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Biomedical subjects

J M Echevarría

Publications and source records attributed to J M Echevarría.

At least 19 recordsLinked to original sources
PubMed2004

Evaluation of an automated complement-fixation test (Seramat) for diagnosis of acute respiratory infections caused by viruses and atypical bacteria.

The complement-fixation test (CFT) permits low-cost screening of serum samples for different agents within a single assay, and is a useful tool for the serological diagnosis of acute respiratory infections. This study evaluated the automated Seramat CFT system with 160 paired serum samples taken from 80 patients with acute respiratory infection in comparison with in-house CFTs against a panel of agents, including influenza A and B, adenovirus, respiratory syncitial virus, cytomegalovirus, Mycoplasma pneumoniae, Coxiella burnetti and Chlamydia spp., and in comparison with indirect immunofluorescence (IIF) against Legionella pneumophila. Overall, the Seramat system identified 75 (88.2%) of the 85 seroconversions recognised by in-house CFTs or IIF. In comparison to the in-house CFTs, the correlation was 89.2% (66/74). For L. pneumophila, the Seramat system detected nine (81.8%) of the 11 cases diagnosed by IIF. The Seramat system also identified eight additional seroconversions that were not detected by the in-house assays; none of these seroconversions was detected by the in-house assay on retesting. The Seramat system represents a significant technical improvement that may enable many clinical laboratories to use the CFT as a routine diagnostic tool.

Acute Disease↗
PubMed2000

Detection of specific IgM antibody in the investigation of an outbreak of pneumonia due to Legionella pneumophila serogroup 1.

OBJECTIVE: Management of outbreaks of pneumonia due to Legionella pneumophila serogroup 1 (SG1) infection requires rapid and accurate diagnostic tests. Current serologic approaches, based on detection of seroconversion for total antibody, do not fulfil this requirement. METHODS: A diagnostic test based on detection of IgM antibody to L. pneumophila SG1 by indirect immunofluorescence was developed and used to evaluate serum samples from patients involved in a community outbreak of L. pneumophila SG1 pneumonia that occurred in Spain. RESULTS: Testing of samples from serologically proven, sporadic cases of pneumonia due to L. pneumophila SG1 (14), cases of atypical pneumonia due to other infectious agents (16) and healthy controls (100) supported the sensitivity and specificity of the assay. On samples from the outbreak, the IgM assay recognized five of six cases with isolation of L. pneumophila SG1 from respiratory secretions or lung tissue and more than 70% of cases with confirmed or presumptive diagnosis as determined by the current serologic criteria. In addition, the IgM assay was positive in 23-70% of patients who fulfilled the clinical and epidemiologic criteria of case definition but did not display diagnostically significant serologic results or who lacked a detectable antibody response in the routine assay. Among cases confirmed by the current criteria, detection of specific IgM was occasionally achieved before the conventional serology gave significant results. CONCLUSION: Incorporation of IgM antibody detection in the current diagnostic criteria for L. pneumophila SG1 infection may help to improve the management of outbreaks of pneumonia due to this agent.

Antibodies, Bacterial↗
PubMed1999

Viral diagnosis of neurological infection by RT multiplex PCR: a search for entero- and herpesviruses in a prospective study.

The diagnosis of a wide range of different neurological syndromes was established by a reverse transcription multiplex PCR assay. The presence of enterovirus and herpesviruses was studied in cerebrospinal fluid samples collected prospectively from 200 patients hospitalized with neurological diseases suspected of viral infection. Positive PCR results for enterovirus and neurotropic herpesvirus (herpes simplex, HSV, and varicella zoster, VZV) were obtained among the immunocompetent patients (55/156, 35%) who presented aseptic meningitis or encephalitis. Among immunocompromised patients the yield of positive PCR results was 41% (18/44), predominantly lymphotropic herpesviruses (15/44, 34%). Cytomegalovirus (CMV) DNA was detected in patients with several clinical syndromes, including encephalitis, chronic meningitis, retinitis, ventriculitis, polyradiculomyelitis, and myeloradiculitis. Epstein-Barr (EBV) and VZV-specific DNA sequences were detected in patients with either encephalitis, aseptic meningitis, and chronic meningitis. Dual infections of CMV and HSV or CMV and EBV were established in two AIDS patients with encephalitis and polyradiculomyelitis, respectively. The applications of this RT multiplex PCR assay are extensive and may prove to be particularly valuable for the rapid and sensitive diagnosis of neurological diseases in both immunocompetent and immunocompromised patients.

Adult↗
PubMed1999

[Prevalence of infections by hepatitis B, C, D and E viruses in Bolivia].

In Bolivia, no studies have been carried out specifically on hepatitis viruses. Thus, their prevalence and circulation patterns are virtually unknown. A seroepidemiologic study was performed from 1992 to 1996 to generate a preliminary idea of the overall prevalence of infection from hepatitis B, C, D, and E viruses (HBV, HCV, HDV, and HEV, respectively) in different Bolivian population groups. Prompted by the data obtained in other areas of Latin America, the study focused on indigenous communities in the Amazon region. In rural areas of the high Andean plateau, HBV infection showed an overall prevalence compatible with medium to low endemicity (11.2%), and no carriers of HCV or HDV antibodies were found. In two high-risk groups in the city of Cochabamba (homeless children and sexual workers), the prevalence of HBV infection was similar (11.6%) and could be considered low by comparison to that of similar population groups in Latin American urban centers. The prevalence of HCV (one positive case, or 0.5%) was similar to that found in similar population groups, although the small number of samples precludes drawing more definite conclusions. As has been noted previously with similar communities in tropical areas of South America, HBV infection is highly endemic in indigenous populations of the Bolivian Amazon (with an overall prevalence of 74.0%), but circulation of HCV has not been detected. It is a well-known fact that HBV is horizontally transmitted and that transmission can take place very early in life, but the mechanisms involved are unknown. By 10 years of age, more than half the population has already had the natural infection that, in approximately 10 more years will have affected virtually the entire population. The very low rate of positivity to HBsAg (1.6%), the absence of viral DNA in samples showing isolated positivity to anti-HBc, and the high prevalence of anti-HBs among individuals who show markers for natural infection (92.4%) suggest vertical transmission plays no role in persistent endemicity. So far, no outbreak of HDV infection has been documented in these communities, but the high endemicity shown by HBV points to the possibility of future outbreaks. Results obtained with tests for the detection of antibodies against HEV suggest that this virus is circulating widely in Bolivia and that it could have caused recent outbreaks in Cochabamba state. Vaccination against HBV in endemic populations is recommended as a short-term measure. Also recommended are actively searching for outbreaks and sporadic cases of hepatitis E in the entire country and performing additional research that will help in assessing the public health consequences of the situation described in this article.

Adolescent↗
PubMed1999

[Prevalence of types of hepatitis C virus in Spanish blood donors: results of a state-based multicenter study. Spanish Group for the Study of Blood Donors with Risk of HCV Transmission].

BACKGROUND: The prevalences established up to the present in Spain for the different types of hepatitis C virus are based on data obtained in populations in which the nature of the population itself may have based the data in favor of certain types of the virus. The study of seropositive blood donors identified through screening of blood donations may provide prevalences closer to the truth among the general population. MATERIALS AND METHODS: Typing of genomes in samples from 441 donors was performed using the blood bank generated during the multicenter study performed by the Spanish Study Group of Blood Donors with Risk of Transmission of the Hepatitis C Virus. The antibodies present were typed in the seropositive samples in the above donors and in 337 more in whom a viral genoma was not detected. RESULTS: In total, the infection was typed in 685 donors. On analysis of the results corresponding to 386 donors, whose number and distribution by autonomous communities were previously fixed to represent all of Spain, type 1 was largely the more prevalent (85.5%) followed by types 3 (4.4%), 2 (4.1%), 4 (3.4%) and 5 (0.5%) and by a group of apparent mixed infections which altogether represented 2.1% of the total. Among the donors in whom the genomes were typed, infectious due to the 1b subtype (78% of the 441 samples genotypes) clearly predominated. The participation of the different types of type 1 was significantly greater in those lacking antibodies detectable versus epitopes codified in the NS4 region of the viral genome. CONCLUSIONS: This study avoids some bias in sampling which may have affected previous studies and provides data which should more closely approach the real prevalence in the general Spanish population. Thus, it should provide a better base of comparison for any study on the distribution of the types of the hepatitis C virus in selected populations or others performed during tha investigation of outbreaks of hepatitis C virus infection.

Blood Donors↗
PubMed1998

Antigenic diversity of hepatitis B virus strains of genotype F in Amerindians and other population groups from Venezuela.

The adw4 subtype of hepatitis B virus (HBV) belongs to a unique genomic group (genotype F) representing the original HBV strains from the New World. Data regarding the prevalence of this subtype among HBV carriers in South America are, however, scarce, and those concerning HBV genotype F are based on only a few samples from Latin America. In this study, serum samples were obtained from 141 hepatitis B surface antigen (HBsAg) carriers from Amerindians and urban populations from Venezuela. The HBsAg subtype was identified with monoclonal antibodies in 105 samples, and the HBV genotype was identified by reverse-phase hybridization with DNA fragments in 58 samples. The adw4 subtype was highly prevalent in the population studied (75%); among the Amerindians, the prevalence was 97%. The adw2 subtype was also present (10%), while other subtypes (ayw3 and ayw4) were only occasionally found. The HBV subtype was associated with the expected genotype in most cases (80%), and thus genotype F was highly prevalent. Sequencing of viral strains that gave genotypes unpredicted by the HBsAg subtyping confirmed seven of them as belonging to not previously described genotype-subtype associations: namely, adw2 and ayw4 within genotype F.

Amino Acid Substitution↗
PubMed1998

Use of overlapping synthetic peptides to characterize samples from blood donors with indeterminate results to hepatitis C virus core antigen.

BACKGROUND AND OBJECTIVES: Despite recent improvements in supplemental assays, isolated reactivity to the hepatitis C virus (HCV) core antigen continues as one of the main problems in the confirmation of anti-HCV in blood donors. Reactivity against individual peptides from the c22-3 HCV recombinant antigen has been described as a useful tool for anti-HCV confirmation and donor counseling in such cases. MATERIALS AND METHODS: We used a previously described set of overlapping peptides spanning the entire sequence of the c22-3 antigen to study 87 single serum samples from blood donors with reactivity for c22-3 antigen alone in second generation recombinant immunoblot assay (RIBA-2). All of them had been previously studied by RIBA-3, anti-HCV E2 EIA and HCV PCR. RESULTS: 66 of the 87 samples studied could be classified as positive or negative for anti-HCV core using the multipeptide assay and such classification correlated well with the results obtained with RIBA-3 and the anti-E2 EIA. However, some discrepancies were found. The epitopes located along the N-terminal half of the molecule were mainly responsible for the specific antibody recognition but those enclosed within amino acids 1-15 were frequently involved in nonspecific reactivity. Some 38% of samples were considered to have specific antibody to the c22-3 antigen and a further 9% reacted for both anti-E2 and single core peptides that were often involved in specific antibody recognition. CONCLUSION: Testing of blood donor samples indeterminate to the HCV c22-3 antigen for reactivity against individual core peptides can confirm the presence of specific antibody and recognize nonspecific reactivity with certain cross-reacting epitopes. Third generation supplemental tests have reduced such false reactivity, but confirmation of samples with anticore alone is still necessary. Single reactivity to the HCV core antigen is likely to reflect prior exposure to the virus, but rarely active infection, either acute or chronic.

Antibody Specificity↗
PubMed1997

Detection of enteroviral RNA and specific DNA of herpesviruses by multiplex genome amplification.

A reverse transcription (RT) multiplex polymerase chain reaction (PCR) assay was developed to allow rapid, sensitive and simultaneous detection of enteroviral RNA and herpesviral DNA specific sequences in a single tube. The method involves a reverse transcription step followed by a multiplex nested PCR in which the combination of primers amplifies cDNA from enteroviruses and specific herpesviruses DNA. Nested amplification utilises primers designed to anneal into the amplification product from the first reaction. Individual viruses were then detected and differentiated by the size of their PCR products determined using ethidium bromide stained agarose gels. To exclude false negatives due to sample inhibitors an internal amplification control, a cloned fragment of DNA from Pseudorabies virus (PRV DNA) was included in the reaction mixture. Detection levels between 0.01 and 0.001 TCID50 of prototype strains of Polio and Coxsackie type B viruses and between 1 and 100 molecules of cloned-DNA of herpesviruses prototype strains were achieved. The RT multiplex PCR method proved capable of detecting enteroviral RNA or herpesviral DNA in cerebro spinal fluid (CSF) samples from patients with aetiologically well characterized encephalitis or aseptic meningitis.

Child↗
PubMed1997

Typing of hepatitis C virus antibody with specific peptides in seropositive blood donors and comparison with genotyping of viral RNA.

BACKGROUND AND OBJECTIVES: Serotyping of antibody to hepatitis C virus (anti-HCV) with specific peptides has been developed as an alternate method for typing HCV infections. The method does not require a prior amplification of viral RNA sequences from the sample. Identification of the viral genotype may be relevant for prognosis and clinical management. MATERIALS AND METHODS: We used a previously described HCV serotyping assay (RIBA HCV Serotype SIA kit, Chiron Corp.) to investigate the serotype in 191 samples from blood donors selected for anti-HCV patterns (positive and indeterminate), ALT levels, and the presence or absence of viral RNA. The serotypes were compared with the genotypes obtained from typing the 5'-noncoding region of the viral RNA in 82 viremic samples. RESULTS: We were able to obtain the viral serotype in 85% (114/134) of samples positive for anti-HCV but in only 3.5% (2/57) of the indeterminates. Lack of anti-NS4 in the sample was significantly associated with both untypable results and the presence of HCV serotypes other than serotype 1. The overall correlation with genotyping was 78% (64/82), rising to 95.5% (64/67) if only samples that could be both genotyped and serotyped were considered. The assay was easy to perform, gave reactivity patterns easy to interpret, and performed with high proficiency on anti-HCV-positive samples lacking detectable levels of viral RNA. CONCLUSIONS: This is a practical and useful method for typing HCV infections in the clinical setting. The poor ability of the Core peptides to give the serotype in samples lacking anti-NS4 and the lack of specific peptides to recognize HCV types other than 1, 2, and 3 are, however, some aspects of the method that need improvement in the future.

Antibodies, Viral↗
PubMed1997

Infections of the nervous system caused by varicella-zoster virus: a review.

Varicella-zoster virus (VZV) is a cause of neurologic disease among humans. Both primary infection and recurrence may lead to neurologic infection and disease. Neurologic syndromes associated with acute VZV infection are caused by abnormal immune responses, the most frequent manifestation being cerebellar ataxia. Those associated with recurrences are often due to the direct effect of viral replication in the nervous tissue. VZV reaches the nervous system either through the bloodstream or by direct spread from sensory ganglia where it remains latent. Postherpetic neuralgia, acute encephalitis, aseptic meningitis and myelitis are the most frequent diseases and have been recorded both in association with herpes zoster and in the absence of a cutaneous rash. Early diagnosis may be established by detecting virus-specific DNA sequences in the cerebrospinal fluid (CSF) after amplification by the polymerase chain reaction and then confirmed by detection of intrathecally produced, specific IgG antibody. Virus isolation from CSF and antibody testing in serum are unsuitable for diagnosis. Early acyclovir therapy is recommended in immuno-compromised patients and those with serious disease.

Herpes Zoster↗