How to reduce bacterial infections at school?

Klapp Rebecca Meys Elise Project „Jonk Fuerscher“ 2015

Index 1. Introduction

page 3

1.1. Objective 1.2. Hypothesis

2. Method page 3-4 2.1. Material 2.2. Procedure

a) Microorganisms at different places at school b) Micrococcus bacteria on different materials

3. Results and Conclusions

page 4-8

a) Microorganisms at different places at school b) Micrococcus bacteria on different materials

4. Discussion

page 8

5. Abstract

page 9

6. Acknowledgments

page 9

7. Pictures

page 9

8. References

page 9

2

1. Introduction 1.1. Objective Our project’s objective was to identify potential sources of infection with microorganisms at school and to analyse bacteria’s survival on different materials, such as plastic, glass and different types of wood. Furthermore our aim was to contribute with the results of this study to a better hygiene in schools. 1.2. Hypothesis -

Microorganisms can be found on places touched by many people The lifetime of bacteria on wood is significantly lower than on plastics therefore furniture made of wood may potentially reduce bacterial spread among pupils at school

2. Method 2.1. Material Bacteria: Micrococcus Luteus Woods oak wood OSB (oriented strand board)

Desks melamin resin

Sterile materials

graduated pipettes (1ml) micropipettes (250µl) cuvettes culture flasks magnetic stirrer Drigalski spatula petri dishes cotton swabs Javel water water ethanol Bunsen burner Oil bath autoclave incubator

Others

Chairs polypropylene

Petri dish glass

Keyboard

Measuring instruments

spectrophotometer cuvettes heatable magnetic stirrer Temperature Gauge

LB-medium

5g/L Yeast Extract 5g/L Sodium chloride (NaCL) 10g/L Peptone (15 g/L Agar-Agar for solid LB agar plates)

2.2. Procedure a) Microorganisms at different places at school Firstly, we prepared liquid culture medium and agar plates for our microorganisms. Therefore we mixed 5g/L of Yeast Extract, 5g/L Sodium chloride (NaCl), 10g/L of Peptone with 1 L water for the liquid medium and for the agar plates we added 15g/L of Agar. Afterwards we autoclaved the medium to sterilise it.

3

Then we looked for places in our school, which could be contaminated with microorganisms due to frequent contact with humans like doors and door handles, desks, chairs, books in the school library, keyboards and computer mouse in computer sciences classrooms. On those specific places, we took samples with cotton swipes, which we put in Eppendorf tubes filled with 1ml of liquid growth medium. Afterwards we put 50l of this solution on Agar growth medium plates, which were kept for 5 days in the incubator at 38 °C.

b) Bacteria on different materials To begin we cultured Micrococcus Luteus in a round-bottom culture flask containing the bacteria, LB-medium and a magnetic stir bar by 37°C in an oil bath. We controlled this process every hour with the aid of a spectrophotometer to identify the moment where bacterial growth reached the exponential growth phase. When this phase was achieved, we did a 10-fold dilution in liquid medium (100µl micrococcus luteus culture + 900µl LB growth medium). We then applied 100l of the dilutions 10-3 to 10-11 on Agar growth medium plates, which were kept for 3 days at 38°C to determine the bacteria colonies. Afterwards we counted the number of bacterial colonies to identify the numbers of bacteria in our culture. In 100µl of the dilution 10-6 we counted 34 colonies. We added 100µl of the dilution 10-3 on every material in triplicates and waited 24 hours, so we have 34000 micrococcus bacteria on the different materials. All materials were previously disinfected either by heat in the incubator at 140°C for minimum 2 hours or using Javel and boiled water. After 24 hours we took samples with cotton swipes from the surfaces contaminated with micrococcus and transferred these in Eppendorf tubes filled 1ml of liquid culture medium. Then we added 50µl of the corresponding solutions on the Agar growth plates and kept them for 72 hours at 27°C in the incubator.

3. Results and conclusions a) Microorganisms at different places at school We determined our results with the help of a chart to analyse different types of bacteria. To give an overview of the specific places we summarized the bacterial contamination in the following table: The following table is categorized in these different classes: Total number of colonies 0-5 6-20 21-30 31-50 51-80 81-100 101+

Number of different types of microorganisms 0 1 2 3 4 5

Numbers of colonies per type of microorganism 0-5 6-10 11-20 21-40 40+

4

Place Negative control Desk

Total number of colonies

different types of microorganisms

0

0

126

3

90

4

8

3

9

4

2

2

2

2

27

3

84

5

Chair type 1

Chair lever

Computer keyboard type 1 Computer mouse type 1 Door handle Doorframe

Book

Number of colonies per type of microorganism 0 44 78 4 56 29 2 3 2 5 1 5 2 1 1 1 1 1 1 3 1 23 31 5 11 18 19

Computer keyboard type 2

62

3

40/12 6 4

Size (mm) / 2-3 1 4-3 2 1-2 7-10 25-45 2-3 1 4-3 4 4 4 4 7 8-12 1 3 1-3 4 1 0,5-1 2-3 3 1-3 1-3 1/ 2-10 1-5 3

Colour

Shape of the border and surface

Form

/ shiny yellow shiny white beige dull orange yellow white white clear yellow shiny white beige white yellow orange fair orange yellow brown/ black white yellow white yellow beige white yellow beige fair orange fair white, nearly invisible white yellow fair white, nearly invisible

/ curved out, clearly-defined, smooth smooth indistinct, brighter at the edge clearly-defined, curved out, smooth curved out, clearly-defined, smooth clearly-defined large broadening curved out, clearly-defined, smooth smooth indistinct, brighter at the edge curved out, clearly-defined, smooth curved out, clearly-defined, smooth curved out, clearly-defined, smooth curved out, clearly-defined, smooth curved out / curved out, clearly-defined, smooth curved out, clearly-defined, smooth curved out, clearly-defined, smooth curved out, clearly-defined, smooth / clearly-defined clearly-defined flow dawns clearly-defined clearly-defined

/ round round round round round oval, round oval lengthened round round round round round round round oval round round round round round round round round round round

clearly-defined, murky clearly-defined, murky large broadening

round round round

5

Computer mouse type 2 Toilet door handle Chair type 2

6

1

6

12

1

9

3

31

3

16 4 1 4 2 5 24

Dustbin lid

Banister

3 6

3

1 2

Door handle type 2

3 2 7

4

1 1

Glass door outside

2 13 25

4

9 1

Door handle outside

3

2

Doorframe type 2 6

3

1

white

clearly-defined

round

2-3 4-10 15 1 1-5 2 2 5

white yellow beige white yellow fair yellow white yellow

round round round round oval round round round

7

beige/ white

2-3

white/ yellow

10 3 10

fair beige, nearly invisible fair brown yellow

clearly-defined, smooth curved out, clearly-defined smooth, clearly-defined curved out, clearly-defined, smooth large broadening, curved out clearly-defined, shiny clearly-defined, shiny, smooth curved out, smooth, not clearly defined puckered, dull, clearly-defined, curved out curved inward, clearly-defined, slightly broadening flat, indistinct

round oval

3

white/yellow

10 1

white fair orange

1

fair yellow

8

beige

40

white, black, fair brown

2 4 3 3

white yellow white fair brown

clearly-defined, smooth, shiny curved out, indistinct, small colonies around, smooth, shiny curved out, white boarding, inside fair yellow, shiny curved out, clearly-defined, shiny flat, shiny, clearly-defined, sometimes orange border flat, shiny, clearly-defined, sometimes orange border lightly curved-out, clearly-defined, shiny three flows: inside black, in the middle white, outside fair brown, indistinct borders, puckered not clearly visible curved out, clearly-defined shiny, clearly-defined, curved out shiny, clearly-defined, curved out

2 1 1 3 2

round round oval

round oval/ round round round oval/round round

/ oval/round round round 6

The highest number of colonies has been counted on the school desk with a melamine resin surface with 126 colonies. The desk was followed by the chair out of polypropylene with 90 colonies. Moreover the book from the library has the third highest results with 87 colonies. The lowest contamination was on the computer mouse and the door handle with only 2 colonies. The door handle outside only possesses 3 colonies. The most different types of microorganisms have been found on the book form the library with 5 different types followed by the chair, the computer keyboard, the door handle and the glass door outside with 4 types. Only one type of microorganism could be determined on the computer mouse, the toilet door handle. The second computer mouse also only had 2 different types. Conclusion We identified significant differences in the extent of contamination with microorganisms at the different places which were analyzed. These differences may be explained by one (or a combination of) the following possibilities: -

Differences in the survival of microorganisms on different surfaces Differences in the frequency of cleaning of the different places/objects Differences in the frequency of contact with humans

For highly contaminated surfaces the frequency of cleaning may have to be increased to reduce contamination and potential infection of humans with the different germs. Alternatively some of the materials used for the furniture could be replaced by others to reduce microorganism’s lifetime.

b) Bacteria on different materials Numbers of bacterial colonies obtained from materials contaminated with approximately 34000 bacteria 24 hours after contamination.

Plastic

Material Computer keyboard

Chair (polypropylene) desk

Glass

Wood

oak wood

OSB (oriented strand board) Petri dish

number of bacteria colonies after 24 h 0 0 5 uncountable uncountable uncountable 50-100 50-100 50-100 2 0 0 0 0 uncountable 0 0 1

7

Conclusion: We conclude from these results, that bacterial survival was by far the highest on the plastic chair and the school desk. On the other materials, such as wood and glass, or the computer keyboard very few bacteria have survived. Therefore the use of different materials may have an impact on bacterial transmission.

0 Bacteria colonies on different materials

(from right to left: glass, desk, oak wood, char, computer keyboard, OSB)

4. Discussion Our hypotheses were proven right by our experiences. There were almost no microorganisms found on wood but mostly on plastic or books. Moreover, books from the library and keyboards, which are touched by many people, were more contaminated than the doorframe for example. Also our second experiment showed that the bacteria growth was important on plastic and much less on glass or on wood. Since we did not use negative controls in the second experiment we can however not fully exclude the possibility that bacterial contamination on desks and chairs were not only due to contamination with micrococcus, despite prior disinfection of the corresponding surface with Javel. Nonetheless, our results seem to suggest that desks and chairs out of wood might be more hygienic and could reduce the rate of bacterial infections in schools.

8

5. Abstract: Our project’s aim was to analyse bacterial survival on different types of materials like plastic, glass and wood to improve hygiene in schools or other public buildings. Our hypothesis were that bacteria will be soaked up by wood, which will reduce their ability to survive and that bacteria can be found mostly on placed touched by many people. Therefor we started our project by taking samples with cotton swipes in contaminated places in our school and added those germs on Agar growth medium plates, which stood for 5 days in an incubator by 38 degrees Celsius. Our results showed that most germs could be found on chairs, computer keyboards, outdoor doorframes, library books and dustbin lids. Next we analysed the survival of Micrococcus luteus on different materials (woods: oak wood, OSB (oriented strand board), desks; chairs; keyboards; glass). Our results showed that the bacteria’s survival was the highest on the chair and the desk out of plastic. On the other materials, only few colonies of bacteria grew on our Agar plates.

6. Acknowledgments First we would like to thank our tutor Jacques Kremer, who supported us during our whole project and helped to find answers to our questions. Also thanks to the “Service technique du ALR” especially to Benny Reuter who provided us with the material we needed for our experimentations. Other thanks go to the direction of our school ALR (Atert-Lycée-Redange), who made it possible for us to carry out the experiments of our project by giving us a lab and other needed informations.

7. Pictures

1 chair used for our experiment 2

2 Oak wood with 100 µl micrococcus solution

1

3 Chair contamination at school

8. References https://modmedmicrobes.wikispaces.com/Sarcina+Lutea http://www.genstrom.net/public/biology/microbiology/microbiology_module/protocols/protokoll_c .html

9