Identification and Biotyping of Pythium insidiosum Isolated from Urban and Rural Areas of Thailand by Multiplex PCR, DNA Barcode, and Proteomic Analyses

Pythium insidiosum causes pythiosis, a fatal infectious disease of humans and animals worldwide. Prompt diagnosis and treatment are essential to improve the clinical outcome of pythiosis. Diagnosis of P. insidiosum relies on immunological, molecular, and proteomic assays. The main treatment of pythiosis aims to surgically remove all affected tissue to prevent recurrent infection. Due to the marked increase in case reports, pythiosis has become a public health concern. Thailand is an endemic area of human pythiosis. To obtain a complete picture of how the pathogen circulates in the environment, we surveyed the presence of P. insidiosum in urban (Bangkok) and rural areas of Thailand. We employed the hair-baiting technique to screen for P. insidiosum in 500 water samples. Twenty-seven culture-positive samples were identified as P. insidiosum by multiplex PCR, multi-DNA barcode (rDNA, cox1, cox2), and mass spectrometric analyses. These environmental strains of P. insidiosum fell into Clade-II and -III genotypes and exhibited a close phylogenetic/proteomic relationship with Thai clinical strains. Biodiversity of the environmental strains also existed in a local habitat. In conclusion, P. insidiosum is widespread in Thailand. A better understanding of the ecological niche of P. insidiosum could lead to the effective prevention and control of this pathogen.

Assessment of matrix-assisted laser desorption ionization-time of flight mass spectrometry for identification and biotyping of the pathogenic oomycete Pythium insidiosum

OBJECTIVE

Pythiosis is a life-threatening infectious disease caused by the oomycete Pythium insidiosum. The disease has been increasingly reported worldwide. Most patients with pythiosis undergo surgical removal of an infected organ. Early diagnosis contributes to better prognosis of pythiosis patients. Here, we assessed the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for identification and biotyping of P. insidiosum.

METHODS

A comprehensive set of mass spectra of P. insidiosum was generated to evaluate MALDI-TOF MS for identification and biotyping of P. insidiosum.

RESULTS

MALDI-TOF MS accurately identified all 13 P. insidiosum strains tested, at the species level. Mass spectra of P. insidiosum did not match any other microorganisms, including fungi (i.e., Aspergillus species, Fusarium species, and fungal species of the class Zygomycetes), which have similar microscopic morphologies with this oomycete. MALDI-TOF MS- and rDNA sequence-based biotyping methods consistently classified P. insidiosum into three groups: Clade-I (American strains), II (Asian and Australian strains), and III (mostly Thai strains).

CONCLUSIONS

MALDI-TOF MS has been successfully used for identification and biotyping of P. insidiosum. The obtained mass spectral database allows clinical microbiology laboratories, well-equipped with a MALDI-TOF mass spectrometer, to conveniently identify P. insidiosum, without requiring any pathogen-specific reagents (i.e., antigen, antibody or primers).

Urinary Metabolomic Profiling in Chronic Hepatitis B Viral Infection Using Gas Chromatography/Mass Spectrometry

Background: Chronic hepatitis B (CHB) can lead to cirrhosis and hepatocellular carcinoma. The metabolomic profiling has been shown to be associated with pathogenic mechanisms in many medical conditions including CHB. The purpose of this study was to investigate the urine metabolomic profiles in CHB patients by gas chromatography/mass spectrometry (GC/MS). Methods: Urine samples were collected from CHB patients (n = 20) and normal control subjects (n = 20). Metabolite profiles were assessed using GC/MS in conjunction with multivariate statistical analysis, in order to identify biomarker metabolites. Pathway analysis was performed by MetaboAnalyst 3.0 and KEGG database.Results: Twelve out of 377 metabolites were shown to be significantly different between the CHB and normal control groups (p < 0.05). These include palmitic acid, stearic acid, oleic acid, benzoic acid, butanoic acid, cholesterol, glycine, 3-heptanone, 4-heptanone, hexanal, 1-tetradecanol and naphthalene. Multivariate statistical analysis constructed using these expressed metabolites showed CHB patients can be discriminated from healthy controls with high sensitivity (95%) and specificity (85%). All the metabolic perturbations in this disease are associated with pathways of fatty acid, amino acid, bile acid and gut microbial metabolism. Conclusion: CHB patients have a specific urinary metabolomic profile. The abnormalities of fatty acid, amino acid, bile acid, and gut microbial metabolism lead to the development of disease progression. GC/MS-based assay is a promising tool for the metabolomic study in CHB.

Screening of Fabry disease in patients with end-stage renal disease of unknown etiology: the first Thailand study

We aimed to explore the prevalence of Fabry disease in Thai patients who were diagnosed with end-stage renal disease (ESRD) of an unknown origin. Venous blood samples were collected from ESRD patients for biochemical and molecular studies. Alpha-galactosidase A (α-GAL A) screening was performed from dried-blood spots using fluorometry. Molecular confirmation was performed using DNA sequencing of the GLA gene. A total of 142 male and female patients were included in this study. Ten patients (7.04%) exhibited a significant decrease in α-GAL A activity. There were no definitive pathogenic mutations observed in the molecular study. However, four patients revealed a novel nucleotide variant at c.1 -10 C>T, which was identified as a benign variant following screening in the normal population. In conclusion, the α-GAL A assay utilizing dried-blood spots revealed a significant false positive rate. There was no definitive Fabry disease confirmed in Thai patients diagnosed with ESRD of unknown etiology.

Low oxygen saturation and severe anemia in compound heterozygous Hb Louisville [β42(CD1)Phe→Leu] and Hb La Desirade [β129(H7)Ala→Val]

OBJECTIVE

To investigate the cause(s) of a Thai male proband presenting low oxygen saturation by pulse oximetry (SpO₂) and severe anemia.

METHODS

As Hb variant was suspected, Hb typing was determined by high-performance liquid chromatography and capillary electrophoresis, and subsequently Hb variant was identified by DNA sequencing. Complete blood counts were performed using automated blood cell counter and oxygen saturation was measured by pulse oximetry.

RESULTS

Proband was compound heterozygous for Hb Louisville [β42(CD1)Phe→Leu] and Hb La Desirade [β129(H7)Ala→Val]. Of the proband's two sons, one was compound heterozygous for Hb Louisville and Hb E and the other for Hb La Desirade and Hb E. The former son had similar clinical features and laboratory findings with those of the proband while the latter showed had no abnormal clinical manifestations.

CONCLUSION

This the first report of compound heterozygosity of Hb Louisville and Hb La Desirade in an individual of Southeast Asian ethnicity. Hb variant identification is crucial for genetic counseling and appropriate treatment in regions where hemoglobinopathies are common.

FIRST IDENTIFICATION OF HEMOGLOBIN LANSINGRAMATHIBODI [α87(F8)His → Gln; CAC>CAG (HBA1: c.264C>G)] IN A THAI FAMILY WITH SPURIOUS HYPOXEMIA

We report, for the first time, hemoglobin (Hb) Lansing-Ramathibodi [α87(F8)His → Gln; CAC>CAG (HBA1: c.264C>G)] in four members of a Thai family presented with low measured oxygen saturation by pulse oximetry (SpO2), with discrepancy between low SpO2 and normal calculated oxygen saturation by arterial blood gas analysis, and no cyanosis or methemoglobinemia. The causative mutation is located in HBA1 whereas in previous reports of Hb Lansing the mutation is on HBA2, including that in a Japanese individual. The index and a male sibling also co-inherited Hb Pakse, a non-deletional α-thalassemia 2, resulting in mild reticulocytosis. Correct Hb identification is crucial for genetic counselling and, thereby, avoiding unnecessary investigation and treatment for spurious hypoxemia.