ABSTRACT
Comparison of the use of indirect immunofluorescence assay (IFA), immunochromatography assay (ICA-BD) and reverse transcription-polymerase chain reaction (RT-PCR) for detecting human respiratory syncytial virus (HRSV) in 306 nasopharyngeal aspirates samples (NPA) was performed in order to assess their analytical performance. By comparing the results obtained using ICA-BD with those using IFA, we found relative indices of 85.0 percent for sensitivity and 91.2 percent for specificity, and the positive (PPV) and negative (NPV) predictive values were 85.0 percent and 91.2 percent, respectively. The relative indices for sensitivity and specificity as well as the PPV and NPV for RT-PCR were 98.0 percent, 89.0 percent, 84.0 percent and 99.0 percent, respectively, when compared to the results of IFA. In addition, comparison of the results of ICA-BD and those of RT-PCR yielded relative indices of 79.5 percent for sensitivity and 95.4 percent for specificity, as well as PPV and NPV of 92.9 percent and 86.0 percent, respectively. Although RT-PCR has shown the best performance, the substantial agreement between the ICA-BD and IFA results suggests that ICA-BD, also in addition to being a rapid and facile assay, could be suitable as an alternative diagnostic screening for HRSV infection in children.
Subject(s)
Child, Preschool , Humans , Chromatography , Fluorescent Antibody Technique, Indirect , Respiratory Syncytial Virus, Human , Reverse Transcriptase Polymerase Chain Reaction , Respiratory Syncytial Virus Infections/diagnosis , Acute Disease , Chromatography/methods , Nasal Lavage Fluid/virology , Nasopharynx/virology , Predictive Value of Tests , RNA, Viral/genetics , Respiratory Syncytial Virus, Human/genetics , Respiratory Syncytial Virus, Human/immunology , Sensitivity and SpecificityABSTRACT
Staphylococcus aureus is a pathogen that has been associated with nosocomial infections since the preantibiotic era. Since the introduction of antibiotics in medical practice in the 1940 s, methicillin-resistant S. aureus (MRSA) strains have been emerging in various parts of the world. In view of the important role of the phagocytic system in the defense against this bacteria, we decided to study phagocytosis by neutrophils and monocytes of an epidemic MRSA strain in São Paulo, Brazil, in comparison with methicillin-sensitive strains. Complement system opsonins are fundamental for efficient ingestion of the resistant and sensitive strains by both types of phagocytes. We found no association of the opsonic requirement of the MRSA strain with the multiresistance phenotype. On the other hand, the MRSA strain was found to be more resistant to the effector mechanisms of neutrophils than both sensitive strains when opsonized with fresh serum, despite the phagocytosis results. This fact suggests that the intracellular killing of S. aureus is an additional parameter of bacterial virulence, but new approaches must be implemented to study the interactions of this MRSA strain with phagocytes in order to investigate the possible factors involved in its behavior in response to neutrophil effector mechanisms.
Subject(s)
Humans , Male , Adolescent , Adult , Middle Aged , Methicillin Resistance , Monocytes , Neutrophils , Phagocytosis , Staphylococcus aureus , Immunoglobulins , Opsonin Proteins , Protein C , Staphylococcus aureusABSTRACT
There is some controversy concerning the effect of intravenous long-chain triglyceride (LCT) emulsions on the phagocytic system and little is known about the effect of medium-chain triglyceride (MCT) containing emulsions. We evaluated the chemotaxis and random migration of human neutrophils from 18 healthy adult after preincubation with the following fat emulsions: LCT, MCT and a mixture of 50% MCT and 50% LCT (MCT/LCT). Leukocyte-rich plasma (4 x 10 6 cells/ml) was diluted 4:1 (v/v) with commercial fat emulsions (LTC, MCT, or MCT?LCT, 1:1) or saline and tumbled at 20 cycles?min for 30 min at 37 grade C. The final composition or the emulsion was 20 mg/ml fat, 0.24% egg yolk lecithin, and 0.5% glycerol and the dispersion was made isotonic by adding NaCl. In a second set of experiments, the LCT and MCT concentrations were adjusted to be equimolar. Leukocyte viability was * 95% after exposure to the treatment with fat emulsions. For emulsions with the same weight of each fat, random migration and chemotaxis of neutrophils were unaffected by the LCT emulsion but there was a significant decrease in both chemotaxis and random migration in MCT- (79 and 74%) or MCT/LCT-treated (60 and 56%) neutrophils. Similar results were obtained when LCT and MCT were equimolar. These results demonstrate an inhibitory effect of MCT on two human neutrophil functions which may be dose dependent