Dirty Car vs. Clean Car

Person #1 Person #2Person #3Person #4

National University

August 2, 2012

Hypothesis

The premise of this group project was to test the amount and type of bacteria found on

the outside and inside of a car, and to compare these microorganisms between a professionally

cleaned car, and one that has not been cleaned in two months. The surfaces that were tested

stayed consistent between the vehicles, and the one who owned and operated each was the same

as well. It was decided that the most commonly touched areas, and what was deemed as the

most unclean parts were chosen as the areas that would be examined; these areas within the car

were the steering wheel and air vents, while the ones chosen outside were the gas cap lid and

driver’s side door handle. This group’s hypothesis was that a professionally cleaned car would

culture far less bacteria in all areas than a non-cleaned car.

Methods

The process utilized inoculating two nutrient agar plates, each sectioned into four quadrants:

Quadrant one for the steering, quadrant two for the door handle, quadrant three was the air vent,

and quadrant four was the gas handle. The two plates were used as a separate growth plate for

each car. For this experiment, the group used distilled water as a method of moisturizing sterile

swabs prior to swiping a surface for bacteria. The swabs were done one at a time, with each

being used to inoculate the agar plates immediately after acquiring the bacterial samples from the

surface so as to reduce the collection of bacteria in the air.

Results

The bacteria cultures from the dirty car and the clean car were surprisingly different. The

dirty car had a total of eleven colonies from the steering wheel, air vent, door handle and gas

handle combined. The steering wheel of the dirty car had only one large, beige, circular, convex

colony 6 millimeters in size. The air vent of the dirty car had no growths after incubation. The

door handle had six colonies ranging from cream to white in color, a variety of appearances and

elevations and sizes ranging from 1 millimeter to 3 millimeters. The gas handle of the dirty car

had four colonies ranging from cream to brown in color, a variety of colony appearances and

elevations and the sizes ranged from 1 millimeter to 5 millimeters. The majority of identifiable

bacteria from the dirty car appeared to be gram positive cocci.

The clean car had a total of fifty two colonies from the steering wheel, air vent, door

handle and gas handle combined. The steering wheel had fourteen colonies ranging from cream

to yellow to light brown in color, all circular in appearance, convex to umbonate in elevation and

1 to 6 millimeters in size. Unlike the dirty car, the clean car’s air vent had seven colonies from

cream to yellow in color, various in appearances, margins and elevations and 1 to 2.6 millimeters

in size. The door handle of the clean car had seven colonies ranging from cream to orange in

color, a variety of appearances, margins, and elevations and sizes ranging from 1 millimeter to 5

millimeters. The gas handle of the clean car had twenty-three colonies ranging from cream to

yellow in color, a variety of colony appearances, margins and elevations and the sizes ranged

from 1 millimeter to 5 millimeters. After gram staining procedures and careful evaluation under

the microscope it was determined that the clean car had both gram positive cocci and gram

positive bacillus bacteria. There was also a development of mold on the clean car agar plate. The

mold or fungi was most noticeable under the microscope.

In conclusion, the clean car had forty one more bacterial colonies grown when incubated

compared to the dirty car. The largest colony from each of the cars measured six millimeters in

size and both of these large colonies originated from the steering wheels. The most abundant

growth of colonies from a single location came from the gas handle of the clean car. The clean

car’s gas handle had a total of twenty three colonies while the gas handle of the dirty car only

had four. Accounting for the size and quantities of all colonies we can conclude that the clean car

was actually more dirty than the dirty car.

Discussion

After examining the results, it was evident that a professionally cleaned car did not drastically

improve the amount of bacteria cultured. In fact, the air vent of the dirty car showed no bacterial

growth of any kind, which could be attributed to the fact that it has been stored outdoors while

the clean car is parked inside a garage; the exposure of heat from the sun could have limited the

growth of any microbial organisms. Also, it is unknown what types of cleaning products were

used, thus making the anti-microbial control undetermined as well. Another factor to consider as

uncontrollable is the usage of distilled water instead of sterile water. It is important to note that

both vehicles saw large amounts of bacteria, and in the case of the dirty cash, fungal growth, in

the samples taken from the gas caps. This can be attributed to the fact that his area of the car

does not regularly get cleaned even when taken to a car wash.

Research by Reuters (2012) and Geekosystem (2011) shows that regardless of a clean car

or a dirty car, the gas handle was the number one spot for bacterial colonies. In a study by

Kimberly-Clark (2012), measurements were taken of repeated swabs of commonly touched

objects and surfaces to determine the levels of adenosine triphosphate, which indicates the

presence of contamination by an animal, vegetable, bacteria, yeast and mold cells (Geekosystem

2011). Gas pump handles were among the dirtiest surfaces Americans touch. This new testing is

compelling because it underscores the importance of hand and surface hygiene (Livescience

2011).

Most cold and flu viruses are spread because people touch surfaces in their immediate area

and then touch their faces, other objects and other people (Wikepedia 2012). Washing and drying

your hands frequently throughout the day, can help prevent your risk of getting sick or spreading

illness (Wikipedia 2012).

In Hong Kong, environmental staphylococcal contamination was investigated by culturing

400 automated teller machines (ATMs). Isolates were characterized for antibiotic and antiseptic

susceptibility, carriage of antiseptic resistance genes (QAC genes), and spa types. MRSA, which

was similar to local clinical isolates, was present on two (0·5%) of the 62 (15·5%) ATMs that

yielded Staphylococcus aureus (Zhang et. al 2012).

Furthermore, handrails in 85 public urban buses were screened for the occurrence of

MRSA in Portugal between May 2009 and February 2010 where 22 (26%) of the buses showed

contamination (Simões et. al 2011). With bacterial contamination stemming from common

surfaces one must be cognizant of what they are touching. Public transportation and personal

cars are home to bacteria and even some fungal growth. Mold or fungal growth was also found in

the clean car’s, gas handle colonies.

Whether a car is professionally detailed or not has nothing to do with the amount of

microbes present on the surfaces. Research around various parts of the world provides insight to

harmful germs found in cars both seen and unseen to the naked eye. From a privately owned

vehicle to public transportation, germs are spread at a rapid rate with passengers unsuspecting of

these organisms since they are not visible.

In October 2011, Kimberly Clark released results of a study conducted in six United States

cities regarding breeding grounds for the worst bacteria and viruses. The study found that gas

pump handles were the filthiest surface that Americans encounter on the way to work (Reuters

2011). This study by Kimberly Clark is conclusive with the results of the Dirty Car vs. Clean Car

study in that the gas handles yielded higher colonies of bacteria and mold than the other surfaces

tested.

Research at the Queen Mary University in London, England (2011) revealed the steering

wheel of a vehicle harbors nine times more germs than a public toilet seat; 80 types of bacteria

lurk on each square inch of a toilet and 700 types inhabit the interior of the car (Dailymail 2011).

Among the types of bacteria found were Bacillus cereus which can cause food poisoning and

Arthrobacter, which is found in soil and on human skin. Dr. Ron Cutler, Director of Biomedical

Science at Queen Mary stated, “While most of the bacteria are unlikely to cause health problems,

some cars were found to play host to a number of potentially harmful bacterial species”

(Dailymail 2011).

NYTimes (2011) reported that Darleen Franklin, a supervisor at San Francisco

University’s biology lab, took specimens of a BART (Bay Area Regional Transit) train. Ms.

Franklin’s findings were fecal and skin born bacteria resistant to antibiotics. Further testing

indicated the presence of MRSA in the train’s cushioned seats (NYTtimes 2011). High

concentrations of bacteria and mold were found on the public transit system. These findings are

also conclusive to the Dirty Car vs. Clean Car study in that both bacteria and mold were present

on frequently touched surfaces.

References

Dailymail.co.uk. 2011. How clean is your car? Retrieved from http://www.dailymail.co.uk/news/article-1379830/How-clean-car-Steering-wheels-times-germs-public-toilet-seat.html on August 1, 2012.

Geekosystem.com. 2012. Gas pumps are Gross. Retrieved from http://www.geekosystem.com/gas-pumps-are-gross/ on July 30, 2012.

Nytimes.com. 2011. On BART trains, the seats are taken by bacteria. Retrieved from http://www.nytimes.com/2011/03/06/us/06bcseats.html?pagewanted=all on August 1, 2012.

Reuters.com. 2011. Gas pump handles top study of filthy surfaces. Retrieved from http://www.reuters.com/article/2011/10/25/us-usa-health-filth-idUSTRE79O0G820111025 on August 1, 2012.

Simões, R., Aires-de-Sousa, M., Conceição, T., Antunes, F., da Costa, P., & de Lencastre, H. (2011). High prevalence of EMRSA-15 in Portuguese public buses: a worrisome finding. Plus One, 6 (3), p 176-185.

Wikepidia.com. 2012. Bacteria. Retrieved from http://abcnews.go.com/Health/ColdandFluNews/story?id=5892245&page=1#.UBcG38W_yZw on July 30, 2012.

Zhang, M.M., O’Dononghue, M.M., & Boost, M.V. (2012). Characterization of staphylococci contaminating automated teller machines in Hong Kong. Epidemiology & Infection, 140 (8) p. 1366-67.