Study of a Conditional Suicide System for Biological Containment of Bacteria in Germ-free Rats

Jacobsen, B.; Schlundt, Jørgen; Fischer, Gerhart W.

doi:10.3109/08910609309141314

Cited by 5 publications

(3 citation statements)

References 9 publications

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“…Escherichia coli BJ4, isolated from a Wistar rat at the National Food Agency, Denmark (Jacobsen et al , 1993), was used as the parent strain. Streptomycin‐resistant (str) (Krogfelt et al , 1993) and streptomycin‐ and rifampicin‐resistant (str/rif) (Krogfelt et al , 2000) derivatives were used as representatives of chromosomal mutations.…”

Section: Methodsmentioning

confidence: 99%

Thein vitrofitness cost of antimicrobial resistance inEscherichia colivaries with the growth conditions

Petersen

Aarestrup

Olsen

2009

FEMS Microbiology Letters

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The objective of this study was to investigate the influence of stressful growth conditions on the fitness cost of antimicrobial resistance in Escherichia coli BJ4 caused by chromosomal mutations and plasmid acquisition. The fitness cost of chromosomal streptomycin resistance increased significantly when the bacteria were grown under all stress conditions tested, while the cost in 1/3 Luria-Bertani was not significantly changed in a streptomycin+rifampicin mutant. The increase in the fitness cost depended in a nonregular manner on the strain/stress combination. The fitness cost of plasmid-encoded resistance on R751 did not differ significantly, and was generally less under stressful growth conditions than in rich media. The fitness cost associated with R751 with the multiple drug resistance cassette from Salmonella Typhimurium DT104 increased significantly only under stressful conditions at low pH and at high-salt concentrations. Strains with an impaired rpoS demonstrated a reduced fitness only during growth in a high-salt concentration. In conclusion, it was demonstrated that bacterial fitness cost in association with antimicrobial resistance generally increases under stressful growth conditions. However, the growth potential of bacteria with antimicrobial resistances did not increase in a straightforward manner in these in vitro experiments and is therefore probably even more difficult to predict in vivo.

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Section: Methodsmentioning

confidence: 99%

Thein vitrofitness cost of antimicrobial resistance inEscherichia colivaries with the growth conditions

Petersen

Aarestrup

Olsen

2009

FEMS Microbiology Letters

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“…A streptomycin‐resistant derivative of E. coli BJ4 isolated from a healthy Wistar rat at the National Food Agency, Denmark, [13] was used in all experiments. When acting as donor, this strain hosted plasmid RP4, which confers resistance to tetracycline and ampicillin.…”

Section: Methodsmentioning

confidence: 99%

Evidence of increased spread and establishment of plasmid RP4 in the intestine under sub-inhibitory tetracycline concentrations

Licht

Struve

Christensen

et al. 2003

FEMS Microbiology Ecology

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The consequences of using anti-microbial agents in a complex ecosystem like the animal intestine can be difficult to predict. We have looked at effects of modulations in growth of competing intestinal bacteria on transfer and establishment of new genetic elements in the intestinal microflora. For this purpose, we used tetracycline, which gradually reduces the growth rate of tetracycline-sensitive bacteria, as the concentration of this drug is increased. The effect of tetracycline on transfer and establishment of the plasmid RP4, which encodes resistance to this drug, in populations of Escherichia coli BJ4 colonizing the intestine was investigated. A tetracycline-sensitive E. coli BJ4 strain was allowed to establish in the gastrointestinal tract of mice, where after an isogenic E. coli BJ4 carrying RP4 was given to the mice per os. Tetracycline in the drinking water given to the animals was kept in concentrations that allowed the sensitive recipient strain to colonize the gut. A given 'window' between the highest and the lowest antibiotic doses tested was shown to be optimal for the establishment of transconjugants in the intestine. These observations are important for the evaluation of the effect of a given drug on the intestinal ecosystem. A reduced potential for growth of a given bacterial species, caused by the presence of sub-inhibitory concentrations of a bacteriostatic antibiotic, will facilitate establishment of competing (i.e. closely related) organisms, which have acquired resistance genes and therefore grow well in the presence of the drug.

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“…E. coli BJ4, which is O‐rough:K − :H2, was isolated from a healthy Wistar rat (Jacobsen et al ., 1993) and has been described in detail previously (Krogfelt et al ., 1993). Bacteria were always grown in the presence of 100 μl ml −1 streptomycin sulphate (Sigma).…”

Section: Methodsmentioning

confidence: 99%

Inhibition of Escherichia coli precursor‐16S rRNA processing by mouse intestinal contents

Licht

Tolker‐Nielsen

Holmstrøm³

et al. 1999

Environmental Microbiology

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The correlation between ribosome content and growth rate found in many bacterial species has proved useful for estimating the growth activity of individual cells by quantitative in situ rRNA hybridization. However, in dynamic environments, the stability of mature ribosomal RNA causes problems in using cellular rRNA contents for direct monitoring of bacterial growth activity in situ. In a recent paper, Cangelosi and Brabant suggested monitoring the content of precursors in rRNA synthesis (pre-rRNAs) as an alternative approach. These are rapidly broken down after the cessation of bacterial growth. We have applied fluorescence in situ hybridization of pre-16S rRNA to Escherichia coil cells growing in vitro in extracts from two different compartments of the mouse intestine: the caecal mucus layer, where E. coli grew rapidly, and the contents of the caecum, which supported much slower bacterial growth. The amounts of 23S rRNA and pre-16S rRNA measured for E. coil growing in intestinal mucus corresponded to that expected for bacteria with the observed growth rate. In contrast, the slow-growing E. coli cells present in intestinal contents turned out to have an approximately ninefold higher content of pre-16S rRNA than cultures of the same strain growing rapidly in rich media. We present results suggesting that the mouse intestinal contents contain an agent that inhibits the growth of E. coli by disturbing its ability to process pre-16S rRNA.

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Study of a Conditional Suicide System for Biological Containment of Bacteria in Germ-free Rats

Cited by 5 publications

References 9 publications

Thein vitrofitness cost of antimicrobial resistance inEscherichia colivaries with the growth conditions

Thein vitrofitness cost of antimicrobial resistance inEscherichia colivaries with the growth conditions

Evidence of increased spread and establishment of plasmid RP4 in the intestine under sub-inhibitory tetracycline concentrations

Inhibition of Escherichia coli precursor‐16S rRNA processing by mouse intestinal contents

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