Abstract
Handwashing is an important process in controlling microorganism transmission and infectious diseases. The purpose of this experiment was to determine the effectiveness of different antibacterial hand cleaners (soap, alcohol hand sanitizer and ethanol soaked wipes) on killing bacteria. Hands were sampled without cleaning with antibacterial hand cleaner (control), and after cleaning with antibacterial soap, alcohol sanitizer, and ethanol soaked wipes. Samples were taken with a sterile cotton swab and inoculated on agar plates. Each experiment was done three times. Colonies were counted, mean values and standard deviation were calculated, and data was reported. Alcohol and sanitizer and ethanol soaked wipes showed the lowest colony count, which demonstrated that they were more effective. More than 90% of colony reduction was found when alcohol contained sanitizers were compared with control. On the other hand, antibacterial soap had a high number of colonies, being ineffective in killing bacteria. In conclusion, antibacterial soap is not effective in killing bacteria. Results suggested alcohol based sanitizers as better hand cleaners.
Introduction
Handwashing has been considered a measure of personal hygiene for many years. It is also important in reducing the transmission of pathogenic microorganisms, particularly in clinical and community settings (Aiello S137). Different substances have been used in this process, including regular soap, alcohol, chlorhexidine, hexachlorophene, iodine, and quaternary ammonium compounds. During routine hand washing, transient microflora on the skin is usually removed.
Soaps are detergents that possess a cleaning action. The simplest chemical forms of soaps are composed by salts of a base and long-chain fatty acids (Rutala and Weber 1). Detergents are surfactants, having a hydrophilic (that likes water) and hydrophobic (that likes oil) side molecule. They possess a cleaning action, removing dirt, soil and some organic substances. It is recognized that plain soaps do not have a strong antimicrobial activity, but can remove the transient flora (CDC). Antibacterial soaps, on the other hand, contain an additional ingredient with regards to regular soap. Although those ingredients are added with the idea of reducing the bacterial presence when they are used, antibacterial soaps are shown to not be more effective than regular soap. On the other hand, some research shows the possibility of an increase in antimicrobial resistance when antibacterial soaps are used (Aiello S137)
Alcohol is also used for hand cleaning. Alcohol based products, such as sanitizers, reduce the number of viable organisms. Usually those products contain 60% to 95% of ethanol or isopropanol (Rutala and Weber 1).
The purpose of this experiment was to determine the effectiveness of different antibacterial hand cleaners (soap, alcohol hand sanitizer and ethanol soaked wipes) on killing bacteria. The hypothesis was that hand cleaning with ethyl alcohol would be more effective killing bacteria on average.
Materials and Methods
Different materials, such as agar plates, sterile swabs, three hand cleaners (antibacterial soap, alcohol sanitizer, and ethanol soaked wipes), were used in this experiment.
Samples were taking from the hand using a sterile cotton swabs. The swab was run across the palm of the hand, the back of the hand, and between fingers. The swab was lightly rubbed in a zig zag path across all the surface of the agar plate. The plate was incubated at 37 ºC for 3 days and the colonies were counted and recorded. The same process was done for control, hands washed with antibacterial soap, alcohol hand sanitizer and ethanol soaked wipes.
A control plate was inoculated from a sample taken from the hand without washing with any of the antibacterial hand cleaner. Each hand sanitizer was tried 3 times. An average of colonies were determine and compared. Standard deviation was also calculated.
Results
SD: standard deviation.
A comparison between mean values in control, antibacterial soap, alcohol hand sanitizer, and ethanol soaked wipes is presented in figure 1.
Figure 1. Mean colonies of bacterial treated with soap, alcohol hand sanitizer and ethanol soaked wipes. Control is also presented.
Discussion
Health care associated infectious incidences are reduced using hand antisepsis (Boyce, 2002). This has been demonstrated after increasing of washing hand frequency. Antimicrobials can control microorganisms by either sterilizing or disinfecting. In the first case, all microorganisms are killed; in the second one, some microorganisms are killed and others are inhibited. Different factors influence microbial control, including type of agent, microbial population, concentration used, and time of contact between the microorganism and the antimicrobial component.
Variability in colony counts was found in all treatment, including control. Standard deviation was higher for antibacterial soap and control than ethanol and alcohol treatments. The presence of colonies in control demonstrated the presence of some bacteria in hands; furthermore, some mold colonies were observed on the agar plate. Normal bacteria flora is always present in hands. It can be resident or transient. Transient flora can be more easily to remove form the skin during hand cleaning (WHO 1).
The highest count of bacteria was found for antibacterial soap, demonstrating the inability of this antibacterial to kill bacteria. Its mean value was two times higher than the control, having mean values of 107 and 54 colonies, respectively. Ogawa, in a study measuring number of bacteria before and after hand washing concluded that handwashing with soap is not effective at killing bacteria (339). They suggested another type of disinfection in doctors and nurses before and after they get in contact with patients. It has been demonstrated that antibacterial soaps are no more effective than regular soap and they are not able to reduce the infection in many circumstances (Tyski 207). Some research has demonstrated that plain soap contains only some antibacterial activity and it was lower than antibacterial soap. This activity depends on soap concentration (Bhat 52).
Alcohol hand sanitizer showed a mean of 5 colonies (in the three trials, colony number was between 1 and 9). More than 90% reduction in colony number from control was found. This demonstrated the ability of the alcohol hand sanitizer to kill the bacteria present in the hand.
On the other hand, the best reduction was found with the ethanol soaked wipes. Only a mean of four colonies grew on agar plates, having more than 90% reduction when compared to the control. A reduction in the transient flora was demonstrated, since this is the bacterial flora which is easily removed when hands are cleaned (Boyce and Pittet 1).
Alcohol acts on bacteria by the denaturation of the proteins. Different alcohol concentrations are used. Absolute ethyl alcohol is not as effective as a mixture between alcohol and water, since proteins denature faster in presence of water. On the other hand, methyl alcohol is the weakest alcohol for bactericidal action. Concentrations between 30 and 90% of alcohol have been demonstrated to killed different bacteria strains in a short time, such as 10 seconds (Rutala and Weber 1).
In the case of alcohol base hand sanitizers, such as alcohol hand sanitizer and ethanol soaked wipes used in this experiment, the Food and Drug Administration (FDA) suggest a concentration of 60% to 95% for ethanol or isopropanol (Reynolds 527). It is important to determine the concentration of the hand sanitizer before using it.
The hypothesis was confirmed: hand cleaner with ethyl alcohol (ethanol) was more effective at killing bacteria. Differences were found between alcohol containing hand cleaners and antibacterial soap. Also, variances were shown when compared to the control.
Future experiments can point to determining the amount of bacteria before and after applying the sanitizer, in order to determine the reduction of the bacteria. In this experiment, different hands were used in each trial, so there can be a difference in bacteria flora in each hand. More experiments are also needed and can be done using people doing different jobs and evaluating if the bacterial hand cleaner reduces the bacterial flora in all of them. Determining the antimicrobial activity of hand sanitizers is important so as to know the effects of them in reducing the flora. In that way, a more effective control can be established to reduce pathogenic microorganisms on hands, and the transmission of infectious diseases.
Works cited
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Boyce, John and Didier Pittet. “Guideline for Hand Hygiene in Health-Care Settings”. MMWR 51 (2002): 1-44. Print.
Reynolds, Scott et al. “Hand Sanitizer Alert”. Emerging Infectious Diseases 12.3 (2006): 527-529. Print.
Rutala, William and David Weber. Guideline for Disinfection and Sterilization in Healthcare Facilities, CDC. Geneva. 2008. http://www.ced.gov/hicpac/Disinfection_Sterilization/6_0disinfection.html
Ogawa, Mizuhito et al. “A survey on contamination by microorganisms and the effect of handwashing by doctors and nurses at the UOEH Hospital”. Journal of UOEH 22.4 (2000): 339-349. Print.
Tyski, S. “Microbiological characteristics of selected liquid soaps for hands washing”. Medycina Doswiadczalna i Mikrobiologia 65.3 (2013): 207-226. Print.
World Health Organization. WHO Guidelines on Hand Hygiene in Health Care: First Global Patient Safety Challenge Clean Care Is Safer Care. Geneva. 2009.
