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This study evaluated the susceptibility of planktonic and biofilm cells of Staphylococcus spp. (n = 87), Klebsiella spp. (n = 30), and Escherichia coli (n = 74) isolates originating from food contact surfaces of milk and meat processing plants to benzalkonium chloride (BAC), sodium hypochlorite (NaClO), chloramine B (CAB), and peracetic acid (PAA). Bacterial growth and reduction of viable cells in the presence of disinfectants were determined in tryptone soya broth (TSB) and water, respectively. Biofilm positive isolates (n = 73) were tested for the presence of selected qac genes. Unlike BAC, chlorine-based disinfectants and PAA were poorly efficient in TSB, especially in the case of biofilms. However, when tested in water, the efficacy of NaClO, CAB and PAA substantially increased, which was particularly evident in biofilms. In water, staphylococcal biofilms were even more susceptible to CAB than planktonic cells. A part (23.3%) of the biofilm positive staphylococci carried the qac genes but did not express an increased resistance to BAC. This study showed that bacterial biofilms protected with organic matter could be one of the main reasons for disinfection failure.

The occurrence of Listeria monocytogenes, Salmonella spp., Bacillus cereus, Staphylococcus spp., Enterococcus spp., and Escherichia coli in raw food materials, food products, and on food contact surfaces after sanitation was investigated during the period of 2005-2006 in three dairy cattle farms (120 samples), one dairy (124 samples), and two meat processing plants (160 samples). A total of 1,409 isolates were identified. The epidemiological characterisation and determination of the virulence factors and antimicrobial resistance were performed on selected isolates. The level of bacterial contamination generally decreased during the production process (the contamination of food products was lower than that of raw material). However, the contamination of food contact surfaces was relatively high even after sanitation. Moreover, specific microbiological profiles were found on the inside equipment surfaces in dairy facilities, where genetically closely related multi-resistant strains persisting in biofilm communities may occur as it was demonstrated for staphylococci. Although the occurrence of potentially significant pathogens was not high, the microorganisms such as L. monocytogenes, Salmonella spp., and shiga-toxin positive E. coli principally contaminated the meat processing plants. B. cereus isolates, among which 76% were positive for diarrhogenic enterotoxin, typically occurred on the inside equipment surfaces and in the heat-treated products.

Eight individual bacteriocin-producing lactic acid bacteria (LAB) strains and three bacteriocin-non-producing cheese starter cultures were evaluated for their ability to inhibit the growth of six Listeria monocytogenes strains, originating from the guinea-pig lymph nodes, raw cow milk, and manufacturing dairy equipment. Results showed that either live cells or cell-free neutralised supernatant (CFNS) and/or heated CFNS of six individual LAB strains (Lcc. lactis subsp. lactis CCDM 416 and NIZO R5, Lbc. plantarum HV 11 and DC 1246, P. acidilactici HV 12, and Ent. mundtii CCM 1282) and one starter culture (DELVO-ADD 100-X DSF) were effective in the suppression of at least one listeria strain. Neither any individual LAB strain nor starter culture was antagonistic toward all studied L. monocytogenes strains, indicating diverse sensitivity/resistance among L. monocytogenes strains to antimicrobial compounds of LAB. The significant susceptibility of listerias isolated from raw milk and dairy equipment together with the strong antilisterial activity of DELVO-ADD 100-X DSF could be applied in dairy technology, where commonly used starter cultures could play both the biopreservative and fermentation role.

Isolates from farm to fork samples (182 isolates from 2,779 samples of raw meat and milk, meat and milk products, contact surfaces in meat and dairy processing plants) were examined genotypically (icaAB genes) and phenotypically (in vitro biofilm formation, typical growth on Congo red agar, CRA) with the aim to assess the risk of penetration of virulent strains of Staphylococcus epidermidis into the food chain. The contamination of meat and milk products was significantly higher in comparison with raw materials. The contamination of contact surfaces in meat processing plants was significantly lower than that in dairy plants. The ica genes (which precondition the biofilm formation) were concurrently detected in 20 isolates that also showed a typical growth on CRA. Two ica operon-negative isolates produced a biofilm in vitro but perhaps by an ica-independent mechanism. Samples from contact surfaces in dairy plants and milk products were more frequently contaminated with ica operon-positive strains (2.3 and 1.2%, resp.) than the other sample types (0-0.6%).

The microbiological quality of the final product and the safety of the production procedures were screened in an ice cream factory, after implementation of a Hazard Analysis Critical Control Points (HACCP) system. We analysed 30 vanilla (IC1), 30 strawberry (IC2), and 30 chocolate flavoured (IC3) samples of ice cream, 30 samples of water; 90 of personnel's hands flora, 150 of plastic ice cream containers flora, and 50 of sanitised equipment-surfaces flora. After HACCP introduction, Staphylococcus aureus was not further detectable in ice cream and Escherichia coli was mostly less than 10 CFU/g, while the spoilage markers (total coliforms - TC, aerobic plate counts - APC) in ice cream and the environment were reduced by 20-35%. Mean log CFU/g decreased as follows: for IC1: TC from 2.20 to 1.57, APC from 4.58 to 3.62; for IC2: TC from 2.29 to 1.65, APC from 4.61 to 3.49; for IC3: TC from 2.67 to 1.76, APC from 5.08 to 3.81.

Listeria strains isolated over the past 10 years from farms and dairy processing environments were subjected to strain-specific ribotyping using the automated Riboprinter microbial characterization system, alpha version (E.I. duPont de Nemours and Co., Inc.). A total of 388 Listeria isolates from 20 different dairy processing facilities were examined along with 44 silage, 14 raw milk bulk tank, and 29 dairy cattle (26 udder quarter milk, 1 brain, 1 liver, and 1 aborted fetus) isolates. These 475 isolates included 93 L. monocytogenes, 362 L. innocua, 11 L. welshimeri, 6 L. seeligeri, 2 L. grayi, and 1 L. ivanovii strains. Thirty-seven different Listeria ribotypes (RTs) comprising 16 L. monocytogenes (including five known clinical RTs responsible for foodborne listeriosis), 12 L. innocua, 5 L. welshimeri, 2 L. seeligeri, 1 L. ivanovii, and 1 L. grayi were identified. Greatest diversity was seen among isolates from dairy processing facilities with 14 of 16 (87.5%) of the L. monocytogenes RTs (including five clinical RTs) and 19 of 21 (90.5%) of the non-L. monocytogenes RTs detected. Sixty-five of the 93 L. monocytogenes isolates belonged to a group of five clinical RTs. These five clinical RTs included one RT unique to dairy processing environments, two RTs common to dairy processing environments and silage, and one RT common to dairy processing environments, silage, and dairy cattle with the last RT appearing in dairy processing environments, silage, raw milk bulk tanks, and dairy cattle. These findings, which support the link between on-farm sources of Listeria contamination (dairy cattle, raw milk, silage) and subsequent contamination of dairy processing environments, stress the importance of farm-based HACCP programs for controlling listeriae

In Sardinia, ewe's milk is almost exclusively used for cheese manufacture, and it is usually processed in small dairies which do not have sufficient technical and scientific knowledge for large-scale controlled production. This study was carried out to identify the sources of contamination and the kinds of contaminating microorganisms present in six ewe's milk processing plants in Sardinia. Samples were collected during production hours three times over a period of 6 months. Raw milk, heat-treated milk, curd, 30-day-old cheese, lactic culture, rennet, and water used in processing lines were analyzed and the microbial contamination of air and surfaces was evaluated. Total mesophilic aerobic counts, coliforms, Escherichia coli, gram-negative psychrotrophs, Staphylococcus aureus, Salmonella spp., Listeria spp., yeasts, and molds were determined. Our survey confirmed that the production of food of high microbiological quality is strictly dependent on the microbiological quality of the raw material, optimization of the parameters for the heat treatment, water of potable quality, well-defined cleaning and disinfection procedures, and hygienic processing conditions. In fact, only plants characterized by raw milk and rennet of acceptable quality, generally clean work surfaces, and low microbial counts in the air of working areas made finished products of high microbiological quality. Standardization of technological parameters and achievement of properly hygienic processing conditions will help minimize the risk of developing food-safety problems, in compliance with public health regulatory requirements. These actions would help guarantee an adequate quality of Sardinian ewe's milk cheeses and might also lead to access to the international market