Identification of a Novel T17 Genotype of Acanthamoeba from Environmental Isolates and T10 Genotype Causing Keratitis in Thailand ▿

We analyzed the nuclear small-subunit rRNA genes of Acanthamoeba isolates from freshwater sources (n = 16) and from patients (n = 6) in Bangkok and surrounding areas. The T10 genotype from a keratitis patient and a novel T17 genotype from water samples were diagnosed for the first time in this study

Stability and infectivity of enteroviruses on dry surfaces: Potential for indirect transmission control

Hand, foot, and mouth disease (HFMD) is a contagious disease mainly occurring in young children, and outbreaks commonly occur among young children in the Asia–Pacific region including Thailand. Moreover, the World Health Organization (WHO) monitors HFMD in the Western Pacific region to detect outbreaks and other significant events by the Regional Event Based Surveillance System. HFMD is mainly caused by a group of enteroviruses (EVs) transmitted through direct contact (person to person) and indirect contact with contaminated objects (surface-to-hand). However, few studies have examined the surface stability of EVs. In this study, we investigated the stability of enterovirus A71 (EV-A71) and coxsackievirus A16 (CVA16) on three different dry surfaces (wood, plastic, and stainless steel) using the endpoint titration using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) staining of viable cells and real-time polymerase chain reaction (viral genome detection). The results revealed that virus infectivity dramatically decreased within a few hours on dry surfaces. However, viral RNA could be detected on dry surfaces for up to 28 days. Concerning heat inactivation, both EV-A71 and CVA16 were inactivated after exposure to 60°C for 15 min. Information on virus stability on different dry surfaces will provide useful information for HFMD transmission control

Molecular epidemiological study of hand, foot, and mouth disease in a kindergarten-based setting in Bangkok, Thailand

Hand, foot, and mouth disease (HFMD) is a contagious childhood illness and annually affects millions of children aged less than 5 years across the Asia-Pacific region. HFMD transmission mainly occurs through direct contact (person-to-person) and indirect contact with contaminated surfaces and objects. Therefore, public health measures to reduce the spread of HFMD in kindergartens and daycare centers are essential. Based on the guidelines by the Department of Disease Control, a school closure policy for HFMD outbreaks wherein every school in Thailand must close when several HFMD classrooms (more than two cases in each classroom) are encountered within a week, was implemented, although without strong supporting evidence. We therefore conducted a prospective cohort study of children attending five kindergartens during 2019 and 2020. We used molecular genetic techniques to investigate the characteristics of the spreading patterns of HFMD in a school-based setting in Bangkok, Thailand. These analyses identified 22 index cases of HFMD (symptomatic infections) and 25 cases of enterovirus-positive asymptomatic contacts (24 students and one teacher). Enterovirus (EV) A71 was the most common enterovirus detected, and most of the infected persons (8/12) developed symptoms. Other enteroviruses included coxsackieviruses (CVs) A4, CV-A6, CV-A9, and CV-A10 as well as echovirus. The pattern of the spread of HFMD showed that 45% of the subsequent enteroviruses detected in each outbreak possessed the same serotype as the first index case. Moreover, we found a phylogenetic relationship among enteroviruses detected among contact and index cases in the same kindergarten. These findings confirm the benefit of molecular genetic assays to acquire accurate data to support school closure policies designed to control HFMD infections

Arbovirus Seroprevalence Study in Bangphae District, Ratchaburi Province, Thailand: Comparison between ELISA and a Multiplex Rapid Diagnostic Test (Chembio DPP^® ZCD IgG)

Arboviruses, particularly dengue virus (DENV), Zika virus (ZIKV), and Chikungunya virus (CHIKV), pose a growing threat to global public health. For disease burden estimation and disease control, seroprevalence studies are paramount. This study was performed to determine the prevalence of DENV, ZIKV, and CHIKV on healthy individuals aged from 1–55 years old in Bangphae district, Ratchaburi province, Thailand. Enzyme-linked immunosorbent assays (ELISAs) and rapid diagnostic tests (RDTs) were performed on archived samples from a dengue serological survey conducted from 2012–2015. All 2012 samples had been previously tested using an anti-DENV immunoglobulin (Ig)G ELISA, and 400 randomly selected samples stratified by age, sex, and residential area were assessed by an in-house anti-ZIKV IgG ELISA and a commercial anti-CHIKV IgG ELISA to determine virus-specific antibody levels. An RDT (Chembio DPP® ZCD IgM/IgG System) was also used to investigate the presence of antibodies against DENV, ZIKV, or CHIKV. The ELISA results indicate that the seroprevalences of DENV, ZIKV, and CHIKV were 84.3%, 58.0%, and 22.5%, respectively. The youngest age group had the lowest seroprevalence for all three arboviruses, and the seroprevalences for these viruses were progressively higher with increasing participant age. The DPP® IgG sensitivities, as compared with ELISAs, for DENV, ZIKV, and CHIKV were relatively low, only 43.92%, 25.86%, and 37.78%, respectively. The ELISA results indicate that 16% of the study population was seropositive for all three viruses. DENV had the highest seroprevalence. ZIKV and CHIKV were also circulating in Bangphae district, Ratchaburi province, Thailand. The DPP® ZCD rapid test is not sensitive enough for use in seroprevalence studies

The use of high-resolution (1)H nuclear magnetic resonance (NMR) spectroscopy in the clinical diagnosis of Acanthamoeba

Acanthamoeba are opportunistic protozoan pathogens that can produce sight-threatening keratitis and fatal granulomatous encephalitis. The successful prognosis requires early diagnosis and differentiation of pathogenic Acanthamoeba spp. followed by aggressive treatment regimen. In this study, we tested the use of high-resolution (1)H NMR spectroscopy in the clinical diagnosis of Acanthamoeba. Using NMR spectroscopy combined with Pattern Recognition Analysis (PRA), we analysed variations in the biochemical 'fingerprint' of invasive and non-invasive Acanthamoeba, its closely related genus, Balamuthia mandrillaris, neuropathogenic Escherichia coli K1 strain E44, a laboratory strain of E. coli K-12, HB101, mammalian cells including human brain microvascular endothelial cells and monkey kidney cells. The findings revealed significant variations in the metabolites of amoebae, mammalian cells and bacteria. Interestingly, (1)H NMR spectra provided distinct biochemical profiles of clinical and non-clinical Acanthamoeba isolates highlighting the potential of (1)H NMR spectroscopy combined with PRA for the development of a novel diagnostic test that could rapidly identify pathogenic Acanthamoeba isolates with high sensitivity and specificity