ABSTRACT
The occurrence and antibiotic resistant patterns of Listeria monocytogenes in salad vegetables collected from open markets in Ago-Iwoye, Ogun State was investigated using standard microbiological standards. Twenty five (25) samples were samples of salad vegetable which included 10 cucumber, 9 carrot and 6 cabbage was purchased from different locations. The total aerobic plate count, coliform count and listeria spp. count of the samples were done by spread plate method on Nutrient agar, MacConkey agar and Brilliance Listeria Agar respectively. The antimicrobial susceptibility of isolatds Listeria spp. to antibiotics was determined by the disk diffusion method on Mueller Hinton Agar.
The mean aerobic plate count obtained from the samples was 5.25 x 105 cfu/g and ranged from 3.4 x 105 cfu/g to 1.2 x 106 cfu/g. Also, mean total coliform count obtained from the samples was 5.72 and ranged from 3.0 x 105 cfu/g to 1.83 x 106 cfu/g. The mean count for total Listeria spp. was 6.57 and ranged from 3.0 x 101 cfu/g to 10.1 x 101 cfu/g.
A total of twenty two (22) Listeria spp. were recovered from the salad vegetables sampled. Listeria spp. Fourteen n=14 (6.3.6%) were positive for Listeria monocytogenes out of which eight n=8 (36.4%) were positive for Listeria spp. Prevalence of Listeria monocytogenes was significantly higher in cabbage (57.8%) than in cucumber 4(57.2%) while the percentage of Listeria monocytogenes isolates from carrots was 3(50%). A significant higher percentage was isolated in cabbage 7(57.8%) while 4(57.2%) was isolated in Cucumber. In the study, Listeria monocytogenes were highly susceptible to Gentamycin 20 (90.9%), Ampicillin 11(50%), Vancomycin 8(40%) and Amoxicillin 5 (22.7%). All of the Listeria monocytogenes were resistance to Oaxacillin 22(100%) and Trimethoprim 22(100%), followed by Amoxicillin 16(72.7%) and Vacomycin 12(54.5%). Resistance to Ampicillin was encountered in 7 (31.8%).
The study therefore shows that L. monocytogenes occur in salad vegetables sold in Ago-Iwoye, Nigeria, therefore, adequate precaution should be taken in preparing these vegetables for both human and animal consumption. Also, the antimicrobial resistance pattern shown by the isolates is an indication that adequate measure need be taken to regulate drug use in both humans and animals in order to minimize the risk of increasing antimicrobial resistance.
TABLE OF CONTENTS
CHAPTER ONE
1.1 Introduction
1.2 Objective of the Study
1.3 Significance of the Study
CHAPTER TWO: Literature Review
2.1 The Opportunistic Pathogen Listeria Monocytogenes
2.2 Occurrence of listeria monocytogenes in vegetables and ready to eat food
2.3 Illness Caused by Listeria Monocytogenes
2.4 Vegetable and Vegetable Salad
2.5 health-benefiting properties of fruits and vegetables
2.6 Contamination of Vegetables by Listeria Monocytogenes
2.6.1 Contamination of Listeria Monocytogenes in the Post-Harvest Environment
2.6.2 Contamination during Produce Distribution
2.6.3 Contamination in the Retail Environment
2.7 Recent Outbreaks of Listeriosis
2.8 Listeria Monocytogenes Sensitivity to Antibiotics
2.9 Isolation and Media used for Listeria Monocytogenes
CHAPTER THREE: Materials and Method
3.1 Sample Collection
3.2 Sterilization and Aseptic Techniques
3.3 Media and Reagent
3.4 Isolation of Listeria Monocytogenes
3.4.1 Sample Preparation
3.4.2 Aerobic Plate Count
3.4.3 Total Coliform Count
3.4.4 Selective Enrichment with Isolation
3.5 Identification of Listeria Monocytogenes Isolates
3.5.1 Morphological Characteristics
3.5.2 Microscopic Examination
3.5.3 Biochemical Tests
3.6 Antibiotic Susceptibility
3.7 Statistical Analysis
CHAPTER FOUR: Results
4.1 Total Aerobic Plate Count
4.2 Total Coliform Count
4.3 Total Listeria spp. Count
4.4 Identification Of Isolates
4.5 Occurrence of Listeria Monocytogenes
4.6 Antibiotics Susceptibility Pattern
CHAPTER FIVE
5.1 Discussion
5.2 Conclusion
References
