International Journal o] Food Microl~ioh~gy, 15 (1992) 45-5t)
45
.~ 1992 Elsevier Science Publishers B.V. All rights reserved 0168-161)5/92/$05.110 FOOD 1111454
Distribution and numbers of Campylobacter in newly slaughtered broiler chickens and hens Eva B e r n d t s o n 1, M a r i a T i v e m o 2,, a n d A n d e r s E n g v a l l 2 l)~7~arOm'nt of Food Ilygiene. Facuhy of Veterinao" Medichle, Swedish Unicersity of Agricultural St'h'nt~t's, Ul~ltsala, Sweden and 2 Dit'ision ¢~f I-pizootioh~,l,9", National Vt'teritlatT htstitute, Uppsahl, Swedt, n (Received 13 June 1991: accepted 9 October 1991 )
if ('aml,yh,hacter is present in the intestinal tract, broiler carcasses become extensively contaminated during the slaughter process. To determine the distribution and numbers of Campylobacter jejuni/coli in newly slaughtered broiler chickens and hens, a total of 1111)birds from six Campylobacter-positive flocks were s~mlpled at lhree Swedish processing plants. Campylob;ictcrs were isolated in 89% of neck skins, 939; of peritoneal cavity swab samples and in 75¢~ of subcutaneous samples. Muscle samples were only very sparsely contaminated. It is likely that the feather follicles arc thc orifices where C..h'iuni/coli is introduced into the subcutis layer. Key words: Campyh,hacter jejuni ~coil: Poultry: Broiler; Carcasses; Meat: Skin
Introduction Infection with Campylobacterjejuni/coli is a common cause of enterocolitis in malk hi the industrialized world and poultry is considered a major source of such infcctions (Blaser et al., 1983; Skirrow, 1987). It is well known that the poultry carcasses can become contaminated with Canlpylobacter bacteria from their intestinal contents during the slaughter process (Wempe et al., 1983; Genigeorgis et al., 1986). To reduce this contamination, it is essential to know which parts of the carcasses that become contaminated during this process. It is also important to ~c~ermine wether the contamination is restricted to the surface or if deeper parts ui ,.,~ ~::~rcas~;c~arc ~.ffectcd. Very fcw ~tudics on thcsc topics hav~ been found in the literature. Altmeycr ct al. (1985) did not find Campylobacter in 50 muscle samples from broilers. The object of the present study was to investigate the distribution and numbers of Campylobacter jejuni/coli in different localities of carcasses of newly slaughtered and processed birds. The flocks investigated were known to harbour Campylobacter in their intestinal tracts during breeding. Correspondence address: Eva Berndtson, Department of Food Hygiene, Faculty of Veterinary Medicine, P.O. Box 70119, S-750 117 Uppsala, Sweden. * Present address: A.I. Cooperative, ()rnsro, Skara. Sweden.
46
Materials and Methods
Samples were taken from slaughtered and processed birds from six different flocks raised on four farms. Broiler chickens (flocks 1-4 and 6) were approximately 5 weeks of age when slaughtered. Flock number five consisted of broiler hens of approximately 55 weeks of age. The sixth flock was part of a study involving infection of chickens with three strains of Campylobacter jejuni, introduced via their drinking water at 5, 7 and 20 days of age. The three slaughterhouses involved in the study used conventional fully automatic slaughter methods, with scalding temperatures of 58-60°C and water chilling. From each bird. samples were collected of caecal contents and from different parts of the carcass (Tables I, II and liD. The intestines were collected on the eviscerating line and the corresponding carcasses (marked by numbered rubber bands) were collected after processing and chilling. All samples were placed individually in plastic bags and transported to the laboratory in chilled boxes. All caecal samples were analysed on the day of slaughter and all other samples on the following day.
Caecal samples One gram of caecal content from each bird was added to a tube containing 9 ml of peptone water. For culturing, see the section on Peptone water.
Muscle samples From each carcass, 10-g samples were removed, using sterile scalpel blades, from two breast and two thigh muscles after removal of the skin, taking care not to contaminate the muscle surface which was not disinfected before removing the tissue for culture. Each sample was added to 90 ml of peptone water in a plastic bag and treated in a stomacher (Lab Blendor 400, Colworth) for one minute, followed by cu',turing (see Peptone water). Four one-gram samples, removed in the same manner as the 10-g samples, were transferred to tubes containing 5 ml of Preston enrichment broth (see Preston enrichment broth).
Neck skin samples Approximately 2 x 2 cm of the outer surface of the neck skin of each carcass was thoroughly rubbed with a cotton swab which then was placed in a tube containing 9 mi of peptone water, and vigorously shaken (see Peptone water). For qualitative analysis another 2 × 2 cm area was rubbed with a cotton swab which then was placed in a tube containing 5 ml of Preston enrichment broth (see below). Ten grams of each neck skin were also quantitatively analysed according to methods outlined for muscle samples.
Subcutaneous skin samples (feather follicles) Pieces of skin from the back of each carcass were aseptically removed and pinned, with the subcutaneous side up, on a piece of sterile plastic-covered cardboard. Four 2 × 2 cm areas were scraped with separate sterile scalpel blades,
47 taking care not to penetrate the cutis layer. Three scalpel blades with subcutaneous materials were each put into a tube with 9 ml peptone water and a fourth scalpel blade was put in 5 mi Preston enrichment broth and cultured (see below).
Peritoneal cacity With cotton swabs two 2 × 2 cm areas of the surface of the peritoneal cavity were thoroughly rubbed. One swab was put into a tube with 9 ml of peptone water and the other swab in 5 ml of Preston enrichment broth and cultured (see below). Media, culture technique and biochemical tests Peptone water 0.1%, consisted of 1.0 g peptone (Merck), 8.5 g sodium chloride and 1009 ml distilled water. For quantitative analyses, ten-fold serial dilutions were made in peptone water and, from appropriate dilutions, 0.1 ml was plated on modified Preston agar plates. The plates were incubated (see below) and colony forming units (CFU) of C. jejuni/coli were counted. Preston enrichment broth (Bolton and Robertson, 1982) consisted of Nutrient broth No. 2 (Oxoid CM 67), 5% (v/v) saponin-lysed horse blood and Preston Campylobacter Selective Supplement (Oxoid SR 117). This supplement consisted of polymyxin B, 5000 IU/I, trimethoprim lactate, 10 mg/l, rifampicin, 10 mg/l, and cycloheximide, 109 mg/I. Preston selectice agar (Bolton and Robertson, 1982) consisted of Campyiobacter agar base (Oxoid CM 689), 5% (v/v) saponin-lysed horse blood and Campylobacter selective supplement (Oxoid SR l l7). In the quantitative analyses, the agar content was increased to 2% to prevent the spreading of Campylobacter colonies. Horse blood agar consisted of Blood Agar Base (Oxoid CM 271) and 5% (v/v) defibrinated horse blood. Incubation: all enrichment broth tubes and agar plates were incubated microaerobica!!y in anaerobic jars with palladium catalysts and Campy Pak (BBL). Broth tubes were incubated for 24 h at 42°C, after which selective agar plates were inoculated using cotton swabs and incubated for 48 h at 42°C. Presumptive Campylobacter colonies were Gram-stained and examined for motility by phase contrast microscopy. Gram-negative, curved bacteria which showed characteristic movements were considered as potential Campylobacters. Colonies of those isolates were subcuitured on horse blood agar plates. The colonies were tested for oxidase and catalase activity and positive isolates were considered to be C. jejuni/coli.
Results and Discussion
The incidence of Campylobacter in muscles was very low, only 9 out of 340 samples, i.e., 3% (data not shown). However, muscle contamination has potentially important implications for public health and should be further investigated. The
48 TABLE ! Number of C jejuni isolated from neck skins Experiment (flock) number
I 2 3 4 5 6 Total " h c d
Neck skin swab samples ~ Enrichment method
Neck skin swab samples ~ Quantitative method
Neck skin samples 10 g stomached Quantitative method
Pos "
(;i
Pos ;~
Number h
Pos ''
Number t,.c
16/19 I(1/10
84 1011 1(111 Illl) 511 911 89
19/19 6/1(I 20/20 0/11) d
2.4-+0.47 1.4-+0.66 2.5 -+ 0.58 < 2.11 1.2 _4-0.65
18/18
3.0+0.41
2(I/2(I Ill/Ill 5/!11 9/11t
70/79
9/10 N.I. t
9/10 18/19 N.I. N.1. 29/30
2.8_+_+0.44 3.4__+(I.38
2.7 -+ (I.44
Number p o s i t i v e / n u m b e r sampled. Mean log m colony forming units_+ standard deviation in the positive samples. A 4 cm 2 area sampled. Ix)west dilution investigated in this flock was I(1 -' Per gram sample. Not investigated.
numbers of C. fljuni ~col( found in neck skins are shown in Table 1, the numbers of positive scrapings of subcutaneous skin are shown in Table II, and those in peritoneal cavities and caecal contents are shown in Table i1I. The present study shows that if Campylobacter is present in the intestinal canals, broiler carcasses become extensively contaminated during the slaughter process. This has been reported earlier, as well as the stages of the slaughter process during which contamination occurs (Oosterom et al., 1983; Genigeorgis et al., 1986). However, an important consideration is whether deeper parts of the carcasses are contaminated to any degree. The number of subcutaneous samples
T A B L E 1I
Occurrence of C. jc'juni in subcutaneous scrapings (feather follicles) from poultry Experiment (flock) number
Enrichment method Pos a.c ~
Quantitative method Pos ,,.c
Number b
1 2 3 4 5 6 Total
17/2O 9/9 20/20 8/10 1/ 10 19/30 74/99
34/611 7/29 47/60 0/30 d 22/30 6/60
1.44 -+ 0.49 ! .08 +_0.23 !.6 ! _+(I.73 < 2.() 1.88 -t- 0.80 1.83 +_11.41
a.h.c.d See Table I.
85 I(10 1(10 8(1 10 63 75
49 TABLE 111 Number of ( \ jejuni isolated from peritoneal cavity and caecal contents Experiment
Peritoneal cavity swab samples "
Caecal content
(flock) number
Enrichment method
Quantitative method
Quantitative method
Pos ~'
c~
Pos"
Number i,
Pos ~
I 2 3 4 5 6 Total
19/20 I11110 21)/211 I0/I0 6/10 28/30 93 / 1110
95 I01) I IX) I00 61) 93 93
2t)/20 6110 20/211 9/10 2/10 10/30
3.0 -+11.39 2.7_+0.38 3.2 _+0.59 2.9_+0.67 3.4 -+0.47 2.3 _+0.37
20/20 N.I. 20/21) I0/I0 9/1(t 30/30
~,,h.~.d.f
See Table
d
Number h 7.5 + 0.91 7.2 + 1.46 8.1 -+0.56 5.8_+ 1.17 > 9.0
1.
showing growth of Campylobacter was high (75%, Table il), but the numbers of Carnpylobacter in these samples generally were low compared to numbers on the neck skin or in the peritoneal cavity. It is likely that the feather follicles are the orifice through which C. jejuni/coli is introduced into the subcutis layer. The scalding procedure is used to open the feather follicles in order to facilitate the removal of feathers. The follicles might remain open throughout the processing until the carcass is chilled. When the follicles close during chilling, the microorganisms will be retained. Methods to reduce contamination of carcasses by treating the body surfaces with disinfectants duriog scalding have been suggested by Okrend et al. 11986) and Hudson and Mead (1987). It seems, however, unlikely that a disinfectant washed or sprayed over a carcass wc~,lel penetrate all the feather follicles. Even if a surface flora of Campylobacter could be diminished by a disinfectant, thus reducing the risk of cross contamination, Campylobacters hidden in deeper subcutaneous layers might survive the treatment. Due to the low infectious dose in humans, these Campylobacters can cause illness if the chicken is not properly heated during cooking. Removal of the skin before cooking would lower the amount of contamination on the carcass, but the relatively large number of Campylobacters found on the peritoneal cavity surfaces will still remain a risk, especially if the chicken is cooked without being divided into halves or parts before cooking.
Acknowledgements We thank Gunny Blomgren for excellent technical assistance. This work was financially supported by the Swedish Poultry Association and the Swedish Council for Forestry and Agricultural Research.
5O
References Altmeyer, M.. Krabisch. P. and Dorn. P. (1985) Zum Vorkommen und zur Verbreilung yon CampyIobacterjejuni/coli in der JungmastgefliigeI-Produktion_ I. Mitteilung. Dtsch. tier';irztl. Wschr. 92, 456-459. Blaser, M.J., Taylor, D.N. and Feldman, R.A. (1983) Epidemiology of Campylobacterjejuni infections. Epidem, Rev. 5, 157-176. Bolton, F.J. and Robertson, L. (1982) A selective medium for isolating Campylobacter jejuni/coli. J. C!!a. Pathol. 35, 462-467. Genigeorgis, C., Hassuneh, M. and Collins, P. (1986) Campyh)bacter jejuni infection on poultry farms and its effect on poultry meat contamination during slaughtering. J. Food Protect. 49, 895-903. Hudson, W.R. and Mead. G.C. (1987) Factors affecting the survival of Campylobacter jejuni in relation to immersion scalding of poultry. Vet. Rec. 121,225-227. Okrend, A.J.. Johnston, R.W. and Moran, A.B. (1986) Effect of acetic acid on the death rates at 52°C of Salmonella newport, Salmonella typhimurium and Campylobacterjejuni in poultry scald water. J. Food Protect. 49. 500-503. Oosterom, J., Notermans, S., Karman, H. and Engels. G.B. (1983) Origin and prevalence of CampyIobacter jejuni in poultry processing. J. Food Protect. 46, 339-344. Skirrow. M.B. (1987)The twisted germ: Campylobacter. Publ, Hlth. !1)1, 159-163. Wempe, J.M., Genigeorgis, C.A., Farver, T.B. and Yusufu. H.1. (1983) Prevalence of Campylobacter jtjuni in two California chicken processing plants. Appl. Environ. Mielobiol. 45, 355-359.
45
.~ 1992 Elsevier Science Publishers B.V. All rights reserved 0168-161)5/92/$05.110 FOOD 1111454
Distribution and numbers of Campylobacter in newly slaughtered broiler chickens and hens Eva B e r n d t s o n 1, M a r i a T i v e m o 2,, a n d A n d e r s E n g v a l l 2 l)~7~arOm'nt of Food Ilygiene. Facuhy of Veterinao" Medichle, Swedish Unicersity of Agricultural St'h'nt~t's, Ul~ltsala, Sweden and 2 Dit'ision ¢~f I-pizootioh~,l,9", National Vt'teritlatT htstitute, Uppsahl, Swedt, n (Received 13 June 1991: accepted 9 October 1991 )
if ('aml,yh,hacter is present in the intestinal tract, broiler carcasses become extensively contaminated during the slaughter process. To determine the distribution and numbers of Campylobacter jejuni/coli in newly slaughtered broiler chickens and hens, a total of 1111)birds from six Campylobacter-positive flocks were s~mlpled at lhree Swedish processing plants. Campylob;ictcrs were isolated in 89% of neck skins, 939; of peritoneal cavity swab samples and in 75¢~ of subcutaneous samples. Muscle samples were only very sparsely contaminated. It is likely that the feather follicles arc thc orifices where C..h'iuni/coli is introduced into the subcutis layer. Key words: Campyh,hacter jejuni ~coil: Poultry: Broiler; Carcasses; Meat: Skin
Introduction Infection with Campylobacterjejuni/coli is a common cause of enterocolitis in malk hi the industrialized world and poultry is considered a major source of such infcctions (Blaser et al., 1983; Skirrow, 1987). It is well known that the poultry carcasses can become contaminated with Canlpylobacter bacteria from their intestinal contents during the slaughter process (Wempe et al., 1983; Genigeorgis et al., 1986). To reduce this contamination, it is essential to know which parts of the carcasses that become contaminated during this process. It is also important to ~c~ermine wether the contamination is restricted to the surface or if deeper parts ui ,.,~ ~::~rcas~;c~arc ~.ffectcd. Very fcw ~tudics on thcsc topics hav~ been found in the literature. Altmeycr ct al. (1985) did not find Campylobacter in 50 muscle samples from broilers. The object of the present study was to investigate the distribution and numbers of Campylobacter jejuni/coli in different localities of carcasses of newly slaughtered and processed birds. The flocks investigated were known to harbour Campylobacter in their intestinal tracts during breeding. Correspondence address: Eva Berndtson, Department of Food Hygiene, Faculty of Veterinary Medicine, P.O. Box 70119, S-750 117 Uppsala, Sweden. * Present address: A.I. Cooperative, ()rnsro, Skara. Sweden.
46
Materials and Methods
Samples were taken from slaughtered and processed birds from six different flocks raised on four farms. Broiler chickens (flocks 1-4 and 6) were approximately 5 weeks of age when slaughtered. Flock number five consisted of broiler hens of approximately 55 weeks of age. The sixth flock was part of a study involving infection of chickens with three strains of Campylobacter jejuni, introduced via their drinking water at 5, 7 and 20 days of age. The three slaughterhouses involved in the study used conventional fully automatic slaughter methods, with scalding temperatures of 58-60°C and water chilling. From each bird. samples were collected of caecal contents and from different parts of the carcass (Tables I, II and liD. The intestines were collected on the eviscerating line and the corresponding carcasses (marked by numbered rubber bands) were collected after processing and chilling. All samples were placed individually in plastic bags and transported to the laboratory in chilled boxes. All caecal samples were analysed on the day of slaughter and all other samples on the following day.
Caecal samples One gram of caecal content from each bird was added to a tube containing 9 ml of peptone water. For culturing, see the section on Peptone water.
Muscle samples From each carcass, 10-g samples were removed, using sterile scalpel blades, from two breast and two thigh muscles after removal of the skin, taking care not to contaminate the muscle surface which was not disinfected before removing the tissue for culture. Each sample was added to 90 ml of peptone water in a plastic bag and treated in a stomacher (Lab Blendor 400, Colworth) for one minute, followed by cu',turing (see Peptone water). Four one-gram samples, removed in the same manner as the 10-g samples, were transferred to tubes containing 5 ml of Preston enrichment broth (see Preston enrichment broth).
Neck skin samples Approximately 2 x 2 cm of the outer surface of the neck skin of each carcass was thoroughly rubbed with a cotton swab which then was placed in a tube containing 9 mi of peptone water, and vigorously shaken (see Peptone water). For qualitative analysis another 2 × 2 cm area was rubbed with a cotton swab which then was placed in a tube containing 5 ml of Preston enrichment broth (see below). Ten grams of each neck skin were also quantitatively analysed according to methods outlined for muscle samples.
Subcutaneous skin samples (feather follicles) Pieces of skin from the back of each carcass were aseptically removed and pinned, with the subcutaneous side up, on a piece of sterile plastic-covered cardboard. Four 2 × 2 cm areas were scraped with separate sterile scalpel blades,
47 taking care not to penetrate the cutis layer. Three scalpel blades with subcutaneous materials were each put into a tube with 9 ml peptone water and a fourth scalpel blade was put in 5 mi Preston enrichment broth and cultured (see below).
Peritoneal cacity With cotton swabs two 2 × 2 cm areas of the surface of the peritoneal cavity were thoroughly rubbed. One swab was put into a tube with 9 ml of peptone water and the other swab in 5 ml of Preston enrichment broth and cultured (see below). Media, culture technique and biochemical tests Peptone water 0.1%, consisted of 1.0 g peptone (Merck), 8.5 g sodium chloride and 1009 ml distilled water. For quantitative analyses, ten-fold serial dilutions were made in peptone water and, from appropriate dilutions, 0.1 ml was plated on modified Preston agar plates. The plates were incubated (see below) and colony forming units (CFU) of C. jejuni/coli were counted. Preston enrichment broth (Bolton and Robertson, 1982) consisted of Nutrient broth No. 2 (Oxoid CM 67), 5% (v/v) saponin-lysed horse blood and Preston Campylobacter Selective Supplement (Oxoid SR 117). This supplement consisted of polymyxin B, 5000 IU/I, trimethoprim lactate, 10 mg/l, rifampicin, 10 mg/l, and cycloheximide, 109 mg/I. Preston selectice agar (Bolton and Robertson, 1982) consisted of Campyiobacter agar base (Oxoid CM 689), 5% (v/v) saponin-lysed horse blood and Campylobacter selective supplement (Oxoid SR l l7). In the quantitative analyses, the agar content was increased to 2% to prevent the spreading of Campylobacter colonies. Horse blood agar consisted of Blood Agar Base (Oxoid CM 271) and 5% (v/v) defibrinated horse blood. Incubation: all enrichment broth tubes and agar plates were incubated microaerobica!!y in anaerobic jars with palladium catalysts and Campy Pak (BBL). Broth tubes were incubated for 24 h at 42°C, after which selective agar plates were inoculated using cotton swabs and incubated for 48 h at 42°C. Presumptive Campylobacter colonies were Gram-stained and examined for motility by phase contrast microscopy. Gram-negative, curved bacteria which showed characteristic movements were considered as potential Campylobacters. Colonies of those isolates were subcuitured on horse blood agar plates. The colonies were tested for oxidase and catalase activity and positive isolates were considered to be C. jejuni/coli.
Results and Discussion
The incidence of Campylobacter in muscles was very low, only 9 out of 340 samples, i.e., 3% (data not shown). However, muscle contamination has potentially important implications for public health and should be further investigated. The
48 TABLE ! Number of C jejuni isolated from neck skins Experiment (flock) number
I 2 3 4 5 6 Total " h c d
Neck skin swab samples ~ Enrichment method
Neck skin swab samples ~ Quantitative method
Neck skin samples 10 g stomached Quantitative method
Pos "
(;i
Pos ;~
Number h
Pos ''
Number t,.c
16/19 I(1/10
84 1011 1(111 Illl) 511 911 89
19/19 6/1(I 20/20 0/11) d
2.4-+0.47 1.4-+0.66 2.5 -+ 0.58 < 2.11 1.2 _4-0.65
18/18
3.0+0.41
2(I/2(I Ill/Ill 5/!11 9/11t
70/79
9/10 N.I. t
9/10 18/19 N.I. N.1. 29/30
2.8_+_+0.44 3.4__+(I.38
2.7 -+ (I.44
Number p o s i t i v e / n u m b e r sampled. Mean log m colony forming units_+ standard deviation in the positive samples. A 4 cm 2 area sampled. Ix)west dilution investigated in this flock was I(1 -' Per gram sample. Not investigated.
numbers of C. fljuni ~col( found in neck skins are shown in Table 1, the numbers of positive scrapings of subcutaneous skin are shown in Table II, and those in peritoneal cavities and caecal contents are shown in Table i1I. The present study shows that if Campylobacter is present in the intestinal canals, broiler carcasses become extensively contaminated during the slaughter process. This has been reported earlier, as well as the stages of the slaughter process during which contamination occurs (Oosterom et al., 1983; Genigeorgis et al., 1986). However, an important consideration is whether deeper parts of the carcasses are contaminated to any degree. The number of subcutaneous samples
T A B L E 1I
Occurrence of C. jc'juni in subcutaneous scrapings (feather follicles) from poultry Experiment (flock) number
Enrichment method Pos a.c ~
Quantitative method Pos ,,.c
Number b
1 2 3 4 5 6 Total
17/2O 9/9 20/20 8/10 1/ 10 19/30 74/99
34/611 7/29 47/60 0/30 d 22/30 6/60
1.44 -+ 0.49 ! .08 +_0.23 !.6 ! _+(I.73 < 2.() 1.88 -t- 0.80 1.83 +_11.41
a.h.c.d See Table I.
85 I(10 1(10 8(1 10 63 75
49 TABLE 111 Number of ( \ jejuni isolated from peritoneal cavity and caecal contents Experiment
Peritoneal cavity swab samples "
Caecal content
(flock) number
Enrichment method
Quantitative method
Quantitative method
Pos ~'
c~
Pos"
Number i,
Pos ~
I 2 3 4 5 6 Total
19/20 I11110 21)/211 I0/I0 6/10 28/30 93 / 1110
95 I01) I IX) I00 61) 93 93
2t)/20 6110 20/211 9/10 2/10 10/30
3.0 -+11.39 2.7_+0.38 3.2 _+0.59 2.9_+0.67 3.4 -+0.47 2.3 _+0.37
20/20 N.I. 20/21) I0/I0 9/1(t 30/30
~,,h.~.d.f
See Table
d
Number h 7.5 + 0.91 7.2 + 1.46 8.1 -+0.56 5.8_+ 1.17 > 9.0
1.
showing growth of Campylobacter was high (75%, Table il), but the numbers of Carnpylobacter in these samples generally were low compared to numbers on the neck skin or in the peritoneal cavity. It is likely that the feather follicles are the orifice through which C. jejuni/coli is introduced into the subcutis layer. The scalding procedure is used to open the feather follicles in order to facilitate the removal of feathers. The follicles might remain open throughout the processing until the carcass is chilled. When the follicles close during chilling, the microorganisms will be retained. Methods to reduce contamination of carcasses by treating the body surfaces with disinfectants duriog scalding have been suggested by Okrend et al. 11986) and Hudson and Mead (1987). It seems, however, unlikely that a disinfectant washed or sprayed over a carcass wc~,lel penetrate all the feather follicles. Even if a surface flora of Campylobacter could be diminished by a disinfectant, thus reducing the risk of cross contamination, Campylobacters hidden in deeper subcutaneous layers might survive the treatment. Due to the low infectious dose in humans, these Campylobacters can cause illness if the chicken is not properly heated during cooking. Removal of the skin before cooking would lower the amount of contamination on the carcass, but the relatively large number of Campylobacters found on the peritoneal cavity surfaces will still remain a risk, especially if the chicken is cooked without being divided into halves or parts before cooking.
Acknowledgements We thank Gunny Blomgren for excellent technical assistance. This work was financially supported by the Swedish Poultry Association and the Swedish Council for Forestry and Agricultural Research.
5O
References Altmeyer, M.. Krabisch. P. and Dorn. P. (1985) Zum Vorkommen und zur Verbreilung yon CampyIobacterjejuni/coli in der JungmastgefliigeI-Produktion_ I. Mitteilung. Dtsch. tier';irztl. Wschr. 92, 456-459. Blaser, M.J., Taylor, D.N. and Feldman, R.A. (1983) Epidemiology of Campylobacterjejuni infections. Epidem, Rev. 5, 157-176. Bolton, F.J. and Robertson, L. (1982) A selective medium for isolating Campylobacter jejuni/coli. J. C!!a. Pathol. 35, 462-467. Genigeorgis, C., Hassuneh, M. and Collins, P. (1986) Campyh)bacter jejuni infection on poultry farms and its effect on poultry meat contamination during slaughtering. J. Food Protect. 49, 895-903. Hudson, W.R. and Mead. G.C. (1987) Factors affecting the survival of Campylobacter jejuni in relation to immersion scalding of poultry. Vet. Rec. 121,225-227. Okrend, A.J.. Johnston, R.W. and Moran, A.B. (1986) Effect of acetic acid on the death rates at 52°C of Salmonella newport, Salmonella typhimurium and Campylobacterjejuni in poultry scald water. J. Food Protect. 49. 500-503. Oosterom, J., Notermans, S., Karman, H. and Engels. G.B. (1983) Origin and prevalence of CampyIobacter jejuni in poultry processing. J. Food Protect. 46, 339-344. Skirrow. M.B. (1987)The twisted germ: Campylobacter. Publ, Hlth. !1)1, 159-163. Wempe, J.M., Genigeorgis, C.A., Farver, T.B. and Yusufu. H.1. (1983) Prevalence of Campylobacter jtjuni in two California chicken processing plants. Appl. Environ. Mielobiol. 45, 355-359.
