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.     

Trends in the development of the epidemic process in salmonellosis caused by Salmonella typhimurium and Salmonella enteritidis

The dynamics and structure of the epidemic process of Salmonella infections among the population of Perm in 1983-1988 was studied and the results of evaluation of antibiotic resistance of the dominating Salmonella species analyzed. The study revealed that a decrease in salmonellosis morbidity caused by S. typhimurium was associated with a limited circulation of anthroponotic (antibiotic-resistant) variants of Salmonellae and a relative increase in the proportion of zoonotic (antibiotic-sensitive) strains. At the period of elevated morbidity this Salmonella infection affected mainly young children in cold months, whereas in recent years seasonal morbidity rises shifted to spring-summer and summer-autumn months, affecting older age groups of the population. The study also revealed that a rise in salmonellosis morbidity caused by S. enteritidis was due to increased circulation of zoonotic variants of Salmonellae. Changes in the epidemiological situation necessitate correction of the system of epidemiological surveillance on Salmonella infections with the emphasis on sanitation measures in stock-breeding farms with unfavorable epidemiological situation.     

Trafficking of the Salmonella vacuole in macrophages

Salmonella enterica is a facultative intracellular pathogen which can replicate in macrophages. Intracellular Salmonella exist in a membrane-bound compartment called the Salmonella -containing vacuole. Most studies on Salmonella trafficking in relation to the endocytic pathway have concluded that the majority of Salmonella -containing vacuoles do not interact extensively with late endosomes and lysosomes. Numerous bacterial genes have been identified which are required for survival and replication in macrophages. These include the spv operon, located on the large virulence plasmid, the phoP-phoQ regulon, and those connected with the Salmonella pathogenicity island 2 type III secretion system. The functions of some of these genes are beginning to be understood. In this review, I discuss their roles in relation to our broader understanding of Salmonella trafficking in macrophages.     

Heat Resistance of Salmonella: the Uniqueness of Salmonella senftenberg 775W

Of approximately 300 cultures of Salmonella, representing 75 different serotypes, none was found to be as heat-resistant as S. senftenberg 775W. However, S. blockley 2004 was 5 times more heat-resistant and S. senftenberg 775W was 30 times more heat-resistant than S. typhimurium Tm-1, the reference strain in this study. All other strains of Salmonella tested, including 19 strains of S. senftenberg and 7 strains of S. blockley, had decimal reduction times at 57 C of about 1 min, equivalent to that of the reference organism, Tm-1. As observed in other bacterial species, strain 775W is more heat-sensitive in the log phase than in the stationary phase of growth. Cells from cultures grown at 44 C were more heat-resistant than those grown at either 35 or 15 C; the medium of growth, whether minimal or complex, made no appreciable difference in heat resistance. Cells from cultures limited by a carbon source were killed at a much slower rate than those limited by a nitrogen source and exhibited a 1-hr lag at 55 C before a significant rate of kill was attained. For any given set of growth conditions, strain 775W was always more heat-resistant than another strain of S. senftenberg, 197B, which has normal heat resistance.     

Plasticity in the purine-thiamine metabolic network of Salmonella

In Salmonella enterica, 5-aminoimidazole ribonucleotide (AIR) is the precursor of the 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP) pyrophosphate moiety of thiamine and the last intermediate in the common HMP/purine biosynthetic pathway. AIR is synthesized de novo via five reactions catalyzed by the purF, -D, -T, -G, and -I gene products. In vivo genetic analysis demonstrated that in the absence of these gene products AIR can be generated if (i) methionine and lysine are in the growth medium, (ii) PurC is functional, and (iii) 5-amino-4-imidazolecarboxamide ribotide (AICAR) has accumulated. This study provides evidence that the five steps of the common HMP/purine biosynthetic pathway can be bypassed in the synthesis of AIR and thus demonstrates that thiamine synthesis can be uncoupled from the early purine biosynthetic pathway in bacteria.     

Mutagenicity of anthraquinones in the Salmonella preincubation test

The mutagenicities of 15 naturally occurring anthraquinones were examined in Salmonella typhimurium strains TA98, TA100 and TA2637 by the preincubation method. 7 of the 15 compounds tested, i.e., chrysazin, emodin, islandicin, alizarin, chrysophanol, 2-hydroxyanthraquinone and emodic acid, were strong mutagens in strain TA2637 with metabolic activation. All of these compounds contain 1-3 hydroxyl groups, and some also have methyl groups. Cynodontin, an anthraquinone with 4 hydroxyl groups and 1 methyl group, was only slightly mutagenic in strain TA2637. 2-Hydroxyanthraquinone, alizarin, emodin, islandicin and chrysazin were also mutagenic in strain TA100 with S9 mix. All the bisanthraquinones tested, i.e., skyrin, (+)rugulosin, (-)luteoskyrin, (-)rubroskyrin and sennoside A, were non-mutagenic in this test system with or without metabolic activation. Unsubstituted anthraquinone and anthrone were also non-mutagenic. These results show that hydroxyl substituents are necessary for the mutagenicity of anthraquinones, the optimal substitutions being 1-3 hydroxyl groups per molecule. The 4th hydroxyl group, in the compound cynodontin reduces the mutagenicity considerably.     

Potential thermosensitive riboswitches in the genome of Salmonella

Currently, a number of structurally and functionally different thermosensitive elements, such as structurally and functionally different RNA thermometers, for controlling a variety of biological processes in bacteria, including virulence are known. These well-known RNA thermometers are structures, whether matched or mismatched, which are represented by either a single stretched hairpin structure or a few hairpins. Based on computer and thermodynamic analyses of 25 isolates of Salmonella enterica with complete genome, we have developed an algorithm and criteria to search for potential RNA thermometers, which will enable us to undertake a future search for potential riboswitches in the genomes of other socially significant pathogens. In addition to the well-known 4U RNA thermometer, another four hairpin-loop structures have been identified in S. enterica as new potential RNA thermometers and two of them are localized in 5′-UTR of virulence regulators gltB and yaeQ. They are highly conserved noncanonical structures and correspond to the necessary and sufficient conditions for forming RNA thermometers, since they are found in each of the 25 S. enterica genome isolates. We analyzed the thermosensitive motif in the pXO1 plasmid of Bacillus anthracis—an anthrax-causative pathogen—and visualized matched hairpins that form a cruciform structure in pUC8 supercoiled plasmid by atomic force microscopy.