Overview of the distribution of Burkholderia pseudomallei sequence types and the Emergence of sequence type 1342 in Malaysia.

Burkholderia pseudomallei, a Gram-negative bacterial pathogen that causes melioidosis, is of public health importance in endemic areas including Malaysia. An investigation of the molecular epidemiology links of B. pseudomallei would contribute to better understanding of the clonal relationships, transmission dynamics and evolutionary change. Multilocus sequence typing (MLST) of 45 clinical B. pseudomallei isolates collected from sporadic melioidosis cases in Malaysia was performed. In addition, a total of 449 B. pseudomallei Malaysian strains submitted to the MLST database from 1964 until 2019 were included in the temporal analysis to determine the endemic sequence types (STs), emergence and re-emergence of ST(s). In addition, strain-specific distribution was evaluated using BURST tool. Genotyping of 45 clinical strains was resolved into 12 STs, and the majority were affiliated with ST46 (n = 11) and ST1342 (n = 7). Concomitantly, ST46 was the most prevalent ST in Malaysia, which was first reported in 1964. All the Malaysian B. pseudomallei strains were resolved into 76 different STs with 36 of them uniquely present only in Malaysia. ST1342 was most closely related to ST1034, in which both STs were unique to Malaysia and first isolated from soil samples in Pahang, a state in Malaysia. The present study revealed a high diversity of B. pseudomallei in Malaysia. Localized evolution giving rise to the emergence of new STs was observed, suggesting that host and environmental factors play a crucial role in the evolutionary changes in B. pseudomallei.

Methicillin-resistant Staphylococcus aureus bacteraemia, 2003-2015: Comparative evaluation of changing trends in molecular epidemiology and clinical outcomes of infections.

Methicillin-resistant Staphylococcus aureus (MRSA) is a prominent pathogen causing invasive infections such as bacteraemia. The continued excessive use of antibiotics to treat MRSA infections has resulted in the evolution of antimicrobial resistant of S. aureus. This study aims to perform a comparative evaluation of changing trends in molecular epidemiology of MRSA and clinical characteristics of patients. This study shows that ST22-MRSA-IV has gradually replaced ST239-MRSA-III as the predominant MRSA clone in the tertiary teaching hospital studied. Independent predictors of mortality among patients included devices in situ at the time of infection, pre-exposure to macrolides, catheter-related bloodstream infection and mono-microbial infection. Hence, our study affirmed community-associated MRSA, which was previously identified from individuals without any exposure to healthcare settings, has now emerged in healthcare settings, causing healthcare-associated MRSA infections.

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia: Correlations between clinical, phenotypic, genotypic characteristics and mortality in a tertiary teaching hospital in Malaysia.

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia is a serious infection that can result in significant morbidity and mortality. A retrospective cohort study was conducted to determine the predictors of mortality in patient with MRSA bacteremia correlating with clinical, phenotypic and genotypic characteristics of the relevant strains. Most of the bacteremia cases were healthcare-associated (P < 0.0001). Older age (P < 0.0001) and comorbidities (diabetes mellitus, hypertension and chronic kidney disease) were identified as the risk factors for MRSA bacteremia. All the strains were sensitive to vancomycin. Most MRSA strains causing bacteremia belonged to SCCmec type III-ST239 and exhibited pulsotype H. According to the multivariate analysis, age ≥ 60 years old (P = 0.022), female gender (P = 0.0003), pneumonia (P = 0.011) as source of infection as well as high APACHE II, Charlson comorbidity Index and Pitt's bacteremia scores were significantly associated with patient's mortality. There were emergence of MRSA clones such as SCCmec type I-ST152, SCCmec type V-ST45 and SCCmec type V-ST951 that was discovered for the first time in Malaysia. To our knowledge, this is the first study correlating the clinical, phenotypic and genotypic characteristics of patients with MRSA bacteremia as well as determining the risk factors for mortality in Malaysian hospital.

Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infection and the molecular characteristics of MRSA bacteraemia over a two-year period in a tertiary teaching hospital in Malaysia.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is an established pathogen that causes hospital- and community-acquired infections worldwide. The prevalence rate of MRSA infections were reported to be the highest in Asia. As there is limited epidemiological study being done in Malaysia, this study aimed to determine the prevalence of MRSA infection and the molecular characteristics of MRSA bacteraemia. METHODS: Two hundred and nine MRSA strains from year 2011 to 2012 were collected from a tertiary teaching hospital in Malaysia. The strains were characterized by antimicrobial susceptibility testing, staphylococcal cassette chromosome mec (SCCmec) typing, detection of Panton-Valentine leukocidin (PVL) gene, multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). Patient's demographic and clinical data were collected and correlated with molecular data by statistical analysis. RESULTS: Male gender and patient >50 years of age (p < 0.0001) were significantly associated with the increased risk of MRSA acquisition. Fifty-nine percent of MRSA strains were HA-MRSA that carried SCCmec type II, III, IV and V while 31% were CA-MRSA strains with SCCmec III, IV and V. The prevalence of PVL gene among 2011 MRSA strains was 5.3% and no PVL gene was detected in 2012 MRSA strains. All of the strains were sensitive to vancomycin. However, vancomycin MIC creep phenomenon was demonstrated by the increased number of MRSA strains with MIC ≥1.5 µg/mL (p = 0.008) between 2011 and 2012. Skin disease (p = 0.034) and SCCmec type III (p = 0.0001) were found to be significantly associated with high vancomycin MIC. Forty-four percent of MRSA strains from blood, were further subtyped by MLST and PFGE. Most of the bacteraemia cases were primary bacteraemia and the common comorbidities were diabetes, hypertension and chronic kidney disease. The predominant pulsotype was pulsotype C exhibited by SCCmec III-ST239. This is a first study in Malaysia that reported the occurrence of MRSA clones such as SCCmec V-ST5, untypeable-ST508, SCCmec IV-ST1 and SCCmec IV-ST1137. CONCLUSIONS: SCCmec type III remained predominant among the MRSA strains in this hospital. The occurrence of SCCmec IV and V among hospital strains and the presence of SCCmec III in CA-MRSA strains are increasing. MRSA strains causing bacteraemia over the two-year study period were found to be genetically diverse.