1.Violet-pigmented Burkholderia contaminans sequence type 922 bacteremia in an end-stage renal disease patient – a case report and review of the literature
Ahmad S. ; Mohd Sukhaimi N.A. ; Shahimi S.S. ; Mahfodz N.H. ; Soh Y.H. ; AbuBakar S. ; Choong K.Y. ; Loong S.K.
Tropical Biomedicine 2026;43(No. 1):1-4
Burkholderia cepacia complex (Bcc) is an emerging nosocomial pathogen, with violet-pigmented
strains representing a rare and possibly neglected but clinically important subset. We report a case
of a 62-year-old man with end-stage renal disease on dialysis who presented with fever and cough.
Blood cultures from central and peripheral lines grew violet-pigmented, non-lactose fermenting
colonies on MacConkey agar, later identified as Burkholderia contaminans sequence type 922 (ST922)
via a multimodal approach. Initial phenotypic methods (VITEK-2, API20NE and MALDI-ToF) and 16S
rDNA sequencing were inconclusive; however, multilocus sequence typing confirmed ST922, a strain
previously reported in India and associated with nosocomial outbreaks. The isolate was susceptible to
ceftazidime, trimethoprim/sulfamethoxazole, minocycline, and meropenem. The patient responded
well to intravenous ceftazidime, with subsequent blood cultures yielding no growth. Notably,
antimicrobial susceptibility varied geographically, with some ST922 isolates resistant to third-generation
cephalosporins. This case illustrates the diagnostic challenges in Bcc speciation and highlights the value
of molecular tools such as MLST. The detection of this strain in Malaysia raises concerns about global
dissemination, potentially via contaminated medical devices or water systems. Early recognition of
violet-pigmented Bcc in resource-limited settings can facilitate prompt, targeted treatment. This report
underscores the need for environmental surveillance and antimicrobial stewardship to prevent spread,
while reinforcing Bcc’s ecological adaptability and clinical significance, especially in immunocompromised
individuals.
2.Sustained antibody response to a linear epitope of Nipah virus fusion protein in human survivor serum samples
Ting L.J ; Tan X.L. ; Tiong V. ; Abubakar S. ; Abdullah I. ; Karsani S.A. ; Chan K-G. ; Chua K-O ; Yong H-S. ; Liew Y.J.M.
Tropical Biomedicine 2026;43(No. 1):5-15
Nipah virus (NiV), a pathogen with pandemic potential, lacks approved treatments or vaccines,
highlighting the urgent need for research on immune-targeted antigenic determinants. A significant
gap persists in NiV research, as studies on the fusion (F) protein critical for viral entry as well as the B
cells epitopes, have primarily focused on computational prediction rather than experimental validation
of immunogenic epitopes obtained through immunoinformatics approach. This study focused on the
conserved F protein across NiV human isolates and employed an immunoinformatics approach to
predict linear B-cell epitopes capable of direct immune activation. Predicted epitopes were screened
for antigenicity, toxicity, and allergenicity. Molecular docking analysis was performed to evaluate
its binding affinity with B-cell receptors (BCRs). To validate its immunogenicity, the LF6 peptide was
synthesized and used in an indirect ELISA to test sera from cohort previously infected with NiV as well
as with negative cohort. Epitope LF6 (LISNIEIGFCL) was identified as a strong candidate based on its
immunogenic properties. Molecular docking showed favorable binding of LF6 with BCR. ELISA results
revealed that one sera from the survival cohort showed positive response which is an IgG antibody
response 2-fold higher (0.343) than the cut-off value (0.0171). This study provides the first reported
evidence linking computational predictions with functional immune reactivity for a B-cell epitope of
NiV. The findings suggest that LF6 has the potential to elicit specific immune responses. However, given
the small sample size, further validation in larger cohorts is essential to confirm LF6’s vaccine relevance.
3.Sunlight exposure might account for the relatively low COVID-19 morbidity and mortality in tropical countries
Muhammad, M. ; Loong, S.K. ; Khor, C.S. ; Mohd-Azami, S.N.I. ; Kafle, A. ; Useh, U. ; Bello, B. ; AbuBakar, S.
Tropical Biomedicine 2024;41(No.1):78-83
The present study aimed at exploring whether sunlight exposure might account for the relative
difference in COVID-19-related morbidity and mortality between tropical and non-tropical countries.
A retrospective observational study was designed and data from the World Health Organization
weekly COVID-19 epidemiological update was compiled. We examined the total number of confirmed
COVID-19 cases per 100 000 population, as well as the total number of COVID-19-related mortalities
per 100 000 population. Solar variables data were obtained from the Global Solar Atlas website
(https://globalsolaratlas.info/). These data were analyzed to determine the association of sunlight
exposure to COVID-19-related morbidity and mortality in tropical and non-tropical countries. Results
revealed a statistically significant decrease in the number of confirmed COVID-19 cases per 100 000
population (P<0.001), as well as the number of COVID-19-related mortalities per 100 000 population
(P<0.001) between tropical and non-tropical countries. Analyses of sunlight exposure data found that
specific photovoltaic power output, global horizontal irradiation, diffuse horizontal irradiation and
global tilted irradiation at optimum angle were significantly inversely correlated to COVID-19-related
morbidity and mortality. This suggests that stronger sunlight exposure potentially leads to lower
COVID-19-related morbidity and mortality. Findings from this study suggest that the relatively low
COVID-19-related morbidity and mortality in tropical countries were possibly due to better sunlight
exposure that translates into adequate vitamin D status.
4.Impact of elevated IgE in protective immunity and immunopathology of dengue
Annsley, D.S. ; Chin, K.L. ; Tan, K.K. ; AbuBakar, S. ; Zainal, N.
Tropical Biomedicine 2024;41(No.1):118-124
Dengue is a mosquito-transmitted infection endemic in tropical and subtropical locations of the world
where nearly half of the world’s population resides. The disease may present as mild febrile illness to
severe and can even be fatal if untreated. There are four genetically related but antigenically distinct
dengue virus (DENV) serotypes. Immune responses to DENV infection are in general protective but
under certain conditions, they can also aggravate the disease. The importance of the cellular immune
responses and the antibody responses involving IgG and IgM has been well-studied. In contrast, not
much has been described on the potential role of hypersensitivity reactions involving IgE in dengue.
Several studies have shown elevated levels of IgE in patients with dengue fever, but its involvement
in the immune response against the virus and disease is unknown. Activation of mast cells (MCs) and
basophils mediated through dengue-specific IgE could result in the release of mediators affecting dengue
virus infection. The present review explores the relationships between the induction of IgE in dengue
virus infection, and the potential role of MCs and basophils, exploring both protective and pathogenic
aspects, including antibody-dependent enhancement (ADE) of infection in dengue.
5.Experimental infection of tick cells with Nipah virus
Phoon, W.H. ; Bell-Sakyi, L. ; AbuBakar, S. ; Chang, L.Y.
Tropical Biomedicine 2023;40(No.1):29-36
Nipah virus (NiV), a highly pathogenic henipavirus of the family Paramyxoviridae, which causes fatal
encephalitis in 40-70% of affected patients, was first reported in Malaysia over 20 years ago. Pteropid
bats are the natural hosts of henipaviruses, and ticks have been proposed as a possible link between
bats and mammalian hosts. To investigate this hypothesis, infection of the tick cell line IDE8 with NiV
was examined. Presence of viral RNA and antigen in the NiV-infected tick cells was confirmed. Infectious
virions were recovered from NiV-infected tick cells and ultrastructural features of NiV were observed
by electron microscopy. These results suggest that ticks could support NiV infection, potentially playing
a role in transmission.
6.Lactic acid bacteria waste infusion as a source of attraction and oviposition stimulation of gravid female Aedes albopictus mosquitoes
Suria, M.M. ; Yap, P.C. ; Low, V.L. ; AbuBakar, S. ; Lee, H.Y.
Tropical Biomedicine 2022;39(No.4):499-503
The Plasmodium knowlesi secreted protein with an altered thrombospondin repeat (PkSPATR) is an
important protein that helps in the parasite’s invasion into the host cell. This protein has been regarded
as one of the potential vaccine candidates against P. knowlesi infection. This study investigates the
genetic diversity and natural selection of PkSPATR gene of P. knowlesi clinical isolates from Malaysia.
PCR amplification of the full length PkSPATR gene was performed on 60 blood samples of infected P.
knowlesi patients from Peninsular Malaysia and Malaysian Borneo. The amplified PCR products were
cloned and sequenced. Sequence analysis of PkSPATR from Malaysia showed higher nucleotide diversity
(CDS p: 0.01462) than previously reported Plasmodium vivax PvSPATR (p = 0.0003). PkSPATR from
Peninsular Malaysia was observed to have slightly higher diversity (CDS p: 0.01307) than those from
Malaysian Borneo (CDS p: 0.01212). Natural selection analysis on PkSPATR indicated significant purifying
selection. Multiple amino acid sequence alignment revealed 69 polymorphic sites. The phylogenetic
tree and haplotype network did not show any distinct clustering of PkSPATR. The low genetic diversity
level, natural selection and absence of clustering implied functional constrains of the PkSPATR protein.
7.Average treatment effects of a single-dose antenatal corticosteroid on the respiratory morbidity of Filipino preterm neonates
Alvin Duke R. Sy ; Abubakar S. Asaad
Acta Medica Philippina 2022;56(16):71-77
Introduction:
Prematurity-related respiratory disorders are an important public health concern that should be
treated efficiently and effectively. Antenatal corticosteroid (ACS) therapy has been recommended to hasten fetal
lung maturation in pregnancies at risk but has not been delivered adequately in low to middle-income countries. This study aimed to estimate the treatment effects associated with the use of a single-dose antenatal corticosteroid on the incidence of respiratory-associated morbidity among prematurely delivered neonates.
Methods:
This was a retrospective cohort study of neonates delivered at 24 to 33 weeks gestation at a tertiary
hospital comparing outcomes in those given single-dose ACS with those given no ACS. Association was estimated using logistic and propensity score (PS) analyses, as well as average treatment effect (ATE) and among those treated (ATET).
Results:
Most neonates (78.11%) received a single dose before delivery (single-dose ACS group) and only a few
(21.89%) did not receive any dose (no ACS dose group). The odds ratio of respiratory morbidity in the single-dose ACS group was 0.44 (0.23-0.84) from an adjusted logistic regression model and 0.33 (0.17-0.80) from the PS matching model. The latter model was used to estimate that the average treatment effect from a single-ACS dose on the entire sample was -0.09 (-0.03 to -0.15), while its effect among the actual recipients was -0.08 (-0.02 to -0.15).
Conclusion
There is a small benefit attributed to the single-dose ACS, reinforcing the need for dose administration and completion. Future studies are recommended to clarify the estimated association and improve on the methodological constraints encountered.
Morbidity
;
Propensity Score
8.Propensity score approaches in quantifying effects of treatment from observational data
Alvin Duke R. Sy ; Abubakar S. Asaad
Acta Medica Philippina 2022;56(16):96-107
Introduction:
Despite the growing popularity of utilizing observational studies for determining associations with public health implications, there is limited literature using them for examining and quantifying the effects of exposures or treatments: The study compared traditional regression with scoring approaches in estimating treatment effects considering the noted limitations in the dataset.
Methods:
We conducted a secondary analysis of previously collected retrospective cohort data derived from
maternal-neonatal dyads delivered prematurely in a tertiary hospital. Propensity scores (PS) were estimated using logistic and boosting regression. These scores were implemented into matching, stratification, and weighting models. The estimated measures of effect from traditional regression and PS-adjusted models were compared using certain metrics (i.e., the width of CI, SE, AIC, BIC). Sensitivity analysis was also performed.
Results:
We included data from 562 patients (123 untreated and 439 treated). Both the estimated scores demonstrated satisfactory fit and reduction in the standardized differences between the groups. However, the logit-estimated scores had better prediction (AUC: 0.71 vs 0.66) and forecasting properties (Brier: 0.15 vs 0.17) than the boosting-estimated scores. All generated statistical models demonstrated a reduction in the occurrence of respiratory morbidity among preterm neonates exposed to a single-dose antenatal corticosteroid (ACS) (ORs ranged from 0.37 to 0.59). The estimated average treatment effects (ATE) and effect among those treated (ATET) from various models suggested a small benefit attributed to the single-dose ACS (ATEs range from -0.09 to -0.41; ATETs range from -0.07 to -0.17).
Conclusion
PS estimated using logistic regression performed better than those estimated using machine learning strategies. The matching model using the said scores demonstrated better fit and parsimony over conventional and propensity-adjusted models. Future studies are recommended to improve the application of these analytic techniques in real-world data.
Propensity Score
;
Machine Learning
;
Logistic Models
9.Ruxolitinib and the Mitigation of Severe COVID-19: A Systematic Review and Meta-analysis
Jorge R. QUIROS ; Jennifer ROSS-COMPTIS ; Donald Hathaway III ; Azza SARFRAZ ; Zouina SARFRAZ ; Zhanna GRIGORYAN ; Kimberly Anne ROMERO ; Abubakar GAPIZOV ; Fortunato S PRÍNCIPE-MENESES ; Manoj Reddy SOMAGUTTA ; Adrian RIVA-MOSCOSO ; Abdulhusein KAPASI
Infection and Chemotherapy 2021;53(3):436-448
Background:
The cause of end-organ damage and acute respiratory distress syndrome (ARDS) in coronavirus disease 2019 (COVID-19) patients is postulated to be connected to the uncontrolled increase of pro-inflammatory cytokines. The upregulation of many cytokines is dependent on signaling through the Janus kinase 1 (JAK-1) and JAK-2 pathways. Ruxolitinib, a JAK-1 and JAK-2 inhibitor, is documented to have potent anti-inflammatory activity by targeting several cytokines and growth factors with proposed efficacy in the cytokine storm observed in severe COVID-19 patients; therefore, this study examines the efficacy and tolerability of ruxolitinib for adult COVID-19 patients.
Materials and Methods:
This review was conducted using preferred reporting items for aystematic reviews and meta-analyses (PRISMA) methodology. Six reviewers analyzed 1,120 results. Seven studies were selected and validated. A quantitative meta-analysis was further performed to evaluate clinical improvement at day 28, mortality at day 28, and oxygen requirements comparing treatment and standard of care groups.
Results:
168 individuals were involved in the studies selected: 122 in cohort studies, 4 in case reports, and 41 in randomized controlled studies. The ruxolitinib group had a higher likelihood of clinical improvement by the 28th day of treatment when assessed with the standard of care (SOC) group (odds ratio [OR]: 1.48; 95% confidence interval [CI]: 0.53 -4.16; P = 0.45; I2 = 0%). The SOC group was at a higher risk of experiencing serious adverse events (OR: 0.17; 95% CI: 0.03 - 1.13; P = 0.07). Notably the SOC group had a higher likelihood of death (OR: 0.51; 95% CI: 0.11-2.29; P = 0.07; I2= 0%).
Conclusion
Prior studies on ruxolitinib have demonstrated it is able to decrease inflammatory markers. In recent studies on COVID-19, treatment with ruxolitinib decreased the time on mechanical ventilation, hospitalization time, and the need for vasopressor support. Additionally, ruxolitinib showed decreased mortality and demonstrated improvement in lung congestion as evidenced by computerized tomography imaging. These findings warrant further clinical investigation into Ruxolitinib as a potential treatment approach for severe COVID-19.
10.Evaluation of commercial serological assays in Malaysia for detection of anti-Zika virus antibodies
Khoo, H.Y. ; Lee, H.Y. ; Khor, C.S. ; Tan, K.K. ; AbuBakar, S.
Tropical Biomedicine 2021;38(No.4):613-621
The recommended test guidelines for Zika virus (ZIKV) include using both molecular and
serological tools. While the molecular tools are useful for detecting acute infection, the
serological tools are useful for the detection of previous infections. Nevertheless, detection
of ZIKV-specific antibodies remains a challenge due to the high cross-reactivity between
ZIKV and other flaviviruses such as dengue virus (DENV) and Japanese encephalitis virus
(JEV). The objective of this study is to evaluate the commercially available enzyme-linked
immunosorbent assay (ELISA) for the detection of ZIKV IgG. In this study, we evaluated 6
commercially available anti-ZIKV IgG ELISA kits. Pre-characterized serum panels consisting
of 70 sera were selected for the evaluation. The diagnostic accuracy of each ELISA kits was
determined and compared to the gold standard, Foci Reduction Neutralization Test (FRNT).
The present study established that the performance of the NS1-based anti-ZIKV IgG ELISA kit
was superior to that which uses of the E protein as antigen. Overall, commercial ZIKV IgG
ELISA showed varying test performances, with some achieving moderate to high test
sensitivities and specificities. When compared against the FRNT, the test sensitivities ranged
from 7.1% to 78.6%, whereas, the test specificities ranged from 40.0% to 100%. Limitation to
the study includes the cross reactivity between flavivirus and specificity of the kit in
addressing the cross reactivity.


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