Identification and molecular typing of Naegleria fowleri from a patient with primary amebic meningoencephalitis in China

Naegleria fowleri is the only Naegleria spp. known to cause an acute, fulminant, and rapidly fatal central nervous system infection in humans called primary amebic meningoencephalitis (PAM). In 2016, a patient with suspected PAM was found in Zhejiang Province of China. The pathogen was identified by microscopic examination and PCR. The positive PCR products were sequenced and the sequences were aligned using the NCBI BLAST program. The homologous and phylogenetic analysis was conducted using MEGA 6 program. On microscopy of direct smears, motile cells with pseudopodia were observed, and the motion characteristics of the pseudopodia as well as the cell morphology suggested that the pathogens were amoeba trophozoites. Wright-Giemsa-stained smears showed amoeba trophozoites of various shapes, which measured 10-25μm in size; these were characterized by a prominent, centrally placed nucleolus and a vacuolated cytoplasm. PCR was negative for Entamoeba histolytica and Entamoeba dispar, but positive for Naegleria spp. and N. fowleri. The nucleotide sequences acquired in this study have been submitted to GenBank with accession numbers KX909928 and KX909927, respectively. The BLAST analysis revealed that the sequences of KX909928 and KX909927 had 100% similarity with the sequence of the N. fowleri gene (KT375442.1). Sequence alignment and the phylogenetic tree revealed that the N. fowleri collected in this study was classified as genotype 2 and was most closely related to Naegleria lovaniensis. This study confirmed N. fowleri as the agent responsible for the infection in this patient. PAM normally progresses rapidly and is generally universally fatal within a week. Unfortunately this patient died at 2 weeks after the onset of symptoms.

Comparative analysis of cytokine gene expression in cerebrospinal fluid of horses without neurologic signs or with selected neurologic disorders

OBJECTIVE

To determine gene transcription for cytokines in nucleated cells in CSF of horses without neurologic signs or with cervical stenotic myelopathy (CSM), West Nile virus (WNV) encephalitis, equine protozoal myeloencephalitis (EPM), or spinal cord trauma.

ANIMALS

41 horses (no neurologic signs [n = 12], CSM [8], WNV encephalitis [9], EPM [6], and spinal cord trauma [6]).

PROCEDURES

Total RNA was extracted from nucleated cells and converted into cDNA. Gene expression was measured by use of real-time PCR assay and final quantitation via the comparative threshold cycle method.

RESULTS

Cytokine genes expressed by nucleated cells of horses without neurologic signs comprised a balance between proinflammatory tumor necrosis factor-alpha (TNF-alpha), anti-inflammatory cytokines (interleukin [IL]-10 and transforming growth factor [TGF]-beta), and Th1 mediators (interferon [IFN]-gamma). Cells of horses with CSM mainly expressed genes for TNF-alpha, TGF-beta, and IL-10. Cells of horses with WNV encephalitis mainly expressed genes for IL-6 and TGF-beta. Cells of horses with EPM mainly had expression of genes for IL-6, IL-8, IL-10, TNF-alpha, IFN-gamma, and TGF-beta. Cells from horses with spinal cord trauma had expression mainly for IL-6; IFN-gamma; TGF-beta; and less frequently, IL-2, IL-10, and TNF-alpha. Interleukin-8 gene expression was only detected in CSF of horses with infectious diseases.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite the small number of CSF samples for each group, results suggest distinct gene signatures expressed by nucleated cells in the CSF of horses without neurologic signs versus horses with inflammatory or traumatic neurologic disorders.

Indirect fluorescent antibody testing of cerebrospinal fluid for diagnosis of equine protozoal myeloencephalitis

OBJECTIVE

To assess the use of CSF testing with an indirect fluorescent antibody test (IFAT) for diagnosis of equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona.

SAMPLE POPULATION

Test results of 428 serum and 355 CSF samples from 182 naturally exposed, experimentally infected, or vaccinated horses.

PROCEDURE

EPM was diagnosed on the basis of histologic examination of the CNS. Probability distributions were fitted to serum IFAT results in the EPM+ and EPM-horses, and correlation between serum and CSF results was modeled. Pairs of serum-CSF titers were generated by simulation, and titer-specific likelihood ratios and post-test probabilities of EPM at various pretest probability values were estimated. Post-test probabilities were compared for use of a serum-CSF test combination, a serum test only, and a CSF test only.

RESULTS

Post-test probabilities of EPM increased as IFAT serum and CSF titers increased. Post-test probability differences for use of a serum-CSF combination and a serum test only were < or = 19% in 95% of simulations. The largest increases occurred when serum titers were from 40 to 160 and pre-test probabilities were from 5% to 60%. In all simulations, the difference between pre- and post-test probabilities was greater for a CSF test only, compared with a serum test only.

CONCLUSIONS AND CLINICAL RELEVANCE

CSF testing after a serum test has limited usefulness in the diagnosis of EPM. A CSF test alone might be used when CSF is required for other procedures. Ruling out other causes of neurologic disease reduces the necessity of additional EPM testing.

Cerebral trypanosomiasis and AIDS

A 36 year-old black female, complaining of headache of one month's duration presented with nausea, vomiting, somnolence, short memory problems, loss of weight, and no fever history. Smoker, intravenous drugs abuser, promiscuous lifestyle.

PHYSICAL EXAMINATION

left homonimous hemianopsia, left hemiparesis, no papilledema, diffuse hyperreflexia, slowness of movements. Brain CT scan: tumor-like lesion in the splenium of the corpus calosum, measuring 3.5 x 1.4 cm, with heterogeneous enhancing pattern, suggesting a primary CNS tumor. Due to the possibility of CNS infection, a lumbar puncture disclosed an opening pressure of 380 mmH(2)0; 11 white cells (lymphocytes); glucose 18 mg/dl (serum glucose 73 mg/dl); proteins 139 mg/dl; presence of Trypanosoma parasites. Serum Elisa-HIV tests turned out to be positive. Treatment with benznidazole dramatically improved clinical and radiographic picture, but the patient died 6 weeks later because of respiratory failure. T. cruzi infection of the CNS is a rare disease, but we have an increasing number of cases in HIV immunocompromised patients. Diagnosis by direct observation of CSF is uncommon, and most of the cases are diagnosed by pathological examination. It is a highly lethal disease, even when properly diagnosed and treated. This article intends to include cerebral trypanosomiasis in the differential diagnosis of intracranial space-occupying lesions, especially in immunocompromised patients from endemic regions.

Lymphocyte phenotype subsets in the cerebrospinal fluid of normal horses and horses with equine protozoal myeloencephalitis

The percentages of T-lymphocytes, lymphocyte subsets CD4+ and CD8+ T-cells, and lymphocyte adhesion molecule CD11a/CD18 were determined in the peripheral blood and cerebrospinal fluid (CSF) of seven normal horses and four horses with equine protozoal myeloencephalitis (EPM) using flow cytometry. There was a greater percentage of CD5+ cells in the CSF (79.0%) than in peripheral blood (67.0%), although this did not achieve statistical significance. Furthermore, the lymphocyte population in CSF comprises a significantly greater (P = .01) percentage of CD8+ T-cells, resulting in a decrease of the CD4/CD8 ratio. Lymphocyte phenotype subsets in peripheral blood or CSF from horses affected with EPM did not differ from normal horses, although CD5+ T-lymphocytes were seen in significantly greater numbers in the CSF of EPM-affected horses (93.2%) than in normal horses (79.0%).