The epidemiology of chronic colonization of airways with Pseudomonas aeruginosa was monitored in 44 patients with cystic fibrosis (CF) by DraI/SpeI macrorestriction analyses of 489 isolates. Sequential P. aeruginosa isolates (144) that had been collected from 32 CF patients over < or = 2.5 years were investigated, and 12 patients were followed for 8 years after onset of colonization. Forty-eight different genotypes were uncovered from 481 typeable isolates. Ten genotypes were found in > 1 unrelated CF patient. The 6 most frequent clones were identified in 58% of isolates. Ten of the 12 patients monitored for 8 years were harboring their initially acquired P. aeruginosa clone at all times, with subtle shifts of fragment patterns indicating subclonal variation. During colonization, the bacteria gradually lost pyocin and phage typing responses, supporting the view that genotypically discordant P. aeruginosa strains develop a common phenotype.
The complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome XI has been determined. In addition to a compact arrangement of potential protein coding sequences, the 666,448-base-pair sequence has revealed general chromosome patterns; in particular, alternating regional variations in average base composition correlate with variations in local gene density along the chromosome. Significant discrepancies with the previously published genetic map demonstrate the need for using independent physical mapping criteria.
The epidemiology of Pseudomonas aeruginosa infection at a cystic fibrosis (CF) center was monitored over a 3-year period. A total of 835 isolates from 72 unrelated patients and 22 siblings with CF were analyzed by genome fingerprinting and serotyping, bacteriophage typing, and pyocin typing. For genome fingerprinting, bacterial chromosomes were digested with one of the restriction endonucleases SpeI, DraI, XbaI, SspI, and NheI, which cut only rarely, and subsequently separated by field inversion gel electrophoresis. The physical genome analysis allowed us to classify P. aeruginosa strains in terms of DNA relatedness. Related strains differed by fewer than six DraI bands in the fingerprint, whereas unrelated strains differed by more than 20 DraI bands. All unrelated CF patients were colonized with different strains. The absence of a nosocomial spread of organisms at the CF center was attributed to the strict hygiene measures observed at the hospital. CF siblings were harboring either identical or closely related strains; transmission within the family is thought to be the most likely cause. In cystic fibrosis (CF), chronic lung infection with Pseudomonas aeruginosa, which is found in the majority of patients, is thought to be primarily responsible for pulmonary deterioration and reduced life expectation (15). Cross infection among CF patients may increase the prevalence of infections caused by these bacteria. We tried to determine the extent of P. aeruginosa cross infection by typing respiratory isolates. Besides the established methods of serotyping, bacteriophage typing, and pyocin typing, the novel technique of genome fingerprinting was applied to this problem as follows (8). Chromosomal DNA was digested with restriction endonucleases that cut only rarely, and the large fragments thus obtained were subsequently separated by field inversion gel electrophoresis (FIGE) (3). The pattern of restriction fragments is characteristic for each strain and provides an estimate of the degree of genomic relationship among the strains.
A complete macrorestriction map of the 5.9 Mb genome of Pseudomonas aeruginosa PAO (DSM 1707) was constructed by the combination of various one‐ and two‐dimensional pulsed field gel electrophoresis techniques. A total of 51 restriction sites (36 SpeI sites, 15 DpnI sites) were placed on the physical map yielding an average resolution of 110 kb. Several genes encoding virulence factors and enzymes of metabolic pathways were located on the anonymous map by Southern hybridization. Distances between the gene loci were similar on the genetic and physical maps, suggesting an even distribution of genome mobility throughout the bacterial chromosome. The four rRNA operons were organized in pairs of inverted repeats. The two‐dimensional macro‐restriction techniques described herein are generally applicable for the genome mapping of any prokaryote and lower eukaryote which yields resolvable fragment patterns on two‐dimensional pulsed field gels.
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