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Biomedical subjects

N Andorn

Publications and source records attributed to N Andorn.

9 recordsLinked to original sources
PubMed2006

Salmonella enterica serotype Virchow: epidemiology, resistance patterns and molecular characterisation of an invasive Salmonella serotype in Israel.

This study outlines the unique epidemiology of Salmonella enterica serotype Virchow in Israel. Between 1997 and 2002, the overall incidence of non-typhoid Salmonella enterica (NTS) decreased from 69.3 to 53.3 infections/100,000 population, but the incidence of S. Virchow increased (from 7.2 to 9.1 infections/100,000). Since 2000, S. Virchow has become the second-ranking NTS isolate, accounting for 17% and 27% of all stool and blood NTS isolates, respectively. Infants aged < 1 year had the highest incidence of isolation from stools (92.8/100,000). The incidence of isolation from blood was highest for infants aged <1 year (4.4/100,000). Only 6% of isolates were susceptible to all ten antibiotic agents tested; 34% were resistant to one agent, 54% to one to three agents, and 40% to four to six agents. A high proportion of the tested isolates were resistant to nalidixic acid (89%), streptomycin (56%), tetracycline (43%), trimethoprim-sulphamethoxazole (38%) and chloramphenicol (28%), but none to ciprofloxacin or ceftriaxone. Pulsed-field gel electrophoresis revealed two closely related clusters, each containing a predominant pulsotype. Coupled with its invasive propensity, the increasing incidence of highly resistant S. Virchow in Israel is of real concern. Future research should focus on the sources of S. Virchow in the food chain in order to institute effective control measures.

Adolescent↗
PubMed2004

Blood invasiveness of Salmonella enterica as a function of age and serotype.

We explored the dual influence of the patient's age and the infecting serotype on the blood invasiveness patterns of non-Typhi Salmonella enterica (NTS). Blood invasiveness ratio (BIR) was calculated as the ratio between the number of blood and blood + stool isolates. Analysis of 14,951 NTS isolates showed that the BIR increased drastically above the age of 60 years, reaching levels 3.5-7 times higher compared to age group < 2 years. Different patterns of age-related invasiveness were observed for the five most common NTS serotypes (Enteritidis, Typhimurium, Virchow, Hadar, Infantis). Among children < 2 years, the BIR was highest for serotype Virchow and lowest for serotype Hadar, while in persons > or = 60 years it was highest for serotypes Enteritidis and lowest for serotype Infantis. The tendency of NTS serotypes to invade the bloodstream was significantly influenced by the patient's age, however the impact of age differed for various NTS serotypes.

Adolescent↗
PubMed2004

Variability of Shigella flexneri serotypes in Israel during a period of two years: 2000 and 2001.

During a period of 2 years (2000 and 2001) 996 Shigella flexneri strains from sporadic cases in Israel were sent to the National Shigella Reference Centre (NSRC) by hospital and outpatient clinics. The most common serotypes were 2a, 6 and 1b, accounting for 88.4% of all isolates. They were investigated according to the monthly distribution of the strains, and the age and sex of the patients. The severity of the disease was assessed by a hospital/outpatient distribution (H/Od) of the isolates, based on the location of the sending laboratory. The most affected age groups were 0-11 months and 1-4 years, and the prevalent serotype was 2a, while serotype 6 was dominant in the 5-14 years age group. More cases were registered during the hot season, and there were some serotype-related variations. Overall, 62.1% of the samples were from male patients. Serotype 1b was dominant in the male/female ratio, although it was third in general prevalence. According to the H/Od serotype 2a was more common in hospitalized males and serotype 6 in outpatients, both male and female. These variations, as well as changes in serotype prevalence in the past, underscore the importance of serotype monitoring as part of the public health strategies for reducing the burden of Shigella flexneri infections.

Adolescent↗
PubMed2004

Antimicrobial resistance of Shigella flexneri serotypes in Israel during a period of three years: 2000-2002.

This is a surveillance study of the antimicrobial resistance of the S. flexneri group in the context of its serotype diversity. It includes 1422 isolates, which were sent to the National Shigella Reference Centre (NSRC) by hospitals and outpatient clinics in Israel during a 3-year period (2000-2002). The strains were identified and classified according to the prevalence and antigenic structure of their serotypes. All samples were checked for resistance to ampicillin (AMP), trimethoprim-sulphamethoxazole (TMP-SMX), ceftriaxone (CRO), tetracycline (TE), nalidixic acid (NAL), and chloramphenicol (C) by the disk diffusion method of Bauer et al. There were significant differences in their resistance to the individual antimicrobials with resistance to AMP, TE and C being lower among the strains of serotype 6 than among those of serotypes 2a and 1b. The resistant phenotypes were also serotype-specific. The similarities both in individual and in phenotype resistance between the rare and the prevalent serotypes (but not serotype 6) may be attributed to their antigenic relatedness. The serospecificity of the antimicrobial resistance was not affected by external factors such as seasonality and source (hospital or outpatient laboratory) of the isolates, and the age and sex of the patients. The serotype-specific approach can assist in properly assessing the problem of the antimicrobial resistance of the Shigella flexneri group and may prove useful for the empirical therapy of shigellosis. The observed interdependency between resistance and the antigenic specificity and relatedness of the S. flexneri serotypes requires additional investigation.

Adolescent↗
PubMed1992

Radiation-induced generation of chlorine derivatives in N2O-saturated phosphate buffered saline: toxic effects on Escherichia coli cells.

The radiolysis of aqueous chloride solutions has been investigated using pulse and steady-state methods. We have found a correlation between the yields of Cl2- and HOCl formed in pulse-irradiated N2O-saturated solutions. The yields increased with the increasing concentrations of Cl- and phosphate. Phosphate enhanced the yield of Cl2- in neutral solutions because of a proton transfer from H2PO4- to HOCl- with a rate constant of (2.6 +/- 0.5) x 10(8) M-1s-1. HOCl could not be detected in pulse-irradiated He or air-saturated, phosphate-buffered saline (PBS) solutions or in gamma-irradiated N2O, He, or air-saturated PBS solutions. The results are discussed in light of previously suggested mechanisms for the formation and decay of Cl2-. Pulse-irradiated N2O-saturated PBS solutions have a lethal effect on Escherichia coli cells, which is proportional to the amount of HOCl in the solutions. Gamma-irradiation of cells in N2O-saturated PBS solution also raises the radiosensitivity of the cells, although HOCl does not accumulate in this system. The effects of the radiation-induced toxic products on E. coli cells are similar to the effects of NaOCl. The cell membrane is probably the site of physiological injury induced by the radiation products.

Adenosine Triphosphate↗
PubMed1984

Immunoadsorption of histidinol dehydrogenase in the presence of urea.

Urea inhibits the activity of histidinol dehydrogenase from Escherichia coli B, prevents precipitation of the enzyme by specific antibodies and dissolves immunoprecipitates which were formed in the absence of urea. However, immunoadsorption of the enzyme to Sepharose-bound antibodies can take place in the presence of high concentrations (5-8 M) of urea. The immobilized antibody-bound enzyme exhibits almost full activity after removal of the urea and is inhibited by soluble specific antibodies in the presence of urea. The possibility of using immunoadsorption in the presence of urea for the study of insoluble proteins is discussed.

Alcohol Oxidoreductases↗
PubMed1982

Purification and properties of histidinol dehydrogenase from Escherichia coli B.

Histidinol dehydrogenase has been purified from a derepressed mutant of Escherichia coli B. A molecular weight of about 91,000 was estimated by gel filtration. The native enzyme seems to be composed of two similar subunits which have a molecular weight of 52,000 as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The pI of the enzyme as determined by isoelectric focusing is 4.75. The enzyme is maximally active at pH 9.5. It is highly specific for NAD+ and histidinol, with a Km (NAD+) of 0.57 mM and a Km (histidinol) of 14 microM. Mn2+ is required for maximal activity. The enzyme is completely inactivated by 8 M-urea but regains its activity very quickly upon removal of the urea. Mn2+ and histidinol protect the enzyme from heat inactivation.

Alcohol Oxidoreductases↗