Survival and reduction of strains of Campylobacter species in broiler meat

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Title: Survival and reduction of strains of Campylobacter species in broiler meat
Author: Isohanni, Pauliina
Publisher: Helsingin yliopisto Ruralia-instituutti
Date: 2013
Language: en
Belongs to series: Julkaisuja 30
ISBN: 978-952-10-8467-6
ISSN: 1796-0657
Abstract: Campylobacter, especially Campylobacter jejuni and C. coli, are reported as the most frequent cause of foodborne bacterial diarrhoea in humans worldwide. One of the most important sources of human campylobacteriosis is the eating or handling of improperly cooked or raw broiler meat. Between January and September 2006, 194 marinated and non-marinated poultry (broiler and turkey) meat products were collected from retail shops in Western Finland and tested for Campylobacter using conventional enrichment culture and Polymerase Chain Reaction (PCR) methods. For marinated poultry products, the study involved modification of a commercial DNA isolation method. Using either method, a total of 25 (12.9%) of all the samples were Campylobacter positive. In August, there was a peak with 28.9% positive samples. In marinated poultry products, Campylobacter was detected at a prevalence of 10.3%. Due to the high detection limit of the direct Campylobacter PCR method, it was necessary to perform a combination of enrichment and PCR. The effects of ultraviolet (UV) irradiation in reducing C. jejuni E1 1347 on the surfaces of broiler meat, skin and carcasses were studied. The surfaces were inoculated with varying counts of C. jejuni E1 1347 and treated with UV irradiation with doses ranging between 9.4 and 32.9 milliwatts per second per square centimetre (mWs/cm2). The log reductions in C. jejuni E1 1347 counts were determined by dilution plating. The effects of UV irradiation on the sensory quality of broiler meat were also evaluated. The maximum reduction achieved was 0.7 log on broiler meat, 0.8 log on broiler skin and 0.5 log on carcasses. UV irradiation did not affect the sensory quality of broiler meat. The survival of high (7 log cfu/ml) and low (3 log cfu/ml) inocula levels of Campylobacter strains RefCJ, RetCJ29, RetCC27 and SlaCJ26 was studied in white and red wines, and in grape and tomato juices. For comparison, survival was studied in a commercial poultry meat marinade. The log reductions were determined by dilution plating. High counts of the bacteria were rapidly inactivated to undetectable numbers within 15 min in white wine and within 1 h in red wine, and low counts within 15 min in white wine and within 30 min in red wine. In grape and tomato juices even low counts of the bacteria were occasionally detected after 48 h. In the commercial marinade the high bacterial counts were inactivated in most cases within 48 h and all the low counts within 3 h. When Campylobacter strains RefCJ and RetCC27 were inoculated on broiler meat, wines reduced the bacterial counts by approximately 1 log cfu/ml over 48 h. Arcobacter are close phylogenetic relatives of Campylobacter that have occurred in broiler meat and have been linked with human illness (mainly diarrhoea). Sublethal stress adaptation temperatures (48ºC and 10ºC) and mild and lethal acid conditions (pH 5.0 and pH 4.0) were determined for A. butzleri ATCC 49616 and C. jejuni NCTC 11168. In addition, it was evaluated whether incubation under the sublethal stress conditions causes specific adaptive responses or cross-protection against subsequent mild or lethal acid stresses in these bacteria. The studies were conducted in broth adjusted to the different conditions and the results were determined by dilution plating. During this study, cross-protection is reported for A. butzleri for the first time. Heat stress adapted A. butzleri ATCC 49616 (incubated for 2 h at 48ºC) were significantly more resistant to subsequent lethal acid stress (pH 4.0) than non-adapted cells at the 1 h time-point (P < 0.01). No specific adaptive responses in the bacteria and no cross-protection in C. jejuni NCTC 11168 were found. In conclusion, there is a seasonal peak in the prevalence of Campylobacter in Finnish poultry meat products, but otherwise the prevalence is low. Campylobacter detection in marinated poultry products indicates that marinating meat might not affect the survival of Campylobacter. The PCR assay together with the optimized DNA isolation method is faster than microbiological analyses and could be used for Campylobacter-detection in marinated meat samples. Due to the low infective dose of C. jejuni in humans and the modest reductions achieved for the strains of Campylobacter species studied, the use of UV irradiation or wines and juices as antimicrobial marinade ingredients cannot be recommended as the primary decontamination methods to control Campylobacter in broiler meat, but might be used as part of a sequential risk reduction strategy to reduce the counts of Campylobacter. The cross-protection phenomenon found for A. butzleri ATCC 49616 should be taken into account when designing food preservation strategies containing these conditions. To further evaluate the significance of poultry meat as a source of Campylobacter in Finland, their occurrence in the meat products should be quantified. Despite the attempts of this study no sufficiently effective way to reduce the counts of Campylobacter in broiler meat was found and further decontamination methods should be studied in the future. Moreover, the cross-protective effect should be investigated further at the gene expression level in order to elucidate the molecular mechanisms behind this phenomenon reported.

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