Exposure to One Antibiotic Leads to Acquisition of Resistance to Another Antibiotic via Quorum Sensing Mechanisms.

The vancomycin-resistant Enterococci (VRE) have progressively become a severe medical problem. Although clinics have started to reduce vancomycin prescription, vancomycin resistance has not been contained. We found that the transfer of vancomycin resistance in Enterococcus faecalis increased more than 30-fold upon treatment by streptomycin. Notably, treatment with an antibiotic caused the bacteria to become resistant to another. The response was even stronger in the well-studied plasmid pCF10 and the number of transconjugants increased about 100,000-fold. We tested four different antibiotics, and all of them induced conjugal response. Through a mathematical model based on gene regulation, we found a plausible explanation. Via quorum sensing, the change of the cell density triggers the conjugation. Moreover, we searched for generality and found a similar strategy in Bacillus subtilis. The outcome of the present study suggests that even common antibiotics must not be overused.

Dynamic evolution of D-dimer level in cerebrospinal fluid predicts poor outcome in patients with spontaneous intracerebral hemorrhage combined with intraventricular hemorrhage.

The risk of mortality in patients with intracerebral hemorrhage (ICH) significantly increases when complicated by intraventricular hemorrhage (IVH). We hypothesize that serial measurement of cerebrospinal fluid (CSF) D-dimer levels in patients with both ICH and IVH may serve as an early marker of IVH severity. We performed a prospective study of 43 consecutive ICH patients combined with IVH and external ventricular drainage placement admitted in our institution from 2005-2006. IVH severity (Graeb score) and fibrinolytic activity were evaluated continuously for 7days using CT scans and CSF D-dimer levels. The primary outcome was 30day mortality. Overall 30day mortality was 26% (n=11), with eight deaths (72.7%) after 3days (D3). Graeb score and CSF D-dimer on admission (D0) were not significantly different between survivors and non-survivors. The temporal profiles of both parameters were distinctly different, with a downward trend in survivors and an upward trend in non-survivors. A mortality rate of 54% was observed between D0-D3 when both scores increased during this interval. In contrast, the mortality was only 4% when both measures decreased during this interval. Early phase (D0-D3) CSF D-dimer or Graeb score change demonstrated high sensitivity of 88% and specificity of 81% when predicting 30day mortality. Early phase CSF D-dimer change in patients with both ICH and IVH is accurate in predicting mortality and may be utilized as a cost-effective surrogate indicator of IVH severity. Serial monitoring of CSF D-dimer dynamic changes is useful for early identification of patients with hematoma progression and poor outcome.