RESEARCH OUTPUT 10, 11: ACTUAL DATA ANALYSIS and DATA PRESENTATION

Adviser: Dr. I.A. Ilano

Submitted by: GROUP 9-A

Leader:

Holgado, Anna Victoria

Members:

Alcantara, Jan Christopher

Balandan, Patricia

Buenafe, Jonas Joaquin

Constantino, Erwin

Delos Santos, Kathrine Aira

Flores, Marie Felle

Hernandez, Kristeen Khae

Lopez, Edison

Date:

February 15, 2012

Topic: "A comparative study on the antibacterial activity of the peel extracts obtained from

Musa acuminata, Musa balbisiana, and Musa paradisiaca against Staphylococcus aureus”

I. INTRODUCTION

A. Research question

“Which species of banana peel extract has greater antibacterial activity against

Staphylococcus aureus?”

B. Research hypotheses

i. Working hypothesis

“The peel extracts obtained from the different species of banana have comparable

antibacterial activity against Staphylococcus aureus.”

ii. Null hypothesis

“The peel extracts obtained from the different species of banana do not have

antibacterial activity against Staphylococcus aureus.”

II. RESEARCH OBJECTIVES and RESEARCH DESIGN

A. General objective

To determine which species of banana peel extract has greater antibacterial activity

against Staphylococcus aureus.

B. Specific objectives

1. To measure the zones of inhibition of peel extracts obtained from Musa acuminata,

Musa balbisiana, and Musa paradisiaca using the disk diffusion method.

2. To establish the respective minimal inhibitory concentrations of peel extracts

obtained from Musa acuminata, Musa balbisiana, and Musa paradisiaca using broth

dilution test.

3. To establish the respective minimal bacteriocidal concentrations of peel extracts

obtained from Musa acuminata, Musa balbisiana, and Musa paradisiaca using broth

dilution test.

4. To compare the obtained zones of inhibition, minimal inhibitory concentrations, and

minimal bacteriocidal concentrations of the peel extracts against Staphylococcus

aureus.

C. Research design

The study will utilize an analytic experimental design, wherein the independent

variable under observation will be assigned particularly to a treatment group and will be

compared to a positive and negative control group. Figure 1 illustrates the design of the

study.

Figure 1: Schematic diagram of research design

Operational definition of variables

1. Independent variable

The antibacterial activity of the different species of banana peel extracts on the

growth of Staphylococcus aureus serves as the independent variable for the study.

“Antibacterial activity” refers to the capacity of an agent to kill or suppress the growth of

microorganisms, specifically bacteria.(1) This property may be further classified into two

mechanisms, bacteriostatic and bacteriocidal. Bacteriostatic activity results into the

inhibition of microbial growth within a certain period of time. Microbial growth may be

observed once environmental elements become suitable, or the microorganism has

gained resistance to counteract the stimulus presented by the agent.(1) On the other hand,

bacteriocidal activity results into the complete eradication of the species. In the study,

significant bacteriostatic activity of the different species of bananas will be observed

through disk diffusion method and broth dilution test.

Musa acuminata (locally known as lakatan), Musa balbisiana (saba), and Musa

paradisiaca (latundan) are considered as the most common group of species grown and

commonly sold in the province of Cavite. Because of their wide availability and easy

accessibility, these species will be chosen as samples for the study.

2. Dependent variable

The expected result from the study will be the inhibition of the growth of

Staphylococcus aureus on nutrient agar medium. Inhibition denotes a temporary cessation

in microbial growth processes. This implies that there are still possible chances for growth,

given that the environment becomes favorable once again for microorganism propagation.(18) Therefore, strict compliance with the incubation of disk diffusion plates within the

allotted time of 24 hours for the Staphylococci species should be observed so as to

achieve reliable results and prevent possible growth of the organism.(2)

Inhibition of growth will be determined qualitatively using the disk diffusion method,

as represented by zones of inhibition. Broth dilution test will also be employed to quantify

the degree of the antibacterial activity by determining the peel extract’s minimal inhibitory

concentration. The end point tube in the series of test tubes illustrates the absence of

microbial growth achieved with the least concentration of the peel extract. (1)(2) Aliquots

from the tube with the least amount of drug that showed no growth and the two tubes that

immediately precede it will be collected and inoculated in a nutrient agar medium using the

streak plating technique in determining the peel extracts’ respective minimal bacteriocidal

concetrations.

3. Confounding variables

Both the independent and dependent variables may face possible contamination

brought about by 1) their exposure to environmental factors, such as temperature and

foreign body contamination; 2) as well as their subjection to certain preparation and

storage techniques executed in the duration of the study. Contamination of the variables of

interest may significantly influence the accuracy and analysis of the results. (1)(2)(3)

III. RESULTS AND ANALYSIS

A. Format for data analysis

i. Descriptive statistics – The mean diameter obtained among the three

replicates will be calculated in measuring the central tendency of the zone of

inhibition produced by the peel extract. Measures of central tendency are

inappropriate for the values obtained in conducting MIC and MBC since these

tests are performed only once. Furthermore, the standard deviation will be

computed from the value gathered from the zone of inhibition. The final data will

then be reported as mean + standard deviation.

ii. Inferential statistics - One-way analysis of variance (ANOVA) will be used as

the test statistic since the study is dealing with more than two independent study

groups. This is based on the premise that each peel extract group’s effect will be

unique from the other as well as from the established control groups. One-way

ANOVA is helpful in determining the probability of observing a difference existing

among the means of several study groups at the same time, minimizes the

possibility of committing a type I error which may result from conducting multiple

t-tests.(4) The confidence interval for this study will be set at 95%, with the value

for α at 0.05. These values have been derived from previous studies on the

antibacterial activity of plant extracts.(5)

Table 1 shows the plan for data analysis that will be utilized in the study. The

objective is to compare the results of more than two independent groups. The mean

diameter of the zones of inhibition obtained from each species of banana peel that will be

compared is categorized under the ratio scale of measurement; therefore, the tool for data

analysis that will be used will be a type of parametric test, namely, one-way ANOVA.

Table 1. Plan for data analysis

Plan for Data Analysis

Variables Scale of measurement Descriptive? Inferential?

Independent variable - The antibacterial activity of the different species of banana peel extracts on the growth of Staphylococcus aureus

Ratio

Dependent variable - the inhibition of the growth of Staphylococcus aureus as measured by the zone of inhibition produced

Ratio

Variables are independently related to each other

ANOVA

B. Results

i. Descriptive statistics

The antibacterial activity of the peel extracts obtained from Musa acuminata, Musa

balbisiana, and Musa paradisiaca were initially determined using the disk diffusion

method. Each species were prepared in three concentrations (30 µg, 300 µg, and 3,000

µg) and were observed for their respective antibacterial activity as evidenced by the zones

of inhibition produced. However, paper disk diffusion results revealed absence of inhibition

in all species. Difficulty in replicating the methods from previous studies, wherein zones of

inhibition were seen, brought about the need to conduct trials in determining the

antibacterial activity of the peel extract. In each trial, the extract concentration used was

set at 3,000 µg. Several variables such as blending time, characteristics of the banana

peel (e.g. color and storage duration), and the extract storage temperature were

considered. Values for mean + standard deviation are then considered to be set at zero,

since the values gathered per trial are null.(6) Table 2 shows the measurements of the

zones of inhibition among the different banana species.

Table 2. Zone of inhibition (mm) of peel extracts of different banana species using

paper disk diffusion in different trials

TRIAL 1 TRIAL 2 TRIAL 3 TRIAL 4 TRIAL 5 TRIAL 6

Musa sapientum

0 0 0 0 0 0

Musa paradisiaca

0 0 0 0 0 0

Musa acuminata

0 0 0 0 0 0

ii. Inferential statistics

Since the values obtained were set at zero, replacing these on the F-ratio (i.e. statistic

used in utilizing ANOVA) would reveal that the p-value would progress towards a positive

infinity, implying that the value of statistical significance is within the non-rejection area of

the normal distribution curve.(7) A conclusion can then be made that there are no sufficient

evidences to reject that the peel extracts obtained from the different species of banana do

not have comparable antibacterial activity against Staphylococcus aureus, in favor of the

alternative hypothesis.

REFERENCES:

(1) Mahon, C.R., Lehman, D.C., and Manuselis, G. (2007). Textbook of Diagnostic Microbiology. Missouri: Saunders.

(2) Forbes, B.A., Sahm, D.F., and Weissfeld, A.S. (2007) Bailey and Scott’s Diagnostic Microbiology. Missouri: Elsevier.

(3) Department of Microbiology and Parasitology, DLS-HIS College of Medicine (2011). “Laboratory Manual on Microbiology and Parasitology”.

(4) “Analysis of Variance”. Retrieved from http://www.wikipedia.com(5) Mokbel, M.S. and Hashinaga, F. (2005). Antibacterial and antioxidant activities of banana (Musa AAA., cv.

Cavendish) fruits peel. American Journal of Biochemistry and Biotechnology, 3, 125-131.(6) MacMillan A., et al. (2007) “Basic statistics: mean, median, average, standard deviation, z-scores, and p-

value”. Retrieved from https://controls.engin.umich.edu(7) “What is the meaning of an F value less than 1 in one-way ANOVA?” Retrieved from

http://stats.statexchange.com