This study evaluated the occurrence of L. monocytogenes in the processing environment of a butcher shop, and the in vitro adhesion capacity and sensitivity of isolates to two sanitizers: A (Mister MaxDG1, chlorine based) and B (B-Quart Sept, quaternary ammonium based). Of the total of 40 samples, 75% were positive for Listeria spp. and 22.5% for L. monocytogenes. 20 isolates were from serogroup 1/2c or 3c, with positive results for all tested virulence genes. All isolates presented adhesion potential. The evaluated sanitizers had the potential to inhibit isolates growth and adhesion, and removed formed biofilms. After evaluation, the sanitizers were adopted by the butcher shop in its sanitation routine, being effective against L. monocytogenes. Collected data allowed identification of adhesion potential by L. monocytogenes and the effectiveness of the tested sanitizers to control contamination by this pathogen. Practical applicationsThe presented study shows the adhesion potential of L. monocytogenes, as well as the resistance of isolates to chlorine and quaternary ammonium based sanitizers, relevant to food facilities cleaning. Finally, we demonstrated the effects of chlorine and quaternary ammonium sanitizers activity on L. monocytogenes biofilm, leading further procedures to avoid adhesion.
Listeria monocytogenes contamination was assessed in different steps of a pork production chain. Ten lots of pigs were sampled at termination barns, at slaughter (after bleeding, after buckling, after evisceration, and after final washing), at processing (knives, deboning tables, and employees' hands), and of end products (ribs, shoulder, ham, and sausage). All samples (n = 670) were subjected to L. monocytogenes detection, and the obtained isolates (n = 18, identified as Listeria spp.) were characterized by their biochemical characteristics, serogroups, virulence genes, pulsed-field gel electrophoresis profiles, antibiotic resistances (ampicillin, penicillin, gentamicin, and sulfamethoxazole-trimethoprim), and adhesion abilities. The results revealed the low occurrence of Listeria spp. in the evaluated pork production chain. However, four tested sausage samples (40%) were positive for Listeria spp., with L. monocytogenes identified in two (20%) of these samples. Ten isolates were identified as L. monocytogenes (eight from serogroup 1/2a or 3a and two from serogroup 4b, 4d, or 4e): all isolates were also positive for the virulence-related genes hlyA, iap, plcA, actA, inlA, inlB, inlC, and inlJ and susceptible to the tested antibiotics. One sausage sample was contaminated by both serogroups 1/2a or 3a and 4b, 4d, or 4e. Isolates from serogroup 1/2a or 3a obtained during visits 5 and 6 presented distinct genetic profiles by pulsed-field gel electrophoresis, indicating that contamination may come from different sources. The adhesion potential exhibited by Listeria spp. isolates (n = 18) ranged from weak (serogroup 4b, 4d, or 4e) to moderate (L. innocua and L. monocytogenes serogroup 1/2a or 3a). Despite the low occurrence of L. monocytogenes, pathogenic serogroups were detected in sausages, demanding control measures by the industry. HIGHLIGHTS
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