Demonstration of presence of acanthamoeba mitochondrial DNA in brain tissue and cerebrospinal fluid by PCR in samples from a patient who died of granulomatous amebic encephalitis

Genotyping and Molecular Identification of Acanthamoeba Genotype T4 and Naegleria fowleri from Cerebrospinal Fluid Samples of Patients in Turkey: Is it the Pathogens of Unknown Causes of Death?

PURPOSE

This study was aimed to investigate the presence of pathogenic free-living amoebae (FLA) in suspected cases of meningoencephalitis with unknown causes of death in Turkey.

METHOD

A total of 92 patients, who were diagnosed as meningoencephalitis, were enrolled. All cerebrospinal fluid (CSF) samples were directly microscopically examined and cultured. Acanthamoeba, N. fowleri and B. mandrillaris were further investigated using molecular diagnostic tools including real-time PCR, sequencing, and phylogenetic analyses.

RESULTS

The examined CSF samples were not found positive for the presence of FLA by microscopic examination and culture method. However, two CSF samples were detected positive by real-time PCR assay. Of the positive CSF samples, one was identified as Acanthamoeba genotype T4 and the second positive sample was identified as N. fowleri belonging to genotype II. Furthermore, the pathogens diagnoses was verified through Sanger sequencing.

CONCLUSION

This study was significant to report the presence of Acanthamoeba genotype T4 and N. fowleri genotype II in CSF samples by real-time PCR assay. The present study shows the significance of primary amoebic meningoencephalitis (PAM) and granulomatous amoebic encephalitis (GAE) as one of the differential diagnoses to be considered by clinicians during the evaluation of suspected meningoencephalitis or cases of unknown cause in Turkey. Using real-time PCR, this has made the rapid detection, in a short time-frame, of Acanthamoeba and N. fowleri in CSF samples from patients. The problems with qPCR is that it is not available in every laboratory, reagents are expensive, and it requires skilled and expert personnel to set up these assays.

Opportunistic free-living amoebal pathogens

Pathogenic free-living amoebae affecting the central nervous system are known to cause granulomatous amoebic encephalitis (GAE) or primary amoebic meningoencephalitis (PAM). Although hosts with impaired immunity are generally at a higher risk of severe disease, amoebae such as Naegleria fowleri and Balamuthia mandrillaris can instigate disease in otherwise immunocompetent individuals, whereas Acanthamoeba species mostly infect immunocompromised people. Acanthamoeba also cause a sight-threatening eye infection, mostly in contact lens wearers. Although infections due to pathogenic amoebae are considered rare, recently, these deadly amoebae were detected in water supplies in the USA. This is of particular concern, especially with global warming further exacerbating the problem. Herein, we describe the epidemiology, presentation, diagnosis, and management of free-living amoeba infections.

Detection of Naegleria fowleri, Acanthamoeba spp, and Balamuthia mandrillaris in Formalin-Fixed, Paraffin-Embedded Tissues by Real-Time Multiplex Polymerase Chain Reaction

OBJECTIVES

Pathogenic free-living amebae (FLAs) cause skin, ocular, and central nervous system (CNS) infections with significant morbidity and mortality. Diagnosis of FLA infections by pathologic examination of tissue sections can be aided using molecular assays. This study investigated the performance characteristics of a multiplex real-time polymerase chain reaction (PCR) assay (FLA-PCR) for detection and differentiation of FLAs in clinical specimens.

METHODS

FLA-PCR was performed on 39 human specimens comprising one cutaneous, 14 corneal, and 24 CNS formalin-fixed, paraffin-embedded (FFPE) tissues with a histopathologic diagnosis of FLA infection and four CNS FFPE tissues with inflammation but no evidence of FLAs. In addition, clinical specificity and assay limit of detection were determined.

RESULTS

FLA detection sensitivities ranged from 79% to 84% in FFPE tissues. No cross-reactivity was observed.

CONCLUSIONS

While sensitivity is limited, FLA-PCR assay may serve as a useful adjunct for detection or confirmation of FLA infections in FFPE tissues.

A case report of granulomatous amoebic encephalitis by Group 1 Acanthamoeba genotype T18 diagnosed by the combination of morphological examination and genetic analysis

Background

The diagnosis of granulomatous amoebic encephalitis is challenging for clinicians because it is a rare and lethal disease. Previous reports have indicated that Acanthamoeba with some specific genotypes tend to cause the majority of human infections. We report a case of granulomatous amoebic encephalitis caused by Acanthamoeba spp. with genotype T18 in an immunodeficient patient in Japan after allogenic bone marrow transplantation, along with the morphological characteristics and genetic analysis.

Case presentation

A 52-year old man, who had undergone allogenic bone marrow transplantation, suffered from rapid-growing brain masses in addition to pneumonia and died within 1 month from the onset of the symptoms including fever, headache and disorientation. Infection with Acanthamoeba in the brain and lung was confirmed by histological evaluation; immunohistochemical staining and polymerase chain reaction analysis using autopsy samples also indicated the growth of Acanthamoeba in the brain. Gene sequence analysis indicated that this is the second documented case of infection with Acanthamoeba spp. with genotype T18 in a human host. Postmortem retrospective evaluation of cerebrospinal fluid sample in our case, as well as literature review, indicated that some cases of granulomatous amoebic encephalitis caused by Acanthamoeba may be diagnosable by cerebrospinal fluid examination.

Conclusion

This case indicates that Acanthamoeba spp. with genotype T18 can also be an important opportunistic pathogen. For pathologists as well as physicians, increased awareness of granulomatous amoebic encephalitis is important for improving the poor prognosis along with the attempt to early diagnosis with cerebrospinal fluid.

Management of granulomatous amebic encephalitis: Laboratory diagnosis and treatment

Granulomatous amebic encephalitis is a life-threatening central nervous system (CNS) infection caused by the free-living amoebae Acanthamoeba spp., Balamuthia mandrillaris and Sappinia pedata. The disease has a subacute to chronic onset affecting commonly the immunocompromised population with high mortality rate. The diagnosis of this disease entity requires high suspicion with appropriate sample collection and testing by the laboratory experts. Radiological investigations are nonspecific and commonly confused with CNS tuberculosis, neurocysticercosis, disseminated encephalomyelitis, viral encephalitis etc., delaying the accurate diagnosis of these cases. Early diagnosis plays a crucial role in the survival of these cases since appropriate management can be initiated. No single drug is effective; hence multiple antibiotics targeting various proteins or receptors are required for successful treatment. A combination of surgical and medical interventions involving multiple specialty experts is required to prevent death and morbidity in survivors.

Diagnosis of infections caused by pathogenic free-living amoebae

Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris, and Sappinia sp. are pathogenic free-living amoebae. N. fowleri causes Primary Amoebic Meningoencephalitis, a rapidly fatal disease of the central nervous system, while Acanthamoeba spp. and B. mandrillaris cause chronic granulomatous encephalitis. Acanthamoeba spp. also can cause cutaneous lesions and Amoebic Keratitis, a sight-threatening infection of the cornea that is associated with contact lens use or corneal trauma. Sappinia pedata has been identified as the cause of a nonlethal case of amoebic encephalitis. In view of the potential health consequences due to infection with these amoebae, rapid diagnosis is critical for early treatment. Microscopic examination and culture of biopsy specimens, cerebral spinal fluid (CSF), and corneal scrapings have been used in the clinical laboratory. For amoebic keratitis, confocal microscopy has been used to successfully identify amoebae in corneal tissue. More recently, conventional and real-time PCR assays have been developed that are sensitive and specific for the amoebae. In addition, multiplex PCR assays are available for the rapid identification of these pathogens in biopsy tissue, CSF, and corneal specimens.

Demonstration of Balamuthia and Acanthamoeba mitochondrial DNA in sectioned archival brain and other tissues by the polymerase chain reaction

Granulomatous amoebic encephalitis (GAE) is a usually fatal disease caused by the free-living amoebae Balamuthia mandrillaris and Acanthamoeba spp. The intent of this study was to determine if the polymerase chain reaction (PCR) could be used retrospectively to detect amoeba mitochondrial 16S rRNA gene DNA in confirmed archival tissue sections from GAE cases stored in our laboratories for 1 to 34 years. The DNA was extracted from deparaffinized sections, and appropriate primer sets for each of the two amoebae were used for amoeba DNA detection. Indirect immunofluorescent (IIF) staining of tissue sections was used as the standard for identification of amoebae against which the PCR results were compared. Sixty slides from a total of 56 cases were processed by PCR for amoeba 16S DNA. In 28 slides (47%), there was agreement between the IIF and PCR results. In 41 of the slides (52%), no amoeba DNA was detected after PCR. In one slide (1%), the PCR and IIF results did not agree. While PCR supported IIF findings in about half of the slides, there are significant limitations in amoeba DNA identifications in formalin-fixed brain tissues. Degradation of amoeba DNA caused by formalin fixation was probably a factor in limiting valid results.

Demonstration of Balamuthia and Acanthamoeba mitochondrial DNA in sectioned archival brain and other tissues by the polymerase chain reaction

Granulomatous amoebic encephalitis (GAE) is a usually fatal disease caused by the free-living amoebae Balamuthia mandrillaris and Acanthamoeba spp. The intent of this study was to determine if the polymerase chain reaction (PCR) could be used retrospectively to detect amoeba mitochondrial 16S ribosomal ribonucleic acid gene deoxyribonucleic acid (DNA) in confirmed archival tissue sections from GAE cases stored in our laboratories for 1 to 34 years. The DNA was extracted from deparaffinized sections, and appropriate primer sets for each of the two amoebae were used for DNA detection. Indirect immunofluorescent staining (IIF) of tissue sections was used as the standard for identification of amoebae against which the PCR results were compared. Sixty slides from a total of 56 cases were processed by PCR for amoeba 16S DNA. In 28 (47%) slides, there was agreement between the IIF and PCR results. In 41 of the slides (52%), no DNA was detected after PCR. In one slide (1%), the PCR and IIF results did not agree. While PCR supported IIF findings in about half of the slides, there are significant limitations in amoeba DNA identifications in formalin-fixed brain tissues. Degradation of amoeba DNA because of formalin fixation was probably a factor in limiting valid results.