Excerpt from Lab Report from Class
Antimicrobial Efficacy of Personal Use Cleaners at
Inhibiting Bacterial Growth of E. coli DH5α
Abstract
Although personal use cleaners are vital to preventing bacterial infections and diseases,
minimal research has been conducted on their antimicrobial efficacy due to manufacturing
companies primarily researching and advertising their cosmetic effects (Fulton, n.d.). This study
used the Kirby Bauer Disk Diffusion test to evaluate and compare the efficacy at inhibiting E.
coli DH5α bacterial growth of three popular personal use cleaners: Olay Ultra Moisture Shea
Butter Body Wash, the Neutrogena Benzoyl Peroxide Clear Pore Facial Cleanser, and the Bath &
Body Works “Ocean” 3 in 1 Hair, Face & Body Wash. Although no significant difference was
found between the treatments, the Olay Body Wash showed the highest inhibition of bacterial
growth. In addition, the positive control showed no antimicrobial effects compared to the
negative control, suggesting that this study is invalid. Analysis of each cleaner’s active
ingredients indicated that the presence of more surfactants corresponds to stronger antimicrobial
activity. The data also demonstrated that dilution and extended drying time can reduce the
potency of cleaners. Further research is needed to understand the antimicrobial effects of
different combinations and concentrations of active ingredients on different bacterial strains.
Introduction
Bacteria and viruses are single-celled microorganisms that can cause various infectious
and deadly diseases around the world (Physiopedia, n.d.). These microorganisms can be found in
all environments and ecosystems, including on common surfaces such as floors, tables, dishes,
door knobs, clothes and the human body, making them a major public health concern
(Physiopedia, n.d.). Antimicrobial agents are substances that kill pathogenic microorganisms or
inhibit their growth or reproduction (Pirmoradian & Hooshmand, 2019). Since they can prevent
the transmission of disease-causing bacteria and viruses to humans, antimicrobials are used for
disinfection in homes, hospitals, and other public spaces in the form of laundry detergents, dish
soap, bathroom cleaners, and body and face products (Levi, 2001). Popular disinfectants include
bleach and ethanol, as well as products from companies such as Lysol, Gain, Clorox and Windex.
Brands with antimicrobial products make many advertising claims about their efficacy in
Excerpt from Lab Report from Class
removing or cleaning germs, such as Lysol and Clorox’s claims of killing 99.99% of bacteria and
viruses (Ticsay, 2017). Antimicrobials are made with different combinations of active ingredients
called surfactants, which work by reducing the surface tension of liquids to allow them to spread
and help lift dirt off surfaces (International Products Corporation, 2022). Examples of surfactants
include alkyl sulfates, alkyl ammonium chlorides, sodium sulfates, benzoyl peroxide, and
cocamidopropyl betaine among others (International Products Corporation, 2022).
The skin serves as a physical barrier against foreign microbes and toxic substances that
cause diseases such as respiratory infections, skin infections, and wound infections. A person’s
skin accumulates oil and dirt throughout the day, and it can host more than 1,000 species of
bacteria (Eisenstein, 2020). Due to their effect on physical appearance, personal use cleaners
often focus on issues such as moisturizing and relieving dryness, irritation, acne, and
discoloration (Fulton, n. d.). Some research has found these antimicrobial products have
health-related effects on the composition of skin microbial communities (Yu et. al., 2018).
However, the study of personal use cleaners’ antimicrobial activity and comparisons between
different products is still lacking. To assess the antimicrobial activity of different personal use
cleaners and determine which is the most effective at inhibiting bacterial growth, the effects on
bacterial growth inhibition of three personal use cleaners were studied: Olay Ultra Moisture Shea
Butter Body Wash, the Neutrogena Benzoyl Peroxide Clear Pore Facial Cleanser, and the Bath &
Body Works “Ocean” 3 in 1 Hair, Face & Body Wash.
All three personal use cleaners had different active ingredients. The Olay Body Wash’s
main active ingredients were sodium trideceth sulfate and cocamidopropyl betaine (Incidecoder,
n.d.). The Bath & Body Works “Ocean” Body Wash had lauramidopropyl betaine and
methylisothiazolinone (Bath & Bodyworks, n.d.). The active ingredients of Olay and “Ocean”
interfere with and break up lipids and proteins in cell membranes to kill bacteria (Ahmed, 2020).
The Neutrogena Face Wash had benzoyl peroxide, which is an oxidizing agent of bacterial
proteins (Neutrogena, n.d.). Oxidizing agents work by taking away electrons from the cell
membranes and internal cell components of microorganisms, resulting in a loss of structure, cell
lysis, and apoptosis (Legionella Control Systems, n.d.; Finnegan et. al., 2010).
This study uses the Kirby Bauer Disk Diffusion Susceptibility Test to investigate the
hypothesis that the Neutrogena Face Wash would inhibit most bacterial growth of Escherichia
coli (E. coli) DH5α. E. coli DH5α was used to model bacteria on the skin because it is a popular
Excerpt from Lab Report from Class
strain for lab use and easy to work with due to their rapid growth under proper culture conditions
(Cooper, 2000). We compared three experimental groups treated with the three cleaners to a
negative control group treated with distilled water and a positive control group treated with a 3%
bleach solution. Bacterial inhibition was compared by measuring the zones of inhibition around
each treatment disk. Our data indicate that Olay Body Wash was most effective at inhibiting
bacterial growth, disproving our hypothesis.
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