Microwave: practical cost-effective method for sterilizing urinary catheters in the home.

We used a standard microwave oven to sterilize red rubber catheters used for intermittent self-catheterization. Catheters were incubated for sixty minutes in a suspension of microorganisms isolated from the urine of patients with urinary tract infections. For each trial, 6 catheters were removed from their respective suspensions, placed in separate plastic freezer bags, distributed evenly in a microwave oven (avoiding cold spots), and microwaved simultaneously for twelve minutes. A control catheter was not microwaved. Two strains of each microorganism were tested. The urinary isolates were Escherichia coli, Klebsiella sp., Proteus sp., Enterobacter sp., Pseudomonas sp., Streptococcus sp., Staphylococcus sp., and Candida sp. In each experiment, all 6 catheters were sterilized. Repeat sterilization in the microwave oven did not affect the integrity of the catheters or the plastic bags. A water heat sink of constant volume was employed. A home microwave oven may be used as a method to sterilize red rubber catheters for reuse with a recommended time of twelve minutes at full power. This technique makes aseptic intermittent self-catheterization a practical possibility.

Microwave sterilization: a method for home sterilization of urinary catheters.

A standard microwave oven has been used to sterilize catheters used for intermittent self-catheterization. Catheters were incubated for 60 minutes in a suspension of microorganisms isolated from the urine of patients with urinary tract infections. Each catheter was removed from the suspension, placed in a paper bag and microwaved for 0 to 30 minutes. A control catheter was not microwaved. We tested 42 strains of microorganisms to determine the minimum microwaving time needed to sterilize the catheters. Representative urinary isolates of Escherichia coli, and Klebsiella, Proteus, Enterobacter, Pseudomonas, Staphylococcus, Streptococcus and Candida species were tested. Mean sterilization time for all strains was 13.0 minutes (standard deviation +/- 5.7 minutes), with a range of 4.0 to 28.6 minutes. Repeat sterilization in the microwave oven did not affect the integrity of the catheter. A water heat sink of constant volume was required. A home microwave oven may be used as a method to sterilize red rubber catheters for reuse. This technique makes aseptic intermittent self-catheterization a practical possibility.

Single-dose ceftriaxone treatment of urinary tract infections.

Single-dose antibiotic therapy for urinary tract infections in which no underlying structural or neurologic lesions are present holds the promise of greater patient compliance and convenience. We present the results of a study comparing a single intramuscular dose of a long-acting, third-generation cephalosporin, ceftriaxone, with a standard, five-day regimen of trimethoprim-sulfamethoxazole (TMS). Fifty-two patients were entered into the study. After randomization, 26 were assigned to the TMS group and 26 were assigned to the ceftriaxone group. Of the patients who completed the study, 13 of the TMS group had positive cultures at the time of initial presentation, and 20 of the ceftriaxone group had positive cultures. There was no statistical difference between the groups in symptoms of dysuria, hematuria, frequency, flank pain, and nocturia (alpha = .05). The physical parameters of age, blood pressure, pulse, and temperature were similar in the two groups (alpha = .05), as were the types of infecting organisms (alpha = .05). When comparing the two regimens, the ceftriaxone group cure rate (18 of 20, 90%) was not found to be significantly different from that of the TMS-treated control group (13 of 13) (alpha = .05).

Overnight concentration of urine. Natural defense mechanism against urinary tract infection.

Growth of Escherichia coli 06 was compared in concentrated overnight urine and dilute daytime urine. In concentrated urine, 90 per cent of the initial inoculum died during the lag phase and surviving bacteria had a long lag period before they started to grow. Once growth began, these bacteria required fifty-five hours to reach their maximum growth yield. In dilute urine, 75 per cent of the same bacteria survived the lag phase; once growth began, they reached maximum growth yield in only thirteen hours. These observations suggest that concentrated overnight urine serves as a natural defense mechanism against urinary tract infections.

Office practice survey of urease positive bacterial pathogens causing urinary tract infections.

Office patients with a positive urinary tract infection (UTI) were screened for the presence of a urease positive microorganism by a rapid biotyping. Approximately 12 per cent of the UTI episodes were caused by a urease positive organism. Over 95 per cent of Proteus and Klebisella isolates were urease positive, and a lesser percentage of Pseudomonas. No Escherichia coli were urease positive. Determination of urease production can be assessed by the standard API (Analytab Products Inc.) biotyping technique for gram negative organisms. A specific digit in the biotype code indicates urease activity.

Classification of urinary tract infections by biotype identification of the pathogens.

Bacterial isolates from urinary tract infections were identified by biotyping. During a 2-year period all episodes of urinary tract infection in 276 patients from an office practice could be classified into 4 categories: 1) first or simple urinary tract infection, 2) recurrent urinary tract infection owing to unresolved bacteriuria during treatment, 3) recurrent urinary tract infection owing to bacterial persistence and 4) recurrent urinary tract infection owing to reinfection.

Growth of Pseudomonas aeruginosa in normal and burned skin extract: role of extracellular proteases.

Growth curves and mean generation times (MGT) were determined for Pseudomonas aeruginosa strain M-2 (protease +) and strain PA-103 (protease +/-) in burned skin extract (BSE) and in normal skin extract (NSE). Strain M-2 grew on NSE or BSE with an MGT of 30 min. Strain PA-103 grew in NSE at a similar MGT; however, PA-103 in BSE had a MGT of 65 min. When protease was added to BSE, PA-103 grew as rapidly as M-2. When ammonium sulfate was added to inhibit protease production, the MGT of M-2 slowed to that of M2 in both BSE in NSE. The MGT of PA-103 in amino acid-supplemented BSE was similar to that of PA-103 in BSE. The MGT of PA-103 in amino acid-supplemented BSE was similar to that of M-2 in both BSE andNSE. These data suggest that protease may serve as a virulence factor by modifying the available nutrients in burned skin. As a result, nutrients are formed that permit an enhanced growth rate and amore rapid establishment of the infection in the host.

Uptake of extracellular biotin by Escherichia coli biotin prototrophs.

Uptake of exogenous biotin by two Escherichia coli biotin prototroph strains, K-12 and Crookes, appeared to involve incorporation at a fixed number of binding sites located at the cell membrane. Incorporation was characterized as a binding process specific for biotin, not requiring energy, and stimulated by acidic pH. Constant saturation quantities of exogenous biotin were incorporated by these cells, and the amounts, which were titrated, depended on whether the cells were resting or dividing. Resting cells incorporated exogenous biotin amounting to 2% of their total intracellular biotin content. Fifty percent of the exogenous biotin was incorporated into their free biotin fraction, and 50% was incorporated into their bound biotin fraction. On the other hand, dividing cells incorporated exogenous biotin into all of their intracellular sites, 88% going into the intracellular-bound biotin fraction, and 12% going into the free biotin fraction. Calculations suggested that each cell contained approximately 3,000 binding sites for biotin. It was postulated that biotin incorporation sites might have been components of acetyl coenzyme A carboxylase located at or near the membrane.

Biotin uptake by cold-shocked cells, spheroplasts, and repressed cells of Saccharomyces cerevisiae: lack of feedback control.

Cold-osmotic-shocked cells and spheroplasts of Saccharomyces cerevisiae (ATCC 9896) display a biotin uptake system similar to that observed in intact cells. 2-Mercaptoethanol was found to inhibit biotin transport. Cells repressed for biotin uptake by growth in excess biotin (25 ng/ml) possess an energy-dependent transport system that has a K(m) for biotin of 6.6 x 10(-7) M and a V(max) equal to 39 pmol per mg (dry weight) per min. A similar K(m) (6.4 x 10(-7) M) but a considerably higher V(max) (530 pmol per mg (dry weight) per min) was determined for biotin uptake by cells grown in sufficient biotin (0.25 ng/ml). The V(max) rates of biotin uptake by both repressed and derepressed cells were increased approximately 35-fold in the presence of glucose. These yeast cells appear to regulate their biotin uptake by two mechanisms. An exit system provides for immediate adjustments, whereas turnover of the transport system and repression of new synthesis establishes a slower adaptation to changes in the environment. Feedback inhibition was ruled out as a mechanism of regulation of transport.