RESUMO
Blinded rechecking is a method proposed for external quality assurance (EQA) of auramine-stained acid-fast bacilli (AFB) smears using fluorescence microscopy (FM), however, this procedure is not well developed and slides fading over time could compromise its implementation. Since bleaching of fluorescent molecules involves temperature-dependent chemical reactions, it is likely that low temperatures could slow down this process. We stored auramine-stained slides under different environmental conditions, including -20°C, and examined them over time. The slides stored in all the environments faded. At -20°C, fading was not reduced in relation to room temperature. Restaining and re-examining smears after five months showed that the slides containing saliva and storage at -20°C were associated with failure in AFB reappearance. In conclusion, the practice of freezing slides until they are viewed should be discouraged as it has a negative effect on blinded rechecking by reducing reading concordance after restaining. Specimen quality should be considered when interpreting FM-EQA results.
Assuntos
Benzofenoneídio/efeitos da radiação , Corantes Fluorescentes/efeitos da radiação , Microscopia de Fluorescência/métodos , Fotodegradação , Garantia da Qualidade dos Cuidados de Saúde/métodos , Escarro/microbiologia , Coloração e Rotulagem/métodos , Tuberculose/diagnóstico , Argentina , Benzofenoneídio/análise , Criopreservação , Estudos de Viabilidade , Corantes Fluorescentes/análise , Humanos , Iluminação , Microscopia de Fluorescência/instrumentação , Variações Dependentes do Observador , Valor Preditivo dos Testes , Preservação Biológica/métodos , Reprodutibilidade dos Testes , Método Simples-Cego , TemperaturaRESUMO
Introduction. The performance of a drug susceptibility test may change when moving from the research stage to implementation on a population level in actual public health practice. Objective. The performance of a rapid drug susceptibility test was described for detecting multidrug-resistant Mycobacterium tuberculosis when implemented in the routine workflow of a low-resource reference laboratory. Materials and methods. A prospective study was done comparing the performance of the nitrate reductase assay with the conventional proportion method for rifampicin and isoniazid on 364 isolates were obtained from multidrug-resistant tuberculosis risk patients referred from diffrent Colombian laboratories. Results. When compared with the proportion method, the nitrate reductase assay sensitivity was 86.8% and 84.9% for rifampicin and isoniazid, respectively, whereas nitrate reductase assay specificity was 100% for isoniazid and rifampicin. Nitrate reductase assay sensitivity was significantly higher when the age of isolate was less than 70 days. A sensitivity of 94.4% dropped to 78.1% for rifampicin resistance for fresh and old isolates, respectively (Fisher exact test, p=0.05). For isoniazid resistance using fresh and old isolates, 94.7% vs.74.3% sensitivities, were achieved (chi square test, p=0.03). The proportion of nitrate reductase assay ambiguous results was significantly higher in multidrug-resistant than in non-multidrug-resistant isolates (17.6% vs. 4.0%, chi square test, p<0.005). Conclusions. The nitrate reductase assay demonstrated provided reliable results for antibiotic resistance. However, using old cultures leds to a higher proportion of false sensitive results; furthermore, the nitrate reductase assay capability to detect multidrug-resistant tuberculosis decreased due to a higher proportion of non-interpretable results.
Assuntos
Testes de Sensibilidade Microbiana/métodos , Mycobacterium tuberculosis/isolamento & purificação , Mycobacterium tuberculosis/patogenicidade , Nitrato Redutases , Tuberculose Resistente a Múltiplos Medicamentos/diagnóstico , Tuberculose Resistente a Múltiplos Medicamentos/microbiologia , Antituberculosos , Humanos , Isoniazida , Testes de Sensibilidade Microbiana/normas , Nitrato Redutases/metabolismo , Estudos Prospectivos , Saúde Pública , Rifampina , Sensibilidade e EspecificidadeRESUMO
Introducción. El rendimiento de cualquier prueba rápida de sensibilidad a medicamentos para Mycobacterium tuberculosis puede cambiar cuando se pasa de la etapa de investigación a su implementación en la práctica de salud pública. Objetivo. Describir el rendimiento del ensayo de nitrato reductasa para detectar tuberculosis multirresistente en la rutina de trabajo de un laboratorio de referencia con recursos limitados. Materiales y métodos. Se comparó prospectivamente la utilidad del ensayo de nitrato reductasa con el método de las proporciones para la detección de resistencia a isoniacida y rifampicina en aislamientos de pacientes con riesgo de multirresistencia. Resultados. Comparando con el método de las proporciones, la sensibilidad del ensayo de nitrato reductasa fue de 86,8 % y 84,9 % para rifampicina e isoniacida, respectivamente; la especificidad fue 100 % para rifampicina e isoniacida. La sensibilidad del ensayo de nitrato reductasa fue significativamente mayor cuando se emplearon aislamientos en los cuales el tiempo entre la realización del cultivo y la inoculación del ensayo de nitrato reductasa no superaba 70 días: 94,3 % Vs. 78,1 % para resistencia a rifampicina usando aislamientos frescos o envejecidos, respectivamente; prueba exacta de Fisher, p=0,05; 94,4 % Vs. 74,3 % para resistencia a isoniacida usando aislamientos frescos o envejecidos, respectivamente, y prueba de ji al cuadrado, p=0,03. La proporción de resultados no interpretables en el ensayo de nitrato reductasa fue mayor en los aislamientos multirresistentes que en los otros Conclusiones. La experiencia con el ensayo de nitrato reductasa demuestra que produce resultados resistentes confiables. El uso de cultivos envejecidos conduciría a una mayor proporción de resultados falsos sensibles, mientras que su capacidad para detectar multirresistencia disminuye a consecuencia de una mayor proporción de resultados no interpretables.
Introduction. The performance of a drug susceptibility test may change when moving from the research stage to implementation on a population level in actual public health practice. Objective. The performance of a rapid drug susceptibility test was described for detecting multidrugresistant Mycobacterium tuberculosis when implemented in the routine workflow of a low-resource reference laboratory. Materials and methods. A prospective study was done comparing the performance of the nitrate reductase assay with the conventional proportion method for rifampicin and isoniazid on 364 isolates were obtained from multidrug-resistant tuberculosis risk patients referred from diffrent Colombian laboratories. Results. When compared with the proportion method, the nitrate reductase assay sensitivity was 86.8% and 84.9% for rifampicin and isoniazid, respectively, whereas nitrate reductase assay specificity was 100% for isoniazid and rifampicin. Nitrate reductase assay sensitivity was significantly higher when the age of isolate was less than 70 days. A sensitivity of 94.4% dropped to 78.1% for rifampicin resistance for fresh and old isolates, respectively (Fisher exact test, p=0.05). For isoniazid resistance using fresh and old isolates, 94.7% vs.74.3% sensitivities, were achieved (chi square test, p=0.03). The proportion of nitrate reductase assay ambiguous results was significantly higher in multidrug-resistant than in nonmultidrug-resistant isolates (17.6% vs. 4.0%, chi square test, p<0.005). Conclusions. The nitrate reductase assay demonstrated provided reliable results for antibiotic resistance. However, using old cultures leds to a higher proportion of false sensitive results; furthermore, the nitrate reductase assay capability to detect multidrug-resistant tuberculosis decreased due to a higher proportion of non-interpretable results.
Assuntos
Testes de Sensibilidade Microbiana , Mycobacterium tuberculosis , Nitrato Redutase , MétodosRESUMO
The diagnostic test characteristics of detecting free and complex-dissociated IgG to three recombinant antigens of Mycobacterium tuberculosis (38-kDa, Ag16 and Ag85B), singly and in combination, were evaluated in sera from 161 tuberculous patients [smear-positive pulmonary TB (50), smear-negative pulmonary TB (pTBsm-) (60) and extrapulmonary TB (51)) and 214 control patients (mycobacteriosis (14), mycoses(14), leprosy(4), other underlying diseases (82) and healthy people (100)]. The individual antigens ranged from 25% to 42% in sensitivity and from 93% to 96% in specificity, while considering free IgG response. Addition of complex-dissociated antibodies against each individual antigen improved the sensitivity up to 55%. The number and levels of specific antibodies varied greatly from individual to individual. Combination of individual results for free and complex-dissociated IgG to 38-kDa, Ag16 and Ag85B offered 76% sensitivity and 83% specificity. When the three antigens were placed in the same well, the sensitivity was lower than that expected on the basis of single antigen (63%) but with a good specificity (95%), even in the group of mycobacteriosis or mycoses. The highest contribution of complex-dissociated IgG results to free IgG results was seen for the diagnosis of pTBsm- patients. In conclusion, although neither single recombinant antigen was reactive with most sera from TB patients even after the measurement of both free and complex-dissociated antibodies, the use of multi-antigen cocktails improved the diagnostic utility of the ELISA assay, allowing the identification of almost 70% of pTBsm-, with a high level of specificity; the use of additional, well selected antigens should lead to the detection of almost all patients with TB.
Assuntos
Anticorpos Antibacterianos/sangue , Complexo Antígeno-Anticorpo/sangue , Antígenos de Bactérias/imunologia , Imunoglobulina G/sangue , Mycobacterium tuberculosis/imunologia , Tuberculose/diagnóstico , Adolescente , Adulto , Idoso , Estudos de Casos e Controles , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina G/imunologia , Masculino , Pessoa de Meia-Idade , Proteínas Recombinantes/imunologia , Sensibilidade e Especificidade , Tuberculose/imunologia , Tuberculose Pulmonar/diagnóstico , Tuberculose Pulmonar/imunologia , Adulto JovemRESUMO
The diagnostic test characteristics of detecting free and complex-dissociated IgG to three recombinant antigens of Mycobacterium tuberculosis (38-kDa, Ag16 and Ag85B), singly and in combination, were evaluated in sera from 161 tuberculous patients [smear-positive pulmonary TB (50), smear-negative pulmonary TB (pTBsm-) (60) and extrapulmonary TB (51)) and 214 control patients (mycobacteriosis (14), mycoses(14), leprosy(4), other underlying diseases (82) and healthy people (100)]. The individual antigens ranged from 25 percent to 42 percent in sensitivity and from 93 percent to 96 percent in specificity, while considering free IgG response. Addition of complex-dissociated antibodies against each individual antigen improved the sensitivity up to 55 percent. The number and levels of specific antibodies varied greatly from individual to individual. Combination of individual results for free and complex-dissociated IgG to 38-kDa, Ag16 and Ag85B offered 76 percent sensitivity and 83 percent specificity. When the three antigens were placed in the same well, the sensitivity was lower than that expected on the basis of single antigen (63 percent) but with a good specificity (95 percent), even in the group of mycobacteriosis or mycoses. The highest contribution of complex-dissociated IgG results to free IgG results was seen for the diagnosis of pTBsm- patients. In conclusion, although neither single recombinant antigen was reactive with most sera from TB patients even after the measurement of both free and complex-dissociated antibodies, the use of multi-antigen cocktails improved the diagnostic utility of the ELISA assay, allowing the identification of almost 70 percent of pTBsm-, with a high level of specificity; the use of additional, well selected antigens should lead to the detection of almost all patients with TB.
Assuntos
Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem , Anticorpos Antibacterianos/sangue , Complexo Antígeno-Anticorpo/sangue , Antígenos de Bactérias/imunologia , Imunoglobulina G/sangue , Mycobacterium tuberculosis/imunologia , Tuberculose/diagnóstico , Estudos de Casos e Controles , Ensaio de Imunoadsorção Enzimática , Imunoglobulina G/imunologia , Proteínas Recombinantes/imunologia , Sensibilidade e Especificidade , Tuberculose Pulmonar/diagnóstico , Tuberculose Pulmonar/imunologia , Tuberculose/imunologia , Adulto JovemRESUMO
In order to assess laboratory resources, practices, and biosafety measures during mycobacterial testing and determine the usefulness and scope of mycobacterial techniques, a cross-sectional survey of public laboratories was conducted in Argentina using a structured questionnaire. Sputum smear analysis showed that both smear and culture testing centers are being provided at or above the WHO recommended density for such facilities. The microscopy quality assessment program covered most high-demand laboratories. Mean number of sputum smears per patient was low (1.6). The use of inadequate personal respiratory protection was identified in 25% of culture laboratories. Jurisdictions that cultured a higher proportion of their smear-tested sputa identified a higher proportion of smear-negative cases. The percentage of smear negatives among all bacteriologically confirmed pulmonary cases was 18.9%, while most extrapulmonary cases were confirmed by culture (71.3%). In conclusion, increasing the number of sputa studied by microscopy and culture (while expanding the coverage of the quality assessment program) is a priority; adequate respiratory protection and regular medical evaluation of laboratory staff is still needed in some laboratories.
Assuntos
Técnicas de Laboratório Clínico/normas , Pesquisas sobre Atenção à Saúde , Laboratórios/normas , Mycobacterium tuberculosis/isolamento & purificação , Tuberculose Pulmonar/diagnóstico , Argentina , Técnicas de Laboratório Clínico/métodos , Estudos Transversais , Humanos , Laboratórios/estatística & dados numéricos , Setor Público , Controle de Qualidade , Manejo de Espécimes , Coloração e Rotulagem , Inquéritos e QuestionáriosRESUMO
Con el objetivo de evaluar recursos, prácticas y medidas de bioseguridad utilizados en el diagnóstico bacteriológico de tuberculosis y determinar la utilidad y alcance de las técnicas empleadas, se llevó adelante una encuesta transversal a laboratorios del sector público de Argentina utilizando un cuestionario estructurado. El análisis de los resultados mostró que la densidad de centros de microscopía y cultivo se encuentra al nivel o encima de lo recomendado por Organización Mundial de la Salud. El programa de control de calidad de microscopía cubre mayoritariamente los laboratorios con alta carga de trabajo. El promedio de baciloscopías/paciente fue bajo (1,6). El 25 por ciento de los laboratorios de cultivo empleaban protección respiratoria inadecuada. El aporte del cultivo a la confirmación de casos pulmonares en las jurisdicciones estuvo asociado a la proporción de muestras cultivadas. Globalmente, el porcentaje de pacientes pulmonares baciloscopía-negativa que fue confirmado bacteriológicamente fue de 18.9 por ciento; mientras que la may-oría de los casos extrapulmonares se confirmó sólo por cultivo (71,3 por ciento). Es prioritario aún el incremento del número de esputos estudiados por baciloscopía y cultivo, así como aumentar la cobertura de programa de control de calidad de microscopía; es fundamental proveer al personal de laboratorio de adecuada protección respiratoria y evaluación médica regular.
In order to assess laboratory resources, practices, and biosafety measures during mycobacterial testing and determine the usefulness and scope of mycobacterial techniques, a cross-sectional survey of public laboratories was conducted in Argentina using a structured questionnaire. Sputum smear analysis showed that both smear and culture testing centers are being provided at or above the WHO recommended density for such facilities. The microscopy quality assessment program covered most high-demand laboratories. Mean number of sputum smears per patient was low (1.6). The use of inadequate personal respiratory protection was identified in 25 percent of culture laboratories. Jurisdictions that cultured a higher proportion of their smear-tested sputa identified a higher proportion of smear-negative cases. The percentage of smear negatives among all bacteriologically confirmed pulmonary cases was 18.9 percent, while most extrapulmonary cases were confirmed by culture (71.3 percent). In conclusion, increasing the number of sputa studied by microscopy and culture (while expanding the coverage of the quality assessment program) is a priority; adequate respiratory protection and regular medical evaluation of laboratory staff is still needed in some laboratories.
Assuntos
Humanos , Masculino , Feminino , Laboratórios/normas , Técnicas Bacteriológicas/normas , Tuberculose Pulmonar/diagnóstico , Tuberculose Pulmonar/microbiologia , Argentina , Setor Público , Controle de Qualidade , Inquéritos e Questionários , Técnicas Bacteriológicas/estatística & dados numéricosRESUMO
A study was carried out to compare the performance of a commercial method (MGIT) and four inexpensive drug susceptibility methods: nitrate reductase assay (NRA), microscopic observation drug susceptibility (MODS) assay, MTT test, and broth microdilution method (BMM). A total of 64 clinical isolates of Mycobacterium tuberculosis were studied. The Lowenstein-Jensen proportion method (PM) was used as gold standard. MGIT NRA, MODS, and MTT results were available on an average of less than 10 days, whereas BMM results could be reported in about 20 days. Most of the evaluated tests showed excellent performance for isoniazid and rifampicin, with sensitivity and specificity values > 90%. With most of the assays, sensitivity for ethambutol was low (62-87%) whereas for streptomycin, sensitivity values ranged from 84 to 100%; NRA-discrepancies were associated with cultures with a low proportion of EMB-resistant organisms while most discrepancies with quantitative tests (MMT and BMM) were seen with isolates whose minimal inhibitory concentrations fell close the cutoff MGIT is reliable but still expensive. NRA is the most inexpensive and easiest method to perform without changing the organization of the routine PM laboratory performance. While MODS, MTT, and BMM, have the disadvantage from the point of view of biosafety, they offer the possibility of detecting partial resistant strains. This study shows a very good level of agreement of the four low-cost methods compared to the PM for rapid detection of isoniazid, rifampicin and streptomycin resistance (Kappa values > 0.8); more standardization is needed for ethambutol.
Assuntos
Antituberculosos/farmacologia , Testes de Sensibilidade Microbiana/métodos , Mycobacterium tuberculosis/efeitos dos fármacos , Etambutol/farmacologia , Humanos , Isoniazida/farmacologia , Testes de Sensibilidade Microbiana/economia , Reprodutibilidade dos Testes , Rifampina/farmacologia , Sensibilidade e Especificidade , Estreptomicina/farmacologiaRESUMO
A study was carried out to compare the performance of a commercial method (MGIT) and four inexpensive drug susceptibility methods: nitrate reductase assay (NRA), microscopic observation drug susceptibility (MODS) assay, MTT test, and broth microdilution method (BMM). A total of 64 clinical isolates of Mycobacterium tuberculosis were studied. The Lowenstein-Jensen proportion method (PM) was used as gold standard. MGIT, NRA, MODS, and MTT results were available on an average of less than 10 days, whereas BMM results could be reported in about 20 days. Most of the evaluated tests showed excellent performance for isoniazid and rifampicin, with sensitivity and specificity values > 90 percent. With most of the assays, sensitivity for ethambutol was low (62-87 percent) whereas for streptomycin, sensitivity values ranged from 84 to 100 percent; NRA-discrepancies were associated with cultures with a low proportion of EMB-resistant organisms while most discrepancies with quantitative tests (MMT and BMM) were seen with isolates whose minimal inhibitory concentrations fell close the cutoff. MGIT is reliable but still expensive. NRA is the most inexpensive and easiest method to perform without changing the organization of the routine PM laboratory performance. While MODS, MTT, and BMM, have the disadvantage from the point of view of biosafety, they offer the possibility of detecting partial resistant strains. This study shows a very good level of agreement of the four low-cost methods compared to the PM for rapid detection of isoniazid, rifampicin and streptomycin resistance (Kappa values > 0.8); more standardization is needed for ethambutol.
Assuntos
Humanos , Antituberculosos/farmacologia , Testes de Sensibilidade Microbiana/métodos , Mycobacterium tuberculosis/efeitos dos fármacos , Etambutol/farmacologia , Isoniazida/farmacologia , Testes de Sensibilidade Microbiana/economia , Reprodutibilidade dos Testes , Rifampina/farmacologia , Sensibilidade e Especificidade , Estreptomicina/farmacologiaRESUMO
Pathozyme-Myco G (Myco G), M, A, and TB complex plus (Omega Diagnostics Ltd., Alloa, Scotland) were evaluated for the serological diagnosis of pulmonary tuberculosis (TB) in an Argentinean population. Sera from 58 patients with pulmonary TB, 24 subjects with pulmonary mycobacteriosis or mycoses (pulmonary MM group), and 45 subjects with other underlying disorders (control group) were analyzed. The sensitivities of the tests ranged from 29% (Myco M) to 82% (Myco G) in smear-positive patients (17 subjects) and from 29% (TB complex plus) to 49% (Myco G) in smear-negative patients (41 subjects). The specificities of the assays varied from 93% (Myco M) to 100% (Myco G and TB complex plus) in controls and from 62% (Myco A) to 96% (TB complex plus) in the pulmonary MM group. Overall, for the diagnosis of smear-negative patients, Myco G had the best characteristics, with a sensitivity of 49% and specificities of 100% for controls and 75% for the pulmonary MM group; after its combination with TB complex plus, its sensitivity improved to 59%. Nevertheless, despite its relatively poor capacity to discriminate between pulmonary TB and pulmonary MM, Myco G, alone or in combination with TB complex plus, would be a useful diagnostic tool for patients with suspected pulmonary TB living in areas where the relative prevalence of pulmonary MM was low.
Assuntos
Ensaio de Imunoadsorção Enzimática/métodos , Mycobacterium/isolamento & purificação , Tuberculose Pulmonar/diagnóstico , Argentina/epidemiologia , Humanos , Hanseníase/diagnóstico , Hanseníase/epidemiologia , Kit de Reagentes para Diagnóstico , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Manejo de Espécimes/métodos , Tuberculose Pulmonar/epidemiologiaRESUMO
El diagnóstico de certeza de tuberculosis infantil es complicado debido a las formas clínicas de presentación de la enfermedad, generalmente paucibacilares. Este estudio colaborativo nacional se realizó con el objetivo de conocer las características de la tuberculosis infantil en el momento del diagnóstico, las pautas diagnósticas en las que los pediatras se basan, el aporte de la bacteriología y la calidad de las notificaciones. Se revisaron las historias clínicas y los registros de laboratorios de pacientes menores de 15 años enfermos de tuberculosis o con primoinfecciones inaparentes diagnosticados durante 1995 en servicios de salud del interior del país en los que los pediatras aceptaron participar. Se estudiaron 400 casos (17 por ciento de las notificaciones al Programa Nacional en este grupo etáreo) y 81 primoinfecciones. Las proporciones de niños enfermos investigados mediante radiologia de tórax, sintomatología, prueba tuberculínica, estudio de contractos y bacteriología fueron del 95.3 por ciento, 79.6 por ciento, 90.1 por ciento, 92.7 por ciento y 35 por ciento respectivamente para los casos pulmonares y del 87.7 por ciento, 100 por ciento, 87.7 por ciento, 85.9 por ciento y 78.9 por ciento, respectivamente para los extrapulmonares. De los casos pulmonares investigados el 99.1 por ciento presentaban radiología anormal, 79.0 por ciento prueba tuberculínica ü 10 mm, 79.8 por ciento fueron sintomáticos y en 80.2 por ciento fue identificado un contacto. Todos los niños con lesiones extrapulmonares fueron sintomáticos; 63 por ciento presentaban concomitantemente anomalias pulmonares. Se confirmó bacteriológicamente el diagnóstico del 10.7 por ciento de los casos (20.8 por ciento de los pulmonares y 40.0 por ciento de los extrapulmonares investigados). El estudio indicaría que el diagnóstico se realiza en etapas relativamente tempranas de la enfermedad. En general se siguen las normas de la Sociedad Argentina de Pediatría. La confirmación bacteriológica resultó baja, lo que podría ser atribuido a la escasa investigación bacteriológica y al bajo rendimiento del cultivo de muestras pulmonares. El estudio evidenció subregistro de casos e imprecisión en la información al Programa Naiconal.
Assuntos
Humanos , Recém-Nascido , Lactente , Pré-Escolar , Criança , Adolescente , Tuberculose Pulmonar/diagnóstico , Argentina/epidemiologia , Notificação de Doenças , Lavagem Gástrica , Escarro/microbiologia , Tuberculose Pulmonar/epidemiologia , Tuberculose Pulmonar/microbiologiaRESUMO
Para conocer los agentes etiológicos de las infecciones respiratorias agudas (IRA) del tracto inferior y la portación de bacterias en aspirados nasofaríngeos (ANF), en niños menores de 5 años, se realizó un estudio en la ciudad de Santa Fe durante 1993, 1994 y 1995. Se incluyeron 450 enfermos y 68 controles sin IRA y se tomaron muestras de sangre, líquido pleural y ANF para cultivo bacteriano. En los ANF se realizaron técnicas de inmunofluorescencia para virus, y se empleó suero para detección de IgM anti Chlamydia trachomatis. El 6,2 por ciento (14/224) de los hemocultivos resultaron positivos. Se aislaron 11 cepas de Streptococcus pneumoniae (cinco resistentes a oxacilina), dos de Haemophilus influenzae y una de Staphylococcus aureus. El virus sincicial respiratorio fue el agente etiológico del 23,3 por ciento (105/450) de las IRA. El 24 por ciento de los niños con factores de riesgo para Chlamydia trachomatis tuvieron altos títulos de IgM específica. Las dos bacterias más aisladas de ANF de niños con IRA fueron H. influenzae (31,6 por ciento) y S. pneumoniae (23,4 por ciento) y, de los controles, estreptococos grupo viridans (26,5 por ciento), H. influenzae (23,5 por ciento) y Moraxella catarrhalis (22,1 por ciento). Los tipos de S. pneumoniae que prevalecieron fueron 14 y 7. El tipo de H. influenzae predominante fue b biotipo I. Durante el período del estudio, la sensibilidad de los neumococos a oxacilina disminuyó desde 60 por ciento hasta 50,8 por ciento y la de H. influenzae a ampicilina bajó desde 92,3 por ciento hasta 79 por ciento. Todas las cepas de H. influenzae tipo b fueron sensibles a ampicilina.