Biofilm formation in erythromycin-resistant Staphylococcus aureus and the relationship with antimicrobial susceptibility and molecular characteristics.

PURPOSE: In this study, we aimed to investigate biofilm formation characteristics in clinical Staphylococcus aureus (S. aureus) isolates with erythromycin (ERY) resistance from China and further analyze their correlations with antimicrobial susceptibility and molecular characteristics. METHODOLOGY: A total of 276 clinical isolates of ERY-resistant S. aureus, including 142 methicillin-resistant S. aureus (MRSA) strains and 134 methicillin-susceptible S. aureus (MSSA) strains, were retrospectively collected in China. Biofilms were determined by crystal violet staining and ERY resistance genes (ermA, ermB and ermC) were detected by polymerase chain reaction. Inducible clindamycin resistance was examined by D test and multilocus sequence typing, and clonal complexes (CCs) based on housekeeping genes were further determined. RESULTS: The frequency of biofilm formation among ERY-resistant S. aureus was 40.9% (113/276) in total and no significant difference was found for the frequency of biofilm formation between ERY-resistant MRSA and ERY-resistant MSSA (44.4% vs 37.3%, P > 0.05). In ERY-resistant MRSA isolates, the frequency of biofilm formation in ermA-positive, gentamicin-resistant and ciprofloxacin-resistant isolates was higher than that in ermA-negative, gentamicin-sensitive and ciprofloxacin-sensitive isolates, respectively (63.9% vs 23.6%, P < 0.01; 60.3% vs 27.5%, P < 0.01; 65.2% vs 26.3%, P < 0.01). In addition, tetracycline resistance facilitated biofilm formation in both ERY-resistant MRSA and MSSA and the frequency of biofilm formation in CC239- or CC7S. aureus isolates with ERY resistance was significantly higher compared with that in CC59S. aureus (both P < 0.01). CONCLUSION: The ermA gene, and gentamicin, ciprofloxacin and tetracycline resistance facilitate biofilm formation in ERY-resistant MRSA isolates and, moreover, ERY-resistant S. aureus isolates with positive biofilm formation exhibited clonality clustering regarding CC239 and CC7.

[Characteristics of CDR3 of TCR beta on CD8+ T cells in chronic hepatitis B patients].

OBJECTIVE: To analyze the characteristics of CDR3 of TCRbeta on CD8+ T cells in chronic hepatitis B patients. METHODS: Eight patients with chronic hepatitis B (ALT more than 2 ULN) were enrolled in this study. CD8+ T cells were isolated from peripheral blood. RT-PCR was proformed to amplify the CDR3 of TCRbeta, and the PCR products were sequenced and analyzed. RESULTS: The chronic hepatitis B patients showed obvious clonal expansion of T cell, and three perturbation patterns of T cell expansion were showed in the CDR3 of TCRbeta, including monoclonicity, oligoclonicity and skewed peak patterns. The number of perturbation families of CD8+ subpopulation was significantly higher than that of CD8- subpopulation (10.6+/-4.7 vs. 4.1+/-3.1, t = 6.619, P less than 0.01). In 3 out of 8 patients, the number of perturbation families of CD8+ subpopulation was also higher than that of PBMCs without depleting CD8+ subpopulation. CONCLUSIONS: The characteristics of CDR3 of TCRbeta may help to understand the inflammatory response in CHB patients.