Type 3 secretion system effector genotype and secretion phenotype of longitudinally collected Pseudomonas aeruginosa isolates from young children diagnosed with cystic fibrosis following newborn screening

Studies of the type 3 secretion system (T3SS) in Pseudomonas aeruginosa isolates from chronically infected older children and adults with cystic fibrosis (CF) show a predominantly exoS+/exoU- (exoS+) genotype and loss of T3SS effector secretion over time. Relatively little is known about the role of the T3SS in the pathogenesis of early P. aeruginosa infection in the CF airway. In this longitudinal study, 168 P. aeruginosa isolates from 58 children diagnosed with CF following newborn screening and 47 isolates from homes of families with or without children with CF were genotyped by pulsed-field gel electrophoresis (PFGE) and T3SS genotype and phenotype determined using multiplex PCR and western blotting. Associations were sought between T3SS data and clinical variables and comparisons made between T3SS data of clinical and environmental PFGE genotypes. Seventy-seven of the 92 clinical strains were exoS+ (71% secretors (ExoS+)) and 15 were exoU+ (93% secretors (ExoU+)). Initial exoS+ strains were five times more likely to secrete ExoS than subsequent exoS+ strains at first isolation. The proportion of ExoS+ strains declined with increasing age at acquisition. No associations were found between T3SS characteristics and gender, site of isolation, exacerbation, a persistent strain or pulmonary outcomes. Fourteen of the 23 environmental strains were exoS+ (79% ExoS+) and nine were exoU+ (33% ExoU+). The exoU+ environmental strains were significantly less likely to secrete ExoU than clinical strains. This study provides new insight into the T3SS characteristics of P. aeruginosa isolated from the CF airway early in life.

Transcriptional regulation ofSalmonella entericaserovar Typhimurium genes by bile

DNA microarrays and two-dimensional (2-D) gel electrophoresis were utilized to analyze the global effect of bile on transcription and protein synthesis in Salmonella enterica serovar Typhimurium. Two bile-regulated proteins, YciF and PagC, were identified by 2-D gel electrophoresis and mass spectrometry fingerprinting. The operon yciGFE-katN demonstrated increased transcriptional activity in the presence of bile. While this operon has previously been shown to be RpoS-regulated, data from this study suggested that yciGFE-katN is regulated by bile independent of RpoS. The PhoP-PhoQ-regulated PagC is decreased in the presence of bile. Characterization of the untranslated leader of pagC demonstrated that a 97-bp region is necessary for the bile-mediated repression of this promoter. Analysis of data from the DNA microarray revealed an effect of bile on important global mechanistic pathways in S. enterica serovar Typhimurium. Genes involved in type III secretion-mediated invasion of epithelial cells demonstrated an overall repression of transcription in the presence of bile, corroborating previously reported data from this laboratory [Infect. Immun. 68 (2000) 6763]. In addition, bile-mediated transcriptional repression of genes involved in flagellar biosynthesis and motility was observed. These data further demonstrate that bile is an important environmental signal sensed by Salmonella spp. and that bile plays a role in regulating bacterial gene expression in multiple virulence-associated pathways.

An investigation of the molecular basis of the spontaneous occurrence of a catalase-negative phenotype in Helicobacter pylori

BACKGROUND

The discovery of a highly active catalase in Helicobacter pylori that in some strains may lose its activity has generated strong scientific interest. We have characterized a spontaneous catalase-negative isolate of H. pylori (UNSW-RU1) and sequenced katA in the parent strain and the promoters of both phenotypes as a prelude to understanding the genetic processes leading to the failure to express catalase.

MATERIALS AND METHODS

Protein extracts from both phenotypes were examined for catalase on 2D-PAGE and analyzed by Western blot-based immuno-analysis. Presence of catalase mRNA was detected by Northern blot. Hi-Fidelity PCR was used to sequence the katA promoter while katA was sequenced using cycle-sequencing. The transcription start site was located by primer extension.

RESULTS

Catalase protein was absent in UNSW-RU1 (KatA-) by 2D-PAGE and Western blot, as was catalase mRNA by Northern blot, indicating that the cause of the KatA- phenotype was at the level of transcription. No mutations were found in the promoter region of the KatA- isolate. The transcription start site was identified 55 bp upstream of the ATG site and putative RNA polymerase binding sites were mapped at "-10" and "-35". A Fur box was identified 181 bp upstream of the transcription start site. The sequences of an 876 bp ORF and a 366 bp Escherichia coli phnA homologue were identified.

CONCLUSIONS

The UNSW-RU1 (KatA-) phenotype does not express KatA or transcribe katA. The absence of defects in its promoter and a large part of its ORF indicates that loss of activity may be due to a mutation in an accessory gene essential for catalase expression, or to the binding of a repressor preventing katA transcription.

The mode of action of metronidazole in Helicobacter pylori: futile cycling or reduction?

The effects of metronidazole on catalase-positive and spontaneous catalase-negative mutants of Helicobacter pylori were studied to investigate whether the action of metronidazole on this microaerophilic organism occurs by reactive oxygen species generated by futile cycling or by the reduction of metronidazole to its active form. Increased sensitivity would be expected to occur in catalase-negative mutants if the mode of action of metronidazole was mediated through reactive oxygen species that may result from futile cycling of metronidazole. Two strains, RU1 and N6, were found to mutate spontaneously to a catalase-negative phenotype. The catalase-positive strain RU1(KatA+) and its catalase-negative counterpart RU1(KatA-) were sensitive to metronidazole, with MICs of 0.5 mg/L. The metronidazole-sensitive strain RU1(KatA-) lost viability at a rate similar to the parent RU1(KatA+) strain in the presence of 10 mg/L of metronidazole. Stable resistance to metronidazole was induced in RU1(KatA+) and RU1(KatA-) by passaging these strains in the presence of metronidazole. The catalase-positive and catalase-negative strains, N6(KatA+) and N6(KatA-), were resistant to metronidazole, with MICs of 96 mg/L. These observations indicated that the presence or absence of catalase activity did not affect the susceptibility of strains to metronidazole. The metabolism of metronidazole by H. pylori was investigated by 14N-NMR spectroscopy. Metronidazole was reduced in sensitive, catalase-positive and catalase-negative strains. Metronidazole-resistant cells reduced the 5-nitroimidazole more slowly, suggesting that resistance is achieved through the prevention or inhibition of metronidazole reduction.

Peritoneal dialysate IgG/C3 levels do not predict susceptibility to peritonitis

OBJECTIVE

To investigate the usefulness of dialysate IgG and C3 concentrations in predicting likelihood of developing peritonitis.

DESIGN

Prospective, longitudinal, and comparative study.

SETTING

Single university teaching hospital dialysis unit and outpatient clinic.

PATIENTS

Thirty-four uremic patients were studied (20 males, 14 females: mean age 47.2, range 20-73 years). Monthly serum and overnight dialysate (eight- to eleven-hour dwell) samples were obtained for IgG and C3 estimations over the first six months of the study, and trimonthly samples were obtained thereafter. All patients performed exchanges using standard transfer sets (Baxter system II, Baxter Healthcare Ltd., Thetford, Norfolk, U.K.), used no hypertonic fluid (3.86%) for overnight exchanges, and were followed up for a minimum of 18 months.

OUTCOME MEASURES

Dialysate and serum levels of IgG and C3; peritonitis episodes.

RESULTS

Forty-five episodes of peritonitis occurred in 24 patients during the study period. We examined opsonin levels in the group as a whole, and then in two subgroups of patients: those who remained peritonitis-free throughout the study, and those who did not. There were no significant differences between IgG and C3 levels in the two groups at any time point, and large interpatient and intrapatient variation in levels were seen.

CONCLUSION

Dialysate levels of IgG and C3 from the overnight dwell are not helpful in predicting the risk of developing continuous ambulatory peritoneal dialysis peritonitis in individual patients. No correlation was found between opsonin levels and onset of clinical peritonitis.

A comprehensive hematologic study in calves with total artificial hearts

Thromboembolism and infection remain potential threats for long-term circulatory assist and replacement devices. The alteration of the hemostatic system and of blood cell functions caused by device implantation may predispose the recipient to these complications. Many sensitive coagulation assays and the technology of flow cytometry would be powerful tools for this investigation. The availability of such immunologic technologies for animal species other than humans has yet to be established. In a series of in vitro tests we found that the following assays, among others, are usable in calves: TAT, TxB2, platelet surface glycoprotein IIbIIIa, and membrane aminophospholipid. F1.2, D-dimer, beta TG, PF-4, and platelet surface expression of GMP-140 and receptors for fibronectin, thrombospondin, and vWF were not measurable. A sustained mild decrease in hematocrit levels in six calves with the Cleveland Clinic-Nimbus total artificial heart for 11-120 days was attributed to an increase in circulating blood volume, but not to red blood cell damage. Whole blood platelet aggregation was suppressed only for the first 3 post operative days, with decreased GPIIbIIIa expression. Polymorphonuclear phagocytosis, chemotaxis, and superoxide anion production were not altered. Device infection and thromboembolism occurred in one of 13 cases overall.

Pre-preparation of the sterile instrument table for emergency cesarean section

Cesarean section instrument tables are often not prepared in advance because of concern of contamination risk. The Association of Operating Room Nurses Standards decries the use of pre-preparation of surgical instrument tables because of this risk, although there are no scientific data to support this claim. We evaluated the contamination risk of pre-preparation of surgical instrument tables, prolonged table coverage and table uncovering using a specific technique referred to as the "sardine can roll." Colony counts were positive in only seven of 180 cultures (< or = 15 colonies per plate in each instance) from six tables evaluated after prolonged coverage or uncovering, or both. These data suggest that contamination risk is slight for the uncovering technique described herein and advance table preparation (24 hours or less, never recovered) is a reasonable clinical option in units in which table preparation reduces response time in emergent clinical situations, such as cesarean section for acute fetal distress.

A long-term study of doxazosin in the treatment of mild or moderate essential hypertension in general medical practice

This study assessed the long-term (54 weeks) antihypertensive efficacy and safety of doxazosin in the treatment of mild or moderate essential hypertension, defined as sitting and standing diastolic blood pressure of 95 to 114 mm Hg. Of the 153 patients who successfully completed an initial 14-week trial, 61 continued uninterrupted into a 40-week extension study. Optimal antihypertensive efficacy was achieved by week 12 and maintained in all patients for the duration of 1 year. The final mean sitting blood pressure was 148/84 mm Hg and was reduced from a mean baseline level of 173/102 mm Hg. Occasional decreases in heart rate were observed, but these were not considered to be clinically relevant (1 to 3 beats/min). The mean final dose of doxazosin for patients evaluable for efficacy was 2.4 mg/day; 91.7% of patients were taking less than or equal to 4 mg/day. No increase in daily maintenance dose was observed from the initial phase to the long-term extension study. After 1 year of treatment, 93.3% of patients were considered a therapeutic success (sitting diastolic blood pressure greater than or equal to 10 mm Hg reduction from baseline or less than or equal to 90 mm Hg with greater than or equal to 5 mm Hg reduction). In no patients was there a worsening in the severity category of the hypertension. Total serum cholesterol concentrations were reduced significantly (6.6% p = 0.03) at the end of week 14. Reductions in total serum cholesterol levels persisted throughout the extension study, with a final reduction of 5.4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that matching for HLA antigens significantly increases transplant survival in 1001 renal transplants performed in the northwest region of England

In the 20-year period from March 1968 to March 1988, 860 patients received 1001 renal transplants in the Northwestern Regional Renal Transplant Unit at Manchester Royal Infirmary. Through a continuing policy of avoiding mismatches for HLA antigens and lymphocytotoxic antibody crossmatching, transplant survival rates were found to correlate with the degree of HLA-A and B antigen mismatching from 1968 to 1978 and with HLA-B and DR antigen mismatching from 1979 to 1988. Mismatching for HLA-B and DR antigens was also found to correlate with transplant survival in highly sensitized patients and in patients transplanted since 1981, the "cyclosporine era." Recipients who were HLA-DR1 positive were found to have the highest graft survival compared to recipients negative for this antigen. In contrast, HLA-DR3 positive recipients had the poorest outcome. Transplants from HLA-DRw6 positive donors showed higher transplant survival rates than donor kidneys positive for any other HLA-DR antigen. A correlation of transplant survival with HLA-B and DR mismatching was seen whether kidneys were collected within our region or received through the UK Transplant Service. We conclude that avoidance of mismatching for HLA-B and DR antigens confers high transplant survival rates (91.1% at 5 years for 0 HLA-B and DR mismatches), and in order to achieve this rate for most recipients exchange of donor kidneys between transplant centers will be essential.

Cryptococcosis complicating continuous ambulatory peritoneal dialysis

We report a case of invasive cryptococcosis complicating continuous ambulatory peritoneal dialysis and its successful treatment. This form of infection has not been previously described.

Successful renal transplantation of patients sensitized following deliberate unrelated blood transfusions

One of the most powerful influences on cadaveric renal graft survival is the enhancing effect of blood transfusions from unrelated individuals (1, 2). However, the optimum number of transfusions required to achieve this effect remains controversial. Enhanced graft survival following only one or two transfusions has been observed (3), although graft survival has also been found to be better for multitransfused recipients (4). Extrapolating from their studies on mice, Wood et al. (5) suggested that only a very small volume of blood may induce the transfusion effect in humans. As the number of transfusions increases so does the risk of sensitizing the patient to produce lymphocytotoxic antibodies that may impair the chances of the patient receiving a crossmatch-negative kidney graft (6, 7). Thus the problem is to minimize the chance of sensitization while still maintaining the beneficial effect of blood transfusion.

Relapsing idiopathic membranous nephropathy

In a series of 60 patients with idiopathic membranous nephropathy (IMN), 8 subjects, aged 16-65 years at presentation, suffered spontaneous relapse of proteinuria after remissions of 25 months to 30 years. Renal biopsy was performed at the time of relapse in 5 cases and revealed histopathology identical to that of the original lesion. Eight courses of immunosuppressive therapy given to 6 patients did not affect either the appearance or duration of remission or relapse. No patient had a familial tendency to renal disease. Immunogenetic markers, HLA A, B and DR, did not distinguish those who relapsed from other patients with IMN. At the end of the study, 3 patients were in a second remission, one had died of myocardial infarction during relapse, 3 remained nephrotic and one had mild renal insufficiency but no proteinuria. As compared with the rest of the series the overall prognosis was not influenced by the relapses.

Strong association between idiopathic membranous nephropathy and HLA-DRW3

HLA A, B, and DR antigens were determined in a homogeneous group of patients with idiopathic membranous nephropathy. The frequency of HLA-DRW3 was significantly higher in the patients than in a control population. The frequencies of HLA B8 and B18, which are in linkage disequilibrium with DRW3, were also increased.