Effect of growth conditions on heat resistance of Arizona bacteria grown in a chemostat.
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The effects of various growth conditions on the heat resistance of Arizona bacteria grown in a continuous-culture device (chemostat) were studied. Using either glucose, NH4Cl, NaH2PO4, or MgCl2 as the rate-limiting nutrient, it was found that the heat resistance, in all cases depended on the dilution rate and, hence, growth rate of the culture. Cells grown at high dilution rates were less heat resistant than those grown at low dilution rates. If, however, the dilution rate was maintained at a constant rate, the higher the growth temperature, the more heat resistant were the cells. Also at any given dilution rate, the cells were most heat resistant when grown at a near neutral pH. Most survival curves were biphasic in shape, indicating the presence in the population of two fractions of cells, one fraction being more resistant than the other. The size of the more heat-resistant fraction varied from almost 100% in very slow-growing cultures to practically 0% in cultures grown at a dilution rate of 0.67 h-1. (+info)
Development of high heat resistance of Arizona neotype by preincubation at 35 degrees C in media containing NaCl.
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When cells of Arizona neotype were preincubated at 35 degrees C in a medium containing NaCl (1 to 10%), they were found to be much more heat resistant upon being tested at 57 degrees C in a Trypticase (BBL Microbiology Systems) soy-yeast extract broth medium containing 10% NaCl than cells that had not been preincubated. Although no growth takes place during preincubation in the presence of 10% NaCl, some metabolic activity is necessary, since the presence of 2,4-dinitrophenol during incubation reduced the amount of gain in heat resistance. Incubation in the presence of N2, instead of air, abolished the effect. Chloramphenicol and rifampin, however, had no effect. Preincubated cells were just as heat resistant when separated by centrifugation and suspended in a fresh medium as when suspended in the incubated supernatant liquid. Conversely, the incubated supernatant liquid did not confer increased heat resistance upon unincubated cells. The increase in heat resistance, therefore, is probably a result of the salt osmotically plasmolyzing the cells by removing intracellular water, thus rendering the cellular contents more stable to heat. It is not known, however, why metabolic activity is necessary. (+info)
Plasmid-specified sucrose fermentation in Salmonella arizonae.
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Thirty cultures of Salmonella arizonae 47:r:253 (Ar 23:24-25) were isolated over 7 months from the faeces of a captive reptile. All were unusual in their inability to produce a positive o-nitrophenyl-beta-D-galactosidase reaction, and in their ability to ferment sucrose. These S. arizonae carried a plasmid having a molecular mass of 72 megadaltons which specified tetracycline resistance and a plasmid of 5 megadaltons which coded for the ability to ferment sucrose. The small size of this sucrose plasmid clearly distinguishes it from others which have been reported. (+info)
Lizards in the ecology of salmonellosis in Panama.
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Enteropathogenic bacteria was isolated from 131 of 447 (29.4%) neotropical Panamanian lizards belonging to 34 species of seven families. Overall, 147 strains of bacteria were isolated comprising 26 Salmonella and 10 Arizona serotypes. Gymnopthalmus speciosus had the highest infection rate, 12 of 13 individuals (92.3%), whereas Gonatodes fuscus exhibited the lowest, 1 of 18 (5.6%). The highest infection was detected in lizards whose behavioral patterns were secretive (42.0%) and terrestrial (42.6%), whereas the lowest infection was among the scansorial lizards (17.5%). Rates were highest during the dry season, from January through April. Many neotropical Panamanian lizards were multiply infected by Salmonella an Arizona strains representing representing a wide range of serotypes. Infected lizards were distributed in areas varying from remote rural and forested regions to urban developments, offering a potentially important reservoir of enteropathogenic bacteria known to cause infection in man and domestic animals. (+info)
Arizona hinshawii bacteraemia and meningitis in a child: a case report.
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An 8-week-old infant presented with Arizona hinshawii meningitis and bacteraemia. The child responded well to the administration of parenteral ampicillin and chloramphenicol. However, chloramphenicol was discontinued after one day of therapy, and A. hinshawii was recultured from the cerebrospinal fluid on the fifth day. Chloramphenicol therapy was restarted and the patient had an uneventful recovery. This report is the first description of A. hinshawii meningitis and should alert clinicians to the possible occurrence of this infection in endemic areas. (+info)
Salmonella infection acquired from reptilian pets.
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Two children presented with signs and symptoms of gastroenteritis. Salmonella chameleon was isolated from the stool of one child and also from an iguana kept in the home as a pet. Salmonella arizonae was isolated from the stool of the other child and also from four snakes sharing the same household. Exotic reptiles are unsuitable pets to share the home environment with infants. (+info)