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Biomedical subjects

S Falkow

Publications and source records attributed to S Falkow.

At least 253 records · Page 14Linked to original sources
PubMed1981

Protein antigens from Staphylococcus aureus strains associated with toxic-shock syndrome.

Staphylococcus aureus isolates from patients with toxic-shock syndrome have two antigenic proteins that distinguish these strains from isolates obtained from patients who do not have this syndrome and who are colonized or infected with S. aureus. These proteins may either represent antigenic markers, the toxin (or toxins), or toxic subunits that cause the clinical manifestations of this disease.

Antigens, Bacterial↗
PubMed1981

Sequence homologies between A subunits of Escherichia coli and Vibrio cholerae enterotoxins.

The genes coding for the heat-labile enterotoxin LT produced by Escherichia coli have been cloned into the plasmid pBR313. Using DNA derived from the resulting chimeric plasmid, we determined the nucleotide sequence of two regions of the gene coding for the enzymatically active A subunit of LT. Translation of the nucleotide sequence gives the primary structure of the NH2-terminal and COOH-terminal regions of the LT A subunit. This permits direct comparison of the LT A subunit with the A subunit of cholera toxin. Our results show that the two toxins possess homologous sequences, of varying degrees, in both regions of their primary structure. The order of the component A1 and A2 polypeptides is A1-A2. The nucleotide sequence predicts the existence of a signal sequence of 18 amino acids at the NH2-terminus of the A subunit.

Amino Acid Sequence↗
PubMed1981

Characterization of plasmids and plasmid-associated determinants of Yersinia enterocolitica pathogenesis.

Yersinia enterocolitica isolates harboring a particular species of plasmid deoxyribonucleic acid showed a high degree of lethality for gerbils and caused the detachment of HEp-2 tissue cell monolayers. Strains cured of their plasmid deoxyribonucleic acid showed loss of these properties. However, invasiveness of HEp-2 cells was shown not to be a plasmid-mediated property. The expression of plasmid-associated properties, including at least three major outer membrane polypeptides, occurred during growth at 37 but not at 25 degrees C and was related to the concentration of calcium in the growth medium. The plasmid species associated with these properties ranged in molecular mass from 40 x 10(6) to 48 x 10(6) daltons and comprised a family of related plasmids.

Animals↗
PubMed1981

Molecular characterization of environmental and nontoxigenic strains of Vibrio cholerae.

Environmental and nontoxigenic strains of Vibrio cholerae 0-1 were examined for genes homologous to genes encoding Escherichia coli heat-labile enterotoxin (LT). Restriction fragments encoding LT A and B subunits were isolated from the recombinant plasmid EWD299 and labeled in vitro with 32P. These probes were then hybridized to deoxyribonucleic acid extracted from strains of V. cholerae and visualized by autoradiography. None of the nontoxigenic strains of V. cholerae 0-1 from Louisiana, Alabama, Maryland, Guam, Brazil, Bangladesh, or Great Britain hybridized with the LT probes, whereas all toxigenic strains exhibited homology. In addition, strains of V. cholerae non-0-1, "group F" vibrios, V. vulnificus, and Aeromonas hydrophila were tested, and all were negative except two strains of V. cholerae non-0-1. The presence of plasmids did not correlate with toxigenicity or nontoxigenicity in any of the species examined. Thus, it appears that these strains are not simple nontoxigenic mutants, but rather do not possess any genetic material encoding cholera toxin. Such strains therefore cannot revert and serve as a reservoir of cholera.

Cholera Toxin↗
PubMed1981

Construction and expression of recombinant plasmids encoding type 1 or D-mannose-resistant pili from a urinary tract infection Escherichia coli isolate.

Isolates of Escherichia coli from human urinary tract infections frequently express adherence properties found less often among normal intestinal isolates. These properties include adherence to human uroepithelial cells and primary monkey kidney cells, as well as D-mannose-resistant hemagglutination of human erythrocytes, and they are mediated by a pilus type different from type 1. The genes encoding this pilus type (pyelonephritis-associated pili, pap) and those encoding type 1 pili have been cloned from a urinary tract infection isolate of E. coli and transferred to an E. coli K-12 derivative. The recombinant plasmids were found to express functional pili and to endow the new host with all of the adherence properties of the urinary tract infection isolate. Both pilus types were found to be genetically distinct, and unlike the adherence genes from bovine, porcine, and human diarrheal isolates, both were found to be chromosomally encoded.

Adhesiveness↗
PubMed1981

Identification and cloning of the genetic determinant that encodes for the K88ac adherence antigen.

Strains of Escherichia coli capable of causing diarrhea in young pigs are often able to proliferate in the upper small intestine of the infected animal due to the presence of a specific surface antigen, K88. The genetic determinants for K88 antigen production and the ability to utilize the trisaccharide raffinose (Raf) are carried on a 50-megadalton plasmid. Recombinant deoxyribonucleic acid techniques were used to insert an 8.2-megadalton HindIII fragment carrying the K88ac gene(s) from the K88/Raf plasmid pPS100 into the vector pBR322. At lease six polypeptides encoded by this fragment were expressed in minicells. These polypeptides ranged in size from 18,000 to 70,000 daltons. The K88ac antigenic subunit, which has an apparent molecular weight of 23,500, was identified by immunoprecipitation with staphylococcal protein A as the coprecipitant.

Antigens, Bacterial↗
PubMed1981

R-factor cointegrate formation in Salmonella typhimurium bacteriophage type 201 strains.

The genetic and molecular properties of the plasmids in Salmonella typhimurium phase type 201 isolated are described. Such strains are resistant to streptomycin, tetracycline, chloramphenicol, ampicillin, kanamycin, and several other antimicrobial drugs, and are highly pathogenic for calves. These strains have been encountered with increasing frequency since 1972 in West Germany and The Netherlands. We show that isolates of this phage type constitute a very homogeneous group with regard to their extrachromosomal elements. These bacteria carry three small plasmids: pRQ3, a 4.2-megadalton (Md) colicinogenic plasmid; pRQ4, 3.4-Md plasmid that interferes with the propagation of phages; and pRQ5, a 3.2-Md cryptic plasmid. Tetracycline resistance resides on a conjugative 120-MD plasmid pRQ1, belonging to the incompatibility class H2. Other antibiotic resistance determinants are encoded by a nonconjugative 108-Md plasmid pRQ2. Transfer of multiple-antibiotic resistance to appropriate recipient strains was associated with the appearance of a 230-Md plasmid, pRQ6. It appears that pRQ6 is a stable cointegrate of pRQ1 and pRQ2. This cointegrate plasmid was transferable with the same efficiency as pRQ1. Other conjugative plasmids could mobilize pRQ2, but stable cointegrates were not detected in the transconjugants. Phase type 201 strains carry a prophage, and we show that phage pattern 201 reflects the interference with propagation of typing phages effected by this prophage and plasmid pRQ4 in strains of phage type 201.

Anti-Bacterial Agents↗
PubMed1981

Virulence-associated plasmids from Yersinia enterocolitica and Yersinia pestis.

A 44-megadalton plasmid associated with virulence and Ca2+ dependence from Yersinia enterocolitica 8081 was compared at the molecular level with a 47-megadalton plasmid associated with Ca2+ dependence from Yersinia pestis EV76. The plasmids were found to share 55% deoxyribonucleic acid sequence homology distributed over approximately 80% of the plasmid genomes. One region in which the plasmids differed was found to contain sequences concerned with essential plasmid functions. Forty-five mutants of Y. pestis were isolated which had spontaneously acquired the ability to grow on calcium-free medium (Ca2+ independence). Of these mutants, 21 were cured of their 47-megadalton plasmid, whereas the remaining had either suffered a major deletion of the plasmid or had a 2.2-kilobase insertion located in one of two adjacent BamHI restriction fragments encompassing approximately 9 kilobases. The inserted sequence was found at numerous sites on the Y. pestis chromosome and on all three plasmids in the strain and may represent a Y. pestis insertion sequence element.

Base Sequence↗
PubMed1981

Use of agarose gel electrophoresis of plasmid deoxyribonucleic acid to fingerprint gram-negative bacilli.

Agarose gel electrophoresis of the plasmid deoxyribonucleic acids from 60 gram-negative bacilli recovered during investigations of nosocomial epidemics was used to fingerprint the strains. This method was as specific at differentiating bacterial strains as more conventional phenotyping methods. In all cases, plasmid band fingerprints of epidermic strains isolates were identical whereas coisolate plasmid deoxyribonucleic acid patterns were different. Agarose gel electrophoresis of plasmid deoxyribonucleic acid is proposed as a method which can be used in conventional microbiology laboratories as an adjunct to or, possibly, replacement for other methods of identifying bacterial strains.

Bacteria↗
PubMed1981

Molecular epidemiology of Haemophilus ducreyi infections.

Haemophilus ducreyi was isolated with an enriched chocolate agar containing vancomycin from seven patients with clinical evidence of chancroid. Four cases were imported from outside the United States; the other three cases were acquired in the United States from one of the imported cases. All strains of H. ducreyi contained ampicillin-resistance plasmids with molecular weights of 7.3, 5.7, or 3.6 megadaltons. Plasmid molecular weights were identical for isolates from the epidemiologically linked cases and differed according to the geographic origins of the strains. Findings of this study confirm that H. ducreyi is sexually transmitted and suggest that clinical chancroid develops frequently after acquisition of H. ducreyi.

Adult↗
PubMed1980

Amino acid sequence homology between cholera toxin and Escherichia coli heat-labile toxin.

Cholera toxin (CT) and the Escherichia coli heat-labile toxin (LT) are functionally, structurally and immunologically similar enterotoxins. Both toxins cause the elevation of cyclic AMP levels in gut epithelial cells by catalysing the NAD-dependent ADP ribosylation of membrane proteins. Each toxin is composed of two dissimilar subunits. The A subunit has an enzymatic activity and is the adenylate cyclase-activating component of the enterotoxin. The B subunit recognizes membrane components and binds the holotoxin to the target call juxtaposing the A subunit with its substrates. Binding studies and competition experiments indicate that the membrane receptors for cholera toxin B subunit (CT-B) and LT-B are similar but not identical (these studies were performed before by LT was purified to homogeneity). The monosialosylganglioside GMI has been shown to be the receptor for the cholera toxin, and it probably composes part of the receptor for LT. Gyles and Barnum, first reported that LT and cholera toxin were immunologically related, and it has subsequently been shown that they share common antigenic determinants in both A and B subunits. The primary structure of CT-B has been determined. We report here a comparison between the amino acid sequences of LT-B and CT-B. The nucleotide sequence of the LT-B cistron (eltB) was determined using a recombinant plasmid encoding LT. Translation of this sequence revealed that LT-B and CT-B show significant amino acid sequence homology. In addition, several features of the eltB cistron were revealed by the sequence analysis.

Amino Acid Sequence↗
PubMed1980

Molecular analysis of R-factors from multiresistant nosocomial isolates.

During an epidemic of infections at the Seattle Veterans Hospital, Washington, due to a multiresistant strain of Serratia marcencens, other enteric species were isolated that had antibiograms nearly identical to those of the epidemic S. marcescens. In 11 instances, these multiresistant species were isolated from specimens that also contained the epidemic serratia strain. All isolates of the epidemic serratia strain contained a conjugative 45-megadalton R-factor (pLST1000) coding for intermediate resistance to three amino-glycosides (minimal inhibitory concentrations, 4--8 micrograms/ml) and high-level resistance to ampicillin, carbenicillin, cephalothin, streptomycin, and sulfonamide. With the use of agarose gel electrophoresis and restriction endonuclease cleavage patterns after digestion with EcoRI, BamH1, and HindIII, it was determined that eight different enteric strains of six different species isolated from the patients contained an R-factor that was molecularly identical to the one isolated from the epidemic strain of S. marcescens. Thus, the epidemic of multiresistant infections at this hospital was caused both by the spread of an epidemic strain and an "epidemic plasmid." The molecular characteristics of pLST1000 appear to be different from previously described multiresistant plasmids.

Aminoglycosides↗
PubMed1980

Detection of enterotoxigenic Escherichia coli by DNA colony hybridization.

A method fo detecting large numbers of isolates of enterotoxigenic Escherichia coli is described in which the genes encoding th enterotoxins are detected, rather than the toxins themselves. Radiolabeled fragments of DNA encoding the heat-labile (LT) or heat-stable (ST) toxins were used as hybridization probes for homologous DNA sequences in E. coli colonies grown and lysed in situ on nitrocellulose filters. The LT probe detected all of 31 E. coli strains producing ST and LT or only LT, while the ST probe detected 12 of 17 strains producing only ST and three of 26 strains producing ST and LT. These results suggest that the LTs produced by different isolates of E. coli are homologous and that human isolates of E. coli produce at least two heterologous STs detectable in the infant mouse assay. The hybridization method also detected the presence of enterotoxigenic E. coli in bacterial growth in directly spotted stools from patients with acute diarrhea.

Acute Disease↗
PubMed1980

A taxonomic study of Gardnerella vaginalis (Haemophilus vaginalis) Gardner and Dukes 1955.

Fifty-five strains received as Haemophilus vaginalis or as catalase-negative coryneform bacteria from the vagina together with 61 marker cultures were subjected to numerical phenetic analyses using 149 unit characters. The data were examined using the simple matching (SSM), Jaccard (SJ) and pattern (DP) coefficients and clustering was achieved using the average linkage algorithm. Cluster composition was not markedly affected by the coefficient used or by test error, estimated at 6 . 5%. The H. vaginalis strains formed a tight cluster which was only distantly related to representatives of the genera arthrobacter, Cellulomonas, Corynebacterium sensu stricto, Erysipelothrix, Haemophilus, Kurthia, Lactobacillus, Listeria and Propionibacterium but shared a high overall affinity to unclassified catalase-negative coryneforms which formed a discrete taxon, cluster 9. The H. vaginalis strains could be distinguished from the related strains in cluster 9 by several unrelated phenotypic characters. Using the S1 endonuclease assay, DNA-DNA hybridizations were performed with representative strains from the numerical as well as with reference strains of Bifidobacterium and Actinomyces. Haemophilus vaginalis was found to be a genotypically legitimate group and its DNA showed little homology with DNA from the marker strains tested. The DNA base composition of H. vaginalis was 42 to 44 mol % guanine plus cytosine. A new genus should be created to incorporate strains known as H. vaginalis or Corynebacterium vaginale. The name Gardnerella vaginalis proposed by Greenwood & Pickett (1979) is supported.

Base Composition↗
PubMed1980

Genetic and molecular characteristics of Vir plasmids of bovine septicemic Escherichia coli.

Three wild strains of bovine septicemic Escherichia coli were selected on the basis of their production of a toxin lethal for mice and chickens and their characteristic surface antigen. The transfer of these virulence (Vir) properties from two of the three to recipient E. coli was detected after mating. One Vir plasmid (pJL1) was derepressed for transfer and associated with mobilization of chromosomal markers. The other, pJL2, was repressed. Both plasmids were tagged with transposon Tn5 (kanamycin resistance), and transfer parameters of the tagged plasmids were studied. The Tn5 insertion in pJL2 usually increased transfer efficiency 100-fold. Plasmid pJL1 was classified as a member of the FIV incompatibility group. A pJL1::Tn5 derivative plasmid was incompatible with ColV1. Plasmid pJL2 behaved as an fi+ plasmid. Both plasmids pJL1 and pJL2 had a molecular weight of 92 x 10(6) and were present at about four copies per chromosome; their deoxyribonucleic acid (DNA) structures were not identical on the basis of restriction enzyme analysis. DNA-DNA hybridization revealed a polynucleotide sequence homology of at least 58% between the two plasmids. No plasmids could be detected in one wild or certain laboratory-derived Vir+ E. coli strains.

Animals↗
PubMed1980

Nucleotide sequence homology between the heat-labile enterotoxin gene of Escherichia coli and Vibrio cholerae deoxyribonucleic acid.

Isolated deoxyribonucleic acid fragments encoding the heat-labile enterotoxin of Escherichia coli were used to probe for homologous sequences in restricted whole-cell deoxyribonucleic acid from Vibrio cholerae. Significant sequence homology between the heat-labile enterotoxin gene and V. cholerae deoxyribonucleic acid was demonstrated, and apparent differences were observed in the organization of the cholera toxin gene among different strains of V. cholerae.

Base Sequence↗