ABSTRACT
Occurrence of methicillin and vancomycin resistant Staphylococcus aureus in yoghurt products sold in Umuahia was investigated. Ten brands of yoghurts were analysed for Staphylococcus load, occurrence and antibiogram using multi-drug antibiotic disc technique. Results obtained shows that the population of Staphylococcus aureus in the yoghurts was in the range from 1.5 × 106 to 4.6 × 106 cfu/ml. Staphylococcus aureus was present in each of the test samples (100% occurrence) and their sensitivity to antibiotics varied. Against methicillin however, all the isolates were resistant (100% resistance) while 90% resistant was recorded against vancomycin. The reactions to the other drugs shows that the isolates were totally resistant to four of the test drugs including Oxacillin, Ceftazidime, Ceftriaxone, Erythromycin, Cloxacillin and Amoxycillin/Clavulanate while Gentamycin, Ofloxacin, Cefuroxime records 70%, 50%,30% and 10% sensitivity respectively. It was observed that they were variations in the levels of resistance and susceptibility of the Staphylococcus aureus isolates from the yoghurt to the test drug. It was concluded that the microbiological quality of the yoghurts was low and the Staphylococcus aureus isolated was multi-drug resistant which is of great public health importance.
TABLE OF CONTENTS
Title
Page i
Certification
ii
Dedication
iii
Acknowledgements iv
Table
of Contents v
List
of Tables vi
List
of Figures ix
Abstract
x
CHAPTER
ONE 1
1.0 Introduction 1
1.1 The Aim and Objectives of this Study are: 3
CHAPTER
TWO
2.0 Literature Review 4
2.1 Production of Yoghurt 4
2.2 Nutritional Facts 6
2.3 Contamination 11
2.4 Staphylococcus Aureus Infection 13
2.5
Food Poisoning 15
2.6 Treatment 16
2.7
Antibiotic 19
2.7.1
Different Classes of Antibiotics 19
2.7.2
Modes of Action of Antibiotics 20
2.8
Antibiotic Resistance 22
2.9 Mechanism
of Antibiotic Resistance 22
2.10 Methicilin-Resistant
Stapylococcus Aureus (MRSA) 24
2.10.1 Transmission of MRSA in humans 25
2.10.2 Transmission of MRSA through milk 25
2.10.3 Treatment of MRSA infection in humans 26
CHAPTER
THREE
3
0 MATERIALS AND METHODS 27
3.1
Sources of Materials 27
3.2
Sterilization 27
3.3
Experimental Design 27
3.3.1
Media preparation 28
3.3.2 Sample
preparation 28
3.4 Isolation
and Enumeration of Staphylococcus aureus 28
3.4.1
Characterization of Staphylococcus isolates 29
3.5
Gram Staining 29
3.6
Biochemical Cultural Characteristics 30
3.6.1 Catalase
test 30
3.6.2 Coagulase
test 30
3.7
Identification of Staphylococcus aureus 30
3.8 Antibiotic Susceptibility Test 31
CHAPTER FOUR
4.0 Results 32
CHAPTER
FIVE
5.0 Discussion 40
5.1 Conclusion 41
5.2 Recommendations 42
References 43
LIST
OF TABLES
Table
Title
Page
1: Mean count of Staphylococcus aureus from yoghurt
samples 34
2: Percentage occurrence of Staphylococcus aureus in yoghurt samples
35
3: Percentage occurrence of MRSA
isolated from yoghurt samples
36
4: Percentage occurrence of VRSA
isolated from yoghurt samples 37
5: Percentage susceptibility
pattern of the Staphylococcus aureus
isolates 38
6: Characterization and
identification of organisms 39
LIST OF FIGURE
Figure Title
Page
2.1: Production of different types of
Yoghurt 5
CHAPTER
ONE
1.0
INTRODUCTION
Yoghurt is a fermented milk product
obtained from the milk or the milk products by the lactic acid fermentation
through the action of Streptococcus salivarius subsp. Thermophilus,
Lactobacillus delbrueckii subsp. Bulgaricus (FAO/WHO, 1977). Yoghurt is a
functional food and the functional food includes probiotics, prebiotics and
synbiotics. Probiotics can be defined as “Live
microbial feed supplements that beneficially affect the host animals by
improving its intestinal microbial balance”
(Champagne et al., 2005). Prebiotics
as “non-digestible
food ingredient that biennially affects the host by the selectively stimulating
the growth and/or activity of one or a limited number of bacteria in the colon”.
Synbiotic is a combination of probiotics that “beneficially
affects the host by improving the survival and the implantation of live
microbial dietary supplements in the gastro-intestinal tract by selectively
stimulating the growth and/or by activating the metabolism of one or a limited
number of health promoting bacteria”.
Studies approximate that 30-50% of the human population harbour Staphylococcus aureus on their bodies
(Sowash and Uhlemann, 2014). It can survive for hours on dry environmental
surfaces (Whitt and Salyers, 2002).
Staphylococcus
aureus is known to be notorious in their
acquisition of resistance to new drugs and continues to defy attempts at
medical control (Talaro and Talaro, 2002). Many strains of Staphylococcus aureus carry a wide variety of multi- drug
resistance genes on plasmids (Jawatz et
al., 1991; Graham et al., 2005;
Ikeagwu et al., 2008).
Methicillin-resistance Staphylococcus aureus (MRSA) strains are
considered to be resistant to all cephalosprins, cephems, beta lactam drugs
such as methicillin and oxacillin and other β
lactams (such as ampicillin-sulbactam), amoxicillin-clavulanic acid,
ticarcillin- clavulanic acid, piperacillin-tarzobactam and carbapenems
(Clinical and Laboratory Standards Institute, 2006). MRSA was first reported in
UK in 1961 after introduction of methicillin (Voss and Doebbeling, 1995).
MRSA infection and colonization have also
been reported in dairy cows, horses, dogs, cats, birds and cattle (Lee, 2003;
Duquette and Nuttal, 2004; Weese, 2005). Transmission of MRSA between animals
and humans have been reported (Simoons-Smit et
al.,2000; Manian,2003; O’Mahony
et al.,2005) as have the recovery of
human MRSA strains from contact with animals (Manian, 2003; Weese, 2005). Staphylococcus aureus has been detected
in milk and other food products locally obtained in Nigeria (Umoh, 1989; Umoh et al., 1990a; 1990b; 1990c). MRSA
colonization and infection in humans have been reported in several parts of
Nigeria including Abuja and Zaria (Ikeh, 2003; Taiwo et al., 2004; Onanuga et al.,
2006a; 2006b; Fusi et al., 2007;Olonitola
et al., 2007; Olowe et al., 2007). Fresh milk and its
fermented product like yoghurt constitute good media for microbial
multiplication (Jawatz et al., 1991)
and hence for transmission of milk borne diseases such as Staphylococcosis, Salmonellosis, Brucellosis and Tuberculosis
among others.
Poor sanitary practices have attributed to gross
contamination of food products such as milk and its products with Staphylococcus aureus . Milk has been
reported to be contaminated with MRSA which is suspected to have been acquired
from dairy animals or from post milking contamination (Umoh et al., 1990). Inadequate handling of milk up to the point
of pasteurization allows for the production of thermo stable toxins which
resist temperature as high as 1000C for 30 minutes (Virgin et al., 2009). Poorly pasteurized milk
could be a vehicle for zoonotic diseases and there is an inherent danger
associated with this product, so the mere touching of raw milk that harbours
the bacteria could result in an infection (www.
cdc /eid.org, 2008). Even fermentation process with the attendant drop in
pH may not rid the product of Staphylococcus.
Contamination of milk and its products during processing and distribution can
occur and this is a potential threat for the acquisition of Staphylococcus aureus including methicillin resistant strains by
those who handle foods, such as those who buy milk and its products, sellers of
the milk and dairy workers. Yoghurt deteriorates faster when stored at a higher
temperature than at a lower temperature (Hamann and Marth, 1984).
Commercially processed yoghurt is assumed
to be refined by the use of modern methods but quality control may be
compromised due to unsatisfactory storage conditions occasioned by epileptic
power supply and the mode of handling during distribution to the final
consumers by retailers.
1.1
AIM
AND OBJECTIVES
The aim and Objectives of this study are;
1.
To isolate and identify Staphylococcus
aureus in yoghurt
2.
To identify methicillin resistant Staphylococcus
aureus
3.
To identify Vancomycin resistant Staphylococcus
aureus
4.
To determine the antibiogram of the Staphylococcus
aureus isolates.
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