Detection of Shiga toxin-producing Escherichia coli by PCR in cattle in Argentina. Evaluation of two procedures

Different experimental approaches were evaluated for their ability to detect stx genes by PCR and identify Shiga toxin-producing Escherichia coli (STEC) in bovine fecal samples. One hundred and sixty fecal samples from steers in Argentina were processed by protocols that involved: (1) enrichment of fecal samples and DNA extraction using a commercially available kit (Protocol A); (2) plating on selective media after enrichment of the fecal sample followed by heat-lysis DNA extraction from the confluent growth zone (Protocol B); (3) analysis of individual colonies isolated from direct fecal culture on MacConkey agar and sorbitol MacConkey agar supplemented with cefixime and potassium tellurite (Protocol C), used as Gold Standard. PCR performed on bacteria from the confluent growth zone (Protocol B) proved to be the most sensitive methodology. In addition, enrichment for greater than 6h, enhanced sensitivity. Among eight STEC isolates, four were O8:H19 and four were stx2/eae-negative. An STEC isolate was characterized as O26:H11 with a stx1/eae/EHEC-hlyA genotype, often associated with human disease. Finally, no STEC O157 strains were isolated using these methods.

[Biomedical images segmentation by the regions growth method]

The study of the different fiber types present in muscle tissue sample images allows the investigators to identify some metabolic and contractile muscle properties, and in general, its physiological state. The image segmentation, which identifies regions or contours of objects within the image, is a fundamental step of the on-line image analysis that can help in this study. However, this kind of images, in general, are very diffuse and with low contrast, so it is difficult to identify the different objects within the image. The main objective of this work is to propose a two-phase method for segmentation of digitized images of cross sections of rat muscle tissue. The first phase allows obtaining an initial group of homogeneous regions by using a uniformity criterion. In this phase we use a division and union of regions algorithm. The purpose of the second phase is to group together in an image the regions corresponding to a given fiber type. The results obtained show an appropriate identification of the regions of interest on the images studied.

[Isolation and characterization of Shiga-toxin-producing Escherichia coli from frozen hamburgers and soft cheeses]

Shiga toxin producing-Escherichia coli (STEC), an important emerging foodborne pathogen, has been associated with bloody and non-bloody diarrhea, hemorrhagic colitis, hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura. The cattle have been shown to be a major reservoir of STEC and raw foods such as ground beef and milk are the most common vehicles of infection. In the present study, the prevalence of STEC in 95 samples of frozen hamburgers and in 114 samples of soft cheese was established in 8.4% and 0.9%, respectively. The genotypic and phenotypic characteristics of the strains were determined. The virulence genes stx1, stx2, eaeA and EHEC-hlyA were identified by PCR and by colony blot hybridization assays. Serotyping, antimicrobial susceptibility and production of Stx using specific cytotoxicity assays on Vero cells were also determined. All STEC strains were characterized as eaeA-/EHEC-hlyA+. The stx2 genotype was prevalent (77.8%), and four different O:H serotypes were found, comprising: O8:H19 (5 strains), O113:H21 (1), O8:H16 (1), and O39:H49 (1). One STEC strain was nontypable. Although soft cheese complimented the microbiological quality controls for the coliform counts, the detection of STEC in one sample raises doubts concerning the effectiveness of the current quality controls. These data contribute to the implementation of strategies for the prevention and control of HUS.

Isolation and characterization of Escherichia coli O157:H7 from retail meats in Argentina

Between February and May 2000, 279 meat samples were collected from 136 retail stores in Gualeguaychú City, Argentina. Samples were assayed for Escherichia coli O157:H7 by selective enrichment in modified EC broth containing novobiocin, followed by immunomagnetic separation (IMS) and plating onto both sorbitol MacConkey agar supplemented with cefixime and potassium tellurite and a chromogenic medium. Eleven E. coli O157:H7 isolates were detected in 6 (3.8%) of 160 ground beef samples, in 4 (4.8%) of 83 fresh sausages, and in 1 (3.3%) of 30 dry sausages. E. coli O157:H7 was not isolated from five hamburger patties or one barbecue-type fresh sausage assayed. The isolates were tested for virulence-related genes. Ten additional Shiga toxin-producing E. coli (STEC) O157:H7 isolates of food origin, recovered from different locations in Argentina, were included for comparison purposes. All 21 isolates harbored both eae and EHEC-hlyA genes, and 12 (57.1%) encoded stx2/stx2vh-a. The isolates were of phage types 87 (seven strains), 14 (four strains), 4 (three strains), and 26 (one strain). Six strains were nontypable by phage typing. Pulsed-field gel electrophoresis (PFGE) revealed 19 XbaI-PFGE profiles. Fifteen (71%) strains were grouped in four clusters, which shared more than 80% of DNA restriction fragments. The enrichment culture method with IMS was a sensitive procedure to detect E. coli O157:H7 strains in retail meats. Some of the isolates from different stores presented a high clonal relatedness, as determined by XhaI-PFGE and phage typing, and harbored the virulence factors associated with human illness.

Intestinal bleeding and occlusion associated with Shiga toxin-producing Escherichia coli O127:H21

We report a case of a nine-year old boy with vomiting, abdominal pain and fever, who underwent surgery with a diagnosis of appendicitis in Mendoza and from whom a Shiga toxin-producing Escherichia coli (STEC) O127:H21 strain was recovered. Forty-eight hours after surgery he presented bilious vomiting and two episodes of intestinal bleeding. Laboratory findings included: hematocrit, 35%; blood urea nitrogen, 0.22 g/L. The urinary output was normal. The following day physical examination showed an alert mildly hydrated child, without fever but with distended and painful abdomen. The patient was again submitted to surgery with a diagnosis of intestinal occlusion. Bleeding and multiple adhesions in jejunum and ileum were found. The patient still had tense and painful abdomen and presented two bowel movements with blood; hematocrit fell to 29% and blood urea nitrogen rose to 0.32 g/L. STEC O127:H21 eae(-)/Stx2/Stx2vh-b(+)/E-Hly(+) was isolated from a stool sample. He was discharged after 10 days of hospitalization and no long-term complications such as HUS or TTP were observed. This is the first report, to our knowledge, on the isolation of E. coli O127:H21, carrying the virulence factors that characterize STEC strains, associated to an enterohemorrhagic colitis case. This serotype was previously characterized as a non-classic enteropathogenic E. coli (EPEC). STEC infections can mimic infectious or noninfectious pathologies. Therefore an important aspect of clinical management is making the diagnosis using different criteria thereby avoiding misdiagnoses which have occasionally led to invasive diagnostic and therapeutic procedures or the inappropriate use of antibiotics.

[Isolation of Escherichia coli O157:H7 in storm drains in the city of Mar del Plata with bacterial contamination of fecal origin]

The present study was focused on the isolation and characterization of Escherichia coli, particularly the serotype O157:H7, from five combined-sewer outflows waters, which drain into the beaches of Mar del Plata. Seventeen hemolytic uremic syndrome cases were reported in Mar del Plata during the sampling period (May 1995-April 1996) in children between 9 month- and 5 year-old, and 3 deaths were recorded. E. coli identification was carried out by biochemical tests. E. coli was detected in 75% of the samples and a total of 98 strains were selected, with 11 sorbol non-fermenting strains. The strains belonged to the O1, O6, O44, O86a, O119 and O168 serogroups. As none of the known virulence factors was detected, strains could not be grouped within any of the diarrheagenic E. coli categories. None of the E. coli strains belonged to the O157:H7 serotype, but E. coli isolation showed fecal contamination in the combined-sewer outflows. Since their waters drain into beaches for recreational use, it is necessary to emphasize the detection of E. coli that would cause severe human illness. Bacterial pollution in combined-sewer outflows draining into Mar del Plata coasts might represent a high risk for human health.

Effect of Shiga toxin 2 on water and ion transport in human colon in vitro

Shiga toxin-producing Escherichia coli (STEC) colonize the lower segments of the human gastrointestinal tract, causing gastrointestinal and systemic diseases. In this study, the effects of Shiga toxin 2 (Stx2) on fluid absorption and ion transport in the human colon were examined. Net water movement (Jw) and short-circuit current (Isc) were simultaneously measured across the colonic mucosa incubated with crude or purified Stx2. Stx2 significantly inhibited the absorptive J(w) with no effect on the basal I(sc) after 60 min of exposure. These effects may be due to the inhibition of a nonelectrogenic transport system present in the surface colonic villus cells. Morphological studies of the colonic mucosa treated with crude or purified Stx2 demonstrated a selective damage in the absorptive villus epithelial cells. These findings suggest that Stx2 inhibits water absorption across the human colon by acting on a specific cell population: the mature, differentiated absorptive villus epithelium.

Biochemical characterization and inhibitory effects of dinophysistoxin-1, okadaic acid and microcystine l-r on protein phosphatase 2a purified from the mussel Mytilus chilensis

Protein phosphatases are involved in many cellular processes. One of the most abundant and best studied members of this class is protein phosphatase type-2A (PP2A). In this study, PP2A was purified from the mussel Mytilus chilensis. Using both SDS-PAGE and size exclusion gel filtration under denaturant conditions, it was confirmed that the PP2A fraction was essentially pure. The isolated enzyme is a heterodimer and the molecular estimated masses of the subunits are 62 and 28 kDa. The isolated PP2A fraction has a notably high p-NPP phosphatase activity, which is inhibited by NaCl. The hydrolytic p-NPP phosphatase activity is independent of the MgCl2 concentration. The time courses of the inhibition of the PP2A activity of p-NPP hydrolysis by increasing concentrations of three phycotoxins that are specific inhibitors of PP2A are shown. Inhibitions caused by Okadaic acid, dinophysistoxin-1 (DTX1, 35-methylokadiac acid) and Microcystine L-R are dose-dependent with inhibition constants (Ki) of 1.68, 0.40 and 0.27 nM respectively. Microcystine L-R, the most potent phycotoxin inhibitor of PP2A isolated from Mytilus chilensis with an IC50 = 0.25 ng/ml, showed the highest specific inhibition effect an the p-NPP hydrolisis. The calculated IC50 for DTX1 and OA was 0.75 ng/ml and 1.8 ng/ml respectively.

Pretreatment of mice with lipopolysaccharide (LPS) or IL-1beta exerts dose-dependent opposite effects on Shiga toxin-2 lethality

Haemolytic uraemic syndrome (HUS) has been closely associated with infection with a group of Shiga toxin-producing enterohaemorrhagic Eschericchia coli in young children. Shiga toxins (Stx) have been implicated as pathogenic agents of HUS by binding to the surface receptor of endothelial cells. LPS is a central product of the Gram-negative bacteria and several reports have documented that both LPS and Stx are important for disease development. In this study the reciprocal interactions between LPS and Stx2 are analysed in a mouse model. The results demonstrated that LPS was able to reduce or enhance Stx2 toxicity, depending on the dose and the timing of the injection. The involvement of the main early cytokines induced by LPS, tumour necrosis factor alpha (TNF-alpha) and IL-1beta, in those LPS opposite effects on Stx2 toxicity was evaluated. Stx2 toxicity was enhanced by in vivo injection of murine TNF-alpha and low doses of murine IL-1beta. However, at higher doses of IL-1beta which induced corticosteroid increase in serum, Stx2 lethality was decreased. Considering that dexamethasone and IL-1beta reproduce the LPS protective effects, it is suggested that endogenous corticosteroids secondary to the inflammatory response induced by LPS, mediate the protection against Stx2. It can be concluded that the fine equilibrium between proinflammatory and anti-inflammatory activities strongly influences Stx2 toxicity.

Asymptomatic infections by diarrheagenic Escherichia coli in children from Misiones, Argentina, during the first twenty months of their lives

Diarrheagenics Escherichia coli are the major agents involved in diarrheal disease in developing countries. The aim of this study was to evaluate the time of appearance of the first asymptomatic infection by the different categories of diarrheagenic E. coli in 44 children since their birth and during the first 20 months of their lives. In all of the children studied, we detected at least one category of diarrheagenic E. coli through the 20 months of the study. 510 diarrheagenic E. coli (33.5%) were obtained from the 1,524 samples collected from the 44 children during the time of the study (31.4% EAggEC, 28.8% EPEC, 27.1% DAEC, and 12.7% ETEC). Neither EHEC nor EIEC were identified. The median age for diarrheagenic E. coli colonization was 7.5 months. The mean weaning period was 12.8 months and the mean age for introduction of mixed feeding (breast fed supplemented) was 3.8 months. A significantly lower incidence of diarrheal disease and asymptomatic infections was recorded among the exclusively breast-fed rather than in the supplemented and non breast-fed infants. For ETEC, EPEC and EAggEC the introduction of weaning foods and complete termination of breast-feeding were associated with an increase of asymptomatic infections.

Prospective cohort study of enterotoxigenic Escherichia coli infections in Argentinean children

In a follow-up study, enterotoxigenic Escherichia coli (ETEC) infections in 145 children from two communities located in northeastern Argentina were monitored for 2 years. The occurrence of diarrhea was monitored by weekly household visits. Of 730 fecal specimens collected, 137 (19%) corresponded to diarrheal episodes. ETEC was isolated from a significantly higher proportion of symptomatic (18.3%) than asymptomatic (13.3%) children (P = 0.04541). Individuals of up to 24 months of age were found to have a higher risk of developing ETEC diarrhea than older children (odds ratio [OR], 3.872; P = 0.00021). When the toxin profiles were considered, only heat stable enterotoxin (ST)-producing ETEC was directly associated with diarrhea (P = 0.00035). Fifty-five percent of the ETEC isolated from symptomatic children and 19% of the ETEC isolated from asymptomatic children expressed one of the colonization factors (CFs) investigated, i.e., CF antigen I (CFA/I), CFA/II, CFA/III, and CFA/IV; coli surface antigens CS7 and CS17; and putative CFs PCFO159, PCFO166, and PCFO20, indicating a clear association between diarrhea and ETEC strains that carry these factors (P = 0.0000034). The most frequently identified CFs were CFA/IV (16%), CFA/I (10%), and CS17 (9%). CFs were mostly associated with ETEC strains that produce ST and both heat-labile enterotoxin and ST. Logistic regression analysis, applied to remove confounding effects, revealed that the expression of CFs was associated with illness independently of the toxin type (OR, 4.81; P = 0.0003). When each CF was considered separately, CS17 was the only factor independently associated with illness (OR, 16.6; P = 0.0151). Most CFs (the exception was CFA/IV) fell within a limited array of serotypes, while the CF-negative isolates belonged to many different O:H types. These results demonstrate that some CFs are risk factors for the development of ETEC diarrhea.

[Antimicrobial resistance among species of Salmonella, Shigella, Escherichia, and aeromonas isolated from children with diarrhea in 7 Argentinian centers]

The increasing levels of resistance of enteropathogenic bacteria against antimicrobial agents present geographic variations. We have analysed the antimicrobial susceptibility of isolates obtained from 4,364 children under 5 years of age with acute diarrhea, in 7 cities of Argentina. Diarrheagenic E. coli exhibited 74.5% of resistance against ampicillin, 64.2% against sulfametoxazole-trimethoprim, and Shigella spp., 62% and 75.6% respectively. Salmonella sp. showed 35%, 14%, 41.8%, 65.4%, 14.5%, and 13.6% of resistance against ampicillin, chloranfenicol, sulfametoxazole-trimetoprim, sulfadiazin, gentamycin, and fosfomycin respectively. These values are higher than the ones observed in developed countries. Aeromonas showed significantly lower resistance percentage. Important differences in our country were observed, consequently, local trials should be carried out in order to apply corrective measures.

[Hemolytic uremic syndrome in children of Mendoza, Argentina: association with Shiga toxin-producing Escherichia coli infection]

Shiga toxin-producing Escherichia coli (STEC) has been associated with pathogenesis of hemolytic uremic syndrome (HUS) worldwide. The aim of the present study was to characterize the HUS cases reported in Mendoza and to determine their association with STEC infection. From July 1994 through June 1996 thirty-six patients with HUS were admitted to Hospital Pediátrico "Dr. HJ Notti" (Mean age 22.8 +/- 14.9 months, 44% females). The children developed HUS following an acute diarrheal illness in 94.4% of the cases. Bloody diarrhea was observed in 83.3% of them. Antimicrobial therapy had been administered to 69.4% of the patients. Most of the patients were well-nourished (88.9%), belong to middle-low socioeconomical condition (91.7%), from urban areas (72.2%) and they were mostly assisted during summer and the beginning of autumn. The acute stage of the disease occurred with presentation of pallor (100%), edema (25%), anuria (38.9%), oliguria (41.7%), hemolytic anemia (97.2%), thrombocytopenia (86.1%) and neurological involvement (41.7%). Twenty-five of them presented the full clinical syndrome. Peritoneal dialysis were performed in 50% and packed blood cell transfusion in 88.9%. The mean days of hospitalization was 15.1 +/- 9.2 [range 1-32]. A 91.7% of the patients recovered renal function, two developed chronic renal failure and one died. Cumulative evidence of STEC infection was found in 19 (86.4%) of 22 HUS patients. STEC O157:H7, biotype C was found in 8 (36.4%). The prevalent Stx type was Stx2 in STEC, free fecal Stx (STMF) and Stx-neutralizing antibodies (a-Stx). In Mendoza, as in the rest of Argentina E. coli O157:H7, biotype C, Stx2 producer is the most frequently detected pathogen in HUS cases.

Differential kinetic patterns for Shiga toxin production by Escherichia coli

We studied the differential kinetic patterns for Shiga toxin (Stx) production (i.e. Stx1, Stx2 and Stx2c) in different reference Escherichia coli strains and in those isolated from hemolytic uremic syndrome (HUS) patients. These results were correlated with those obtained by specific cytotoxic activity assays on Vero cells and hybridization tests with DNA probes for Stx1 and Stx2. Strains cultured in Penassay broth were sampled at 1.5; 3; 5; 9 and 24 hours to determine bacterial growth and its association with cell-bound and free cytotoxicity. Stx1 showed an intracellular/extracellular concentration ratio (ic/ec) between 32 and 200 times after 3 h-growth. At 24 h both Stx1 concentrations were equal or, in some strains, the ec resulted 2-fold higher that the ic. The ic-Stx1 was equal or just 2-fold higher that ec after 3 h-growth. However, at 24 h the released toxin level was 16 to 32 times higher that cell-bound toxin. The ec-Stx2c increased logarithmically, with maximal yields at 5 h, remaining constant up to 24 h. At that time ic-toxin was 2-fold higher than the released one. When the same experiments were performed on strains isolated from HUS patients they showed that the kinetic patterns obtained corresponded to Stx2. These results were confirmed by hybridization assays. In this study we have shown that Stx1 production decreases dramatically during stationary phase while Stx2 is detected at high level at that time. This could explain the higher frequency of association of Stx2-producing E. coli strains and HUS in some countries, including Argentina.

Synchronous pulmonary cryptococcosis and histoplasmosis

A chronically immunosuppressed patient receiving oral steroid therapy had a cavitary lesion; both Histoplasma capsulatum and Cryptococcus neoformans were found in samples of respiratory secretions. C neoformans was also found in specimens taken from skin lesions and blood. This is the first reported instance of synchronous infection by these two fungi.

Inactivity changed fiber type proportion and capillary supply in cat muscle

The effect of different levels of activity on fiber types, capillaries and enzymes of gastrocnemius and soleus muscles was studied in two groups of cats. The first group was successfully kept in a large room, exercised on a treadmill 15 min daily 5 days per week and kept in individual small cages. Each period lasted 6 weeks. A muscle biopsy was taken after each period. The second group was formed by cats that were caged for over 20 months. In the group caged for over 20 months, gastrocnemius muscle showed higher IIB and lower I fiber type proportion. Fiber cross-sectional area was not different in any condition. All capillary measurements were significantly lower in gastrocnemius muscle of long-term caged cats, and capillaries per mm2 were lower in soleus muscle of these cats. Exercise increased capillary/fiber in soleus muscle but subsequent caging did not reduced it. In soleus muscle, beta-hydroxy-acyl-CoA dehydrogenase levels decreased after the cage period and hexokinase levels increased after the exercise and decreased after the cage period. In conclusion, different levels of activity for short time produced enzyme changes in soleus muscle, whereas long-term inactivity changed fiber type proportion in gastrocnemius muscle and reduced capillary supply.

Bone loss and turnover after cardiac transplantation

Cardiac transplantation is associated with increased prevalence and incidence of fracture, and rapid bone loss has been reported during the first posttransplant year. To define further the pattern and etiology of bone loss after cardiac transplantation, we enrolled 70 patients (52 men and 18 women) in a prospective 3-yr study. Bone densitometry (BMD) and biochemical indexes of mineral metabolism were performed before and at defined times after transplantation. Despite supplementation with elemental calcium (1000 mg/day) and vitamin D (400 IU/day), the mean rate of bone loss during the first year was 7.3 +/- 0.9% (+/- SEM) at the lumbar spine and 10.5 +/- 1.1% at the femoral neck. The rate of bone loss slowed (P < 0.001 compared to year 1) at both sites (0.9 +/- 0.9% and 0.1 +/- 1.0%, respectively) during the second year. During the third year, lumbar spine BMD increased at a rate of 2.4 +/- 0.8%/yr (P < 0.02 compared to year 2), but femoral neck BMD did not change. At the radius, the rate of decline in BMD was negligible during the first year (0.9 +/- 0.5%), but was significant during the second (2.1 +/- 0.6%; P < 0.01) and third (2.9 +/- 0.8%; P < 0.03) years. Evaluation of the pattern of bone loss during the first year demonstrated that mean lumbar spine BMD decreased rapidly during the first 6 months, after which there was no further decline. In contrast, femoral neck BMD continued to fall at an annualized rate of 8.2 +/- 1.3% during the second half of the year. The pattern and rates of bone loss were similar in men and women. Biochemistries revealed decreases in serum testosterone and osteocalcin and increases in all bone resorption markers 1 and 3 months after transplantation, with a return to baseline by 6 months. Higher rates of bone loss were associated with greater exposure to prednisone, lower serum concentrations of vitamin D metabolites, greater suppression of osteocalcin, higher levels of bone resorption markers, and, in men, lower serum testosterone concentrations. We conclude that rapid bone loss is primarily confined to the initial year after transplantation. During the first 6 months, bone loss is accompanied by alterations in markers of bone turnover consistent with biochemical uncoupling of bone formation and resorption. Greater exposure to glucocorticoids, lower serum concentrations of vitamin D metabolites and testosterone, and higher bone turnover were associated with more rapid bone loss.

[Cases of gastroenteritis associated to Vibrio cholerae no 01 in Oran, Salta]

Forty-one sporadic cases of non-O group 1 Vibrio cholerae gastroenteritis were detected in Orán, Salta, between February 1992 and February 1995. The frequency of isolation was 0.9% of the diarrhea cases. Out of 41 patients, 21 (51.2%) were older than 15 years and 25 (60.9%) were male. All the patients had diarrhea, 24 (58.5%) had watery stools and 6 (14.6%) cholera-like diarrhea; 10 (24.4%) presented vomiting and 12 (29%) mild dehydration. Six malnourished children who suffered from diarrhea with moderate dehydration for more than a week, were hospitalized. V. cholerae non O1 and Shigella flexneri were isolated from one patient, during the first outbreak and V. cholerae non O1 and Salmonella IV 50:b:- were recovered simultaneously from another patient during the fourth outbreak. A 72 year old woman died during the second cholera outbreak. The symptoms were: watery diarrhea, vomiting, fever and mild dehydration. A strain of V. cholerae O5, that did not produce cholera toxin, heat-stable enterotoxin, Kanagawa-like hemolysin or verocitotoxin was detected. It was positive for El Tor hemolysin and D-mannose and L-fucose resistant cells-associated hemagglutinins. Among the 41 isolates studied, all were oxidase and indole positive, fermented glucose, saccharose and mannitol. They were all motile, produced lysine and ornithine decarboxylases but not arginine dihydrolase or hydrogen sulfide. They were sensitive to O129 vibriostatic compound. None of them belonged to O1 or O139 serogroup and they did not produce cholera troxin. Among the V. cholerae non O1 strains isolated, 9.5% were resistant to ampicillin and 4.9% to trimethoprim-sulfamethoxazole. Active surveillance had shown that V. cholerae non-O1 is not an important agent of diarrhea in Orán, Salta.

Prospective study of enteropathogens in two communities of Misiones, Argentina

Children under five years of age, from two communities of different socio-economic strata (97 from Zaiman and 55 from Las Dolores) were examined epidemiologically during 2 years, by means of quarterly visits of the working team, who carried out the collection of faecal samples. During the study, one or more enteropathogens were identified in 73.9% of samples in children from Zaiman and in 58.3% of the samples from Las Dolores, being associated to diarrhoea in 70.5% and to asymptomatic infections in 65.7%. The number of diarrheic episodes was higher in Zaiman (15.45%) than in Las Dolores (12.35%), being more frequent in the spring-summer seasons. In Zaiman, the bacterial enteropathogen proportion was relevantly higher (p < 0.005) in children with diarrhoea, whereas the presence of parasites was more frequent in asymptomatic children (p < 0.01). Rotavirus had an even distribution within diarrheic and asymptomatic children. In Las Dolores, no relevant differences were found in the detection of enteroparasites between diarrheic and asymptomatic children. Mixed infections were detected; enterotoxigenic Escherichia coli (ETEC)-rotavirus and ETEC-parasites being the most frequent ones. ETEC was involved in 85% of these infections. These data, together with the high enteropathogen carriage, suggest an elevated level of environmental contamination. The latter plays an important role in diarrheic diseases, and added to the most extreme poverty, it affects children's lives.

Gonadal (ovarian) dysgenesis in 46,XX individuals: frequency of the autosomal recessive form

Gonadal (ovarian) dysgenesis with normal chromosomes (46,XX) clearly is a heterogeneous condition. In some forms, the defect is restricted to the gonads, whereas other affected females show neurosensory hearing loss (Perrault syndrome). In another form, brothers may have germ cell aplasia [Granat et al., Fertil Steril 1983; 40:215-219]. Nongenetic causes exist as well. To elucidate the proportion of XX gonadal (ovarian) dysgenesis due to autosomal recessive genes, we analyzed published (N = 17) and unpublished (N = 8) families having at least two female offspring. Analysis was restricted to cases in whom ovarian failure was documented by the presence of streak ovaries (published cases) or elevated gonadotropins (unpublished cases). We reasoned that the closer to that segregation ratio expected for an autosomal recessive trait (0.25), the lower the frequency of nongenetic forms. Segregation analysis utilized standard correction for single ascertainment, with only females included in the preliminary analysis. The segregation ratio estimate was 0.16. Our results suggest that many 46,XX females with gonadal (ovarian) dysgenesis represent a disorder segregating as an autosomal recessive trait, placing sisters of these cases at a 25% risk for this disorder.

Fracture after cardiac transplantation: a prospective longitudinal study

Cardiac transplantation is associated with increased prevalence of vertebral fractures, but the natural history of and risk factors for fracture after this life-saving procedure are unclear. We evaluated 47 patients (34 men and 13 postmenopausal women) before transplantation with spinal radiographs, determination of bone density by dual energy x-ray absorptiometry, and measurement of biochemical indexes of mineral metabolism. During the first year after transplantation, incident fractures were documented radiographically. Associations among demographic characteristics, bone density, biochemistries, and fracture risk were evaluated with logistic regression analysis. Despite supplementation with elemental calcium (1000 mg/day) and vitamin D (400 IU/day), 17 patients (7 women and 10 men) sustained a total of 34 fractures. Most fractures involved the spine, and 85% of the patients who experienced fracture did so within 6 months of transplantation. Fifty-four percent of the women and 29% of the men experienced fracture. Femoral neck bone mineral density was significantly lower in women who experienced fracture than in those who did not (0.604 +/- 0.11 vs. 0.760 +/- 0.12 g/cm2; P < 0.04), but did not differ in men according to fracture outcome. The amount of bone loss at the femoral neck by 6 months after transplantation was significantly greater in men with fracture than in men without fracture (12.0 +/- 6.4% vs. 6.8 +/- 5.3%; P < 0.04), but did not differ in women according to fracture outcome. Pretransplant 1,25-dihydroxyvitamin D levels were significantly lower (25 +/- 9 vs. 39 +/- 17 pg/mL; P < 0.007) and intact PTH levels tended to be higher in men who did not experience fracture (37 +/- 15 vs. 69 +/- 46 pg/mL; P < 0.06). Individual pretransplant bone density measurements demonstrated substantial overlap between patients who did and did not experience fracture, and normal bone density did not necessarily protect against fracture after transplantation. We conclude that fractures are a common and early complication of cardiac transplantation. No pretransplant measurement has yet been identified that reliably predicts fracture after transplantation in the individual patient.

Water permeability properties of the human small intestine in vitro: effects of Escherichia coli heat-stable enterotoxin

The net absorptive water flux (Jw), the transepithelial potential difference (PD) and the short-circuit current (Isc) were simultaneously measured in the human small intestine in vitro with the following results: 1) An absorptive Jw was observed when the jejunum or the ileum were mounted between two identical standard solutions in the presence of an hydrostatic pressure gradient (delta P) of 13 cm of water (mucosal side positive). 2) The absorptive Jw was a linear function of the applied delta P or the imposed osmotic transepithelial gradient (delta Osm) in both intestinal segments. The hydrostatic (Phydr) and osmotic (Posm) permeabilities to water for jejunum and ileum were: 0.349 +/- 0.049 cm/s vs. 0.156 +/- 0.022 cm/s and 0.0012 +/- 0.0001 cm/s vs. 0.0019 +/- 0.0003, respectively. 3) A fraction of this absorptive Jw was independent of the presence of any hydrostatic, osmotic or chemical gradient and represented the transport associated to movement of water (Jwt). 4) PD and Isc values were similar in the jejunum and in the ileum but the transepithelial resistance (Rt) was significantly greater in ileum than in jejunum. 5) 2 micrograms/ml of E. coli heat-stable enterotoxin (STa) caused a significant inhibition of the absorptive Jw without modification of Phydr, Posm or Isc. 6) After STa treatment, the absorptive Jwt reverted to a secretory one in the jejunum. In the ileum, STa action caused a 48% decrease in the absorptive Jwt values.

Antibody responses against Escherichia coli heat-labile toxin and colonization factor antigens I and II in Argentinian children

Serum antibody responses against Escherichia coli heat-labile enterotoxin (LT) and colonization factor antigens (CFAs) I and II were studied in 84 children < 5 years old living in two communities. These villages differed in the quality of their drinking water. Children from both communities developed significantly increased antibody titers against LT and CFA/II but not against CFA/I during 3 months of follow-up. The magnitude of the anti-LT response was significantly higher in children from Zaiman than in those from Las Dolores. Antibody titers rose to maximum levels during the second year of age and reached relatively constant levels in children aged 2-5 years, probably due to repeated exposure to enterotoxigenic E. coli strains. Antibody levels of 30 children were followed for 2 years; increases in anti-LT and anti-CFA titers varied in the different age groups.

Systemic and subcutaneous microvascular oxygen tension in conscious Syrian golden hamsters

Arteriolar and venular oxygen tension distribution was studied in the subcutaneous connective tissue of the chamber window preparation in conscious Syrian golden hamsters as a function of the systemic PO2, PCO2, pH, arterial pressure and hematocrit, microvascular red blood cell (RBC) velocity, vessel diameter, and blood flow in the same microvessels. PO2 was measured with the phosphorescence decay technique using Pd-meso-tetra(4-carboxyphenyl)porphyrin (30 mg/kg body wt iv). Systemic arterial and venous PO2s were 71.6 +/- 13.1 and 28.4 +/- 5.1 mmHg, while oxygen tension was 45.1 +/- 13.3 mmHg in arterioles and 30.1 +/- 10.7 mmHg in venules. The relatively low arteriolar PO2 and the small arteriolar-venular PO2 gradient indicate that some blood oxygen exits directly to the tissue or is shunted before reaching the capillaries. RBC velocity was the strongest correlate of microvascular PO2 (arterial correlation coefficient = 0.503 and venous correlation coefficient = 0.560, P < 0.001). Microvascular PO2 was also correlated with blood flow, vessel diameter, blood pH, and PCO2 but not with systemic PO2. Arterial oxygen tension was only significantly related to PCO2, pH, and hematocrit. These findings suggest that oxygen delivery to the tissue improves with increasing blood flow velocity and that microvascular PO2 is a locally regulated parameter in the absence of major systemic perturbations.

Trisomy 21 and maternal age of menopause: does reproductive age rather than chronological age influence risk of nondisjunction?

The biological basis underlying the increased risk of nondisjunction in offspring of women of advanced maternal age is not understood. We sought to test the hypothesis that maternal reproductive age (distance in time from approaching menopause) rather than chronological age is pivotal in the etiology of nondisjunction. Our results found no difference in age of menopause between women > or = 30 years old at delivery of a child with trisomy 21 (i.e., age-related nondisjunction) compared to controls. Among women < 30 years of age at delivery of a child with trisomy 21, none underwent premature menopause. Therefore, our findings fail to support the theory that reproductive age plays a major role in the etiology of nondisjunction.

[Enterohemorrhagic Escherichia coli in hemolytic uremic syndrome in Chilean children. Evaluation of different technics in the diagnosis of the infection]

Enterohemorrhagic Escherichia coli (EHEC), have been associated with pathogenesis of hemolytic uremic syndrome (HUS) worldwide. Our aim was to determine the association of EHEC infection and HUS in Chilean children. During may 1991 and october 1993, 34 children with HUS and 33 age matched controls (children with diarrhea that did not develop HUS) were enrolled in a case/control study. For each child a stool and serum sample were obtained at admission. Stools were processed for common enteropathogens and for EHEC identification. EHEC were identified in stools by gene probes for different virulence factors (EHEC plasmid-associated fimbria, Shiga-like toxin I, Shiga-like toxin II and eae adherence factor) and by detection of free fecal toxin by a neutralization assay in Vero cells. Sera were processed for anti-cytotoxin antibodies also by an assay in Vero cells. Enteropathogens were isolated in 20.6% and 15.5% of HUS and control children respectively (p = NS). 91% of the HUS children and 73% of the control children were EHEC positive by one or more of the techniques used (p = 0.05). Of the three detection methods used for EHEC, only free fecal cytotoxin was significantly more common in HUS children than controls (45.5% vs 9% p = 0.007). Genotype patterns of HUS and controls strains were similar except for a trend towards a higher frequency of non-toxigenic strains in the control group. Serogroup O157 was more common in HUS children than in controls (9% vs 0% p = 0.036). In Chile as in other countries, EHEC infection is common and significantly associated with occurrence of HUS. Infection with EHEC strain O157 seems to be an important risk factor for HUS.

Direct detection of Vibrio cholerae in stool samples

A direct method to detect Vibrio cholerae in stool samples was developed by using a PCR procedure that did not require a DNA purification step. Dilution (1/100) of stool samples prevented inhibition of the reaction by contaminants, and two consecutive PCRs, the second one with a nested primer, achieved the desired sensitivity. Comparison of the results obtained from stool swab samples processed by the two-step PCR and by an enzyme-linked immunosorbent assay using GM1 as the capture molecule showed that the former is more sensitive and gave positive results even when V. cholerae was not culturable or dead.

Identification of toxigenic Vibrio cholerae from the Argentine outbreak by PCR for ctx A1 and ctx A2-B

A polymerase chain reaction (PCR) to detect a region of the A1 cholera toxin gene was applied to the identification of 43 Vibrio cholerae strains isolated from the recent outbreak in Argentina. A good correlation was observed between the GM1-enzyme-linked immunosorbent assay (GM1-ELISA) to detect the B subunit of the enterotoxin and PCR. However, a V. cholerae non-01 strain that was negative by the ELISA test, was positive by the PCR assay for the A1 region. A second PCR test to detect the A2-B coding region was developed to solve this case. We propose that routine detection of toxigenic V. cholerae by PCR should include analysis of A2-B coding region or the whole cholera toxin operon.

Studies of the Effect of Cyclosporine in Psoriasis In Vivo: Combined Effects on Activated T Lymphocytes and Epidermal Regenerative Maturation

Cyclosporine (CSA) decreases lymphokine synthesis and keratinocyte proliferation in vitro, but its in vivo mechanism of action in treating recalcitrant psoriasis is incompletely understood. Ten psoriasis patients were treated with CSA (2-7.5 mg/kg/d) with clinical improvement in nine of 10 patients. Skin biopsies before and after 1-3 months of CSA treatment were studied for evidence of immune and keratinocyte activation using immunoperoxidase and Northern blotting analysis. The number of activated, IL-2 receptor+ T cells in plaques after CSA treatment was reduced in all patients by a mean of 60%. Seven of 10 patients showed a decrease in keratinocyte HLA-DR expression; five of seven showed a decrease in gamma-IP-10 immunoreactivity, suggesting a decline in gamma interferon levels in plaques after CSA therapy. We studied the effect of CSA treatment in vivo on TGF-alpha, IL-6, and keratin K16 expression, three markers of keratinocyte growth activation. Expression of keratinocyte TGF-alpha and IL-6, which are elevated in active psoriatic epidermis, did not change in these patients after CSA treatment. The majority of patients (five of eight) continued to express the hyperproliferative keratin K16 after CSA treatment. Our results suggest that the predominant direct mechanism of action of Cyclosporine in vivo is a diminution of T-cell activation in plaques, with attendant decreased lymphokine production.

Colonization factors of enterotoxigenic Escherichia coli isolated from children with diarrhea in Argentina

A prospective study was performed to evaluate the presence of colonization factor antigens (CFAs) in enterotoxigenic Escherichia coli (ETEC) strains isolated from 1,211 children with diarrhea in Argentina. One hundred nine ETEC strains that were isolated from seven different laboratories in various regions of the country were tested for CFAs by using monoclonal antibodies against CFA/I and E. coli surface antigens CS1, CS2, and CS3 of CFA/II and CS4 and CS5 of CFA/IV; a polyclonal antiserum against CS6 was used. The CFAs searched for were found in 52% of the ETEC strains: 23% of the strains carried CFA/I, 17% carried CFA/IV, and 12% carried CFA/II. All of the CFA/I strains produced heat-stable enterotoxin, and several of them were of the prevalent serotypes O153:H45 and O78:H12. Among the 19 strains expressing CFA/IV, 16 expressed CS5 and CS6 and produced the heat-stable enterotoxin and most were of serotype O128:H21; the remaining 3 strains produced CS6 only. No ETEC strains expressing CS4 were found. Most (11 of 13) of the CFA/II-carrying ETEC strains expressed CS1 and CS3, and 10 of them were of the O6:K15:H16 serotype and produced both heat-labile and heat-stable toxins. As many as 24 of the 109 CFA-negative ETEC strains gave mannose-resistant hemagglutination with erythrocytes from different species; 4 strains had high surface hydrophobicity, suggesting the presence of additional, as yet undefined, colonization factors in up to 25% of the ETEC isolates.

An evaluation of the pooling culture method for the detection of Escherichia coli enterotoxins

The efficiency of the pooling method for the detection of enterotoxigenic Escherichia coli (ETEC) strains associated with children acute diarrhea, was evaluated. This study involved the analysis of 6989 E. coli strains corresponding to 1485 cases, coming from 7 hospitals at different geographic locations. Three to five strains from each case were inoculated in pool in Casamino-acids-yeast extract-salts medium plus lincomycin (30 micrograms/ml) and incubated at 37 degrees C during 18 hours with shaking. Polymyxin sulphate B (2200 U/ml) was added to the cultures, and incubation with shaking continued for additional 30 minutes. The culture was then centrifuged and the supernatant tested by a) the enzyme-linked immunosorbent assay to detect heat-labile enterotoxin (LT) and b) the suckling mouse assay for the detection of heat-stable enterotoxin (ST). Strains from a pool were individually studied in all positive cases as shown by the pooling methodology. Also, in 1 out of every 15 negative cases by the pool method, their component strains were individually analyzed, to confirm that there were no false negatives. Fifty seven LT-ETEC, 61 ST-ETEC and 15 LT-ST cases were detected. From the 89 negatives selected by the pool method, 2 cases were positive when the component strains were individually tested (p1 = 2.25%, 95% confidence interval from 0.27 to 7.88%). In both cases one of the non ETEC strains inhibited the ETEC strain. In other 5 negative cases (p2 = 5.62%, 95% confidence interval from 1.85% to 12.63%), ETEC strains were detected when analyzed individually, and gave a positive result when the pooling method was repeated.(ABSTRACT TRUNCATED AT 250 WORDS)

[Production of thermolabile exotoxin by strains of Escherichia coli isolated in Argentina]

The production of heat-labile enterotoxin (LT) by E. coli strains was studied. Four strains isolated from acute infant diarrhea cases in Argentina and one reference strain, all of them producers of different levels of LT, were employed. GM1-ELISA was used as titration method. The production was assayed in two culture media; Evans (Ev) and Trypticase Soy Broth (CTS) with or without glucose and with different concentrations of lincomycin (0; 30; 45 y 90/micrograms/ml). The effects of pH and inoculum concentration were also examined. Higher levels of LT were found to be produced in Ev (mean production value X = 233.1 ng/ml) than in CTS (X = 133.8 ng/ml), although the difference was statistically not significant (P = 0.22). Lincomycin addition stimulated toxin synthesis and release in both media, and these effects were found to increase with the concentration of the antibiotic (P less than 0.01). Glucose increased the LT levels of low-producing strains and also the growth rate, cellular yield and LT levels of 40T and CC2e strains. Levels of LT released were found to be independent of inoculum concentration. In CTS without pH control, the LT production was one half the levels attained with regulated pH. This was not an effect on the release of the toxin as the determination included both the extracellular LT and the intracellular toxin accumulated in the periplasmic space, which is released by polymyxin B treatment. A pH-dependent inactivation of the synthetized and release toxin was demonstrated.

[Numerical taxonomy of gram-positive anaerobic bacilli]

Numerical Taxonomy's techniques were employed on twenty one anaerobic Gram positive bacilli strains taking account of eighty morphologic and biochemical features. Two methods of coding (weighted and non weighted) and four clustering methods (unweighted pair-group method using arithmetic averages; weighted pair-group method using arithmetic averages; single linkage and complete linkage) were used. Eight dendrograms were obtained and they showed that C. haemolyticum (strains 1, 2, 4, 7); C. subterminale (strains 8, 19); C. botulinum (strain 14) and C. sporogenes (strain 15) belong to a different group than the other strains. Another group would be formed with C. perfringens (strains 3, 5, 6, 12, 16, 21) and C. paraperfringens (strains 9, 10, 11). Of the remaining strains the two classified as Propionibacterium acnes (strains 17, 18) have a very high degree of agreement. C. histolyticum (strain 20) adjoins at a very low level, while C. butyricum (strain 13) shows a unfixed behaviour. The dendrograms display a disposition according with Classical Taxonomy.