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Epidemiology of enteric fevers

Fletcher W

Malayan Medical Journal, 1928;3:59-60.

Matched MeSH terms: Salmonella typhi
Complications of bacteriologically confirmed typhoid fever in children

Malik AS

J Trop Pediatr, 2002 Apr;48(2):102-8.
PMID: 12022423

To find the incidence, markers and nature of complications of typhoid fever, we studied 102 children with cultures positive for Salmonella typhi in a cross-sectional study, prospectively, over a period of almost 5 years. All isolates were sensitive to commonly used antibiotics. One third of these children developed complications which included: anicteric hepatitis, bone marrow suppression, paralytic ileus, myocarditis, psychosis, cholecystitis, osteomyelitis, peritonitis, pneumonia, haemolysis, and syndrome of inappropriate release of antidiuretic hormone (SIADH). Twelve children developed multiple complications. If hepatitis is excluded from the complications, the rate of complications in bacteriologically confirmed cases of typhoid fever drops to 11 per cent. These complications were not related to: the age or sex of patients, duration of illness before admission, use of antibiotics before admission, nutritional status, level of 'O' or 'H' titre, presence of IgM or IgG antibodies, or treatment with chloramphenicol or ampicillin. Children with splenomegaly, thrombocytopenia or leukopenia were more likely to develop complications.

Matched MeSH terms: Salmonella typhi/isolation & purification*
Serum C-reactive protein concentrations in Malaysian children with enteric fever

Choo KE, Davis TM, Henry RL, Chan LP

J Trop Pediatr, 2001 Aug;47(4):211-4.
PMID: 11523761

To investigate the role of serum C-reactive protein (CRP) in the diagnosis of typhoid fever, we studied 227 febrile Malaysian children hospitalized during a 12-month period. The children were: culture-positive for Salmonella typhi (Group 1; n = 108); culture-negative but with typical clinical features of typhoid fever (Group 2; n = 60); or had non-typhoidal illness (Group 3; n = 59). Group 1 children had the highest serum CRP concentrations (geometric mean [SD range]; 43 [12-150] mg/l vs. 26 [8-85] mg/l in Group 2 and 21 [4-110] mg/l in Group 3; p < 0.001). In regression analysis, age, patient group and fever duration were independently associated with serum CRP (p < 0.05) but gender was not. In Group 1 patients, there was a significant positive association between serum CRP and Widal O and H agglutinin titres. In receiver-operator characteristic (ROC) analysis of serum CRP for Groups 1 and 2 combined, compared with Group 3, the area under the curve (AUC) was 0.65. These data show that the serum CRP is highest in culture-positive children with enteric fever and reflects the immune response to the infection in this group. Nevertheless, serum CRP had relatively low sensitivity and specificity for confirmed or clinically diagnosed typhoid fever (68 and 58 per cent, respectively at 'cut-off' concentration 30.0 mg/l), and an AUC value only moderately above that associated with no predictive power (0.5). Although of limited use as a primary diagnostic test, a raised serum CRP may still have a place as one of a range of features that facilitate assessment of a febrile child in a typhoid-endemic area.

Matched MeSH terms: Salmonella typhi/isolation & purification*
Effect of reduced graphene oxide-hybridized ZnO thin films on the photoinactivation of Staphylococcus aureus and Salmonella enterica serovar Typhi

Teh SJ, Yeoh SL, Lee KM, Lai CW, Abdul Hamid SB, Thong KL

J. Photochem. Photobiol. B, Biol., 2016 Aug;161:25-33.
PMID: 27203568 DOI: 10.1016/j.jphotobiol.2016.05.013

The immobilization of photocatalyst nanoparticles on a solid substrate is an important aspect for improved post-treatment separation and photocatalyst reactor design. In this study, we report the simple preparation of reduced graphene oxide (rGO)-hybridized zinc oxide (ZnO) thin films using a one-step electrochemical deposition, and investigated the effect of rGO-hybridization on the photoinactivation efficiency of ZnO thin films towards Staphylococcus aureus (S. aureus) and Salmonella enterica serovar Typhi (S. Typhi) as target bacterial pathogens. Field-emission scanning electron microscopy (FESEM) revealed the formation of geometric, hexagonal flakes of ZnO on the ITO glass substrate, as well as the incorporation of rGO with ZnO in the rGO/ZnO thin film. Raman spectroscopy indicated the successful incorporation of rGO with ZnO during the electrodeposition process. Photoluminescence (PL) spectroscopy indicates that rGO hybridization with ZnO increases the amount of oxygen vacancies, evidenced by the shift of visible PL peak at 650 to 500nm. The photoinactivation experiments showed that the thin films were able to reduce the bacterial cell density of Staph. aureus and S. Typhi from an initial concentration of approximately 10(8) to 10(3)CFU/mL within 15min. The rGO/ZnO thin film increased the photoinactivation rate for S. aureus (log[N/No]) from -5.1 (ZnO) to -5.9. In contrast, the application of rGO/ZnO thin film towards the photoinactivation of S. Typhi did not improve its photoinactivation rate, compared to the ZnO thin film. We may summarise that (1) rGO/ZnO was effective to accelerate the photoinactivation of S. aureus but showed no difference to improve the photoinactivation of S. Typhi, in comparison to the performance of ZnO thin films, and (2) the photoinactivation in the presence of ZnO and rGO/ZnO was by ROS damage to the extracellular wall.

Matched MeSH terms: Salmonella typhi/drug effects*; Salmonella typhi/radiation effects
Usefulness of the Widal test in diagnosing childhood typhoid fever in endemic areas

Choo KE, Razif AR, Oppenheimer SJ, Ariffin WA, Lau J, Abraham T

J Paediatr Child Health, 1993 Feb;29(1):36-9.
PMID: 8461177

Data are presented for 2382 children investigated for fever in a Malaysian hospital between 1984 and 1987 when Widal tests and blood cultures were a routine part of every fever screen. There were 145 children who were culture positive (TYP-CP) for Salmonella typhi, while 166 were culture negative but were diagnosed as having typhoid (TYP-CN). Analyses of the sensitivity and specificity of combinations of initial Widal titres in predicting a positive S. typhi culture in a febrile child (culture positive vs the rest) showed the best model to be an O- and/or H-titre of > or = 1 in 40 (sensitivity 89%; specificity 89%). While the negative predictive value of the model was high (99.2%) the positive predictive value remained below 50% even for very high titres of O and H (> 1 in 640), at which point the specificity was 98.5%, supporting the clinical view that a high proportion of the TYP-CN patients really were typhoid but were missed by culture. The TYP-CN patients showed a very similar clinical and age profile to TYP-CP patients. The length of history of fever did not affect the initial Widal titre in culture positive cases. The Widal test in children remains a sensitive and specific 'fever screen' for typhoid although it will not identify all cases. In children, lower cut-off points for O- and H-titres should be used than are generally recommended.

Matched MeSH terms: Salmonella typhi/immunology; Salmonella typhi/isolation & purification*
Integration of molecular dynamics simulation and hotspot residues grafting for de novo scFv design against Salmonella Typhi TolC protein

Leong SW, Lim TS, Ismail A, Choong YS

J. Mol. Recognit., 2018 05;31(5):e2695.
PMID: 29230887 DOI: 10.1002/jmr.2695

With the development of de novo binders for protein targets from non-related scaffolds, many possibilities for therapeutics and diagnostics have been created. In this study, we described the use of de novo design approach to create single-chain fragment variable (scFv) for Salmonella enterica subspecies enterica serovar Typhi TolC protein. Typhoid fever is a global health concern in developing and underdeveloped countries. Rapid typhoid diagnostics will improve disease management and therapy. In this work, molecular dynamics simulation was first performed on a homology model of TolC protein in POPE membrane bilayer to obtain the central structure that was subsequently used as the target for scFv design. Potential hotspot residues capable of anchoring the binders to the target were identified by docking "disembodied" amino acid residues against TolC surface. Next, scFv scaffolds were selected from Protein Data Bank to harbor the computed hotspot residues. The hotspot residues were then incorporated into the scFv scaffold complementarity determining regions. The designs recapitulated binding energy, shape complementarity, and interface surface area of natural protein-antibody interfaces. This approach has yielded 5 designs with high binding affinity against TolC that may be beneficial for the future development of antigen-based detection agents for typhoid diagnostics.

Matched MeSH terms: Salmonella typhi/immunology; Salmonella typhi/metabolism*
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/classification*; Salmonella typhi/genetics
Convenient and versatile DNA extraction using agarose plugs for ribotyping of problematic bacterial species

Nair S, Karim R, Cardosa MJ, Ismail G, Pang T

J Microbiol Methods, 1999 Oct;38(1-2):63-7.
PMID: 10520586

We describe a convenient, versatile and safe method for preparing bacterial DNA for ribotyping analysis. In this method, extraction of bacterial DNA from Salmnonella typhi and Burkholderia pseudomallei. and subsequent restriction endonuclease digestion, was performed in agarose blocks/plugs thus minimizing shearing and loss of DNA, problems commonly associated with liquid phase phenol extraction. Digested DNA in the plugs was then electrophoresed directly, transferred to nylon membranes and hybridized with labeled rDNA probes in the usual manner to provide reproducible restriction patterns. This method is particularly useful for bacterial species where standard DNA extraction in the liquid phase using phenol has been problematic (e.g. B. pseudomallei) but can be used for any bacterial species. The DNA extracted within the agarose plugs can be stored for long periods and can be used in other, widely-used typing methods such as pulsed-field gel electrophoresis (PFGE) and PCR-based techniques. Embedding live cells directly in agarose plugs also minimizes the risk of exposure to these virulent human pathogens among laboratory workers.

Matched MeSH terms: Salmonella typhi/isolation & purification; Salmonella typhi/chemistry*
One-step differential detection of Salmonella enterica serovar Typhi, serovar Paratyphi A and other Salmonella spp. by using a quadruplex real-time PCR assay

Teh CSJ, Lau MY, Chong CW, Ngoi ST, Chua KH, Lee WS, et al.

J Microbiol Methods, 2021 04;183:106184.
PMID: 33662480 DOI: 10.1016/j.mimet.2021.106184

Diseases caused by typhoidal and non-typhoidal Salmonella remain a considerable threat to both developed and developing countries. Based on the clinical symptoms and serological tests, it is sometimes difficult to differentiate the Salmonella enterica serovar Paratyphi A (S. enterica serovar Paratyphi A) from serovar Typhi (S. enterica serovar Typhi). In this study, we developed a quadruplex real-time polymerase chain reaction (PCR) assay with an internal amplification control (IAC), to simultaneously differentiate S. enterica serovar Paratyphi A from serovar Typhi and to detect other Salmonella serovars which cause salmonellosis in humans. This assay was evaluated on 155 salmonellae and non-salmonellae strains and demonstrated 100% specificity in species differentiation. Inclusion of an IAC did not affect the efficiency of the assay. Further evaluation using a blind test on spiked stool, blood and food specimens showed that the detection limit was at 103 -104 CFU/mL (or g) and a high PCR efficiency with different targets (R2 > 0.99), except for S. enterica serovar Paratyphi A in blood. This assay has been applied to clinical specimens to detect the causative agents of gastrointestinal infections and has successfully identified 6 salmonellosis patients from the 50 diarrhoea patients. The quadruplex real-time PCR developed in this study could enhance the detection and differentiation of salmonellae. This assay could be applied to stools, blood and food based on the notable performance in the simulation tests and field evaluation.

Matched MeSH terms: Salmonella typhi/genetics; Salmonella typhi/isolation & purification*
A simple adherence test for detection of IgM antibodies in typhoid

Ong LY, Pang T, Lim SH, Tan EL, Puthucheary SD

J Med Microbiol, 1989 Jul;29(3):195-8.
PMID: 2473209

A simple adherence test to detect IgM antibodies in patients with typhoid is described. The test utilises the IgM-"capture" approach, in which the test serum is applied to microtitration plate wells previously coated with anti-human IgM, followed by application of a stained Salmonella typhi antigen suspension which shows adherence in positive cases. By this test, 58 (95%) of 61 sera from confirmed cases of typhoid possessed IgM antibodies to the H or O or both antigens of S. typhi. In patients for whom a diagnosis of typhoid was based only on a significant Widal-test titre, 31 (41%) of 76 sera had IgM antibodies to the H or O or both antigens of S. typhi. Some cross-reactivity of the IgM antibodies was detected, especially with the O antigens of S. paratyphi A and B. A total of 82 sera from non-typhoidal fevers (leptospirosis, typhus, dengue fever) showed no reactivity in this test. In normal sera there was no detectable IgM to the O antigen of S. typhi and only a small number (3.9%) had low levels of IgM to the H antigen. The significance and potential importance of this simple, sensitive, specific and economical test is discussed.

Matched MeSH terms: Salmonella typhi/immunology*
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*
Mimotopes of heat shock proteins of Salmonella enterica serovar Typhi identified from phage-displayed peptide library

Yuen HL, Shamala D, Thong KL

J Infect Dev Ctries, 2008 Aug 30;2(4):313-23.
PMID: 19741295

BACKGROUND: Heat shock proteins (HSPs) are known to be involved in the pathogenesis of Salmonella enterica serovar Typhi (S. Typhi), the causative agent of typhoid fever. The objective of this study was to apply a phage display library to identify mimotopes of two HSPs, HSP90 and DnaK in S. Typhi.
METHODOLOGY: A 12-mer random peptide library expressed on the surface of the filamentous phage, M13, was used to select the mimotopes of two S. Typhi heat shock proteins by biopanning with monoclonal antibodies (mAbs), DnaK and HSP90. The immunogenicity of the selected peptides was determined through binding affinity with polyclonal antibodies from pooled typhoid-confirmed patients' sera and purified HSPs mAb using Western blotting and ELISA.
RESULTS: Five rounds of biopanning resulted in enrichment of phage clones expressing the binding motifs TDxSTRP and FPSHYWLYPPPT, respectively. The selected peptides showed strong immunoreactivity with patients' sera. Thus, monoclonal antibodies against HSP and patient sera can select common mimotopes from the random peptide library.
CONCLUSION: These findings may provide fundamental information for further studies on diagnostic application or vaccine design against this aetiologic agent of typhoid fever.

Matched MeSH terms: Salmonella typhi/immunology*
Significance and value of the Widal test in the diagnosis of typhoid fever in an endemic area

Pang T, Puthucheary SD

J Clin Pathol, 1983 Apr;36(4):471-5.
PMID: 6833514

The diagnostic value of the Widal test was assessed in an endemic area. The test was done on 300 normal individuals, 297 non-typhoidal fevers and 275 bacteriologically proven cases of typhoid. Of 300 normal individuals, 2% had an H agglutinin titre of 1/160 and 5% had an O agglutinin titre of 1/160. On the basis of these criteria a significant H and/or O agglutinin titre of 1/320 or more was observed in 93-97% of typhoid cases and in only 3% of patients with non-typhoidal fever. Of the sera from typhoid cases which gave a significant Widal reaction, the majority (79.9%) showed increases in both H and O agglutinins and 51 of 234 (21.8%) of these sera were collected in the first week of illness. The significance and implications of these findings are discussed.

Matched MeSH terms: Salmonella typhi/immunology; Salmonella typhi/isolation & purification
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/classification*; 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/classification*; Salmonella typhi/genetics; Salmonella typhi/isolation & purification
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/classification; Salmonella typhi/drug effects*; 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*; Salmonella typhi/isolation & purification*; Salmonella typhi/pathogenicity
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*; Salmonella typhi/isolation & purification*
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/classification; Salmonella typhi/genetics; Salmonella typhi/isolation & purification*
Development of two salmonella-based oral vaccines against human respiratory syncytial virus

Azizi Jalilian F, Yusoff K, Suhaimi S, Amini R, Sekawi Z, Jahanshiri F

J Biol Regul Homeost Agents, 2015 Jan-Mar;29(1):7-18.
PMID: 25864737

Human respiratory syncytial virus is the most common cause of bronchiolitis and other respiratory infections in infants and the elderly worldwide. We have developed two new oral vaccines using Salmonella typhi TY21a to carry and express the immunogenic epitopes of RSV fusion (F) and attachment (G) glycoproteins on its surface, separately. To evaluate the efficacy of the designed vaccines, BALB/c mice were orally immunized and then infected with RSV. Immune response analyses showed that cellmediated, mucosal and humoral immunity in the vaccinated mice were significantly enhanced compared to the control group. Both vaccines generated a balanced Th1/Th2 immune response which is crucial for efficiency of vaccines against RSV. Furthermore, histopathological examination proved that these vaccines were safe as they did not cause any Th2-associated adverse effects in the lungs of RSV-infected mice. The findings of this research suggest that Salmonella-F and Salmonella-G vaccine candidates may have strong potential to prevent RSV infection.

Matched MeSH terms: Salmonella typhi/genetics

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