Products containing biocides: perceptions and realities.

The mechanisms of action for chemical germicides and antibiotics for inactivating microorganisms are significantly different and methods for determining resistance by microorganisms to these agents are also different. Chemical germicides usually have multiple targets and the mechanisms for inactivation and resistance are not measured in absolute terms but rather in the rapidity with which they reduce levels of microorganisms. The term tolerance is much more suited for germicides than the term resistance. The mechanism of resistance to chemical germicides is often dependent on the concentration of the germicide. At high concentrations multiple cellular and metabolic targets are involved, and at low concentrations fewer cellular targets. In contrast antibiotics usually have a singular cellular or metabolic target and resistance implies the ability of the microorganism to grow in the presence of the antibiotic, and in a clinical sense, to initiate or continue infection in the presence of the antibiotic. When methods used to assess resistance to antibiotics are applied to chemical germicides, inappropriate interpretations can be made regarding the ability of microorganisms to develop resistance to antibiotics as a result of developing resistance to chemical germicides. The use of chemical germicides in health-care institutions and especially the home setting has increased in recent years. Although there may be an overuse of germicides in these settings the consequence is a cost issue and not one that involves the development of antibiotic resistant microorganisms.

Products containing biocides: perceptions and realities.

The mechanisms of action for chemical germicides and antibiotics for inactivating microorganisms are significantly different and methods for determining resistance by microorganisms to these agents are also different. Chemical germicides usually have multiple targets and the mechanisms for inactivation and resistance are not measured in absolute terms but rather in the rapidity with which they reduce levels of microorganisms. The term tolerance is much more suited for germicides than the term resistance. The mechanism of resistance to chemical germicides is often dependent on the concentration of the germicide. At high concentrations multiple cellular and metabolic targets are involved, and at low concentrations fewer cellular targets. In contrast antibiotics usually have a singular cellular or metabolic target and resistance implies the ability of the microorganism to grow in the presence of the antibiotic, and in a clinical sense, to initiate or continue infection in the presence of the antibiotic. When methods used to assess resistance to antibiotics are applied to chemical germicides, inappropriate interpretations can be made regarding the ability of microorganisms to develop resistance to antibiotics as a result of developing resistance to chemical germicides. The use of chemical germicides in health-care institutions and especially the home setting has increased in recent years. Although there may be an overuse of germicides in these settings the consequence is a cost issue and not one that involves the development of antibiotic resistant microorganisms.

Susceptibility of vancomycin-resistant enterococci to environmental disinfectants.

OBJECTIVE: To determine the susceptibilities of vancomycin-resistant and -sensitive enterococci (VRE and VSE) to various concentrations of commonly used, commercial, hospital-grade disinfectants. DESIGN: A microbial suspension test using inocula of 10(8) cells per mL in a disinfectant test dilution was used to determine inactivation kinetics of the test strains. In each test, 1-mL aliquots were removed from the cell-disinfectant mixtures at 15 and 30 seconds and then at 1-minute intervals for 5 minutes and neutralized. Appropriate serial dilutions were plated on agar medium for enumeration of survivors. RESULTS: VRE and VSE challenge inocula (in the absence of any additional protein or serum challenge) were below the limit of detection (5 colony-forming units/mL) after 15 seconds' exposure to the manufacturers' suggested use-dilutions of quaternary ammonium, phenolic, or iodophor germicidal detergents. In subsequent tests, when the disinfectants were diluted far beyond-the recommended use-dilutions (extended dilution), no differences were demonstrated between the susceptibilities of VRE and VSE. CONCLUSIONS: VRE and VSE are sensitive to a spectrum of commonly used environmental disinfectants and have parallel inactivation rates when challenged with extended dilutions of these products. Our findings did not demonstrate a relationship between antibiotic and germicide resistance. Routine disinfection and housekeeping protocols presently used in hospitals need not be altered due to concerns about the potential for environmentally mediated transmission of antibiotic-resistant microorganisms.

National surveillance of dialysis associated diseases in the United States--1994.

Dialysis centers in the United States were surveyed in 1994 regarding a number of hemodialysis associated diseases and practices. A total of 2,449 centers, representing 206,884 patients and 50,314 staff members, responded. In 1994, 99% of centers used bicarbonate dialysate as the primary method of dialysis, 45% used high flux dialysis, and 75% reused dialyzers. Hepatitis B vaccine had been administered to 31% of patients and to 80% of staff members. Acute infection with hepatitis B virus occurred in 0.1% of patients and was more likely to be reported by centers with lower proportions of patients vaccinated against hepatitis B virus and those not using a separate room and dialysis machine to treat hepatitis B surface antigen positive patients. The prevalence of antibody to hepatitis C virus was 10.5% among patients and 1.9% among staff members and varied according to geographic region. Pyrogenic reactions in the absence of septicemia were reported by 22% of centers and were most highly associated with dialyzer reuse. Human immunodeficiency virus infection was reported to be present in 1.5% of patients; 37% of centers provided hemodialysis to one or more patients infected with human immunodeficiency virus.

National surveillance of dialysis associated diseases in the United States, 1993.

To determine trends in a number of hemodialysis associated diseases and practices, the Centers for Disease Control and Prevention, in collaboration with the Health Care Financing Administration, performed a mail survey of 2,304 chronic hemodialysis centers in the United States in 1993. By the end of 1993, at least three doses of hepatitis B vaccine were administered to 29% of patients and 76% of staff at responding centers. Hepatitis B surface antigen was present at low frequency in patients (incidence = 0.1%, prevalence = 1.2%) and staff members (incidence = 0.2%, prevalence = 0.3%). The 1993 incidence of hepatitis B virus infection among patients was higher at centers that accepted hepatitis B surface antigen positive patients but did not use a separate room and dialysis machine for treatment of these patients, government and profit (versus nonprofit) centers, and centers in four End Stage Renal Disease Networks. The prevalence of antibody to hepatitis C virus was 9.7% among patients and 1.6% among staff members. Pyrogenic reactions in the absence of septicemia were reported by 21% of centers and associated with use of high flux dialysis. Human immunodeficiency virus infection was known to be present in 1.5% of patients; 34% of centers reported providing hemodialysis to one or more human immunodeficiency virus infected patients.

Comparison of chemical dehydration and critical point drying for the stabilization and visualization of aging biofilm present on interior surfaces of PVC distribution pipe.

In this study, fixation of attached glycocalyx on the interior surfaces of polyvinyl chloride distribution pipe remnants was compared with and without ruthenium red/osmium tetroxide and, in the final preparatory phase, with chemical dehydration and critical point drying. SEM examination of interior surface of the polyvinyl chloride pipe showed varying concentrations of adherent bacteria, depending on the preparatory technique used. It was concluded that using a combination of ruthenium red/osmium tetroxide and critical point drying is the optimum method for visually demonstrating aging biofilm on the interior surface of contaminated polyvinyl chloride pipe.

Microbiologic considerations. Disinfection and sterilization strategies and the potential for airborne transmission of bloodborne pathogens.

Bloodborne pathogens are transmitted from person to person by sexual contact and by injection of drugs and, in health-care settings, by needlesticks and, in the case of HBV, by mucous membrane exposure. Conventional disinfection and sterilization and housekeeping strategies are sufficient for the environmental control of bloodborne viruses. Environmentally mediated infection transmission of bloodborne viruses is unlikely and only HBV, because of the extraordinarily high viral concentration in blood, is thought to have a real potential for such transmission. No epidemiologic or laboratory data support the hypothesis that surgeons or other health care workers are at increased risk of infection by bloodborne pathogens. Although theoretically possible, airborne transmission does not appear likely. Studies that claim to show the potential for airborne transmission of bloodborne pathogens ignore the basic principles of aerobiology and the requirements for proving environmental transmission.