1.Interplay of interleukins (IL6, IL10) and 25 hydroxycholecalciferol in asthmatic subjects with chronic post-COVID condition (PCC)
Jaleel, A. ; Namoos, K. ; Asim, S. ; Uppal, S.S. ; Zaman, S. ; Irfan, H. ; Pervaiz, S. ; Tariq, M. ; Shafique, M.
Tropical Biomedicine 2024;41(No.1):70-77
The study aimed to compare and correlate serum levels of IL-6, 10, and 25-hydroxycholecalciferol
in individuals with asthma with and without post-COVID condition (PCC). The study was designed
to investigate the inflammatory response and serum 25-hydroxycholecalciferol status in asthmatics
with and without PCC. A cross-sectional study of 252 subjects (128 asthmatics and 124 non-asthmatic
subjects) was carried out. Interleukins and 25-hydroxycholecalciferol levels were estimated on ELISA.
The principle findings were that IL-6 and 25-hydroxycholecalciferol levels were significantly increased
(p<0.001), while IL-10 levels were non-significant in asthmatics with PCC compared to those without PCC.
However, 25-hydroxycholecalciferol levels were significantly increased, but no significant change was
observed in IL-6, and IL-10 levels in non-asthmatics with and without chronic PCC. A significant positive
correlation (r = 0.258) was found between 25-hydroxycholecalciferol and IL-6 but a significant negative
correlation (r = -0.227) with IL-10 in asthmatics with PCC. Similarly, a significant negative correlation (r
= -0.285) was found between 25-hydroxycholecalciferol and IL-10 but was non-significant with IL-6 in
asthmatics without PCC. The correlation of 25-hydroxycholecalciferol with IL-10 was significant (0.683),
but IL-6 was non-significant in non-asthmatics with PCC. Multiple regression analysis showed that age,
IL-6, gender, and PCC were significantly related in adjusted values to 25-hydroxycholecalciferol. This
study sheds light on the complex liaison between 25-hydroxycholecalciferol levels and inflammatory
responses in asthmatics, especially those with PCC. The findings suggest that although asthmatics with
PCC maintain sufficient levels of 25-hydroxycholecalciferol, they show a substantial increase in the proinflammatory response. This suggests that PCC exacerbates the pro-inflammatory response in asthma.
Moreover, the study reveals that asthmatics, whether with or without PCC, display a negative correlation
between 25-hydroxycholecalciferol and the anti-inflammatory response. This emphasizes the main
influence of asthma on the overall inflammatory response. These findings reveal a complex interplay
between vitamin D levels and inflammatory mediators in asthmatic individuals with and without PCC.
2.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.
3.Construction of multi-epitope vaccine against the Rhipicephalus microplus tick: an immunoinformatics approach
Younas, M. ; Ashraf, K. ; Ijaz, M. ; Suleman, M. ; Chohan, T.A. ; Rahman, S.U. ; Rashid, M.I.
Tropical Biomedicine 2024;41(No.1):84-96
Rhipicephalus microplus, known as the hard tick, is a vector for the parasites Babesia spp. and
Anaplasma marginale, both of which can cause significant financial losses to the livestock industry.
There is currently no effective vaccine for R. microplus tick infestations, despite the identification of
numerous prospective tick vaccine candidates. As a result, the current research set out to develop
an immunoinformatics-based strategy using existing methods for designing a multi-epitope based
vaccination that is not only effective but also safe and capable of eliciting cellular and humoral immune
responses. First, R. microplus proteins Bm86, Subolesin, and Bm95 were used to anticipate and link B
and T-cell epitopes (HTL and CTL) to one another. Antigenicity testing, allergenicity assessment, and
toxicity screening were just a few of the many immunoinformatics techniques used to identify potent
epitopes. Multi-epitope vaccine design was chosen based on the antigenic score 0.935 that is promising
vaccine candidate. Molecular docking was used to determine the nature of the interaction between TLR2
and the vaccine construct. Finally, molecular dynamic simulation was used to assess the stability and
compactness of the resulting vaccination based on docking scores. The developed vaccine was shown
to be stable, have immunogenic qualities, be soluble, and to have high expression by in silico cloning.
These findings suggest that experimental investigation of the multi-epitope based vaccine designed in
the current study will produce achievable vaccine candidates against R. microplus ticks, enabling more
effective control of infestations.
4.Whole genome sequencing of Streptococcus suis revealed potential drug resistance and zoonotic transmission in companion cat
Lee, C.Y. ; Selvarajah, G.T. ; Zakaria, Z. ; Mustaffa-Kamal, F. ; Gan, H.M. ; Voon, K.G.L. ; Fong, M.W.C ; Ooi, P.T.
Tropical Biomedicine 2024;41(No.1):97-108
Streptococcus suis is a bacterium of clinical importance in diverse animal hosts including companion
animals and humans. Companion animals are closely associated in the living environment of humans
and are potential reservoirs for zoonotic pathogens. Given the zoonotic potential of S. suis, it is crucial
to determine whether this bacterium is present among the companion animal population. This study
aimed to detect Streptococcus suis in companion animals namely cats and dogs of the central west
coast of Peninsular Malaysia and further characterize the positive isolates via molecular and genomic
approach. The detection of S. suis was done via bacterial isolation and polymerase chain reaction assay
of gdh and recN gene from oral swabs. Characterization was done by multiplex PCR serotyping, as well
as muti-locus sequence typing, AMR gene prediction, MGE identification and phylogenomic analysis
on whole genome sequence acquired from Illumina and Oxford Nanopore sequencing. Among the 115
samples, PCR assay detected 2/59 of the cats were positive for S. suis serotype 8 while all screened
dog samples were negative. This study further described the first complete whole genome of S. suis
strain SS/UPM/MY/F001 isolated from the oral cavity of a companion cat. Genomic analysis revealed a
novel strain of S. suis having a unique MLST profile and antimicrobial resistance genes of mefA, msrD,
patA, patB and vanY. Mobile genetic elements were described, and pathogenic determinants matched
to human and swine strains were identified. Phylogenetic tree analysis on the core genome alignment
revealed strain SS/UPM/MY/F001 was distinct from other S. suis strains. This study provided insight
into the detection and genomic features of the S. suis isolate of a companion cat and highlighted its
potential for antimicrobial resistance and pathogenicity.
5.Identification of skin bacterial profiles of early deceased bodies and the relation to post-mortem interval
Chong, C.K. ; Emamjomeh, M. ; Joseph, N. ; Siew, S.F. ; Maeda, T. ; Mustapha, N.A. ; Hoshiko, Y. ; Muthanna, A. ; Amin-Nordin, S.
Tropical Biomedicine 2024;41(No.1):109-117
Post-mortem microbiology (PMM) is an important tool in identifying possible causes of sudden
unexpected death, as an infectious cause is highly suspected. However, contamination is a major problem
in microbiology, and this has increased the difficulty determining the true pathogen that contributes to
death in post-mortem cases. Skin commensals are common contaminants in blood cultures. This study
was conducted to investigate the skin flora on early deceased bodies and observe the bacteria detected
at different post-mortem intervals (PMIs). As blood is usually drawn from the neck and femoral sites for
PMM examination, the two body sites were chosen as the sampling sites. Skin swab samples from the
neck and femoral (n=80) of each early deceased body were collected by sterile cotton swabs. DNA was
extracted from the swabs and then subjected to high-throughput 16S rRNA sequencing by using the
Illumina MiSeq platform. Staphylococcus was found to be the most dominant genus in both neck and
femoral sites. LEfSe results showed that Cutibacterium is significantly different at the neck site while
Corynebacterium is more abundant at femoral site. There are significant differences at genus level
between PMI<5H and PMI>5H at both neck and femoral sites. The findings of the present study may
act as a reference for microbiologists and forensic pathologists when mixed growth or contamination
occurs in post-mortem blood cultures.
6.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.
7.Population genetics of the biting midge Culicoides oxystoma Kieffer (Diptera: Ceratopogonidae) from Thailand and its genetic relationships with global populations
Pramual, P. ; Jumpato, W. ; Gomontean, B. ; Mintara, R. ; Wannasingha, W. ; Wongpakam, K.
Tropical Biomedicine 2024;41(No.1):125-133
Culicoides oxystoma Kieffer is a vector of viruses, filarial nematodes and protozoa of the genus
Leishmania transmitted to humans and other animals. Understanding genetic diversity, genetic
structure and genetic relationships among geographically widespread populations will provide
important information related to disease epidemiology. In this study, genetic diversity, genetic
structure and genetic relationships between Thai C. oxystoma and those reported from other
countries were inferred based on mitochondrial cytochrome oxidase I (COI) and nuclear internal
transcribed spacer 1 (ITS-1) sequences. A high level of genetic diversity was found in C. oxystoma
from Thailand. The maximum K2P intraspecific genetic divergence for COI gene and ITS-1
sequences were 4.29% and 6.55%, respectively. Despite high genetic diversity, no significant genetic
differentiation was found within the 13 Thai populations. This could be a result of unspecialized
habitat requirement of the larval habitat, abundance and continuous distribution of host blood
sources, potential for long distance movement with host via trading. Mitochondrial genealogy
analysis of the global population of C. oxystoma revealed three (A, B and C) genetically divergent
lineages. Specimens from Thailand were included in the main lineage (A) with those from all
other countries except those from Senegal that formed lineage B and those of Lineage C that was
exclusively found in Bangladesh. The nuclear (ITS-1) genetic markers genealogy indicated that Thai C.
oxystoma belong to the same genetic lineage with those from East, South and Southeast Asia which
presumably the true C. oxystoma.
8.Epidemiological characteristics and strategies for prevention and elimination of malaria in Qingdao, Shandong Province, China from 1949 to 2021
Shi, L.M. ; Liu, S.Z. ; Dou, X.J. ; Liu, X.Y. ; Feng, E.Q. ; Liang, J.W. ; Kong, X.L. ; Ji, F.Y.
Tropical Biomedicine 2024;41(No.2):134-141
Malaria is an insect-borne disease transmitted by Anopheles mosquitoes or the importation of
Plasmodium-infected blood, posing a serious threat to human health and life safety. This study aims
to analyze the incidence of malaria in Qingdao at various stages from 1949 to 2021, to collate the
control measures taken at different epidemic stages to assess the effectiveness of malaria control, and
to identify a set of malaria control strategies suitable for Qingdao, while providing Chinese experience
for other countries or cities in their malaria elimination efforts. A retrospective survey was used to
collect information on malaria cases, control measures and prevention and control effects in Qingdao
from 1949 to 2021, and to evaluate malaria control strategies and measures in Qingdao. 704 155 cases
have been reported from 1949 to 2021, with three epidemic peaks: the incidence rate was 1715.9/100
000 in 1961, 1409.7/100 000 in 1965, and the most severe case occurred in 1972, with an incidence
rate of 1635.6/100 000 and a case count exceeding 90 000. Throughout the various stages of malaria
epidemics, Qingdao has effectively eliminated indigenous malaria by implementing diverse preventive
and control measures. Since the last indigenous case of Plasmodium vivax was reported in 2002, all
locally reported cases have been imported, mainly by returning migrant workers from Africa. This study
examines a range of malaria prevention and control strategies and interventions that are appropriate
for Qingdao. These measures have enabled Qingdao to successfully eliminate malaria and maintain
malaria-free status for more than 20 years. These measures can also serve as a reference for similarly
situated cities in Africa and Southeast Asia.
9.Intravaginally CpG-ODN and Salmonella enteritidis on TLR21, cytokines, and AvBD10 gene expressions in the reproductive tract of native chicken
Suryohastari, R.R.B. ; Sumarsono, S.H. ; Giri-Rachman, E.A. ; Edi, S.P.
Tropical Biomedicine 2024;41(No.2):142-148
Salmonella enterica subsp. enterica serovar Enteritidis (SE) is a global concern for the poultry industry
due to its association with foodborne illnesses. The transmission occurs through the transovarial route
which initiates from colonization in oviducts and ascending to ovaries. Though there are studies on
cytosine-phosphate-guanine oligodeoxynucleotide (CpG-ODN) and the increase of innate immune
response, there is limited research on the intravaginal treatment using CpG-ODN. Previous studies
have shown that stimulating CpG-ODN can induce the production of antimicrobial peptide avian
beta-defensins (AvBDs) in vaginal cell cultures, there is limited information on the use of intravaginal
treatment to induce the innate immune system, particularly in the Kampung Unggul Balitbangtan
(KUB-1) chickens (Gallus gallus domesticus). This study investigates the impact of intravaginal CpG-ODN
stimulation on the innate immune response in KUB-1 chicken ovaries and oviducts when challenged
to SE. A total of 39 KUB-1 chickens were divided into four groups namely T1 (treated with CpG-ODN,
n=12), T2 (SE group, n=12), T3 (CpG-ODN and SE, n=12), and Control (without CpG-ODN and SE, n=3).
Chickens were observed from day 1 to 4 post-intravaginal (PI) inoculation. The results suggest that
intravaginal CpG-ODN treatment modulates AvBD10 production through toll-like receptor (TLR)21, with
interleukin (IL)1B and IL10 playing reciprocal roles, providing insights into the potential of this treatment
to prevent transovarial Salmonellosis in poultry. The novelty of this study adds valuable insights to the
current body of knowledge.
10.Distribution of virulence genes in clinical isolates of hospital-associated and community-associated methicillin-susceptible Staphylococcus aureus from Terengganu, Malaysia
Che Hamzah, A.M. ; Yeo, C.C. ; Puah, S.M. ; Chua, K.H. ; A. Rahman, N.I. ; Ismail, S. ; Abdullah, F.H. ; Othman, N. ; Chew, C.H.
Tropical Biomedicine 2024;41(No.2):149-156
Staphylococcus aureus is a common bacterial pathogen known to cause various kinds of infections due to
its repertoire of virulence factors. This study aimed to investigate the distribution of 19 types of virulence
genes among clinical isolates of methicillin-susceptible S. aureus (MSSA) using the polymerase chain
reaction. A total of 109 MSSA isolates, i.e., 63 hospital-associated (HA) and 46 community-associated (CA)
were collected from Hospital Sultanah Nur Zahirah, the main tertiary hospital in Terengganu, Malaysia,
from July 2016 to June 2017. The most frequent virulence genes detected were hla (78.9%, n=86) and
hld (78.0%, n=85) encoding hemolysins, lukED (56.9%, n=62) encoding leukotoxin ED, followed by seb
(26.6%, n=29) and sea (24.8%, n=27) encoding enterotoxins. Among 34 (31.2%) isolates carrying six
or more virulence genes, only five were multidrug resistant (MDR) while the remaining isolates were
susceptible. Significant associations were discovered between the hld gene with CA-MSSA (p=0.016) and
the seo gene with HA-MSSA (p=0.023). However, there is no significant association between virulence
genes among the different types of infection. The clinical MSSA isolates in Terengganu showed high
prevalence and high diversity of virulence gene carriage.


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