Plasmid characteristics of Salmonella strains of various origins

Salmonella antibiotic-resistant strains, isolated from patients with hospital infections and from various environmental objects, showed lower virulence than antibiotic-sensitive strains in experiments on mice infected by intraperitoneal and enteral routes. Salmonella strains, sensitive to antimicrobial preparations, contained 1-2 plasmids, while those with multiple drug resistance contained 3-10 plasmids varying in their molecular weight. All these strains, with the exception of one laboratory strain, carried a plasmid with a molecular weight of about 60 Md. A decrease in the virulence of Salmonella strains, carrying R-plasmid, with respect to mice, their natural host, in experimental infection by the above-mentioned routes was probably unrelated to the loss of this plasmid. 80% of Salmonella strains with multiple resistance to antibiotics yielded positive results in the keratoconjunctival and conjunctival tests as compared with 42% of sensitive strains. These data suggest that Salmonella strains, carrying R-plasmid, retained pronounced capacity for local colonization.     

Enterotoxigenicity and invasiveness of Salmonella species

A large number of enterotoxigenic strains was encountered in a group 56 Salmonella cultures belonging to 8 species viz., S. alachua, S. anatum, S. dublin, S. enteritidis, S. hindmarsh, S. newport, S. typhimurium, S. weltevreden, and 5 serotypes of S. arizona (16:z₄:-; 48:1,v:z₅₆; 53:z₅₂:z₅₃; 60:r:z; 61:i:z₅₃). These cultures were isolated mainly from humans and animals suffering from gasteroenteritis. The enterotoxigenic (diarrhoeagenic) Salmonella cultures possess capacities for both skin permeation and epithelial penetration (invasiveness). Preliminary characterization revealed that Salmonella enterotoxin is a heatlabile protein of high molecular weight. It is suggested that enterotoxigenic and invasive propeties play a vital role in the pathogenesis of Salmonella diarrhoea.     

Effect of the R plasmids of Salmonella typhimurium strains of various origins on salmonella virulence

Antibiotic-multiresistant S. typhimurium strains, phagovars 20 and 25, of different origin (isolated in hospital infections transferred through everyday contacts and by alimentary route, as well as from samples taken from open water basins and sewage) have been found to carry both transmissible and nontransmissible R plasmids. The frequency of the transfer of R plasmids to Escherichia coli K-12 C 600 rif varies within 0.6 X 10(-5) and 0.7 X 10(-3) per donor cell. The direct transfer of plasmids to S. typhimurium has been mostly realized only in the presence of the mobilizing plasmid, the transfer frequency being 1.0 X 10(-7) to 2.2 X 10(-4) per donor cell. S. typhimurium transconjugates show decreased virulence in both enteral and intraperitoneal infection of mice.     

Enterotoxigenicity of diarrhoeal isolates of Salmonella bareilly

Whole cell cultures, cell-free supernatants, and cell sonicates from ten strains of Salmonella bareilly induced fluid accumulation in ligated rabbit and rat ileal loops. All strains had an intracellular vascular permeability factor, half were suckling mouse positive indicating the presence of a heat-stable type of activity. The toxin(s), however, were Immunologically distinct from the heat-labile toxin of Escherichia coll LT and cholera toxin. Besides enterotoxigenicity, all strains exhibited potential Invasive character.The authors are with the Department of Microbiology, Panjab University, Chandigarh, India 160 014. M. Saxena is the corresponding author.     

Enterotoxigenicity of Staphylococcus strains isolated from Spanish dry-cured hams.

The ability of 135 Staphylococcus strains isolated from Spanish dry-cured hams to produce enterotoxins in culture was investigated by the reversed passive latex agglutination method. A high percentage of enterotoxigenic Staphylococcus aureus strains (85.9%) was recorded, and 54.3% of these produced enterotoxin A. One of the two Staphylococcus epidermidis strains produced enterotoxin C. The reversed passive latex agglutination method yielded satisfactory results.     

Enterotoxigenicity of Staphylococcus strains isolated from Spanish dry-cured hams.

The ability of 135 Staphylococcus strains isolated from Spanish dry-cured hams to produce enterotoxins in culture was investigated by the reversed passive latex agglutination method. A high percentage of enterotoxigenic Staphylococcus aureus strains (85.9%) was recorded, and 54.3% of these produced enterotoxin A. One of the two Staphylococcus epidermidis strains produced enterotoxin C. The reversed passive latex agglutination method yielded satisfactory results.     

Effect of the transfer of the R plasmids of resistant Salmonella typhimurium strains of different origins on the phage sensitivity of Salmonella typhimurium

It has been shown that after the transfer of R-plasmids from S. typhimurium strains of different origin to S typhimurium strains sensitive to antibiotics these latter strains, as a rule, cannot be typed according to the scheme of Felix and Kellow These strains retain sensitivity to phages from I. G. Chiarkadze's collection, but the spectrum of their phage sensitivity is narrower. In one case the recipient was noted to change its phagovar to that of the donor. S. typhimurium donor strains, differing in the degree of their influence on the virulence of recipients, do not differ in their capacity for changing their sensitivity to the phages from the international collection of Felix and Kellow and from I. G. Chirakadze's collection.     

Ginseng extract exhibits antimutagenic activity against induced mutagenesis in various strains of Salmonella typhimurium

Ginseng has been reported to exhibit antioxidant and antimutagenic activity. The present study was undertaken with a view to confirm whether the antioxidant activity of Ginseng is responsible for its antimutagenic action. The concentrated root extract of Panax ginseng (Ginseng extract I) and its lyophilized powder (Ginseng extract II) obtained from two different manufacturing houses, were tested against mutagenesis using the well-standardized Ames microsomal test system. The extracts exhibited antimutagenic effect against hydrogen peroxide induced mutagenesis in TA100 strain, and against mutagenesis produced by 4-nitroquinoline-N-oxide in both TA98 and TA100 strains of Salmonella typhimurium. Both the extracts failed to show any antimutagenic potential against tert-butyl hydroperoxide (an oxidative mutagen) in TA102 strain, a strain highly sensitive to active oxygen species. The extracts also indicated a weak antioxidant activity in a series of in vitro test systems viz., 1,1-diphenyl picryl hydrazyl (DPPH) assay, hydrogen peroxide scavenging and superoxide anion scavenging. The results indicate that the protective effects shown by ginseng extract(s) against 4-nitroquinoline-n-oxide and hydrogen peroxide induced mutagenesis in TA98 and TA100 could mainly be due to its property to initiate and promote DNA repair rather than free radical scavenging action.     

Fibronectin binding to Salmonella strains

Abstract Recent investigations by many workers have elucidated the mechanisms which may explain the clinical observation that an excessive intake of dietary carbohydrates can aggravate oral candidosis. These include the enhancement of growth, multiplication and adherence of Candida species to oral surfaces and the production of excessive quantities of short-chain carboxylic acids as byproducts of sugar metabolism. The resultant acidic milieu, in addition to provoking a mucosal inflammatory reaction, could also activate the highly potent phospholipases and acid proteases of Candida and suppress the growth of normal commensal flora. A unifying hypothesis encompassing the above is proposed to explain the exacerbation of mucosal candidoses observed in environments replete with carbohydrates such as glucose and sucrose.     

The pathogenicity of strains of Salmonella paratyphi B and Salmonella java

AIMS: To relate the diseases caused by strains of Salmonella paratyphi B and S. java to pathogenic mechanisms expressed by these bacteria for the purpose of organism discrimination. METHODS AND RESULTS: Epidemiological data relating to cases of disease caused by strains of S. paratyphi B and S. java, isolated over a 10-year period, were analysed with respect to patients' symptoms, particularly those involving enteric fever. Strains of S. paratyphi B and S. java were also examined for a range of known pathogenic mechanisms. Infection with S. paratyphi B involved pyrexia in 12.5% of patients compared with 2.2% of patients infected with S. java. These organisms could not be differentiated based on the pathogenic properties examined. CONCLUSIONS: Strains of S. paratyphi B appear not to be a major cause of enteric fever but primarily a cause of gastroenteritis, in common with S. java. Both organisms express similar pathogenic mechanisms, and strains of S. java are probably d-tartrate utilizing variants of S. paratyphi B. SIGNIFICANCE AND IMPACT OF THE STUDY: Strains of S. paratyphi B are very closely related organisms, primarily causing gastroenteritis. From this study it would appear that strains of S. paratyphi B are not a major cause of enteric fever.