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Oxidative stress resistance and fitness-compensatory response in vancomycin-intermediate Staphylococcus aureus (VISA)

Tan XE, Neoh HM, Cui L, Hiramatsu K, Jamal R

Can J Microbiol, 2019 Aug;65(8):623-628.
PMID: 31063703 DOI: 10.1139/cjm-2019-0048

In this study, vancomycin-intermediate Staphylococcus aureus (VISA) cells carrying vraS and (or) graR mutations were shown to be more resistant to oxidative stress. Caenorhabditis elegans infected with these strains in turn demonstrated lower survival. Altered regulation in oxidative stress response and virulence appear to be physiological adaptations associated with the VISA phenotype in the Mu50 lineage.
Pulsed-field gel electrophoresis (PFGE): A review of the "gold standard" for bacteria typing and current alternatives

Neoh HM, Tan XE, Sapri HF, Tan TL

Infect Genet Evol, 2019 10;74:103935.
PMID: 31233781 DOI: 10.1016/j.meegid.2019.103935

Pulsed-field gel electrophoresis (PFGE) is considered the "gold standard" for bacteria typing. The method involves enzyme restriction of bacteria DNA, separation of the restricted DNA bands using a pulsed-field electrophoresis chamber, followed by clonal assignment of bacteria based on PFGE banding patterns. Various PFGE protocols have been developed for typing different bacteria, leading it to be one of the most widely used methods for phylogenetic studies, food safety surveillance, infection control and outbreak investigations. On the other hand, as PFGE is lengthy and labourious, several PCR-based typing methods can be used as alternatives for research purposes. Recently, matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) and whole genome sequencing (WGS) have also been proposed for bacteria typing. In fact, as WGS provides more information, such as antimicrobial resistance and virulence of the tested bacteria in comparison to PFGE, more and more laboratories are currently transitioning from PFGE to WGS for bacteria typing. Nevertheless, PFGE will remain an affordable and relevant technique for small laboratories and hospitals in years to come.
Fulltext Clonal distribution and possible microevolution of methicillin-resistant Staphylococcus aureus strains in a teaching hospital in Malaysia

Tan XE, Neoh HM, Hussin S, Zin NM

Asian Pac J Trop Biomed, 2013 Mar;3(3):224-8.
PMID: 23620843 DOI: 10.1016/S2221-1691(13)60055-6

OBJECTIVE: To genotypically characterize methicillin-resistant Staphylococcus aureus (MRSA) strains isolated from medical and surgical wards in Universiti Kebangsaan Malaysia Medical Centre (UKMMC) in 2009.
METHODS: MRSA strains were collected and molecularly typed by pulsed-field gel electrophoresis (PFGE).
RESULTS: PFGE typing on 180 MRSA isolated in UKMMC identified 5 pulsotypes (A-E) and 6 singletons, where pulsotypes B and C were suspected to be divergent clones originating from a single ancestor. This study also showed that most MRSA strains were isolated from swab (119 isolates), followed by blood (22 isolates), tracheal aspirate (11 isolates) and sputum (10 isolates). On the other hand, urine and bone isolates were less, which were 4 and 1 isolates, respectively. The distribution of different pulsotypes of MRSA among wards suggested that MRSA was communicated in surgical and medical wards in UKMMC, with pulsotype B MRSA as the dominant strain. Besides, it was found that most deceased patients were infected by pulsotype B MRSA, however, no particular pulsotype could be associated with patient age, underlying disease, or ward of admittance.
CONCLUSIONS: Five pulsotypes of MRSA and 6 singletons were identified, with pulsotype B MRSA as the endemic strains circulating in these wards, which is useful in establishment of preventive measures against MRSA transmission.
Fulltext Stress and its relationship with body mass index among biomedical science students in Kuala Lumpur, Malaysia

Nur Zakiah Mohd Saat, Ismarulyusda Ishak, Syarif Husin Lubis, See, Huong Wen, Siti Nor Lily Suriyanee Mohd, Norul Sahira Zakaria, et al.

ASEAN Journal of Psychiatry, 2010;11(2):190-197.
MyJurnal

Objective: The objective of this study was to assess the relationship between stress score and body mass index (BMI) of students of Science in Kuala Lumpur. Methods: A cross-sectional study was carried out among 126 students. Data about stress score were collected using a questionnaire, the Student-Life Stress Inventory (SLSI) Data about BMI were calculated from height and weight of the respondents. Results: A total of 117 (92.85%) out of 126 students had responded. The mean difference of stress score among first, second and third year students were 87.6 ± 17.0, 83.4 ± 16.9 and 86.7 ± 15.4 respectively. The mean difference of stress scores between the Bumiputra and non-Bumiputra students were 87.9 ± 16.5 and 83.2 ± 15.9 .The mean of body mass Index(BMI) between first, second and third year students were 21.0 ± 3.5, 20.3 ± 2.7 and 21.8 ± 4.3 respectively. Conclusions: This study showed that the stress level is higher in first year, female and bumiputra student. There was no significant relationship between stress score and BMI.
Activated ADI pathway: the initiator of intermediate vancomycin resistance in Staphylococcus aureus

Tan XE, Neoh HM, Looi ML, Chin SF, Cui L, Hiramatsu K, et al.

Can J Microbiol, 2017 Mar;63(3):260-264.
PMID: 28059579 DOI: 10.1139/cjm-2016-0439

Comparative proteomic profiling between 2 vancomycin-intermediate Staphylococcus aureus (VISA) strains, Mu50Ω-vraSm and Mu50Ω-vraSm-graRm, and vancomycin-susceptible S. aureus (VSSA) strain Mu50Ω revealed upregulated levels of catabolic ornithine carbamoyltransferase (ArcB) of the arginine catabolism pathway in VISA strains. Subsequent analyses showed that the VISA strains have higher levels of cellular ATP and ammonia, which are by-products of arginine catabolism, and displayed thicker cell walls. We postulate that elevated cytoplasmic ammonia and ATP molecules, resulting from activated arginine catabolism upon acquisition of vraS and graR mutations, are important requirements facilitating cell wall biosynthesis, thereby contributing to thickened cell wall and consequently reduced vancomycin susceptibility in VISA strains.
Fulltext Draft Genome Sequences of Four Nosocomial Methicillin-Resistant Staphylococcus aureus (MRSA) Strains (PPUKM-261-2009, PPUKM-332-2009, PPUKM-377-2009, and PPUKM-775-2009) Representative of Dominant MRSA Pulsotypes Circulating in a Malaysian University Teaching Hospital

Neoh HM, Mohamed-Hussein ZA, Tan XE, B Raja Abd Rahman RM, Hussin S, Mohamad Zin N, et al.

Genome Announc, 2013 Jan;1(1).
PMID: 23405328 DOI: 10.1128/genomeA.00103-12

Here, we report the draft genome sequences of four nosocomial methicillin-resistant Staphylococcus aureus strains (PPUKM-261-2009, PPUKM-332-2009, PPUKM-377-2009, and PPUKM-775-2009) isolated from a university teaching hospital in Malaysia. Three of the strains belong to sequence type 239 (ST239), which has been associated with sustained hospital epidemics worldwide.
Antimicrobial resistance profiling and molecular typing of methicillin-resistant Staphylococcus aureus isolated from a Malaysian teaching hospital

Noordin A, Sapri HF, Mohamad Sani NA, Leong SK, Tan XE, Tan TL, et al.

J Med Microbiol, 2016 Dec;65(12):1476-1481.
PMID: 27902380 DOI: 10.1099/jmm.0.000387

The annual prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in Malaysia has been estimated to be 30 % to 40 % of all S. aureus infections. Nevertheless, data on the antimicrobial resistance and genetic diversity of Malaysian MRSAs remain few. In 2009, we collected 318 MRSA strains from various wards of our teaching hospital located in Kuala Lumpur, the capital city of Malaysia, and performed antimicrobial susceptibility testing on these strains. The strains were then molecularly characterized via staphylococcal cassette chromosome (SCC) mec and virulence gene (cna, sea, seb, sec, sed, see, seg, seh, sei, eta, etb, Panton-Valentine leukocidin and toxic shock syndrome toxin-1) typing; a subset of 49 strains isolated from the intensive care unit was also typed using PFGE. Most strains were found to be resistant to ciprofloxacin (92.5 %), erythromycin (93.4 %) and gentamicin (86.8 %). The majority (72.0 %) of strains were found to harbour SCCmec type III-SCCmercury with the presence of ccrC, and carried the sea+cna gene combination (49.3 %), with cna as the most prevalent virulence gene (94.0 %) detected. We identified four PFGE clusters, with pulsotype C (n=19) as the dominant example in the intensive care unit, where this pulsotype was found to be associated with carriage of SCCmec type III and the sea gene (P=0.05 and P=0.02, respectively). In summary, the dominant MRSA circulating in our hospital in 2009 was a clone that was ciprofloxacin, erythromycin and gentamicin resistant, carried SCCmec type III-SCCmercury with ccrC and also harboured the sea+cna virulence genes. This clone also appears to be the dominant MRSA circulating in major hospitals in Kuala Lumpur.