1.The implication of amino acid mutations at flavivirus NS1-2A cleavage site on NS1’protein production
Siti Nor Khadijah Addis ; Jayaram Bettadapura
Malaysian Journal of Microbiology 2015;11(4):398-402
Aims: The presence of a C-terminally extended form of NS1 (NS1’ protein) has been previously reported in encephalitic
flaviviruses, due to the presence of -1 programmed ribosomal frameshift at the N-terminal of NS2A protein. This present
study is aimed to further confirm that the NS1’ protein production is independent of the authentic cleavage at NS1-2A
junction.
Methodology and results: Six different constructs (P1-Leu, P2-Asp, P3-Phe, P3-Leu, P3-Gly and P5-8 Ala) containing
various mutations at conserved and variable amino acids at C-terminal of NS1 protein were generated by site-directed
mutagenesis and analysed with transient polyprotein expression assay. While analysis on the NS1-2A cleavage of the
mutants exhibited extremely poor to efficient cleavage ranging from 6-89%, significant amount of NS1’ being expressed
in all mutants irrespective of their NS1-2A cleavage outcome.
Conclusion, significance and impact study: In this analysis, we showed for the first time that the abolishment of the
authentic NS1-2A cleavage in Murray Valley encephalitis virus (MVEV) did not impact on NS1’ production. This
observation extend on previous studies to show that NS1 and NS2A proteins are the product of NS1-2A cleavage which
is catalysed by an unknown host protease while NS1’ protein is a product of ribosomal frameshift, independent of the
authentic cleavage at NS1-2A junction.
Flavivirus
2.Virulence evaluation of entomopathogenic fungi to subterranean termites, Globitermes sulphureus (INSECTA: ISOPTERA)
Wahizatul Afzan Azmi ; Zaidatul Akma Sulaiman ; Insyirah Ishak ; Pong Kuan Kin ; Grace Lee Earn Lin ; Siti Nor Khadijah bt. Addis
Malaysian Journal of Microbiology 2016;12(6):492-497
Aims: Subterranean termites, Globitermes sulphureus is one of the significant pests for agricultural crops such as
coconut and oil palm, and occasionally attacks building structure in Malaysia. Efforts to control subterranean termite
infestations depended heavily on liquid termiticide applications. Natural pathogen of termites such as entomopathogenic
fungi (EPF) is a promising alternative to chemical control. The objective of this study was to determine the most virulent
EPF such as Metarhizium anisopliae, Beauveria bassiana and Paecilomyces sp. against the subterranean termites, G.
sulphureus for the development of bio-insecticide for future use of termite control.
Methodology and results: Subterranean termites were collected from mound-building termites found in Universiti
Malaysia Terengganu (UMT). Cultivating, harvesting and counting of conidia of EPF were carried out to prepare the
desired concentrations for screening test and bioassays, which were 1×103
, 1x105
, 1×107 and control. The pathogenicity
testing was observed daily within 1 week under laboratory conditions. Screening showed that M. anisopliae was found to
be the most virulent compared to B. bassiana and Paecilomyces sp., achieving 100% mortality within 3-4 days. M.
anisopliae was then further tested on termites and it was found that concentration of 1×107 showed the lowest LT50
value, while LC50 of M. anisopliae in 1 day was 2.0151×106
.
Conclusion, significance and impact of study: It could be concluded that M. anisopliae is the most virulent EPF
against termites and the most effective concentration was ±107
followed by strains of B. bassiana and Paecilomyces sp.
However, there is limited field evaluation of EPF against termites in Malaysia. Evaluation on the efficiency of M.
anisopliae in the field should be conducted so that its efficacy could be proven and marketed.
3.Molecular identification of antibiotic-resistant bacteria isolated from used contact lens cases
Siti Nor Khadijah Addis ; Nurfarhana Rosli ; Fatimah Hashim ; Amina Rusli ; Dharane Kethiravan ; Asmadamia Abdul Aziz
Malaysian Journal of Microbiology 2021;17(3):305-312
Aims:
The contact lens (CL) has become one of the most convenience refractive devices used in vision correction,
occupational and in cosmetics purposes. Despite the convenience of CL usage, poor hygiene might cause eye infections
due to microbial contamination. In this work, a random collection of used CL cases among Universiti Malaysia
Terengganu (UMT) students had shown the emergence of antibiotic-resistant bacteria towards commonly used
antibiotics to treat eye infections.
Methodology and results:
The study was carried out from 28 CL cases samples with the duration of one to three
months of use. Bacteria that were successfully isolated from the CL cases were then exposed to the commonly
prescribed antibiotics followed by identification through the partial 16S rDNA sequencing. Our finding exhibited that the
rate of contamination is over 50% where 32 bacteria were isolated, with 20 (62.5%) of the isolates were Gram-positive
bacteria. Approximately 31% of the isolated bacteria are resistant and intermediate resistant to the commonly used
antibiotics to treat eye infection, especially erythromycin and chloramphenicol. The isolated bacteria were genotypic
identified as Bacillus cereus, B. anthracis, Acinetobacter variabilis, Klebsiella pneumoniae, and Serratia marcescens.
These bacteria are known as a common cause for microbial keratitis, except for A. variabilis, where the association of
this bacteria in causing microbial keratitis is relatively rare.
Conclusion, significance and impact of study
This study highlights the emergence of antibiotic-resistant bacteria that
can cause severe eye infections among CL wearer. The high percentage of contamination (>50%) found from the
isolates reflected on the lack of hygiene practice on the CL handling. Thus, it is crucial to perceive this study as microbial
contamination will lead to more serious eye infection disease such as conjunctivitis and keratitis.
Drug Resistance, Bacterial
;
Contact Lenses
4.First detection of Shiga toxin producing Escherichia coli O157:H7 (HlyA gene) and enumeration of most probable number (MPN) of fecal coliforms and Escherichia coli in cage cultured oysters (Crassostrea iredalei) and water from southern Malaysia
Tee Ka Hong ; George Bobby ; Nurshafiqah Norizan ; Nurshuhada Ariff ; Siti Nor Khadijah Addis ; Najiah Musa ; Sandra Catherine Zainathan
Malaysian Journal of Microbiology 2021;17(4):390-402
Aims:
Escherichia coli O157:H7 is known to be transmitted via fecal-oral route, where water plays a role in the
transmission process. Oysters as bivalves, bio accumulate pathogens from the water through filter feeding and are
suspected to play a role as disease transmission vector. In Malaysia, the data on oyster’s microbiological quality are
limited. Hence, it was vital to conduct oyster related studies in Malaysia. The main objectives of this study include the
enumeration of most probable number (MPN) of fecal coliforms and E. coli and isolation of E. coli from oyster
(Crassostrea iredalei) and water sample for the detection of 16S rRNA and HlyA (Hemolysin A) genes of E. coli
O157:H7.
Methodology and results:
A total of 120 oysters and water samples (n=6) were collected from a fisherman village
located in southern Malaysia. Total fecal coliforms and E. coli were determined using the MPN procedure. Colonies of E.
coli were identified based on Gram staining, biochemical test, and PCR detection for the presence of 16S rRNA and
HlyA gene of E. coli O157:H7. The enumeration results showed that the MPN of the fecal coliforms and E. coli found in
the collected oyster samples do not meet the standard to be directed for human consumption (0.72 ± 0.19 × 104
MPN/100 g and 0.13 ± 0.03 × 10
4 MPN/100 g, respectively). The PCR assays showed that 16 out of the 104 (15.38%) of
E. coli isolated from water and oysters showed the presence of HlyA gene. The phylogenetic tree analysis showed there
were genetic relationships between the HlyA gene of the E. coli isolated in this study with the ones isolated from calf and
human faeces.
Conclusion, significance and impact of study
The detection of Shiga toxin producing E. coli O157:H7 (HlyA gene) in
cage cultured oysters (C. iredalei) and water from southern Malaysia was first time reported here. In the future, more
study can be conducted to study the expression of the HlyA gene and confirm of its identity as E. coli O157:H7 using
different target genes such as eaeA (encodes a 94 kD outer membrane protein called intimin) and Stx1 (Shiga toxin,
Shigella dysenteriae type 1).
Escherichia coli O157
;
Crassostrea