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Diversity and Antibiogram of Microbial Contaminants Isolated From Foods: Current School News : Nigerian Education

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Diversity and Antibiogram of Microbial Contaminants Isolated From Foods Hawked in Nsukka Metropolis: Consideration for Public Health.


Hawked foods are cheap and easily accessible and have met the food needs of people in many cities and towns of developing countries. This study was aimed at ascertaining the diversity of microbial contaminants in foods hawked in Nsukka town.

Seven different food samples of cooked foods hawked in Nsukka were examined for the presence of bacterial and fungal contaminants using streak plate method on sterile nutrient agar plates and SDA plates respectively.

The foods included; pigeon pea with yam (ayarayaji), pigeon pea with maize (ayaraya oka), pigeon pea with cocoyam (achicha), bambara nut (okpa), rice and stew, maize meal (igbangwu) and maize meal (agidi jellof).

Eighteen species of bacteria were isolated and identified using microbiological and biochemical methods. These were Staphylococcus aureus (n = 1), Enterobacter aerogenes (n = 1), Shigella dysenteriae (n = 1), Bacillus spp. (n = 12) and Bacillus megaterium (n = 3). Ten species of fungi were also isolated and identified.

They include Candida spp. (n = 7) and Aspergillus spp. (3). The most predominant isolates were Bacillus spp. other Candida spp. All the bacterial isolates were sensitive to levofloxacin, gentamicin, erythromycin, amoxicillin, streptomycin and chloramphenicol.

Six isolates were resistant to ampiclox, followed by rifampicin (5), ciprofloxacin (4), and norfloxacin (1). Staphylococcus auerus., Enterobacter aerogenes other Shigella dysenteriae were sensitive to levofloxacin, ciprofloxacin, norfloxacin, gentamicin, amoxicillin, streptomycin, rifampicin, erythromycin, and chloramphenicol.

The fungal isolates were all sensitive to itraconazole. One of the fungal isolates was resistant to ketoconazole, four were resistant to fluconazole and five to griseofulvin.

Eighty percent of the isolates were resistant to nystatin. The multiple antibiotic resistance indices were low for all the antimicrobial agents used (antibacterial and antifungal). MAR indices of six of the fungal contaminants were high, indicating that the organisms have originated from environment where antibiotics were often used.

The Aspergillus species were examined using Polymerase Chain Reaction (PCR) for resistant gene MDR3 and CYP51. Result showed that the Aspergillus species had the resistant gene MDR3 in them.

The result of this study revealed that cooked foods hawked in Nsukka town are contaminated with both bacteria and fungi. These organisms showed sensitivity and resistance activities to the antimicrobial agent used.

Ready to eat foods hawked in Nsukka also harbor multidrug resistance food borne bacteria and fungi which might cause public health hazards if these antibiotics resistance organisms are transferred to human.


Certification i
Dedication iii
Acknowledgments iv
Lists of Tables v
Table of contents vi
Abstract ix


1.0 Introduction 1
1.1 Food items 3
1.1.1 Tomatoes 3
1.1.2 Pepper 4
1.1.3 Cucumber 4
1.1.4 Carrot 5
1.1.5 Yam 5
1.1.6 Bambara nut 6
1.1.7 Plantain 7
1.1.8 Pineapple 8
1.1.9 Cocoyam 9
1.1.10 Pigeon pea 9
1.1.11 Breadfruit 10
1.2 Microorganism associated with food items 11
1.2.1 Bacillus species 11
1.2.2 Streptococcus species 12
1.2.3 Vibro cholerae 13
1.2.4 Staphylococcus species 13
1.2.5 Aspergillus species 14
1.2.6 Salmonella species 14
1.2.7 Enterobacter species 15
1.2.8 Pseudomonas species 15
1.2.9 Campylobacter species 16
1.2.10 Fusarium species 16
1.2.11 Shigella species 16
1.2.12 Escherichia coli 17
1.3 Prevalence of Microorganism in Ready-to-Eat Foods 17
1.4 Isolation of Microorganism from Ready-to-Eat Foods 18
1.5 Antibiotics Susceptibility of Microbial Contaminants Isolated from Ready-to-Eat Foods 19
1.6 Polymerase Chain Reaction 20
1.6.1 Process of PCR 20 Denaturation 21 Annealing or hybridization 21 Extension 21
1.6.2 Analysis of PCR Product 21 Agarose gel electrophoresis 21 Principle of agarose gel electrophoresis 22
1.7 Purpose of the Study 22


2.0 Materials and Methods 23
2.1 Materials 23
2.1.1 Culture Media 23
2.1.2 Chemicals 23
2.1.3 Antibiotic Discs 23
2.1.4 Samples (Food Items) 23
2.1.5 Glasswares and Equipment24
2.1.6 Other Materials 24
2.2 Methods 24
2.2.1 Sample collection 24
2.2.2 Sample preparation 24
2.2.3 Subculturing and storage of microbial isolates 24
2.2.4 Identification and Characterization of Bacterial Isolate 24 Gram staining 25 Endospore staining 25 Catalase Test 25 Citrate Test 25 Oxidase test 26 Amylase Test / Starch Hydrolysis 26 Voges Proskeur Test 26 Sugar Fermentation 26 Motility Test 27
2.2.5 Characterization and Identification of Fungal Isolate 27
2.2.6 Susceptibility test for bacterial isolates 27
2.2.7 Suscepbility test for fungal isolates 27
2.2.8 Multiple Antibiotic Resistance Index (MARI) 28
2.2.9 Identification of resistant gene MDR3 in Aspergillus species 28


3.0 Results and Discussion 29
3.1 Results 29
3.1.1 Sample preparation, identification and characterization of isolates 29
3.1.2 Antibiotic susceptibility test 35
3.1.3 Identification of resistance gene, MDR3 45
3.2 Discussion 47

4.0 Conclusion and Recommendation 50
Reference 51
Appendix 81


Food plays a vital role in the rise and growth or the fall and decline of a nation. This is because of its effect on the health of the population. Hawked food plays an important role in meeting immediate or urgent food need of people in many cities and towns.

Thousands of people depend on hawked food daily. The foods are cheap and easily accessible (Tambekar et al., 2008).

Ready-to-eat food can be described as the state of food ready for immediate consumption at the point of sale (Eni et al., 2001).

It is also defined as food consumed ordinarily in the same state as that in which it is sold by food vendors, hawkers or at local market and does not include nut in the shell and whole, raw fruits, vegetables that are intended for peeling or washing before consumption (Eni et al., 2001).

It is a popular option for people “ on the go ”. However, they often come with a lot of risk. This is because ready-to-eat foods can be consumed at the point of sale without further cooking or preparation (Castro-Rosas et al., 2007).

Ready-to-eat food can be raw or cooked, hot or chilled and can be consumed without further heat treatment (Tsang, 2002). Different terms have been used to describe such ready-to-eat food. These include: ” convenient ”, ” ready ”, ” instant ” and ” fast ” foods.

A general observation of our society shows a social pattern characterized by increased mobility, large numbers of workers and less family-or-home centered activities.

This situation has resulted in more ready-to-eat foods taken outside home; thus, there is an increase in food vendor services (Musa and Akande, 2002).


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Abe, AS, Inuwa, B., Abbas, H., Sule, AM, Mohammed, HA and Gero, M. (2012). Identification and characterization of bacteria air pathogens for homes in Zaria metropolis. International Journal of Science and Technology 2(7): 443-445.

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