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ARTICLE ORIGINAL
A survey of Salmonella contamination
in chicken carcass and giblets
in Central Ethiopia
B. MOLLA* and A. MESFIN
Department of Microbiology, Infectious Diseases and Veterinary Public Health, Faculty of Veterinary Medicine, Addis Ababa University, P.O. Box 34, Debre Zeit, Ethiopia
* Corresponding author. Tel. +2511 33 89 17 / 33 8062 ; Fax : +25 11 33 99 33 ; E-mail : [email protected]
SUMMARY
RÉSUMÉ
A study was conducted to estimate the prevalence and distribution of
Salmonella in raw chicken meat and giblets (liver, gizzard and heart) from
poultry processing plants and retail markets at Debre Zeit and Addis Ababa,
Ethiopia. A total of 378 samples were collected from two processing plants
and retail markets from November 2001 to April 2002.
Of the total 378 samples examined, Salmonella was detected in 80
(21.1 %) of the samples analysed. Among the chicken samples examined
high proportion of chicken meat (15.4 %), liver (34.5 %), gizzard (41.1 %),
heart (23.7 %) and skin (7.7 %) were contaminated with Salmonella. Out of
the total 80 Salmonella isolates, 8 different serotypes were identified of
which S. Braenderup (53.7 %) was the most frequent followed by S.
Typhimurium var. Copenhagen (30.0 %), S. Anatum (10.0 %), S. Kottbus
(6.2 %) and S. Typhimurium (3.7 %). Other serovars isolated include S.
Bovismorbificans, S. Hadar and S. Infantis. Results of the present study
indicated that there was a high level of Salmonella contamination of chicken meat and giblets in processing plants and retail markets, which could be
considered as one of the major potential source of human salmonellosis in
Ethiopia.
Enquête sur la contamination par Salmonella des carcasses et abats de
poulet en Ethiopie centrale. Par MOLLA (B.) et MESFIN (A.).
KEY-WORDS : Salmonella - chicken meat - giblets - survey - Ethiopia.
MOTS-CLÉS : Salmonella - viande de poulet - abats enquête - Ethiopie.
Introduction
uncontaminated carcasses and giblets in which contamination could continue during subsequent handling, processing
and preparations [7, 25, 27].
Poultry and poultry products are usually incriminated in
outbreaks of human salmonellosis. Salmonella often reach
the carcasses from the intestinal tracts or faecal materials on
feathers or feet. Particularly scalding, defeathering, evisceration and giblet operations are the major points of spread in
poultry processing plants [7, 10, 27]. The cross-contamination of the hands of workers, working equipment and utensils
could also serve as a means of spread of Salmonella to
Revue Méd. Vét., 2003, 154, 4, 267-270
Une étude a été menée pour estimer la prévalence et la distribution de
Salmonella dans la viande crue et les abats (foie, gésier et cœur) de poulet
provenant d’établissements de transformation de volailles et de marché de
détail à Debre Zeit et Addis Abeba, Ethiopie. 378 échantillons ont été prélevés dans deux établissements de transformation et des marchés de détail
entre novembre 2001 et avril 2002.
Sur les 378 échantillons examinés, Salmonella a été isolée dans 80
(21,1 %) des échantillons. Parmi les échantillons de poulet examinés, une
forte proportion de viande de poulet (15,4 %), de foie (34,5 %), de gésier
(41,1 %), de cœur (23,7 %) et de peau (7,7 %) était contaminée par
Salmonella. Sur les 80 souches de Salmonella isolées, 8 sérotypes différents
ont été identifiés, parmi lesquels S. Braenderup (53,7) était le plus fréquent,
suivi par S. Typhimurium var. Copenhagen (30 %), S. Anatum (10 %), S.
Kottbus (6,2 %) et S. Typhimurium (3,7 %). Les autres sérovars isolés
comprennent S. Bovismorbificans, S. Hadar et S. Infantis. Les résultats de
la présente étude indiquent qu’il y avait un fort taux de contamination de la
viande de poulet et des abats dans les établissements de transformation et
les marchés de détail, ce qui pourrait être considéré comme une des sources
potentielles majeures de salmonellose humaine en Ethiopie.
In several countries, a high level of Salmonella contamination in chicken carcasses and giblets from processing plants
or retail markets has been reported [5, 9, 13, 17, 23, 24, 27].
Previous works undertaken in Ethiopia indicated the presence and distribution of Salmonella in poultry farms [21],
cattle [1, 22], poultry meat and meat products [6], selected
food items [20] and man [19]. Various serotypes of
268
Salmonella were also identified from slaughtered cattle and
poultry, foods and man in Ethiopia [1, 6, 19, 20, 21, 22].
A periodic surveillance of the level of Salmonella contamination in the different food animals, food products and environment is necessary to control the spread of the pathogen
and infection of man [5, 12]. The knowledge on the prevalent
Salmonella serotypes in a country is also important in order
to understand the distribution and means of introduction into
a country [16]. This study was, therefore, undertaken from
November 2001 to April 2002 to determine the prevalence
and distribution of serotypes of Salmonella in chicken carcass and giblets obtained from processing plants and retail
markets at Debre Zeit and Addis Ababa, Ethiopia.
Materials and methods
SAMPLE COLLECTION AND PROCESSING
Chicken meat, skin and giblet (liver, gizzard and heart)
samples (n = 286) were obtained from two processing plants
at Debre Zeit, 47 km south east of Addis Ababa while
92 chicken meat and skin samples were purchased from different retail markets in Addis Ababa as whole or chicken
parts. Samples were collected every two weeks from
November 2001 to April 2002. The samples consisted of
chicken meat and skin (n = 104 for each), liver (55), gizzard
(56) and heart (59). Each sample was collected aseptically
and transported in portable coolers immediately to the microbiology laboratory of Faculty of Veterinary Medicine, Addis
Ababa University, Debre Zeit, Ethiopia. The samples were
tested upon arrival or were stored at freezer temperature for
no longer than a week.
ISOLATION AND IDENTIFICATION OF SALMONELLA
Frozen chicken meat and giblet samples were thawed at
room temperature for 4 to 5 hours before analysis. From each
sample 25 g was weighed and cut into fine smaller pieces
using sterile scalpel blades. The 25 g chicken meat sample
consisted of breast muscle, neck, leg and wall of visceral
cavity. The isolation and identification of Salmonella was
carried out following the techniques recommended by the
International Organisation for Standardisation [15]. Briefly,
the following procedures were employed :
Twenty-five grams of each sample were put into a stomacher bag containing 225 ml buffered peptone water (BPW,
Merck) and homogenised using a stomacher (Colworth 400,
London). The homogenate was incubated at 37°C for 16 to
20 hours. From the pre-enriched sample, 0.1 ml and 1 ml of
the test aliquot was transferred into 10 ml of Rappaport
Vassiliadis (RV, Merck) and 10 ml of selenite cystine medium
(SC, Difco) and incubated at 42°C and 37°C for 18 to
24 hours, respectively. This was followed by streaking onto
MacConkey (Merck) and brilliant green phenol-red lactosesucrose (BPLS, Merck) agar plates and incubated at 37°C for
24 to 48 hours. Presumptive Salmonella colonies were then
subjected to further biochemical tests. The presence of
MOLLA (B.) AND MESFIN (A.)
Salmonella antigens was tested by slide agglutination using
polyvalent Salmonella anti-sera I and II (Sifin, Berlin,
Germany). Those isolates tentatively identified as Salmonella were sent to the OIÉ Reference Laboratory for
Salmonellosis of Health Canada in Guelph, Ontario, Canada
for complete serotyping and phage typing.
The somatic (O) antigens of the Salmonella isolates were
determined by slide agglutination tests as described by
EWING [14]. The flagellar (H) antigens were identified
using a microtechnique [26] that employs microtitre plates.
The antigenic formulae of LE MINOR and POPOFF [18]
were used to name the serovars. The standard phage typing
technique described by ANDERSON and WILLIAMS [3]
was employed throughout. The phage typing scheme and
phages for S. Typhimurium, developed by CALLOW [8] and
further extended by ANDERSON [2] and ANDERSON et al.
[4] were obtained from the Central Public Health Laboratory,
Colindale, London, United Kingdom.
Results
Of the total of 378 samples examined, 21.1 % (80/378)
were contaminated with Salmonella (Table I). Out of the total
286 samples (n = 378) analysed from processing plants,
64 (22.3 %) proved to be Salmonella positive whereas from
92 samples obtained from retail markets 16 (17.3 %) contained Salmonella. A high level of Salmonella contamination
was found in chicken gizzard (41.1 %) and liver (34.5 %) followed by heart (23.7 %), meat (15.4 %) and skin (7.7 %).
Sample type
Number of samples
Examined
%
Positive
Meat
Skin
Liver
Gizzard
Heart
104
104
55
56
59
16
8
19
23
14
15.4
7.7
34.5
41.1
23.7
Total
378
80
21.1
TABLE I. — Salmonella isolated from chicken meat and giblets.
Out of the total 80 Salmonella isolates, 8 different serotypes were identified of which S. Braenderup was the most
frequent followed by S. Typhimurium var. Copenhagen,
S. Anatum, S. Kottbus and S. Typhimurium (Table II). Other
serovars isolated include S. Bovismorbificans, S. Hadar and
S. Infantis. Salmonella Typhimurium and S. Kottbus were
detected only from samples taken at processing plants whereas S. Hadar and S. Bovismorbificans were isolated only
from retail market samples (Table II).
The phage typing of Salmonella Typhimurium variety
Copenhagen indicated that only phage type 120 was identified from all sample types whereas phage type 1 and 104 of
S. Typhimurium were detected from chicken liver and gizzard samples (Table II).
Revue Méd. Vét., 2003, 154, 4, 267-270
A SURVEY OF SALMONELLA CONTAMINATION IN CHICKEN CARCASS AND GIBLETS IN CENTRAL ETHIOPIA
Serotype
Number isolated from
Processing Retail market
Total
%
Phage
type
identified
plant
S. Braenderup
28
S. Typhimurium
22
var. Copenhagen
S. Anatum
5
S. Kottbus
5
S. Typhimurium
3
S. Hadar
S. Infantis
1
S. Bovismorbificans Total
7
2
35
24
53.7
30.0
3
2
1
1
8
5
3
2
2
1
10.0
6.2
3.7
2.5
2.5
1.2
64/286 (22.3%) 16/92 (17.3%) 80/378
120
1 and 104
-
Serotype
S. Braenderup
S. Typhimurium var.
Copenhagen
S. Anatum
S. Kottbus
S. Typhimurium
S. Infantis
S. Hadar
S. Bovismorbificans
Total
Number of positive samples
269
Total
Liver
Heart
Gizzard
Skin
Meat
8
9
6
5
11
8
2
1
8
1
35
24
2
-
1
2
-
2
1
1
-
3
1
1
2
2
1
2
-
8
5
3
2
2
1
19
14
23
8
16
80
21.1
TABLE II. — Salmonella serotypes identified from chicken meat and giblets.
TABLE III. — Distribution of Salmonella serotypes in chicken meat and
giblets.
Salmonella Braenderup and S. Typhimurium var.
Copenhagen were isolated from all sample types (chicken
meat, skin, gizzard, heart and liver) while S. Hadar and S.
Bovismorbificans were detected only from chicken meat and
skin samples respectively (Table III). Other serotypes were
isolated from two or more of the samples analysed.
these, scalding water can become contaminated with Salmonella from faeces, plucking equipment, cages and floors.
Workers can spread the contamination during retailing [5,
27]. Rupture of the intestine could also occur during evisceration and pooling giblets might lead to cross-contamination
of carcasses and other chicken parts.
In our study samples obtained from retail markets were
relatively less contaminated with Salmonella (17.3 %) than
those from processing plants (22.3 %). This could be due to
the low number of samples included from the retail markets
(n = 92) as compared to those from the processing plants
(n = 286). The improper handling of chicken meat and giblets
by food handlers during preparation and distribution might
result in increased cross-contamination of Salmonella from
giblets to meat. Therefore, an increased detection rate of
Salmonella could be obtained in chicken samples from retail
market than those from processing plants [9, 17].
Out of the total 80 Salmonella isolates, 8 different Salmonella serotypes were identified (Table II). The most prevalent
serotypes were Salmonella Braenderup, followed by S.
Typhimurium var. Copenhagen, S. Anatum, S. Kottbus, and
S. Typhimurium. Previously other workers have reported
some of these serotypes in poultry meat and poultry products
[6, 9, 20, 27]. It should also be noted that the presence and
distribution of Salmonella serotypes could vary from region
to region [13, 27]. While some serotypes emerge and
decrease over time, others maintain their dominant role for
many years with widespread distributions. The rapid international trade in agricultural, aquacultural and food products
has also facilitated the introduction of new Salmonella serotypes into importing countries [11].
Salmonella Enteritidis has been previously isolated from
Ethiopian chicken [20, 21]. However, in our study and that of
BONIPHACE [6], it was not detected from any of the
samples examined. It is possible that Salmonella Enteritidis
could be present in Ethiopian chicken in such low numbers
that our present sample size was not large enough to detect it.
Previously MOLLA et al. [20] isolated S. Enteritidis and S.
Discussion
The level of Salmonella contamination of chicken samples
observed in our study (21.1 %) was relatively high and
confirms the findings of previous studies on Salmonella
contamination in poultry and poultry products in Ethiopia [6,
20, 21]. A number of authors in different countries have
reported different prevalence rates of Salmonella in poultry
and poultry products: 22.8 % in UK [23], 35.5 % in Malaysia
[24], 35.8 % in Spain [13], 36.7 % in Belgium [27] and 66 %
in Thailand [17].
The variation in the prevalence of Salmonella contamination could be partly due to differences in sample type, sampling techniques, distribution of salmonellae in a lot examined and the detection methods employed [7, 13, 24, 27]. In
the present study out of the total 378 samples 170 (45 %)
were giblets, which had higher contamination level of
Salmonella (32.9 %) than carcass samples (9.6 %). This was
in agreement with the findings of JERNGKLINCHAN et al.
[17] and BONIPHACE [6] who reported respectively 86 %
(190/221) and 42 % (24/57) prevalence rates of Salmonella
in chicken giblets. Comparison could also be made with the
other studies in which a high level of Salmonella contamination was detected in retail chicken meat and giblets [5, 9, 13,
16, 23, 24] which in turn confirms the widespread contamination of chicken and chicken products with Salmonella.
Cross-contamination of Salmonella from giblets to carcass
could occur during handling, processing, packing and distribution. The packing of giblets with the carcass observed in
this study at processing plants could have also contributed to
increase Salmonella cross-contamination. In addition to
Revue Méd. Vét., 2003, 154, 4, 267-270
270
Typhimurium from edible chicken offals in Addis Ababa and
MOLOMO [21] reported S. Enteritidis, S. Anatum, andS.
Uganda from chicken as well as from environmental samples
of selected poultry farms at Debre Zeit, Ethiopia. MACHE et
al. [19] isolated 6.4 % Salmonella strains (45/700) from
human diarhoeal outpatients in Addis Ababa, Ethiopia of
which Salmonella serogroup B (24.4 %), C (31.1 %), D
(13.3 %) and E (6.7 %) were identified. These indicate the
presence and distribution of various serotypes of Salmonella
of animal and human origin, which are of significance in the
veterinary and public health sectors in Ethiopia. The isolation
of invasive Salmonella serotypes such as S. Typhimurium
and other pathogenic salmonellas in our study indicates the
public health significance of these serovars as contaminated
chicken meat and meat products may pose health hazards.
This risk may further be higher if chicken meat or giblets are
consumed undercooked or cross-contamination in the kitchen with Salmonella during meal preparation [10, 25, 27].
JERNGKLINCHAN et al. [17] reported a higher prevalence
of Salmonella (10 %) than expected in cooked chicken products and was attributed to improper handling of these products during marketing and preparations which might have
resulted in cross-contamination.
The importance of some of the basic instructions regarding
storage temperature, cooking and prevention of Salmonella
contamination and cross-contamination is not appreciated by
many consumers [25, 27]. Therefore, efforts should be made
to enhance public awareness and consumer education to prevent the horizontal spread of Salmonella. This is of particular
importance in developing countries like Ethiopia where there
are inadequate facilities including refrigeration at meat processing plants and home as well. Some of the measures in
controlling Salmonella and other foodborne pathogens in the
food chain include the introduction of good manufacturing
practices (GMP) and hazard analysis critical control point
(HACCP) concepts together with stringent control of all
aspects of chicken meat production, preparation and distribution [12]. Education of personnel involved in food preparation and microbiological monitoring of broiler chicken and
rejection of infected flocks from food production is also
required [5, 12]. The high level of contamination of chicken
meat and giblets with Salmonella observed in our study indicates the need for an improvement in the microbiological
quality of retail chicken. There is also a need for a comprehensive epidemiological study and control of Salmonella
contamination at various levels of chicken production and
processing plants in Ethiopia.
Acknowledgements
The authors thank Dr Anne MUCKLE, head of Laboratory
for Foodborne Zoonoses, Health Canada and the technical
staff at the OIÉ Reference Laboratory for Salmonellosis,
Health Canada for the complete serotyping and phage typing
of our Salmonella isolates. Drs Daniel ALEMAYEHU and
Woubitu SALAH are acknowledged for their excellent technical assistance.
MOLLA (B.) AND MESFIN (A.)
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