Biomedical subjects

S M Payne

Publications and source records attributed to S M Payne.

At least 37 records · Page 2Linked to original sources

PubMed1999

Comparison of the heme iron utilization systems of pathogenic Vibrios.

Vibrio alginolyticus, Vibrio fluvialis, and Vibrio parahaemolyticus utilized heme and hemoglobin as iron sources and contained chromosomal DNA similar to several Vibrio cholerae heme iron utilization genes. A V. parahaemolyticus gene that performed the function of V. cholerae hutA was isolated. A portion of the tonB1 locus of V. parahaemolyticus was sequenced and found to encode proteins similar in amino acid sequence to V. cholerae HutW, TonB1, and ExbB1. A recombinant plasmid containing the V. cholerae tonB1 and exbB1D1 genes complemented a V. alginolyticus heme utilization mutant. These data suggest that the heme iron utilization systems of the pathogenic vibrios tested, particularly V. parahaemolyticus and V. alginolyticus, are similar at the DNA level, the functional level, and, in the case of V. parahaemolyticus, the amino acid sequence or protein level to that of V. cholerae.

Bacterial Proteins↗

PubMed1999

A multifunctional ATP-binding cassette transporter system from Vibrio cholerae transports vibriobactin and enterobactin.

Vibrio cholerae uses the catechol siderophore vibriobactin for iron transport under iron-limiting conditions. We have identified genes for vibriobactin transport and mapped them within the vibriobactin biosynthetic gene cluster. Within this genetic region we have identified four genes, viuP, viuD, viuG and viuC, whose protein products have homology to the periplasmic binding protein, the two integral cytoplasmic membrane proteins, and the ATPase component, respectively, of other iron transport systems. The amino-terminal region of ViuP has homology to a lipoprotein signal sequence, and ViuP could be labeled with [(3)H]palmitic acid. This suggests that ViuP is a membrane lipoprotein. The ViuPDGC system transports both vibriobactin and enterobactin in Escherichia coli. In the same assay, the E. coli enterobactin transport system, FepBDGC, allowed the utilization of enterobactin but not vibriobactin. Although the entire viuPDGC system could complement mutations in fepB, fepD, fepG, or fepC, only viuC was able to independently complement the corresponding fep mutation. This indicates that these proteins usually function as a complex. V. cholerae strains carrying a mutation in viuP or in viuG were constructed by marker exchange. These mutations reduced, but did not completely eliminate, vibriobactin utilization. This suggests that V. cholerae contains genes in addition to viuPDGC that function in the transport of catechol siderophores.

ATP-Binding Cassette Transporters↗

PubMed1998

Structure of the Shigella dysenteriae haem transport locus and its phylogenetic distribution in enteric bacteria.

The ability to transport and use haemin as an iron source is frequently observed in clinical isolates of Shigella spp. and pathogenic Escherichia coli. We found that many of these haem-utilizing E. coli strains contain a gene that hybridizes at high stringency to the S. dysenteriae type 1 haem receptor gene, shuA. These shuA-positive strains belong to multiple phylogenetic groups and include clinical isolates from enteric, urinary tract and systemic infections. The distribution of shuA in these strains suggests horizontal transfer of the haem transport locus. Some haem-utilizing pathogenic E. coli strains did not hybridize with shuA, so at least one other haem transport system is present in this group. We also characterized the chromosomal region containing shuA in S. dysenteriae. The shuA gene is present in a discrete locus, designated the haem transport locus, containing eight open reading frames. Several of the proteins encoded in this locus participate with ShuA in haem transport, as a Salmonella typhimurium strain containing the entire haem transport locus used haem much more efficiently than the same strain containing only shuA. The haem transport locus is not present in E. coli K-12 strains, but the sequences flanking the haem transport locus in S. dysenteriae matched those at the 78.7 minute region of E. coli K-12. The junctions and flanking sequences in the shuA-positive pathogenic E. coli strains tested were nearly identical to those in S. dysenteriae, indicating that, in these strains, the haem transport locus has an organization similar to that in S. dysenteriae, and it is located in the same relative position on the chromosome.

Bacterial Outer Membrane Proteins↗

PubMed1998

Vibrio cholerae iron transport: haem transport genes are linked to one of two sets of tonB, exbB, exbD genes.

Vibrio cholerae was found to have two sets of genes encoding TonB, ExbB and ExbD proteins. The first set (tonB1, exbB1, exbD1) was obtained by complementation of a V. cholerae tonB mutant. In the mutant, a plasmid containing these genes permitted transport via the known V. cholerae high-affinity iron transport systems, including uptake of haem, vibriobactin and ferrichrome. When chromosomal mutations in exbB1 or exbD1 were introduced into a wild-type V. cholerae background, no defect in iron transport was noted, indicating the existence of additional genes that can complement the defect in the wild-type background. Another region of the V. cholerae chromosome was cloned that encoded a second functional TonB/Exb system (tonB2, exbB2, exbD2). A chromosomal mutation in exbB2 also failed to exhibit a defect in iron transport, but a V. cholerae strain that had chromosomal mutations in both the exbB1 and exbB2 genes displayed a mutant phenotype similar to that of an Escherichia coli tonB mutant. The genes encoding TonB1, ExbB1, ExbD1 were part of an operon that included three haem transport genes (hutBCD), and all six genes appeared to be expressed from a single Fur-regulated promoter upstream of tonB1. A plasmid containing all six genes permitted utilization of haem by an E. coli strain expressing the V. cholerae haem receptor, HutA. Analysis of the hut genes indicated that hutBCD, which are predicted to encode a periplasmic binding protein (HutB) and cytoplasmic membrane permease (HutC and HutD), were required to reconstitute the V. cholerae haem transport system in E. coli. In V. cholerae, the presence of hutBCD stimulated growth when haemin was the iron source, but these genes were not essential for haemin utilization in V. cholerae.

Amino Acid Sequence↗

PubMed1998

Determinants of home health visit length: results of a multisite prospective study.

OBJECTIVES: The authors (1) compare visit length across four categories of skilled nursing home health visits which reflect recent changes in home health casemix-AIDS-related, hospice/terminal (HT), intravenous (IV) therapy, and maternal and child health (MCH)-with general adult medical/surgical (MS) visits and (2) identify factors influencing visit length. METHODS: The study sites were 12 nonproprietary Massachusetts home health agencies (HHAs). Staff nurses collected data concurrently on a sample of visits they provided between December 1, 1992 and November 30, 1993. The visits were stratified by agency, time of year, and visit category. The authors used analysis of variance to test for significant differences across visit categories in Home Length of Visit (the number of minutes between when the nurse entered and left the home) (HLOV). The authors used multivariate regression analysis to develop models identifying determinants of HLOV and adjusted R2 to measure the explanatory power of partial models. RESULTS: In univariate analysis, the categories differed significantly from each other in length (P < 0.0001). HT visits were the longest (median visit length = 60, 80, and 59 minutes for HT Only visits, visits in both the HT and AIDS categories (HT/AIDS), and HT/IV visits, respectively). MS visits were the shortest (median = 30 minutes). The remaining categories were intermediate in length (medians = 37 to 50 minutes). Almost half the variability in HLOV was explained by the full multivariate regression model, which includes all independent variables (adjusted R2 = .4486; P < 0.0001). Visit characteristics alone in a partial model explained 18% of the variability in HLOV. Three other variable sub-groups-agency, client characteristics, and nursing workload-each explained about 15% of the variability in HLOV. Nursing activities performed during the visit explained 11%; several of these related to teaching, education, or assessment. CONCLUSIONS: Accurate reimbursement reflecting casemix differences is important to protect the teaching, education, and assessment functions of nurses; measure nurse productivity and allocate caseloads; maintain access to services for clients with greater needs; and avoid creating economic disincentives to the agencies that serve them. Payers formulating prospective payment systems can adjust per visit reimbursement rates to reflect differences in visit length by category and incorporate functional limitations, clinical instability, and case coordination as classification variables. Developers of home health casemix systems can use factor analysis to improve the robustness of multivariate models and include nursing workload in predicting visit length. Home health agencies measuring productivity and caseload across complex client populations can classify visits into three groups-MS; HT; and AIDS, IV, and MCH-or use the regression results to develop more refined predictors of visit length and nursing caseload.

Adult↗

PubMed1998

Identification of two Shigella flexneri chromosomal loci involved in intercellular spreading.

The ability of Shigella flexneri to multiply within colonic epithelial cells and spread to adjacent cells is essential for production of dysentery. Two S. flexneri chromosomal loci that are required for these processes were identified by screening a pool of TnphoA insertion mutants. These mutants were able to invade cultured epithelial cells but could not form wild-type plaques. Analysis of the nucleotide sequence indicated that the sites of TnphoA insertion were within two different regions that are almost identical to Escherichia coli K-12 chromosomal sequences of unknown functions. One region is located at 70 min on the E. coli chromosome, upstream of murZ, while the other is at 28 min, downstream of tonB. The mutant with the insertion at 70 min was named vpsC because it showed an altered pattern of virulence protein secretion. The vpsC mutant formed pinpoint-sized plaques, was defective in recovery from infected tissue culture cells, and was sensitive to lysis by the detergent sodium dodecyl sulfate. Recombinant plasmids carrying the S. flexneri vpsA, -B, and -C genes complemented all of the phenotypes of the vpsC mutant. A mutation in vpsA resulted in the same phenotype as the vpsC mutation, suggesting that these two genes are part of a virulence operon in S. flexneri. The mutant with the insertion at 28 min was interrupted in the same open reading frame as S. flexneri ispA. This ispA mutant could not form plaques and was defective in bacterial septation inside tissue culture cells.

Bacterial Proteins↗

PubMed1998

Home alone: unmet need for formal support services among home health clients.

In order to remain in the home without family or other informal support, home health clients must have access to essential formal services such as nutritional support and homemaking chores to supplement medical and nursing care. In this study, we looked at client-related factors associated with the need for formal support services, and factors associated with whether those needs are adequately met. Data were collected from 2,013 home health clients in Massachusetts. According to the assessment of the skilled nurses treating them, 85 percent of the clients needed one or more support services; some or all needs were not adequately met in nearly half. Significant factors contributing to unmet need included: being non-white, having Medicaid as payer, being in a health maintenance organization, having AIDS, receiving maternal/child health services, and having an acute condition. This research suggests that even clients receiving skilled nursing care may not have many or most of their supportive needs met, and that there are identifiable factors which decrease the likelihood of having adequate care provided.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Genetic analysis of experimentally induced lupus in mice.

The DBA/2 and C57BL/6 mouse strains, as well as the BXD RI lines derived from these strains, were used to map the genes controlling experimentally induced systemic lupus erythematosus (SLE). SLE was induced using two immunologic approaches: (1) immunization with the human monoclonal anti-DNA antibody expressing the 16/6Id, to which the DBA/2 strain is susceptible (responder) and the C57BL/6 strain is resistant (nonresponder); and (2) induction of autoimmune GVHD in B6D2F1 hosts by inoculation of parental DBA/2 (induces SLE) or C57BL/6 (does not induce SLE) T cells. By both approaches the BXD RI lines could be divided into distinct DBA/2-like and C57BL/6-like categories. Concordance of SLE induced by both methods was observed for susceptibility and resistance in 13/15 BXD lines (P < 0.005). The results suggest that at least two non-H-2 genes control susceptibility and resistance to experimentally induced SLE, one mapping to chromosome 7 and the other mapping to chromosome 14.

Animals↗

PubMed1997

Haem iron-transport system in enterohaemorrhagic Escherichia coli O157:H7.

In this study, we identified the iron-transport systems of Escherichia coli O157:H7 strain EDL933. This strain synthesized and transported enterobactin and had a ferric citrate transport system but lacked the ability to produce or use aerobactin. It used haem and haemoglobin, but not transferrin or lactoferrin, as iron sources. We cloned the gene encoding an iron-regulated haem-transport protein and showed that this E. coli haem-utilization gene (chuA) encoded a 69 kDa outer membrane protein that was synthesized in response to iron limitation. Expression of this protein in a laboratory strain of E. coli was sufficient for utilization of haem or haemoglobin as iron sources. Mutation of the chromosomal chuA and tonB genes in E. coli O157:H7 demonstrated that the utilization of haemin and haemoglobin was ChuA- and TonB-dependent. Nucleotide sequence analysis of chuA revealed features characteristic of TonB-dependent, Fur-regulated, outer membrane iron-transport proteins. It was highly homologous to the shuA gene of Shigella dysenteriae and less closely related to hemR of Yersinia enterocolitica and hmuR of Yersinia pestis. A conserved Fur box was identified upstream of the chuA gene, and regulation by Fur was confirmed.

Bacterial Outer Membrane Proteins↗

PubMed1997

Effect of mutations in Shigella flexneri chromosomal and plasmid-encoded lipopolysaccharide genes on invasion and serum resistance.

This study shows that both length and distribution of lipopolysaccharide (LPS) are important for Shigella flexneri invasion and virulence. Mutants were generated in the chromosomal LPS synthesis genes rfa, rfb, and rol, and in a plasmid-encoded O-antigen chain-length regulator, cld(pHS-2). LPS analysis showed that mutations in rfb genes and in a candidate rfaL gene either eliminated the entire O-antigen side chains or produced chains of greatly reduced length. Mutation in a previously unidentified gene, rfaX, affected the LPS core region and resulted in reduced amounts of O-antigen. Mutants defective in cld(pHS-2) or rol had different distributions of O-antigen chain lengths. The results of tissue-culture cell invasion and plaque assays, the Serény test, and serum-sensitivity assay suggested roles for the different LPS synthesis genes in bacterial survival and virulence; rfaL, rfaX and rfb loci are required for serum resistance and intercellular spread, but not for invasion; cld(pHS-2) is required for resistance to serum killing and for full inflammation in the Serény test, but not for invasion or intercellular spread, while rol is required for normal invasiveness and plaque formation, but not for serum resistance. Thus, O-antigen synthesis and chain-length regulation genes encoded on both the chromosome and the small plasmid pHS-2 play important roles in S. flexneri invasion and virulence.

Animals↗

PubMed1997

Identification of shuA, the gene encoding the heme receptor of Shigella dysenteriae, and analysis of invasion and intracellular multiplication of a shuA mutant.

shuA encodes a 70-kDa outer membrane heme receptor in Shigella dysenteriae. Analysis of the shuA DNA sequence indicates that this gene encodes a protein with homology to TonB-dependent receptors of gram-negative bacteria. Transport of heme by the ShuA protein requires TonB and its accessory proteins ExbB and ExbD. The shuA DNA sequence contains a putative Fur box overlapping the -10 region of a potential shuA promoter, and the expression of shuA is repressed by exogenous iron or hemin in a Fur-dependent manner, although hemin repressed expression to a lesser extent than iron salts. Disruption of this open reading frame on the S. dysenteriae chromosome by marker exchange yielded a strain that failed to use heme as an iron source, indicating that shuA is essential for heme transport in S. dysenteriae. However, shuA is not essential for invasion or multiplication within cultured Henle cells; the shuA mutant invaded and produced normal plaques in confluent cell monolayers.

Amino Acid Sequence↗

PubMed1997

Expression of aerobactin genes by Shigella flexneri during extracellular and intracellular growth.

The expression of the Shigella flexneri chromosomal aerobactin genes during growth of the bacterium within tissue culture cells was assayed. During intracellular growth, aerobactin promoter activity was repressed relative to the level observed in bacteria grown extracellularly, even when the bacteria had been starved for iron prior to infection. Similarly, the level of one of the proteins encoded by this operon, the aerobactin outer membrane receptor, Iut, was reduced in the intracellular environment. These studies indicate that the aerobactin system is not highly expressed by bacteria within host cells, suggesting that siderophore-independent iron acquisition systems can provide essential iron during intracellular multiplication.

Extracellular Space↗

PubMed1997

Cloning of a Vibrio cholerae vibriobactin gene cluster: identification of genes required for early steps in siderophore biosynthesis.

Vibrio cholerae secretes the catechol siderophore vibriobactin in response to iron limitation. Vibriobactin is structurally similar to enterobactin, the siderophore produced by Escherichia coli, and both organisms produce 2,3-dihydroxybenzoic acid (DHBA) as an intermediate in siderophore biosynthesis. To isolate and characterize V. cholerae genes involved in vibriobactin biosynthesis, we constructed a genomic cosmid bank of V. cholerae DNA and isolated clones that complemented mutations in E. coli enterobactin biosynthesis genes. V. cholerae homologs of entA, entB, entC, entD, and entE were identified on overlapping cosmid clones. Our data indicate that the vibriobactin genes are clustered, like the E. coli enterobactin genes, but the organization of the genes within these clusters is different. In this paper, we present the organization and sequences of genes involved in the synthesis and activation of DHBA. In addition, a V. cholerae strain with a chromosomal mutation in vibA was constructed by marker exchange. This strain was unable to produce vibriobactin or DHBA, confirming that in V. cholerae VibA catalyzes an early step in vibriobactin biosynthesis.

Catechols↗

PubMed1996

Amelioration of experimental systemic lupus erythematosus (SLE) by retrovirus infection.

Experimental SLE can be induced in susceptible 129/J mice by immunization with a human anti-DNA antibody bearing a common idiotype designated 16/6 Id. Immunized mice develop autoantibodies, leukopenia, proteinuria, and immune complex deposits in renal glomeruli. Case reports have described clinical improvement in SLE in individuals becoming infected with HIV-1. Because 129/J mice are susceptible to experimental SLE and to infection with the BM5def murine leukemia virus (MuLV) mixture but do not develop the lymphoproliferative/ immunodeficiency disorder known as murine AIDS (MAIDS), we superimposed this infection on immunization with the 16/6 Id. Multiple effects were observed. First, we noted an amelioration in the course of experimental SLE. Second, both in experimental SLE and in BM5def MuLV infection, immunoreactivity to HIV-1 gp120 was demonstrated, although gp120 is not present in the BM5def MuLV viruses. Third, production of autoantibodies characteristically found in SLE, e.g., anti-DNA, anti-RNP, and anti-SSA, was seen in BM5def MuLV-infected mice, demonstrating that an immune response as a consequence of infection had occurred despite the absence of MAIDS induction. We conclude that (1) retrovirus inoculation may ameliorate the course of experimental SLE; and (2) retrovirus inoculation, even in the absence of MAIDS induction, induces an immunologic response which promotes the production of potentially pathogenic autoantibodies.

Animals↗

PubMed1995

Variations in pediatric pneumonia and bronchitis/asthma admission rates. Is appropriateness a factor?

OBJECTIVE: To explore through a pilot study the relationship between appropriateness (medical necessity) and variations in pediatric hospital admission rates across several communities in the Boston (Mass) area for two common pediatric conditions with extremely variable admission rates: pneumonia and bronchitis/asthma. DESIGN: We identified five communities in the greater Boston area with high, average, and below-average ratios of observed to expected admissions for the study conditions. Diagnosis-specific, criteria-based utilization review instruments were developed by community-based pediatricians and applied by trained nurse reviewers to medical records. ADMISSIONS STUDIED: All admissions for pneumonia (diagnosis related group [DRG] 91) and bronchitis/asthma (DRG 98) of study area residents younger than 18 years to participating hospitals during fiscal year 1986. OUTCOME MEASURES: For each area, we calculated age-adjusted admission rates, age-adjusted observed to expected ratios, and rates of inappropriate admissions. We tested the hypothesis that admission rates and inappropriateness rates were directly related. RESULTS: We deemed 9.4% of pneumonia admissions and 4.4% of bronchitis/asthma admissions inappropriate. Rates of inappropriate admissions were not significantly associated with admission rates in this local pilot study for either study condition at P < .05. However, in one community both rates were high for both conditions. Feedback of findings to the key local hospital there resulted in sharp decreases in admission rates for DRGs 91 and 98 in subsequent years. CONCLUSIONS: Our results suggest that higher pediatric admission rates may not be associated with higher rates of inappropriateness. Further research is needed, with a larger number of communities, to differentiate practice patterns more precisely and explore patient and family preferences.

Adolescent↗

PubMed1995

Using administratively collected hospital discharge data for AIDS surveillance.

The objectives of this study were twofold: to improve methods of identifying possible and acquired immunodeficiency syndrome (AIDS)-related hospital discharges in administrative databases and to measure AIDS-reporting completeness in Massachusetts both overall and by subgroup. We used fiscal year 1988 discharge data from the Massachusetts Rate Setting Commission (RSC) and data from the Massachusetts AIDS Reporting System (ARS). We identified 3362 discharges of adult patients (> 12 years old) from the RSC file that had diagnosis codes which are human immunodeficiency virus (HIV)-specific (042.x, 043.x, 044.x, or 795.8) or pertain to AIDS-defining "manifestations." Medical records of 650 patients apparently not reported to the ARS were reviewed. THe best set of codes overall consisted of either (a) the 042.x code or (b) the 043.x, 044.x, or 795.8 code plus selected manifestation codes (sensitivity, 93%; specificity, 86%; predictive value positive, 71%). Of the 927 AIDS cases identified from the 3362 discharges, only 36 had not been reported. AIDS cases among women (odds ratio (OR) = 2.9; 95% confidence interval (CI): 1.33 to 6.33), intravenous drug users (OR = 4.2; 95% CI: 2.20 to 8.02), and persons residing outside the Boston metropolitan area (OR = 2.3; 95% CI: 1.18 to 4.57) were more likely to be unreported than those among comparison groups.

AIDS-Related Opportunistic Infections↗

PubMed1995

Increased protein secretion and adherence to HeLa cells by Shigella spp. following growth in the presence of bile salts.

Growth of Shigella spp. in the presence of the bile salt deoxycholate or chenodeoxycholate enhanced the bacterial invasion of HeLa cells. Growth in the presence of other structurally similar bile salts or detergents had little or no effect. Deoxycholate-enhanced invasion was not observed when bacteria were exposed to deoxycholate at low temperatures or when chloramphenicol was added to the growth medium, indicating that bacterial growth and protein synthesis are required. Increased invasion is associated with the presence of an intact Shigella virulence plasmid and is correlated with increased secretion of a set of proteins, including the Ipa proteins, to the outer membrane and into the growth medium. The increased invasion induced by the bile salts appears to be due to increased adherence. The enhanced adherence was specific to Shigella spp., since the enteroinvasive Escherichia coli strains tested did not exhibit the effect in response to growth in bile salts.

Adhesins, Bacterial↗

PubMed1995

Genetics and regulation of heme iron transport in Shigella dysenteriae and detection of an analogous system in Escherichia coli O157:H7.

Shigella species can use heme as the sole source of iron. In this work, the heme utilization locus of Shigella dysenteriae was cloned and characterized. A cosmid bank of S. dysenteriae serotype 1 DNA was constructed in an Escherichia coli siderophore synthesis mutant incapable of heme transport. A recombinant clone, pSHU12, carrying the heme utilization system of S. dysenteriae was isolated by screening on iron-poor medium supplemented with hemin. Transposon insertional mutagenesis and subcloning identified the region of DNA in pSHU12 responsible for the phenotype of heme utilization. Minicell analysis indicated that a 70-kDa protein encoded by this region was sufficient to allow heme utilization in E. coli. Synthesis of this protein, designated Shu (Shigella heme uptake), was induced by iron limitation. The 70-kDa protein is located in the outer membrane and binds heme, suggesting it is the S. dysenteriae heme receptor. Heme iron uptake was found to be TonB dependent in E. coli. Transformation of an E. coli hemA mutant with the heme utilization subclone, pSHU262, showed that heme could serve as a source of porphyrin as well as iron, indicating that the entire heme molecule is transported into the bacterial cell. DNA sequences homologous to shu were detected in strains of S. dysenteriae serotype 1 and E. coli O157:H7.

Bacterial Proteins↗