Observations on the development of the crystalline bacterial biofilms that encrust and block Foley catheters.

The care of many patients undergoing long-term bladder catheterisation is complicated when the flow of urine through the catheter is blocked by encrustation. The problem results from infection by urease-producing bacteria, especially Proteus mirabilis, and the subsequent formation of crystalline biofilms on the catheter. The aim of this study was to discover how P. mirabilis initiates the development of these crystalline biofilms. The early stages in the formation of the biofilms were observed on a range of Foley catheters in a laboratory model of the catheterised bladder. Scanning electron micrographs revealed that when all-silicone, silicone-coated latex, hydrogel-coated latex, hydrogel/silver-coated latex and nitrofurazone silicone catheters were inserted into bladder models containing P. mirabilis and alkaline urine, their surfaces were rapidly coated with a microcrystalline foundation layer. X-ray microanalysis showed that this material was composed of calcium phosphate. Bacterial colonisation of the foundation layer followed and by 18h the catheters were encrusted by densely populated crystalline P. mirabilis biofilms. These observations have important implications for the development of encrustation-resistant catheters. In the case of silver catheters for example, bacterial cells can attach to the crystalline foundation layer and continue to grow, protected from contact with the underlying silver. If antimicrobials are to be incorporated into catheters to prevent encrustation, it is important that they diffuse into the urine and prevent the rise in pH that triggers crystal formation.

Parathyroid metabolism after operative treatment of hypercalcemic (primary) hyperparathyroidism.

Parathyroidectomy is usually followed by a decrease in serum calcium, a lessening of symptoms, and a normocalcemic state that continues for years. Evaluation of parathyroid gland function after parathyroidectomy over a protracted period showed a continued hypersecretory state in many normocalcemic patients and is reported here for the first time. Patients identified with parathyroid hyperplasia (more than one gland excised) and patients who later developed mild renal failure were excluded. Seventy-seven patients undergoing parathyroidectomy with only one enlarged gland removed and the other normal-sized glands viewed or examined by biopsy were followed up from 5 to 16 years. Two patients developed recurrent hypercalcemia at 4 and 9 years after surgery. Seventy-five patients are considered "cured" and have normal serum calcium values. However, 28 (37%) of these normocalcemic patients have persistent elevations of parathyroid hormone. This increased parathyroid gland function suggests a continuing stimulation of the remaining glands. The rarity of clinical recurrence may be related to effective adaptations that prevent overt hypercalcemia. Many parathyroid adenomas appear to represent nonneoplastic disease.

A simple procedure for isolation and purification of A-type staphylococcus enterotoxin.

A new procedure is presented for the isolation and purification of A-type staphylococcus enterotoxin. Homogeneous enterotoxin preparation was obtained by purification in 2 phases. In radial double agar-gel immunodiffusion the smallest precipitating dose of the isolated and purified enterotoxin was found to be 1.4-0.7 micrograms protein and 0.4-0.1 micrograms nitrogen. In cat experiments the dose giving a positive reaction was 2 micrograms protein or 0.5 micrograms nitrogen calculated for kg body weight.