Salmonella Typhi is a human restricted pathogen with a significant number of individuals as asymptomatic carriers of the bacterium. Salmonella infection can be effectively controlled if a reliable method for identification of these carriers is developed. In this context, the availability of whole genomes of carrier strains through high- throughput sequencing and further downstream analysis by comparative genomics approaches is very promising. Herein we describe the genome sequence of a Salmonella Typhi isolate representing an asymptomatic carrier individual during a prolonged outbreak of typhoid fever in Kelantan, Malaysia. Putative genomic coordinates relevant in pathogenesis and persistence of this carrier strain are identified and discussed.
Indicators, whether referred to as ecological, biological or environmental, help us in assessing environmental conditions. Hypothetically, joint influences are predicted of the parameters associated with the number of water-borne, food-borne and vector-borne cases in study areas. Regression analysis of the dependent variables in water—borne diseases such as Cholera, Typhoid, Dysentery and Hepatitis indicated that the total coly°orm, fecal colform, residual chlorine, mean monthly rainfall and temperature influence almost hay of the cases in the 3 District of Serernban. Thus, coordinated monitoring of physical, chemical and biological parameters is needed to continue to build databases and to develop models integrating environnrental and social conditions, consequences and costs.
On March 17, 2003 the Kelantan Health Department was notihed about a possible typhoid outbreak following a wedding party. An investigation was carried out to identiy the source and recommend control measures. Active case detection, yield investigation and case»control study were conducted. Cases were symptomatic attendees with a stool or blood culture positive for Salmonella
typhii. Each control had a negative culture and denied symptoms. Of the more than 1 OOO guests, 477 experienced fever; 152 met the case definition. The party hostess was found to be an Salmonelb typhii carrier. Syrup prepared with untreated well water was identified as the most likely source for this outbreak, with an odds ratio 14.0 (95% C1: 2.9, 104.1). This was a common source
outbreak of typhoid. We recommend that all food handlers at large parties be screened for typhoid and other foodborne diseases and samples of higherisk foods should be kept for few days after each event in case they are needed for testing.
1. (1) The injection of serum prepared especially against strains of typhoid bacilli strong in "O" and "Vi" antigens appeared during the epidemic at Singapore to be of value in the treatment of serious cases of typhoid fever, even at a comparatively late stage of the disease. The time for the routine use of such serum in treatment has perhaps not yet come, but strong indications for its use are severe toxaemia, or failure to improve with general treatment. 2. (2) The absence of eosinophil cells in a differential white blood count is of value in the diagnosis though it is not an absolute sign in either a negative or positive direction. 3. (3) Congenital immunity against typhoid fever appears to be powerful for several years of childhood, in Malaya and presumably elsewhere also. 4. (4) Compulsory inoculation is advocated as a public health measure of protection against typhoid fever in countries where the disease is endemic, but not earlier than the 5th year of age. c 1941
The determination of the high-risk area and clusters of typhoid cases is critical in typhoid control. The purpose of this study was to identify and describe the epidemiology and spatial distribution of typhoid in four selected districts in Kelantan using GIS (geographical information system). A total of 1215 (99%) of the cases were coordinated with GPS (global positioning system) and mapping was done using ArcGIS 9.2. Spatial analysis was performed to determine the cluster and high-risk area of typhoid. Results showed that typhoid incidence was not associated with race and sex. Most affected were from the age group of 5-14 followed by 15-24 year olds. Nine sub-districts were categorized as highly endemic. In addition typhoid has shown a significant tendency to cluster and a total of 22 hotspots were found in Kota Bharu, Bachok and Tumpat with a few sub districts identified as high risk for typhoid. No significant relationships between the treated water ratio and flood risk area were found with the cluster of cases. The cluster of typhoid cases in the endemic area did not appear to be related to environmental risk factors. Understanding the characteristics of these clusters would enable the prevention of typhoid disease in the future.
Hemolysin E (HlyE) is an immunogenic novel pore-forming toxin involved in the pathogenesis of typhoid fever. Thus, mapping of B-cell epitopes of Salmonella enterica serovar Typhi (S. Typhi) is critical to identify key immunogenic regions of HlyE. A random 20-mer peptide library was used for biopanning with enriched anti-HlyE polyclonal antibodies from typhoid patient sera. Bioinformatic tools were used to refine, analyze and map the enriched peptide sequences against the protein to identify the epitopes. The analysis identified both linear and conformational epitopes on the HlyE protein. The predicted linear GAAAGIVAG and conformational epitope PYSQESVLSADSQNQK were further validated against the pooled sera. The identified epitopes were then used to isolate epitope specific monoclonal antibodies by antibody phage display. Monoclonal scFv antibodies were enriched for both linear and conformational epitopes. Molecular docking was performed to elucidate the antigen-antibody interaction of the monoclonal antibodies against the epitopes on the HlyE monomer and oligomer structure. An in-depth view of the mechanistic and positional characteristics of the antibodies and epitope for HlyE was successfully accomplished by a combination of phage display and bioinformatic analysis. The predicted function and structure of the antibodies highlights the possibility of utilizing the antibodies as neutralizing agents for typhoid fever.
Malaysia is endemic for both these diseases and one should not be too surprised when faced with a diagnosis of co-infection of typhoid and malaria, as have been described in India and Canada. Here we describe one such case of Salmonella typhi and Plasmodium vivax infection.
Chronic carriers of Salmonella Typhi act as reservoirs for the organism and become the agents of typhoid outbreaks in a community. In this study, chronic carriers in Kelantan, Malaysia were first identified using the culture and polymerase chain reaction method. Then, a novel serological tool, designated Typhidot-C, was evaluated in retrospect using the detected individuals as control positives. Chronic carriage positive by the culture and polymerase chain reaction method was recorded at 3.6% (4 out of 110) among individuals who previously had acute typhoid fever and a 9.4% (10 out of 106) carriage rate was observed among food handlers screened during outbreaks. The Typhidot-C assay was able to detect all these positive carriers showing its potential as a viable carrier screening tool and can be used for efficient detection of typhoid carriers in an endemic area. These findings were used to establish the first carrier registry for S Typhi carriers in Malaysia.
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.
Salmonella osteomyelitis of the rib is a rare clinical entity. In our case, a muhidrug resistant Salmonella enterica serotype Typhi was isolated from an immuno-competent patient with osteomyclitis of the ribs, who was treated earlier with ciprotloxacin for typhoid fever. The patient was successfully treated for osteomyclitis with intravenous ceftriaxone.
The objective of this study was to develop an optimized assay for Salmonella Typhi biofilm that mimics the environment of the gallbladder as an experimental model for chronic typhoid fever. Multi-factorial assays are difficult to optimize using traditional one-factor-at-a-time optimization methods. Response surface methodology (RSM) was used to optimize six key variables involved in S. Typhi biofilm formation on cholesterol-coated polypropylene 96-well microtiter plates. The results showed that bile (1.22%), glucose (2%), cholesterol (0.05%) and potassium chloride (0.25%) were critical factors affecting the amount of biofilm produced, but agitation (275 rpm) and sodium chloride (0.5%) had antagonistic effects on each other. Under these optimum conditions the maximum OD reading for biofilm formation was 3.4 (λ600 nm), and the coefficients of variation for intra-plate and inter-plate assays were 3% (n = 20) and 5% (n = 8), respectively. These results showed that RSM is an effective approach for biofilm assay optimization.
Salmonella enterica serovar Typhi (S. Typhi) is a foodborne pathogen that causes typhoid fever and infects only humans. The ability of S. Typhi to survive outside the human host remains unclear, particularly in human carrier strains. In this study, we have investigated the catabolic activity of a human carrier S. Typhi strain in both planktonic and biofilm cells using the high-throughput Biolog Phenotype MicroArray, Minimum Biofilm Eradication Concentration (MBEC) biofilm inoculator (96-well peg lid) and whole genome sequence data. Additional strains of S. Typhi were tested to further validate the variation of catabolism in selected carbon substrates in the different bacterial growth phases. The analyzes of the carbon utilization data indicated that planktonic cells of the carrier strain, S. Typhi CR0044 could utilize a broader range of carbon substrates compared to biofilm cells. Pyruvic acid and succinic acid which are related to energy metabolism were actively catabolised in the planktonic stage compared to biofilm stage. On the other hand, glycerol, L-fucose, L-rhamnose (carbohydrates) and D-threonine (amino acid) were more actively catabolised by biofilm cells compared to planktonic cells. Notably, dextrin and pectin could induce strong biofilm formation in the human carrier strain of S. Typhi. However, pectin could not induce formation of biofilm in the other S. Typhi strains. Phenome data showed the utilization of certain carbon substrates which was supported by the presence of the catabolism-associated genes in S. Typhi CR0044. In conclusion, the findings showed the differential carbon utilization between planktonic and biofilm cells of a S. Typhi human carrier strain. The differences found in the carbon utilization profiles suggested that S. Typhi uses substrates mainly found in the human biliary mucus glycoprotein, gallbladder, liver and cortex of the kidney of the human host. The observed diversity in the carbon catabolism profiles among different S. Typhi strains has suggested the possible involvement of various metabolic pathways that might be related to the virulence and pathogenesis of this host-restricted human pathogen. The data serve as a caveat for future in-vivo studies to investigate the carbon metabolic activity to the pathogenesis of S. Typhi.
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.
A dot enzyme immunoassay (EIA) using 50-kD outer-membrane proteins (OMPs) of Salmonella typhi was compared with the Widal test for the serodiagnosis of typhoid fever in 109 febrile children admitted to a hospital in an endemic area. In the culture-positive typhoid group, the initial dot EIA was positive in 40 of 42 cases and the initial Widal test was positive in 41. In the culture-negative clinical typhoid group, both the dot EIA and the Widal test were positive in 17 of 18 cases. In the nontyphoidal fever group, the dot EIA was negative in all of 49 cases and the Widal test was negative in 44. With culture used as the gold standard, the dot EIA is as sensitive as the Widal test (95% vs. 98%), has a similar high negative predictive value (96% vs. 98%), and is more specific (75% vs. 67%). In addition, the dot EIA offers the advantages of simplicity, speed, early diagnosis, economy, and flexibility (i.e., other diagnostic tests can be conducted simultaneously).
Current studies were undertaken to determine the presence of a specific antigenic protein on the outer membrane of Salmonella typhi. Immunoblot analysis using sera from patients with fevers revealed that the 50 kD band was specifically recognized only by typhoid sera. The 50 kD band located on the outer membrane is protein by nature and is not a Vi (capsular), dH (flagellar), or O9 (somatic) antigen of S. typhi. These results indicate the usefulness of the specific antigen in the development of a serodiagnostic test for typhoid fever since antibodies of both the IgM and IgG class responses were obtained.
A nitrocellulose membrane strip dotted with a specific 50 kDa outer membrane protein of Salmonella typhi was applied for the serodiagnosis of typhoid fever. Using horseradish peroxidase conjugated IgM and IgG antibodies with 4-chloronaphthol as substrate, antibodies in typhoid patients were clearly visualised as bluish purple dots while sera from patients with non-typhoid fevers gave negative results. The detection of specific IgM and IgG antibodies in typhoid patients suggest either recent or current infection. Combined with the high specificity, reliability and rapidity of the test, the dot EIA technique provides a simple and useful method for the serodiagnosis of typhoid using a single serum specimen.
Analysis of diarrhoeal disease patterns in Malaysia from 1981-1986 suggested that infectious hepatitis ranked as the most predominant diarrhoeal disease followed by typhoid, food poisoning, dysentery and cholera. Although these five major food and water-borne diseases are still endemic in this country, diarrhoeal diseases per se no longer become an important public health problem in Malaysia. Enforcement of the cholera control program brought the incidence of the disease to a minimal. Unfortunately, this fatal form of diarrhoeal disease caused the greatest mortality compared to the others. Seasonal influence also played a part in controlling the occurrence of the disease. There was a preponderance of diarrhoeal diseases during the rainy season implicating contaminated water as a source of transmission. Although greater than half of the population has been supplied with piped water and sanitary latrines, a lot more has to be done before diarrhoeal diseases could be eliminated from this country.
Salmonella enterica serovar Typhi is the causative agent of typhoid fever, which causes nearly 21.7 million illnesses and 217,000 deaths globally. Herein, we describe the whole-genome sequence of the Salmonella Typhi strain ST0208, isolated from a sporadic case of typhoid fever in Kuala Lumpur, Malaysia. The whole-genome sequence and comparative genomics allow an in-depth understanding of the genetic diversity, and its link to pathogenicity and evolutionary dynamics, of this highly clonal pathogen that is endemic to Malaysia.