Application of fnbA gene as new target for the species-specific and quantitative detection of Staphylococcus aureus directly from lower respiratory tract specimens by real time PCR.

Staphylococcus aureus is a significant cause of hospital-acquired pneumonia (HAP), particularly in mechanically ventilated patients. We used the fibronectin-binding protein A gene (fnbA) for the species-specific and quantitative detection of S. aureus directly from lower respiratory tract (LRT) specimens by a Taq Man real time PCR. For this reason, a total of 269 lower respiratory tract (LRT) specimens collected from patients with hospital-acquired pneumonia were assayed. Amplification of fnbA in serial dilutions ranged from 10 9 CFU/ ml to 10 2 CFU/ml. Standard curve of triplicate every dilution had slope 3.34 ± 0.1 and R 2 > 0.99 with SD 0.1. Based on these data, the sensitivity and specificity of the newly developed real time PCR targeting the fnbA gene were both 100%. The Cohen's Kappa test showed the Kappa value of 1.0. The fnbA gene is a potential marker for the species-specific detection of S. aureus and can be used to detect this bacterium in any clinical specimens by real time PCR. Moreover, this method reduces the time needed for quantitative detection of Staphylococcus aureus from LRT specimens to nearly 2 hours compared to 1 to 4 days for culture and provided sensitivity equal to or greater than culture.

CD4+ cell counts in patients with different clinical manifestations of tuberculosis

Tuberculosis is the prototype of infections that require a cellular immune response for their control. It has been shown that CD4+ T-lymphocytes are most important in the protective response against Mycobacterium tuberculosis. CD8+ T-lymphocytes are also important for effective T-cell immune response. This study compares CD4+ and CD8+ baseline values in patients with different manifestations of tuberculosis. CD4+ and CD8+ in three groups of patients with tuberculosis (pulmonary, lymphadenitis, meningitis/milliary involvement) and a group of healthy volunteers were enumerated using flowcytometry. Twenty-six patients with pulmonary tuberculosis, 10 with adenitis, 16 with meningitis or milliary tuberculosis and 16 healthy volunteers entered the study. Mean CD4 in meningitis/milliary group was significantly lower than all other groups (p<0.05). Mean CD4 counts of patients with pulmonary tuberculosis was also significantly lower than control group (p=0.01). Mean CD8 in meningitis/milliary group was significantly lower than control group (p=0.02). No relation was found between results of TSTs and CD4 values in three groups. CD4 depletion is an expectable phenomenon in patients with tuberculosis. This study shows that patients with more severe form of disease had the lowest number of both CD4 and CD8 cells which can be a sign of suppressed cellular immunity in these patients.