RESUMO
Listeria monocytogenes is one of the most severe foodborne pathogens found in several habitats. Therefore, this study aims to investigate the antilisterial activity of different essential oils (EOs) against multidrug-resistant (MDR) L. monocytogenes strains isolated from fresh chicken meat. Our results showed that the prevalence of L. monocytogenes in the examined samples was 48%. Seventy-eight isolates were identified as L. monocytogenes. Out of these, 64.1% were categorized as MDR and were categorized in 18 patterns with 50 MDR isolates. One isolate was selected randomly from each pattern to investigate their biofilm-forming ability, resistance, and virulence genes incidence. Out of 18 MDR isolates, 88.9% showed biofilm-forming ability. Moreover, the most prevalent resistance genes were ermB (72%), aadA (67%), penA (61%), and floR genes (61%). However, the most prevalent virulence genes were inlA (94.4%), prfA (88.9%), plcB (83.3%), and actaA (83.3%). The antilisterial activity of EOs showed that cinnamon bark oil (CBO) was the most effective antilisterial agent. CBO activity could be attributed to the bioactivity of cinnamaldehyde which effects cell viability by increasing the bacterial cell electrical conductivity, ion leakage, and salt tolerance capacity loss. Therefore, CBO could be an effective alternative natural agent for food safety applications.
RESUMO
This study was conducted to determine the concentration and frequency distribution of certain airborne micro-organisms on cattle farms and their potential health hazards to farm workers. The samples (60 air samples and 240 hand and nasal swabs from cattle farm workers) were collected from ten cattle farms (five dairy barns and five beef sheds) located in the Sharkia Governorate of Egypt. Air samples were collected for microbiological examination in liquid media using an all-glass impinger whereas those for fungal examination were placed on agar plates using slit air samplers (aeroscopes). The results showed that the overall means of total culturable bacterial and fungal counts were lower in the air of dairy cattle barns than in beef cattle sheds. Identification of the isolated bacteria revealed the recovery of the following species (from dairy cattle barns versus beef cattle sheds): Staphylococcus epidermidis (26.7% vs 36.7%), S. saprophyticus (20% vs 33.3%), S. aureus (10% vs 16.7%), Enterococcus faecalis (23.3% vs 26.7%), Enterobacter agglomerans (23.3 vs 13.3%), Escherichia coli, (16.7% vs 26.7%), Klebsiella oxytoca, (10% vs 16.7%), K. pneumoniae (3.3% vs 0%), Proteus rettegri (6.7% vs 13.3%), P. mirabilis (10% vs 10%), P. vulgaris (3.3% vs 6.7%), Pseudomonas species (6.7% vs 16.7%), respectively). Mycological examination of air samples revealed the presence of Aspergillus fumigatus (46.7% vs 63.3%), A. niger (20% vs 36.7%), A. flavus (13.3% vs 26.7%), Penicillium citrinum (16.7% vs 23.3%), P. viridicatum (13.3% vs 6.7%), P. capsulatum (3.3% vs 0%), Cladosporium spp. (30% vs 56.7%), Alternaria spp. (13.3 vs 23.3%), Mucor spp. (6.7% vs 16.7%), Fusarium spp. (3.3% vs 10%), Absidia spp. (6.7% vs 10%), Curvilaria spp. (10% vs 3.3%), Rhizopus spp. (6.7% vs 13.3%), Scopulariopsis (3.3% vs 6.7%), Epicoccum spp. (0% vs 3.4%) and yeast (13.3% vs 20%), respectively. In addition, microbiological examinations of farm workers revealed heavy contamination of their hands and noses with most of the micro-organisms detected in the air of cattle farms. The results showed that potential airborne microbial risks in beef cattle sheds were greater than in dairies.