Sonication is superior to scraping for retrieval of bacteria in biofilm on titanium and steel surfaces in vitro

Background and purpose Low-virulence implant infections are characterized by bacterial colonization of the implant with subsequent biofilm formation. In these cases, soft tissue biopsies often prove to be culture negative. Consequently, detachment of the causative adherent bacteria is crucial for correct microbiological diagnosis. Using an in vitro model, we compared 4 methods of biofilm sampling from metal surfaces

Engineering an aldehyde dehydrogenase toward its substrates, 3-hydroxypropanal and NAD(+), for enhancing the production of 3-hydroxypropionic acid

3-Hydroxypropionic acid (3-HP) can be produced via the biological route involving two enzymatic reactions: dehydration of glycerol to 3-hydroxypropanal (3-HPA) and then oxidation to 3-HP. However, commercial production of 3-HP using recombinant microorganisms has been hampered with several problems, some of which are associated with the toxicity of 3-HPA and the efficiency of NAD(+) regeneration. We engineered a-ketoglutaric semialdehyde dehydrogenase (KGSADH) from Azospirillum brasilense for the second reaction to address these issues. The residues in the binding sites for the substrates, 3-HPA and NAD(+), were randomized, and the resulting libraries were screened for higher activity. Isolated KGSADH variants had significantly lower Km values for both the substrates. The enzymes also showed higher substrate specificities for aldehyde and NAD(+), less inhibition by NADH, and greater resistance to inactivation by 3-HPA than the wild-type enzyme. A recombinant Pseudomonas denitrificans strain with one of the engineered KGSADH variants exhibited less accumulation of 3-HPA, decreased levels of inactivation of the enzymes, and higher cell growth than that with the wild-type KGSADH. The flask culture of the P. denitrificans strain with the mutant KGSADH resulted in about 40% increase of 3-HP titer (53 mM) compared with that using the wild-type enzyme (37 mM)

Treatment of long-term intravascular catheter-related bacteraemia with antibiotic lock: randomized, placebo-controlled trial

Objectives: The use of an antibiotic lock (AB-lock) for the treatment of catheter-related bloodstream infection (CRBSI) has been suggested, but randomized trials have never been performed. Methods: A randomized, blinded, multicentre trial was set up to compare an AB-lock—containing van-comycin for Gram-positive or ceftazidime for Gram-negative bacteria—with placebo, in addition to par-enteral AB therapy. We included only CRBSI from a long-term intravascular device (LTID) whether tunnelled or totally implanted. Results: During 30 months, 174 patients with an LTID and bacteraemia were evaluated, of whom 85 had a CRBSI. Forty-six patients were included. Frequent reasons for exclusion were: catheter not vacant for>8–12 h/day for the AB-lock (n 5 10); yeast infection or mixed Gram-positive/negative infections (n 5 13); catheter removal preferred by the treating physician (n 5 7); and CRBSI <14 days after inser-tion or pocket/tunnel infection (n 5 10). Forty-four patients met the criteria for modified intention-to-treat analysis. The primary endpoint was failure to cure the CRBSI or relapse with the same strain. On study day 180 by Kaplan–Meier analysis, this occurred in 33 % (seven of 21) in the AB-lock arm and in 57 % (13 of 23) in the placebo arm (hazard ratio 0.55, P 5 0.10). A relapse with the same strain occurred in 9/23 with the placebo and 3/21 with the AB-lock (P 5 0.06). Conclusion: Future studies should take into account the barriers to the use of AB-lock observed in this study. Most importantly, shorter lock dwell times and broader spectrum locks (e.g. antiseptic) should be investigated to target a larger patient population