Biochemical Characterization of Cardiolipin Synthase Mutations Associated with Daptomycin Resistance in Enterococci

Daptomycin (DAP) resistance in enterococci has been linked to mutations in genes that alter the cell envelope stress response (CESR) (liaFSR) and changes in enzymes that directly affect phospholipid homeostasis, and these changes may alter membrane composition, such as that of cardiolipin synthase (Cls). While Cls substitutions are observed in response to DAP therapy, the effect of these mutations on Cls activity remains obscure. We have expressed, purified, and characterized Cls enzymes from both Enterococcus faecium S447 (residues 52 to 482; Cls447a) and Enterococcus faecalis S613 (residues 53 to 483; Cls613a) as well as Cls variants harboring a single-amino-acid change derived from DAP-resistant isolates of E. faecium. E. faecium Cls447a and E. faecalis Cls613a are tightly associated with the membrane and copurify with their substrate, phosphatidylglycerol (PG), and product, cardiolipin (CL). The amount of PG that copurifies with Cls is in molar excess to protein, suggesting that the enzyme localizes to PG-rich membrane regions. Both Cls447a^H215R and Cls447a^R218Q showed an increase in V_max (μM CL/min/μM protein) from 0.16 ± 0.01 to 0.26 ± 0.02 and 0.26 ± 0.04, respectively, indicating that mutations associated with adaptation to DAP increase Cls activity. Modeling of Cls447a to Streptomyces sp. phospholipase D indicates that the adaptive mutations Cls447a^H215R and Cls447a^R218Q are proximal to the phospholipase domain 1 (PLD1) active site and near the putative nucleophile H217. As mutations to Cls are part of a larger genomic adaptation process, increased Cls activity is likely to be highly epistatic with other changes to facilitate DAP resistance.     

Ciprofloxacin versus ceftriaxone in the treatment of multiresistant typhoid fever

A randomized trial comparing ceftriaxone (3 g given parenterally per day for 7 days) to ciprofloxacin (500 mg given orally twice a day for 7 days) in the treatment of blood culture positive typhoid fever was conducted. Twenty patients were openly randomized to receive ciprofloxacin and 22 to receive ceftriaxone. The outcome was classified as clinical failure in 6 patients (27 %) in the ceftriaxone group, but in none in the ciprofloxacin group (p=0.01). The mean duration of fever was four days in the ciprofloxacin group and about five days in the ceftriaxone group (p=0.04). In the six patients in the ceftriaxone group who experienced failure, therapy was switched to ciprofloxacin and the patients became afebrile and asymptomatic within 48 hours. Patients with resistant strains ofSalmonella typhi and patients with sensitive strains responded equally well to ciprofloxacin therapy. Analysis of a subset of 12 of the multiresistant strains revealed that resistance was encoded for by a transferable 180 kilobase plasmid. Ciprofloxacin represents a useful treatment option in areas where multiresistant strains are likely to be encountered.     

新式口腔激光应用

自20世纪90年代初起，超短激光脉冲（ultra-short laser pulses，USLP）就已成为医学诊断和组织处理领域研究的重点，大量关于等离子体介导消融（plasma—mediated ablation）机制，生物软硬组织激光消融及其对周围健康组织的影响等方面的研究成果已公开发表，在这些研究中，主要是关于US-LP在牙科中的应用。     

Toxic effect of concomitant administration of cyclosporin A and acyclovir on renal function and morphology in rats

The immunosuppressive agent cyclosporin A (CyA) and the antiviral drug acyclovir may cause renal functional impairment. CyA-induced immunosuppression increases the rate of viral infections. Therefore we were interested to determine whether short-term co-administration of CyA and acyclovir involves an increased nephrotoxic risk. Male Wistar rats were treated with CyA (20 mg/kg body wt., s.c., once daily for 8 days), acyclovir (15 mg/kg body wt., s.c., 3-times daily for the last 5 days) or a combination of CyA and acyclovir. Blood levels of CyA were determined after a single dose. Urine was monitored for volume, osmolality, total protein and N-acetyl-β-d-glucosaminidase (β-NAG). Concentrations of blood urea nitrogen (BUN) and plasma-creatinine were determined (day 9). Renal cortical slices were monitored for accumulation of weak organic acids (para-aminohippurate, PAH) and bases (tetra-ethylammonium, TEA) and for malondialdehyde (MDA) content. Renal histology was also examined. CyA induced a decrease in body and kidney weight, in urine osmolality and in the excretion of total protein. Plasma-creatinine and BUN as well as MDA content of renal tissues were increased by CyA. Acyclovir alone did not induce significant changes. In comparison to CyA values, urine volume and β-NAG excretion were enhanced and TEA accumulation depressed by the concomitant administration of CyA and acyclovir. CyA- or acyclovir-treatment alone did not result in significant morphological changes. In the group co-administered CyA/acyclovir, the kidneys showed mild to moderate signs of tubulopathy. Short-term co-administration of CyA and acyclovir was concluded to have possibly increased nephrotoxic potential. Received: 28 August 1996 / Accepted: 9 April 1997     

On-site work evaluations: desensitisation for avoidance reactions following severe hand injuries

This study examined on-site work evaluations as an environmental exposure strategy to promote return to work in 15 recalcitrant patients who had failed to benefit from established methods of reducing post-traumatic stress disorder symptoms. Following the on-site work evaluation, 87% of these patients were able to use visualisation of the work setting to further desensitize themselves and returned to work within the next eight weeks. All 87% have continued to be employed at six and twelve month follow-ups. This approach holds promise for assisting patients with hand injuries who develop post-traumatic stress disorder and fail to respond to traditional psychological strategies.     

The occipital artery flap for transfer of hair-bearing tissue.

The posterior scalp is investigated as the donor site for the transfer of hair-bearing tissue based on the occipital artery. The dissection of fresh cadavers was performed and the occipital artery was noted to have three major branches including a vertical, transverse, and descending branch. The vessel connection across the midline allowed transfer of the posterior scalp to the desired recipient site. This vessel provides the possibility of transfer of large areas of hair-bearing tissue to a single stage. The variability of flap design is described as well as the technical considerations for a successful transfer.