Data Collection of bacterial loads on mobile phones

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Chapter 1 – Introduction

Introduction:

On Earth today, there are more than a billion different types of living organisms present. Surprisingly, most of them we cannot see with the naked eye called the microorganisms. One of those are called the bacteria which are the largest and most influential microorganisms on human species. They are also one of the smallest organisms in the world. They are about 10-6 meters in length. However, bacteria come in a large variety of different shapes and sizes. This is called morphology of bacteria, which differentiates different bacteria species by their physical structure. The most common shapes of bacteria are rod-like (which are called bacillus), spherical (called coccus).

The bacteria are found in very large number on the human skin which is called the normal microbial flora, but most of the bacteria are harmless to the human body ([1]Bacteria such as someStaphylococcusspecies,Corynebacteriumspp.,Brevibacteriumspp andAcinetobacterlive on normal skin and cause no harm), but there are some harmful bacteria which can cause serious skin diseases and damages to the skin ([2]The most common bacteria to cause skin infections are staphylococcus aureus which causes school sores and streptococcus pyrogenes which causes cellulitis).

Mobile phones have become one of the most used device in the world today. In fact so, popular that it has become a need nowadays. We take the mobile phones wherever we go even in the bathrooms, in public areas while eating so, just imagine the amount of bacteria transfer from the mobile to the hand. There is a chance of getting infected especially for the people with a weak immune system. Though the bacteria can transfer to the mobile it cannot multiply on the mobile phone as there is no nutrient support for the bacteria.

I was fascinated by tiny living organisms ever since I was a child. As I grew up I also started using many electronic gadgets the most common one being the mobile phones. I was wondering that nowadays mobile phones have become the most needy and useful products which is used by almost everyone. Since, our skin harbors lots of bacteria there could be a transfer of bacteria from one to another. I wanted to find out whether possible contamination of mobile phones with bacteria. So, I have chosen this topic as I am curious to know the load of bacteria on the surface of mobile phones and whether they have any impact on our health.

Hypothesis:

I assume that the bacteria present on the skin get transferred to the surface of the phone, but it does not support the growth of the bacteria, but merely harbor them. I wanted to inoculate to verify the samples from the mobile phones into the nutrient medium. I predict that there are some bacterial colonies……. I wanted to choose two media which are Nutrient Agar (N.A) and Soy Tryptone agar (S.T). The soy tryptone agar is very rich in nutrient value as given in Table 1.1. I assumed that petri dishes with Soy Tryptone agar may have more number of colonies than Nutrient Agar. I also wanted to test 3 groups that is House-keeping staff, Students and Teachers. I predict that the group 3 which House-keeping staff will have more number of colonies because they continuously work in unhygienic areas with high bacterial surroundings and don’t have time to sanitize themselves.

Chapter 2 – Materials & Methods

Materials and Equipment used:

  • Autoclave (Citizen)
  • Hot air oven (SISCO)
  • Incubator (SISCO)
  • Laminar air flow cabinet (AIRCON)
  • Nutrient agar (Hi Media)
  • Soy tryptone agar (Hi Media)
  • Petri dishes (Borosil)
  • Conical flasks (Borosil)
  • Mobile phones
  • Absorbent cotton (Vimal)
  • Non-absorbent cotton (Vimal)
  • Sterile water
  • Aluminum foil (Super Wrap)
  • Sterile cotton swabs

Procedure of Sterilization of glass wares:

[3]Sterilization is the process which eliminates all types of microbial life, including transmissible agents such as fungi, bacteria, viruses, etc., present on any surface, present in fluid or in a biological culture media. When we are working on bacteria the place where we work should be in aseptic conditions i.e. is sterile. That is why a process such as sterilization should take place. It eliminates all living organisms in that particular area so, that work on bacteria can take place. Sterilization can be achieved by supplying heat, chemicals, high pressure and irradiation.[4]Sterilization inhibits or kills bacteria in various ways such as:

  • Damage to the cell wall or inhibition of cell-wall synthesis.
  • Alteration of the permeability of the cytoplasmic membrane
  • Alteration of the physical or chemical state of proteins and nucleic acids.
  • Inhibition of enzyme action
  • Inhibition of protein or nucleic acid synthesis.

There are mainly to types of heating:

  • Dry heat
  • Moist heat

Most of the bacteria are inhibited when exposed to dry heat for 1-2 hours at a temperature of 150oC.[5]

Dry heat is a process accomplished by conduction. That is where heat is absorbed by the exterior surface of an item. Normally, dry heat is achieved using a hot air oven. They are electrical devices used in sterilization. They were developed by Louis Pasteur. The oven uses dry heat to sterilize items. There is a thermostat which controls the temperature of the hot air oven. The hot air oven has a doubled walled insulation which keeps the heat in and proper circulation of it happens.

Moist heat is another process normally used for sterilization. The process is commonly achieved using an autoclave or pressure cooker. An autoclave is a device which used to sterilize equipment by subjecting them to high pressure saturated steam at around 1210C for 15-20 minutes. The time depends on the amount of load and the contents. It was invented by Charles Chamberland in the year 1879.

To work in a sterile conditions there is a common machine used which is called laminar flow cabinet. It is a carefully enclosed cabinet designed to prevent the contamination of biological samples. Air is drawn through a High-Efficiency Particulate Absorption (HEPA) filter and is blown in a very smooth, laminar flow towards the outside. The cabinet is usually made of stainless steel without any gaps or joints where spores and other organisms which risk contamination gets collected. Laminar flow cabinet also has a UV-C germicidal lamp which sterilizes the shell and contents when not in any use. While using the laminar flow cabinet it is a must to switch off the UV-C germicidal lamp and use as it will immediately cause sunburns and sometimes cataracts.

  • First take the required amount of glass wares and clean them in liquid detergent and let them dry thoroughly. Then they should be placed in the hot air oven at 180oC for 1 hour.
  • Then along with the petri dishes required amount of conical flasks with capacity of 250cm3 should be placed in the hot air oven at 180oC for 1 hour. This is to kill all the microorganisms present on the glass wares.

Procedure for making Nutrient agar:

Composition of Nutrient Agar:

Ingredients

Gms/litre

  • Agar 15.00
  • Peptic digest of animal tissue 5.00
  • Sodium Chloride 5.00
  • Beef Extract 1.50
  • Yeast Extract 1.50
  • First take 2.8 grams of nutrient agar with the help of an electronic balance. Then, add the agar to a 250ml conical flask. After that in a separate beaker pour accurately 100ml of distilled water.
  • Then add the distilled water to the conical flask with agar slowly, then mix the solution with the help of a glass rod until there is no residue left.
  • Then place the conical flask over a slow flame for 10 minutes. After that cover the conical flask’s opening with a nonabsorbent cotton. Ensure that the conical flask is air tight. Then cover the top of the conical flask with aluminum foil.
  • Then place the conical flask in an autoclave for 15 minutes at 15 psi. If the psi rises above 15 then the autoclave should be turned off then when it comes back to 14 psi the autoclave should again be switched on.
  • This will be repeated until 15 minutes is done.
  • Then the pressure must slowly be removed from the autoclave. After complete pressure is removed the lid can be opened and the conical flask can be taken out. Then the conical flask should be left out for 5 minutes. This is to bring the temperature between 60 -700C.

Procedure of preparing Soyabean Casein Digest Medium:

*Composition of Soyabean Casein Digest Medium:

Ingredients Gms/litre

  • Pancreatic digest or casein 17.00
  • Papaic digest or soyabean meal 3.00
  • Sodium Chloride 5.00
  • Dipotassium Hydrogen phosphate 2.50
  • Dextrose (Glucose) 2.50

*Final pH (at 25oC) 7.3 + 0.2

Table 1.1: composition of Soy Tryptone agar

  • First suspend 3.5 grams of Soyabean Casein Digest Medium in 150cm3 distilled water in a 250cm3 conical flask.
  • Then heat if necessary to dissolve the medium completely. After that, cover the flask with nonabsorbent cotton and wrap the opening of the flask with aluminum foil.
  • Then sterilize by autoclaving at 15lbs pressure (121oC) for 15 minutes.
  • Then mix well and dispense as required.

Procedure of sterilization of cotton buds and water:

  • First take 100cm3 of water in a 250cm3 conical flask and cover the flask with nonabsorbent cotton making the flask airtight.
  • Then cover the top of the flask with aluminum foil.
  • After that, take the required amount of cotton buds and place them in a beaker.
  • Then cover the beaker with aluminum foil and place it in an autoclave with the conical flask of water. These should be kept in the autoclave at 121oC, 15lbs and for 15 minutes.

Pouring of medium in the petri dishes:

  • First switch on the UV light in the laminar flow for 10 minutes. Then, switch on the motor and make sure to clean the surface with ethanol as it makes the surface sterile.
  • Then, if you don’t have a gas connection use a spirit lamp while pouring the medium in the petri plates.
  • Carefully pour the medium in the petri dish near the flame as to take precautions of contamination. Then, after pouring into the first plate immediately cover both the petri dish and the conical flask containing the medium.
  • Repeat this process for the required number of petri dishes and then let be left in the laminar air flow for the medium to solidify.

Procedure for taking swabs of mobile phones:

The mobile phones were taken from three different groups, the teachers, the students and the house-keeping staff from my school. From each group 20 mobiles were collected and marked and tagged in zipped bags as to get values of the particular mobile phone owner. A mix of smartphones and keypad mobiles were used and with the permission of the users.

  • First take the required amount of cotton swabs and place them in a beaker. After that place the beaker in the autoclave for 15 minutes. Along with 250ml of distilled water.
  • This is to sterilize the cotton swabs. Then take the cotton swab and dip it in the sterilized water so that while swiping against the screen bacteria can get stuck easily to the swab. Then with minimum pressure move the swab along the surface of the smartphone. This should be done in the laminar flow.
  • Then take the sterilized petri dish, open it near the flame and quickly swipe the cotton swab along the surface of the nutrient agar without breaking the gel.
  • The swiping should be done in a zigzag pattern. Then quickly close the lid of the petri dish and mark the date of inoculation and the smartphone serial number.
  • Then repeat this for the other group of smartphones and then label it. This should be repeated 5 times for each smartphone in each group to get an accurate result.

Chapter 3 - Results

Data Collection of bacterial loads on mobile phones:

TEACHERS:

S no.

No. of colonies

Types of colonies

-

-

Number

Shape

Colour

M1

Nil

Nil

Nil

nil

M2

14

2

2=round 2=line

white

M3

61

3

oval, line

white

M4

19

2

oval, line

white

M5

20

2

Round

white

M6

20

3

Round

grey

M7

8

2

Round

grey

M8

1

Line

grey

M9

1

1

Line

white

M10

1

1

Round

grey

Table 1.0: bacterial count in nutrient agar

S no.

No. of colonies

Types of colonies

-

-

Number

Shape

Colour

M1

Nil

Nil

nil

nil

M2

5

3

round

white

M3

1

1

round

white

M4

1

irregular

Grey

M5

12

2

round

white

M6

3

irregular

Grey

M7

1

1

round

White

M8

24

1

round

Grey

M9

2

1

round

White

M10

8

2

oval, line

White

Table 1.1: bacterial count in tryptone agar

HOUSE-KEEPING STAFF:

S no.

No. of colonies

Types of colonies

-

-

Number

Shape

Colour

M1

796

2

C & W

white

M2

129

3

irregular

grey

M3

107

2

1-rhiz, 3 round

M4

52

3

1rhiz

white

M5

210

2

round rod white

M6

110

3

2rhiz roun white

M7

328

1

1rh,2rou

white

M8

92

2

1rh,2rou

white

M9

Infinite

1

round

white

M10

102

2

1rh, 2rou

Table 1.0: bacterial count in nutrient agar

S no.

No. of colonies

Types of colonies

-

-

Number

Shape

Colour

M1

301

M2

200

4

round

White

M3

73

3

rhiz1

White

M4

Nil

nil

nil

Nil

M5

48

3

round

White

M6

6

1

round

White

M7

25

2

round

White

M8

456

2

round

White

M9

512

1

round

White

M10

Table 1.1: bacterial count in tryptone agar

STUDENTS:

S no.

No. of colonies

Types of colonies

-

-

Number

Shape

Colour

M1

7

2

1C, 1I

white

M2

77

1

irregular

grey

M3

110

1

round

white

M4

8

3

2C&W,1r,

white

M5

Nil

nil

nil

nil

Table 1.0: Bacterial count in Nutrient agar.

S no.

No. of colonies

Types of colonies

-

-

Number

Shape

Colour

M1

92

2

1r, 1ir

white

M2

Infinite

2

1r, 1ir

white

M3

120

3

1line, 1ir,

white

M4

64

1

1ir

grey

M5

3

2

1C&W, 1r

white

Table 1.1: bacterial count in tryptone agar

Observation of bacterial colonies on mobile phones of Teacher’s:

  • The number of colonies in the nutrient agar is more than the colonies in the tryptone agar so, nutrient agar seems to be a better nutrient medium for bacteria than the medium of tryptone agar.
  • The bacteria found on the mobile phones are mostly harmless. Those of which are present on the skin. There are only possibilities of having skin acnes.

Observation of bacterial colonies on mobile phones of House-keeping staff’s:

  • Most of the bacteria were harmless but there were lot of colonies formed on both the mediums. There were on petri plates which had some different results with yellow colonies.

Picture 1.0: Bacterial colonies from mobiles phones of house-keeping staff with yellow colonies.

Chapter 4 - Conclusion


[1] http://dermnetnz.org/bacterial/

[2] http://dermnetnz.org/bacterial/

[3] http://en.wikipedia.org/wiki/Sterilization_(microbiology)

[4] Microbiology (Michael J. Pelczar, JR.), (E.C.S. Chan), (Noel R. Krieg)

[5] http://en.wikipedia.org/wiki/Sterilization_(microbiology)

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