Assessment of microbial loads and antibiotic residues in milk supply in Khartoum State

82 Pages·2006·0.19 MB·English

ﻢﻴﺣﺮﻟﺍ ﻦﻤﺣﺮﻟﺍ ﷲﺍ ﻢﺴﺑ

Assessment of microbial loads and antibiotic residues
in milk supply in Khartoum State

By
Ammar Mohamed El-hassan Mohamed Said Ahmad
B.Sc. Honours Animal Production
University of Gezira
1999

A dissertation submitted in partial fulfilment for the requirements of the
Degree of Master of Dairy Production and Technology

Supervisor: Dr. Ibtisam El Yas Mohamed El Zubeir

Department of Dairy Production
Faculty of Animal Production
University of Khartoum
May 2006
ACKNOWLEDGEMENTS

All praise being to Allah, the almighty for his uncounted support.
Peace and blessing of Allah be on the soul of prophet and messenger,
Mohamed and his pious companions and followers.
I would like to thank and show may sincere gratitude to Dr. Ibtisam
El Yas Mohamed El Zubeir who supervised this work. I could not have
completed this study without her wise guidance, advice, friendship and
encouragement.
I am greatly indebted to Dr. Mohamed Khair Abd Allah and Mr.
Fath alrahman Abdalgalail for helping me in statistical analysis.
I appreciate the kind help offered to me by members of the
Department of dairy production, Faculty of Animal Production,
University of Khartoum.
Last but not least, I am really indebted to my beloved parents,
brothers and sisters, who without their generous and unlimited financial
and moral support it would have been impossible to achieve this present
work. And my thanks to every person who contributed directly or
indirectly and whose is not mentioned here.
Table of content
Page
Acknowledgements
Table of contents
Abstract I
Arabic abstract IV
Chapter one: Introduction 1
Chapter two: Literature review 3
3
2.1 Hygiene production of market milk
4
2.2 Milk marketing system in Sudan
2.3 Bacteriology of raw milk 5
2.3.1 Sources of microorganisms in milk 6
2.3.1.1 Microbial contamination from within the udder 7
2.3.1.2 Microbial contamination from the exterior of the udder 7
2.3.1.3 Microbial contamination during milk handling and storage 9
2.4 Bacterial load of raw milk 10
2.4.1 Total bacterial count 10
2.4.2 Coliform bacterial counts 11
2.4.3 Psychrotrophic bacterial counts 13
2.6. Antibiotics and antibiotics residues in milk 15
2.6.1 Definition of antibiotics 15
2.6.2 Source of antibiotics in milk
16
2.6.3 Antibiotic residues in milk
17
2.7 Problems caused by milk containing antibiotic residues
18
2.7.1 Public health risks
18
2.7.2 Economical and industrial problems
19
2.8. Methods of detecting antibiotics
20
2.8.1 Screening methods
21
2.8.1.1 Microbiological methods 21
2.8.1.2 Radioimmunological and enzyme techniques 22
2.8.2 Confirmation methods 23
2.9 Effect of heating on antibiotic residues in milk 23
Chapter three: Material and methods 25
3.1 Source of sample 25
3.2 Collection of the milk samples 25
3.3 Microbiological examination of milk 25
3.3.1 Cultured media used for microbial examinations 26
3.3.1.1 Solid medium 26
3.3.1.1.1 Plate count agar 26
3.3.1.1.2 Mac Conkey’s agar 26
3.3.1.1.3 Nutrient agar 26
3.3.1.2 Liquid medium 27
3.3.1.2.1 Nutrient broth
27
3.3.2 Sterilization
27
3.3.2.1 Sterilization of the equipment
27
3.3.2.2 Sterilization of distilled water
27
3.3.3 Preparation of serial dilutions
27
3.3.4 Bacterial counts
28
3.3.4.1 Total bacterial counts
28
3.3.4.2 Coliform counts
28
3.3.4.3 Psychrotrophic bacterial counts
28
3.3.5 Counting
28
3.4 Physiochemical properties of milk
28
3.4.1 Determination of the acidity
28
3.4.2 Temperature and pH
29
3.5 Detection of antibiotic residues in milk
29
3.5.1 Delvotest ® SP– ampule:
29
3.5.1.1 Equipment and supplies 29
3.5.1.2 Procedure 30
3.5.1.3 Interpretation of the results 30
3.5.2 Antibiotic residues detection using Modified one plate test 31
3.5.2.1 Equipment and supplies 31
3.5.2.2 Procedure 31
3.5.2.2.1 Test medium preparation 31
3.5.2.2.2 Antibiotic residues testing
32
3.5.3 Effect of heating on antibiotic residues in milk
32
3.6 Statistical analysis
32
Chapter four: Results
33
4.1 The hygienic quality of raw milk samples from Khartoum and 33
Khartoum North (Khartoum State):
4.1.1 Total bacterial count: 33
4.1.2 Coliform count:
33
4.1.3 Psycrotrophic count:
35
4.2 Comparison of some hygienic quality measurements between
35
different sampling points in Khartoum State:

4.3 Determination of some physical properties of milk samples
39
from Khartoum State:

4.3.1 Titratable acidity:
39
4.3.2 Temperature:
40
4.4 pH values:
43
4.5 Antibiotic residues of the milk samples collected from
43
different cities in Khartoum State:

4.6 Effect of heat treatment on antibiotic residues
44
Chapter five: Discussion
47
Conclusion 54
55
Recommendation 56
References
Abstract
This study was conducted to evaluate the quality of milk supplied
to consumers from two sources which include farms and sales points
in Khartoum State. Raw milk samples (72 samples) were collected
from Khartoum North (36 samples) and Khartoum (36 samples). All
milk samples were subjected to bacteriological examination total
bacterial counts (TBC), coliform counts and psychrotrophic counts.
Also evaluations of the physiochemical properties of milk were
determined by measuring milk temperature, acidity and pH. Moreover,
antibiotic detection was performed using both Delvotest and Modified
one plate test.
The results indicated that the levels of TBC, coliform counts,
psychrotrophic counts, ranged between log 8.279 to log 11.491
10 10
cfu/ml, log 3.845 to log 9.179 cfu/ml, 0 to log 1.690 cfu/ml. The
10 10 10
acidity, pH, and temperature of milk samples were 0.11 % to 0.3 %,
6.5 to 6.99 and 13 to 30.7º C, respectively. These results revealed that
there were no significant differences (P> 0.05) between the two areas
(Khartoum North and Khartoum) for milk samples which might
indicate the similarity of production systems, management, handling,
storage and transportation conditions of milk in the studied area.
In the present study it was found that the mean level of TBC,
coliform counts and acidity of milk samples from sales point's samples
were found to be log 11.136± 0.215 cfu/ml, log 8.802± 0.254
10 10
cfu/ml and 0.219± 0.048 %, respectively. These values were found to
be higher than the values, which recorded for the milk samples that
were collected from the farms (log 9.089± 0.281 TBC, log 4.789±
10 10
0.340 coliform, 0.158± 0.032 % acidity). However, psychrotrophic
counts revealed higher mean value (log 0.227± 0.523 cfu/ml) for
10
farms samples compared to sales points samples (log 0.069± 0.238).
10
The results also indicated significant variations (P<0.05) in TBC,
coliform counts and acidity of milk samples between farms and sales
points.
Antibiotic residues were detected in 28 (38.9%) of examined
milk samples, 17(23.6%) of these were in Khartoum North and
11(15.3 %) were in Khartoum. On the other hand the milk samples
from sales points had the highest percent of the antibiotic residues 20
(55.6%) compared to those detected in the farms (8; 22.2%). The 28 (
38.9%) milk samples that showed positive results were confirmed for
the presence of antibiotic residues after heat treatment and 26 (92.9%)
of them remained positive.
The present study concluded that the raw milk samples examined
in the studied areas was of low quality. Examination of milk for
bacterial counts and antibiotic residues detection could provide an
indicator for a current potential problem associated with milk quality.
Hence it was recommended that quality assurance programs should be
started to ensure that good quality milk and milk products are
produced and consumed in the Sudan.
ﻪﺣﻭﺮﻃﻻﺍ ﺺﺨﻠﻣ
. ﻡﻭـﻁﺭﺨﻟﺍ ﺔـﻴﻻﻭ ﻲـﻓ ﻥﻴﻜﻠﻬﺘﺴﻤﻠﻟ ﻡﺩﻘﻴ ﻱﺫﻟﺍ ﻥﺒﻠﻟﺍ ﺓﺩﻭﺠ ﻡﻴﻴﻘﺘﻟ ﺔﺴﺍﺭﺩﻟﺍ ﻩﺫﻫ ﺕﻴﺭﺠﺃ
36 36 72
ﻥـﻤ ( ﻡﻭـﻁﺭﺨﻟﺍ ﻥـﻤ ﻪﻨﻴﻋ ﻭ ﻱﺭﺤﺒ ﻡﻭﻁﺭﺨﻟﺍ ﻥﻤ ﻪﻨﻴﻋ ) ﻥﺒﻠﻟﺍ ﻥﻤ ﺔﻨﻴﻋ ﺕﻌﻤﺠ
.ﻊﻴﺒﻟﺍ ﻁﺎﻘﻨ ﻭ ﻉﺭﺍﺯﻤﻟﺍ
ﺔﺒﺤﻤﻟﺍ ﺎﻴﺭﺘﻜ ﺒﻟﺍ ﻭ ﻥﻭﻟﻭﻘﻟﺍ ﺎﻴﺭﺘﻜﺒ ،ﺎﻴﺭﺘﻜﺒﻠﻟ ﻲﻠﻜﻟﺍ ﺩﻌﻟﺍ ﺙﻴﺤ ﻥﻤ ﺕﺎﻨﻴﻌﻟﺍ ﻊﻴﻤﺠ ﺭﺎﺒﺘﺨﺍ ﻡﺘ

لﺃ ﻭ ﺔﻀﻭﻤﺤﻟﺍ ،ﺓﺭﺍﺭﺤﻟﺍ ﺔﺠﺭﺩ ﺱﺎﻴﻘﺒ ﻥﺒﻠﻟ ﺔﻴﺌﺎﻴﻤﻴﻜﻭﻴﺯﻴﻔﻟﺍ ﺹﺌﺎﺼﺨﻟﺍ ﺱﺎﻴﻗ ﻡﺘ ﺎﻤﻜ ﻭ ﺓﺩﻭﺭﺒﻠﻟ
Delvotest .pH
ﻭ ﻡﺍﺩﺨﺘـﺴﺎﺒ ﺔـﻴﻭﻴﺤﻟﺍ ﺕﺍﺩﺎﻀﻤﻟﺍ ﺎﻴﺎﻘﺒ ﻥﻋ ﻑﺸﻜﻟﺍ ﻡﺘ ﻙﻟﺫ ﻰﻠﻋ ﺓﻭﻼﻋ
.Modified one plate test

ﺔـﺒﺤﻤﻟﺍ ﺎـﻴﺭﺘﻜﺒﻟﺍﻭ ﻥﻭـﻟﻭﻘﻟﺍ ﺎﻴﺭﺘﻜﺒ ﺩﺍﺩﻋﺃﻭ ﺎﻴﺭﺘﻜﺒﻠﻟ ﻲﻠﻜﻟﺍ ﺩﻌﻟﺍ ﻥﺃ ﺔﺴﺍﺭﺩﻟﺍ ﺕﺤﻀﻭﺃ
log log 3.845 log 11.491 cfu/ml log 8.279
10 ﻲﻟﺇ 10 ، 10 ﻲﻟﺇ 10 ﻥﻴﺒ ﺡﻭﺍﺭﺘﺘ ﺓﺩﻭﺭﺒﻠﻟ
pH log 1.690 cfu/ml 0 9.179 cfu/ml
ﺓﺭﺍﺭـﺤﻟﺍ ﺔﺠﺭﺩ ﻭ لﺃ ،ﺔﻀﻭﻤﺤﻟﺍ ﺎﻤﻨﻴﺒ . 10 ﻲﻟﺇ ،
30.7 ºC 13 6.99 6.5 % 0.3 % 0.11
.ﻲﻟﺍﻭﺘﻟﺍ ﻰﻠﻋ ﻰﻟﺇ ﻭ ﻲﻟﺇ ، ﻰﻟﺇ ﻥﻴﺒ ﺕﺤﻭﺍﺭﺘ ﺩﻘﻓ
(P> 0.05)
ﻱﺫـﻟﺍ ﻭ ،ﻥﻴـﺘﻘﻁﻨﻤﻟﺍ ﻥﻴﺒ ﺔﻴﻭﻨﻌﻤ ﻕﻭﺭﻓ ﺩﺠﻭﺘ ﻻ ﺔﻨﺃ ﺞﺌﺎﺘﻨﻟﺍ ﻩﺫﻫ ﺕﺭﻬﻅﺃ
ﻲـﻓ ﻥﺎـﺒﻟﻸﻟ لـﻘﻨﻟﺍ ﻑﻭﺭﻅ ﻭ ﻥﻴﺯﺨﺘﻟﺍ ،لﻭﺍﺩﺘﻟﺍ ،ﺓﺭﺍﺩﻹﺍ ﻭ ﺝﺎﺘﻨﻹﺍ ﻡﻅﻨ ﻲﻓ ﻪﺒﺎﺸﺘﻟﺍ ﻲﻟﺇ ﺭﻴﺸﻴ
.ﺔﺴﺍﺭﺩﻟﺍ ﻕﻁﺎﻨﻤ
ﻭ ﻥﻭـﻟﻭﻘﻟﺍ ﺎـﻴﺭﺘﻜﺒ ﺩﺍﺩـﻋﺃ ﻭ ﺎـﻴﺭﺘﻜﺒﻠﻟ ﻰﻠﻜﻟﺍ ﺩﻌﻟﺍ ﻁﺴﻭﺘﻤ ﻥﺃ ﺔﺴﺍﺭﺩﻟﺍ ﻩﺫﻫ ﻲﻓ ﺩﺠﻭ
log 11.136± 0.215 cfu/ml
، 10 ﻭـﻫ ﻊـﻴﻤﺠﺘﻟﺍ ﻁﺎـﻘﻨ ﻲـﻓ ﻥﺒـﻠﻟﺍ ﺕﺎـﻨﻴﻌﻟ ﺔـﻀﻭﻤﺤﻟﺍ
0.219± 0.048 % log 8.802± 0.254 cfu/ml
ﻰـﻠﻋﺃ ﻡﻴﻘﻟﺍ ﻩﺫﻫ ﺕﻨﺎﻜ .ﻲﻟﺍﻭﺘﻟﺍ ﻰﻠﻋ ﻭ 10
log 9.089±
10 ﺎـﻴﺭﺘﻜﺒﻠﻟ ﻰﻠﻜﻟﺍ ﺩﻌﻟﺍ) ﻉﺭﺍﺯﻤﻟﺍ ﻥﻤ ﻩﺫﻭﺨﺎﻤﻟﺍ ﻥﺒﻠﻟﺍ ﺕﺎﻨﻴﻌﻟ ﺕﻠﺠﺴ ﻲﺘﻟﺍ ﻙﻠﺘ ﻥﻤ
0.158± 0.032% log 4.789± 0.340 0.281
ﻥﻤ .( ﺔﻀﻭﻤﺤﻟﺍ ﺔﺒﺴﻨﻭ 10 ﻥﻭﻟﻭﻘﻟﺍ ﺎﻴﺭﺘﻜﺒﻟ ،
log 0.227± 0.523cfu/ml
( 10 ) ﺎﻬﻟ ﻡﻴﻗ ﻲﻠﻋﺍ ﺕﺩﺠﻭ ﺓﺩﻭﺭﺒﻠﻟ ﺔﺒﺤﻤﻟﺍ ﺎﻴﺭﺘﻜﺒﻟﺍ ﻥﺎﻓ ﻪﻴﻨﺎﺜ ﺔﻴﺤﺎﻨ