Aplicação de métodos moleculares no diagnóstico de endoftalmite bacteriana

• Autor(a) principal: Bispo, Paulo José Martins [UNIFESP]
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UNIFESP
• Texto Completo: https://repositorio.unifesp.br/handle/11600/8956
• topic: Endoftalmite bacteriana; Infecções intra-oculares; Multiplex PCR; Nested PCR; PCR em Tempo Real

Objective: Development and application of Nested Multiplex PCR and Real Time PCR assays for detection and Gram classification of bacteria using aqueous and vitreous humor collected from patients with suspected endophthalmitis. Methods: Analytical specificity was established using 31 clinically important pathogens, 20 gram-positive and 11 gram-negative. Specificity was also tested using human DNA and fungal DNA. Control samples of non-infected aqueous humor collected at the end of phacoemulsification surgery were included. Analytical sensitivity was determined using a 10-fold dilution of S. epidermidis and E. coli DNA. After, methodologies were tested in aqueous and vitreous humor collected from patients with clinical diagnosis of endophthalmitis. Comercial Taq polymersase preparations were DNA decontaminated using DNaseI pretreatment. Results: Universal amplification of 16S rDNA was achieved for all bacterial isolated. Nested Multiplex PCR failed only to determine the Gram status of Acinetobacter spp. Gram classification was achieved for every bacterial isolates using a Multiplex Gram-Specific TaqMan-based PCR, and only a P. acnes isolate showed a mixed signal. Limit of detection using Nested Multiplex PCR was 1 fg/μl for both S. epidermidis and E. coli. Sensitivity for detection of S. epidermidis and E. coli DNA using a SYBR Green 16S rDNA-based universal PCR was 100 fg/μl (E = 0.82 and 0.86; r2 = 0.99) and 1 pg/μl using a Multiplex Gram-Specific TaqMan-based PCR (E = 0.66 and 0.77; r2 = 0.99). Culture was positive in 47.6% of aqueous and vitreous humor analysis. Nested Multiplex PCR and Real Time PCR assays were positive in 100% and 95.2% of these cases, respectively. Among negative culture samples, Nested Multiplex PCR was positive for all (100%) and Real Time PCR assays in 90% of cases (9/10). Gram classification was completed for 88.8% and 100% samples using Nested Multiplex PCR and Real Time PCR methodologies, respectively. Correlation of 63.6% between microbiological and molecular Gram classification was observed using both molecular assays. 16S rDNA sequence-based identification using Nested Multiplex PCR and Real Time PCR products showed 100% and 88.8% correlation respectively when compared with phenotypic identification. Conclusions: Both PCR methodologies presented good correlation when compared with culture-proven results and bacterial detection was improved from 47.6%% to 100% showing to be feasible tests for laboratorial characterization of bacterial endophthalmitis.