Genomic characterization of the most barotolerant Listeria monocytogenes RO15 strain compared to reference strains used to evaluate food high pressure processing

BackgroundHigh pressure processing (HPP; i.e. 100-600MPa pressure depending on product) is a non-thermal preservation technique adopted by the food industry to decrease significantly foodborne pathogens, including Listeria monocytogenes, from food. However, susceptibility towards pressure differs among diverse strains of L. monocytogenes and it is unclear if this is due to their intrinsic characteristics related to genomic content. Here, we tested the barotolerance of 10 different L. monocytogenes strains, from food and food processing environments and widely used reference strains including clinical isolate, to pressure treatments with 400 and 600MPa. Genome sequencing and genome comparison of the tested L. monocytogenes strains were performed to investigate the relation between genomic profile and pressure tolerance.ResultsNone of the tested strains were tolerant to 600MPa. A reduction of more than 5 log(10) was observed for all strains after 1min 600MPa pressure treatment. L. monocytogenes strain RO15 showed no significant reduction in viable cell counts after 400MPa for 1min and was therefore defined as barotolerant. Genome analysis of so far unsequenced L. monocytogenes strain RO15, 2HF33, MB5, AB199, AB120, C7, and RO4 allowed us to compare the gene content of all strains tested. This revealed that the three most pressure tolerant strains had more than one CRISPR system with self-targeting spacers. Furthermore, several anti-CRISPR genes were detected in these strains. Pan-genome analysis showed that 10 prophage genes were significantly associated with the three most barotolerant strains.ConclusionsL. monocytogenes strain RO15 was the most pressure tolerant among the selected strains. Genome comparison suggests that there might be a relationship between prophages and pressure tolerance in L. monocytogenes.Peer reviewe

Characterization of clinical and food Listeria monocytogenes isolates with different antibiotic resistance patterns through simulated gastrointestinal tract conditions and environmental stresses

Thirty-three Listeria monocytogenes isolates previously collected from two sources, food (n = 18) and human patients suffering from listeriosis (n = 15), with variable antibiotic susceptibility profiles (sensitive/resistant) to erythromycin, ciprofloxacin and nitrofurantoin, were studied for their ability to survive (i) the environmental stress provided by sequential conditions that simulate the digestive tract, and (ii) extreme pH values (1.5–12). The results showed a response that was only strain dependent. There were no variability in survival results based on type of stress (low or high pH), source (food or clinical), or sensitivity/resistance to antibiotics (p > 0.01). Some strains of L. monocytogenes are able to survive extreme acid and alkaline conditions, and conditions that mimic the sequential stressors found in the gastro-intestinal tract. The resistance to the antibiotics tested in this study by some L. monocytogenes strains did not confer any cross-protection to acid or alkaline stressors.his work was supported by funding from the National Funds from the Fundação para a Ciência e a Tecnologia (FCT) through project Pest-OE/EQB/LA0016/2013 and “KLEAR - Knowledge and tools for safety, quality and competitiveness in the food chain.” n º NORTE-07-0124-FEDER-000052, co-funded by Fundo Europeu de Desenvolvimento Regional (FEDER), under Programa ON2, Eixo Prior- itário 01-01 – Competitividade, Inovação e Conhecimento, Tipologia 01-01-01-24 – Apoio a Entidades do Sistema Científico e Tecnológico. Financial support for authors Rui Magalhães and Vânia Ferreira was provided by FCT through doctoral fellowship SFRH/BD/71704/2010 and postdoctoral fellowship SFRH/BPD/72617/2010, respectively. Editing of this paper by Dr. P. A. Gibbs is gratefully acknowledge

Prevalence of staphylococcus aureus from nares and hands on health care professionals in a portuguese hospital

Aims: The main goal was to estimate the prevalence of methicillin-resistant Staphylococcus aureus on hands and in nose of health care professionals. Methods and Results: Detection of Staph. aureus on hands or in the nose of 169 individuals was performed. Nasal and hand carriage was found in 39 6 and in 8 9% respectively. About 17 2% of the individuals were carriers of methicillin-resistant Staph. aureus (MRSA) in the nose and 4 7% on hands. The majority of nasal MRSA were resistant to b-lactams, erythromycin and ciprofloxacin. All nasal MRSA were SCCmec type IV and Panton-Valentine leukocidin (PVL) negative. One MRSA isolated from hand was SCCmec type V. About 75 6% of MRSA isolates presented the same or closely related restriction patterns. Sixty per cent of Staph. aureus from hands and from noses from the same individual were the same strain. Conclusions: MRSA nasal carriage was high considering healthy health care professionals but in accordance with high level of MRSA infection in Portugal. Isolates recovered in this study seemed to be different from major clones previously isolated in other Portuguese hospitals. Significance and Impact of the Study: These findings may have implications on the knowledge of healthy health care workers as vehicles of MRSA infections among the community. Presence of several virulence factors may contribute to increased pathogenesis in case of infection.info:eu-repo/semantics/publishedVersio