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.

Bacillus cereus is a ubiquitous spore-forming bacterium causing food spoilage. In this study, seventeen B. cereus were isolated from dairy processing equipment in Algeria and characterized. The pathogenic potential genes encoding hemolysin, nonhaemolytic enterotoxin, cytotoxin K and emetic toxin were investigated by PCR. Phylogeny and genetic markers for antimicrobial resistance and virulence were analyzed using whole-genome sequencing data using the Illumina MiSeq technology. The identity of the isolated strains was confirmed as B. cereus sensu lato and the sequencing of the panC gene clustered 64.7 of them in phylogenetic group III and 35.3 in group IV. The results of PFGE showed that 8 (47.1), 4 (23.5), 3 (17.6) and 2 (11.8) were differentiated into four groups A, B, C and D, respectively. Each of the two panC phylogenetic groups contains two different types of isolates corresponding to PFGE group (A and C) and (B and D) for phylogenetic groups III and IV, respectively. None of the 14 isolates carried the emetic toxin (ces) gene, whereas other toxin genes were variably detected. Genotyping assigned all isolates to three different sequence types (ST 2226, ST1018 and ST1431) while one clonal complex (CC-142) was identified in three isolates. Hierarchical clustering with a threshold of 500 core genome single nucleotide polymorphism (cgSNPs) differences grouped the strains into three clusters while two strains were less than 20 SNPs different. Three B. cereus (25) contained three enterotoxic HBL complex-encoding genes hblA/C/D. Enterotoxic NHE complex-encoding genes (nheA/B/C) and the ctyK1 gene were detected in all isolates. The overall results highlight the risk due to toxins produced by the B. cereus group in the food safety and dairy industries in Algeria. This study emphasized the potential of whole-genome sequencing for genotyping and predicting the virulence-associated genes and antimicrobial resistance. The present study will help to better assess the health and spoilage risk associated with B. cereus in dairy processing plants and to incorporate adequate preventive measures.

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 recontamination during food processing, and cleaning and disinfection are largely used by industries to control them. Hence, this study aims to assess the detachment capacity (or removing activity) of detergents based on sodium hydroxide, nitric acid, phosphoric acid, and chlorine against two adhered B. cereus spores (one hydrophobic and other hydrophilic) to stainless steel surfaces. Microorganism adhesion on the surfaces reached 5.5 log CFU/cm2 for the two strains studied. Two protocols composed of combinations of chemical compounds, concentration, temperature, and contact time were tested. The inactivation kinetics shapes were convex and modeled by the Weibull model. The effects of temperature and biocide concentration were quantified using a Bigelow-like model. The temperature applied during the cleaning-in-place treatment is an important factor acting on the speed of inactivation or detachment of B. cereus spores. However, this efficiency depends on the hydrophobic characteristics of B. cereus spores. The concentration of detergent and acid also affects the inactivation rate, whereas the characteristic of hydrophobicity does not intervene for the chlorine alkaline treatments.HIGHLIGHTSAll tested combinations cannot effectively remove adhered spores.Chlorine-based was more efficient than phosphoric acid–based detergent at very low concentrations.Hydrophilicity or hydrophobicity is related to detachment ability of stainless steel–adhered spores.

The global dairy industry faces challenges in sourcing cost-effective and suitable lactic starters for traditional cheese production. This study investigates the use of locally selected lactic starters in crafting Algerian Jben cheese, aiming to provide a sustainable alternative to imported starters. Local lactic starters comprising Lactococcus lactis, Leuconostoc mesenteroides, and Enterococcus durans were characterized by their technological properties when applied to cow's milk. The resulting cheese was compared with another cheese produced under similar conditions but using an industrial mesophilic starter, including strains of Lactococcus and Leuconostoc. Physicochemical and microbiological analyses were conducted on both cheeses, followed by sensory evaluations using the triangular and classification tests. Microbiological analyses revealed the absence of pathogenic germs or spores in both types of cheese. However, the cheese made with the industrial starter exceeded the standards for fecal coliforms and total coliforms. Titratable acidity measurements indicated comparable levels in both cheeses. Interestingly, there were no discernible differences in taste or aroma between the two types, with both being well received by tasters. In conclusion, our findings suggest that local lactic starters have the potential to replace the commercial starters currently employed in the Algerian dairy industry.

Staphylococcus aureus colonizes the skin and nasal orifices of both humans and animals. Biofilm-related infections and acquired antimicrobial resistance render this bacterium a major health concern. This study examined the biofilm-forming capacity of eight S. aureus isolates originating from humans, sheep, and food matrices in northern Algeria. The efficiency of sanitizers (povidone–iodine [PVI], peracetic acid [PAA], quaternary ammonium compounds [QACs] and chlorhexidine [CHX]) in inhibiting and detaching biofilms was also assessed. Biofilm-production ability was assessed using a tissue culture plate. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration were measured for each sanitizer, and antibiotic susceptibility profiles were determined by performing the Kirby-Bauer disk diffusion assay. All S. aureus isolates demonstrated the ability to produce biofilms, and among these, food and sheep mastitis isolates exhibited a strong capacity for biofilm formation. CHX exhibited the highest efficacy in bacterial biofilm inhibition and was considered more potent than the other sanitizers (P < 0.0001). Further, it exhibited lower MIC interval values (0.98-1.9 µg/g). However, MIC interval values for PVI, PAA, and QACs were 3125-25000, 39.06-156.25, and 0.98-3.9 mg/L, respectively. PVI did not affect biofilm detachment at different concentrations. All isolates were sensitive to methicillin (with mecA/mecC genes not detected), gentamicin, sulfamethoxazole–trimethoprim, vancomycin, and amikacin; however, two isolates were resistant to erythromycin and clindamycin. These findings demonstrated the biofilm-forming potential of S. aureus isolates and confirmed the effectiveness of sanitizers against S. aureus isolated from different sources.