Identificação de micro-organismos presentes em hemoculturas de pacientes de unidades de terapia intensiva e avaliação dos Staphylococcus coagulase-negativa
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Data
2016-10-27
Autores
Monteiro, Aydir Cecília Marinho [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A rápida e precisa identificação de micro-organismos causadores de infecções da corrente sanguínea é uma das funções mais importantes do laboratório de microbiologia clínica. Com o objetivo de diminuir o tempo gasto para se identificar esses micro-organismos, vários equipamentos foram desenvolvidos, entre eles o sistema VITEK® 2, usado na rotina de diversos laboratórios de microbiologia clínica para a identificação de isolados de amostras clínicas. Inúmeros micro-organismos são isolados de hemoculturas e as bactérias pertencentes ao grupo dos cocos Gram-positivos aeróbios são os principais agentes etiológicos das infecções de correntes sanguíneas, principalmente em pacientes mantidos em unidades de terapia intensiva (UTIs). Este trabalho comparou sistemas de identificação de espécies de micro-organismos isolados a partir de hemoculturas e acompanhou os pacientes com hemoculturas positivas para Estafilococos coagulase-negativa (ECN). A partir dessas hemoculturas positivas coletadas de 216 pacientes foram isolados e identificados 400 microorganismos, dentre eles 5 bacilos Gram-positivos, 15 leveduras, 165 bacilos Gram-negativos e 215 cocos Gram-positivos. Essa identificação foi realizada pelo sistema VITEK® 2 e os resultados foram comparados com os obtidos em provas fenotípicas convencionais e nos métodos genotípicos. Os pacientes com hemoculturas positivas para ECN foram acompanhados durante sua permanência no hospital com a coleta de seus dados clínicos dos prontuários. O sistema automatizado VITEK® 2 identificou corretamente 94,7% das amostras, os cartões YST e GN apresentaram 100% de identificações corretas das leveduras e dos bacilos Gram-negativos, respectivamente, ao passo que o GP identificou corretamente 92,6% dos cocos Gram-positivos. A sensibilidade apresentada pelo sistema VITEK® 2 e a análise estatística permitem concluir que esse equipamento é uma opção viável na rotina de laboratórios de microbiologia clínica para a identificação de micro-organismos. A análise multivariada para o desfecho óbito no estudo de coorte dos pacientes que apresentaram hemocultura positiva para ECN revelou associações positivas com AIDS e com hemocultura positiva para S. hominis, enquanto o uso de meropenem mostrou associação negativa. Na análise do desfecho múltiplas hemoculturas positivas para ECN, foi verificada associação positiva com pacientes em choque que necessitavam de droga vasoativa. Isso sugere que a gravidade da sepse (choque) é um preditor da significância clínica de ECN com o isolamento em mais de uma hemocultura, um dos critérios mais utilizados para valorização clínica desses micro-organismos quando isolados da corrente sanguínea. A análise da curva de sobrevida dos pacientes incluídos na coorte revelou que pacientes com hemocultura positiva para a espécie S. hominis apresentaram menor sobrevida quando comparados com pacientes com hemoculturas para outras espécies de ECN, indicando a importância dessa espécie na gravidade das infecções da corrente sanguínea.
The rapid and accurate identification of microorganisms which cause bloodstream infections is one of the major roles of the clinical microbiology laboratory. Aiming at reducing the time spent in identifying such microorganisms, several devices have been developed, including the VITEK® 2 system, which is routinely used in a number of clinical microbiology laboratories for identifying isolates from clinical specimens. A lot of microorganisms are isolated from blood cultures; bacteria belonging to the group of aerobic Gram-positive cocci are the main etiological agents of bloodstream infections, especially in patients kept in intensive care units (ICUs). The objectives of this study were to compare the performance of (manual and automated) species identification systems for microorganisms isolated from blood cultures by evaluating the performance of VITEK® 2 system and also to conduct a cohort study of patients who had blood cultures positive for Coagulase-negative staphylococci (CoNS) in order to address two outcomes: isolation of CoNS in more than one blood culture as opposed to a single blood culture and the factors associated with patient prognosis. Four hundred microorganisms isolated from blood cultures were identified: 5 Gram-positive bacilli, 15 yeasts, 165 Gram-negative bacilli, and 215 Gram-positive cocci. This identification was carried out by the VITEK® 2 system and the results were compared with those obtained from conventional phenotypic tests and genotypic methods. Patients with blood cultures positive for CoNS were followed during their stay in hospital with collecting the clinical data from their medical records. The automated VITEK® 2 system accurately identified 94.7% of the specimens. The YST and GN ID cards had 100% accurate identifications of the yeasts and the Gram-negative bacilli respectively, whereas the GP ID card accurately identified 92.6% of the Gram-positive cocci. The susceptibility of the VITEK® 2 system and the statistical analysis allow the conclusion that this instrument is a viable option in the routine of clinical microbiology laboratories for microorganism identification. The multivariate analysis for death as the outcome in the cohort study of patients with CoNS positive blood culture revealed positive associations with AIDS and with blood culture positive for S. hominis, while the use of meropenem showed a negative association. In analyzing the outcome of multiple blood cultures positive for CoNS, a positive association was observed in patients with shock (requiring vasoactive drugs). It suggests that the sepsis (shock) severity is a predictor of CoNS clinical significance with the isolation in more than one blood culture, which is one of the most commonly used criteria for clinical recovery of the microorganisms when isolated from the bloodstream. The analysis of the survival curve of patients included in the cohort revealed that patients with blood cultures positive for S. hominis species showed lower survival compared to patients with blood cultures for other species of CoNS, which indicates the importance of this species in the severity of bloodstream infections.
The rapid and accurate identification of microorganisms which cause bloodstream infections is one of the major roles of the clinical microbiology laboratory. Aiming at reducing the time spent in identifying such microorganisms, several devices have been developed, including the VITEK® 2 system, which is routinely used in a number of clinical microbiology laboratories for identifying isolates from clinical specimens. A lot of microorganisms are isolated from blood cultures; bacteria belonging to the group of aerobic Gram-positive cocci are the main etiological agents of bloodstream infections, especially in patients kept in intensive care units (ICUs). The objectives of this study were to compare the performance of (manual and automated) species identification systems for microorganisms isolated from blood cultures by evaluating the performance of VITEK® 2 system and also to conduct a cohort study of patients who had blood cultures positive for Coagulase-negative staphylococci (CoNS) in order to address two outcomes: isolation of CoNS in more than one blood culture as opposed to a single blood culture and the factors associated with patient prognosis. Four hundred microorganisms isolated from blood cultures were identified: 5 Gram-positive bacilli, 15 yeasts, 165 Gram-negative bacilli, and 215 Gram-positive cocci. This identification was carried out by the VITEK® 2 system and the results were compared with those obtained from conventional phenotypic tests and genotypic methods. Patients with blood cultures positive for CoNS were followed during their stay in hospital with collecting the clinical data from their medical records. The automated VITEK® 2 system accurately identified 94.7% of the specimens. The YST and GN ID cards had 100% accurate identifications of the yeasts and the Gram-negative bacilli respectively, whereas the GP ID card accurately identified 92.6% of the Gram-positive cocci. The susceptibility of the VITEK® 2 system and the statistical analysis allow the conclusion that this instrument is a viable option in the routine of clinical microbiology laboratories for microorganism identification. The multivariate analysis for death as the outcome in the cohort study of patients with CoNS positive blood culture revealed positive associations with AIDS and with blood culture positive for S. hominis, while the use of meropenem showed a negative association. In analyzing the outcome of multiple blood cultures positive for CoNS, a positive association was observed in patients with shock (requiring vasoactive drugs). It suggests that the sepsis (shock) severity is a predictor of CoNS clinical significance with the isolation in more than one blood culture, which is one of the most commonly used criteria for clinical recovery of the microorganisms when isolated from the bloodstream. The analysis of the survival curve of patients included in the cohort revealed that patients with blood cultures positive for S. hominis species showed lower survival compared to patients with blood cultures for other species of CoNS, which indicates the importance of this species in the severity of bloodstream infections.
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Palavras-chave
Hemocultura, Staphylococcus coagulase-negativa, Vitek 2® System, Identificação, Comparação