High Percentage Of Positive Samples Research Articles

CHLAMYDOPHILA PSITTACIINFECTIONS IN HYACINTH MACAWS (ANODORHYNCHUS HYACINTHINUS) CONFISCATED IN BRAZIL

The hyacinth macaw (Anodorhynchus hyacinthinus) is the largest species of psittacine birds. It is considered endangered and illegal trade is one of the main factors involved in its decline. In this study, 26 hyacinth macaws maintained under poor husbandry conditions and destined for the illegal trade were confiscated in São Paulo State, Brazil. These birds were evaluated for the presence of antibodies against Chlamydophila psittaci by complement fixation test and C. psittaci DNA by seminested polymerase chain reaction. Results showed that 65.4% of the macaws were positive for at least one test. Birds with subclinical infections can shed chlamydiae intermittently over long periods, contributing to the dissemination of the agent. Global trade is one of the most important drivers of disease emergence. The high percentage of positive samples in this study emphasizes the potential risk that the illegal trade of wild birds represents for both human and animal health.

Diversity of C. difficile PCR ribotypes isolated from hospitalised patients in Slovenia during two-winter-month period.

Background : Clostridium difficile is an important cause of nosocomial diarrhoea. Strains are further differentiated into PCR ribotypes, and some ribotypes (e.g. 027) are often associated with outbreaks, increased disease severity and increased mortality. Here we describe the diversity of C. difficile among human isolates in Slovenia. Methods : All eight microbiological diagnostic laboratories providing C. difficile diagnostics in Slovenia have participated. Isolates from two–month- winter period were collected and ribotyped. The following data were also collected from the laboratories: number of all tested samples, number of all positive samples, and patient age and gender. Results : In a two-month period, altogether 860 samples were tested for C. difficile in all participating laboratories. Of those, 154 (17.9 %) samples from 125 patients were positive. The percentage of positive samples in different laboratories ranged from 13.3 to 43.2 %. Two out of eight laboratories did not have positive samples. C. difficile strains (n= 149) were grouped into 35 ribotypes. However, 57.7 % of all strains belonged only to two PCR ribotypes (027 and 014/020). PCR ribotype 027 was not present in Slovenia until 2010, but was in this study the most prevalent PCR ribotype and present mainly in the northeast region. Conclusions : There is a substantial diversity of C. difficile ribotypes in Slovenia. A high prevalence of ribotype 027 and a high percentage of positive samples in some laboratories indicate the presence of C. difficile outbreaks.

Development of A Monoclonal Antibody-Coated Immunomagnetic Beads for Separation and Detection of Norovirus (Genogroup II) in Oysters

The present study aimed to develop and evaluate a reverse transcription- polymerase chain reaction (RT-PCR) assay that incorporated immunomagnetic beads (IMS/RT-PCR) coated with a monoclonal antibody (Mab) for the separation and detection of noroviruses (NVs, genogroup II) in oysters. Mab-coated beads and polyclonal antibody (Pab)-coated beads were added to oyster extracts containing a series of tenfold dilution of NVs-positive fecal extracts. The oyster extracts were also treated with Proteinase K method. RNA was extracted and used as template for RT-PCR. Mab-based IMS/RT-PCR could detecte 10 RT PCR unit in oyster homogenate, it was 10 times more sensitive than Pab-based IMS/RT-PCR, and 102 times more sensitive than proteinase K/RT-PCR. Analysis of 473 oysters showed that Mab-based IMS/RT-PCR has the highest percentage of positive samples (5.29%), followed by Pab-based IMS/RT-PCR (3.81%), and proteinase K/RT-PCR (2.11%). Mab-based IMS/RT-PCR is a sensitive method for the detection of NVs in oysters and could be a good candidate for routine screening and risk assessment.

Comparison of three diagnostics methods of Mycoplasma gallisepticum in Batna governorate (Algeria)

Mycoplasma gallisepticum infection is commonly designated as chronic respiratory disease in chickens. It is the most pathogenic avian Mycoplasma; however, strains may differ markedly in virulence. In this study, the technical performance of culture, a commercially available polymerase chain reaction (PCR) test and rapid plate agglutination (SPA) test were compared for the detection of Mycoplasma gallisepticum infections from 18 birds. Results showed a high percentage of positive samples of both culture and PCR tests (72.22% and 63.63% respectively). SPA showed a less positive rate (61.11%). the utilization of SPA towards MG diagnosis is limited by its reduced specificity and the high incidence of false positives Contradictory to other studies, bacteriology was more sensitive than PCR. Several studies support strongly the use of the PCR as a technique for the diagnosis of Mycoplasma infections since this technique is more sensitive than serology and culture. This study showed that it is not advisable to rely completely on one test (system) only.

Usefulness of rickettsial PCR assays for the molecular diagnosis of human rickettsioses

BackgroundThe effectiveness of PCR methods to amplify rickettsiae from clinical samples has still not been evaluated. Our aim was to determine the sensitivity and usefulness for Rickettsia species identification by PCR methods, targeting 16S rDNA, htrA, gltA, ompA, and ompB genes for molecular diagnosis of rickettsioses. MethodsA total of 72 clinical samples (EDTA-blood, skin biopsies and ticks) taken from 52 patients in the early phase of the illness with PCR-confirmed rickettsioses were included. Single [16S rDNA, gltA (5′ end), and htrA genes] and sequential (nested or semi-nested) PCR assays [ompB, gltA (central region) and ompA genes] were performed. ResultsFor single-stage PCR assays, the greatest sensitivity (33.3%) was obtained using the gltA (5′ end), while for sequential assays, the most sensitive results were obtained using the ompB assay (83.3%). The highest sensitivity (100%) was achieved using the three sequential PCRs. The ompA PCR method was the most reliable for identifying Rickettsia species, according to clinical features. ConclusionsPCR-based amplification methods are useful rickettsial diagnostic tools in the early phase of the illness. The three sequential PCR assays here investigated (ompB, gltA and ompA) appear to be useful tools for molecular diagnosis of rickettsioses. ompB PCR assay is effective for primary screening, since it detects a high percentage of positive samples. ompA assay is the most useful method to identify a Rickettsia species in human pathology. Nevertheless, epidemiology, clinical symptoms and the vector involved in the infection have to be taken into account for the diagnosis of rickettsioses.

Epidemiological study of Chlamydophila psittaci in pet birds in Croatia

A total of 411 samples from birds of different species originating from all counties of the Republic of Croatia have been tested for the presence of Chlamydophila psittaci. The sampling was conducted in pet stores, breeders' aviaries, in a specialized bird clinic and in zoos. The testing included 177 parrots, 169 pigeons, 58 canaries and 7 finches. For the detection of specific C. psittaci antigen a commercial ELISA kit was used- IDEIATM PCE Chlamydia (DAKO Cytomation Ltd., United Kingdom). The samples that were non-specifically positive or doubtful in the ELISA test (a total of 26 samples) were analyzed also by means of polymerase chain reaction (PCR). Diagnostic ELISA method found a total of 17.03% birds positive for chlamydiosis, and after additional testing by PCR a total of 12.65% positive ones were found. According to bird species, the most frequently positive ones were canaries and pigeons (15.52% and 13.02%), and according to the sampling location most of the positive birds were found in pet stores (16.52%), but a high percentage of positive samples were also found in breeders’ aviaries (11.76%). The average positive result for chlamydiosis in 12.65% of tested birds is alarming and it confirms the importance of monitoring bird health and of prescribed legal regulations when it comes to chlamydial diseases, as well as education of persons involved in breeding, keeping or selling birds.

Use of a multivariate approach to assess the incidence of Alicyclobacillus spp. in concentrate fruit juices marketed in Argentina: Results of a 14-year survey

The purpose of this study was to determine the incidence of Alicyclobacillus spp. in fruit/vegetable juices (concentrated pulps and clarified and non-clarified juices) marketed in Argentina between 1996 and 2009. The presence of Alicyclobacillus was determined in a total of 8556 samples of fruit and vegetable juices (apple, pear, grape, peach, blend of juices, tangerine, pineapple, orange, mango, plum, guava, apricot, lemon, banana, kiwi, carrot, strawberry, grapefruit, and beetroot) collected in seven Argentinean provinces. Multiple factor analysis (MFA) was carried out on a data matrix that contained the percentage of positive samples, type of juice, raw material and production year. Except for kiwi and orange, Alicyclobacillus was found in juices from all the evaluated raw materials. The highest percentage of positive samples was found for beetroot, strawberry, banana, peach, mango, carrot and plum juices. The percentage of positive samples for these juices ranged from 100% to 24%. Furthermore, the application of multivariate techniques provided an insight on the relationship between the incidence of Alicyclobacillus and production variables. This approach enabled the identification of the most relevant variables that increased the percentage of positive samples among the juices, which could help in developing strategies to avoid the incidence of this bacterium. By means of hierarchical cluster analysis seven groups (clusters) of juices which showed different percentages of positive samples for Alicyclobacillus spp. were identified. This analysis showed that pineapple, peach, strawberry, mango and beetroot juices had higher rates of positivity for Alicyclobacillus than the rest of the evaluated juices. MFA analysis also showed that some clear relationships could be highlighted between the percentage of samples positive for Alicyclobacillus and five types of fruit juices (strawberry, beetroot, grapefruit, pineapple and mango). It was observed that a large proportion of juices produced in 2000, 2005 and 2008 were located in clusters with higher incidence of Alicyclobacillus spp., whereas a larger proportion of clarified concentrate juice and concentrate pulp samples showed higher probability of incidence of Alicyclobacillus in these products. Data presented in this study brings a contribution to the ecology of Alicyclobacillus in fruit/vegetable juices marketed in Argentina. This information would be useful to enhance the microbiological stability of fruit juices regarding the presence of Alicyclobacillus spp.

Assessment of PCBs exposure in human hair using double focusing high resolution mass spectrometry and single quadrupole mass spectrometry

Polychlorinated biphenyls (PCBs) levels were assessed in human hair samples, originating from two main agricultural regions of Greece. The analysis was performed by gas chromatography–mass spectrometry (GC–MS) and gas chromatography–double focusing high resolution mass spectrometry (GC–DFHRMS). The main analytical procedure involved hair decontamination, solid–liquid extraction and cleanup steps. The recoveries of PCBs ranged from 71.2% to 101.6%, with accuracies greater than 87.5% and the between-run precisions (%RSD) lower than 25% for all analytes. Differences in the frequencies of detection and the median values of PCBs were detected between the examined regions and between the applied analytical techniques. All Peloponnesus’ hair examined samples were found positive for each examined PCB, while the percentage of the total positive samples ranged from 86.1% (for PCB 138) to 94.4% (for PCB 28 and 153 congeners) using GC–DFHRMS. The Cretan hair samples were less contaminated (SUM PCBs=0.61 and 1.47pg/mg) unlike the Peloponnesus’ samples (SUM PCBs=24.68 and 38.74pg/mg) measured by GC–DFHRMS and GC–MS, respectively. PCBs with high chlorination gave lower concentration values compared to low chlorination PCBs in both populations. No significant differences were observed between women and men. The GC–DFHRMS technique provided higher percentage of positive samples and low PCBs median values, due to higher sensitivity and interferences from isobaric ions in the GC–MS technique and is therefore considered as a powerful tool for such assessments in hair specimens.

Evidência molecular de Brucella sp. em Ozotoceros bezoarticus (veado campeiro) do Pantanal Sul-Mato-Grossense

A presença de Brucella spp. entre animais silvestres pode influenciar a taxa de reprodução destes hospedeiros, além de atuarem como fonte de infecção natural para os animais domésticos e humanos. O objetivo deste estudo foi identificar a presença de Brucella spp. em 44 amostras de sangue de veado campeiro (Ozotoceros bezoarticus) do Pantanal do Sul-Mato-Grossense, utilizando a técnica de PCR. Observou-se que 20,4% (9/44) das amostras foram positivas. A sequência consenso de nucleotídeo obtida no sequenciamento do isolado de veado campeiro apresentou 514 pb e 95% de identidade com virB5 de B. abortus (best hits acesso nr AF226278, e-value 0.0), já na análise filogenética a amostra de Brucella isolada de veado campeiro apresentou-se muito próximo de B. suis. A alta porcentagem de amostras positivas sugere que a brucelose pode ser um problema entre os veados campeiros na área estudada e que estes animais podem representar riscos para outros animais domésticos e silvestres.

Non-tuberculous mycobacteria and microbial populations in drinking water distribution systems.

Data on the occurrence of non-tuberculous mycobacteria (NTM), in parallel with those obtained for bacterial indicators and amoebae, are presented with the aim to collect information on the spread of NTM in drinking water distribution systems in Italy. Samples were collected from taps of hospitals and households in Central and Southern Italy. The concentration values obtained for the more traditional microbial parameters complied with the mandatory requirements for drinking water. Conversely, moderate-to-high microbial loads (till 300 CFU/L) were observed for the NTM. Positive samples were obtained from 62% of the investigated water samples. Analogous results were observed for amoebae showing a higher percentage of positive samples (76%). In terms of public health, the presence of mycobacteria in water distribution systems may represent a potential risk especially for vulnerable people such as children, the elderly or immunocompromised individuals.

Regulation of Prostate Cancer Progression by Galectin-3

Galectin-3, a beta-galactoside-binding protein, has been implicated in a variety of biological functions including cell proliferation, apoptosis, angiogenesis, tumor progression, and metastasis. The present study was undertaken to understand the role of galectin-3 in the progression of prostate cancer. Immunohistochemical analysis of galectin-3 expression revealed that galectin-3 was cleaved during the progression of prostate cancer. Galectin-3 knockdown by small interfering RNA (siRNA) was associated with reduced cell migration, invasion, cell proliferation, anchorage-independent colony formation, and tumor growth in the prostates of nude mice. Galectin-3 knockdown in human prostate cancer PC3 cells led to cell-cycle arrest at G(1) phase, up-regulation of nuclear p21, and hypophosphorylation of the retinoblastoma tumor suppressor protein (pRb), with no effect on cyclin D1, cyclin E, cyclin-dependent kinases (CDK2 and CDK4), and p27 protein expression levels. The data obtained here implicate galectin-3 in prostate cancer progression and suggest that galectin-3 may serve as both a diagnostic marker and therapeutic target for future disease treatments.

Isolation and sources of ‘blown pack’ spoilage clostridia in beef abattoirs

(i) To evaluate methods for isolation and molecular detection of blown pack spoilage (BPS) clostridia and (ii) to survey beef abattoirs for sources and distributions of Clostridium estertheticum and Cl. gasigenes. Molecular detection and conventional isolation methods were used to detect and recover BPS associated clostridia (Cl. estertheticum and Cl. gasigenes), from four commercial Irish beef abattoirs and their environments, during a one year study. DNA-based methods detected 218 Cl. estertheticum and 300 Cl. gasigenes, from 1680 samples, whereas culture-methods only yielded 17 Cl. estertheticum and 176 Cl. gasigenes isolates. BPS Clostridia were frequently detected in beef abattoirs and their environments, especially at areas prior to hide removal. The study noted a higher percentage of positive samples during the month of May (38.6%). (i) DNA-based techniques are the most reliable ways to determine the presence of these organisms in various samples and (ii) hides and faeces are the main reservoirs of BPS clostridia in the abattoirs. This paper provides useful information to detect BPS organisms, as well as to develop a science-based control strategy of the problem.

Statistical limitations in the usefulness of total coliform data

Most water systems— rates of coliform‐positive samples are well below the 5% trigger for the monthly maximum contaminant level (MCL) set by the Total Coliform Rule (TCR). This study reviewed results of 540,357 samples collected from 15 systems and represented more than 12 years of sampling. Of these samples, 3,912 (0.72%) tested positive for total coliform and 79 (0.01%) tested positive for Escherichia coli. No correlations were observed between samples positive for total coliform and any available environmental data, including chlorine residuals. Small systems (serving 501‐3,300 people) and very small systems (serving 500 or fewer people) had a significantly higher percentage of positive samples, but values in general remained far below the monthly MCL. No clear patterns in the number of violations by system type were discerned. According to a power analysis of these data, under current sampling strategies, few systems will be able to detect the effects of any mitigation following TCR violations because sample sizes are too small. Water systems taking fewer than 250 samples per month cannot detect changes smaller than 2.5%. For most water providers, detecting the effects of mitigation will require pooling multiple months of data before and after a corrective action is taken.

Use of secondary enrichment for isolation of Salmonella from naturally contaminated environmental samples

Since the implementation of Hazard Analysis Critical Control Point (HACCP), the need for on-farm food safety risk assessment and management has greatly increased. In order to provide accurate risk assessments, attention should be focused on better characterization of the Salmonella isolation and identification techniques. In this work, we compared the isolation ability of 4 Salmonella-specific protocols: immunomagnetic separation (DB), tetrathionate (TT) broth, Rappaport-Vassiliadis R10 (RV) broth, and a secondary enrichment (TR) procedure as well as 2 selective solid media (brilliant green agar, BG; and xylose-lysine tergitol 4, XLT4). All 4 methods were compared in litter and drag swab samples that were collected weekly during the broiler grow out period in 7 houses. There were 65/126 (51.6%) pooled litter samples positive and 115/304 (37.8%) drag swab samples positive for Salmonella by at least one method. Of the 65 positive litter samples, DB, RV, and TT isolated 1 (2.7%), 31 (47.7%), and 23 (35.4%) of the samples as positive when using BG agar, respectively. The TR protocol identified 83.1% (54/65) of the positive samples as positive when using BG agar. In the drag swab samples, DB did not identify any samples as positive, whereas TT and RV found 28 (25.7%) and 26 (23.9%) of the 109 samples to be positive when using BG agar, respectively. Again, the TR protocol identified the highest percentage of positive samples (94.5%). An analysis of agreement, kappa, revealed that TT and RV did not always agree on which samples were positive, although the number of samples identified as positive by both were not different. A comparison between the 2 agar plates used, BG and XLT4, showed that they had high agreement when the secondary enrichment protocol was used, but agreement was only moderate to low when the other 3 methods were used.

Eliminação de oocistos de Cryptosporidium parvum por ovelhas e cordeiros confinados

Este experimento foi realizado com o objetivo de determinar a variação na eliminação de oocistos de Cryptosporidium parvum nas fezes de cordeiros e ovelhas, mantidos confinados do nascimento a desmama, em uma criação localizada em Botucatu -SP. Um grupo de 20 ovelhas da raça Ile de France em final de gestação foi confinado em instalações com piso de concreto. O piso era lavado três vezes por semana e as fezes eram removidas diariamente. O nascimento dos cordeiros ocorreu em Agosto e Setembro/2001. Amostras de fezes foram colhidas das ovelhas e dos cordeiros no dia do nascimento, 4, 8, 16, 32 e 64 dias pós-parto. As amostras foram processadas pela técnica de centrífugo-sedimentação em éter. Esfregaços foram confeccionados e corados com auramina O e pela técnica de Ziehl-Neelsen modificada. Do total de amostras de cordeiros e ovelhas, 26,7% e 31,9%, respectivamente (P>;0,05) apresentaram oocistos de Crypostosporidium. Quatro dos 20 cordeiros e duas das 20 ovelhas não apresentaram oocistos em nenhuma das amostras examinadas. O percentual mais alto de amostras positivas ocorreu nas amostras dos cordeiros com quatro dias de vida. Nas ovelhas o maior percentual de amostras positivas foi registrado quatro dias após o parto. Apesar da taxa relativamente elevada de animais que eliminaram oocistos nas fezes, a infecção por C. parvum foi subclínica nas ovelhas e nos cordeiros.

Comparison of Culture, PCR, and Different Serologic Tests for Detection of Mycoplasma gallisepticum and Mycoplasma synoviae Infections

In this study, the technical performance of culture, two commercially available polymerase chain reaction (PCR) tests, rapid plate agglutination (RPA) test, hemagglutination inhibition (HI) test, and eight commercially available enzyme-linked immunosorbent assays (ELISAs) were compared for the detection of avian mycoplasma infections from 3 days postinfection (d.p.i.) through 35 d.p.i. The tests were carried out on samples from specified pathogen-free layers that were infected at 66 wk of age with recent Mycoplasma synoviae (MS) and Mycoplasma gallisepticum (MG) field strains, MS and MG ATCC strains, and Mycoplasma imitans (MIM), respectively. Results showed a high percentage of positive samples in the homologous infected groups and a high percentage of negative samples (100%) in the uninfected and heterologous infected groups during 35 d.p.i. of both culture and PCR tests. For the group infected with the MG 15302 ATCC strain, serology was more sensitive than bacteriology. All MG and MS tests, with the exception of MG ELISA kit D showed a lower percentage of positive samples during 35 d.p.i. for the detection of the MG and MS ATCC strain infection compared with that of the field strains. Also, the number of cross-reactions (false positives) in the serologic tests was lower after infection with an ATCC strain than after an infection with the MG or MS field strain. Contradictory to other studies, the ELISAs and the RPA test using undiluted serum showed a relatively high number of false-positive results. The MG ELISAs (except ELISA kit D) showed more false-positive results (up to 37%) in the MIM-infected group than in the MS-infected groups. This was not unexpected, as MIM and MG have a close antigenic relationship. The results of the serologic tests in this study showed that a certain level of false-positive results can be expected in about any serologic test. Although the level of false-positive results varied between several serologic tests, this study showed that it is not advisable to rely completely on one test (system) only.

Pesticide residues survey in citrus fruits

The use of pesticides is widespread in citrus fruits production for pre- and post-harvest protection and many chemical substances may be applied in order to control undesirable moulds or insects. A survey was carried out to evaluate levels of pesticide residues in citrus fruits. Two multiresidue analytical methods were used to screen samples for more than 200 different fungicides, insecticides and acaricides. A total of 240 samples of citrus fruits including lemon, orange, mandarin, grapefruit, lime, pomelo and kumquat were taken in various markets in the Geneva area during the year 2003. Ninety-five percent of the 164 samples issued from classical agriculture contained pesticides and 38 different compounds have been identified. This high percentage of positive samples was mainly due to the presence of two post-harvest fungicides, imazalil and thiabendazole, detected in 70% and 36% of samples respectively. Only three samples exceeded the Swiss maximum residue limits (MRLs). Fifty-three samples sold with the written indication “without post-harvest treatment” were also controlled. Among theses samples, three exceeded the Swiss MRLs for penconazole or chlorpyrifos and 18 (34%) did not respect the written indication since we found large amounts of post-harvest fungicides. Finally, 23 samples coming from certified organic production were analysed. Among theses samples, three contained small amounts of pesticides and the others were pesticides free.

Occurrence of Cryptosporidium oocysts in sewage effluents and correlation with microbial, chemical and physical water variables.

Contaminated water are recognized as a potential source of Cryptosporidium oocysts. In Italy studies on the environmental spread of the parasite are still scarce even if a high frequency of serological responses could suggest high rates of endemic Cryptosporidium infections. In this investigation the occurrence of the parasite in water samples from a municipal wastewater treatment plant was monitored with the aim to evaluate possible correlation between oocysts and bacterial indicators, pathogens and physico-chemical parameters using a multivariate analysis. Data collected showed high numbers of oocysts, with a high percentage of positive samples and a significant correlation with pH, redox potential and total organic carbon. No correlation was found between Cryptosporidium concentration and that of the other microrganisms. The results, through a probing statistical analysis, show that none of the selected microrganisms was a reliable predictor of the presence of the parasite.

Human exposure to endocrine disrupters: Standardisation of a marker of estrogenic exposure in adipose tissue

In many epidemiological studies based on the direct measurement of exposure to organochlorines, the chemicals of concern are determined directly from adipose tissue samples. Although the measurement of all possible organochlorines, their metabolites, isomers and congeners may be desirable, it is expensive and time‐consuming and many chemicals with hormonal activity may not yet have been identified. Testing systems are therefore required to screen for estrogenicity and to identify appropriate biomarkers of human exposure. To address this issue, we developed and standardised a method to assess the total estrogenic xenobiotic burden in human adipose tissue. The method extracts and separates the more lipophilic xenoestrogens from ovarian estrogens, with a subsequent bioassay determination of the cumulative effect of the xenoestrogens. It was applied to 400 women, using 200 mg of adipose tissue: 65% of samples showed measurable estrogenicity in the fraction where most non‐polar xenoestrogens eluted, and 76% of fractions where ovarian estrogens eluted were positive for estrogenicity. Residues of 16 organochlorine pesticides were determined. No correlation was found between pesticide content and estrogenicity of the samples. The high percentage of positive samples suggests that the method is sensitive enough to be used as a biomarker of human exposure to estrogenic xenobiotics and can be applied in epidemiological studies.

Human exposure to endocrine disrupters: standardisation of a marker of estrogenic exposure in adipose tissue.

In many epidemiological studies based on the direct measurement of exposure to organochlorines, the chemicals of concern are determined directly from adipose tissue samples. Although the measurement of all possible organochlorines, their metabolites, isomers and congeners may be desirable, it is expensive and time-consuming and many chemicals with hormonal activity may not yet have been identified. Testing systems are therefore required to screen for estrogenicity and to identify appropriate biomarkers of human exposure. To address this issue, we developed and standardised a method to assess the total estrogenic xenobiotic burden in human adipose tissue. The method extracts and separates the more lipophilic xenoestrogens from ovarian estrogens, with a subsequent bioassay determination of the cumulative effect of the xenoestrogens. It was applied to 400 women, using 200 mg of adipose tissue: 65% of samples showed measurable estrogenicity in the fraction where most non-polar xenoestrogens eluted, and 76% of fractions where ovarian estrogens eluted were positive for estrogenicity. Residues of 16 organochlorine pesticides were determined. No correlation was found between pesticide content and estrogenicity of the samples. The high percentage of positive samples suggests that the method is sensitive enough to be used as a biomarker of human exposure to estrogenic xenobiotics and can be applied in epidemiological studies.