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Fulltext Plasmid-mediated transferable chloramphenicol and tetracycline resistance in Salmonella typhi (Vi phage type 25) isolated in Peninsular Malaysia

Koh CL, Lim ME, Wong YH

Med J Malaysia, 1983 Dec;38(4):320-4.
PMID: 6599991

A clinical isolate of Salmonella typhi (Vi phage type 25), resistant to chloramphenicol, streptomycin and tetracycline, was examined for the presence of R plasmids. Results from conjugation, agarose gel electrophoresis and transformation experiments indicated that it harboured a single large self-transmissible R plasmid which coded for both the chloramphenicol and tetracycline resistance traits.

Matched MeSH terms: Salmonella typhi/genetics*
Plasmid incidence rate and conjugative chloramphenicol and tetracycline resistance plasmids in Malaysian isolates of Salmonella typhi

Phipps M, Pang T, Koh CL, Puthucheary S

Microbiol. Immunol., 1991;35(2):157-61.
PMID: 1886492

Seven (6.1%) of 115 strains of Salmonella typhi isolated from Malaysian patients harbored a single large plasmid of 71 to 166 mD. Two of the seven plasmid-bearing strains were resistant to chloramphenicol (Cm) and tetracycline (Tc) and they transferred Cm and Tc resistance traits to Escherichia coli K12 at frequencies from 1.6 x 10(-7) to 1.9 x 10(-6). Agarose gel electrophoresis provided evidence that the resistance traits were cotransferred on a conjugative plasmid. The significance and importance of these results are discussed.

Matched MeSH terms: Salmonella typhi/genetics*
Report from an international symposium on typhoid fever

Pang T, Calva E, Punjabi N, Rowley D

Asian Pac J Allergy Immunol, 1992 Jun;10(1):73-7.
PMID: 1358084
Matched MeSH terms: Salmonella typhi/genetics
Genetic variation among Malaysian isolates of Salmonella typhi as detected by ribosomal RNA gene restriction patterns

Pang T, Altwegg M, Martinetti G, Koh CL, Puthucheary S

Microbiol. Immunol., 1992;36(5):539-43.
PMID: 1513268

Genetic variation among Malaysian isolates of Salmonella typhi was determined by analysis of ribosomal RNA gene restriction patterns. Of the 20 isolates analyzed, eight different pattern combinations were detected. The amount of variation observed was also dependent upon the restriction endonuclease used; PstI produced more different patterns than did SmaI. The results suggested that disease activity was due to a number of different clones circulating simultaneously rather than a single strain. Further implications of the data are discussed.

Matched MeSH terms: Salmonella typhi/genetics*
Epidemiologic analysis of sporadic Salmonella typhi isolates and those from outbreaks by pulsed-field gel electrophoresis

Thong KL, Cheong YM, Puthucheary S, Koh CL, Pang T

J Clin Microbiol, 1994 May;32(5):1135-41.
PMID: 7914202

Pulsed-field gel electrophoresis (PFGE) was used to compare and analyze 158 isolates of Salmonella typhi from five well-defined outbreaks of typhoid fever in Malaysia and also isolates involved in sporadic cases of typhoid fever occurring during the same period. Digestion of chromosomal DNAs from these S. typhi isolates with the restriction endonucleases XbaI (5'-TCTAGA-3'), SpeI (5'-ACTAGT-3'), and AvrII (5'-CCTAGG-3') and then PFGE produced restriction endonuclease analysis (REA) patterns consisting of 11 to 24 DNA fragments ranging in size from 20 to 630 kbp. Analysis of the REA patterns generated by PFGE after digestion with XbaI and SpeI indicated that the S. typhi isolates obtained from sporadic cases of infection were much more heterogeneous (at least 13 different REA patterns were detected; Dice coefficient, between 0.73 and 1.0) than those obtained during outbreaks of typhoid fever. The clonal nature and the close genetic identities of isolates from outbreaks in Alor Setar, Penang, Kota Kinabalu, Johor Bahru, and Kota Bahru were suggested by the fact that only a limited number of REA patterns, which mostly differed by only a single band, were detected (one to four patterns; Dice coefficient, between 0.82 and 1.0), although a different pattern was associated with each of these outbreaks. Comparison of REA patterns with ribotyping for 18 S. typhi isolates involved in sporadic cases of infection showed a good correlation, in that 72% of the isolates were in the same group. There was no clear correlation of phage types with a specific REA pattern. We conclude that PFGE of s. typhi chromosomal DNA digested with infrequently cutting restriction endonucleases is a useful method for comparing and differentiating S. typhi isolates for epidemiological purposes.

Matched MeSH terms: Salmonella typhi/genetics
Analysis of Salmonella typhi isolates from Southeast Asia by pulsed-field gel electrophoresis

Thong KL, Puthucheary S, Yassin RM, Sudarmono P, Padmidewi M, Soewandojo E, et al.

J Clin Microbiol, 1995 Jul;33(7):1938-41.
PMID: 7665677

Pulsed-field gel electrophoresis (PFGE) revealed that multiple genetic variants of Salmonella typhi are simultaneously present in Southeast Asia and are associated with sporadic cases of typhoid fever and occasional outbreaks. Comparative analysis of PFGE patterns also suggested that considerable genetic diversity exists among S. typhi strains and that some PFGE patterns are shared between isolates obtained from Malaysia, Indonesia, and Thailand, implying movement of these strains within these regions of Southeast Asia, where they are endemic.

Matched MeSH terms: Salmonella typhi/genetics*
Molecular analysis of environmental and human isolates of Salmonella typhi

Thong KL, Cordano AM, Yassin RM, Pang T

Appl Environ Microbiol, 1996 Jan;62(1):271-4.
PMID: 8572705

Molecular characterization of a total of 54 isolates of Salmonella typhi from Santiago, Chile, was performed by pulsed-field gel electrophoresis (PFGE) after digestion of chromosomal DNA with three restriction endonucleases: XbaI (5'-TCTAGA-3'), AvrII (5'-CCTAGG-3'), and SpeI (5'-ACTAGT-3'). Thirteen of the 54 isolates were obtained from environmental sources (sewage and river water), and the rest were isolates from clinical cases of typhoid fever. Considerable genetic diversity was detected among the human isolates obtained in 1994, as evidenced by the presence of 14 to 19 different PFGE patterns among 20 human isolates, with F (coefficient of similarity) values ranging from 0.69 to 1.0 (XbaI), 0.61 to 1.0 (AvrII), and 0.70 to 1.0 (SpeI). A total of eight phage types were detected among these 20 isolates, with 50% possessing the E1 or 46 phage type. There was no correlation between PFGE pattern and phage types. Similar diversity was seen among 21 isolates obtained in 1983, with 17 to 19 PFGE patterns detected and F values of 0.56 to 1.0 (XbaI), 0.55 to 1.0 (AvrII), and 0.67 to 1.0 (SpeI). Comparison of these two groups of human isolates obtained 11 years apart indicated that certain molecular types of S. typhi are shared and are able to persist for considerable periods. A similar degree of genetic diversity was also detected among the environmental isolates of S. typhi, for which 10 to 12 different PFGE patterns were detected among the 13 isolates analyzed, with F values ranging from 0.56 to 1.0 (XbaI), 0.52 to 1.0 (AvrII), and 0.69 to 1.0 (SpeI). Certain molecular types present among the environmental isolates of S. typhi were also found among the human isolates from the same time period, providing evidence for the epidemiological link between environmental reservoirs and human infection.

Matched MeSH terms: Salmonella typhi/genetics*
Molecular analysis of isolates of Salmonella typhi obtained from patients with fatal and nonfatal typhoid fever

Thong KL, Passey M, Clegg A, Combs BG, Yassin RM, Pang T

J Clin Microbiol, 1996 Apr;34(4):1029-33.
PMID: 8815078

Molecular characterization of a total of 52 human isolates of Salmonella typhi from Papua New Guinea was performed by using pulsed-field gel electrophoresis (PFGE) after digestion of chromosomal DNA with three restriction endonucleases, XbaI (5'-TCTAGA-3'), AvrII (5'-CCTAGG-3'), and SpeI (5'-ACTAGT-3'). Of the 52 isolates tested, 11 were obtained from patients with fatal typhoid fever and 41 were obtained from patients with nonfatal disease. The 52 isolates showed limited genetic diversity as evidenced by only three different PFGE patterns detected following digestion with XbaI (patterns X1 to X3; F [coefficient of similarity] = 0.86 to 1.0), four patterns detected following digestion with AvrII (patterns A1 to A4; F =0.78 to 1.0), and two patterns detected following digestion with SpeI (patterns S1 and S2; F = 0.97 to 1.0). Of the 52 isolates, 37 were phage typed, and all belonged to phage type D2. All 11 isolates obtained from patients with fatal typhoid fever were identical (F = 1.0) and possessed the PFGE pattern combination X1S1A1, whereas the 41 isolates from patients with nonfatal typhoid fever had various PFGE pattern combinations, the most common being X2S1A2 (39%), X1S1A1 (24%), and X1S1A2 (15%). Thus, all the isolates from patients with the fatal disease had the X1 and A1 patterns, whereas the majority of the isolates from patients with nonfatal typhoid fever possessed the X2 and A2 patterns. The data suggest that there is an association among strains of S. typhi between genotype, as assessed by PFGE patterns, and the capability to cause fatal illness. Analysis of blood and fecal isolates of S. typhi from the same patient also indicated that some genetic changes occur in vivo during the course of infection.

Matched MeSH terms: Salmonella typhi/genetics*
Genome size variation among recent human isolates of Salmonella typhi

Thong KL, Puthucheary SD, Pang T

Res. Microbiol., 1997 Mar-Apr;148(3):229-35.
PMID: 9765803

We performed genome size estimation of 17 recent human isolates of Salmonella typhi from geographically diverse regions using pulsed-field gel electrophoresis (PFGE) after digestion of chromosomal DNA with restriction endonucleases XbaI (5'-TCTAGA-3'), AvrII (5'-CCTAGG-3') and SpeI (5'-ACTAGT-3'), and summation of the sizes of restriction fragments obtained. All 17 isolates had circular chromosomes, and genome sizes differed by as much as 959 kb, ranging from 3,964 to 4,923 kb (mean genome size = 4,528 kb). The data obtained confirm the usefulness of PFGE in studies of bacterial genome size and are in agreement with recent results indicating considerable genetic diversity and genomic plasticity of S. typhi. The variation in genome sizes noted may be relevant to the observed biological properties of this important human pathogen, including its virulence.

Matched MeSH terms: Salmonella typhi/genetics*
Typhoid fever--important issues still remain

Pang T, Levine MM, Ivanoff B, Wain J, Finlay BB

Trends Microbiol., 1998 Apr;6(4):131-3.
PMID: 9587187
Matched MeSH terms: Salmonella typhi/genetics
Genetic dynamics of Salmonella typhi--diversity in clonality

Pang T

Trends Microbiol., 1998 Sep;6(9):339-42.
PMID: 9778724
Matched MeSH terms: Salmonella typhi/genetics*
Analysis of plasmid and chromosomal DNA of multidrug-resistant Salmonella enterica serovar typhi from Asia

Mirza S, Kariuki S, Mamun KZ, Beeching NJ, Hart CA

J Clin Microbiol, 2000 Apr;38(4):1449-52.
PMID: 10747124

Molecular analysis of chromosomal DNA from 193 multidrug-resistant (MDR) Salmonella enterica serovar Typhi isolates from 1990 to 1995 from Pakistan, Kuwait, Malaysia, Bangladesh, and India produced a total of five major different pulsed-field gel electrophoresis (PFGE) patterns. Even within a particular country MDR S. enterica serovar Typhi DNA was found to be in different PFGE groups. Similar self-transferable 98-MDa plasmids belonging to either incompatibility group incHI1 or incHI1/FIIA were implicated in the MDR phenotype in S. enterica serovar Typhi isolates from all the locations except Quetta, Pakistan, where the majority were of incFIA. A total of five different PFGE genotypes with six different plasmids, based on incompatibility and restriction endonuclease analysis groups, were found among these MDR S. enterica serovar Typhi isolates.

Matched MeSH terms: Salmonella typhi/genetics
Genotypic characterization of Salmonella typhi by amplified fragment length polymorphism fingerprinting provides increased discrimination as compared to pulsed-field gel electrophoresis and ribotyping

Nair S, Schreiber E, Thong KL, Pang T, Altwegg M

J Microbiol Methods, 2000 Jun;41(1):35-43.
PMID: 10856775

Amplified fragment length polymorphism (AFLP) is a recently developed, PCR-based high resolution fingerprinting method that is able to generate complex banding patterns which can be used to delineate intraspecific genetic relationships among bacteria. In the present study, AFLP was evaluated for its usefulness in the molecular typing of Salmonella typhi in comparison to ribotyping and pulsed-field gel electrophoresis (PFGE). Six S. typhi isolates from diverse geographic areas (Malaysia, Indonesia, India, Chile, Papua New Guinea and Switzerland) gave unique, heterogeneous profiles when typed by AFLP, a result which was consistent with ribotyping and PFGE analysis. In a further study of selected S. typhi isolates from Papua New Guinea which caused fatal and non-fatal disease previously shown to be clonally related by PFGE, AFLP discriminated between these isolates but did not indicate a linkage between genotype with virulence. We conclude that AFLP (discriminatory index=0.88) has a higher discriminatory power for strain differentiation among S. typhi than ribotyping (DI=0.63) and PFGE (DI=0.74).

Matched MeSH terms: Salmonella typhi/genetics
Multidrug-resistant strains of Salmonella enterica serotype typhi are genetically homogenous and coexist with antibiotic-sensitive strains as distinct, independent clones

Thong KL, Bhutta ZA, Pang T

Int J Infect Dis, 2000;4(4):194-7.
PMID: 11231181

OBJECTIVE: The goal of this study was to report the molecular analysis of antibiotic-sensitive and multidrug-resistant (MDR) strains of Salmonella typhi, using pulsed-field gel electrophoresis (PFGE), with a particular emphasis on the coexistence of these strains in a typhoid-endemic region of Karachi, Pakistan.
METHODS: One hundred isolates of S. typhi in humans (50 MDR and 50 antibiotic-sensitive isolates) from sporadic cases of typhoid fever were analyzed by Vi-phage typing, antibiograms and PFGE.
RESULTS: The MDR S. typhi strains were resistant to ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole. Analysis by PFGE showed that 50 MDR isolates of S. typhi had a single, homogenous PFGE profile, which was distinctly different from that of 50 antibiotic-sensitive isolates obtained in the same time frame from the same area. This latter group of isolates showed much greater diversity of PFGE profiles, as has been observed in other endemic regions.
CONCLUSIONS: Multidrug-resistant and antibiotic-susceptible strains of S. typhi can coexist in endemic areas as epidemiologically independent pathogens and are not in competition for continued persistence and transmission.

Matched MeSH terms: Salmonella typhi/genetics
Increasing genetic diversity of Salmonella enterica serovar typhi isolates from papua new guinea over the period from 1992 to 1999

Thong KL, Goh YL, Yasin RM, Lau MG, Passey M, Winston G, et al.

J Clin Microbiol, 2002 Nov;40(11):4156-60.
PMID: 12409390

Pulsed-field gel electrophoresis (PFGE) of XbaI-digested chromosomal DNA was performed on 133 strains of Salmonella enterica serovar Typhi obtained from Papua New Guinea, with the objective of assessing the temporal variation of these strains. Fifty-two strains that were isolated in 1992 and 1994 were of one phage type, D2, and only two predominant PFGE profiles, X1 and X2, were present. Another 81 strains isolated between 1997 and 1999 have shown divergence, with four new phage types, UVS I (n = 63), UVS (n = 5), VNS (n = 4), and D1 (n = 9), and more genetic variability as evidenced by the multiple and new PFGE XbaI profiles (21 profiles; Dice coefficient, F = 0.71 to 0.97). The two profiles X1 and X2 have remained the stable, dominant subtypes since 1992. Cluster analysis based on the unweighted pair group method using arithmetic averages algorithm identifies two main clusters (at 87% similarity), indicating that the divergence of the PFGE subtypes was probably derived from some genomic mutations of the X1 and X2 subtypes. The majority of isolates were from patients with mild and moderate typhoid fever and had various XbaI profiles. A single isolate from a patient with fatal typhoid fever had a unique X11 profile, while four of six isolates from patients with severe typhoid fever had the X1 pattern. In addition, 12 paired serovar Typhi isolates recovered from the blood and fecal swabs of individual patients exhibited similar PFGE patterns, while in another 11 individuals paired isolates exhibited different PFGE patterns. Three pairs of isolates recovered from three individuals had different phage types and PFGE patterns, indicating infection with multiple strains. The study reiterates the usefulness of PFGE in assessing the genetic diversity of S. enterica serovar Typhi for both long-term epidemiology and in vivo stability and instability within an individual patient.

Matched MeSH terms: Salmonella typhi/genetics
Molecular typing of Salmonella enterica serovar typhi isolates from various countries in Asia by a multiplex PCR assay on variable-number tandem repeats

Liu Y, Lee MA, Ooi EE, Mavis Y, Tan AL, Quek HH

J Clin Microbiol, 2003 Sep;41(9):4388-94.
PMID: 12958274

A multiplex PCR method incorporating primers flanking three variable-number tandem repeat (VNTR) loci (arbitrarily labeled TR1, TR2, and TR3) in the CT18 strain of Salmonella enterica serovar Typhi has been developed for molecular typing of S. enterica serovar Typhi clinical isolates from several Asian countries, including Singapore, Indonesia, India, Bangladesh, Malaysia, and Nepal. We have demonstrated that the multiplex PCR could be performed on crude cell lysates and that the VNTR banding profiles produced could be easily analyzed by visual inspection after conventional agarose gel electrophoresis. The assay was highly discriminative in identifying 49 distinct VNTR profiles among 59 individual isolates. A high level of VNTR profile heterogeneity was observed in isolates from within the same country and among countries. These VNTR profiles remained stable after the strains were passaged extensively under routine laboratory culture conditions. In contrast to the S. enterica serovar Typhi isolates, an absence of TR3 amplicons and a lack of length polymorphisms in TR1 and TR2 amplicons were observed for other S. enterica serovars, such as Salmonella enterica serovar Typhimurium, Salmonella enterica serovar Enteritidis, and Salmonella enterica serovar Paratyphi A, B, and C. DNA sequencing of the amplified VNTR regions substantiated these results, suggesting the high stability of the multiplex PCR assay. The multiplex-PCR-based VNTR profiling developed in this study provides a simple, rapid, reproducible, and high-resolution molecular tool for the epidemiological analysis of S. enterica serovar Typhi strains.

Matched MeSH terms: Salmonella typhi/genetics
Ribotyping of Salmonella enterica serovar Typhi isolates from Papua New Guinea over the period 1977 to 1996

Combs BG, Passey M, Michael A, Pang T, Lightfoot D, Alpers MP

P N G Med J, 2005 Sep-Dec;48(3-4):158-67.
PMID: 17212062

The prevalence of typhoid in the Papua New Guinea (PNG) highlands region increased rapidly in the mid-1980s, and now remains endemic. In this study ribotyping has been used to examine the number and types of Salmonella enterica serovar Typhi strains present during the 1977-1996 period. The ribotyping banding pattern results were based on Cla I and Eco RV digests. The 57 PNG isolates were divided into 11 different ribotypes. Comparison of ribotypes using coefficient of similarity values revealed a diverse group of ribotypes. Several strains appear to be endemic in PNG For instance, ribotypes 1, 2 and 3 were most commonly found among PNG isolates and isolates with these ribotypes have been cultured over a period of at least 11 years (1985-1996). Ribotype 3 was also observed in isolates from Malaysia and Thailand. Also found in PNG were ribotypes 4, 5, 6, 7, 8, 9, 16 and 17. The ribotyping suggests that serovar Typhi strains present in PNG include unique strains of serovar Typhi and also strains that are common to other countries.

Matched MeSH terms: Salmonella typhi/genetics*
Amplification of ST50 gene using dry-reagent-based polymerase chain reaction for the detection of Salmonella typhi

Aziah I, Ravichandran M, Ismail A

Diagn Microbiol Infect Dis, 2007 Dec;59(4):373-7.
PMID: 17964105

Conventional polymerase chain reaction (PCR) testing requires many pipetting steps and has to be transported and stored in cold chain. To overcome these limitations, we designed a ready-to-use PCR test for Salmonella typhi using PCR reagents, primers against the ST50 gene of S. typhi, a built-in internal amplification control (IAC), and gel loading dye mixed and freeze-dried in a single tube. The 2-step dry-reagent-based assay was used to amplify a 1238-bp target gene and an 810-bp IAC gene from 73 BACTEC blood culture broths (33 true positives for S. typhi and 40 true negatives for non-S. typhi). The sensitivity, specificity, positive predictive value, and negative predictive value of the PCR assay were 87.9%, 100%, 100%, and 90.9%, respectively. We suggest that this rapid 2-step PCR test could be used for the rapid diagnosis of typhoid fever.

Matched MeSH terms: Salmonella typhi/genetics
Analysis and construction of pathogenicity island regulatory pathways in Salmonella enterica serovar Typhi

Ong SY, Ng FL, Badai SS, Yuryev A, Alam M

J Integr Bioinform, 2010;7(1).
PMID: 20861532 DOI: 10.2390/biecoll-jib-2010-145

Signal transduction through protein-protein interactions and protein modifications are the main mechanisms controlling many biological processes. Here we described the implementation of MedScan information extraction technology and Pathway Studio software (Ariadne Genomics Inc.) to create a Salmonella specific molecular interaction database. Using the database, we have constructed several signal transduction pathways in Salmonella enterica serovar Typhi which causes Typhoid Fever, a major health threat especially in developing countries. S. Typhi has several pathogenicity islands that control rapid switching between different phenotypes including adhesion and colonization, invasion, intracellular survival, proliferation, and biofilm formation in response to environmental changes. Understanding of the detailed mechanism for S. Typhi survival in host cells is necessary for development of efficient detection and treatment of this pathogen. The constructed pathways were validated using publically available gene expression microarray data for Salmonella.

Matched MeSH terms: Salmonella typhi/genetics*
Fulltext Complete genome sequence of Salmonella enterica subsp. enterica serovar Typhi P-stx-12

Ong SY, Pratap CB, Wan X, Hou S, Abdul Rahman AY, Saito JA, et al.

J Bacteriol, 2012 Apr;194(8):2115-6.
PMID: 22461552 DOI: 10.1128/JB.00121-12

We report here the complete genome sequence of Salmonella enterica subsp. enterica serovar Typhi P-stx-12, a clinical isolate obtained from a typhoid carrier in India.

Matched MeSH terms: Salmonella typhi/genetics*

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