Evaluation of rapid influenza diagnostic tests for influenza A and B in the tropics.

Rapid diagnosis of influenza is important for early treatment and institution of control measures. In developing tropical countries such as Malaysia, influenza occurs all year round, but molecular assays and conventional techniques (such as immunofluorescence and culture) for diagnosis are not widely available. Rapid influenza diagnostic tests (RIDTs) may be useful in this setting. A total of 552 fresh respiratory specimens were assessed from patients with respiratory symptoms at a teaching hospital in Kuala Lumpur, Malaysia from November 2017 to March 2018. Two digital immunoassays (DIAs), STANDARD F Influenza A/B Fluorescence Immunoassay (STANDARD F) and Sofia Influenza A + B Fluorescence Immunoassay (Sofia) and one conventional RIDT (immunochromatographic assay), SD Bioline Influenza Ag A/B/A(H1N1) Pandemic rapid test kit (SD Bioline) were evaluated in comparison with a WHO-recommended reverse transcription quantitative PCR (RT-qPCR). Of the 552 samples, influenza A virus was detected in 47 (8.5%) and influenza B virus in 7 (1.3%). The digital immunoassays STANDARD F and Sofia had significantly higher overall sensitivity rates (71.7% and 70.6%, respectively) than the conventional RIDT SD Bioline and immunofluorescence/viral culture (55.8% and 52.8%, respectively). Sensitivity rates were higher for influenza A than influenza B, and specificity rates were uniformly high, ranging from 98% to 100%. Digital readout RIDTs can be used in tropical settings with year-round influenza if PCR is unavailable.

Detection of Respiratory Viruses from ARTI Patients by xTAG RVP Fast v2 Assay and Conventional Methods.

INTRODUCTION: Acute respiratory tract infections (ARTIs) are a major cause of morbidity and mortality in paediatric patients. Therefore, early detection of the viral aetiologies of ARTIs is essential for patient management and infection control. In this study, we evaluated the performance of a new multiplex polymerase chain reaction (PCR) assay (xTAG Respiratory Viral Panel [RVP] Fast v2) in the detection of respiratory viruses by comparing it with that of viral culture and direct immunofluorescence (IF) staining. METHODS: Nasopharyngeal swab and aspirate samples were collected prospectively from 199 patients who presented with ARTIs at the University Malaya Medical Centre (UMMC) in Kuala Lumpur, Malaysia during a 10-month period. The PCR assay was conducted in parallel with conventional culture and direct IF staining methods. RESULTS: The positive rate of the xTAG RVP Fast v2 assay (78.4%) in detecting respiratory viruses was higher than that of the viral isolation (7.5%) and direct IF (23.1%) methods. Using the xTAG RVP Fast v2 assay, human enterovirus/human rhinovirus (HEV/HRV) was the most frequently detected (46.2%). The xTAG RVP Fast v2 assay revealed mixed infection caused by two or three respiratory viruses in 40 specimens, and these were undetected by the viral isolation and direct IF methods. CONCLUSION: The xTAG RVP Fast v2 assay was superior to conventional methods in the identification of common respiratory viruses, with higher sensitivity and shorter turnaround times for laboratory results.

Evolution of Influenza B Virus in Kuala Lumpur, Malaysia, between 1995 and 2008.

Influenza B virus causes significant disease but remains understudied in tropical regions. We sequenced 72 influenza B viruses collected in Kuala Lumpur, Malaysia, from 1995 to 2008. The predominant circulating lineage (Victoria or Yamagata) changed every 1 to 3 years, and these shifts were associated with increased incidence of influenza B. We also found poor lineage matches with recommended influenza virus vaccine strains. While most influenza B virus lineages in Malaysia were short-lived, one circulated for 3 to 4 years.

Early detection of dengue virus by use of reverse transcription-recombinase polymerase amplification.

A method for the rapid diagnosis of early dengue virus (DENV) infection is highly needed. Here, a prototype reverse transcription-recombinase polymerase amplification (RT-RPA) assay was developed. The assay detected DENV RNA in <20 min without the need for thermocycling amplification. The assay enabled the detection of as few as 10 copies of DENV RNA. The designed RT-RPA primers and exo probe detected the DENV genome of at least 12 genotypes of DENV circulating globally without cross-reacting with other arboviruses. We assessed the diagnostic performance of the RT-RPA assay for the detection of DENV RNA in 203 serum samples of patients with clinically suspected dengue. The sera were simultaneously tested for DENV using a reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay, quantitative RT-PCR (qRT-PCR), and IgM- and IgG-capture enzyme-linked immunosorbent assays (ELISA). Acute DENV infection was confirmed in 130 samples and 61 of the samples (46.9%) were classified as viremic with qRT-PCR. The RT-RPA assay showed good concordance (κ of ≥0.723) with the RT-LAMP and qRT-PCR assays in detecting the dengue viremic samples. When used in combination with ELISA, both the RT-RPA and RT-LAMP assays increased the detection of acute DENV infection to ≥95.7% (≥45/47) in samples obtained within 5 days of illness. The results from the study suggest that the RT-RPA assay is the most rapid molecular diagnostic tool available for the detection of DENV. Hence, it is possible to use the RT-RPA assay in a laboratory to complement routine serology testing for dengue.

Outbreak of human infection with Sarcocystis nesbitti, Malaysia, 2012.

An outbreak of fever associated with myalgia and myositis occurred in 2012 among 89 of 92 college students and teachers who visited Pangkor Island, Malaysia. The Sarcocystis nesbitti 18S rRNA gene and sarcocysts were obtained from muscle tissues of 2 students. Our findings indicate emergence of S. nesbitti infections in humans in Malaysia.

Seroprevalence of seasonal and pandemic influenza a in Kuala Lumpur, Malaysia in 2008-2010.

Relatively little is known about the burden of influenza in tropical countries. The seroprevalence of pandemic influenza A (H1N1) 2009, seasonal H1N1 and H3N2 was determined in Kuala Lumpur, Malaysia. Pre- and post-pandemic residual laboratory sera were tested by hemagglutination-inhibition. The seroprevalence of A(H1N1)pdm09 increased from 3.7% pre-pandemic to 21.9% post-pandemic, giving an overall cumulative incidence of 18.1% (95% CI, 13.8-22.5%), mainly due to increases in those <5, 5-17, and 18-29 years old. In contrast with findings from USA, Europe, and Australia, pre-existing seroprevalence to A(H1N1)pdm09 was low at 5.6% in the elderly age group of >55 years. A(H1N1)pdm09 affected almost a third of those <30 years in Kuala Lumpur. Pre-pandemic seroprevalence was 14.7% for seasonal H1N1 and 21.0% for H3N2, and these rates did not change significantly after the pandemic. Seasonal and pandemic influenza cause a considerable burden in tropical Malaysia, particularly in children and young adults.

Detection of dengue viruses using reverse transcription-loop-mediated isothermal amplification.

BACKGROUND: Early and rapid detection of dengue virus (DENV) infection during the febrile period is crucial for proper patient management and prevention of disease spread. An easy to perform and highly sensitive method is needed for routine implementation especially in the resource-limited rural healthcare settings where dengue is endemic. METHODS: A single-tube reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay with a set of nine primers was developed for the detection of all four DENV serotypes and their different genotypes. The sensitivity and specificity of the RT-LAMP were evaluated. The clinical applicability of RT-LAMP assay for detection of DENV RNA was assessed in a total of 305 sera of clinically-suspected dengue patients. The test results of RT-LAMP were statistically compared to those of quantitative reverse transcription-polymerase chain reaction (qRT-PCR), IgM- and IgG-capture enzyme-linked immunosorbent assays (ELISA). RESULTS: Acute DENV infection was confirmed in 171 samples (n = 305); 43.3% (74/171) and 46.8% (80/171) of the samples were positive for DENV using RT-LAMP and qRT-PCR, respectively. The combination of RT-LAMP with the dengue IgM and IgG ELISA increased detection of acute DENV infection to 97.7% (167/171), in comparison to only 70.8% (121/171) when dengue IgM and IgG ELISA alone were used. The RT-LAMP assays showed high concordance (κ = 0.939) with the qRT-PCR. The RT-LAMP assay detected up to 10 copies of virus RNA within an hour but 100% reproducibility (12/12) was achieved with 100 copies. There was no cross reactivity of RT-LAMP with other closely related arboviruses. CONCLUSION: The RT-LAMP assay developed in this study is sensitive, specific and simple to perform. The assay improved the detection of dengue when used in combination with serological methods.

Epidemiology and seasonality of respiratory viral infections in hospitalized children in Kuala Lumpur, Malaysia: a retrospective study of 27 years.

BACKGROUND: Viral respiratory tract infections (RTI) are relatively understudied in Southeast Asian tropical countries. In temperate countries, seasonal activity of respiratory viruses has been reported, particularly in association with temperature, while inconsistent correlation of respiratory viral activity with humidity and rain is found in tropical countries. A retrospective study was performed from 1982-2008 to investigate the viral etiology of children (≤ 5 years old) admitted with RTI in a tertiary hospital in Kuala Lumpur, Malaysia. METHODS: A total of 10269 respiratory samples from all children ≤ 5 years old received at the hospital's diagnostic virology laboratory between 1982-2008 were included in the study. Immunofluorescence staining (for respiratory syncytial virus (RSV), influenza A and B, parainfluenza types 1-3, and adenovirus) and virus isolation were performed. The yearly hospitalization rates and annual patterns of laboratory-confirmed viral RTIs were determined. Univariate ANOVA was used to analyse the demographic parameters of cases. Multiple regression and Spearman's rank correlation were used to analyse the correlation between RSV cases and meteorological parameters. RESULTS: A total of 2708 cases were laboratory-confirmed using immunofluorescence assays and viral cultures, with the most commonly detected being RSV (1913, 70.6%), parainfluenza viruses (357, 13.2%), influenza viruses (297, 11.0%), and adenovirus (141, 5.2%). Children infected with RSV were significantly younger, and children infected with influenza viruses were significantly older. The four main viruses caused disease throughout the year, with a seasonal peak observed for RSV in September-December. Monthly RSV cases were directly correlated with rain days, and inversely correlated with relative humidity and temperature. CONCLUSION: Viral RTIs, particularly due to RSV, are commonly detected in respiratory samples from hospitalized children in Kuala Lumpur, Malaysia. As in temperate countries, RSV infection in tropical Malaysia also caused seasonal yearly epidemics, and this has implications for prophylaxis and vaccination programmes.

Enterovirus 71 outbreak, Brunei.

Enterovirus 71 (EV71) outbreaks occur periodically in the Asia-Pacific region. In 2006, Brunei reported its first major outbreak of EV71 infections, associated with fatalities from neurologic complications. Isolated EV71 strains formed a distinct lineage with low diversity within subgenogroup B5, suggesting recent introduction and rapid spread within Brunei.

The Use of NS1 Rapid Diagnostic Test and qRT-PCR to Complement IgM ELISA for Improved Dengue Diagnosis from Single Specimen.

Timely and accurate dengue diagnosis is important for differential diagnosis and immediate implementation of appropriate disease control measures. In this study, we compared the usefulness and applicability of NS1 RDT (NS1 Ag Strip) and qRT-PCR tests in complementing the IgM ELISA for dengue diagnosis on single serum specimen (n = 375). The NS1 Ag Strip and qRT-PCR showed a fair concordance (κ = 0.207, p = 0.001). While the NS1 Ag Strip showed higher positivity than qRT-PCR for acute (97.8% vs. 84.8%) and post-acute samples (94.8% vs. 71.8%) of primary infection, qRT-PCR showed higher positivity for acute (58.1% vs. 48.4%) and post-acute (50.0% vs.41.4%) samples in secondary infection. IgM ELISA showed higher positivity in samples from secondary dengue (74.2-94.8%) than in those from primary dengue (21.7-64.1%). More primary dengue samples showed positive with combined NS1 Ag Strip/IgM ELISA (99.0% vs. 92.8%) whereas more secondary samples showed positive with combined qRT-PCR/IgM ELISA (99.4% vs. 96.2%). Combined NS1 Ag Strip/IgM ELISA is a suitable combination tests for timely and accurate dengue diagnosis on single serum specimen. If complemented with qRT-PCR, combined NS1 Ag Strip/IgM ELISA would improve detection of secondary dengue samples.

Negative cross-reactivity of rabbit anti-Malassezia furfur antibodies with other yeasts.

Anti-Malassezia furfur monospecific polyclonal antibodies was produced by repeated immunization of rabbit with Malassezia furfur yeast cells mixed with Freud adjuvant. The antibody titres of respective rabbit's serum samples prior to and after each immunization against M. furfur were assayed by indirect immunofluorescence technique using the M. furfur whole yeast antigen fixed in Teflon coated slides. The highest anti-M. furfur antibody titre achieved was 1 in 1280 dilution. At 1:20 dilution, none of the respective serum samples taken at various stages of immunization gave positive immunofluorescent staining against any of the other species of yeasts tested in this study. Anti-M. furfur monospecific polyclonal antibodies produced in rabbit in this study has the potential for diagnostic application in immunohistochemical detection of M. furfur in human tissues.

Isolation of Nipah virus from Malaysian Island flying-foxes.

In late 1998, Nipah virus emerged in peninsular Malaysia and caused fatal disease in domestic pigs and humans and substantial economic loss to the local pig industry. Surveillance of wildlife species during the outbreak showed neutralizing antibodies to Nipah virus mainly in Island flying-foxes (Pteropus hypomelanus) and Malayan flying-foxes (Pteropus vampyrus) but no virus reactive with anti-Nipah virus antibodies was isolated. We adopted a novel approach of collecting urine from these Island flying-foxes and swabs of their partially eaten fruits. Three viral isolates (two from urine and one from a partially eaten fruit swab) that caused Nipah virus-like syncytial cytopathic effect in Vero cells and stained strongly with Nipah- and Hendra-specific antibodies were isolated. Molecular sequencing and analysis of the 11,200-nucleotide fragment representing the beginning of the nucleocapsid gene to the end of the glycoprotein gene of one isolate confirmed the isolate to be Nipah virus with a sequence deviation of five to six nucleotides from Nipah virus isolated from humans. The isolation of Nipah virus from the Island flying-fox corroborates the serological evidence that it is one of the natural hosts of the virus.

Echovirus 7 associated encephalomyelitis.

BACKGROUND: Hand, foot, and mouth disease (HFMD) is endemic in Malaysia. In 1997, a large outbreak of enterovirus 71 (EV-71) associated HFMD resulted in 41 deaths due to severe left ventricular dysfunction and central nervous system infection with extensive damage to the medulla and pons. The clinical presentation in all these patients were rapid cardio-respiratory decompensation leading to cardiac arrest. Another large outbreak of HFMD with 55 fatal cases and a similar clinical picture was reported in Taiwan in 1998. In 2000, an outbreak of HFMD resulted in the deaths of three children who had rapid cardio-respiratory decompensation and one child who survived a central nervous system infection. OBJECTIVES: We set out to study the etiologic agent and mechanism involved in three children who presented to our hospital, two of whom died and one survived a central nervous system infection. STUDY DESIGN: The clinical course of the disease was described. Throat, rectal swab and cerebrospinal fluid samples were subjected to viral isolation and viral isolates were identified by immunofluorescence, micro-neutralisation using human rhabdomyosarcoma (RD) cells, and reverse transcritpase polymerase chain reaction. Magnetic resonance imaging was performed on two of the patients. RESULTS: Echovirus 7 was the sole pathogen isolated from three cases of acute encephalomyelitis, two of which were fatal due to severe left ventricular dysfunction resistant to inotropic support. The survivor had residual bulbar palsy, but is considered to have had a good neurological outcome. CONCLUSION: Echovirus 7 infection associated with encephalomyelitis could be fatal due to indirect involvement of the heart resulting in severe left ventricular dysfunction. In addition one of the children presented with hand, foot, and mouth disease, a syndrome that has not been previously associated with echovirus 7 infection.

Seroprevalence of Malassezia furfur in an urban population in Malaysia.

An in-house prepared M. furfur antigen was used to carry out a seroprevalence study in an urban population in Malaysia by indirect immunofluorescence assay. Of the 800 serum samples from all ages screened, 738 samples were positive for M. furfur specific IgG, giving an overall seropositive rate of 92.3%. There was no significant difference in the seropositive rates among the different gender group and races. However, there was a statistical significant difference in the seropositive rate among different age groups with a lower rate (73%) for the age group 5 years old and below, which increased rapidly to 99% for the 16 to 20 years old age group but declined slightly for the oldest age group. The degree of seropositivity, which semi-quantitatively reflect the anti-M. furfur specific IgG titre, did not show any significant difference among the gender and racial groups. On the other hand, there was a significant difference in the degree of seropositivity among the various age groups, with the 16 to 20 years old age group having the highest antibody titre and the extreme of age groups having the lower antibody titre.

Displacement of predominant respiratory syncytial virus genotypes in Malaysia between 1989 and 2011.

From 1989 to 2011 in Kuala Lumpur, Malaysia, multiple genotypes from both respiratory syncytial virus (RSV) subgroups were found co-circulating each year. RSV-A subgroup predominated in 12 out of 17years with the remaining years predominated by RSV-B subgroup. Local RSV strains exhibited temporal clustering with RSV strains reported in previous epidemiological studies. Every few years, the existing predominant genotype was replaced by a new genotype. The RSV-A genotypes GA2, GA5 and GA7 were replaced by NA1 and NA2, while BA became the predominant RSV-B genotype. A unique local cluster, BA12, was seen in 2009, and the recently-described ON1 genotype with 72-nt duplication emerged in 2011. Our findings will have important implications for future vaccine intervention.

Real-time polymerase chain reaction for diagnosis and quantitation of negative strand of chikungunya virus.

Quantitative real-time polymerase chain reaction (qRT-PCR) is useful for diagnosis and studying virus replication. We developed positive- and negative-strand qRT-PCR assays to detect nsP3 of chikungunya virus (CHIKV), a positive-strand RNA alphavirus that causes epidemic fever, rash, and arthritis. The positive- and negative-strand qRT-PCR assays had limits of quantification of 1 and 3 log10 RNA copies/reaction, respectively. Compared to a published E1 diagnostic assay using 30 laboratory-confirmed clinical samples, the positive-strand nsP3 qRT-PCR assay had higher R(2) and efficiency and detected more positive samples. Peak viral load of 12.9 log(10) RNA copies/mL was reached on day 2 of illness, and RNA was detectable up to day 9, even in the presence of anti-CHIKV IgM. There was no correlation between viral load and persistent arthralgia. The positive-strand nsP3 assay is suitable for diagnosis, while the negative-strand nsP3 assay, which uses tagged primers to increase specificity, is useful for study of active viral replication kinetics.

Chikungunya virus of Asian and Central/East African genotypes in Malaysia.

BACKGROUND: Chikungunya virus (CHIKV) of the Central/East African genotype has caused large outbreaks worldwide in recent years. In Malaysia, limited CHIKV outbreaks of the endemic Asian and imported Central/East African genotypes were reported in 1998 and 2006. Since April 2008, an unprecedented nationwide outbreak has affected Malaysia. OBJECTIVE: To study the molecular epidemiology of the current Malaysian CHIKV outbreak, and to evaluate cross-neutralisation activity of serum from infected patients against isolates of Asian and Central/East African genotypes. STUDY DESIGN: Serum samples were collected from 83 patients presenting in 2008, and tested with PCR for the E1 gene, virus isolation, and for IgM. Phylogenetic analysis was performed on partial E1 gene sequences of 837bp length. Convalescent serum from the current outbreak and Bagan Panchor outbreak (Asian genotype, 2006) were tested for cross-neutralising activity against representative strains from each outbreak. RESULTS: CHIKV was confirmed in 34 patients (41.0%). The current outbreak strain has the A226V mutation in the E1 structural protein, and grouped with Central/East African isolates from recent global outbreaks. Serum cross-neutralisation activity against both Central/East African and Asian genotypes was observed at titres from 40 to 1280. CONCLUSIONS: The CHIKV strain causing the largest Malaysian outbreak is of the Central/East African genotype. The presence of the A226V mutation, which enhances transmissibility of CHIKV by Aedes albopictus, may explain the extensive spread especially in rural areas. Serum cross-neutralisation of different genotypes may aid potential vaccines and limit the effect of future outbreaks.

Reemergence of endemic Chikungunya, Malaysia.

Chikungunya virus infection recently reemerged in Malaysia after 7 years of nondetection. Genomic sequences of recovered isolates were highly similar to those of Malaysian isolates from the 1998 outbreak. The reemergence of the infection is not part of the epidemics in other Indian Ocean countries but raises the possibility that chikungunya virus is endemic in Malaysia.

Isolation of Waddlia malaysiensis, a novel intracellular bacterium, from fruit bat (Eonycteris spelaea).

An obligate intracellular bacterium was isolated from urine samples from 7 (3.5%) of 202 fruit bats (Eonycteris spelaea) in peninsular Malaysia. The bacterium produced large membrane-bound inclusions in human, simian, and rodent cell lines, including epithelial, fibroblastlike, and lymphoid cells. Thin-section electron microscopy showed reticulate bodies dividing by binary fission and elementary bodies in the inclusions; mitochondria surrounded the inclusions. The inclusions were positive for periodic acid-Schiff stain but could not be stained by fluorescein-labeled anti-Chlamydia trachomatis major outer membrane protein monoclonal antibody. The bacterium was resistant to penicillin and streptomycin (MICs > 256 mg/L) but susceptible to tetracycline (MIC = 0.25 mg/L) and chloramphenicol (MIC = 0.5 mg/L). Sequence analysis of the 16SrRNA gene indicated that it was most closely related to 2 isolates of Waddlia chondrophila (94% and 96% identity). The 16S and 23S rRNA gene signatures were only 91% identical. We propose this novel bacterium be called W. malaysiensis.