OCCURRENCE AND ANTIBIOTIC SUSCEPTIBILITY PATTERN OF STAPHYLOCOCCUS AUREUS PRESENT IN EXPOSED POWERED MILK SOLD IN UMUAHIA NORTH LOCAL GOVERNMENT AREA, ABIA STATE

ABSTRACT

This study was conducted to ascertain the occurrence and antibiotics susceptibility pattern of Staphylococcus aureus present in exposed powered milk. The research was carried out in Umuahia North local Government area, Abia State. A total of 160 exposed milk samples were collected such as Miksi, Cowbell and Dano milk were collected from four different market located in Umuahia North local Government Area. The samples were collected under aseptic precautions and were enriched in peptone water (PW) followed by direct plating on selective media (Mannitol Salt Agar). The presumptive Staphylococcus aureus isolates were identified by biochemical tests. Antibiogram pattern of Staphylococcus aureus to antimicrobial agents were evaluated by disk diffusion method. The analysis of the result showed that out of 160 samples of exposed powdered milk resulted in the isolation of 10 isolates (12.5%) of 100 milk samples. The staphylococcus aureus showed the highest sensitivity towards Cephalexin (100%), Co-trimoxazole (100%) Oxacillin (70%), streptomycin (60%) and ampicillin (60%). Results clearly suggested a possibility of potential public health threat of S. aureus resulting from contaminating of exposed powdered milk with pathogenic bacteria is mainly due to unhygienic processing handling and unhygienic environment.

TABLE OF CONTENT

Certification ii

Dedication iii

Acknowledgement iv

Table of content v

List of tables vi

Abstract vii

CHAPTER ONE

1.1 Introduction 1

1.2 Aim and Objectives of the study 3

CHAPTER TWO: LITERATURE REVIEW

2.1 Biology and Characteristics of S. aureus 4

2.2 The mechanisms of antibiotic resistance 7

2.3 Food contamination by S. aureus 8

2.4 Exposed powdered handling practices 11

2.5 Milk pasteurization as a preservation technique 13

CHAPTER THREE: MATERIALS AND METHODS

3.1 Study Area 17

3.1.1 Sample collection 17

3.1.2 Isolation and Identification of Staphylococcus aureus 17

3.1.3 Morphological characteristics 18

3.1.4 Biochemical examination 18

3.1.5 Antibiogram pattern of the isolated Staphylococcus aureus to  some antimicrobial

         agents 18

3.2 Biochemical tests 19

3.2.1 Identification of Staphylococcus aureus by catalase test 19

3.2.2 Identification of Staphylococcus aureus by coagulase test 19

3.2.3 Antimicrobial sensitivity test 20

3.2.4 Determination of products with the highest level of contamination 22

CHAPTER FOUR

Results

CHAPTER FIVE

5.1 Discussion          28

5.2 Conclusion          29

REFERENCES

LIST OF TABLES

Table 1: Recovery frequency of S.aureus from sample in various sampling

             location 24

Table 2.1: identification and characterization of Staphylococcus aureus

                isolate                                                                                                        25

Table 2.2. Morphological and culture characteristics of S.aureus                         26

Table 4: Antimicrobial Susceptibility pattern of S.aureus  isolated (n=10) from

               the exposed powered milk           27

CHAPTER ONE

1.1 Introduction

Staphylococcus aureus is Gram positive and spherical cocci of about (0.8-1.0 micron) in diameter appearing in grape like clusters. Staphylococcus aureus are aerobes and facultative anaerobes that thrive at an optimum temperature of 37º C while the temperature at which they are active ranges between 12- 44º C. They have an optimum pH of 7.5. They have been found to grow well on ordinary lab media forming a golden yellow color in agar (William et al., 2005).

Pathogenic microorganisms are introduced in milk products when raw milk used to process them is contaminated or by cross-contamination (Muriuki et al., 2011). In Nigeria, 86 % of milk is marketed raw and only 14 % is processed (Balaban N. et al., 2001). Raw milk can be 20-50 % cheaper than the formal and pasteurized milk on the market (SDP, 2004). Unprocessed milk is also sold in desired quantities which give the low income earners access since they can buy as little as they can afford (Balaban N. et al., 2001). Milk handling equipment is one of the most significant sources of microbial contamination in milk (Muriuki et al., 2011). If equipment is inadequately cleaned and milk residues are left on wet surfaces it will result in microbial growth which could contaminate the milk (Muriuki et al., 2011).

Staphylococcus aureus produce enterotoxins that are virulent factors responsible for food poisoning in humans. In essence, according to Julia et al., (1995) enterotoxins are basic proteins which are resistant to heat, acid and digestive enzymes. There are four immunologically distinct enterotoxins that are designated as enterotoxins A, B, C and D (Julia et al., 1995). The enterotoxins produced cannot be destroyed by exposure to 100˚C for 30 minutes, therefore posing a serious challenge to their elimination from the contaminated food and other edibles (William et al., 2005).

Enterotoxins consumed incubate under favorable conditions and after 4-6 hours, symptoms of infection appear such as nausea, dizziness, severe abdominal pains and cramps, loss of appetite, diarrhea and vomiting up to 24 hours. This period of incubation is of great significance since it differentiates food poisoning caused by Staphylococcus aureus to that caused by Salmonella infection which appear 24-48 hours after eating contaminated food.

Staphylococcus aureus is associated with most wound infections in man and animals and may localize in boils, tonsillitis, cancerous cells, infections in the mammary glands and infection of sinuses. It was previously thought that contaminated water was the only source of diarrhea, however, it is now understood that food contaminated with Staphylococcus aureus equally causes food poisoning. Risk factors include: eating food that was prepared by a person with a skin infection, eating food kept at room temperature, eating improperly prepared food, sharing the same food with someone who has symptoms of infections. Staphylococcus aureus is a formidable pathogen of humans and livestock (William et al., 2005).

The genetic plasticity of Staphylococcus aureus has facilitated the emergence of persistent and multidrug-resistant strains that have a major impact on human and animal health (Foster, 2004). There has been a high risk factor of about 60 % prevalence rate of Staphylococcus aureus infections as a result of their high resistance to antibiotics used and 39.5 % of the infections have their source from milk and milk products (Tacconeli et al., 2008).

Figures from the health information system in the Ministry of Health reveals that between 1997 and 1999, there were 6833 cases and 566 deaths were reported from food contamination (William H. et al., 2005). Foods that are most commonly involved in food-borne disease are meat and meat products, poultry, eggs, milk and milk products, sweetmeats and rice preparations (Tambekar et al., 2004).

Staphylococcus aureus are able to grow at low temperatures and therefore posing a serious threat. With the current high risk factor of about 32 % prevalence rate of Staphylococcus aureus infections, resistance to the commonly used antibiotics is also on the rise. In Nigeria, there exists limited information on prevalence of Staphylococcus aureus in raw milk while none has been documented on milk products. Susceptibility patterns of isolated from milk have also not been well documented. Currently, most of the milk sold by vendors and intermediaries within Umuahia North Local Government Area, Abia State is not widely monitored in informal markets. Milk and milk products in some outlets are put in shelves and crates where ambient conditions can favor microbial growth. In other shop outlets, exposed powdered milk are stored without any form of refrigeration. Veterinary and public health services historically have worked independently Staphylococcus aureus and lack of cooperation has contributed to inadequate attention to effective control of zoonoses. In addition to institutional constraints, there are capacity training and technical constraints (Schelling et al., 2007). This study attempted to fill this gaps by generating information that allows risk assessments to be conducted in informal markets and suggest possible drugs of choice in empirical treatment of Staphylococcus aureus infections.

1.2 Aim and Objectives of the study

To determine the occurrence and susceptibility patterns of Staphylococcus aureus isolated from exposed powdered milk supplied for consumption within Umuahia North.

i. To isolate Staphylococcus aureus in exposed powdered milk in Umuahia North.

ii. To determine antimicrobial susceptibility patterns of Staphylococcus aureus isolates.

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