Bacteria may adhere to and develop biofilm structures onto dairy surfaces trying to protect themselves from adverse conditions such as pasteurization and CIP processes. Thus, biofilms are considered common sources of food contamination with undesirable bacteria. The purpose of this study was to evaluate the diversity of the microbiota attached to stainless steel surfaces in pre-and post-pasteurization pipe lines of a milk-processing plant. Seventy Gram-positive isolates were identified as Enterococcus faecalis (33), Bacillus cereus (26), Staphylococcus hominis (8), Staphylococcus saprophyticus (2), and Staphylococcus epidermidis-Staphylococcus aureus (1) species. Fifty-five Gram-negative isolates were identified to the species Escherichia coli (18), Klebsiella pneumoniae (13), Acinetobacter calcoaceticus (6), Serratia marcescens (6), Enterobacter spp. (5), Pseudomonas aeruginosa (4), Escherichia vulneris (2), and Proteus mirabilis (1). Fifty-five different strains were detected by the RAPD technique. These were subjected to an in vitro assay to evaluate their biofilm-forming capability. E. faecalis (7), A. calcoaceticus (4), K. pneumoniae (3), S. hominis (3), and P. aeruginosa (2) were the species in which more biofilm producer strains were encountered. The adhered microbiota was also assessed by the PCR-DGGE culture-independent technique. This analysis revealed a greater bacterial diversity than that revealed by culturing methods. In this way, in addition to the bacteria detected by culturing, DNA bands belonging to the genera Chrysobacterium and Streptomyces were also identified. This study emphasizes that knowledge of attached Dairy Sci. & Technol. (2016) 96:27-38 DOI 10.1007
Staphylococcus aureus is an opportunistic bacterium causing a wide variety of diseases. Biofilm formation of Staphylococcus aureus is of primary public and animal health concern. The purposes of the present study were to investigate the ability of Staphylococcus aureus isolated from animals, humans, and food samples to form biofilms and to screen for the presence of biofilm-associated and regulatory genes. In total, 55 Staphylococcus aureus isolated from sheep mastitis cases (n = 28), humans (n = 19), and from food matrices (n = 8) were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The ability of Staphylococcus aureus for slime production and biofilm formation was determined quantitatively. A DNA microarray examination was performed to detect adhesion genes (icaACD and biofilm-associated protein gene (bap)), genes encoding microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), regulatory genes (accessory gene regulator (agr) and staphylococcal accessory regulator (sarA)), and the staphylococcal cassette chromosome mec elements (SCCmec). Out of 55 Staphylococcus aureus isolates, 39 (71.0%) and 23 (41.8%) were producing slime and biofilm, respectively. All Staphylococcus aureus strains isolated from food showed biofilm formation ability. 52.6% of the Staphylococcus aureus strains isolated from sheep with mastitis, and 17.9% of isolates from humans, were able to form a biofilm. Microarray analysis typed the Staphylococcus aureus into 15 clonal complexes. Among all Staphylococcus aureus isolates, four of the human isolates (21.1%) harbored the mecA gene (SCCmec type IV) typed into 2 clonal complexes (CC22-MRSA-IV and CC80-MRSA-IV) and were considered as methicillin-resistant, while two of them were slime-producing. None of the isolates from sheep with mastitis harbored the cna gene which is associated with biofilm production. The fnbB gene was found in 100%, 60% and 40% of biofilm-producing Staphylococcus aureus isolated from food, humans, and sheep with mastitis, respectively. Three agr groups were present and agr group III was predominant with 43.6%, followed by agr group I (38.2%), and agr group II (18.2%). This study revealed the capacity of Staphylococcus aureus isolates to form biofilms and highlighted the genetic background displayed by Staphylococcus aureus isolates from different sources in Algeria.
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Bacillus cereus spores have the ability to adhere to solid surfaces, including stainless steel, a material widely used in food industries. Adhesion of spores allows for recontamination during food processing, and the cleaning and disinfection are largely used by industries to control them. Hence, this study aims to assess the detachment capacity (or removing activity) of sodium hydroxide, nitric acid, phosphoric acid-based detergent, chlorine-based detergent; against two adhered Bacillus cereus spores (hydrophobic strain and hydrophilic strain) to stainless steel surfaces. Microorganism adhesion on the surfaces reached 5.5 log CFU/cm² the two strain studied. Two protocols composed of combinations of chemical compounds concentration, temperature, and contact time were tested. The inactivation kinetics shapes were convex and were modelled by the Weibull model. The effect of temperature and biocide concentration were quantified using a Bigelow like model. The temperature applied during of treatment of the cleaning in place is an important factor acting on the speed of inactivation or detachment of Bacillus cereus spores. However, this efficiency depends on the hydrophobic characteristics of Bacillus cereus spores. The concentration of detergent and acid also affects the inactivation rate. The inactivation rate, whereas the character of hydrophobic does not intervene for the chlorine alkaline treatments.
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