METHODS FOR DISINFECTION OF HANDS AND OPERATION SITES

maxPIE: An innovative high throughput approach to enhance pathogen inactivation practices

Effective pathogen inactivation is highly desired in public health but limited by existing methods each capable of assessing pathogen inactivation effectiveness (PIE) only in a specific condition. We therefore developed a novel method maxPIE designed to identify maximal PIEs across inactivation conditions by leveraging the power of massive array technologies. maxPIE implements a three-step algorithm to quickly identify maximal PIEs of inactivation treatments: (1) dilute pathogens into different initial titers each stored in an array well, (2) submit one sorted array to one treatment, (3) scan the treated array to find the maximum. maxPIE outperformed the conventional methods in (a) inactivating S. aureus using ultraviolet light of different wavelengths with different durations; (b) antibiotic treatment of S. aureus, E. coli, and multidrug-resistant E. coli; (c) inactivating S. aureus in plasma using ultraviolet light in different wavelengths with and without riboflavin. maxPIE was easy to understand and interpret and was robust in situations where conventional PIE methods would suffer. Hence, maxPIE can serve as an innovative and high throughput approach that can be widely used to enhance pathogen inactivation practices.

A novel device for preoperative skin preparation to reduce the risk of injury and surgical site infection during lower limb surgery

Surgical site infection (SSI) continues to be a feared complication of surgery but especially orthopaedic surgery where a superficial SSI has been estimated to add nine days to the hospital stay and an average of £2500 to the cost. Despite the efficacy of all skin preparation agents being maximal at around 10 minutes no current system, apart from the double prep method attributed to Sir John Charnley, allows adequate control of bacteria. Current techniques of skin preparation require lifting of the limb with an associated risk of injury to theatre operatives. In order to provide for longer duration of contact, potentially better antisepsis and to remove the dangers inherent in lifting the limb we developed a novel system for limb antisepsis prior to surgery. To demonstrate efficacy we performed a single blind randomised controlled trial powered to demonstrate non-inferiority. We demonstrated a significant benefit of the device in terms of bactericidal effect. Whilst only recently entering full production, we would recommend the system as a significant improvement over current techniques of limb antisepsis.

Bacterial safety of cell-based therapeutic preparations, focusing on haematopoietic progenitor cells

Bacterial safety of cellular preparations, especially haematopoietic progenitor cells (HPCs), as well as advanced therapy medicinal products (ATMPs) derived from stem cells of various origins, present a challenge for physicians, manufacturers and regulators. The article describes the background and practical issues in this area and illustrates why sterility of these products cannot currently be guaranteed. Advantages and limitations of approaches both for classical sterility testing and for microbiological control using automated culture systems are discussed. The review considers novel approaches for growth-based rapid microbiological control with high sensitivity and faster availability of results, as well as new methods for rapid bacterial detection in cellular preparations enabling meaningful information about product contamination within one to two hours. Generally, however, these direct rapid methods are less sensitive and have greater sampling error compared with the growth-based methods. Opportunities for pyrogen testing of cell therapeutics are also discussed. There is an urgent need for development of novel principles and methods applicable to bacterial safety of cellular therapeutics. We also need a major shift in approach from the traditional view of sterility evaluation (identify anything and everything) to a new thinking about how to find what is clinically relevant within the time frame available for the special clinical circumstances in which these products are used. The review concludes with recommendations for optimization of microbiological control of cellular preparations, focusing on HPCs.

Surgical hand rub: Influence of duration of application on the immediate and 3-hours effects of n-propanol and isopropanol

BACKGROUND

The recommended duration for surgical hand treatment has been changed from 10 over 5 to 3 minutes and even shorter.

OBJECTIVES

Our objective was to study the impact of the length of surgical hand antisepsis with n-propanol 60% (vol/vol) or isopropanol 70% (vol/vol) applied for 1, 3, or 5 minutes on the reduction of resident hand flora in the setting of the microbiologic laboratory for experimental and applied testing of disinfectants and antiseptics at the Medical University Vienna, Austria, using a Latin Square design.

METHODS

Our methods were according to the Austrian Guidelines for Testing Products for Surgical Hand Antisepsis. The release of bacterial hand flora of 21 subjects is assessed before and immediately after disinfection from one hand and 3 hours later from the other, meanwhile gloved, hand. Mean reduction factors (RF) are calculated.

RESULTS

The immediate mean log(10) RFs with n-propanol or isopropanol were 1.05, 2.03, and 2.30 and 0.74, 1.48, and 2.12, respectively, when applied for 1, 3, or 5 minutes, respectively. After 3 hours, the respective mean log(10) RFs were 0.45, 1.01, and 1.60 and 0.19, 0.79, and 1.03. Thus, with increasing length of application, a highly significant trend (P < .001) toward higher log(10) reductions was demonstrated. At both sampling times, n-propanol was more effective than isopropanol at the corresponding treatments. Furthermore, a highly significant (P < .001) association was found between the individual volunteers and the effect of the antiseptics on their hands.

CONCLUSION

The efficacy of surgical antisepsis is significantly associated with the length of application.

Comparison of bacterial counts in glove juice of surgeons wearing smooth band rings versus those without rings

BACKGROUND

Removal of rings is recommended before surgeons aseptically prepare for surgical procedures.

OBJECTIVES

This study was undertaken to determine whether there is a difference between bacterial counts under surgical gloves of ring wearers compared with nonring wearers after proper aseptic hand preparation and 3 hours of wear.

METHODS

Twenty volunteer veterinary medical students were divided into 2 groups: One group wore a smooth ring band (without projections or mounted stones) on their ring finger, and the other group did not wear a ring. A modified glove juice method was used to obtain bacterial counts (colony-forming units/mL) inside surgically gloved hands prior to a proper aseptic hand preparation and 3 hours after hand preparation and wear. Each of the pre- and postsurgical glove juice samples were inoculated onto Letheen agar plates, which were incubated aerobically under atmospheric conditions for 48 hours at 35 degrees C. Gloves were tested for perforations using a water pressure test.

RESULTS

No differences, or significant change, in bacterial counts were found before or after surgery between all ring hands and nonring hands or between ring and nonring hands for ringed participants. No differences in bacterial counts were found within perforated versus nonperforated gloves.

CONCLUSION

There is no compelling evidence to suggest that surgeons wearing rings possess higher bacterial counts under their gloves during surgery.

A prospective controlled trial of the efficacy of isopropyl alcohol wipes before venesection in surgical patients

It has previously been suggested that skin preparation before venesection with antiseptic agents is unnecessary. However thousands of doctors and medical students continue to use isopropyl alcohol (IPA) swabs for venesection, at an estimated cost of 10,000 P per annum in a 500 bed hospital. An audit of IPA swab use among junior doctors and medical students at our institution was undertaken; 76% of doctors and 100% of medical students routinely prepared the skin with alcohol before venesection and only one used the swabs correctly. A randomised single-blind controlled trial was conducted of IPA versus no IPA skin preparation before venesection. There were 194 patients in the study, 93 in the IPA group and 101 controls. There was no statistical difference with respect to complications at the venepuncture site between the two groups.

The use of alcoholic wipes for disinfection of injection sites

An evaluation of a proprietary skin disinfection wipe - paper impregnated with 70% isopropanol - with a discussion of pre-inoculation disinfection methods used.

To dry or not to dry? An assessment of the possible degradation in efficiency of preoperative skin preparation caused by wiping skin dry

A controlled study of the effects of wiping skin dry after application of aqueous povidone-iodine was carried out in 24 subjects. There was no significant difference in the reduction from baseline counts of skin flora at 5, 30, 60 and 120 min between wiping the agent off after 30 s of application and leaving it to dry. It would appear that wiping skin dry that has been prepared for operation with this solution in order to allow application of adhesive drapes is a bacteriologically safe practice.

Soap pH and the effectiveness of alcoholic hand antiseptics

This study was done to investigate if the pH-value of a soap used for handwashing had any effect on the immediate and the prolonged effectiveness of alcoholic hand disinfectants. One acidic soap (pH = 3.5) and one alkaline soap (pH = 8.5) were tested in combination with 70% and 90% ethanol and alcoholic chlorhexidine. Bacterial counts from the hands of 26 test persons were obtained using the fingerprint method. The fingerprints were taken before and after handwashing, after hand disinfection and after 3 h of wearing sterile latex gloves. The results showed that soap pH did not influence significantly the effectiveness of a subsequent hand disinfection. The combined use of alkaline soap and alcoholic chlorhexidine showed a tendency to smaller variation in bacterial reduction and greater effectiveness. This combination was the only one that led to an increased bacterial reduction after 3 h.

Current use of skin and wound cleansers and antiseptics

Out of the tumult of a turbulent, eight-century-long background of surgical skin and wound cleansing methods has come a set of basic principles that serve as performance specifications for new developments. Alcohol remains the superior skin antiseptic. Its characteristic rapid-drying effect and consequent loss of bactericidal action can be overcome by maintaining wetness or by admixture with emollients or longer-acting antiseptics. Today's combinations of cleaners, alcohol, and either iodophores or chlorhexidine have emerged from previous eras characterized by the use of metallic compounds, halogen compounds, and tincture of iodine. Published guidelines are important but must be looked upon as current consensus rather than standard practice.

The effect of polyvinylpyrrolidone-iodine as an disinfectant in eye surgery

105 patients admitted for cataract surgery were treated pre-operatively with polyvinylpyrrolidone-iodine (PVP-I) as a disinfectant, and consecutive bacterial cultures were obtained before initiating surgery and at the end of the operation. A control group (n = 99) only had a standard disinfection procedure of the eye (including instillation of Terramycin cum polymyxin B cream in the conjunctival sac the evening before surgery). The cultures obtained from the conjunctival sac of the control group principally showed growth of Staph. albus and Staph. aureus, and to a minor degree diphtheroids (Corynebacterium species). Proteus mirabilis, Escherichia coli and micrococci. There was a significant quantitative diminished growth (P less than 0.05) of bacteria in the group of patients treated with PVP-I compared to the control group. Concerning the growth of Staph. albus, this was reduced to almost one third and other bacteria were almost eliminated in the group receiving PVP-I. As we disclosed no toxic or allergic reaction post-operatively which could be related to the use of PVP-I as a disinfectant, this agent seems to constitute an effective pre-operative antimicrobial treatment, taking into consideration the broad antimicrobial spectrum of PVP-I shown by other authors.

Comparative antibacterial effectiveness of seven hand antiseptics

Seven hand antiseptics (alcohol-, iodophor- and chlorhexidine preparations) were compared for antibacterial effectiveness using finger-print contact sampling on blood agar in duplicate series with 18 students as test persons. Bacterial samples were obtained before and after handwashing (with unmedicated liquid soap) as well as after hand disinfection. Hibiscrub was tested without prewashing. The antiseptics were rubbed into the skin and the hands left uncontaminated for 2 min before sampling. Due to results showing unexpectedly low antibacterial effectiveness of 70% (v/v) ethanol, a series of supplementary experiments with ethanol (70% (v/v) and 80% (v/v] and isopropanol (60% (v/v] were performed with 10 laboratory staff-members. These experiments confirmed the previously demonstrated weak antibacterial effect of 70% (v/v) ethanol on the normal hand flora. Alcoholic chlorhexidine solutions and Hibiscrub were the only preparations that gave significant, mean reductions (97.9-99.9% and 80.3-93.4%, respectively) in the number of colony forming units. According to the present study, these are the only test preparations that can be recommended for presurgical hand disinfection, and when hand disinfection is needed in general dental practice.

Increased bactericidal activity of dilute preparations of povidone-iodine solutions

Recent confirmation of intrinsic bacterial contamination of 10% povidone-iodine solution has raised questions regarding the bactericidal mechanism of iodophors and the possibility for survival of vegetative bacterial cells in iodophor solutions. In this laboratory investigation, five different species were exposed to various dilutions of three commercial preparations of 10% povidone-iodine solution; survival was assessed after exposure for time periods varying between 0 and 8 min. All brands of povidone-iodine solution tested demonstrated more rapid killing of Staphylococcus aureus and Mycobacterium chelonei at dilutions of 1:2, 1:4, 1:10, 1:50, and 1:100 than did the stock solutions, S. aureus survived a 2-min exposure to full-strength povidone-iodine solution but did not survive a 15-s exposure to a 1:100 dilution of the iodophor. Both stock and dilute preparations of 10% povidone-iodine solution demonstrated rapid bactericidal action against Klebsiella pneumoniae, Pseudomonas cepacia, and Streptococcus mitis.

Topical application of povidone-iodine in the management of decubitus and stasis ulcers

The efficacy of topical applications of povidone-iodine (Betadine solution and ointment) for the control of infection associated with decubitus and stasis ulcers was evaluated in 18 male outpatients (age range, 33--68 years). Dressings were changed twice daily over a period of 42 days. Statistically significant improvement was noted in the following signs and symptoms: edema, pain, erythema, ulcer size, and ulcer depth. All patients experienced some degree of symptomatic relief and clinical improvement within two weeks after starting therapy. At the end of the study, 67 percent of the ulcers were clinically cured and 33 percent showed improvement. Acceptance by the patients was excellent, with no reported side effects or sensitization reactions. Povidone-iodine used in a daily regimen of ulcer care can reduce the level of infection and promote healing.

Delayed antimicrobial effects of skin disinfection by alcohol

Aqueous suspensions of Staphylococcus aureus were deposited on a Millipore filter and then exposed for a few seconds to 70% ethyl alcohol. Viable counts of bacteria extracted from the filter immediately after exposure to alcohol, and, in replicate experiments, after a further period of 3 h, showed that the mean immediate reduction of 97.6% in viable counts after treatment with alcohol was followed by a further mean reduction of 67.1% in the further 3 h holding time; the same bacterial suspensions allowed to dry on Millipore filters without exposure to alcohol showed a significantly smaller mean reduction in viable counts (34.3%) during a further 3 h holding time. These findings support the view that the reported further fall in numbers of bacteria on hands while wearing gloves for 3 h after alcohol disinfection can be explained by sublethal damage to some of the bacteria, from which they can recover only if promptly inoculated on culture medium.

Limits to progressive reduction of resident skin bacteria by disinfection

Antiseptic preparations used repeatedly to disinfect the skin caused a reduction in yield of resident flora to a low equilibrium level beyond which further reduction did not occur. This equilibrium varied with the antiseptic preparation used. In a comparison of three preparations, the lowest equilibrium level was obtained with 95% ethyl alcohol. The further reduction in yield of skin bacteria on using alcohol after repeated disinfection with an antiseptic detergent preparation ('two-phase' disinfection) was not paralleled by a further reduction when the preparations used in the two phases were reversed, the antiseptic detergent being used after repeated disinfection with ethyl alcohol. 'Two-phase' disinfection was therefore seen to be due to further reduction in skin bacteria from the low equilibrium obtained with the antiseptic detergent to the lower level obtainable by alcohol disinfection. When repeated disinfection to equilibrium with alcohol was followed by a 'second-phase' handwash with a non-antiseptic detergent and water, there was a large increase in the yield of skin bacteria. This finding supports the view that a low equilibrium level occurs when the reduction in density of accessible bacteria through disinfection is balanced by the emergence of bacteria drawn from deeper layers of the skin.

Comparative study on the antimicrobial effect of 0.5% chlorhexidine gluconate and 70% isopropyl alcohol on the normal flora of hands

A gloved-hand wash method was used to compare the antimicrobial effect of chlorhexidine gluconate alcohol emollient hand wash (HIBISTAT) with that of 70% isopropyl alcohol on the normal flora of the hands (81 subjects) under conditions designed to mimic use by surgeons. Results of the immediate postwash effects on the bacterial counts for all 3 tests days showed that chlorhexidine significantly reduced the normal flora of the hands. When compared with the base line bacterial counts, there was 85, 96, and 98% reduction with chlorhexidine treatment and 84, 93, and 90% reduction with alcohol treatment on days 1,2, and 5, respectively. The difference between chlorhexidine and alcohol treatments was not statistically significant on days 1 and 2, but was significant on day 5 (P less than 0.01). For delayed postwash bacterial counts (for persistent antimicrobial effects), the overall log means were 4.9943 and 5.4684 for chlorhexidine and alcohol treatments, respectively. The difference between the two treatments was significant (P less than 0.01). After the chlorhexidien treatment, there was no significant growth of bacteria over a period of 6 h when compared with the base line bacterial counts.

Disinfection of the skin of the abdomen

The skin of the abdomen of 106 staff and 358 patients was sampled 5 min and 2 h after disinfection using contact plates. Control areas of skin were treated with water only or left untreated. A reduction of 99 per cent (log reduction factor = 2) or more in colony counts was obtained in 5 min with 70 per cent ethyl alcohol and alcoholic solutions of chlorhexidine, povidone-iodine and chloroxylenol/EDTA. Aqueous solutions of chlorhexidine (0.5 per cent) Savlon (5 per cent), povidone-iodine (10 per cent) and chloroxylenol/EDTA (X10 recommended concentration) also showed similar reductions. Weaker aqueous solutions of chlorhexidine (0.05 per cent), Savlon (1 per cent) and chloroxylenol/EDTA (recommended concentration) were significantly less effective than the alcoholic and the most effective aqueous solutions, although all were more effective than water. Total bacterial counts were lower from the skin of female than from male staff and lower from staff than from patients. Pathogens (Staphylococcus aureus or Gram-negative bacilli) were isolated from only one member of staff in small numbers and irregularly and rarely in large numbers from patients. Few pathogens were isolated after application of any of the disinfectants.

A test for 'hygienic' hand disinfection

A standardised test procedure is described in which finger-tips are inoculated with broth cultures of organisms (Staphylococcus aureus, Staphyloccocus saprophyticus, Escherichia coli, and Pseudomonas aeruginosa): counts are made from washings of hands after disinfection with various antiseptic-detergents, alcoholic solutions, or unmedicated soap. 70% alcohol, with or without chlorhexidine, was the most effective preparation. The two antiseptic detergents showed variable results, but against Gram-negative bacilli neither was significantly more effective than plain soap. Some tests were also made on the death rate of organisms dried on the skin without disinfection.

Failure of hand disinfection with frequent hand washing: a need for prolonged field studies

In a prolonged field trial a 4% chlorhexidine digluconate detergent scrub (Hibiscrub(R)), that had earlier proved to be an effective hand disinfectant, was studied in hospital wards. Finger tips were found to harbour more bacteria than the hand dorsum and the samples collected from them yielded more information on the bacteriological and dermatological effects of hand disinfectants in practice.In wards with a relatively low hand-washing frequency (less than 20 times in 8 hours) the bacteriological results resembled those obtained by in-use tests with volunteers. In the neonatal unit where the hand washing frequency was remarkably high, even occasionally over 100 times/8 h shift, an increase in the bacterial colony counts of the majority of the staff was recorded both before and after hand washing already after using the preparation for 1 week. Age, occupation and hand-washing frequency all correlated with the bacteriological results. Twenty-seven out of 37 persons complained of side effects such as wounds of finger tips and redness or heavy drying of the skin. Wounds, particularly on finger tips, resulted in the failure of disinfection. An increase in bacterial counts was sometimes noted without any dermatological or subjective changes. Drying of the skin was complained of less often when no increase in skin bacteria occurred.After the changeover of washing practice to a detergent followed by a rinse with spirit solution containing chlorhexidine and glycerol a decrease was recorded in the bacterial counts. It is concluded that more attention should be paid to long-term testing of hand washing and disinfection methods to ensure optimum final results in practice. It is obvious that the knowledge obtained from short time in-use testing cannot be applied to all conditions of use.

Micropunctures of rubber gloves used in oral surgery

In 720 operations in ambulatory oral surgery, the 2,880 surgical rubber gloves used were tested at the end of operation for perforations not earlier detected (microperforations). Gloves of ordinary thickness (type A) and of a thicker quality (type B) were examined. Perforations were found in 1495% and 22.0% of type A gloves and in 3.2% and 2.0% of type B gloves when oral surgeons and dental students, respectively, were operators. Gloves worn by operation assistants showed a lower incidence of perforation. Before operation, 50 gloves of type A were punctured at the tip of right index finger by a sterile dental probe. Results of bacteriologic examinations of the right index and middle fingers strongly indicated that a high number of bacteria passed through pinholes in the gloves. The intact surgical glove represents an impermeable barrier, protecting not only the operation wound against skin bacteria from the hands of the oral surgeon, but also the oral surgeon against pathogenic microorganisms, in particular hepatitis virus type B, escaping from the oral cavity of the patient.

Significance of the isolation of Clostridium welchii from routine blood cultures

Clostridium welchii has been demonstrated in approximately 20% of contact plates taken from the antecubital fossa of 185 inpatients and outpatients and healthy staff. The highest incidence was in a group of 40 very ill patients. The isolation of the organism from blood cultures is not always of clinical significance. Skin preparation as at present practised is often inadequate to remove the spores when contamination is relatively heavy, for example, in bedridden patients.

An evaluation of antiseptics used for hand disinfection in wards

The antibacterial effectiveness of hand antiseptics commonly used in wards was studied by laboratory and in-use tests and their acceptability assessed by means of a questionnaire passed to hospital staff. To determine the immediate and long-term antibacterial effects of the preparations the in-use tests were performed by groups of students. The greatest immediate reduction in bacterial counts on hands was obtained by products containing chlorhexidine. The long-term antibacterial effect was recorded with emulsions containing 3% hexachlorophane, 2% Irgasan CF3R or 4% chlorhexidine when used constantly on several consecutive days. Considerable discrepancies were recorded in the antibacterial effectiveness of some preparations when comparing laboratory and in-use test results. Therefore it is suggested that antiseptics should be tested by in-use tests which more closely resemble practical conditions before their use, or further trial, in hospital.

Anaerobic and aerobic skin bacteria before and after skin-disinfection with chlorhexidine: an experimental study in volunteers

The amount, composition, and localization of anaerobic and aerobic bacteria in the normal skin before and after disinfection were the subject of a volunteer study. The superficial bacterial flora were sampled by velvet pad imprints, and the deep flora were determined from whole skin biopsies. Only one anaerobic species, Propionebacterium acnes, was encountered even though other and more strict anaerobic bacteria could have been grown with the anaerobic technique employed. Staphylococcus albus dominated among the aerobic superficial bacteria, while diphtheroids, Micrococcus spp., and lactobacilli occurred sporadically. The deep aerobic bacteria were present in a significantly greater amount than the anaerobic. A two-step cleansing/disinfection procedure was evaluated in vivo in volunteers as well as in surgical patients, and aqueous cetrimide/chlorhexidine (Savlon) followed by chlorhexidine in alcohol (Hibitane) almost eradicated both the superficial and deep anaerobic and aerobic skin flora.

Preoperative disinfection of surgeons' hands: use of alcoholic solutions and effects of gloves on skin flora

A single application of about 10 ml of 95% alcoholic chlorhexidine (0.5%) or tetrabrom-o-methyl phenol (0.1%) rubbed on to the hands until they were dry led to mean reduction in viable bacterial counts from standard handwashings of 97.9 +/- 1.09% and 91.8 +/- 4.63% respectively. After six of such treatments, three on each of two successive days, the mean reductions in relation to viable counts before the first treatment were 99.7 +/- 0.09% for alcoholic chlorhexidine and 99.5 +/- 0.17% for tetrabrom-o-methyl phenol. These reductions were greater than those obtained with 4% chlorhexidine detergent solution- 87.1 +/- 3.5% and 98.2 +/- 1.6%, and with 95% or 70% ethyl alcohol and with aqueous 0.5% chlorhexidine. Preoperative washing of the surgeon's hands with alcoholic chlorhexidine used without addition of water is more effective and less expensive than handwashing with antiseptic detergent preparations and running water.The viable counts of washings from hands treated with various antiseptics, including ethyl alcohol, were lower in relation to the pretreatment levels when gloves had been worn for three hours than when samples for counts were taken immediately after the antiseptic treatment. No such difference was found in samplings from hands washed with unmedicated soap.Tests for residual action of antiseptics on the skin showed a greater effect with alcoholic chlorhexidine than with tetrabrom-o-methyl phenol, though both showed greater residual activity than an Irgasan DP 300 detergent preparation. No residual action was shown after 70% ethyl alcohol.

Disinfection of the skin with detergent preparations of Irgasan DP 300 and other antiseptics

An evaluation of the relative effectiveness of 2% hexachlorophane and 0.75% Irgasan DP 300 bar soaps in disinfection of the hands showed that the former caused a significantly larger reduction in natural skin bacteria than the latter after one handwash and after six handwashings, three on each of two successive days. Repeated use of Irgasan DP 300 bar soap caused a significantly greater reduction in skin flora than repeated handwashings with unmedicated bar soap, but a single handwash gave no significant reduction in skin flora compared with a single use of the unmedicated soap.In a comparison of a 4% chlorhexidine detergent solution a 3% hexachlorophane detergent cream and a 2% Irgasan DP 300 detergent solution the 4% chlorhexidine detergent gave the largest mean reduction in skin bacteria after one handwash and after six handwashings and 2% Irgasan DP 300 a poor and erratic reduction after a single handwash. After six handwashings all three preparations gave large reductions in skin bacteria. The 2% Irgasan preparation showed some residual activity on the skin after handwashing though less than that with chlorhexidine and with hexachlorophane-chlorocresol detergent preparations.

The effect of blood on disinfection of surgeons' hands

The effect on skin flora of spreading 2 ml of blood over the hands after a 2-minute disinfectant handwash and then wearing rubber gloves for an hour was assessed by a trial in which 6 volunteers used each of six preparations, once with blood and once, as a control experiment, with water on their hands. Bacterial counts of handwashings and of glove washings showed significant interference by blood with the effectiveness of povidone iodine detergent solution (Disadine). With a 3 per cent hexachlorophane detergent cream (Disfex) significant interference by blood was shown in bacterial counts of glove washings and a nearly significant interference was shown in counts of handwashings. There was no evidence of any interference by blood with the effectiveness of a 4 per cent chlorhexidine detergent solution (Hibiscrub) or a 3 per cent hexachlorophane liquid soap containing 0.3 per cent chlorocresol (Ster-Zac).

Hand carriage of gram-negative bacilli and Staphylococcus aureus

The influence of hexachlorophane disinfection on the bacterial hand flora of hospital personnel has been examined. Hexachlorophane effectively reduced the total number of bacteria and the staphylococcal carriage. Gram-negative bacilli were isolated from 18.8% of the personnel, and 13% of the carriers continued to carry Gram-negative bacilli for more than six months. The carrier rate was significantly higher among those using hexachlorophane detergents (20.8%) than among those using plain soap (14.1%). Prolonged hand carriage of Gram-negative bacilli was often associated with skin irritation, especially of the nailfolds. Hand carriage may be an important source of Gram-negative infections in hospital, and the increase in these infections may partly be due to extensive use of hexachlorophane preparations.

Use of 4 per cent chlorhexidine detergent solution (Hibiscrub) and other methods of skin disinfection

In a comparison of three antiseptic detergent preparations for hand washing, Hibiscrub, a 4% chlorhexidine detergent solution, caused a significantly greater estimated immediate reduction of skin flora (86.7% +/- 3.0) than was obtained with Dermofax, a 0.75% chlorhexidine detergent solution (55.5% +/- 5.1), or with Disadine scrub, a povidone iodine detergent preparation (68% +/- 6.8). After six applications the mean estimated reductions of skin flora were 99.2% +/- 0.2 for Hibiscrub, 97.7% +/- 0.7 for povidone iodine, and 91.8% +/- 1.6 for Dermofax.After a series of hand washings with Hibiscrub, as with a hexachlorophane detergent preparation, a further large reduction of skin flora, shown by bacterial counts of hand sampling, was obtained by a second phase of disinfection consisting of two minutes' application on gauze swabs of 0.5% chlorhexidine digluconate in 70% ethanol; a further wash with Hibiscrub, in place of alcoholic chlorhexidine, for the second phase of disinfection caused an increase rather than a reduction in the yield of bacteria on skin sampling. Unlike this "two-phase" disinfection, the application for 30 minutes of compresses soaked in 10% aqueous povidone iodine or in 0.5% aqueous chlorhexidine digluconate did not cause a greater reduction in skin flora than that obtained by the conventional two minutes' application on gauze of 0.5% chlorhexidine in 70% ethanol.Chlorocresol (0.3%) liquid soap (the base used for Ster-Zac liquid hexachlorophane soap) caused a mean reduction of skin flora when used for hand washing of 29% after one application and 72% after six applications spread over two days. This formulation, though less active and more variable as a detergent skin antiseptic than chlorhexidine, hexachlorophane, or povidone iodine detergent preparations, is an inexpensive disinfectant soap which could be useful in catering establishments. Alcoholic cetrimide applied as for disinfection of an operation site caused a reduction of skin flora greater than that shown by aqueous cetrimide but comparable to that shown by 70% ethyl alcohol in previous experiments.

A quantitative method for investigating the bacteriology of skin: its application to burns

A technique is described for homogenizing biopsies of skin and determining their total viable bacterial content. The method has been carefully checked to ensure that homogenization did not alter the bacterial content of skin and the technique was shown to give reproducible results. The bacterial content of normal and burned human and guinea-pig skin has been determined. Possible applications of the method are discussed.