Gerald Reybrouck

Handwashing and hand disinfection

One of the most efficient methods of restricting the transfer of infectious material from one patient to another is by the application of a handwashing and hand disinfection policy (Reybrouck, 1983). Since members of hospital staff are often confused about the object of different forms of cleansing and disinfection, it seems appropriate to define these general aims and terms before discussing systematically the individual methods and their efficacy.

Role of the hands in the spread of nosocomial infections. 1

There is some evidence to suggest that nosocomial infections are usually transmitted in hospital wards by contact from a source (an infected patient, a carrier, a common inanimate source) to a previously uninfected patient. This route is usually more hazardous than the airborne route since larger numbers and often more virulent organisms can contaminate the susceptible patient at one time. Direct inoculation from an infective lesion is uncommon, and infective organisms are mostly transferred indirectly by means of a vehicle. Inanimate objects, such as instruments, thermometers, breathing apparatus and linen, can serve as vehicles, and transmission in this manner can be prevented by disinfection or sterilization of the relevant item. The most common vehicles, however, are the hands of members of the hospital staff. Hands cannot be sterilized, and the disinfectants which are most effective on inanimate objects are usually too toxic for application to the skin. Moreover, the skin has its own microbial flora, which is more difficult to remove or destroy than the micro-organisms present on inanimate objects. If, after disinfection, vegetative micro-organisms can be isolated from an instrument, one may conclude either that the measure was inefficient or that contamination took place subsequent to disinfection. This is not true for the skin. Pathogenic organisms deposited on the skin may become part of the normal cutaneous flora, or may only survive for a short time. The normal skin inhabitants also influence the survival of contaminants, and there is a reciprocal action between the micro-organisms on the skin and their habitat. A knowledge of cutaneous ecology is of value for the understanding of the mechanisms through which infection is transmitted by the skin, especially the hands, and also the incidence of carriers and the importance of the carrier site. Application of this knowledge should lead to an efficient policy of prophylaxis and disinfection.

The national prevalence survey of nosocomial infections in Belgium, 1984

A national one-day prevalence survey of nosocomial infections was carried out in March 1984 in 106 Belgian acute-care hospitals involving 8723 patients of whom 6130 had undergone surgery. Three infections were studied: surgical wound infection, bacteraemia and urinary-tract infection. One or more of these three infections was recorded in 9.3% of all patients and in 11.8% of surgical patients. Prevalences increased with increasing duration of hospital stay and with higher ages, but the association of HAI with age was no longer significant after correction for duration of hospital stay. Prevalences varied considerably in different specialties. After adjustment for age and duration of stay, there was no association between perioperative antibiotic prophylaxis and the prevalence of the infections studied, but bias due to selection of higher risk patients in the antibiotic group was probable. Larger hospitals had a higher overall prevalence, but populations differed according to the size of the hospital. Bacteraemia was strongly associated with the presence of an intravenous catheter, and urinary-tract infection with a urinary catheter.

The testing of disinfectants

Abstract Although all disinfectant tests have the same final purpose, namely measuring the antimicrobial activity of a chemical substance or preparation, a large number of testing methods has been described. They are subdivided into suspension tests, carrier and surface disinfection tests and other practice-mimicking tests. The suspension tests comprise qualitative and quantitative suspension tests, and, as derived tests, the determination of the phenol coefficient and capacity tests. There is an essential difference between a carrier test and a surface disinfectant test: in the former case the carrier is submerged in the disinfectant solution during the whole exposure time, whereas in the latter case the disinfectant is applied on the carrier for the application time and thereafter the carrier is drying during the exposure. The basic principle now widely accepted is that the antimicrobial efficiency of a disinfectant is examined at three stages of testing. The first stage concerns laboratory tests in which it is verified whether a chemical compound or a preparation possesses antimicrobial activity. For these preliminary screening tests, suspension tests are considered. In the second stage of tests, disinfection procedures and not disinfectants are examined. It is determined under which conditions and at which use-dilution for a given application the preparation is active: the tests simulate real-life situations; such tests are carrier tests for the disinfection of materials by submersion and surface disinfection tests. The last stage takes place in the field, and comprises the in-loco or in-situ tests with as variants the in-use tests, which examine whether, after a normal period of use, germs are still killed by the disinfectant solution. It is the task of the European and international standardization organisations to develop new standards and to elaborate tests, which predict the effectiveness of a preparation in practice under variable circumstances.

Assessment of the efficacy of disinfectants on surfaces

Abstract The Literature on testing the efficacy of disinfectants covers a century. Most predominant and standardized are the so called suspension tests that allow for the quantitative estimation of the microbicidal activity (log reduction factors) of disinfectants on test organisms suspended in solutions of these products. Since the outcome of suspension tests might be a poor predictor for the efficacy of a disinfectant under practical circumstances, especially with regard to bacteria attached to surfaces, a variety of test procedures have been designed to mimic those conditions. Within the framework of CEN/TC 216 a quantitative surface test has been developed to assess the activity of disinfectants on bacteria or fungi attached to steenless steel surfaces. Preliminary data suggest that covering a dried inoculum with disinfectant without any further mechanical action to improve contact between organisms and disinfectant, will usually result in lower reduction factors than those obtained with suspension tests. Comparative testing further suggests that by applying mechanical action, with the effect of resuspending cells in the liquid on the surface,—similar to mopping, brushing etc.— will result in higher reduction rates. Although not unexpected these findings emphasize the importance of designing test methods based on practical applications of disinfectants.

International standardization of disinfectant testing: is it possible?

At present there is no harmonization of antiseptic and disinfectant testing in the world, not even in Europe. In the case of surface disinfection the bactericidal activity of preparations is evaluated by very different techniques. The Association of Official Analytical Chemists of the USA prescribes a carrier test, the use-dilution test, to determine the maximum dilutions that are effective for practical disinfection. In Germany and in France, the final test for determining the use-dilution of a disinfectant preparation is a practical test mimicking conditions of use. In the UK the Kelsey-Sykes test, a capacity test, is more popular. The Council of Europe prescribes a quantitative suspension test with organic load, the European Suspension Test (EST), as the definitive testing method for disinfectants used in food hygiene. It is to be expected that these varied testing techniques would yield different results. The evaluation of a testing technique should be supported by correlation of the results of the tests with efficacy in practice. The recent founding of a technical committee of the European Committee for Standardization (CEN) raises great hope that, at least in Europe, a harmonization of the testing techniques will be possible in the near future.

National Study On the Utilization of Prophylactic Antibiotics in Surgery, Belgium, 1986

During the last week of May 1986, a 1-week prospective study on antibiotic utilization in surgical patients was held in 104 (42%) of the 247 Belgian acute care hospitals. All surgical patients with a post-operative stay of at least 3 days were studied, involving 3112 patients. Each patient was observed for 7 days, starting from the day before surgery. Antibiotics were administered to 71.9% of all patients; 21.9% received therapeutic antibiotics and 52.9% prophylactic antibiotics; 2.9% received both. Of the 1285 patients undergoing a surgical procedure with no indication for antimicrobial prophylaxis, 50.7% nevertheless received prophylaxis; 92.8% of patients with a generally recognized indication for prophylaxis received antibiotic prophylaxis. Less than one fifth (17.1%) of all prophylactic courses were stopped on the day of the intervention whilst 26.3% were continued up to the fifth post-operative day or beyond. The most frequently prescribed drugs for this indication included first and second generation cephalosporins and nitroimidazoles. The number of different generic drugs utilized per hospital ranged from 1 to 18 (mean: 7.7).