Epidemiology, clinical and imaging features of rhombencephalitis caused by L. monocytogenes. A retrospective observational study

INTRODUCTION

To date, few studies have explored the specific risk factors of patients with listeriosis who develop rhombencephalitis, and there is insufficient information regarding imaging findings and clinical symptoms in patients with this disease. This work aimed to analyze the imaging findings associated with L. monocytogenes rhombencephalitis in a cohort of patients with listeriosis.

MATERIALS AND METHODS

We conducted a retrospective observational study of all declared cases of listeriosis in a tertiary hospital from Granada, Spain, from 2008 to 2021. Risk factors, comorbidities, and clinical outcomes were collected for all patients. In addition, clinical symptoms and magnetic resonance imaging (MRI) findings were included for those patients who developed rhombencephalitis. Descriptive and bivariate analyses were performed using SPSS statistical software (IBM SPSS, version 21).

RESULTS

Our cohort comprised 120 patients with listeriosis (41.7% women, mean age: 58.6 ± 23.8 years), of which 10 (8.3%) had rhombencephalitis. The most frequent MRI findings in patients with confirmed rhombencephalitis were T2-FLAIR hyperintensity (100%), T1 hypointensity (80%), scattered parenchymal enhancement (80%), and cranial nerve enhancement (70%), while the most frequent anatomical involvement were pons, medulla oblongata, and cerebellum. Complications occurred in 6 patients (abscess in 4, hemorrhage in 2, hydrocephalus in 1).

CONCLUSIONS

Rhombencephalitis is associated with an increased in-hospital mortality in patients with listeriosis. The anatomical distribution and imaging characteristics of neurolisteriosis could be useful to suggest the diagnosis. Future studies with greater sample size should explore the association between anatomical location, imaging patterns, and associated complications (e.g., hydrocephalus, hemorrhage), and clinical outcomes.

The zebrafish as a novel model for the in vivo study of Toxoplasma gondii replication and interaction with macrophages

Toxoplasma gondii is an obligate intracellular parasite capable of invading any nucleated cell. Three main clonal lineages (type I, II, III) exist and murine models have driven the understanding of general and strain-specific immune mechanisms underlying Toxoplasma infection. However, murine models are limited for studying parasite-leukocyte interactions in vivo, and discrepancies exist between cellular immune responses observed in mouse versus human cells. Here, we developed a zebrafish infection model to study the innate immune response to Toxoplasma in vivo By infecting the zebrafish hindbrain ventricle, and using high-resolution microscopy techniques coupled with computer vision-driven automated image analysis, we reveal that Toxoplasma invades brain cells and replicates inside a parasitophorous vacuole to which type I and III parasites recruit host cell mitochondria. We also show that type II and III strains maintain a higher infectious burden than type I strains. To understand how parasites are cleared in vivo, we further analyzed Toxoplasma-macrophage interactions using time-lapse microscopy and three-dimensional correlative light and electron microscopy (3D CLEM). Time-lapse microscopy revealed that macrophages are recruited to the infection site and play a key role in Toxoplasma control. High-resolution 3D CLEM revealed parasitophorous vacuole breakage in brain cells and macrophages in vivo, suggesting that cell-intrinsic mechanisms may be used to destroy the intracellular niche of tachyzoites. Together, our results demonstrate in vivo control of Toxoplasma by macrophages, and highlight the possibility that zebrafish may be further exploited as a novel model system for discoveries within the field of parasite immunity.This article has an associated First Person interview with the first author of the paper.

Early trigeminal nerve involvement in Listeria monocytogenes rhombencephalitis: case series and systematic review

Listeria monocytogenes is associated with rhombencephalitis. However, the exact mechanisms of brainstem invasion remains poorly understood. Here, we demonstrate clinical and radiological data suggesting that Listeria may invade the brainstem via the trigeminal nerve. Three females (41, 64 and 70 years) with culture proven L. monocytogenes bacteremia and rhombencephalitis were investigated in the period of 2014-16. T2-weighted and contrast-enhanced T1-weighted MRI revealed a cerebellopontine abscess in all three patients, including the involvement of the trigeminal nerve root. In two patients, MRI also revealed selective contrast enhancement of the sensory trigeminal tract in the pons and medulla oblongata. Prior to any other neurological symptoms, two patients complained of hypoesthesia and a tingling sensation in the ipsilateral half of the face, consistent with sensory trigeminal nerve dysfunction on that side. In addition, we identified another 120 cases of Listeria rhombencephalitis following a systematic review. Cranial nerves VII, V, IX, and X, respectively, medulla oblongata, cerebellum and pons, were the most frequently involved brain structures. The present clinical and radiological findings corroborate earlier data from animal experiments, indicating that L. monocytogenes may be capable of retrograde intra-axonal migration along the cranial nerves. We suggest that in a subset of patients with rhombencephalitis L. monocytogenes enters the cerebellopontine angle through the trigeminal nerve, invading the brainstem via the sensory trigeminal nuclei.

A zebrafish larval model reveals early tissue-specific innate immune responses to Mucor circinelloides

Mucormycosis is an emerging fungal infection that is clinically difficult to manage, with increasing incidence and extremely high mortality rates. Individuals with diabetes, suppressed immunity or traumatic injury are at increased risk of developing disease. These individuals often present with defects in phagocytic effector cell function. Research using mammalian models and phagocytic effector cell lines has attempted to decipher the importance of the innate immune system in host defence against mucormycosis. However, these model systems have not been satisfactory for direct analysis of the interaction between innate immune effector cells and infectious sporangiospores in vivo. Here, we report the first real-time in vivo analysis of the early innate immune response to mucormycete infection using a whole-animal zebrafish larval model system. We identified differential host susceptibility, dependent on the site of infection (hindbrain ventricle and swim bladder), as well as differential functions of the two major phagocyte effector cell types in response to viable and non-viable spores. Larval susceptibility to mucormycete spore infection was increased upon immunosuppressant treatment. We showed for the first time that macrophages and neutrophils were readily recruited in vivo to the site of infection in an intact host and that spore phagocytosis can be observed in real-time in vivo. While exploring innate immune effector recruitment dynamics, we discovered the formation of phagocyte clusters in response to fungal spores that potentially play a role in fungal spore dissemination. Spores failed to activate pro-inflammatory gene expression by 6 h post-infection in both infection models. After 24 h, induction of a pro-inflammatory response was observed only in hindbrain ventricle infections. Only a weak pro-inflammatory response was initiated after spore injection into the swim bladder during the same time frame. In the future, the zebrafish larva as a live whole-animal model system will contribute greatly to the study of molecular mechanisms involved in the interaction of the host innate immune system with fungal spores during mucormycosis.

[Listeria monocytogenes rhomboencephalitis. Report of three cases]

An unusual number of cases of rhomb encephalitis have occurred in Chile because of the increased frequency of infections caused by Listeria monocytogenes. We report three females aged 36, 40 and 55 years, with the disease. All presented with a prodrome characterized by headache, nausea, vomiting and fever, followed by ataxia and unilateral palsies of the third, seventh and twelfth cranial nerves. One patient presented also a hemi-hypoesthesia. Magnetic resonance showed lesions in the posterior aspect of the brain stem, specifically in relation to the floor of the fourth ventricle. Blood cultures were positive for Listeria monocytogenes.

[Rhombencephalitis due to Listeria monocytogenes]

A 37-year-old man presented with acute dizziness, nausea, headache and fever. Later on, he developed diplopia, swallowing difficulties, numbness and ataxia. MRI on day 6 showed hypo-intense, contrast-enhancing lesions on TI-weighted scans in the brainstem and cerebellum. Cerebrospinal fluid (CSF) findings on day 6 included pleiocytosis, a mildly-elevated protein level and mildly-decreased glucose level. CSF and blood cultures were initially negative for both bacteria and viruses. Acute disseminated encephalomyelitis (ADEM) was suspected and dexamethasone therapy was started. On day 26, a blood culture was positive for Listeria monocytogenes. The diagnosis 'Listeria rhombencephalitis' was made and the patient was treated with amoxicillin. This resulted in good recovery. In patients with a subacute onset of progressive cranial nerve dysfunction, ataxia, CSF pleiocytosis, and MRI lesions in the brainstem and cerebellum, Listeria rhombencephalitis should be considered. Early diagnosis and treatment improve the prognosis.

Diffusion-weighted magnetic resonance imaging in rhombencephalitis due to Listeria monocytogenes

We present diffusion-weighted imaging findings of a case of rhombencephalitis due to Listeria monocytogenes. It is a rare, life-threatening disorder. The diagnosis is difficult by clinical findings only. In this report, we aim to draw attention to the role of conventional and diffusion-weighted magnetic resonance imaging findings. To our knowledge, this is the first case report in the literature with apparent diffusion coefficient values of diseased brain parenchyma.

[Misleading presentation of rhombencephalitis due to Listeria monocytogenes]

INTRODUCTION

Rhombencephalitis due to Listeria monocytogenes may present in a variety of forms.

CASE REPORT

We describe the case of a 76 years old male presenting with an acute symmetrical palsy of fifth, seventh, ninth-tenth cranial nerves, ophthalmoparesia and miosis, without evident signs of long tract lesion, mimicking a peripheral nervous system or neuromuscular junction disease. The results of the blood cultures and the magnetic resonance imaging gave the diagnosis of rhombencephalitis due to Listeria.

CONCLUSIONS

Rhombencephalitis due to Listeria monocytogenes may present as a symmetric palsy of cranial nerves, therefore it can mimic a cranial nerves multineuritis syndrome.

Treatment difficulties of a listerial rhombencephalitis in an adult patient allergic to penicillins

Rhombencephalitis is not a rare presentation of listerial central nervous system infections in healthy adults. This report describes a case with several management difficulties linked to antibiotic related adverse events, pointing to alternative solutions to aminopenicillins. In addition, the role of dexamethasone in the management of inflammation and neurological symptoms is discussed.

[Listeria rhombencephalitis. Neuroradiological findings]

Rhombencephalitis due to listeria monocytogenes is an uncommon and serious form of brainstem infection. The disease has a characteristic biphasic course: a nonspecific prodrome of headache, nausea or vomiting, and fever lasting for a several days is followed by progressive asymmetrical cranial-nerve palsies. We report two cases of Listeria monocytogenes rhombencephalitis. The first case is a previously healthy 20 year-old-man who developed fever, headache, nausea and vomiting, followed by numbness in left trigeminal nerve. The second case is an immunosuppressed 77 year-old-man, who developed sudden left hemiparesis, followed by fever and severe brainstem dysfunction with ophthalmoplegia and dysphagia. In both cases, a brain magnetic resonance imaging (MRI) scan, showed increased intensity on T2-weighted lesions in the brainstem that enhanced after contrast on T1-weighted sequences. Both patients had a favorable outcome with full clinical recovery. We conclude that MRI aids in the early detection of parenchymal infections, therefore, MRI is crucial for early diagnosis and is very useful for follow-up examinations.

[Wallenberg syndrome as a sign of rhombencephalitis-meningitis due to Listeria monocytogenes]

We report a case of rhombencephalitis with meningitis in a 36-years-old previously healthy man; neurological signs and symptoms were initially consistent with a diagnosis of Wallenberg syndrome. Analysis of cerebrospinal fluid showed predominantly lymphocytic pleocytosis and elevated protein levels. A CT brain scan was normal. MRI of the brain showed a hypertensive type lesion in T2, in the right pontomedullary region that suggested inflammation. A blood culture grew Listeria monocytogenes. The patient improved and fully recovered with appropriate antibiotic treatment. Listeria monocytogenes is a recognized cause of acute brainstem meningoencephalitis. Differential diagnoses that must be considered are other forms of purulent meningitis, viral meningoencephalitis, granulomatosis infections of the central nervous system and, occasionally, stroke.