Vitamin D supplementation in CKD

Vitamin D deficiency is common in chronic kidney disease and is associated with increased morbidity and mortality. In addition, vitamin D deficiency in renal disease is associated with serious comorbidities including secondary hyperparathyroidism and cardiovascular disease. Several therapeutic options are available to correct vitamin D deficiency, including nutritional vitamin D, pro-hormones and active hormones. In this review we discuss clinical findings related to the effectiveness of these therapies in chronic kidney disease.

Serotypes, virulence genes, intimin types and PFGE profiles of Escherichia coli isolated from piglets with diarrhoea in Slovakia

Two hundred and fifty Escherichia coli isolates from diarrhoeic and healthy piglets were serotyped and tested for the presence of virulence genes for fimbriae, intimin, heat-labile (LT) and heat-stable (STa and STb) enterotoxins, Stx toxins, and enteroaggregative heat-stable 1 (EAST1) enterotoxin by polymerase chain reaction (PCR). Although 220 isolates from diarrhoeic piglets belonged to 43 O serogroups and 77 O:H serotypes, 60% were of one of the 10 serogroups O2, O8, O15, O54, O84, O101, O141, O147, O149 and O157, and 60% belonged to only 10 serotypes (O8:H-, O54:H-, O84:H7, O101:H-, O141:H-, O141:H4, O147:H-, O149:H10, O163:H-, and ONT:H-). PCR showed that 79% of 220 isolates carried genes for at least one of the virulence factors tested. The gene encoding for EAST1 was the most prevalent (65%) followed by those encoding for STb (49%), LT (42%), STa (13%), and Stx2e (4%). Eighty-three (38%) of the 220 E. coli isolates carried the gene for F4 (K88), whereas genes for F18, F5 (K99), F41, F6 (P987), F17, and intimin (eae) were detected in 9%, 3%, 3%, 3%, 1%, and 3%, respectively. Seropathotype O149:H10:F4:LT/STb/EAST1 (70 isolates) was the most common, representing 32% of isolates. Pulsed-field gel electrophoresis (PFGE) analysis with XbaI of 15 O149:H10 representative isolates from diarrhoeic piglets distinguished 14 types. The 15 isolates exhibited a wide variability of distinct restriction patterns though all belonged to the same serotype (O149:H10), and all but one showed identical virulence determinants (F4, LT, STb, and EAST1). Among 30 isolates from healthy piglets only two virulence genes were detected: EAST1 (26%) and eae (17%). In total, 12 isolates were positives for the eae gene: five isolates had intimin beta1, four possessed intimin theta and three showed intimin type xiB. This is believed to be the first study describing the presence of intimin type xiB in E. coli of porcine origin.

Serotypes, virulence genes, and intimin types of Shiga toxin (verotoxin)-producing Escherichia coli isolates from cattle in Spain and identification of a new intimin variant gene (eae-xi)

A total of 514 Shiga toxin-producing Escherichia coli (STEC) isolates from diarrheic and healthy cattle in Spain were characterized in this study. PCR showed that 101 (20%) isolates carried stx(1) genes, 278 (54%) possessed stx(2) genes, and 135 (26%) possessed both stx(1) and stx(2). Enterohemolysin (ehxA) and intimin (eae) virulence genes were detected in 326 (63%) and in 151 (29%) of the isolates, respectively. STEC isolates belonged to 66 O serogroups and 113 O:H serotypes (including 23 new serotypes). However, 67% were of one of these 15 serogroups (O2, O4, O8, O20, O22, O26, O77, O91, O105, O113, O116, O157, O171, O174, and OX177) and 52% of the isolates belonged to only 10 serotypes (O4:H4, O20:H19, O22:H8, O26:H11, O77:H41, O105:H18, O113:H21, O157:H7, O171:H2, and ONT:H19). Although the 514 STEC isolates belonged to 164 different seropathotypes (associations between serotypes and virulence genes), only 12 accounted for 43% of isolates. Seropathotype O157:H7 stx(2) eae-gamma1 ehxA (46 isolates) was the most common, followed by O157:H7 stx(1) stx(2) eae-gamma1 ehxA (34 isolates), O113:H21 stx(2) (25 isolates), O22:H8 stx(1) stx(2) ehxA (15 isolates), O26:H11 stx(1) eae-beta1 ehxA (14 isolates), and O77:H41 stx(2) ehxA (14 isolates). Forty-one (22 of serotype O26:H11) isolates had intimin beta1, 82 O157:H7 isolates possessed intimin gamma1, three O111:H- isolates had intimin type gamma2, one O49:H- strain showed intimin type delta, 13 (six of serotype O103:H2) isolates had intimin type epsilon and eight (four of serotype O156:H-) isolates had intimin zeta. We have identified a new variant of the eae intimin gene designated xi (xi) in two isolates of serotype O80:H-. The majority (85%) of bovine STEC isolates belonged to serotypes previously found for human STEC organisms and 54% to serotypes associated with STEC organisms isolated from patients with hemolytic uremic syndrome. Thus, this study confirms that cattle are a major reservoir of STEC strains pathogenic for humans.

Prevalence and characterization of Vero cytotoxin-producing Escherichia coli isolated from diarrhoeic and healthy sheep and goats

Faecal samples from 146 diarrhoeic lambs and goat kids, and from 511 healthy sheep and goats were screened for the presence of Vero cytotoxin-producing Escherichia coli (VTEC). In healthy sheep and goats, VTEC were isolated in 24.4 and 16.2% of the animals, respectively. Moreover, VTEC were detected in 3.1 and 5.9% of the diarrhoeic lambs and goat kids, respectively. These data suggest that VTEC seems not to be associated with diarrhoea in lambs and goat kids. Only four VTEC strains were eae-positive. The absence of the eae gene in most of these VTEC strains could indicate that these strains are less virulent for humans that the classical eae-positive enterohaemorrhagic E. coli types. However, almost half (42.9%) and 12.2% of VTEC strains isolated from healthy sheep and goats, respectively, belonged to serotypes associated with severe diseases in humans.

Serotypes, virulence genes, and intimin types of Shiga toxin (verotoxin)-producing Escherichia coli isolates from healthy sheep in Spain

Fecal swabs obtained from 1,300 healthy lambs in 93 flocks in Spain in 1997 were examined for Shiga toxin-producing Escherichia coli (STEC). STEC O157:H7 strains were isolated from 5 (0.4%) animals in 4 flocks, and non-O157 STEC strains were isolated from 462 (36%) lambs in 63 flocks. A total of 384 ovine STEC strains were characterized in this study. PCR showed that 213 (55%) strains carried the stx(1) gene, 10 (3%) possessed the stx(2) gene, and 161 (42%) carried both the stx(1) and the stx(2) genes. Enterohemolysin (ehxA) and intimin (eae) virulence genes were detected in 106 (28%) and 23 (6%) of the STEC strains, respectively. The STEC strains belonged to 35 O serogroups and 64 O:H serotypes (including 18 new serotypes). However, 72% were of 1 of the following 12 serotypes: O5:H-, O6:H10, O91:H-, O117:H-, O128:H-, O128:H2, O136:H20, O146:H8, O146:H21, O156:H-, O166:H28, and ONT:H21 (where NT is nontypeable). Although the 384 STEC strains belonged to 95 different seropathotypes (associations between serotypes and virulence genes), 49% of strains belonged to only 11. O91:H- stx(1) stx(2) (54 strains) was the most common seropathotype, followed by O128:H- stx(1) stx(2) (33 strains) and O6:H10 stx(1) (25 strains). Three strains of serotypes O26:H11, O156:H11, and OX177:H11 had intimin type beta1; 5 strains of serotype O157:H7 possessed intimin type gamma1; and 15 strains of serotypes O49:H-, O52:H12, O156:H- (12 strains), and O156:H25 had the new intimin, intimin type zeta. The majority (82%) of ovine STEC strains belonged to serotypes previously found to be associated with human STEC strains, and 51% belonged to serotypes associated with STEC strains isolated from patients with hemolytic-uremic syndrome. Thus, this study confirms that healthy sheep are a major reservoir of STEC strains pathogenic for humans.

Soluble IL-6 receptor levels in patients on chronic hemodialysis

Osteitis fibrosa, a part of the spectrum of renal osteodystrophy, is characterized by high bone turnover as a result of high circulating levels of parathyroid hormone (PTH). It is well accepted that the bone resorptive effects of PTH occur, at least in part, by inducing osteoblasts to secrete cytokines that stimulate both differentiation and activation of osteoclasts. One such cytokine, interleukin 6 (IL-6), exerts its actions via the IL-6 receptor (IL-6R), which has alpha and beta subunits. The alpha subunit binds IL-6 and exists in both membrane bound and soluble forms which can interact with the signal transducing components of the receptor or beta subunits and result in the same biological effect. Abnormalities in the IL-6 system have the potential to affect bone turnover and to modulate the effects of PTH. In this regard, we examined the levels of circulating soluble IL-6 receptor (sIL-6R) and plasma intact PTH in 27 patients on hemodialysis, of whom 15 were on therapy with vitamin D compounds and 12 were vitamin D naive. The results were compared to values obtained from 9 healthy controls. Blood samples were obtained pre-dialysis and sIL-6R levels were determined using a commercially available enzyme immunoassay, which measures biologically active sIL-6R. In patients on chronic hemodialysis, plasma levels of sIL-6R were 123.4 +/- 11.01 ng/ml. In healthy controls, the levels were 99.61 +/- 11.52 ng/ml, values not significantly different from those found in dialysis patients. PTH values ranged from 7-1,709 pg/ml in patients on hemodialysis; however, there was no correlation between intact PTH levels and the levels of sIL-6R. Similarly, vitamin D therapy did not influence the levels of sIL-6R. These data indicate that using an assay which is specific for biologically active sIL-6R, the levels of this receptor in patients on hemodialysis are similar to those found in normal individuals and neither the levels of PTH nor vitamin D therapy alter this aspect of IL-6 action.

Mechanism of retinoic acid induced attenuation of PTH action in UMR 106-01 cells

Studies from our laboratory in osteoblast-like cells have shown that the increase in EGF receptor expression in response to PTH was cyclic AMP mediated and was blocked by treatment with retinoic acid (RA). The present studies investigate the mechanism for this effect of RA on PTH actions. UMR 106-01 cells were exposed to RA and were tested for cAMP response to PTH as well as for (125)I PTH binding. cAMP production in response to PTH was markedly decreased by RA (25.1 +/- 1.6% of control) whereas there was only a slight decrease in PTH binding in response to RA. For the study of adenylate cyclase activity, membranes were isolated from intact cells that had been exposed to RA. Treatment with RA decreased PTH-stimulated adenylate cyclase activity; however, forskolin-stimulated enzyme activity was unchanged. Treatment of intact cells with pertussis toxin, to inactivate Gi, did not alter the inhibitory effect of RA on PTH-stimulated adenylate cyclase activity. Addition of GppNHp, a non-hydrolyzable analogue of GTP, completely restored the response to PTH in the membranes. Therefore, we examined the activity of IMP dehydrogenase, the rate-limiting enzyme for GTP biosynthesis, and GMP reductase which counteracts the effect of the synthetic enzyme. Treatment with RA for 48 hours increased GMP reductase activity by 240.9 +/- 24.2% and decreased IMP dehydrogenase activity to 67.5 +/- 8.8% of control values. These data indicate that RA impairs the response to PTH in intact cells. This blunted response was preserved in membrane preparations but was corrected by GTP. The RA-induced alterations of enzymes involved in the GTP biosynthetic pathway in a direction that favors a decrease in GTP biosynthesis provide an explanation for the inhibitory effect of RA on PTH actions.

Strategies to minimize bone disease in renal failure

The skeletal disorders associated with renal insufficiency result from alterations in calcium, phosphorus, and vitamin D metabolism. Each requires intervention to prevent and control the problem. Hyperparathyroidism and its treatment can also result in extraskeletal complications. To prevent the development of parathyroid hyperplasia and the skeletal complications of chronic kidney disease, it is desirable to initiate interventions early in the course of kidney disease; however, many patients present with established hyperparathyroidism and additional strategies are necessary to suppress hyperparathyroidism. Mainstays of this approach are the control of phosphorus and the use of vitamin D analogs. Phosphorus control requires the use of phosphate binders, preferably non-calcium-containing binders, to prevent intestinal phosphorus absorption. Vitamin D analogs are used to suppress hyperparathyroidism and have the potential to have lesser toxicity than calcitriol. Paricalcitol is the most widely used vitamin D analog in this country and it effectively suppresses hyperparathyroidism with only minimal effects on calcium and phosphorus. A substantial body of data in experimental animals supports the use of paricalcitol as a preferential therapeutic agent. Recently, an additional vitamin D sterol, doxercalciferol, has been introduced, which is metabolized to 1,25-dihydroxyvitamin D(2). Although initially thought to have lesser toxicity than its vitamin D(3) counterpart, recent studies have not provided support for a major difference in this regard. Doxercalciferol is also effective in lowering parathyroid hormone (PTH), though hypercalcemia in hyperphosphatemic episodes occurred relatively frequently during the clinical studies. As these therapeutic strategies are undertaken, it is important not to oversuppress PTH and decrease bone turnover to abnormally low levels because of the risk for adynamic renal bone disease. It is possible that when bone turnover is abnormally low, the extraskeletal deposition of calcium in blood vessels and other tissues is enhanced. Accordingly, constant monitoring is required during treatment, with emphasis on minimizing the calcium load, and, if monitored correctly, a satisfactory control of hyperparathyroidism may be achieved with the agents currently available.

Vitamin D analogues for the management of secondary hyperparathyroidism

Secondary hyperparathyroidism complicating chronic kidney disease requires therapy to minimize the effects of parathyroid hormone (PTH) on bone and other tissues. Low levels of calcitriol in blood play a major role in the initiation and maintenance of hyperparathyroidism. Accordingly, administration of calcitriol has been demonstrated to be an effective form of therapy. While this therapy is effective in controlling hyperparathyroidism, side effects of calcitriol, including increased intestinal absorption of calcium and phosphate, often complicate therapy by giving rise to hypercalcemia and hyperphosphatemia, which may be important risk factors for extraskeletal calcifications. Over the last several years, interest has turned toward vitamin D analogs, which may be able to affect parathyroid function with lesser effects on calcium and phosphorus in serum, and thereby, minimizing the undesirable toxicities of vitamin D therapy. Two vitamin D analogs are available in this country for the control of hyperparathyroidism in the setting of advanced kidney disease, and include 19-nor-1,25-dihydroxyvitamin D(2) (paricalcitol), and more recently, 1-alpha-hydroxyvitamin D(2) (doxercalciferol). 19-nor-1,25-dihydroxyvitamin D(2) is widely used and was evaluated extensively in animals, revealing that this vitamin D sterol had a selective effect on increasing PTH suppression, with lesser effects on calcium and phosphorus metabolism. These studies lead to clinical trials which showed the efficacy of this therapy in that PTH could be lowered satisfactorily in patients with calcium and phosphorus values within the normal range. The selectivity of 19-nor-1,25-dihydroxyvitamin D(2) seen in animals has also been found in humans, such that therapy with this sterol can achieve control of hyperparathyroidism with a wider therapeutic window than the predecessor, calcitriol. 1-alpha-hydroxyvitamin D(2) has recently been introduced, but in contrast to paracalcitol, there is little reason to believe that there is any selectivity in its actions in terms of suppressing PTH, compared with its ability to raise serum calcium or phosphorus in serum. However, this vitamin D sterol can effectively decrease PTH levels in patients with advanced renal failure. Comparative studies of paricalcitol and doxercalciferol have not been undertaken at the present time. Further studies on the mechanism of actions might explain the differences between these sterols and their effects on the intestinal absorption of calcium and phosphate. At the present, the use of vitamin D analogs can achieve control of hyperparathyroidism with a wider therapeutic window than the native sterol, calcitriol.

A long-term, multicenter study of the efficacy and safety of paricalcitol in end-stage renal disease

BACKGROUND

Paricalcitol is a vitamin D analog approved for the prevention and treatment of secondary hyperparathyroidism associated with chronic renal failure. This study was designed to evaluate the long-term efficacy and safety of paricalcitol. Additional analysis evaluated the effects of paricalcitol in hypocalcemic and hyperphosphatemic subpopulations.

PATIENTS AND METHODS

One hundred sixty-four end-stage renal disease (ESRD) patiesnts on hemodialysis were treated in an open-label, multicenter study lasting up to 13 months in duration. After a baseline or washout period, an initial starting dose of 0.04-0.393 microg/kg was given 2-3 times per week. This dose was adjusted at the discretion of the investigator according to the patient's intact parathyroid hormone level (iPTH), calcium level, and calcium-phosphorus (Ca x P) product. The therapy was intended to reproduce expected clinical use of paricalcitol. Patients represented a wide cross-section of the ESRD population, and were not excluded from the study based on age or underlying disease.

RESULTS

The mean paricalcitol dose level throughout the study was 0.10 microg/kg. The mean iPTH levels (baseline mean 628.3 +/- 27.65 pg/ml) decreased rapidly during the first 4 months of therapy, and reached the designated target range (100-300 pg/ml) by month 5 (mean 295.3 +/- 25.69 pg/ml). A maximum mean decrease in iPTH level of 409 +/- 35.01 pg/ml was seen at month 13. Throughout the course of the study, the mean normalized calcium level was maintained well within the normal range (9.44-9.94 mg/dl). The mean phosphorus level was maintained in an acceptable range throughout the study (5.92-6.53 mg/dl). Mean Ca x P product was maintained between 52 and 65. Mean alkaline phosphatase levels decreased significantly from baseline with a maximum mean decrease of 62 +/- 17.3 U/l observed at month 9. In 34 initially hypocalcemic patients (mean of 7.7 mg/dl) iPTH levels decreased from baseline, on average, by 443 +/- 81.86 pg/ml while mean calcium levels rose by 1.2 +/- 0.23 mg/dl to reach the normal range. In 35 initially hyperphosphatemic patients (mean of 8.0 mg/dl) iPTH levels decreased, on average, by 515 +/- 103.31 pg/ml with an associated mean decrease in phosphorus of 0.57 +/- 0.52 mg/dl. Adverse events that were considered by the investigator to have a possible. probable, or definite relationship to study drug occurred in 26% of patients. Other than expected temporary effects of hypercalcemia and hyperphosphatemia. the only possible trends for causally-related adverse events were for nausea/vomiting and metallic taste.

CONCLUSIONS

This long-term study of paricalcitol demonstrates that it rapidly and effectively suppresses iPTH levels in a wide spectrum of ESRD patients and caused no unexpected adverse events.

The evolution of assays for parathyroid hormone

Recent progress in the assay of parathyroid hormone has revealed that commercially available assays for intact parathyroid hormone also measure additional parathyroid hormone peptides that appear to be truncated at the amino-terminal region and have the elution position on high-performance liquid chromatography of parathyroid hormone 7-84. Specific assays have been developed that measure only the true or 'whole', 84-amino-acid peptide. Such 'whole' parathyroid hormone assays have led to the discovery of new findings that suggest that parathyroid hormone fragments such as parathyroid hormone 7-84, which have hitherto been considered to be biologically inactive, may actually have biologic effects. These data, coupled with the emerging discovery of additional receptors for parathyroid hormone peptides, suggest that parathyroid hormone fragments might have potentially important actions, at least in the setting of renal failure.

Therapy of secondary hyperparathyroidism with 19-nor-1alpha,25-dihydroxyvitamin D2

Secondary hyperparathyroidism contributes to significant morbidity in patients with chronic renal failure. The treatment of this disorder with vitamin D compounds, such as calcitriol, although effective at suppressing parathyroid hormone (PTH) secretion, may promote the development of hypercalcemia and hyperphosphatemia, thus increasing the risk for metastatic calcification. A new vitamin D analogue, 19-nor-1alpha,25-(OH)2D2 (paricalcitol; Zemplar, Abbott Laboratories, Inc, Chicago, IL) has recently been developed for the treatment of secondary hyperparathyroidism, and, in experimental animals, it was found to be less calcemic and phosphatemic than calcitriol. In double-blind clinical trials, paricalcitol effectively decreased the levels of PTH by 60%, yet the mean serum calcium values remained within the normal range. The few episodes of hypercalcemia that occurred in the paricalcitol-treated patients (8 of 400 determinations > or =11.0 mg/dL in 7 patients) were associated with marked decreases in PTH levels (87% +/- 2% less than baseline) and absolute values of PTH less than 100 pg/mL in four of the seven patients. PTH values less than 100 pg/mL, however, occurred in 15 patients, but were not invariably associated with frank hypercalcemia, although serum calcium levels increased to 10.63 +/- 0.3 mg/dL, slightly greater than the upper limits of normal. Additional studies to evaluate the conversion from calcitriol to paricalcitol therapy showed that a dose ratio of 1:4 (calcitriol:paricalcitol) could maintain control of high levels of PTH without significant alterations in serum calcium and phosphorus levels. These studies indicate that effective control of hyperparathyroidism can be achieved with paricalcitol therapy with minimal perturbation of serum calcium and phosphorus levels, and may have a therapeutic advantage over current treatment strategies.

19-Nor-1-alpha-25-dihydroxyvitamin D2 (Paricalcitol) safely and effectively reduces the levels of intact parathyroid hormone in patients on hemodialysis

Paricalcitol (19-nor-1alpha-25-dihydroxyvitamin D2), a new vitamin D analog developed for the treatment of secondary hyperparathyroidism, was evaluated in three double-blind, placebo-controlled, dose-escalating, randomized multicenter trials. A total of 78 patients (40 Paricalcitol injection, 38 placebo) achieved treatment phase eligibility, which included intact parathyroid hormone (iPTH) > or = 400 pg/ml, normalized serum calcium levels between 8.0 and 10.0 mg/dl, and calcium x phosphorus product values less than 75. Study end points included a decrease in iPTH of at least 30% or a maximum of five dose escalations. After a 4-wk washout, paricalcitol or placebo was administered intravenously three times per week after dialysis for 12 wk. Study drug was started at a dose of 0.04 microg/kg and was increased by 0.04 microg/kg every 2 wk to a maximal allowable dose of 0.24 microg/kg or until at least a 30% decrease in serum iPTH was achieved. The dose of paricalcitol that decreased iPTH by at least 30% became the maintenance dose. Of 40 patients receiving paricalcitol, 27 (68%) had at least a 30% decrease in serum iPTH for 4 consecutive weeks, compared with three of 38 patients (8%) receiving placebo (P < 0.001). For patients who received 12 wk of treatment with paricalcitol, the levels of iPTH decreased significantly from 795+/-86 to 406+/-106 pg/ml (P < 0.001), whereas the values for PTH were 679+/-41 pg/ml before and 592+/-41 pg/ml after 12 wk of therapy in patients receiving placebo (P=NS). Also, there was a significant difference between treatment groups for the change from baseline PTH levels (P < 0.001). Paricalcitol treatment resulted in a significant reduction in serum alkaline phosphatase from 148+/-23 U/L to 101+/-14 U/L (P < 0.001) in patients treated for 12 wk compared with 120+/-9 U/L to 130+/-11 U/L (P=NS) in patients receiving placebo for 12 wk. Importantly, hypercalcemia did not occur before achieving target serum iPTH levels in any of the paricalcitol-treated patients. There was no significant difference for the change from baseline in serum phosphorus within or between treatment groups. There was no significant difference in adverse events between the paricalcitol and placebo-treated groups. These studies demonstrate that paricalcitol safely and effectively suppresses iPTH levels in hemodialysis patients. This second generation vitamin D analog may have a wider therapeutic window than current vitamin D preparations, and thus may allow reduction in PTH with less hypercalcemia.

Colonization antigens of enterotoxigenic Escherichia coli strains isolated from piglets in Spain

Eighty-eight enterotoxigenic E.coli strains isolated from 69 pigs with enteric infections (diarrhoea or oedema disease) were investigated for the presence of F4 (K88), F5 (K99), F6 (987P) and F41 colonization antigens. The commonest colonization antigen was F6 (987P), which was detected in ETEC strains from 31.9% pigs, followed by F5 (K99) 11.6%, F4 (K88) 10.1% and F41 8.7%. Presence of F6 (987P) and F5 (K99) fimbriae was statistically associated (0.025 > p < 0.005) with diarrhoeic piglets younger than 15 days. F4 (K88) colonization antigen was only expressed by ETEC isolated from piglets older than 15 days. 90.5% of ETEC isolated from 90.0% of piglets younger than 15 days expressed F5 (K99), F6 (987P) or F41 antigens, whereas only 31.3% ETEC isolated from piglets older than 15 days were positive for F4 (K88), F5 (K99), F6 (987P) or F41 antigens (p < 0.001). None of the ETEC pigs with oedema disease produced any of the four colonization antigens. ETEC bearing colonization antigens were associated with particular serogroups and toxic phenotypes, whereas 4P- ETEC strains showed diverse phenotypic characteristics.

Coordinate regulation of PTH/PTHrP receptors by PTH and calcitriol in UMR 106-01 osteoblast-like cells

High levels of PTH result in desensitization of target cells to further stimulation with PTH in vivo and in vitro. While studies in vitro demonstrate that the effect of PTH can be direct, it is also possible that studies in vivo may be complicated by the fact that other potential regulators of PTH action, such as increased levels of calcitriol, may play a role. Thus, we examined the actions of calcitriol and PTH on PTH/PTHrP-receptor expression in confluent cultures of UMR 106-01 osteoblast-like cells treated with calcitriol, PTH or both hormones for one to three days. Following these treatments, studies of PTH receptor binding, cAMP generation, and steady-state levels of PTH/PTHrP receptor mRNA were performed. Exposure to PTH resulted in a decrease in PTH stimulated cAMP generation by 88 +/- 2%, and PTH binding by 63 +/- 3%. Levels of PTH/PTHrP-receptor mRNA decreased progressively reaching 20% of control values after three days of PTH (100 nM) treatment. Calcitriol also resulted in a dose and time-dependent decrease in PTH/PTHrP-receptor mRNA, decreasing by 72 +/- 4% after 48 hours. PTH receptor binding and cAMP generation were diminished by 42 +/- 3% and 42 +/- 4%, respectively. Co-incubation of UMR 106-01 cells with submaximal doses of calcitriol and PTH together revealed that the levels of PTH/PTHrP-receptor mRNA were decreased by both hormones together to a greater extent than with either alone. These studies show that both calciotropic hormones, PTH and calcitriol, are potent regulators of PTH/PTHrP-receptor gene expression in UMR 106-01 osteoblast-like cells. Thus, stimulation of calcitriol production by PTH may result in a coordinated down-regulation of PTH receptor expression by these hormones.

Development and evaluation of an ELISA to detect Escherichia coli K88 (F4) fimbrial antibody levels

An enzyme-linked immunosorbent assay (ELISA) to determine IgG antibody levels against K88 (F4) fimbrial antigen from porcine enterotoxigenic Escherichia coli (ETEC) has been developed. The ELISA method was checked with serum samples obtained from rabbits and pigs, and the parameters affecting the method were also analysed. ELISA plates were optimally coated with K88 antigen 0.5 microgram/ml for testing rabbit antiserum or with 1.25 microgram/ml for testing pig serum. Optimal concentrations of H202 (0.5%) and orthophenylene-diamine (OPD) (0.125%) were chosen when a 10-min incubation period was used. The expression of antibody levels as enzyme-immunosorbent units (EIU) significantly decreased the variability of results between duplicate plates, when compared with the expression of results as direct OD values. ELISA-K88 applied to a field study with serum samples from 141 vaccinated and 52 unvaccinated sows was shown to be useful in differentiating between samples from vaccinated and unvaccinated animals.

Retinoids modulate the effect of PTH and calcitriol on EGF receptor expression in UMR 106-01 cells

Although osteoblast proliferation is a prominent feature of osteitis fibrosa, studies in vitro using osteoblast-like cells have shown that parathyroid hormone (PTH) impairs cell growth. Recent studies in our laboratory have shown that PTH increases epidermal growth factor (EGF) receptor expression in UMR 106-01 osteoblast-like cells, and thus, osteoblast proliferation may occur as a result of an enhanced response of the osteoblast to EGF. In the present studies we investigated the effect of calcitriol and the influence of retinoids on the regulation of EGF receptors. Calcitriol increased 125I-EGF binding 2.5-3-fold after 72 hours of incubation and was maximal at a calcitriol dose of 100 nM. Scatchard analysis showed that this effect was due to increased receptor number. In contrast, all-trans retinoic acid or 9-cis retinoic acid alone, even at 10 microM, caused less than a 50% increase in 125I-EGF binding. However, the effect of calcitriol was totally abolished in the presence of all-trans retinoic acid. 9-cis retinoic acid was equivalent with all-trans retinoic acid in this regard. In the presence of either retinoid, the stimulatory effect of PTH was totally eliminated and EGF binding was actually decreased below control values. Additional studies revealed that retinoic acid decreased PTH-stimulated cAMP generation in a dose-dependent manner. These data are consistent with our previous studies which showed that the effect of PTH on the induction of EGF receptors was mediated by a cAMP-dependent mechanism. The inhibition of the calcitriol effect by retinoids is consistent with the requirement of the retinoid-X-receptor (RXR) for binding of the vitamin D receptor (VDR) to its target sequences in DNA. These data indicate that EGF receptors in UMR 106-01 cells are up-regulated by PTH and calcitriol and that this process can be modulated by retinoids. Retinoids, therefore, may play a major role in the regulation of osteoblast function by PTH and calcitriol.

Fimbriae extracts from enterotoxigenic Escherichia coli strains of bovine and porcine origin with K99 and/or F41 antigens

Fimbriae extracts obtained using the thermal shock method, from bovine and porcine enterotoxigenic Escherichia coli strains with K99 and/ or F41 antigens, were analyzed by SDS-PAGE, immunoblotting and haemagglutinating activity. Three major protein bands with molecular weights 17 kDa, 29.3 kDa and 30.9 kDa were detected depending on the strain assayed. A 17 kDa band was identified as the fimbrial subunit for K99 fimbriae and was detected in strains of bovine and porcine origin. The 30.9 kDa band was identified as the fimbriae subunit for F41 fimbriae and was detected in all porcine strains with F41 antigen and only in the bovine strains of serogroups O9 and 0101 that proved positive for F41 antigen. The 29.3 kDa band was shown to be antigenically related to F41 and K88, and was only detected in bovine strains of serogroups O8 (5 strains) and O20 (a single strain). We speculate that the 29.3 kDa band may be related to the CS31A antigen.

Serogroups of Escherichia coli isolated from piglets in Spain

Serogroups of 1334 E. coli colonies isolated in Spain between 1986 and 1991 from piglets with diarrhoea, oedema disease and from healthy piglets, were determined. The serogroups determined in E. coli from diarrhoea were: O1, O2, O4, O5, O7, O8, O9, O12, O20, O21, O23, O25, O26, O32, O39, O45, O54, O75, O78, O80, O83, O91, O92, O101, O103, O113, O115, O116, O118, O125, O127, O138, O139, O141, O149, O153 and O157; from pigs with oedema disease: O8, O101, O138, O149 and O157; and from healthy piglets: O1, O2, O5, O7, O8, O9, O20, O21, O26, O29, O45, O64, O71, O80, O81, O91, O101, O105, O113, O115, O116, O126, O128, O132, O138, O139, O142, O146, O149, O152, O153, and O168. Serogroups O138, O141 and O149 were found to be statistically associated with enteric porcine colibacillosis (diarrhoea and oedema disease) (0.025 > P < 0.01). In addition, enterotoxigenic (ETEC) strains belonged to serogroups: O8, O9, O20, O101, O138, O141 and O149; verotoxigenic (VTEC) strains (VTEC) strains to serogroups 091 and 0138; and necrotizing (NTEC) strains to serogroups O2, O4, O8, O54, O78 and O83. Furthermore, 91.2% (249 out 273) of the ETEC (LT and/or STa) and/or VTEC strains belonged to only seven different serogroups. These major serogroups to which the ETEC and VTEC strains belonged, were determined in a lower percentage (21.2%) among non-toxigenic E. coli colonies isolated from sick and healthy piglets.

Isolation of K88 antigen variants (ab, ac, ad) from porcine enterotoxigenic Escherichia coli belonging to different serotypes

Fimbriae isolation by means of thermal shock was applied to fifteen K88-positive (three K88ab, nine K88ac and three K88ad) Escherichia coli reference strains belonging to serotypes O8:K87, O32, O45, O138:K81, O141:K85, O147:K89, O149:K91, and O157, as well as to ten K88-positive enterotoxigenic strains isolated from porcine diarrhea in Spain, all of them belonging to the O149 serogroup. Fimbriae were removed from the bacterial cells by thermal shock at 60 C and then precipitated using ammonium sulfate. The final amount of K88 antigen and the purification degree were not related to the serogroup of the bacteria or to the antigen variant but were related to the buffer used for isolation. Phosphate buffer containing urea was shown to be more effective than Tris-HCl for isolation of K88 antigen. The molecular weights by SDS-PAGE for K88ab, K88ac, and K88ad were 28.5, 29.2, and 31.0 kDa, respectively. All enterotoxigenic E. coli strains isolated in Spain showed the K88ac variant.

Genes coding for Shiga-like toxins in bovine verotoxin-producing Escherichia coli (VTEC) strains belonging to different O:K:H serotypes

Forty-six verotoxin-producing Escherichia coli (VTEC) strains isolated from diarrhoeic and healthy calves in Spain were examined for DNA sequences homologous to genes for verotoxins (VT1 and VT2) and enterotoxins (LT-I, LT-II, STaH, STaP and STb). Hybridisation showed that 26 (57%) of VTEC strains carried VT1 genes, 13 (28%) possessed VT2 genes, and 7 (15%) carried both VT1 and VT2 genes. No VTEC strains hybridised with DNA probes for enterotoxins. A correlation was found between the serotype and type of VT produced. Thus, all strains of serotypes O26:K-:H11 (13 strains), O103:K-:H2 (3 strains) and O128:K?:H- (4 strains) hybridised with the VT1 probe only, whereas all strains of serotypes O4:K-:H4 (3 strains) and O113:K-:H21 (4 strains) were positive with the VT2 probe only. By contrast, O81:K?:H28 (2 strains) and O157:K-:H- (2 strains) strains hybridised with both VT1 and VT2 probes. One strain of serotype O157:K-:H7 was VT2 positive.

Characteristics of haemolytic Escherichia coli with particular reference to production of cytotoxic necrotizing factor type 1 (CNF1)

A total of 1,106 Escherichia coli strains isolated in Spain between 1986 and 1991 from extraintestinal infections and faeces of healthy controls were examined for production of alpha-haemolysin (Hly). Among strains causing urinary tract infections, sepsis and other extraintestinal infections, Hly production was detected in 51% (P < 0.001), 32% (P < 0.001) and 18% (P < 0.02), respectively. In contrast, only 9% of faecal isolates from healthy individuals synthesized Hly. The 356 haemolytic E. coli strains characterized in this study belonged to 28 different serogroups. However, 284 (80%) were of one of eight serogroups (02, 04, 06, 08, 018, 022, 075 and 083); 40% and 31% of haemolytic strains expressed P fimbriae and mannose-resistant haemagglutination (MRHA) type III, respectively. We have found that haemolytic isolates of E. coli may clearly be divided into two categories on the basis of the ability to produce cytotoxic necrotizing factor type 1 (CNF1). The serogroups and adhesins determined in Hly+CNF1+ strains were generally different from those found in Hly+CNF1- strains. Thus, serogroups 02, 06 and 075 were associated with haemolytic E. coli producing CNF1+, whereas serogroups 01, 08, 018, 028 and 086 were established more frequently among Hly+CNF1- strains. While expression of P fimbriae was more frequently detected in Hly+CNF1- strains (70 versus 29%, P < 0.001), MRHA type III was usually identified in Hly+CNF1+ E. coli (42 versus 1%, P < 0.001). Furthermore, the sonic extracts of Hly+CNF1+ strains caused necrosis in rabbit skin (96 versus 25%, P < 0.001) and death in intraperitoneally injected mice (73 versus 11%, P < 0.001) more frequently than sonic extracts of Hly+CNF1- strains.

Establishment of three categories of P-fimbriated Escherichia coli strains that show different toxic phenotypes and belong to particular O serogroups

Eight hundred and nineteen strains of Escherichia coli isolated in Spain between 1986 and 1991 from extraintestinal infections and feces of healthy controls were investigated for expression of P-fimbriae using a particle agglutination test. Among strains causing urinary tract infections, sepsis and other extraintestinal infections, P-fimbriae were found in 31% (130/420) (P < 0.001), 25% (30/118) (P < 0.001) and 12% (11/92) (P < 0.5) respectively. In contrast, only 7% (14/189) of faecal isolates from healthy individuals carried P-fimbriae. According to two more common toxic markers detected in this study (alpha-haemolysin and cytotoxic necrotizing factor type 1), P-fimbriated E. coli strains were grouped into three categories: haemolysin+cytotoxic necrosing factor+ (Hly+CNF1+) (68/185; 37%), haemolysin+cytotoxic necrosing factor- (Hly+CNF1-) (61/185; 33%) and Hly-CNF1- (56/185; 30%). The 185 P-fimbriated strains belonged to 17 different O serogroups. However, 148 (80%) were of one of six serogroups (O1, O2, O4, O6, O7 and O18). The most frequent serogroups determined in the Hly+CNF1+ strains were the O4 and O6 (53/68; 78%), in the Hly+CNF1- strains it was the O18 (27/61; 44%) and in the Hly-CNF1- strains the O1, O2 and O7 (41/56; 73%). The majority (160/185; 86%) of P-fimbriated E. coli expressed the mannose-resistant haemagglutinin type IVa.

Serogroups of Escherichia coli strains producing cytotoxic necrotizing factors CNF1 and CNF2

The serogroups of 396 necrotizing Escherichia coli of human and bovine origin isolated in Spain between 1979 and 1991 have been determined. The 270 cytotoxic necrotizing factor strains belonged to 22 different O serogroups; however, 84% (226 of 270) were of one of seven serogroups (O2, O4, O6, O14, O22, O75 and O83). Although necrotizing E. coli producing cytotoxic necrotizing factor 2 belonged to 28 different serogroups, only six of them (O1, O3, O15, O55, O88 and O123) accounted for 60% (76 of 126) of cytotoxic necrotizing factor 2 strains. Furthermore, only 3% (4 of 126) of cytotoxic necrotizing factor 2 strains belonged to serogroups most common among strains producing cytotoxic necrotizing factor 1. The majority of necrotizing E. coli producing cytotoxic necrotizing factor 1 were obtained from human extraintestinal infections, whereas cytotoxic necrotizing factor 2 strains were isolated from stools of healthy and diarrhoeic calves.

[Escherichia coli virulence factors causing peritonitis, appendicitis and other extraintestinal infections]

Fifty-nine E. coli strains isolated from clinical cases of peritonitis, appendicitis, cholecystitis, wounds and respiratory infections as well as from other miscellaneous sources were investigated. A control group constituted by 475 E. coli strains isolated from the faeces of healthy individuals were also studied. E. coli O-grouped and investigated for production of cytotoxic necrotizing factor CNF1 and alpha-haemolysin (Hly), expression of P fimbriae and mannose-resistant (MRHA) and mannose-sensitive (MSHA) haemagglutination. Virulence factors significantly associated with extraintestinal strains were: production of CNF1 (19% versus 5%, p < 0.001), Hly (27% versus 9%; p < 0.001) and expression of MRHA (44% versus 16%; p < 0.001). The majority of extraintestinal strains (68% versus 36%; p < 0.001), in contrast with faecal E. coli, belonged to O serogroups frequently detected in uropathogenic and bacteraemic E. coli. These results suggest that E. coli causing different types of extraintestinal infections show similar virulence factors and belong to the same serogroups. However, between E. coli isolated from intraabdominal, wound and respiratory infections the number of strains with virulence factors was lower than in E. coli causing urinary tract infections and sepsis.

Enterotoxigenic and necrotizing Escherichia coli in human diarrhoea in Spain

Enterotoxigenic Escherichia coli (ETEC) strains of serotype 0153: K-:H45 CFA/I+ STa+ were associated with two outbreaks of neonatal diarrhoea that occurred in two different hospitals of Madrid, in one of which several children died. Two other outbreaks were associated with ETEC strains of serotypes 0159: K-:H21 (LT+) and 0159: K-:H4 (LT+ STa+) without CFA/I and CFA/II colonization factors. Necrotizing E. coli (NTEC) strains of serotype 06:K13, producing the cytotoxic necrotizing factor CNF1 and alpha-haemolysin, were also associated with two outbreaks of neonatal diarrhoea that occurred in a hospital in Madrid and in a hospital in Talavera de la Reina. The results of the characterization of some ETEC and NTEC strains isolated from sporadic cases of diarrhoea are also discussed.

Bovine Escherichia coli of serotypes O55:H4 and O55:H21 which produce CNF2 express P fimbriae and Vir surface antigen, respectively

We have characterized the toxic and adhesive properties of Escherichia coli strains producing the second type of cytotoxic necrotizing factor (CNF2) and belonging to the classic enteropathogenic serogroup O55. Bovine CNF2 strains of serotype O55:H4 express P fimbriae as do pyelonephritic Escherichia coli that cause infections in humans. In contrast, strains of serotype O55:H21 which produce CNF2 from bovine origin possess the Vir surface antigen. One human strain of serotype O55:H- was positive for production of CNF2, but was negative for the two adhesive factors and for mannose-resistant haemagglutination.

Fibronectin binding by Salmonella strains: evaluation of a particle agglutination assay

Thirty-five Salmonella strains isolated from human cases of salmonellosis were tested and compared for their fibronectin (fn) binding capacities by using two fn-particle agglutination assays (fn-PAAs) prepared by coating with human fn either (i) latex beads (Difco; 0.81-micron diameter) (L-fn-PAA) or (ii) heat-killed formalin-treated Staphylococcus aureus Cowan 1 cells (C-fn-PAA). Six S. aureus strains were also included in this study as controls. The strains were cultured on colonization factor antigen agar and blood agar and in tryptic soy broth and brain heart infusion broth. The Salmonella and S. aureus strains were cultured at 33 and 37 degrees C, respectively, for optimal expression of fn-binding proteins. Bacterial cells (approximately 10(10) cells per ml) harvested from growth in various culture media and suspended in 0.02 M potassium phosphate buffer (pH 6.8) agglutinated the fn-PAA reagents. These reactions were scored semiquantitatively from + to + depending on the speed or intensity of the reactions within 2 min. Maximum agglutination in fn-PAA systems was observed when the cells were grown in brain heart infusion broth, while tryptic soy broth proved to be least suitable media for culturing cells for fn-PAAS. Although a statistically highly significant correlation was obtained between results of assays of radiolabeled fn and 29-kDa fragment binding, no significant correlation was observed (i) between the results of strains cultured in different media or (ii) when semiquantitative score results of the two fn-PAA systems were compared with those of the conventional radiolabeled fn assay. To enhance the efficiency of the test system, the C-fn-PAA reagent was stained with methylene blue (2% in 0.17 M glycine-NaOH buffer [pH 6.8]). This facilitated easy interpretation of results, which could be performed on hydrophobic paper instead of glass slides. The results obtained with both unstained C-fn-PAA and stained C-fn-PAA were comparable to each other and reproducible. Although the fn-PAAs are simple and easy to perform, the results did not differentiate between negative, low, moderate, and high binding abilities when Salmonella strains were evaluated for fn binding, and the results were not comparable to those obtained by the conventional radiolabeling method.

Enterotoxins, colonization factors and serotypes of enterotoxigenic Escherichia coli from humans and animals

Enterotoxigenic Escherichia coli (ETEC) strains may synthesize both thermolabile (LT-I and LT-II) and thermostable (STa and STb) enterotoxins. Whereas thermolabile enterotoxins are high molecular weight proteins (85,000 d-90,000 d) composed by a single enzymatic A subunit combined with five B subunits which enable toxin for the receptor recognition, thermostable enterotoxins are small peptide chains with molecular weight between 1,900 d and 5,000 d. In addition to the synthesis of enterotoxins, the ability of ETEC strains to cause diarrhoea is also conditioned by the possession of colonization factors which enable bacteria adhere-to and colonize the luminal surface of small bowel. Colonization factors in ETEC strains were located in rigid fimbriae and flexible fibrils constituted by protein subunits ranging in size from 14,500 d to 31,000 d and usually responsible for mannose-resistant haemagglutination with determined erythrocyte species. Both enterotoxins and colonization factors are controlled by plasmids. There exist plasmids which may code separately enterotoxins and colonization factors, and besides there also exist recombinant plasmids coding together these two virulence factors. Human ETEC strains may synthesize LT-I and/or STa enterotoxins, they may possess the colonization factors named CFA/I, CFA/II, CFA/III or CFA/IV, and they belong mainly to serogroups O6, O8, O15, O20, O25, O27, O63, O77, O78, O114, O115, O126, O128, O139, O148, O153, O159 and O167. ETEC strains from porcine origin synthesize LT-I, STa and/or STb, they possess the colonization factors K88, P987, K99 or F41, and they usually belong to serogroups O8, O9, O20, O45, O64, O101, O115, O138, O141, O147, O149 and O157. Bovine and ovine ETEC strains are usually STa producers harbouring on the bacterial surface K99 or F41 colonization factors and they belong to serogroups O8, O9 and O101. Nevertheless, some particular bovine ETEC strains synthesizing LT-II have been described. Thus, a high specificity level between ETEC strains causing diarrhoea in humans and domestic animals can be observed. This is mainly due to the specific recognition between bacterial colonization factors and the epithelial receptors during host-parasite interaction.

Enterotoxigenic Escherichia coli associated with infant diarrhoea in Galicia, north-western Spain

To assess the role of enterotoxigenic Escherichia coli (ETEC) in infantile diarrhoea, 482 children with diarrhoea and 103 healthy controls, from three localities of Galicia, north-western Spain, were investigated between 1985 and 1988. Rotavirus (37.3%) and Salmonella spp. (12.8%) were the most common causal agents, followed by ETEC (3.9%), Campylobacter jejuni (2.3%), Shigella spp. (0.9%) and Yersinia enterocolitica (0.5%). ETEC were significantly more frequently isolated from children with diarrhoea who were under 1 month of age (26.5%) than from older diarrhoeic children (2.2%) (p less than 0.001) or from healthy children who were under 1 month of age (0%) (p less than 0.05). Among children who harboured ETEC, five of the nine children under 1 month of age developed diarrhoea in hospital, whereas none of the 10 children over 1 month of age did so. Seventeen ETEC isolates produced heat-stable enterotoxin (STa) only, four produced only heat-labile enterotoxin (LT), and two produced both toxins. Colonisation factor antigens CFA/I and CFA/II were detected in 11 (55.0%) of the 20 ETEC isolates that remained enterotoxigenic after maintenance in the laboratory. Most ETEC isolates belonged to serotypes O153:K-:H45 (nine STa+ CFA/I+ isolates), O27:K-:H7 (three STa+ isolates) or O6:K15:H16 (two LT+ STa+ CFA/II+ isolates). Our results suggest that ETEC constitute an important cause of neonatal diarrhoea in this part of Spain.

Comparative evaluation of three tests for the detection of Escherichia coli cytotoxic necrotizing factors (CNF1 and CNF2) using filtrates of cultures treated with mitomycin C

Necrotizing Escherichia coli (NTEC) strains grown in the presence of mitomycin C released cell associated necrotizing factors CNF1 and CNF2 to culture medium. Using culture filtrates from 96 mitomycin C treated E. coli strains, we have found that a modified HeLa cell assay was a more sensitive and specific method for the detection of CNF1 and CNF2 than the Vero cell assay and the rabbit skin test.

Evidence for two types of cytotoxic necrotizing factor in human and animal clinical isolates of Escherichia coli

We have characterized the in vitro and in vivo toxic properties of cell sonic extracts from 22 animal and human clinical isolates of Escherichia coli that caused both necrosis in the rabbit skin and multinucleation in tissue cultures, two toxic properties previously reported as being specific for E. coli cytotoxic necrotizing factor (CNF). Two distinct toxic phenotypes were observed. Type 1, which was displayed by originally described CNF strains, was characterized by extensive multinucleation and rounding of cells in HeLa cell culture assays, moderate necrosis in the rabbit skin test, and absence of necrosis in the mouse footpad test. Type 2, which has recently been shown to be associated with E. coli Vir plasmid, was characterized by moderate multinucleation, by polymorphism and elongation of HeLa cells, and by an intense necrotic response in both the rabbit skin test and the mouse footpad test. The distinction between the two cytotoxins accounting for these effects (CNF 1 and CNF 2), together with their partial relatedness, was confirmed by seroneutralization studies of both cytopathic effects and necrosis in the rabbit skin test. In addition, type 2 extracts were more lethal in the mouse intraperitoneal test and induced a moderate, although not totally repetitive, fluid accumulation in the ileal loop test. The original toxic properties of these recently recognized categories of E. coli strains, together with their association with enteritis and septicemia, suggest that these strains may play a significant role in pathology.

Surface and virulence properties of environmental Vibrio cholerae non-O1 from Albufera Lake (Valencia, Spain)

A total of 140 environmental Vibrio cholerae non-O1 isolates, together with several culture collection strains from both environmental and clinical sources, were studied in relation to hemagglutination, surface hydrophobicity, and the enzymatic, hemolytic, cytotoxic, and enterotoxic activities of their extracellular products. A total of 78 and 62% of the strains produced hemagglutinins and exohemagglutinins, respectively. Four different hemagglutinating and two exohemagglutinating activities were found by using eight sugars in the inhibition assays. Cell-bound mannose-sensitive hemagglutination was detected mainly in chicken blood, whereas fucose-sensitive hemagglutination was recorded only in human blood. Cell-bound hemagglutinin resistant to all sugars tested was the only one related to surface hydrophobicity. The surface properties varied along the growth curves. The non-O1 strains displayed strong enzymatic and hemolytic activities, except for esculin hydrolysis. Of 26 non-O1 isolates selected for cytotoxin and enterotoxin production, 23 showed a wide spectrum of cytotoxic effects on cell lines of poikilothermic and homoiothermic species, but they were weakly enterotoxigenic in the infant mouse test. All extracellular products of cytotoxic strains were proteolytic, lipolytic, and hemolytic, and a high percentage produced hemagglutination of chicken blood. The cytotoxic factors in the non-O1 strains analyzed were not R plasmid mediated.

Virulence factors of bacteraemic Escherichia coli with particular reference to production of cytotoxic necrotising factor (CNF) by P-fimbriate strains

Thirty-seven strains of Escherichia coli isolated from bacteraemia and 40 faecal strains isolated from healthy individuals were O serogrouped and investigated for the production of colicins, haemolysin (Hly), cytotoxic necrotising factor (CNF), lethal activity for mice, the expression of P fimbriae, mannose-resistant (MRHA) and mannose-sensitive (MSHA) haemagglutination, and relative cell surface hydrophobicity. Virulence factors significantly associated with bacteraemic strains were: serogroups O2, O4, O6, O7, O8 and O75 (54% versus 10%, p less than 0.001), production of Hly (32% versus 8%, p less than 0.02) and CNF (38% versus 10%, p less than 0.01), expression of P fimbriae (27% versus 5%, p less than 0.02), MRHA types III, IVa and IVb (51% versus 8%, p less than 0.001), and possession of a moderate cell surface hydrophobic charge (35% versus 13%, p less than 0.05). Virulence factors were strongly associated with strains expressing defined MRHA types. Thus, all strains belonging to MRHA types III and IVa were toxigenic, whereas only 11% of strains belonging to MRHA types IVb, V or VI were toxigenic (p less than 0.001). Virulence factors were concentrated in strains belonging to O serogroups usually found in E. coli that cause extra-intestinal infections, especially in strains of O4 and O6 groups. The most interesting result of this study was that all 12 P-fimbriate strains expressed the MRHA type IVa and 11 of them synthesised CNF.

Enterotoxic, cytotoxic, necrotic and lethal activities in cell-free extracts of Salmonella strains isolated from humans

Unconcentrated cell-free sonic extracts from thirty Salmonella strains isolated from the faeces and blood of humans were investigated for the production of enterotoxins in various tests (Vero cell, infant mouse, rabbit skin permeability and rabbit ileal loop), as well as for lethal activity in adult mice. Sonic extracts from 23 (76.7%) strains were lethal for mice, 21 (70%) increased skin permeability and 3 (10%) showed necrotizing activity for the rabbit skin. No Salmonella strain producing typical Escherichia coli toxins, such as thermolabile (LT) or thermostable (STa) enterotoxins, Verotoxin (VT) or cytotoxic necrotizing factor (CNF) cytotoxins, were detected. Non-repetitive fluid accumulation in rabbit loops was obtained when unconcentrated sonic extracts from 10 selected strains were assayed in seven rabbits. Growth of Salmonella in casamino acid yeast extract medium, followed by treatment of bacterial cells with polymyxin B, was demonstrated to be a rapid and sensitive method for releasing the delayed permeability factor.

Serotypes and antibiotic resistance of verotoxigenic (VTEC) and necrotizing (NTEC) Escherichia coli strains isolated from calves with diarrhoea

Serotypes and antibiotic resistance of 51 Verotoxigenic (VTEC) and 33 Necrotizing (NTEC) bovine Escherichia coli strains were determined and compared with those shown by 205 non-VTEC non-NTEC strains isolated from the same batch of calves. E. coli untypable for O-antigen represented 47% of the VTEC, 12% of the NTEC and 8.8% of the non-VTEC non-NTEC. Typable VTEC belonged to serotypes 02:K?, 0103:K-, 0104:K?, 0128:K?, 0153:K- and O157:K-:H7, whereas typable NTEC were of serotypes 08:K87, 015:K14, 015:K-, 054:K?, 076:K-, 078:K(80), 088:K?, 0123:K-, 0139:K- and 0153:K-. Non-VTEC non-NTEC showed a wide variety of serotypes which were generally unrelated to those found in VTEC and NTEC. VTEC were resistant to antibiotics at higher rates than NTEC and non-VTEC non-NTEC, and showed also the highest multidrug-resistant pattern. Our results show that bovine VTEC strains belonged to O-groups usually found in human VTEC causing sporadic diarrhoea, haemorrhagic colitis and/or haemolytic uraemic syndrome, such as 02, 0103, 0104, 0153 and especially 0128 and O157. In contrast, bovine NTEC strains belonged to serotypes different from those previously found in necrotizing E. coli strains of human origin.

Prevalence of enterotoxigenic Escherichia coli strains in outbreaks and sporadic cases of diarrhoea in Spain

Escherichia coli strains isolated 1985-1988 in Spain from patients with diarrhoea were examined; 1170 strains were isolated from 582 sporadic cases of diarrhoea in children, and seven strains were associated with seven outbreaks of diarrhoea. Strains positive for STa enterotoxin production in the infant mouse test were also assayed for production of LT enterotoxin on Vero cells and by a coagglutination test. Thirty-one strains were STa positive: 28 were isolated from 16 (2.7%) sporadic cases of diarrhoea and three were responsible for outbreaks. The majority of STa+LT- strains from both outbreaks and sporadic cases were serotype O153:H45 and expressed the CFA/I colonization factor antigen. Enterotoxigenic STa+LT- strains of serotype O27:H7 and STa+LT+ CFA/II+ strains of serotype O6:K15:H16 were also isolated frequently from sporadic cases.

Production of toxins by Escherichia coli strains isolated from calves with diarrhoea in galicia (north-western Spain)

A total of 289 Escherichia coli colonies isolated from 78 diarrhoeic calves were studied for production of heat-labile (LT) and heat-stable (STa) enterotoxins, verotoxin (VT), cytotoxic necrotizing factor (CNF) and K99 antigen, and they were serotyped. Production of STa was detected in a single strain possessing both K99 and F41 antigens; the serotype was 09:K (A) 35. LT-producing strains were not detected. From 16 (20.5%) calves, 51 VT-producing colonies of E. coli were isolated. Production of the necrotic factor was detected in 33 E. coli colonies isolated from 14 (17.9%) calves. Serotype was a useful marker for production of VT and CNF. Among the 51 VT-producing colonies, 24 were untypable and the remainder belonged to serotypes O2:K?, O103:K--, O104:K?, O128:K?, O153:K-- and O157:K--:H7. Four of the 33 CNF-producing colonies were untypable and the majority of the remaining colonies belonged to serotypes O15:K14, O78:(K80), O123:K-- and O139:K--. Both VT and CNF were lethal for mice, but only CNF showed necrotizing reaction in rabbit skin. Our results indicate that VT-producing and CNF-producing E. coli strains are frequently isolated from diarrhoeic calves and that according to the serotypes exhibited, some of them might be considered potential pathogens for humans. The role of VT-producing and CNF-producing strains in calf diarhoea remains to be established.

Growth conditions for the expression of fibronectin and collagen binding to Salmonella

Binding of 125I-fibronectin, its 125I-labelled 29-kDa aminoterminal fragment, and 125I-collagen to cells of 13 Salmonella strains grown in broth and agar media at three different temperatures was studied. Of the 13 strains, 7 had only smooth colony morphologies while three strains were pairs of both smooth strains and their corresponding rough variants. The three rough variants showed higher binding to fibronectin, it's 29-kDa fragment and to collagen, than the corresponding smooth forms. However, the percentage of 125I-protein bound was greatly influenced by the growth conditions. In these three pairs of strains, there was a direct correlation between cell-surface hydrophobicity and the binding activity, but this correlation was not observed in the remaining strains. Thus, some of the strains showed high cell-surface hydrophobicity but low binding activity under optimal growth conditions. The highest binding rates of fibronectin and of it's 29-kDA fragment were obtained with bacteria grown on colonisation factor antigen (CFA) agar at 33 degrees C, while the binding to collagen was slightly higher when bacteria were cultured on tryptic soy agar.

Relation between antibiotic resistance and number of plasmids in enterotoxigenic and non-enterotoxigenic Escherichia coli strains

We have investigated the relation between antibiotic resistance and the number of plasmids contained in 44 enterotoxigenic (ETEC) and 69 non-enterotoxigenic (non-ETEC) Escherichia coli strains. Both ETEC and non-ETEC strains were resistant to one or more antibiotics at a similar rate, but multiple resistance in resistant non-ETEC strains was higher than in resistant ETEC strains, showing a significant difference (P less than 0.001) when subjected to Student's t test. Among the ETEC strains, those producing both LT and STa enterotoxins were more sensitive to antibiotics than strains producing only a single toxin type. On the other hand, resistant ETEC strains possessed a higher number of plasmids per strain than the resistant non-ETEC strains (P less than 0.05 by Student's t test). Consequently, resistance to antibiotics could not be related to the possession of a higher number of plasmids. Furthermore, our results support the hypothesis that there is a generalized incompatibility process between plasmids which code for antibiotic resistance and plasmids which code for enterotoxin production in ETEC strains, at least in those strains producing both LT and STa enterotoxins.

Colonization antigens and haemagglutination patterns of human Escherichia coli

The haemagglutinating properties of 223 (35 enterotoxigenic and 188 non-enterotoxigenic) Escherichia coli strains with nine erythrocyte types were investigated; 153 strains were also tested for beta-haemolysis and colicin production and for the presence of CFA/I, CFA/II, K88 and K99 antigens. A selected group of strains was also examined by electron microscopy to determine the presence of fimbriae or fibrils and to establish the relationship between these, the haemagglutinating properties and the presence of colonization antigens. Generally, the haemagglutinating patterns yielded by the same strains grown in Mueller Hinton broth and on CFA agar differed considerably. Mannose-sensitive haemagglutinating (MSHA) patterns were more homogeneous than mannose-resistant haemagglutinating (MRHA) patterns. Forty-seven percent of the non-enterotoxigenic MRHA+ strains were haemolytic while only 6% of the remaining strains were (chi2 correction = 34.01; p less than 0.001). CFA/I was only detected in the four enterotoxigenic MRHA+ strains which were positive only with human and calf erythrocytes when grown on CFA agar. CFA/II was detected in three of a total of six enterotoxigenic strains which were MRHA+ only with calf erythrocytes when grown on CFA agar. K88 and K99 antigens were not detected. All strains in which bacteria with fimbriae or fibrils were observed showed haemagglutinating activity. Thus, 18 (66.7%) of the 27 haemagglutinating strains grown on CFA agar showed fimbriae or fibrils while none of the 19 non-haemagglutinating strains did (chi2 correction = 18.10; p less than 0.001).

Enterotoxigenic and enteropathogenic Escherichia coli in Galicia (north-west Spain)

We have studied the incidence of enterotoxigenic and enteropathogenic Escherichia coli strains associated with infant diarrhoeal disease in Galicia (North-west Spain). During a period of 9 months we isolated heat-labile enterotoxin-positive strains in 2.1% of children with diarrhoea examined, whereas the production of heat-stable enterotoxin was detected in 1.1% of them. Enteropathogenic strains were isolated from 5.3% of the children with diarrhoea, but none of these strains released heat-labile or heat-stable enterotoxins.

[Limiting amino acids of chickpeas (Cicer arietinum) for chickens and pigs]

Three experiments, two with broilers and one with pig, were conducted to determine the limiting amino acids of chickpea (Cicer arietinum). In the first 15% protein diets based on autoclaved chickpea were supplemented with methionine (0.20%), either alone or combined with threonine (0.025%) with no significant effect on growth or feed convertion of chicks; however, the addition of methionine tended to improve both parameters in relation to the unsupplemented diet. In the second experiment methionine (0.20%) and/or tryptophan (0.03%) were added to 15% protein diets based on either raw or autoclaved chickpeas. Cooking improved growth and feed efficiency in relation to the raw controls (P less than .05); methionine supplementation was beneficial for both raw and autoclaved diets (P less than .01); the addition of tryptophan was favourable only for the cooked chickpeas. A third experiment was conducted with weanling pigs to study the effect of methionine supplementation to sorghum-chickpea diets with 14 and 12% protein. In both cases, the addition of the sulphur amino acid improved growth and efficiency to the levels obtained with a 15.34% protein sorghum-soybean meal control.