Occurrence of Salmonella typhi and Salmonella paratyphi in Jordan

In order to justify the surveillance control system and hygiene policy in Jordan, this study evaluated the occurrence of diarrhoea during the period 1988-2000, focusing on cases caused by Salmonella typhi and Salmonella paratyphi. From January 1988 to December 2000, the number of notified diarrhoeal cases by the Ministry of Health in Jordan was 1,399,563 million. Other groups of patients confined to the Governorate of Amman was diagnosed at Al-Battikhi Medical Laboratories. One-way ANOVA and Least Significant Difference (LSD) were carried out for statistical analysis. The number of reported diarrhea cases was 1,399,563, 53.0% were males, and 47.0% were females, among them, 80.3% were < 20 years and 19.7%, were > 20 years. Out of 245,255 patients tested for S. typhi and S. pararyphi, positive stool culture were 1992 (0.6%). Out of these, 960 (48.2%) were males and 1,032 (51.8%) were females (P = 0.028). The highest incidence rate (10.8) was observed in the year 1993, while the lowest incidence rate (0.9) was found in year 2000. A significant difference (P < 0.001) was found between the number of S. typhi and S. Paratyphi cases and year. The seasonal variation was also found to be significant (P < 0.0001), with the summer period showing the highest incident rate. A significant difference (P < 0.001) was observed between number of typhoid and paratyphoid cases and districts. A significance difference between number of typhoid and paratyphoid cases with age and sex. The group most affected was school age and adolescence. The demographic situation plays an important role in reporting typhoid and paratyphoid cases, where there might be an urgent indication for a better surveillance control system on water resources and disposal systems. S. typhi and S. paratyphi antibiotics resistance pattern showed they were resistant to tetracycline (56.0%, 58.0%), ampicillin (45.0%, 48.0%), trimethoprim (43.0%, 47.0%), cephtazidime (12.0%, 13.5%) chloramphenicol (6.8%, 7.2%), gentamycin (3.0%, 4.0%) neomycin (2.1. 1.8%), calvulanic acid (augmentin (1.4%, 2.2%) and norofloxacin (0.92%, 1.1%). Susceptibility to amikacin, ciprofloxacin, cetfriaxone, ofloxacine, imepenim, cefixime and cefotaxime was 100.0%. The increase in percentage of antibiotic resistant strain might indicate a need for a further prescribing policy for treatment.     

Comparative Virulotyping of Salmonella typhi and Salmonella enteritidis

Members of Salmonella enterica are important foodborne pathogens of significant public health concern worldwide. This study aimed to determine a range of virulence genes among typhoidal (S. typhi) and non-typhoidal (S. enteritidis) strains isolated from different geographical regions and different years. A total of 87 S. typhi and 94 S. enteritidis strains were tested for presence of 22 virulence genes by employing multiplex PCR and the genetic relatedness of these strains was further characterized by REP-PCR. In S. typhi, invA, prgH, sifA, spiC, sopB, iroN, sitC, misL, pipD, cdtB, and orfL were present in all the strains, while sopE, agfC, agfA, sefC, mgtC, and sefD were present in 98.8, 97.7, 90.8, 87.4, 87.4 and 17.2 %, of the strains, respectively. No lpfA, lpfC, pefA, spvB, or spvC was detected. Meanwhile, in S. enteritidis, 15 genes, agfA, agfC, invA, lpfA, lpfC, sefD, prgH, spiC, sopB, sopE, iroN, sitC, misL, pipD, and orfL were found in all S. enteritidis strains 100 %, followed by sifA and spvC 98.9 %, pefA, spvB and mgtC 97.8 %, and sefC 90.4 %. cdtB was absent from all S. enteritidis strains tested. REP-PCR subtyped S. typhi strains into 18 REP-types and concurred with the virulotyping results in grouping the strains, while in S. enteritidis, REP-PCR subtyped the strains into eight profiles and they were poorly distinguishable between human and animal origins. The study showed that S. typhi and S. enteritidis contain a range of virulence factors associated with pathogenesis. Virulotyping is a rapid screening method to identify and profile virulence genes in Salmonella strains, and improve an understanding of potential risk for human and animal infections.     

Siderophore production by Salmonella typhi

This study was initiated to determine the mechanism of iron-uptake in Salmonella typhi. When stressed for iron, microorganisms produce siderophores to obtain the necessary nutrient. Generally two types of siderophores exist: the phenolate-type predominantly produced by bacteria and the hydroxamate-type commonly secreted by fungi. Results of this investigation showed that S. typhi produced siderophores of the phenolate-type since culture supernatant of the organism grown under iron-deprivation supported the growth of the phenolate-dependent auxotroph. The culture supernatant when extracted for phenolate siderophores, also supported the growth of the phenolate auxotroph but not the hydroxamate auxotroph. Production of phenolate-type siderophores were further confirmed using biochemical assays. These results showed that S. typhi utilized the high-affinity iron transport system to obtain the necessary iron.     

The function of Salmonella typhi at different stages in the pathogenesis of typhoid infection

The complex study of the adhesive, colicinogenic and antigenic properties of S. typhi of different origin has revealed that adhesive properties can be observed more frequently in the strains isolated from the blood and bile and are completely absent in the strains isolated from feces. S. typhi strains of various origin do not essentially differ in their sensitivity to colicins and in the capacity for their production. Among the strains isolated from feces and bile, agents in the W-form occur more frequently than among the strains isolated from the blood. Escherichia coli, isolated from typhoid patients and carriers at the moment of the persistence of S. typhi in the body, are characterized by faintly pronounced antagonistic properties, enhanced sensitivity to colicins and rather pronounced hemagglutinating activity.     

Differentiation of Salmonella typhi using resistotyping

The potential value of resistotyping in the investigation of strain differences is illustrated by its application to Salmonella typhi . The method, although very demanding and prone to technical difficulties, is capable of yielding information about the identity of strains. In its present form the technique was shown to be able to characterize strains in such a manner that available epidemiological information was confirmed.     

Pathogenetic and immunological characteristics of different forms of the Salmonella typhi carrier state

Infectious granulomas with macrophages containing Salmonella typhi have been detected in the immune organs of the intestine of typhoid patients by means of morphological investigation techniques, immunofluorescent and electron microscopy. This suggests that typhoid granulomas form the basis of S. typhi primary carriership complicated by the relapses of this infection in cases of weakened cell-mediated immunity, which is proved by a decrease in the level of T-lymphocytes and by increased leukocyte migration index in relapses of typhoid fever and in S. typhi primary carriership. At the same time, the formation of S. typhi secondary carriership occurs in the process of the colonization of the altered organs and tissues of the body by S. typhi. This secondary carriership differs from the primary one by a number of pathogenetic signs. The detailed characterization of these two forms of S. typhi carriership is presented.     

Behaviour of temperate phage Mu in Salmonella typhi

We have developed a convenient system for genetic analysis of Salmonella typhi exploiting the properties of the mutator phage Mu. In spite of the fact that wild-type Salmonella typhi strains do not allow Mu to form plaques on them, we have shown that these strains are actually sensitive to the phage. It proved possible to use Mu to induce mutations and to promote intra- and interspecific genetic transfer, without having to introduce the phage into the bacteria by means other than infection. Furthermore, we isolated Salmonella typhi derivatives on which Mu formed plaques, and studied the behaviour of Mu in these and wild-type strains.     

Susceptibility of Salmonella typhimurium and Salmonella typhi to oxygen metabolites

Abstract The susceptibility of Salmonella typhimurium LT2 and of S. typhi 1079 to oxygen metabolites were compared. S. typhimurium LT2 and S. typhi 1079 were killed to an equal extent (about 40%) by the xanthine-xanthine oxidase (200 mU/ml) system. Among the various scavengers of oxygen metabolites, catalase alone inhibited the killing of S. typhimurium LT2 and S. typhi 1079 by the xanthine-xanthine oxidase system, indicating that hydrogen peroxide contributed to the killing of Salmonellae . The respiratory burst of murine macrophages was efficiently triggered by the ingestion of S. typhimurium LT2, S. typhimurium SL1102, and S. typhi 1079 and all to the same extent. However, in the range of the concentration of hydrogen peroxide produced by murine macrophages, neither S. typhimurium LT2 nor S. typhi 1079 were killed. Only S. typhimurium SL1102, a rough mutant of S. typhimurium LT2, was markedly susceptible under these conditions. The findings suggest that both S. typhimurium LT2 and S. typhi 1079 are resistant to oxygen-dependent killing mechanisms.     

Susceptibility of Salmonella typhimurium and Salmonella typhi to oxygen metabolites

The susceptibility of Salmonella typhimurium LT2 and S. typhi 1079 to oxygen metabolites were compared. S. typhimurium LT2 and S. typhi 1079 were killed to an equal extent (about 40%) by the xanthine-xanthine oxidase (200 mU/ml) system. Among the various scavengers of oxygen metabolites, catalase alone inhibited the killing of S. typhimurium LT2 and S. typhi 1079 by the xanthine-xanthine oxidase system, indicating that hydrogen peroxide contributed to the killing of Salmonellae. The respiratory burst of murine macrophages was efficiently triggered by the ingestion of S. typhimurium LT2, S. typhimurium SL1102, and S. typhi 1079 and all to the same extent. However, in the range of the concentration of hydrogen peroxide produced by murine macrophages, neither S. typhimurium LT2 nor S. typhi 1079 were killed. Only S. typhimurium SL1102, a rough mutant of S. typhimurium LT2, was markedly susceptible under these conditions. The findings suggest that both S. typhimurium LT2 and S. typhi 1079 are resistant to oxygen-dependent killing mechanisms.     

Genome plasticity and ori-ter rebalancing in Salmonella typhi

Genome plasticity resulting from frequent rearrangement of the bacterial genome is a fascinating but poorly understood phenomenon. First reported in Salmonella typhi, it has been observed only in a small number of Salmonella serovars, although the over 2,500 known Salmonella serovars are all very closely related. To gain insights into this phenomenon and elucidate its roles in bacterial evolution, especially those involved in the formation of particular pathogens, we systematically analyzed the genomes of 127 wild-type S. typhi strains isolated from many places of the world and compared them with the two sequenced strains, Ty2 and CT18, attempting to find possible associations between genome rearrangement and other significant genomic features. Like other host-adapted Salmonella serovars, S. typhi contained large genome insertions, including the 134 kb Salmonella pathogenicity island, SPI7. Our analyses showed that SPI7 disrupted the physical balance of the bacterial genome between the replication origin (ori) and terminus (ter) when this DNA segment was inserted into the genome, and rearrangement in individual strains further changed the genome balance status, with a general tendency toward a better balanced genome structure. In a given S. typhi strain, genome diversification occurred and resulted in different structures among cells in the culture. Under a stressed condition, bacterial cells with better balanced genome structures were selected to greatly increase in proportion; in such cases, bacteria with better balanced genomes formed larger colonies and grew with shorter generation times. Our results support the hypothesis that genome plasticity as a result of frequent rearrangement provides the opportunity for the bacterial genome to adopt a better balanced structure and thus eventually stabilizes the genome during evolution.     

Deoxyribonucleic Acid Adenine and Cytosine Methylation in Salmonella typhimurium and Salmonella typhi

The methylations of adenine in the sequence -GATC- and of the second cytosine in the sequence - [Formula: see text] - were studied in Salmonella typhimurium and in Salmonella typhi. The study was carried out by using endonucleases which restrict the plasmid pBR322 by cleavage at the sequences -GATC- (DpnI and MboI) and - [Formula: see text] - (EcoRII). The restriction patterns obtained for this plasmid isolated from transformed S. typhimurium and S. typhi were compared with those of pBR322 isolated from Escherichia coli K-12. In E. coli K-12, adenines at the sequence -GATC- and the second cytosines at - [Formula: see text] - are met hylated by enzymes coded for by the genes dam and dem, respectively. From comparison of the restriction patterns obtained, it is concluded that S. typhimurium and S. typhi contain genes responsible for deoxyribonucleic acid methylation equivalent to E. coli K-12 genes dam and dcm.