The effect of blood on the ability of biofilm formation by Listeria monocytogenes strains

Introduction: Listeria monocytogenes strains are widespread in the natural environment and are the etiological factor of listeriosis. Food is the main source of L. monocytogenes. Secondary contamination of food products which results from the formation of biofilm by L. monocytogenes on the surfaces of the processing devices makes an essential problem. Material and methods: We evaluated the ability of biofilm formation in media supplemented with sheep blood (in a volume of 5.0, 10.0, 20.0 and 50.0%) for the reference strain L. monocytogenes ATCC 7644 and strains isolated from the human blood and carrots on the polypropylene surface. Results: The strain isolated from blood most efficiently formed a biofilm with increasing blood sheep’s addition (nutrient broth — 4.87 × 105 CFU × cm-2, blood supplement 50.0% (v/v) — 3.4 × 107 CFU × cm-2).The number of L. monocytogenes recovered from the biofilm for the reference strain and the strain from carrot increased to 20.0% by volume of the blood addition (3.07 × 105 CFU × cm-2 and 4.03 × 105 CFU × cm-2 respectively — nutrient broth; 1.1 × 107 CFU × cm-2 and 9.23 × 106 CFU × cm-2 — blood supplement 20.0% (v/v)). Decrease in the number of cells recovered from the biofilm for the reference strain and the one isolated from carrot has been demonstrated at 50.0% addition of blood into nutrient medium (8.8 × 106 CFU × cm-2 and 7.87 × 106 CFU × cm-2 respectively). Conclusion: The addition of sheep blood to the medium at concentrations up to 20.0% increases the number of cells recovered from the biofilm for all studied L. monocytogenes strains whereas medium with 50.0% blood stimulates the biofilm formation only by the strain isolated from blood

Assessment of drug susceptibility and biofilm formation ability by clinical strains of Listeria monocytogenes

BACKGROUND: Listeria monocytogenes is a cause of listeriosis, dangerous especially for elderly, immunocompromised people and pregnant women. Ability to colonize biotic and abiotic surfaces and form biofilm by these pathogens poses a serious threat for the hospitalized, catheterized patients. METHODS: The study was conducted on 29 L. monocytogenes strains isolated from clinical materials (blood, cerebrospinal fluid, swabs from vagina) and the reference strain L. monocytogenes ATCC 1911. Ability to form biofilm in 96-well plates and drug susceptibility (disk diffusion method) of tested strains was determined. RESULTS: All strains formed biofilm though it’s intensity was correlated with source of isolation. The strong biofilm formed 72.73 % of isolates from cerebrospinal fluid ((A570 0.421 – 1.3), 75.0 % of blood isolates 9 (A570 0.389 – 1.063) and 50.0 % of isolates from vaginal swabs (A570 0.457 – 0.487). The strongest biofilm was formed by strains derived from cerebrospinal fluid whereas isolates from vaginal swabs, which strongly formed a biofilm accounted for 50.0% of the studied population (absorbance 0.457 - 0.487). It was found that 93.1 % (n=27) of strains were susceptible to all drugs tested. Two strains (6.9 %) were resistant to cotrimoxazol and 1 strain (3.45 %) to erythromycin. CONCLUSIONS: Diverse ability to form biofilm by clinical L. monocytogenes strains is an important aspect in prophylaxis in catheterized patients

The effect of initial sonication on disinfectant efficacy against Listeria monocytogenes biofilm

Background: Listeria monocytogenes is a Gram-positive, foodborne pathogen. Biofilms formed by thisbacterium are a serious problem in the food industry. Bacteria in biofilms are much more resistant to cleaningand disinfection agents posing a risk of food recontamination. The aim of this study was the assessmentof the influence of initial sonication on disinfectant efficacy, based on QAC, against L. monocytogenesbiofilm on the stainless steel.Methods: The biofilm formed on the stainless steel by the reference strain L. monocytogenes ATCC 19111was sonicated for 1 and 5 minutes (500W/ 20kHz/ 100% amplitude). Then disinfection with quaternaryammonium compounds (0.5% working solution) was applied for 1 and 5 minutes and the number ofbacteria recovered from the biofilm was assessed.Results: It was found that disinfection was more efficient than sonication (p ≤ 0.05). However, the combinationof sonication and disinfection significantly improved biofilm eradication compared to the use ofone of these methods separately (p ≤ 0.05). The greatest reduction of bacteria number was achieved after5 minutes of sonication combined with 5 minutes of disinfection (6.42 log CFU × cm-2), whereas the lowestreduction was observed after 1 minute-sonication (2.03 log CFU × cm-2).Conclusions: Combination of sonication and disinfection based on quaternary ammonium compounds isan effective method allowing biofilm eradication from the food production surfaces

Effect of commercially available spices and herbs on the survival of Listeria monocytogenes and Salmonella Enteritidis

Background: Currently, natural food preservation methods are explored, one of which includes the useof herbs and spices.Methods: The study assessed the effect of herbs and spices; either opened directly before the test oropened and stored for three months; on the survival of L. monocytogenes and S. Enteritidis bacilli, isolated from meat. Moreover, the microbiological purity of the investigated herbs and spices was evaluated. The research consisted of the analysis of inhibition zone patterns around the wells with spice pulp after the incubation period.Results: Varied influence of herbs and spices on the survival of bacilli was reported, depending on thespecies. The strongest impact against L. monocytogenes, among freshly opened spices, had: granulatedgarlic (38.63 mm), whole cloves (28.87 mm), savoury (22.25 mm), ground cinnamon (22.13 mm), ground ginger (18.75 mm). As for S. Enteritidis, in the group of freshly opened spices, the strongest effect was found for: granulated garlic (37.25 mm), whole cloves (31.50 mm), and ground cinnamon (18.16 mm). It was reported that the storage of open spices caused a decrease in antimicrobial activity against L. monocytogenes, except for cloves, oregano, hot pepper, chilli, sage and turmeric. In the case of S. Enteritidis, the following stored spices were not effective: cinnamon, ground black pepper, sage, oregano, basil, tarragon, marjoram, rosemary, coriander, green mint, hot pepper, chilli, curry.Conclusions: It was confirmed, that herbs and spices, because of its antimicrobial activity can be used,e.g. for food preservation, minimizing the amount of chemical additives applied to the product and extending its shelf-life

Viral infections after hematopoetic stem cell transplantation in children with acute lymphoblastic leukemia: the Polish experience

Introduction: Allogeneic hematopoetic stem cell transplantation (allo-HSCT) is one of the therapeutic options in pediatric acute lymphoblastic leukemia (ALL). Most previous analyses have concerned the reactivation of viruses in the entire population of children after allo-HSCT, regardless of the disease entity being an indication for transplantation. In our report, we aimed to evaluate the occurrence, etiology, risk factors and clinical outcome of viral infections in pediatric patients with ALL. Material and methods: 83 post-HSCT ALL patients from 2020 through 2021 were analyzed for infections with polioma BK virus (BKV), cytomegalovirus (CMV), Epstein-Bárr virus, severe acute respiratory syndrome coronavirus 2, adenovirus, respiratory syncytial virus, norovirus, rotavirus, influenza, human herpes virus-6, parainfluenza and rhinovirus. Results: Viral infections were detected after 41% of the transplantations. The viruses most commonly detected were BKV (26.2%) and CMV (23.8%). The analyzed potential risk factors for viral infections were total body irradiation (TBI), graft-versus-host disease, complete remission status, and donor type. Overall survival in the investigated group was 0.815. Conclusions: Complications occurred more frequently in patients without TBI and we did not confirm the impact of other factors. Viral infections in children with ALL after allo-HSCT remain a significant problem. Our results highlight the importance of frequent monitoring and anti-viral prophylaxis