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Fulltext Culture-positive thoracic empyema in adults

Liam CK, Pendek R, Navaratnam P, Hassan H, Puthucheary SD, Abdul Majid A, et al.

Med J Malaysia, 1990 Jun;45(2):169-76.
PMID: 2152022

Twenty-nine adult patients with culture-positive thoracic empyema were seen at the University Hospital Kuala Lumpur from 1984 to 1988. Cough, fever, chest pain, dyspnoea and weight loss were the common presenting symptoms. The empyema in 16 patients was associated with primary bronchopulmonary infections, nine occurred following thoracentesis of culture-sterile pleural effusions, two occurred as post-thoracic surgery complications, one following a subdiaphragmatic abscess and one as a result of a stab wound. The most common culture isolates were Streptococcus milleri, Pseudomonas aeruginosa and Klebsiella pneumoniae. Closed tube thoracostomy, the most common form of drainage procedure employed, was able to effect a cure or control of the empyema in 11 out of 19 patients in whom it was used.
DNA fingerprinting of human isolates of Salmonella enterica serotype Paratyphi B in Malaysia

Goh YL, Yasin R, Puthucheary SD, Koh YT, Lim VK, Taib Z, et al.

J Appl Microbiol, 2003;95(5):1134-42.
PMID: 14633043

DNA fingerprinting of Salmonella enterica serotype Paratyphi B isolated in Malaysia during 1982-83, 1992 and 1996-2002 was carried out by pulsed-field gel electrophoresis (PFGE), antimicrobial susceptibility tests and D-tartrate utilization tests to assess the extent of genetic diversity of these isolates in Malaysia.
Molecular analysis of ciprofloxacin resistance among non-typhoidal Salmonella with reduced susceptibility to ciprofloxacin isolated from patients at a tertiary care hospital in Kuala Lumpur, Malaysia

Karunakaran R, Tay ST, Rahim FF, Lim BB, Puthucheary SD

Jpn J Infect Dis, 2014;67(3):157-62.
PMID: 24858603

We investigated the prevalence of non-typhoidal Salmonella (NTS) with "reduced susceptibility to ciprofloxacin" (RS-Cip) (minimum inhibitory concentration [MIC], 0.12-1.0 μg/mL) as well as their resistance genes in 75 NTS isolates (53 from stool, 21 from blood, and 1 from urine) from patients at a tertiary care Malaysian hospital between January and December 2009. RS-Cip was detected in 24/75 (32.0%) isolates. Using the ciprofloxacin MIC interpretive criteria for Salmonella in the Clinical and Laboratory Standards Institute 2013 guidelines, 51/75 (68.0%) isolates were found to be sensitive, 22/75 (29.3%) were intermediate, and 2/75 (2.7%) were resistant to ciprofloxacin. The 24 isolates that were intermediate or resistant to ciprofloxacin were the same isolates categorized as having RS-Cip. Among the 23 tested isolates with RS-Cip, the qnrS gene was detected in 17/23 (73.9%) and single gyrA mutations were detected in 6/23 (26.1%) (Asp87Tyr [n = 3], Asp87Asn [n = 2], and Ser83Phe [n = 1]). A parC (Thr57Ser) mutation was detected in 13/23 (56.5%) isolates, coexisting with either a qnrS gene or a gyrA mutation. The high incidence of the qnrS gene among isolates with RS-Cip needs to be monitored because qnr genes can spread via plasmids and aid in the emergence of increased resistance levels.
Effect of soy protein on the small bowel mucosa of young infants recovering from acute gastroenteritis

Iyngkaran N, Yadav M, Looi LM, Boey CG, Lam KL, Balabaskaran S, et al.

J Pediatr Gastroenterol Nutr, 1988 Jan-Feb;7(1):68-75.
PMID: 3335989

The effect of soy protein on the small bowel mucosa of 18 infants with acute gastroenteritis was studied. The infants were maintained on a protein hydrolysate formula for 6-8 weeks, following which they were readmitted for soy protein challenge studies. Jejunal biopsy was performed before and 24 h after challenge. On the basis of the clinical and histological reaction to soy protein challenge, three groups were identified. Group 1 consisted of three infants who had clinical and histological reaction. There was associated depletion of mucosal enzymes, lactase, sucrase, malatase, alkaline phosphatase, and blood xylose levels. Group 2 consisted of seven infants who had histological reaction but no clinical symptoms. Two of these seven infants, however, developed clinical reaction when rechallenged with soy protein 2 and 90 days later. Following challenge, mucosal enzymes and blood xylose levels were depressed in five of the seven infants tested. Group 3 consisted of eight infants who did not have either a clinical or a histological reaction. The mucosal enzymes and blood xylose levels were not depressed in four infants tested. The present study shows that the small bowel mucosa of some young infants recovering from acute gastroenteritis remains sensitive to soy protein for a variable period of time. The feeding of soy protein to these infants may result in the persistence of mucosal damage and perpetuation of diarrhea.(ABSTRACT TRUNCATED AT 250 WORDS)
Proteomic profiling of clinical and environmental strains of Pseudomonas aeruginosa

Liew SM, Puthucheary SD, Rajasekaram G, Chai HC, Chua KH

Mol Biol Rep, 2021 Mar;48(3):2325-2333.
PMID: 33728559 DOI: 10.1007/s11033-021-06262-8

Pseudomonas aeruginosa is a ubiquitous bacterium, which is able to change its physiological characteristics in response to different habitats. Environmental strains are presumably less pathogenic than clinical strains and whether or not the clinical strains originate from the environment or through inter-host transmission remains poorly understood. To minimize the risk of infection, a better understanding of proteomic profiling of P. aeruginosa is necessary for elucidating the correlation between environmental and clinical strains. Based on antimicrobial susceptibility and patterns of virulence, we selected 12 clinical and environmental strains: (i) environmental, (ii) multidrug resistant (MDR) clinical and (iii) susceptible clinical strains. Whole-cell protein was extracted from each strain and subjected to two-dimensional differential gel electrophoresis (2-D DIGE) and liquid chromatography tandem mass spectrometry quadrupole time-of-flight (LC-MS QTOF). All 12 strains were clustered into 3 distinct groups based on their variance in protein expression. A total of 526 matched spots were detected and four differentially expressed protein spots (p < 0.05) were identified and all differential spots were downregulated in MDR strain J3. Upregulation of chitin binding and BON domain proteins was present in the environmental and some MDR strains, whereas the clinical strains exhibited distinct proteomic profiles with increased expression of serine protein kinase and arginine/ornithine transport ATP-binding proteins. Significant difference in expression was observed between susceptible clinical and MDR strains, as well as susceptible clinical and environmental strains. Transition from an environmental saprophyte to a clinical strain could alter its physiological characteristics to further increase its adaptation.
Fulltext Genetic relatedness and novel sequence types of clinical Aeromonas dhakensis from Malaysia

Lau TTV, Tan JMA, Puthucheary SD, Puah SM, Chua KH

Braz J Microbiol, 2020 Sep;51(3):909-918.
PMID: 32067209 DOI: 10.1007/s42770-020-00239-8

Aeromonas dhakensis is an emergent human pathogen with medical importance. This study was aimed to determine the sequence types (STs), genetic diversity, and phylogenetic relationships of different clinical sources of 47 A. dhakensis from Malaysia using multilocus sequence typing (MLST), goeBURST, and phylogenetic analyses. The analysis of a concatenated six-gene tree with a nucleotide length of 2994 bp based on six housekeeping genes (gyrB, groL, gltA, metG, ppsA, and recA) and independent analyses of single gene fragments was performed. MLST was able to group 47 A. dhakensis from our collection into 36 STs in which 34 STs are novel STs. The most abundant ST521 consisted of five strains from peritoneal fluid and two strains from stools. Comparison of 62 global A. dhakensis was carried out via goeBURST; 94.4% (34/36) of the identified STs are novel and unique in Malaysia. Two STs (111 and 541) were grouped into clonal complexes among our strains and 32 STs occurred as singletons. Single-gene phylogenetic trees showed varying topologies; groL and rpoD grouped all A. dhakensis into a tight-cluster with bootstrap values of 100% and 99%, respectively. A poor phylogenetic resolution encountered in single-gene analyses was buffered by the multilocus phylogenetic tree that offered high discriminatory power (bootstrap value = 100%) in resolving all A. dhakensis from A. hydrophila and delineating the relationship among other taxa. Genetic diversity analysis showed groL as the most conserved gene and ppsA as the most variable gene. This study revealed novel STs and high genetic diversity among clinical A. dhakensis from Malaysia.
Development of a species-specific PCR-RFLP targeting rpoD gene fragment for discrimination of Aeromonas species

Puah SM, Khor WC, Kee BP, Tan JAMA, Puthucheary SD, Chua KH

J Med Microbiol, 2018 Sep;67(9):1271-1278.
PMID: 30024365 DOI: 10.1099/jmm.0.000796

PURPOSE: The taxonomy of Aeromonas keeps expanding and their identification remains problematic due to their phenotypic and genotypic heterogeneity. In this study, we aimed to develop a rapid and reliable polymerase chain reaction-restriction fragment length polymorphism assay targeting the rpoD gene to enable the differentiation of aeromonads into 27 distinct species using microfluidic capillary electrophoresis.
METHODOLOGY: A pair of degenerate primers (Aero F: 5'-YGARATCGAYATCGCCAARCGB-3' and Aero R: 5'-GRCCDATGCTCATRCGRCGGTT-3') was designed that amplified the rpoD gene of 27 Aeromonas species. Subsequently, in silico analysis enabled the differentiation of 25 species using the single restriction endonuclease AluI, while 2 species, A. sanarelli and A. taiwanensis, required an additional restriction endonuclease, HpyCH4IV. Twelve type strains (A. hydrophila ATCC7966T, A. caviae ATCC15468T, A. veronii ATCC9071T, A. media DSM4881T, A. allosaccharophila DSM11576T, A. dhakensis DSM17689T, A. enteropelogens DSM7312T, A. jandaei DSM7311T, A. rivuli DSM22539T, A. salmonicida ATCC33658T, A. taiwanensis DSM24096T and A. sanarelli DSM24094T) were randomly selected from the 27 Aeromonas species for experimental validation.Results/key findings. The twelve type strains demonstrated distinctive RFLP patterns and supported the in silico digestion. Subsequently, 60 clinical and environmental strains from our collection, comprising nine Aeromonas species, were used for screening examinations, and the results were in agreement.
CONCLUSION: This method provides an alternative method for laboratory identification, surveillance and epidemiological investigations of clinical and environmental specimens.
Simple and rapid detection of Salmonella strains by direct PCR amplification of the hilA gene

Pathmanathan SG, Cardona-Castro N, Sánchez-Jiménez MM, Correa-Ochoa MM, Puthucheary SD, Thong KL

J Med Microbiol, 2003 Sep;52(Pt 9):773-6.
PMID: 12909653

The suitability of a PCR procedure using a pair of primers targeting the hilA gene was evaluated as a means of detecting Salmonella species. A total of 33 Salmonella strains from 27 serovars and 15 non-Salmonella strains from eight different genera were included. PCR with all the Salmonella strains produced a 784 bp DNA fragment that was absent from all the non-Salmonella strains tested. The detection limit of the PCR was 100 pg with genomic DNA and 3 x 10(4) c.f.u. ml(-1) with serial dilutions of bacterial culture. An enrichment-PCR method was further developed to test the sensitivity of the hilA primers for the detection of Salmonella in faecal samples spiked with different concentrations of Salmonella choleraesuis subsp. choleraesuis serovar Typhimurium. The method described allowed the detection of Salmonella Typhimurium in faecal samples at a concentration of 3 x 10(2) c.f.u. ml(-1). In conclusion, the hilA primers are specific for Salmonella species and the PCR method presented may be suitable for the detection of Salmonella in faeces.
Analysis of fliC variation among clinical isolates of Burkholderia cepacia

Winstanley C, Hales BA, Morgan JAW, Gallagher MJ, Puthucheary SD, CISSé MF, et al.

J Med Microbiol, 1999 Jul;48(7):657-662.
PMID: 10403416 DOI: 10.1099/00222615-48-7-657

PCR and restriction fragment length polymorphism (RFLP) typing of flagellin genes (fliC) from 57 clinical isolates of Burkholderia cepacia indicated that only type 11 flagellins were present. Twenty-two isolates previously identified as the epidemic UK cystic fibrosis strain were indistinguishable by this method, as were 11 isolates from a pseudo-outbreak in Senegal. Other clinical isolates, including 19 from disparate sources in Malaysia, were separated into nine fliC RFLP groups, exhibiting a large degree of divergence. When isolates were indistinguishable by fliC genotyping, their similarity was confirmed by whole genome macro-restriction analysis with pulsed-field gel electrophoresis following XbaI digestion. The variation in fliC sequences of B. cepacia was far greater than that with B. pseudomallei, supporting the view that 'B. cepacia', as currently defined, may comprise several different genomic species.
Fulltext Rapid identification of melioidosis agent by an insulated isothermal PCR on a field-deployable device

Chua KH, Tan EW, Chai HC, Puthucheary SD, Lee PC, Puah SM

PeerJ, 2020;8:e9238.
PMID: 32518734 DOI: 10.7717/peerj.9238

Background: Burkholderia pseudomallei causes melioidosis, a serious illness that can be fatal if untreated or misdiagnosed. Culture from clinical specimens remains the gold standard but has low diagnostic sensitivity.
Method: In this study, we developed a rapid, sensitive and specific insulated isothermal Polymerase Chain Reaction (iiPCR) targeting bimA gene (Burkholderia Intracellular Motility A; BPSS1492) for the identification of B. pseudomallei. A pair of novel primers: BimA(F) and BimA(R) together with a probe were designed and 121 clinical B. pseudomallei strains obtained from numerous clinical sources and 10 ATCC non-targeted strains were tested with iiPCR and qPCR in parallel.
Results: All 121 B. pseudomallei isolates were positive for qPCR while 118 isolates were positive for iiPCR, demonstrating satisfactory agreement (97.71%; 95% CI [93.45-99.53%]; k = 0.87). Sensitivity of the bimA iiPCR/POCKIT assay was 97.52% with the lower detection limit of 14 ng/µL of B. pseudomallei DNA. The developed iiPCR assay did not cross-react with 10 types of non-targeted strains, indicating good specificity.
Conclusion: This bimA iiPCR/POCKIT assay will undoubtedly complement other methodologies used in the clinical laboratory for the rapid identification of this pathogen.
Characterization of the relationship between polar and lateral flagellar genes in clinical Aeromonas dhakensis: phenotypic, genetic and biochemical analyses

Lau TV, Puah SM, Tan JMA, Puthucheary SD, Chua KH

Braz J Microbiol, 2021 Jun;52(2):517-529.
PMID: 33768508 DOI: 10.1007/s42770-021-00457-8

Flagellar-mediated motility is a crucial virulence factor in many bacterial species. A dual flagellar system has been described in aeromonads; however, there is no flagella-related study in the emergent human pathogen Aeromonas dhakensis. Using 46 clinical A. dhakensis, phenotypic motility, genotypic characteristics (flagellar genes and sequence types), biochemical properties and their relationship were investigated in this study. All 46 strains showed swimming motility at 30 °C in 0.3% Bacto agar and carried the most prevalent 6 polar flagellar genes cheA, flgE, flgG, flgH, flgL, and flgN. On the contrary, only 18 strains (39%) demonstrated swarming motility on 0.5% Eiken agar at 30 °C and they harbored 11 lateral flagellar genes lafB, lafK, lafS, lafT, lafU, flgCL, flgGL, flgNL, fliEL, fliFL, and fliGL. No association was found between biochemical properties and motility phenotypes. Interestingly, a significant association between swarming and strains isolated from pus was observed (p = 0.0171). Three strains 187, 277, and 289 isolated from pus belonged to novel sequence types (ST522 and ST524) exhibited fast swimming and swarming profiles, and they harbored > 90% of the flagellar genes tested. Our findings provide a fundamental understanding of flagellar-mediated motility in A. dhakensis.
Molecular identification and biofilm-forming ability of Elizabethkingia species

Puah SM, Fong SP, Kee BP, Puthucheary SD, Chua KH

Microb Pathog, 2022 Jan;162:105345.
PMID: 34896547 DOI: 10.1016/j.micpath.2021.105345

Recently, Elizabethkingia species have gained attention as a cause of life-threatening infections. The identification via phenotypic methods of three important species- Elizabethkingia meningoseptica, E. anophelis and E. miricola is difficult. Our objectives were to re-assess 30 archived Flavobacterium meningosepticum isolates using 16S rRNA gene sequencing, ERIC-PCR, and biofilm formation assay. Twenty-four isolates were re-identified as E. anophelis and 6 as E. miricola. All of them had the ability to form biofilm as shown in microtiter plate assay based on crystal violet staining. Overall, E. anophelis had a higher specific biofilm formation index compared to E. miricola. A total of 42% (10 out of 24) of E. anophelis were classified as strong, 29% (7 out of 24) as moderate and 29% (7 out of 24) as weak biofilm producers. E. miricola, 17% (1 out of 6) isolates were strong biofilm producers, 50% (3 out of 6) moderate and 33% (2 out of 6) were weak producers. E. anophelis from tracheal secretions were significantly associated with (p = 0.0361) strong biofilm formation. In summary, this study showed that the isolates originally identified as F. meningosepticum were re-classified using the 16S rRNA gene as one of two Elizabethkingia species. The ability of E. anophelis to form strong biofilm in endotracheal tubes indicates their probable role in the pathogenesis of Elizabethkingia infections.
Comparison of Clinical Isolates of Aeromonas from Singapore and Malaysia with Regard to Molecular Identification, Virulence, and Antimicrobial Profiles

Khor WC, Puah SM, Koh TH, Tan JAMA, Puthucheary SD, Chua KH

Microb Drug Resist, 2018 May;24(4):469-478.
PMID: 29461928 DOI: 10.1089/mdr.2017.0083

OBJECTIVE: The objective of this study was to examine the species distribution, genetic relatedness, virulence gene profiles, antimicrobial sensitivities, and resistance gene distribution of clinical Aeromonas strains from Singapore and Malaysia.
METHODS: A total of 210 Aeromonas clinical isolates were investigated: 116 from Singapore General Hospital and 94 archived clinical isolates from University of Malaya Medical Center, Malaysia. The isolates were genetically identified based on the gcat gene screening and the partial sequences of the rpoD housekeeping gene. Genetic relatedness, distribution of 15 virulence genes and 4 beta-lactamase resistance genes, and susceptibility patterns to 11 antimicrobial agents were compared.
RESULTS: Of the 210 Aeromonas isolates, A. dhakensis-94 (45%) was the dominant species in Singapore and Malaysia. Species composition was similar and enterobacterial repetitive intergenic consensus-PCR did not show genetic relatedness between strains from the two countries. Of the 15 virulence genes, A. dhakensis and A. hydrophila harbored the most compared with other species. Different combinations of 9 virulence genes (exu, fla, lip, eno, alt, dam, hlyA, aexU, and ascV) were present in A. dhakensis, A. hydrophila, and A. veronii from both the countries. Distribution of virulence genes was species and anatomic site related. Majority (>80%) of the strains were susceptible to all antimicrobial agents tested, except amoxicillin and cephalothin. A. dhakensis strains from Malaysia significantly harbored the cphA gene compared with A. dhakensis from Singapore. Multidrug resistance was mostly detected in strains from peritoneal fluids of dialysis patients.
CONCLUSION: This study revealed A. dhakensis as the dominant species isolated in both geographic regions, and that it carried a high number of virulence genes. It also highlights the geographic-related differences of virulence gene distribution and antimicrobial resistance profiles of clinical Aeromonas strains from Singapore and Malaysia.
Flagellar motility mediates biofilm formation in Aeromonas dhakensis

Lau TV, Puah SM, Tan JMA, Merino S, Puthucheary SD, Chua KH

Microb Pathog, 2023 Apr;177:106059.
PMID: 36878334 DOI: 10.1016/j.micpath.2023.106059

Aeromonas dhakensis possesses dual flagellar systems for motility under different environments. Flagella-mediated motility is necessary for biofilm formation through an initial attachment of bacteria to the surface, but this has not been elucidated in A. dhakensis. This study investigates the role of polar (flaH, maf1) and lateral (lafB, lafK and lafS) flagellar genes in the biofilm formation of a clinical A. dhakensis strain WT187 isolated from burn wound infection. Five deletion mutants and corresponding complemented strains were constructed using pDM4 and pBAD33 vectors, respectively, and analyzed for motility and biofilm formation using crystal violet staining and real-time impedance-based assays. All mutants were significantly reduced in swimming (p
Genetic diversity of clinical and environmental strains of Salmonella enterica serotype Weltevreden isolated in Malaysia

Thong KL, Goh YL, Radu S, Noorzaleha S, Yasin R, Koh YT, et al.

J Clin Microbiol, 2002 Jul;40(7):2498-503.
PMID: 12089269

The incidence of food-borne salmonellosis due to Salmonella enterica serotype Weltevreden is reported to be on the increase in Malaysia. The pulsed-field gel electrophoresis (PFGE) subtyping method was used to assess the extent of genetic diversity and clonality of Salmonella serotype Weltevreden strains from humans and the environment. PFGE of XbaI-digested chromosomal DNA from 95 strains of Salmonella serotype Weltevreden gave 39 distinct profiles with a wide range of Dice coefficients (0.27 to 1.00), indicating that PFGE is very discriminative and that multiple clones of Salmonella serotype Weltevreden exist among clinical and environmental isolates. Strains of one dominant pulsotype (pulsotype X1/X2) appeared to be endemic in this region, as they were consistently recovered from humans with salmonellosis between 1996 and 2001 and from raw vegetables. In addition, the sharing of similar PFGE profiles among isolates from humans, vegetables, and beef provides indirect evidence of the possible transmission of salmonellosis from contaminated raw vegetables and meat to humans. Furthermore, the recurrence of PFGE profile X21 among isolates found in samples of vegetables from one wet market indicated the persistence of this clone. The environment in the wet markets may represent a major source of cross-contamination of vegetables with Salmonella serotype Weltevreden. Antibiotic sensitivity tests showed that the clinical isolates of Salmonella serotype Weltevreden remained drug sensitive but that the vegetable isolates were resistant to at least two antibiotics. To the best of our knowledge, this is the first study to compare clinical and environmental isolates of Salmonella serotype Weltevreden in Malaysia.
Fulltext Draft genome sequence of an Aeromonas sp. strain 159 clinical isolate that shows quorum-sensing activity

Chan XY, Chua KH, Puthucheary SD, Yin WF, Chan KG

J Bacteriol, 2012 Nov;194(22):6350.
PMID: 23105081 DOI: 10.1128/JB.01642-12

Aeromonas is a pathogenic organism that is often found to infect humans. Here we report the draft genome of a clinical isolate in Malaysia, Aeromonas sp. strain 159, which shows N-acylhomoserine lactone production. In the draft genome of strain 159, luxI and luxR homologue genes were found to be located at contig 47, and these genes are believed to be important for the quorum-sensing system present in this pathogen.
Fulltext Multiple-antigen ELISA for melioidosis--a novel approach to the improved serodiagnosis of melioidosis

Hara Y, Chin CY, Mohamed R, Puthucheary SD, Nathan S

BMC Infect Dis, 2013;13:165.
PMID: 23556548 DOI: 10.1186/1471-2334-13-165

Burkholderia pseudomallei, the causative agent of melioidosis, is endemic to Southeast Asia and northern Australia. Clinical manifestations of disease are diverse, ranging from chronic infection to acute septicaemia. The current gold standard of diagnosis involves bacterial culture and identification which is time consuming and often too late for early medical intervention. Hence, rapid diagnosis of melioidosis is crucial for the successful management of melioidosis.
Diagnostic use of Burkholderia pseudomallei selective media in a low prevalence setting

Roesnita B, Tay ST, Puthucheary SD, Sam IC

Trans R Soc Trop Med Hyg, 2012 Feb;106(2):131-3.
PMID: 22112687 DOI: 10.1016/j.trstmh.2011.10.007

Routine use of selective media improves diagnosis of Burkholderia pseudomallei, but resources may be limited in endemic developing countries. To maximise yield in the relatively low-prevalence setting of Kuala Lumpur, Malaysia, B. pseudomallei selective agar and broth were compared with routine media for 154 respiratory specimens from patients with community-acquired disease. Selective media detected three additional culture-positive specimens and one additional melioidosis patient, at a consumables cost of US$75. Burkholderia pseudomallei was not isolated from 74 diabetic foot ulcer samples. Following careful local evaluation, focused use of selective media may be cost-effective.
Characterization of drug resistant Salmonella enterica serotype Typhimurium by antibiograms, plasmids, integrons, resistance genes and PFGE

Benacer D, Thong KL, Watanabe H, Puthucheary SD

J Microbiol Biotechnol, 2010 Jun;20(6):1042-52.
PMID: 20622506

Forty-seven Salmonella Typhimurium (33 zoonotic, 14 clinical) strains were tested for antimicrobial resistance using the standard disk diffusion method. Presence of relevant resistance genes and class 1 integrons were investigated by using PCR. Pulsed-field gel electrophoresis (PFGE) and plasmid profiling were carried out to determine the genomic diversity of Salmonella Typhimurium. Approximately 57.4% of S. Typhimurium were multidrug resistant (MDR) and showed high resistance rates to tetracycline (70.2%), sulphonamides (57.4%), streptomycin (53.1%), ampicillin (29.7%), nalidixic acid (27.6%), kanamycin (23.4%), chloramphenicol (21.2%) and trimethoprim (19.1%). Resistance towards cephalosporins was noted for cephalothin (27.6%), cephradine (21.2%), amoxicillin clavulanic acid (17.0%) and cephalexin (17.0%). Resistance genes, blaTEM, strA, aadA, sul1, sul2, tet(A), tet(B) and tet(C) were detected among the drug resistant strains. Thirty-three strains (70.2%) carried class 1 integrons, which were grouped in 9 different profiles. DNA sequencing identified sat, aadA, pse-1 and dfrA genes in variable regions on class 1 integrons. Thirty-five strains (74.4%) were subtyped to 22 different plasmid profiles, each with 1 - 6 plasmids (2.0 to 95 kb). PFGE subtyped the 47 strains into 39 profiles. In conclusion, high rates of multidrug-resistance were found among the Malaysian Salmonella Typhimurium strains. The emergence of multidrug-resistant Salmonella Typhimurium to cephalosporin antibiotics was also observed. The strains were very diverse and no persistent clone was observed. The emergence of MDR Salmonella Typhimurium is a worldwide problem and this report provides information for the better understanding of the prevalence and epidemiology of MDR S. Typhimurium in Malaysia.
Burkholderia thailandensis whole cell antigen cross-reacts with B. pseudomallei antibodies from patients with melioidosis in an immunofluorescent assay

Puthucheary SD, Anuar AS, Tee TS

Southeast Asian J. Trop. Med. Public Health, 2010 Mar;41(2):395-400.
PMID: 20578523

An immunofluorescent assay (IFAT) using whole cell antigen derived from Burkholderia thailandensis used for detection of total antibodies to Burkholderia pseudomallei, was found to compare favorably with a previous published report on a B. pseudomallei IFAT assay. At a 1:20 cut-off titer, the assay had high sensitivity (98.9%) and satisfactory specificity (92.3%), when tested against sera from 94 patients suspected of melioidosis. Sera from 12 patients with culture proven melioidosis gave absolute concordance with the 2 test antigens. No sera from 50 blood donors had a titer of > or =20. Cross-reactivity with patients' sera positive for Chlamydia, Mycoplasma, Legionella and typhoid was not observed, except for 3 sera from typhus patients and one from a patient with leptospirosis. The major advantage of this assay is that the cultivation and preparation of B. thailandensis as antigen can be carried out in any laboratory with basic microbiological set-up. The serodiagnosis of melioidosis can be made safe for medical laboratory personnel, particularly in B. pseudomallei endemic regions.

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