Conjugative Botulinum Neurotoxin-Encoding Plasmids in Clostridium botulinum

Clostridium botulinum produces seven distinct serotypes of botulinum neurotoxins (BoNTs). The genes encoding different subtype neurotoxins of serotypes A, B, F and several dual neurotoxin-producing strains have been shown to reside on plasmids, suggesting that intra- and interspecies transfer of BoNT-encoding plasmids may occur. The objective of the present study was to determine whether these C. botulinum BoNT-encoding plasmids are conjugative.C. botulinum BoNT-encoding plasmids pBotCDC-A3 (strain CDC-A3), pCLJ (strain 657Ba) and pCLL (strain Eklund 17B) were tagged with the erythromycin resistance marker (Erm) using the ClosTron mutagenesis system by inserting a group II intron into the neurotoxin genes carried on these plasmids. Transfer of the tagged plasmids from the donor strains CDC-A3, 657Ba and Eklund 17B to tetracycline-resistant recipient C. botulinum strains was evaluated in mating experiments. Erythromycin and tetracycline resistant transconjugants were isolated from donor:recipient mating pairs tested. Transfer of the plasmids to the transconjugants was confirmed by pulsed-field gel electrophoresis (PFGE) and Southern hybridizations. Transfer required cell-to-cell contact and was DNase resistant. This indicates that transfer of these plasmids occurs via a conjugation mechanism.This is the first evidence supporting conjugal transfer of native botulinum neurotoxin-encoding plasmids in C. botulinum, and provides a probable mechanism for the lateral distribution of BoNT-encoding plasmids to other C. botulinum strains. The potential transfer of C. botulinum BoNT-encoding plasmids to other bacterial hosts in the environment or within the human intestine is of great concern for human pathogenicity and necessitates further characterization of these plasmids

Laparoscopic hand-assisted resection of a rare intra-adrenal schwannoma

Schwannomas are well-differentiated mesenchymal tumors of the of Schwann cells that are usually benign. A lack of specific radiographic characteristics makes definitive preoperative diagnosis difficult. Therefore, despite the benign nature of these tumors, the gold-standard for symptomatic tumors is surgical resection. Here, we report the surgical management of a 37-year-old male whose pre-surgical evaluation identified a tumor in the right retroperitoneal space between the right adrenal gland and intraperitoneal porta hepatis. As a result of both the preliminary pathologic diagnosis and the close proximity of the tumor to the porta hepatis, laparoscopic hand-assisted surgical resection of the retroperitoneal tumor was performed. Postoperative pathologic diagnosis demonstrated a benign intra-adrenal schwannoma. This case highlights the importance of a broad differential diagnosis for any large retroperitoneal tumor and the requirement for post-operative pathologic diagnosis to characterize the definitive tumor location and malignant potential of the tumor

Laparoscopic donor nephrectomy increases the supply of living donor kidneys

Background. A tenet of microeconomics is that new technology will shift the supply curve to the right. Laparoscopic donor nephrectomy (LDN) is a new technique for removal of living donor kidneys. Centers performing this procedure have noted an increased number of patients presenting for donor evaluation. This has not been previously studied. Methods. The records of all LDN performed from May 1998 to February 1999 were reviewed. The following variables were examined: sex, age, related vs. unrelated donation, estimated blood loss, i.v. analgesia, length of stay, and time out of work. Donors undergoing traditional open donor nephrectomy during January 1997 to May 1998 served as the control group. A composite cost index was constructed. Results. LDN significantly decreased length of stay, pain, and time out of work; the supply function shifted to the right. Telephone interviews revealed that 47% donated solely because of the LDN procedure. Conclusions. LDN increases the supply of living donor kidneys