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Biomedical subjects

J R Johnson

Publications and source records attributed to J R Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1997

A surface swab method for culturing Foley catheters assays the pericatheter (urethral) but not the urine (luminal) microbial population.

Assessment of the urethral flora in patients with indwelling bladder catheters is problematic in the presence of urinary tract infection (UTI). A new surface swab method that samples the external catheter surface without interference from contaminated luminal contents is described. In vitro, recovery of adherent bacteria from the external catheter surface by the surface swab method was proportional to the bacterial density as measured by a comparison scrape method. In a prospective longitudinal assessment of three chronically catheterized subjects with polymicrobial catheter-associated UTI, a conventional roll plate catheter culture method suggested substantial overlap between the urethral and urine microbial populations, possibly a result of contamination of catheter cultures by infected urine. In contrast, the surface swab method revealed little overlap between these floras, evidence suggesting a predominantly luminal (rather than meatal) route of UTI acquisition. The new surface swab method should prove useful in future studies of the pathogenesis and prevention of catheter-associated UTI.

Bacteriological Techniques↗
PubMed1997

Discovery of disseminated J96-like strains of uropathogenic Escherichia coli O4:H5 containing genes for both PapG(J96) (class I) and PrsG(J96) (class III) Gal(alpha1-4)Gal-binding adhesins.

The pyelonephritis-associated adhesin gene papG of Escherichia coli occurs in three variants. Whereas the class II and class III variants are common among human urinary tract infection isolates, the class I allele, despite being the first cloned, has previously been found only in source strain J96. Five strains have been discovered from geographically diverse locales that, like J96, contain both the class I and class III papG alleles. One strain caused bacteremia, whereas 4 caused cystitis. Like J96, all 5 had group III capsule genes, expressed the H5 flagellar antigen and the F13 fimbrial antigen, and exhibited similar genomic patterns and virulence factor profiles. These findings demonstrate that the class I papG allele is not unique to J96 but is present in a group of extraintestinal isolates of E. coli O4:H5 that represent a disseminated virulent clonal group.

Adhesins, Escherichia coli↗
PubMed1997

Receptor specificities of variant Gal(alpha1-4)Gal-binding PapG adhesins of uropathogenic Escherichia coli as assessed by hemagglutination phenotypes.

Receptor specificities of the three recognized variants of PapG, the major adhesin of uropathogenic Escherichia coli, have been deduced in part from the distinctive hemagglutination (HA) patterns these adhesins ostensibly exhibit with different erythrocytes. A comprehensive reevaluation of these HA patterns using sheep, rabbit, and diverse human erythrocytes revealed that the erythrocyte binding ranges of the three PapG variants are broader and more overlapping than generally recognized, suggestive of receptor specificities beyond those posited in the prevailing model. Experiments involving guinea pig erythrocytes artificially labeled with defined Gal(alpha1-4)Gal-containing glycolipids supported this hypothesis and further suggested that HA patterns with naturally occurring erythrocytes cannot be used to determine reliably an adhesin's glycolipid binding specificities. Finally, slide HA assays exhibited considerable interexperiment, interobserver, and intraobserver irreproducibility, limiting their usefulness for assessing either the receptor specificities of PapG variants or the PapG repertoire of wild-type E. coli strains.

Adhesins, Escherichia coli↗
PubMed1997

Characteristics and prevalence within serogroup O4 of a J96-like clonal group of uropathogenic Escherichia coli O4:H5 containing the class I and class III alleles of papG.

The recent discovery of a geographically dispersed clonal group of Escherichia coli O4:H5 that includes prototypic uropathogenic strain J96 prompted us to determine the prevalence of J96-like strains within serogroup O4 and to further assess the characteristics of such strains. We used O:K:H;F serotyping, PCR-based genomic fingerprinting, pulsed-field gel electrophoresis (PFGE), multilocus enzyme electrophoresis (MLEE), and PCR detection of the three papG alleles and of the cytotoxic necrotizing factor 1 (cnf1) and aerobactin (aer) gene sequences to characterize the 15 O4 strains among 336 E. coli isolates from three clinical collections (187 from mixed-source bacteremia, 75 from urosepsis, and 74 from acute cystitis). J96-like strains constituted approximately half of the O4 strains, or 2% of the total population. In contrast to other O4 strains, the J96-like strains characteristically exhibited specific group III capsular antigens, the H5 flagellar and F13 fimbrial antigens, a distinctive PCR genomic fingerprint, the class III papG allele (plus, in 50% of strains, the enigmatic class I papG allele), and cnf1 but lacked aer. A subset of these strains was remarkably homogeneous with respect to all these characteristics and exhibited a distinctive PFGE fingerprint and MLEE pattern. These findings clarify the epidemiological relevance of J96 as a model extraintestinal pathogen, provide further evidence of the class I papG allele outside of strain J96, and offer insights into the evolution of E. coli serogroup O4.

Adhesins, Escherichia coli↗
PubMed1997

The MHSIP mental health report card. A consumer-oriented approach to monitoring the quality of mental health plans. Mental Health Statistics Improvement Program.

Health care report cards have been endorsed as a mechanism for efficiently comparing key quantifiable aspects of performance across a range of health systems or plans. There are challenges in determining what to measure; how to gather and analyze data; and how to report, interpret, and use findings. Mental health has received little attention, and a consumer perspective is typically not included. The proposed MHSIP mental health report card (MMHRC) addresses these concerns. General issues for report cards are discussed, and the MMHRC is described in terms of content, data sources and quality, and analysis and reporting.

Community Participation↗
PubMed1996

Management of iatrogenic spinal stenosis complicating placement of a fusion cage. A case report.

STUDY DESIGN: A case of iatrogenic spinal stenosis secondary to fusion cage retropulsion is presented. OBJECTIVES: To highlight fusion cage retropulsion, a potential complication that may become more prevalent as the use of fusion cage instrumentation expands. The difficulty in management of this complication is emphasized. SUMMARY OF BACKGROUND DATA: Early reports regarding fusion cage instrumentation have been encouraging. At this point, however, the potential benefits are better defined than the potential complications. METHODS: A significant complication of fusion cage instrumentation and the limited literature on this subject are reviewed. RESULTS: The patient underwent successful revision surgery after retropulsion of a fusion cage, however, an extensive surgical procedure including partial vertebral body resection was required. CONCLUSIONS: The frequency and severity of complications related to fusion cage instrumentation remain poorly defined. Caution should be used in patient selection until additional experience more clearly defines the risk-to-benefit ratio for a given application of this new technology.

Humans↗
PubMed1996

Salvage of instrumental lumbar fusions complicated by surgical wound infection.

STUDY DESIGN: This study retrospectively reviewed instrumented lumbar fusions complicated by surgical wound infection and managed by a protocol including antibiotic impregnated beads. OBJECTIVE: To evaluate the potential for an acceptable clinical outcome in cases of instrumented lumbar fusion complicated by wound infection. SUMMARY OF BACKGROUND DATA: Initial studies of pedicle screw instrumentation suggested an increased infection rate versus noninstrumented fusion. The presence of a metallic implant also complicates wound management. METHODS: Eight hundred fifty-eight instrumented fusions were reviewed with 22 (2.6%) deep wound infections identified. Analysis included preoperative risk factors, surgical procedure, postoperative course, and clinical outcome. RESULTS: Nineteen patients (mean age, 55 years) were reviewed at a minimum of 1 year after surgery. Sixteen (83%) reported significant preoperative health problems. Forty-seven percent of the patients had three- and four-level fusions. Mean operative time was 342 minutes. Mean estimated blood loss was 1620 mL. Infection was diagnosed at an average of 16 days after surgery with wound drainage as the most common presenting feature. Patients underwent between two and 10 (mean, 4.7) irrigation procedures. Seven patients had other significant noninfectious complications. At follow-up evaluation, no patient had recurrence of infection. By comparison to preoperative symptoms, 15 patients were improved, three were unchanged, and one deteriorated. Fusion was apparently solid in 14 patients, probable in four patients, and nonunion occurred in one patient. CONCLUSION: Although wound infection is a significant complication, this study suggests that aggressive surgical management can result in preservation of an adequate fusion rate and maintenance of an acceptable postoperative outcome.

Adult↗
PubMed1996

Prevotella intermedia and Prevotella nigrescens serotypes, ribotypes and binding characteristics.

Type strains and 62 clinical isolates of Prevotella intermedia and Prevotella nigrescens were typed with the use of genomic DNA fingerprints and rRNA gene probes. The strains were further serotyped with monoclonal antibodies and characterized with SDS-PAGE, enzymatic activities, hemolysis and hemagglutination and coaggregation with Streptococcus and Actinomyces spp. P. intermedia and P. nigrescens were found to have distinct ribotype patterns which correspond to previously defined serotyupes I and II/III, respectively. No clear phenotypic difference related to hemolysis, hemagglutination and coaggregation with streptococcus and actinomyces species, or expression of aminopeptides and lipase was found between P. intermedia and P. migrescens.

Animals↗
PubMed1996

Radical improvements in the display of clinical microbiology results: a Web-based clinical information system.

OBJECTIVE: To evaluate the performance of a novel computerized system for reporting clinical microbiology results. The new system provides a summarized overview of a patient's current (or past) microbiological status, with the option to selectively explore in greater depth. It is deployed using World Wide Web technology, which supports virtually any kind of computer and allows physicians to obtain results via the internet using personal computers in the office or at home. METHODS: In an unblinded crossover study at a university-affiliated medical center, participants used both the new system and a conventional display system to retrieve selected microbiology results for two actual patients, according to standardized questionnaires, with balanced allocation of sequence of system use. Participants also subjectively rated the two systems. The participants were 16 physician, pharmacist, and nurse volunteers. Outcome measures included completion time and number of errors (categorized as major and minor) associated with results retrieval, and participants' ratings of the new system. RESULTS: Mean completion time was 45% shorter (13.9 versus 25.5 minutes; P < 0.001), and there were fewer associated major errors (0 versus 13; P = 0.01) and minor errors (10 versus 21; P = 0.003) with the summarized display system. All participants rated the new system as easier to learn and use than the conventional system. CONCLUSIONS: A system that appropriately summarizes and groups microbiology results can significantly shorten retrieval times and reduce interpretive errors, while providing users with information needed for cost-effective therapy. Such a system can be deployed by leveraging the rapidly evolving technology of the World Wide Web.

Academic Medical Centers↗
PubMed1996

Identification of two previously unrecognized genes (guaA and argC) important for uropathogenesis.

Our knowledge of the traits possessed by extraintestinal isolates of Escherichia coli, necessary for growth and survival in urine, is limited. To identify such determinants, transposon (TnphoA'1,4) mutant libraries of a clinical isolate (CP9) were generated and screened for derivatives exhibiting decreased growth in urine in vitro, and for mutants with active lacZ fusions that were induced in urine relative to laboratory medium. Using this approach we identified two genes, guaA (CPA24) and argC (CPI-1), which were previously unrecognized as being important for growth in human urine. Unexpectedly, not only does CPA24 (guaA) not grow in human urine in vitro, but it is sensitive to its effects, undergoing a 2-3 log loss of viability over 6 h. By contrast, CPA24 neither grows nor is killed in M9 minimal medium and artificial urine. Therefore, we postulate that lack of guanine or its derivatives in urine, and the inability of CPA24 to synthesize these compounds de novo, prevents CPA24 from synthesizing other guanine (or derivatives)-dependent products that are critical for growth and survival in urine. Although it seems logical that decreased growth in urine in vitro should correlate with diminished urovirulence, this concept was tested by challenging mice with CPA24 in vivo in a mouse model of urinary tract infection (UTI). Indeed, CPA24 was found to be significantly less virulent compared with its wild-type parent CP9. CPI-1(argC) was identified because of the significant induction of its argC::lacZ fusion in urine. Subsequent testing in urine demonstrated that its growth was significantly diminished in all urine samples tested (four females, three males). Polyamine synthesis is dependent upon, in part, the arginine biosynthetic pathway. Therefore, we tested whether the induction of argC in urine and/or the decreased growth of CPI-1 was a result of low levels of polyamines or arginine in urine. The results suggest that low levels of arginine, but not polyamines, in human urine are responsible. When tested in vivo in the mouse model of UTI, CPI-1 was also found to be significantly less virulent than CP9. In summary, we have established that guaA and argC are the first genes, which we are aware of, that have been shown to contribute to the growth of E. coli in urine in vitro and both have diminished urovirulence in vivo. These results support the concept that urine can be used in vitro as a screening tool to identify urovirulence traits.

Aldehyde Oxidoreductases↗
PubMed1996

Defining inoculation conditions for the mouse model of ascending urinary tract infection that avoid immediate vesicoureteral reflux yet produce renal and bladder infection.

A satisfactory mouse model of ascending urinary tract infection (UTI) must avoid inoculation-induced vesicoureteral reflex (VUR) yet still produce kidney and bladder infection in a substantial proportion of mice. To define inoculation conditions that would satisfy both these conditions, mice were evaluated for VUR immediately after inoculation under a variety of conditions and were assessed for kidney and bladder infection 48 h after inoculation. Elimination of VUR required a slowed infusion rate, a reduced inoculum volume (25 microliter), and use of less traumatic methods for euthanasia and organ harvest. Bladder and kidney infection were highly prevalent at 48 h among mice inoculated under VUR-free conditions with either of 2 wild type Escherichia coli strains. Together with reports from other investigators, these findings indicate that satisfactory experimental conditions for the mouse model of ascending UTI can be defined empirically but may be laboratory-specific.

Animals↗
PubMed1996

A novel multiply primed polymerase chain reaction assay for identification of variant papG genes encoding the Gal(alpha 1-4)Gal-binding PapG adhesins of Escherichia coli.

A more convenient assay is needed for the three recognized allelic variants of papG, which encode the Gal(alpha 1-4)Gal-binding adhesin molecules of P fimbriae of uropathogenic Escherichia coli. The development and validation of a novel multiply primed polymerase chain reaction (PCR) assay is described. The assay was 100% sensitive and specific for the three papG variants, whether present individually or in any combination. PCR products specific for the "class I" (papGJ96), "class II" (papGIA2), and "class III" (prsGJ96) alleles of papG could be resolved by size in the same lane using agarose gel electrophoresis after simultaneous amplification in a single tube by multiply primed PCR. This new papG PCR assay should aid future molecular epidemiologic studies that assess the contribution of the three variants of papG to the pathogenesis of urinary tract infection.

Adhesins, Escherichia coli↗
PubMed1996

The O4 specific antigen moiety of lipopolysaccharide but not the K54 group 2 capsule is important for urovirulence of an extraintestinal isolate of Escherichia coli.

Group 2 capsules and lipopolysaccharides are regarded as important virulence factors in extraintestinal isolates of Escherichia coli, but their specific contributions to bladder and renal infections, if any, are unknown. Proven isogenic derivatives deficient in the K54 antigen alone (CP9.137), the O4 antigen alone (CP921), or both the K54 and O4 antigens (CP923) were compared with their wild-type parent (CP9 [O4/K54JH5]) for growth in human urine in vitro and for virulence in vivo in a mouse model of ascending urinary tract infection (UTI). Growth of CP9.137 and CP921 was equivalent to that of CP9 in human urine. CP923 demonstrated a small but reproducible decrease in log-phase growth but achieved the same plateau density. In the mouse model of UTI, the isogenic mutant deficient in the 04 antigen alone (CP921) and, to a greater degree, the derivative deficient in both the K54 and O4 antigens (CP923) were significantly less virulent in nearly all parameters measured. In contrast, the K54 knockout derivative was as virulent as its parent, CP9, in causing bladder infection and nearly as virulent in causing renal infection. These results demonstrate an important role for the O4 antigen moiety of lipopolysaccharide in the pathogenesis of UTI. The possibility that the K54 antigen also plays a minor role cannot be excluded.

Animals↗