture positive. Therefore, when there is no improvement after using the first-line antibiotic treatment, it is very important to repeat lumbar puncture for CSF examination in severe meningitis patients. In our group, lumbar puncture was performed 4-7 times in each one of the 3 cases. In most cases, CSF examination showed an increase in leukocyte and protein levels while a decrease in glucose levels. In this paper, among the classification of CSF leukocytes in children during the first test, mononuclear cells was dominated. The result was similar to other scholars' reports [16], and it may be detrimental to the early diagnosis of the disease. At present, the application of multiplex PCR technology abroad can identify the pathogen rapidly and provide great help for clinical effective diagnosis and treatment [17].

The third generations of cephalosporins and vancomycin are the first-line antibiotics for the treatment of bacterial meningitis, which are specific to most common pathogens. Although Lm is sensitive to most commonly used antibiotics, the cure rate is only 70%. Maybe it is because that Lm is an intracellular bacterium, the penetration of antibiotics is difficult. There are at least five penicillin binding proteins on the Lm cell membrane, among which pbp-3 has high affinity for penicillin, amoxicillin and ampicillin. But pbp-3 has no related binding site for cephalosporins, so it owns natural resistance to cephalosporins [3].

Let’s review the treatments of all 14 children infected with Lm in China again, we found that the antibiotics adopted in the domestic cured patients included penicillin G, ampicillin, linezolid, meropenem, vancomycin, amoxicillin/clavulanate potassium, rifampicin and compound neoformamine. Among the 14cases, 9 used combination antibiotics. Ampicillin or penicillin was the top priority for Lm meningitis treatment, and both of them could be used in combination with aminoglycoside antibiotics. They would act synergistically and enhance the bactericidal effect in vivo when the two antibiotics were used together [2]. Although drug sensitivity test in vitro confirmed that vancomycin was effective in anti Listeria, the failure rate for clinical treatment was high [18], which may be associated with the failure of vancomycin to pass the blood-brain barrier and reach the effective antibacterial concentration. In our article, only case 1 was cured with ampicillin and vancomycin. Cotrimoxazole had the equivalent antibacterial effect inside and outside the Lm cells, and had a significant effect on the treatment of refractory central nervous system listeriosis [19]. The patients who are allergic to penicillin can be treated with cotrimoxazole. It would have a better prognosis if the carbapenems was used alone or in combination with aminoglycosides. On the other side, some scholars believe that the combination of aminoglycoside antibiotics can significantly increase the risk of poor prognosis in patients with LM meningitis [20], so its application in the treatment of Lm infection remains controversial. Because of the medication restriction to the children in China, aminoglycoside antibiotics should be used with caution. All 3 patients recovered varily after the introduction of vancomycin and carbapenem, especially meropenem, so meropenem can be selected as a clinical drug. Leiti O et al [21] reported one patient of Lm meningitis who was allergic to penicillin and compound neoforman was cured through the treatment of linezolid and rifampicin. Though its condition was unstable in case 3, the patient's condition was controlled after adjusting the antibiotics in combination linezolid, which indicated that linezolid had a good curative effect. However, there is little data to support this opinion at present, and it needs further study to confirm. There is no optimum treatment plan and treatment course to recommend for Listeria meningitis. It is only suggested that the treatment course should last at least 2～3 weeks, and the withdrawal criterion of purulent meningitis should be met at the same time. In addition, the course of treatment for children with brain abscess should be extended to more than 6-8 weeks [22].

In conclusion, although Listeria meningitis in healthy children are rare, the clinicians should consider the possibility of Lm meningitis and promptly complete the cerebrospinal fluid examination when the patients have fever for a long time and fail to respond to the empirical anti-infection treatment.