Polyphosphate production by strains of Acinetobacter.

Of four strains of Acinetobacter isolated from a pilot plant exhibiting enhanced biological phosphate removal from sewage, two strains (RA3116 and RA3117) accumulated more than 10 times the amount of polyphosphate accumulated by the other two strains (RA3114 and RA3123). Variants isolated from RA3116 and RA3117 showed polyphosphate levels similar to RA3114 and RA3123. No correlation was found between the polyphosphate content of the strains and levels of several enzymes that have been implicated in polyphosphate formation.

Differentiation of polyphosphate and poly-beta-hydroxybutyrate granules in an Acinetobacter sp. isolated from activated sludge.

Cells containing polyphosphate 71 micrograms P (mg protein)-1 and no poly-beta-hydroxybutyrate showed metachromatic granules but no lipid granules; cells containing poly-beta-hydroxybutyrate (15% of dry weight) showed fluorescence lipid granules but no metachromatic granules; whereas cells containing both polyphosphate and poly-beta-hydroxybutyrate showed both types of granules. These observations, together with a critical review of the literature, show a clear distinction between metachromatic (or volutin) granules and lipid granules.

Characterisation of chloramphenicol resistance plasmids of Staphylococcus aureus and S. epidermidis by restriction enzyme mapping techniques.

Chloramphenicol resistance (Cmr) plasmids pSK2 and pSK5 from Staphylococcus aureus and pSK102 and pSK103 from S. epidermidis have been characterised and detailed restriction endonuclease cleavage maps constructed. TaqI digestion profiles illustrated the identity of pSK5 and pSK102 and also revealed a high degree of similarity between these four Cmr plasmids from Australian staphylococci and three Cmr plasmids from S. aureus strains of geographically unrelated origin. DNA-DNA hybridisation indicated that the chloramphenicol acetyltransferase determinant carried by pSK5/pSK102 could be found on other structurally-distinct Cmr plasmids. The role of S. epidermidis as a reservoir for Cmr plasmids found in S. aureus is discussed.

Antibiotic resistance in Staphylococcus aureus isolated at an Australian hospital between 1946 and 1981.

A total of 517 strains of Staphylococcus aureus isolated at a hospital in Melbourne, Australia between 1946 and 1981 was examined for resistance to a range of antimicrobial agents and for the presence of plasmid DNA. The use of mixed-culture transfer and restriction endonuclease analysis showed that the determinants for resistance to penicillin and to the heavy metals were carried by several related plasmids of (15-23) X 10(6) mol. wt, and that tetracycline resistance was encoded on a plasmid of 2.8 X 10(6) mol. wt in strains isolated before 1970. These phenotypes were chromosomally encoded in the majority of strains isolated thereafter. Resistance to chloramphenicol throughout the study period was plasmid-mediated. Of five aminoglycoside-resistance phenotypes, one was plasmid-mediated and three were chromosomally encoded. The remaining phenotype, specifying low-level gentamicin resistance, was found to be located on the chromosome of early isolates, but in later strains was borne by an 18 X 10(6) mol. wt plasmid which also encoded resistance to quaternary ammonium compounds.

Antibiotic susceptibilities and plasmid profiles of nosocomial methicillin-resistant Staphylococcus aureus: a retrospective study.

Methicillin-resistant Staphylococcus aureus strains isolated at a single Melbourne Hospital between 1969 and 1981 were examined for susceptibility to a range of antimicrobial agents and for the presence of plasmid DNA. Isolates obtained during 1969 possessed a plasmid of mol. wt 20 X 10(6), encoding heavy metal resistance and penicillinase production, and a plasmid of mol. wt 2.8 X 10(6), mediating tetracycline resistance. In the majority of isolates obtained after 1973, these functions were chromosomally encoded. Before 1980, both high- and low-level chromosomally-encoded gentamicin resistances were encountered, whereas isolates from 1980 and 1981 displayed low-level gentamicin resistance only; the latter phenotype was most commonly mediated by a plasmid of mol. wt 18 X 10(6) that also encoded resistance to tobramycin and kanamycin. Chloramphenicol resistance in strains isolated throughout the period was mediated by one of three plasmids, each of mol. wt c. 3 X 10(6).

Plasmid-mediated resistance to gentamicin in Staphylococcus aureus: the involvement of a transposon.

Resistance to gentamicin, tobramycin and kanamycin (GmrTmrKmr) in strains of Staphylococcus aureus isolated from clinical sources in Australia is mediated by a 4.7 kb transposable element, designated Tn4001. A 2.5 kb HindIII fragment which maps symmetrically within Tn4001, and encompasses the aminoglycoside-resistance coding region, has been shown to hybridise with fragments of identical size in HindIII digests of three different GmrTmrKmr plasmids, two of which were self-transmissible, from strains of S. aureus isolated in the USA. Examination by electronmicroscopy of self-annealed molecules of the North American GmrTmrKmr plasmids revealed the presence of stem and loop structures similar to those produced by Tn4001, but with shorter inverted repeats. These results suggest that GmrTmrKmr in strains of S. aureus isolated in the USA is, or once was, transposable, and that transposable elements analogous to Tn4001 may be found in isolates of GmrTmrKmr S. aureus worldwide.

Molecular epidemiology of multiresistant Staphylococcus aureus in Australian hospitals.

Antibiotic multiresistant isolates of Staphylococcus aureus from outbreaks of nosocomial infection throughout Australia were found to possess essentially similar patterns of antibiotic resistance. Plasmid DNA profiles from these isolates exhibited a common pattern of large plasmids, of (15-22) X 10(6) mol. wt, associated with resistance to gentamicin, kanamycin and tobramycin, plasmids of 3 X 10(6) mol. wt, mediating resistance to chloramphenicol, and cryptic plasmids of 1 X 10(6) mol. wt. Restriction endonuclease digestion confirmed the presence of related plasmids in isolates from all the hospitals that were surveyed. The homogeneity of these organisms suggests the dissemination of a multiresistant, plasmid-bearing strain of S. aureus, or its derivatives, among geographically-separated hospitals in Australia.

Multiple antibiotic resistance in Staphylococcus aureus and Staphylococcus epidermidis: plasmids in strains associated with nosocomial infection.

The plasmid DNA profiles were compared to phenotypically-similar, antibiotic-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis associated with nosocomial infections in a Melbourne hospital. Whereas resistance to gentamicin, tobramycin and kanamycin was encoded by one of 3 plasmids [pSK1, 18 megadalton (Md); pSK4, 22 Md; pSK9, 17 Md] in S. aureus, no similar plasmids were detected in S. epidermidis. Mediated exclusively by the chromosome in S. aureus, tetracycline resistance was encoded either by the chromosome or by a 2.8 Md plasmid in strains of S. epidermidis. The inability to detect common resistance plasmids in strains of S. aureus and S. epidermidis recovered from this outbreak is in contrast to recent observations with staphylococci from other geographic areas; nevertheless, on the basis of restriction endonuclease analyses of 3 Md chloramphenicol resistance plasmids, it is suggested that a common gene pool does exist within isolates of S. aureus and S. epidermidis from Melbourne hospitals.

The reconstruction of defects in the femoral shaft with vascularized transfers of fibular bone.

Seven major reconstructions of the femoral shaft using a vascularized graft of bone from the fibula were performed at the Massachusetts General Hospital from 1981 to 1984. Three patients had a post-traumatic infected non-union; one, extensive osteomyelitis of the femoral shaft; one, a fractured allograft; one, an atrophic non-union associated with radiation therapy; and one, post-traumatic loss of a ten-centimeter segment of bone. Six of the seven patients had a skeletal femoral defect, ranging from seven to fifteen centimeters in length. The average length of fibula that was used for reconstruction was 19.6 centimeters. Primary skeletal union occurred in five of the seven patients. Two patients had healing only at the distal junction and required a conventional bone graft and supplementary internal fixation of the proximal junction. At an average length of follow-up of thirty-four months, all of the patients were able to walk. Only two patients, both of whom had an extreme limb-length discrepancy, required additional support.

Growth-plate behavior in whole joint replantation in the rabbit.

We studied the behavior of the distal femoral and proximal tibial physes after whole knee-joint replantation in skeletally immature New Zealand White Rabbits. We developed an operative model in which a rabbit's knee was isolated on a vascular pedicle and was then replanted using microvascular technique. In a short-term study (three weeks or less) of ten rabbits, the patency of the vascular repairs and the resumption of metabolic activity of the cells in the growth plates were assessed. A long-term study (ninety days) of eight rabbits was designed to monitor growth after replantation. The results indicated that in rabbits, the femoral and tibial growth plates could be removed and returned to place during whole-joint replantation. If the blood supply was successfully re-established, metabolic function of the cells in the physes remained normal during the early postoperative period, and at ninety days (near the time of skeletal maturity) bone growth in the limb that was operated on was about equal to that of the opposite limb which was not operated on.

Foot reconstruction using free microvascular muscle flaps with skin grafts.

Free muscle flap transfer with skin graft coverage for extensive foot defects can be a successful form of foot reconstruction in well-selected patients who have overall normal foot innervation and deep pressure sensibility. Cutaneous sensibility does not appear to be necessary to maintain a functional or well-healed foot. The major reconstructive goal in plantar foot reconstruction is the restoration of weight-bearing during normal ambulation using regular foot apparel. Based on this reconstructive goal, the authors present their current approach in the reconstruction of extensive defects of the foot using free microvascular muscle flaps with skin grafts.

Synthetic mesh. Its use in abdominal wall reconstruction after the TRAM.

This technique has evolved over 13 years and has been associated with very few mesh-related complications. A recently reported study of 65 consecutive patients with a mean follow-up of 47.4 months reported a hernia rate of 1.5% (1 of 65) and an incidence of mesh-related infection of 1.5% (1 of 65). It appears that the use of polypropylene (Marlex mesh) offers the reconstructive surgeon several advantages, including elevation of the entire rectus flap, thereby preserving the entire blood supply to the rectus muscle. Second, the interrupted suture technique surrounding the mesh allows for greater distribution of force and diminishes the risk of fascial dehiscence. Therefore, one can obtain a tighter, narrower abdomen to achieve an improved aesthetic abdominal result. The TRAM flap breast reconstruction should not only yield a fine reconstructed breast but also deliver an aesthetic abdominal contour improvement that represents a significant benefit to the patient undergoing this procedure.

Thermocouple probe monitoring for free tissue transfer, replantation, and revascularization procedures.

As the field of microsurgery has expanded over the past decade, the need for a reliable method to monitor the patency of microvascular anastomoses has become increasingly evident. Thermocouple probe monitoring for free tissue transfer, replantation, and revascularization procedures has been done at the Massachusetts General Hospital over the past four years. The authors explain how this method of tissue viability monitoring can be a practical and useful adjunct to clinical surveillance in these complex methods of reconstruction.

Hernia prevention and aesthetic contouring of the abdomen following TRAM flap breast reconstruction by the use of polypropylene mesh.

The value of synthetic mesh use in the treatment of recurrent abdominal hernias is well recognized and has led to its advocacy by some authors as an adjunct in primary hernia repair. Mesh use in the donor-site closure associated with TRAM flap reconstruction is typically restricted to situations where undue tension or questionable tissue integrity may be predisposing factors to herniation. Although more liberal use of mesh has been advocated for these circumstances, fear of mesh complications may continue to restrict its use. We present a series of 65 consecutive patients who had routine mesh application to fascial closures following TRAM flap breast reconstruction. The use of mesh provides an added margin of strength to fascial reconstruction and was found to have additional benefit as a technical adjunct to the aesthetic aspects of the abdominoplasty. Mean patient follow-up was 56.4 months. The resulting rates of hernia (1.5 percent) and mesh-related infection (1.5 percent) demonstrate its considerable safety. We recommend consideration of polypropylene mesh use for improved strength and aesthetic quality of the donor-site closure following TRAM flap breast reconstruction.

Thermal-energy dissipation: a laboratory study to assess patency in blood vessels.

Surgeons involved in the repair of small blood vessels could benefit from a postoperative monitoring system that would allow vessel-patency determination. These experiments have confirmed that thermal-energy dissipation, measured electrically by direct vascular thermocouple application, is a sensitive and accurate indicator of regional arterial perfusion. Occlusion of arteries 1 to 2 mm in diameter produced a significant temperature decrease in direct artery measurements in the rat and island-flap artery assessments in rats and rabbits. Early recognition of vessel occlusion could allow for rapid intervention and increase the likelihood of tissue salvage. While this technology need not replace existing methodology, it does alleviate many of the problems seen with other vessel- and tissue-monitoring methods and thus may deserve further investigation.

Salvage of a failing microvascular free muscle flap by direct continuous intravascular infusion of heparin: a case report.

A free gracilis muscle transfer with skin graft was performed for reconstruction of a type IIIB lower extremity traumatic wound with acute exposure of the distal tibia fracture site and an extensive soft-tissue wound. The free muscle flap failed from a venous thrombosis that was recognized 12 hours postoperatively, and reexploration revealed extensive venous thrombosis throughout the lower leg. The flap was salvaged by direct catheter administration of heparin into the vena comitans of the gracilis artery, which bathed the newly repaired venous anastomosis with an anticoagulating dose of heparin without systemic elevation of the patient's PTT. Ultimate full flap survival and wound healing ensued.

Historical review and present status of free fat graft autotransplantation in plastic and reconstructive surgery.

Free fat graft autotransplantation for soft-tissue replacement has been a neglected subject in recent years. In a review of the literature, investigations of the various uses of free fat autotransplantation in animals and humans provide an understanding of the problems associated with the use of fat as a free graft. Results of free fat autotransplantation were found to be quite unpredictable, with wide variations in the resulting bulk of the graft. Microscopic studies of this behavior led to controversy as to whether the graft ultimately was made of surviving graft adipocytes (cell survival theory) or host adipocytes (host replacement theory). Studies revealed a "fibroblast-like" mesenchymal cell within adipose tissue that was believed to be an immature adipocyte precursor or preadipocyte. Further characterization of the preadipocyte and its complete differentiation was accomplished using tissue-culture techniques. These investigations provide evidence of the dynamic nature of adipose tissue that strongly supports the cell survival theory and gives explanation to the unpredictable behavior of free fat autografts. Many conditions treated by plastic surgeons require soft-tissue augmentation. Autogenous adipose tissue is the most appropriate and natural replacement material. With new culturing techniques, preadipocytes in a single cell suspension may provide an injectable soft-tissue replacement. This subject appears ripe for investigation.

Subciliary malar augmentation and cheek advancement: a 6-year study in 22 patients undergoing blepharoplasty.

Twenty-two patients seeking aesthetic improvement of their eyelid and orbital-cheek region underwent malar augmentation and cheek advancement in conjunction with lower eyelid blepharoplasty by means of a subciliary incision. The follow-up ranged from 12 to 78 months, with a mean follow-up of 44 months. Concomitant other aesthetic procedures were performed in 27 percent of the patients. Satisfactory goals of lower eyelid aesthetic improvement and malar augmentation with cheek advancement were achieved in 21 of 22 patients. A single patient had her implants removed within 3 weeks of her initial operation, at her request. Complications included hematoma formation in two patients, transient ectropion in two patients, and a palpable implant edge in a single patient. There were no long-term functional or aesthetic sequelae. Malar augmentation and cheek advancement have been found to be a significant adjunct to lower eyelid blepharoplasty because they improve the appearance of the cheek region and add a youthful contour to the malar area. These straightforward procedures add an effective dimension to blepharoplasty in appropriately selected patients.

Mechanical analysis of explanted silicone breast implants.

Smooth-walled silicone gel breast implants (n = 25) were removed from 15 women after implantation times that varied from 23 to 216 months (mean = 117 months; SEM = 12.9). Strips of implant shells were tested to failure by computer-controlled tensiometer. Regression analysis revealed significant negative correlation between age of implantation and shell strength (p < 0.05), shell toughness (p < 0.05), and shell elasticity (p < 0.05). These data suggest that exposure to the in vivo environment weakens silicone gel breast implant shells over time.

Staged use of soft-tissue expansion and lower thoracic advancement flap in breast reconstruction.

A single patient is presented in whom breast reconstruction after mastectomy for breast cancer has been achieved by sequential use of soft-tissue expansion followed by permanent silicone implant placement and thoracic flap advancement to define the inframammary fold. This procedure may play a useful role in patients in whom other, more complex methods of breast reconstruction are not selected or indicated and in particular in patients in whom bilateral silicone implants are utilized.