RESUMO
Ready to use dry-reagent PCR assays for Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas spp. and for broad-range bacteria detection were developed. The assays were based on novel switchable lanthanide probes that provide sensitive target DNA detection with exceptionally high signal-to-background ratio, thus enabling clear discrimination between positive and negative results. For example, sensitivity of three S. aureus and two S. pneumonia bacteria (colony forming units) per PCR assay was measured with fluorescence signal more than 30 times over the background signal level. The rapid and easy-to-use assays are suitable for routine clinical diagnostics without molecular biology expertise and facilities.
Assuntos
Infecções Bacterianas/diagnóstico , Técnicas Bacteriológicas/métodos , Elementos da Série dos Lantanídeos/metabolismo , Medições Luminescentes , Técnicas de Diagnóstico Molecular/métodos , Sondas de Oligonucleotídeos/genética , Reação em Cadeia da Polimerase/métodos , Escherichia coli/genética , Escherichia coli/isolamento & purificação , Humanos , Pseudomonas/genética , Pseudomonas/isolamento & purificação , Sensibilidade e Especificidade , Staphylococcus aureus/genética , Staphylococcus aureus/isolamento & purificação , Streptococcus pneumoniae/genética , Streptococcus pneumoniae/isolamento & purificaçãoRESUMO
A method for the rapid detection of methicillin-sensitive and -resistant Staphylococcus aureus (MSSA and MRSA, respectively) and methicillin-resistant coagulase-negative staphylococci (MRCoNS) with a straightforward sample preparation protocol of blood cultures using an automated homogeneous polymerase chain reaction (PCR) assay, the GenomEra™ MRSA/SA (Abacus Diagnostica Oy, Turku, Finland), is presented. In total, 316 BacT/Alert (bioMérieux, Marcy l'Etoile, France) and 433 BACTEC (Becton Dickinson, Sparks, MD, USA) blood culture bottles were analyzed, including 725 positive cultures containing Gram-positive cocci in clusters (n = 419) and other Gram stain forms (n = 361), as well as 24 signal- and growth-negative bottles. Detection sensitivities for MSSA, MRSA, and MRCoNS were 99.4 % (158/159), 100.0 % (9/9), and 99.3 % (132/133), respectively. One false-positive MRSA result was detected from a non-staphylococci-containing bottle, yielding a specificity of 99.8 %. The lowest detectable amount of viable cells in the blood culture sample was 4 × 10(4) CFU/mL. The results were available within one hour after microbial growth detection and the two-step, time-resolved fluorometric (TRF) measurement mode employed by the GenomEra CDX™ instrument showed no interference from blood, charcoal, or culture media. The method described lacks all sample purification steps and allows reliable and simplified pathogen detection also in clinical microbiology laboratory settings without specialized molecular microbiology competence.
