Enteroaggregative Escherichia coli as etiological agent of endemic diarrhea in Spain: A prospective multicenter prevalence study with molecular characterization of isolates

Background

Enteroaggregative Escherichia coli (EAEC) is increasingly associated with domestically acquired diarrheal episodes in high-income countries, particularly among children. However, its specific role in endemic diarrhea in this setting remains under-recognized and information on molecular characteristics of such EAEC strains is limited. We aimed to investigate the occurrence of EAEC in patients with non-travel related diarrhea in Spain and molecularly characterize EAEC strains associated with illness acquired in this high-income setting.

Methods

In a prospective multicenter study, stool samples from diarrheal patients with no history of recent travel abroad (n = 1,769) were collected and processed for detection of EAEC and other diarrheagenic E. coli (DEC) pathotypes by PCR. An additional case–control study was conducted among children ≤5 years old. Whole-genome sequences (WGS) of the resulting EAEC isolates were obtained.

Results

Detection of DEC in the study population. DEC was detected in 23.2% of patients aged from 0 to 102 years, with EAEC being one of the most prevalent pathotypes (7.8%) and found in significantly more patients ≤5 years old (9.8% vs. 3.4%, p < 0.001). Although not statistically significant, EAEC was more frequent in cases than in controls. WGS-derived characterization of EAEC isolates. Sequence type (ST) 34, ST200, ST40, and ST10 were the predominant STs. O126:H27, O111:H21, and O92:H33 were the predominant serogenotypes. Evidence of a known variant of aggregative adherence fimbriae (AAF) was found in 89.2% of isolates, with AAF/V being the most frequent. Ten percent of isolates were additionally classified as presumptive extraintestinal pathogenic E. coli (ExPEC), uropathogenic E. coli (UPEC), or both, and belonged to clonal lineages that could be specifically associated with extraintestinal infections.

Conclusion

EAEC was the only bacterial enteric pathogen detected in a significant proportion of cases of endemic diarrhea in Spain, especially in children ≤5 years old. In particular, O126:H27-ST200, O111:H21-ST40, and O92:H33-ST34 were the most important subtypes, with all of them infecting both patients and asymptomatic individuals. Apart from this role as an enteric pathogen, a subset of these domestically acquired EAEC strains revealed an additional urinary/systemic pathogenic potential.

Prevalence and temporal dynamics of Cryptosporidium spp., Giardia duodenalis, and Blastocystis sp. among toddlers attending day-care centres in Spain. A prospective molecular-based longitudinal study

Giardia duodenalis, Cryptosporidium spp., and Blastocystis sp. are common intestinal eukaryotic parasites affecting children in developed and resource-limited countries. Lack of information on the epidemiology and long-term stability in asymptomatic children complicates interpretation of transmission and pathogenesis. To assess the occurrence, genetic diversity, and temporal dynamics of intestinal eukaryotic parasites in young children, 679 stool samples from 125 toddlers attending six public day-care centres in Central Spain were collected bimonthly within a 1-year period. Detection and identification of species/genotypes were based on PCR and Sanger sequencing methods. Four eukaryotic species were identified: G. duodenalis (2.5‒31.6%), Cryptosporidium spp. (0.0‒2.4%), Blastocystis sp. (2.5‒6.4%), and Entamoeba dispar (0.0‒0.9%). Entamoeba histolytica and Enterocytozoon bieneusi were undetected. Sequence analyses identified assemblage A (63.6%) and B (36.4%) within G. duodenalis (n = 11), C. hominis (40%), C. parvum (40%), and C. wrairi (20%) within Cryptosporidium spp. (n = 5), and ST1 (3.8%), ST2 (46.2%), ST3 (15.4%), and ST4 (34.6%) within Blastocystis sp. (n = 26). Giardia duodenalis sub-assemblage AII/AIII was detected in a toddler for 10 consecutive months. Stable carriage of Blastocystis ST2 allele 9, ST3 allele 34, and ST4 allele 42 was demonstrated in five toddlers for up to 1 year.   Conclusions: Giardia duodenalis and Blastocystis sp. were common in toddlers attending day-care centres in Central Spain. Long-term infection/colonization periods by the same genetic variant were observed for G. duodenalis (up to 10 months) and Blastocystis sp. (up to 12 months). What is Known: • Asymptomatic carriage of G. duodenalis and Blastocystis sp. is frequent in toddlers. • The epidemiology and long-term stability of these eukaryotes in asymptomatic young children is poorly understood. What is New: • Long-term colonization/infection periods by the same genetic variant were described for Blastocystis sp. (up to 12 months) and G. duodenalis (up to 10 months).

Evaluation of the SHIGA TOXIN QUIK CHEK after overnight enrichment as screening tool for Shiga toxin-producing Escherichia coli detection in human fecal samples

We evaluated the SHIGA TOXIN QUIK CHEK (STQC) on its suitability for Shiga toxin-producing Escherichia coli (STEC) testing on human fecal samples after overnight enrichment. Our in-house PCR-based protocol for STEC detection was used as the standard for comparison. STQC detected all described Shiga toxin subtypes with the only exception of Stx2f. In comparison to PCR, STQC performed with an overall sensitivity of 55.4%, specificity of 100.0%, positive predictive value of 100.0%, negative predictive value of 73.0%, infinite positive likelihood ratio, and negative likelihood ratio of 0.45. We conclude that STQC may not be considered a suitable screening tool for STEC detection in human fecal samples, although it could be useful for laboratories where PCR is not a routine tool for STEC screening yet, subject to the confirmation of negative samples by a reference laboratory with full diagnostic capabilities.

Mucus-Activatable Shiga Toxin Genotype stx2d in Escherichia coli O157:H7

We identified the mucus-activatable Shiga toxin genotype stx2d in the most common hemolytic uremic syndrome–associated Escherichia coli serotype, O157:H7. stx2d was detected in a strain isolated from a 2-year-old boy with bloody diarrhea in Spain, and whole-genome sequencing was used to confirm and fully characterize the strain.

Isolation of Campylobacter spp. from Three Species of Antarctic Penguins in Different Geographic Locations

The presence of Campylobacter species was studied in three Antarctic penguin species, Adélie (Pygoscelis adeliae), chinstrap (Pygoscelis antarctica) and gentoo (Pygoscelis papua). A total of 390 penguins were captured in 12 different rookeries along the Antarctic Peninsula with differences in the amount of human visitation: six colonies were highly visited [Stranger Point, King George Island (P. papua and P. adeliae); Hannah Point, Livingston Island (P. papua and P. antarctica); Deception Island (P. antarctica); and Paradise Bay, Antarctic Peninsula (P. papua)], and six colonies were rarely visited [Devil's Point, Byers Peninsula, Livingston Island (P. papua); Cierva Cove, Antarctic Peninsula (P. papua); Rongé Island (P. papua and P. antarctica); Yalour Island (P. adeliae); and Avian Island (P. adeliae)]. A total of 23 strains were isolated from penguins from nine different rookeries. Campylobacter lari subsp. lari was isolated from eight samples (seven from P. papua and one from P. adeliae); C. lari subsp. concheus from 13 (ten from P. adeliae and three from P. antarctica) and C. volucris from two samples (both from P. papua). We did not find any significant differences in the prevalence of Campylobacter spp. between the populations in highly and rarely visited areas. This is the first report of C. lari subsp. concheus and C. volucris isolation from penguins in the Antarctic region.

Development of three multiplex PCR assays targeting the 21 most clinically relevant serogroups associated with Shiga toxin-producing E. coli infection in humans

Escherichia coli serogroups O5, O15, O26, O45, O55, O76, O91, O103, O104, O111, O113, O118, O121, O123, O128, O145, O146, O157, O165, O172, and O177 are the O-antigen forms of the most clinically relevant Shiga toxin-producing E. coli (STEC) serotypes. In this study, three multiplex PCR assays able to specifically detect these 21 serogroups were developed and validated. For this purpose, the O-antigen gene clusters of E. coli O5 and O76 were fully sequenced, their associated genes were identified on the basis of homology, and serogroup-specific primers were designed. After preliminary evaluation, these two primer pairs were proven to be highly specific and suitable for the development of PCR assays for O5 and O76 serogroup identification. Specific primers were also designed for serogroups O15, O45, O55, O91, O104, O113, O118, O123, O128, O146, O157, O165, O172, and O177 based on previously published sequences, and previously published specific primers for serogroups O26, O103, O111, O121, and O145 were also included. These 21 primer pairs were shown to be specific for their target serogroup when tested against E. coli type strains representing 169 known O-antigen forms of E. coli and Shigella and therefore suitable for being used in PCR assays for serogroup identification. In order to validate the three multiplex PCR assays, 22 E. coli strains belonging to the 21 covered serogroups and 18 E. coli strains belonging to other serogroups were screened in a double-blind test and their sensitivity was determined as 1 ng chromosomal DNA. The PCR assays developed in this study could be a faster, simpler, and less expensive strategy for serotyping of the most clinically relevant STEC strains in both clinical microbiology and public health laboratories, and so their development could benefit for clinical diagnosis, epidemiological investigations, surveillance, and control of STEC infections.

The new allelic variant of the subtilase cytotoxin (subAB2) is common among Shiga toxin-producing Escherichia coli strains from large game animals and their meat and meat products

Subtilase cytotoxin (SubAB) is an AB5 toxin produced by Shiga toxin (Stx)-producing Escherichia coli (STEC) strains usually lacking the eae gene product intimin. Two allelic variants of SubAB encoding genes have been described: subAB1, located on a plasmid, and subAB2, located on a pathogenicity island (PAI) together with tia gene. While subAB1 has been reported to be more frequent among bovine strains, subAB2 has been mainly associated with strains from small ruminants. We investigated the presence of the two variants of subAB among 59 eae-negative STEC from large game animals (deer and wild boar) and their meat and meat products in order to assess the role of other species in the epidemiology of subAB-positive, eae-negative STEC. For this approach, the strains were PCR-screened for the presence of subAB, including the specific detection of both allelic variants, for the presence of saa, tia and sab, and for stx subtyping. Overall, subAB genes were detected in 71.2% of the strains: 84.1% of the strains from deer and 33.3% of the strains from wild boar. Most of them (97.6%) possessed subAB2 and most of these subAB2-positive strains (92.7%) were also positive for tia and negative for saa, suggesting the presence of the subAB2-harbouring PAI. Subtype stx2b was present in most of the strains (67.8%) and a statistically significant association could be established between subAB2 and stx2b. Our results suggest that large game animals, mainly deer, may represent an important animal reservoir of subAB2-positive, eae-negative STEC, and also highlight the risk of human infection posed by the consumption of large game meat and meat products.

Cytotoxicity and genotoxicity of sewage treatment plant effluents in rainbow trout cells (RTG-2)

The cytotoxicity and genotoxicity of 11 organic fractions from sewage treatment plant (STP) effluents were tested using the RTG-2 rainbow trout permanent cell line. An automated in vitro micronucleus assay developed for RTG-2 cells was used to test the genotoxicity, whereas neutral red uptake, kenacid blue protein assay and ATP content were used to evaluate cytotoxicity. The induction of micronuclei (MN) and alterations in the cell cycle were analysed in these cells by flow cytometry after exposure to the organic fractions for 72 h. More than half of the organic extracts tested demonstrated a significant increase in the MN frequency, thus indicating that most of them can be considered to be genotoxic. The extracts were analysed chemically by GC/MS. Although the most frequently detected compounds in the effluents were bisphenol A (BPA), octylphenol (OP), di-2-ethylhexyl phthalate (DEHP) and dibutyl phthalate (DBP), as well as other possible mutagens, the concentrations cannot explain the genotoxicity of the individual chemicals, thereby suggesting a mixture effect. The results obtained support the need to apply effect-based tests to monitor complex mixtures as the most accurate means of assessing the genotoxicity of environmental samples.

Cytotoxic and genotoxic effect in RTG-2 cell line exposed to selected biocides used in the disinfection of cooling towers

The cytotoxic and genotoxic effects induced by trichloroisocyanuric acid, Oxone, and sodium bromide, active principles included in formulations for cleaning and disinfection of cooling towers, were studied on RTG-2 cell line. Neutral red assay was used to determine the cellular viability. Toxicity ranking based on IC(50) values found that trichloroisocyanuric acid was the most cytotoxic biocide tested followed by Oxone, whereas sodium bromide resulted in a very low cytotoxicity. DNA damage has been evaluated on RTG-2 cultures by means of an in vitro assay based on the ability of PicoGreen fluorochrome to interact preferentially with dsDNA, and the results indicated that trichloroisocyanuric acid induced DNA strand breaks at concentrations above 1.2 mg/l, equivalent to 1/50-EC(50(48)), whereas exposures to Oxone and sodium bromide did not induce DNA damage at the maximal concentrations tested (1/10-EC(50(48))). These results confirm the suitability of this method for the screening of genotoxic effects of this type of aquatic pollutants, and we suggest their use in environmental risk assessment procedures.

Correlation between the presence of symptoms and the Giardia duodenalis genotype

Clinical manifestations of Giardia duodenalis infection vary from asymptomatic infection to chronic diarrhoea. We study the correlation between the presence of symptoms and the G. duodenalis genotype in 108 patients with giardiasis. Patient age ranged from 2 to 72 years old. We found a correlation between assemblage AII and symptomatic infections, and between assemblage B and asymptomatic infections in the overall patient group and in patients less than five years of age. Nevertheless, if only patients of more than five years of age were considered, no statistically significant relationship between assemblage and symptomatic or asymptomatic Giardia infections was found. In these patients, host factors may affect the presence of clinical manifestations more than Giardia assemblage.

Genetic characterization of Cryptosporidium species from humans in Spain

Several species of Cryptosporidium have been associated with infection. Cryptosporidium parvum and Cryptosporidium hominis are the main agents of cryptosporidiosis in humans. Stool samples from 108 Cryptosporidium-infected patients were submitted to PCR-RFLP analysis for a 553-bp fragment of Cryptosporidium oocyst wall protein (COWP) gene and an 826-864 bp fragment of the small-subunit ribosomal RNA (SSU-rRNA) gene. Ninety-two patients were immunocompetent children and 16 were HIV-infected adults. C. hominis was detected in 69 patients (59 immunocompetent and 10 HIV-infected); C. parvum, in 34 patients (28 immunocompetent and 6 HIV-infected); and C. meleagridis and C. felis in one patient each (both immunocompetent children). Three samples yielded negative results. C. parvum was significantly more frequent in children from rural areas than in those of urban residence (p=0.010). As far as we know, this is the first surveillance study about the molecular characterization of Cryptosporidium in humans performed in Spain. The finding of zoonotic species infecting humans calls for further research on this subject.

Genotoxic effects of selected biocides on RTG-2 fish cells by means of a modified Fast Micromethod Assay

A sensitive in vitro assay for detecting DNA damage in RTG-2 cells culture is described. This assay employs a dye, PicoGreen double stranded DNA (dsDNA) quantitation reagent, which becomes intensely fluorescent upon binding nucleic acids. The assay includes a simple and rapid 50-min sample lysis in the presence of EDTA, SDS, and high urea concentration at pH 10, followed by time-dependent DNA denaturation at pH 11.6 after NaOH addition. The time course and the extent of DNA denaturation are followed in a microplate fluorescence reader at room temperature for less than 1h. Comparative studies between suspension and fixed RTG-2 cells indicated that it is possible to apply this methodology in both cases with good results. Neutral red assay was used for to determine the cellular viability when RTG-2 cultures were exposed to tetrakis(hydroxymethyl) phosphonium chloride (THPC) and benzalkonium chloride (BC), as biocides used in the disinfection of cooling towers. The results obtained by neutral red assay indicate IC(50(48)) values of 0.017 (0.011-0.028) and 2.71 (1.91-3.86) mg/L for tetrakis(hydroxymethyl) phosphonium chloride and benzalkonium chloride, respectively. DNA damage has been evaluated for both disinfectants in RTG-2 culture, by exposure to 1/10-, 1/25-, 1/50-, and 1/100-IC(50(48)) value, and the results obtained indicate a strain scission factor (SSF) of 0.126+/-0.014, 0.181+/-0.014, 0.217+/-0.013, and 0.245+/-0.013 in cell suspensions, and 0.077+/-0.019, 0.107+/-0.014, 0.151+/-0.014, and 0.202+/-0.015 in attached cells for tetrakis(hydroxymethyl) phosphonium chloride; while the SSF values for benzalkonium chloride are 0.023+/-0.009, 0.033+/-0.017, 0.068+/-0.012, and 0.088+/-0.015 in cell suspensions, and 0.033+/-0.010, 0.044+/-0.011, 0.080+/-0.009, and 0.093+/-0.010 in attached cells. Thus, the assay proposed in this study has made it possible to show DNA damage in RTG-2 cells when exposed to 0.2(1/100 IC(50(48))) and 300(1/10 IC(50(48))) Hg/L of tetrakis(hydroxymethyl) phosphonium chloride and benzalkonium chloride, respectively. The results obtained indicate that the Fast Micromethod Assay, applied on RTG-2 cell line cultures, is a fast and sensitive method for the early DNA damage detection in the aquatic environment.

Post-antifungal effect and effects of sub-MIC concentrations on previously treated Candida spp.: influence of exposure time and concentration

This study evaluates the influence of exposure time and concentration on the post-antifungal effect (PAFE) and the effect of sub-MIC concentrations (1/4 x MIC) on Candida albicans and C. glabrata in the PAFE stage (PAFSE). This stage was induced by pretreatment for 1.5, 3 or 12 h with 1 x, 4 x or 8 x MIC of 4 antifungal agents fundamental to modern candidiasis therapy. The length of the 2 effects studied was dependent on the concentration of the antifungal agent applied during pretreatment, as well as on the exposure time. An increase in the dose and/or longer pretreatment prolonged the duration of the PAFE and PAFSE in both species and with all the antifungal agents. Significant PAFEs were always observed for amphotericin B and 5-fluorocytosine (0.8-13 h and 0.6-10.8 h, respectively). These values were increased (by 2.3-8.7 h and 1.5-7.8 h, respectively) by posterior exposure to 1/4 x MIC of the respective antifungal agent. Neither ketoconazole nor fluconazole were able to induce significant PAFEs, even with exposures of up to 12 h duration and a dose of 8 x MIC. However, treatment with 1/4 x MIC of each of the 2 azoles led to significant PAFSEs in both yeast species, of up to 6.5 h duration with ketoconazole and 1.7 h with fluconazole, if the concentrations and/or exposure times were sufficiently high.

Postantifungal effect and effects of sub-MIC concentrations on previously treated Candida sp. influence of growth phase

OBJECTIVES

This study evaluates the influence of growth phase on the postantifungal effect (PAFE) and on the effect of sub-MIC concentrations (1/4x MIC) on Candida sp. in PAFE stage (PAFSE).

METHODS

This stage was induced by pre-treatments of 1.5 h of C. albicans or C. glabrata in their exponential or stationary phase, with 1x, 4x or 8x MIC of four antifungal agents that are fundamental for modern candidiasis therapy.

RESULTS

Ketoconazole and fluconazole induced longer PAFSEs on microorganisms in logarithmic growth phase. However, this influence did not exist in the case of PAFSEs induced by AmB and 5-Fc or with the postantifungal effect induced by the four antifungal agents. In any way, significant PAFEs were always observed for Amphotericin B and 5-fluorocytosine (0.8-4.8 and 0.5-3 h, respectively, depending on the treatment dose). These values were increased (2.3-3.6 and 1.4-3.2 h respectively, depending on the pre-treatment dose) by posterior exposition to 1/4x MIC of the respective antifungal agent. In the case of ketoconazole and fluconazole, both antimycotics were not able to induce significant PAFEs, but posterior treatments to 1/4x MIC of each of the two azoles led in both yeast species to significant PAFSE of up to 2.6 h duration with ketoconazole, and 0.8 h with fluconazole, depending on the pre-treatment concentration.

CONCLUSION

The growth phase of microorganisms should be considered in the planning of dosage protocols with azoles, because if the concentration applied is not high enough, the sub-MIC effects could be no significant for fungi in stationary phase of large wounds. Amphotericin B and 5-fluorocytosine induced significant postantifungal effect onCandida sp. This effect was increased by posterior exposition to sub-MIC concentration of the antifungal agents. Ketoconazole and fuconazole were not able to induce significant PAFEs at the concentrations tested, but posterior treatments to sub-MIC concentrations led to significant PAFSE. The growth phase of the culture at the time of its pre-treatment did not influence the length of the PAFE induced in it. However, the effect of the sub-MIC concentrations of Kz or Flu in yeast in PAFE phase was greater on yeast in exponential phase than for cultures in stationary phase.

Evaluation of an immunochromatographic dip-strip test for the detection of Cryptosporidium oocysts in stool specimens

The study presented here examined the efficacy of a commercially available qualitative immunochromatographic assay for detecting Cryptosporidium oocysts in stool samples. A total of 75 samples were tested, including 50 positive for Cryptosporidium spp. by acid-fast stain, 20 positive for other parasites ( Blastocystis hominis, Endolimax nana, Entamoeba coli, Giardia lamblia, Ascaris lumbricoides, Strongyloides stercoralis and Trichuris trichiura), and five negative samples. The observed sensitivity was 98%, while specificity was 100%; the detection threshold was near 1000 oocysts/ml. Correctly diagnosed positive samples included Cryptosporidium parvum genotypes 1 and 2, whereas the single false-negative sample corresponded to a Cryptosporidium meleagridis infection.

[Antimicrobial resistance of clinical strains of Salmonella enterica isolated in Zaragoza]

In order to identify any changes in the incidence of Salmonella enterica serotypes and their resistance to a variety of antimicrobial agents, we conducted a retrospective study of all the strains isolated from stool samples at Hospital Clínico Universitario Lozano Blesa in Zaragoza from 1997 to 2000. We observed an increase in the number of isolates of Salmonella and Campylobacter and a decrease in other enteropathogens. Enteritidis was the most frequently isolated serotype (55.2%), showing an increasing tendency (from 44.1% in 1997 to 60.6% in 2000). Hadar, glostrup and virchow showed the highest rate of resistance to nalidixic acid. Enteritidis also showed an important increase in resistance to nalidixic acid (from 17.6% in 1997 to 41.4% in 2000). Typhimurium showed the highest resistance levels to ampicillin, chloramphenicol and cotrimoxazole. No resistance to fluoroquinolones or to cefotaxime was detected, with the exception of 0.5% of the S. enteritidis strains, which showed resistance to fluoroquinolones.

Detection of cytogenetic alterations and blood cell changes in natural populations of carp

A field study was conducted to investigate the appearance of alterations in the peripheral blood cells of wild populations of fish. Two aspects were evaluated: the appearance of cytogenetic effects, measured as increases on micronuclei frequencies, and the appearance of haematological effects by checking changes in the relative proportion of the different blood cell types. For this purpose common carp (Cyprinus carpio) were caught from four areas along a Spanish river. Three areas were located under the influence of chemical industries and/or a nuclear power plant. The fourth was a clean reference area. Flow cytometry was used to quantify the appearance of micronuclei on the same day of sampling and also after two and twelve months. The alterations in the relative proportion of cell types were counted in blood smears stained with Giemsa. Increases in micronuclei frequencies were observed in fish living in supposedly polluted areas. Alterations of the relative proportions of blood cells were manifested as an increase in white blood cells and as a decrease in red blood cells vs. control area. Since accidental spills have not been reported over this period of time, the alterations observed could suggest that fish are suffering chronic effects due to low level contamination associated with the sampled areas.

Influence of pH and concentration on the postantifungal effect and on the effects of sub-MIC concentrations of 4 antifungal agents on previously treated Candida spp

This study investigates the impact of different pH values (5.5 and 7.4) on the postantifungal effect (PAFE) and the effect of sub-MIC concentrations (1/4 x MIC) on C. albicans and C. glabrata in the PAFE stage (PAFSE). The PAFE stage was induced by a 1.5 h pretreatment with different doses (1, 4 and 8 x MIC) of 4 antifungal agents. An increase in the pH and/or an increase in the dose of the antimycotic prolonged the duration of the PAFE induced by amphotericin B or 5-fluorocytosine and the PAFSE induced by all 4 antifungal agents in both species. 5-Fluorocytosine and amphotericin B (except for treatment with 1 x MIC at pH 5.5) induced significant PAFEs (0.5-3.0 h and 1.4-4.8 h, respectively), which were increased (to 0.9-3.2 h and 0.8-3.4 h, respectively) by posterior (PLEASE EXPLAIN WHAT YOU MEAN BY THE WORD "POSTERIOR" HERE) exposure to 1/4 X MIC of the respective antifungal agent. Although ketoconazole and fluconazole were not able to induce significant PAFEs, posterior exposure to 1/4 x MIC of each of these 2 azoles led to significant PAFSEs of up to 2.6 h in both yeast species when the concentrations and pH were high enough.

The eaeA gene is not found in Hafnia alvei from patients with diarrhea in Aragón, Spain

A total of 102 Hafnia alvei clinical strains isolated from different patients with diarrhea has been tested, using polymerase chain reaction and dot-blot hybridization, for the enteropathogenic Escherichia coli attaching and effacing A (eaeA) gene to establish their role as a causative agent of diarrhea in our environment. None of them was positive for the eaeA gene. We cannot consider the eaeA gene as the virulence-associated factor implicated in the H. alvei strains isolated from diarrheal feces in our region.

Influence of temperature and concentration on the postantifungal effect and the effects of sub-MIC concentrations of four antifungal agents on previously treated Candida species

BACKGROUND

The objective of this study was to investigate the impact of different temperatures (22, 35 and 37 degrees C) on the postantifungal effect (PAFE) and the effect of sub-MIC concentrations (1/4 x MIC) on Candida albicans and Candida glabrata in PAFE stage (PAFSE).

METHODS

This stage was induced by a 1.5-hour pretreatment with different doses (1 x, 4 x and 8 x MIC) of four antifungal agents that are fundamental to modern candidiasis therapy.

RESULTS

The temperature, as well as the dose of the antifungal agent that was applied during the pretreatment, determined the duration of the two studied effects. An increase in the temperature and/or the dose prolonged the duration of the PAFE and PAFSE in both species, independent of the applied antifungal agent. Amphotericin B and 5-fluorocytosine always induced significant PAFEs (0.5-4.8 h and 0.5-3.0 h, respectively), which were increased (0.7-3.4 h and 0.5-3. 2 h, respectively) by posterior exposure to 1/4 x MIC of the respective antifungal agent. In the case of ketoconazole and fluconazole, temperature and concentration were especially important. Although neither antimycotics was able to induce a significant PAFE, posterior exposure to 1/4 x MIC of each of the two azoles led in both yeast species to a significant PAFSE of up to 0.8 h (if the concentrations and/or the temperatures were high enough).

CONCLUSION

Factors such as temperature and concentration could be important when choosing an antifungal agent.

The use of alternative systems for the ecotoxicological screening of complex mixtures on fish populations

This paper presents the results of the use of alternative systems in a screening study of four complex mixtures. The following tests were performed: in vitro induction of micronuclei in a rainbow trout-derived cell line by flow cytometry, and hatching percentage, time of hatching and teratogenic alterations on the embryolarval development on medaka fish eggs. The results obtained with the proposed tests in this study allows an increase in the information level in a short period of time (2 weeks), using very low sample volumes (< 100 ml). Inclusion of chronic and specific effects (genotoxicity and teratogenicity) allows the selection of the most sensitive endpoint to increase security factors in the ecotoxicological assessment of complex mixtures, so that detailed studies can be focused only on those samples which require further research.

Flow cytometric detection of micronuclei and cell cycle alterations in fish-derived cells after exposure to three model genotoxic agents: mitomycin C, vincristine sulfate and benzo(a)pyrene

The measurement of cytogenetic alterations in vitro is considered an initial step in the risk assessment procedures for genotoxic agents. The concern about genotoxic pollutants in natural fish population makes the use of fish-derived cells an useful tool for these purposes. The technological improvements in well-established cytogenetic endpoints, such as micronuclei (MN) estimations by means of flow cytometry, have been proposed in the later years using mammalian cells. In this work, we test the capability of flow cytometry to evaluate MN induction and cell cycle alterations in an established fish cell line (RTG-2) using three agent-inductor models at different concentrations and exposure periods. For mitomycin C, an inverse relationship between length of exposure period and concentrations was observed. A dose-response relationship was observed after exposing RTG-2 cells to vincristine sulfate and benzo(a)pyrene. As this study shows, RTG-2 cells respond to clastogenic and aneugenic effects of the tested chemicals through the induction of MN at similar doses to mammalian cells and without the addition of exogenous metabolic activity. The possibility to check cell cycle alterations, in the same sample, gives the opportunity to evaluate early signals of cytotoxicity. The use of flow cytometry improves the assay by means of its speed and objectivity, which makes the assay very useful for genotoxicity assessment of aquatic chemicals.

Activity of voriconazole: post-antifungal effect, effects of low concentrations and of pretreatment on the susceptibility of Candida albicans to leucocytes

This study examined: (i) the post-antifungal effect (PAFE) of Voriconazole (UK 109,496) on Candida albicans, at 2 concentrations (MIC and 4 x MIC) in the presence or absence of 10% human serum; (ii) the activity of low concentrations of the drug (1/4 x MIC) on yeasts that had previously been exposed to Voriconazole (PAFSE) with or without 10% human serum; and (iii) the effect of Voriconazole pretreatment on the fungicidal activity of leucocytes and serum against C. albicans (PALE). Two concentrations (0.25 and 1 mg/l) of Voriconazole induced no PAFE against C. albicans between -4.3 and -1.4 h, but when the assays were performed in the presence of serum, positive and concentration-dependent PAFEs were obtained (0.2-4.1 h). Pretreated yeasts were more susceptible than untreated yeasts to low concentrations (0.0625 mg/l) of Voriconazole, so the drug showed positive PAFSE that was dependent on the concentration used in pretreatment without serum (0.3-1.9 h) or with 10% human serum (0.5-2.5 h). Pretreatment of the growing C. albicans cells with Voriconazole (0.25 mg/l) increased their vulnerability to killing by leucocytes during the last 2 h (p < 0.05), leading to PALE of 2 h. The results suggest that these effects might be used to evaluate the in vivo activity of an antifungal agent. The sum of the durations of these effects (PAFE, PAFSES and PALE) cause a considerable delay in yeast growth in treated cultures compared with control cultures.

Postantifungal effect and effects of low concentrations of amphotericin B and fluconazole on previously treated Candida albicans

The objective of the study was to assess (a) the postantifungal effect (PAFE) of amphotericin B (AmB) and fluconazole (Flu) on two Candida albicans strains, and (b) the effect of low concentrations of AmB or Flu on yeasts previously exposed to AmB or Flu, respectively, in the presence or absence of 10% human serum. In the absence of serum, AmB exerted a positive effect (at 0.5-5.0 h) depending on the concentration and the strain used. Flu, however, produced negative effects (at -1.2 to -0.1 h). When the experiment was conducted in the presence of serum, the duration of all PAFEs increased significantly, especially those induced by Flu that became positive. Pretreated yeasts were more susceptible than untreated controls to the antifungal activity of low concentrations of the drugs. Growth delay was more pronounced with Flu (up to 5.2 h), whereas the greatest decrease in log10 at 12 h was slightly more pronounced for AmB. A knowledge of PAFEs and the effects of low drug concentrations on pretreated yeasts and the effects of serum on these is important in order to gain more insight into the in vivo activity of the study drugs.

[Study of renal function after the administration of a low-osmolarity iodized contrast medium. Prospective study]

We analysed the development of various kidney function parameters in 40 patients on whom an intravenous urography had been carried out with a non-ionic contrast medium of low osmolarity (iohexol). No patient displayed prior renal insufficiency (serum creatinine 0.4-2mg/dl). Twenty-four hours after injection of the iodized contrast no significant variations in urea blood concentrations, creatinine, sodium or uric acid appeared. As a result of the urography an increase in urine osmolarity and a decrease in fractional sodium excretion took place.

IN CONCLUSION

in patients without renal insufficiency intravenous urography with iohexol does not give rise to a significant alteration in the renal excretory function.

[Traumatic sectioning of the isthmus in a case of renal fusion]

In this paper, we present a case of traumatic sectioning of the isthmus in a patient with multiple injuries, suffering from a horse-shoe-shaped kidney, which is extremely rare, according to the review of the literature which we have carried out. In view of the scanty incidence of kidney fusions and the difficulty sometimes involved in classifying them and in their surgical treatment, we shortly comment on the consequences which traumatisms may have on this kind of kidney malformation.

Radiological characteristics of perforated pulmonary hydatid cysts

Perforation of pulmonary hydatid cysts into the bronchial tree was seen in 56 of 239 cases. The resulting radiological signs are much more specific than those seen prior to perforation. These signs are described and correlated with the cystic structures that give rise to them. Perforation into the pleural cavity, seen in 5 cases, may result in secondary hydatidosis, as happened in one case.