Occurrence and Genetic Diversity of Arcobacter butzleri in an Artisanal Dairy Plant in Italy

Abstract

bThe present study aimed to investigate the presence, distribution, and persistence of Arcobacter spp. in an artisanal dairy plant and to test the isolates to determine their different genotypes in the processing plant and in foods. Samples were collected in an artisanal cheese factory on four occasions between October and December 2012. Food samples (raw milk, ricotta cheese, mozzarella cheese, and conditioning liquid), water samples, and environmental samples were analyzed by the culture method; isolates were identified by multiplex PCR and genotyped by pulsed-field gel electrophoresis (PFGE) analysis. Arcobacter butzleri was isolated from 29 out of 59 samples (46.6%), 22 of which were from environmental samples and 7 of which were from food samples. Cluster analysis divided the strains into 47 PFGE patterns: 14 PFGE clusters and 33 unique types. Our findings indicate that the plant harbored numerous A. butzleri pulsotypes and that the manual cleaning and sanitation in the studied dairy plant do not effectively remove Arcobacter. The recurrent isolation of A. butzleri suggests that the environmental conditions in the dairy plant constitute a good ecological niche for the colonization of this microorganism. In some cases, the presence of indistinguishable strains isolated from the same facilities on different sampling days showed that these strains were persistent in the processing environment. Interest in arcobacters in veterinary and human public health has increased from the first report of the isolation of arcobacters from food of animal origin; since then, studies worldwide have reported the occurrence of arcobacters on food and in food production animals and have highlighted possible routes of transmission, especially for Arcobacter butzleri, to the human population (1).Arcobacter butzleri is the most important and prevalent species of the genus and has been classified as a serious hazard to human health by the International Commission on Microbiological Specifications for Foods (2) and as a significant zoonotic pathogen (3). A few surveys have investigated the presence of Arcobacter spp. in bulk tank raw cow's milk, reporting prevalence rates of 46% in Northern Ireland (4), 5.8% in Malaysia (5), and 48% in Italy (6). In Italy, A. butzleri was isolated in fecal samples and in-line milk filters on a water buffalo (WB) dairy farm (7,8). Consumption of Arcobacter-contaminated food or water is regarded as the most probable route of transmission to humans and animals (9) following fecal contamination during the various stages of production processes (10). In the Mediterranean countries, there is a widespread tradition of raw milk cheese production, including, particularly in Italy, WB cheeses. A. butzleri demonstrated the ability to survive during the production process and shelf life of WB mozzarella cheese (11), and raw milk cheeses may be considered a potential source of human infection even though A. butzleri has not been isolated from dairy products. A. butzleri contamination of food processing plants may...

Arcobacter butzleri in Sheep Ricotta Cheese at Retail and Related Sources of Contamination in an Industrial Dairy Plant

“…This study showed the occurrence of A. butzleri in the surfaces of the investigated dairy plant, in agreement with previous reports (10)(11)(12) in which A. butzleri was isolated from surfaces in contact with food and from surfaces not in contact with food both in artisanal and in industrial dairy plants; the plant surfaces were more frequently contaminated than food samples (33.3% versus 21%).…”

“…Although the present study did not investigate the primary source of dairy plant contamination, postprocess contamination was identified as the most probable source of ricotta cheese contamination, in agreement with a previous study (10). In fact, the survival of A. butzleri during the cheese manufacturing process can be excluded given the thermal treatment applied to produce ricotta cheese (heating at 80 to 82°C of a 1,500-liter vat of whey) and the thermal resistance of A. butzleri (33) that was reported to have a decimal reduction time at 55°C between 0.4 and 1.1 min and a Z value between 7.4 and 8.1°C, in the stationary and exponential phases, respectively.…”

“…other than A. butzleri was isolated in ricotta cheese and in the dairy plant; A. butzleri has been reported to be more resistant than other Arcobacter species in several substrates (8,26,32), and this may account for the more frequent isolation of A. butzleri both in milk and in dairy plants (10)(11)(12)(24)(25)(26). In addition, the isolation method used in this work may have affected the species of Arcobacter detected, as most of the isolation methods used are not optimal for all Arcobacter species (28).…”

“…In industrialized countries, the consumption and handling of raw or poorly cooked contaminated foods of animal origin have been implicated as important routes of Arcobacter transmission to humans (7), and the initial source seems to be fecal contamination during the various stages of production processes (8). However, Arcobacter contamination of food processing surfaces has been reported in poultry slaughterhouses, spinach processing plants, and dairy plants (9)(10)(11)(12)(13)(14)(15)(16)(17).…”

“…have been isolated in the dairy chain from fecal samples of dairy animals (18)(19)(20)(21)(22), from milk filters (23), and from raw milk (10,24,25). Recent investigations demonstrated the ability of A. butzleri and A. cryaerophilus to survive during the shelf life of dairy products (26,27), reporting isolation of A. butzleri in an artisanal ready-to-eat water buffalo ricotta cheese and in the environments of both artisanal and industrial dairy plants (10)(11)(12). In Italy, ricotta cheese is a widespread fresh or salted dairy product produced from whey resulting from the cheesemaking process, using milk of different animals.…”