Comparison of Intranasal and Injectable Glucagon Administration Among Pediatric Population Responders

Aims: Ease of use and acceptability of nasal versus injectable glucagon (IG) among pediatric responders have been little investigated. This study compared the performance of administering nasal and IG in parents of youth with type 1 diabetes (T1D) and in school workers. Enablers and barriers associated with each glucagon and preferred glucagon administration learning modality were also evaluated. Methods: Three months after watching short pedagogical videos, 30 parents and 30 school workers performed simulated scenarios where they administered both glucagon. Completion time and successful execution of critical steps were collected. Interviews assessed preferred learning modalities, barriers, and enablers associated with each glucagon. Results: Both groups administered nasal glucagon faster than IG (median [interquartile range]: parents 19 [12-29] vs. 97 [71-117] s, P < 0.001; school workers 24 [16-33] vs. 129 [105-165] s, P < 0.001). A lower proportion of participants successfully executed all critical steps for injectable versus nasal glucagon (significant difference for school workers [53% vs. 90%; P = 0.007] but not for parents [68% vs. 83%; P = 0.227]). Nasal glucagon was preferred for ease of use and acceptability. Preferred learning modalities were a combination of videos and workshops, but videos alone could suffice for nasal glucagon. Conclusions: Nasal glucagon is faster to use, more likely to be successfully administered, and more acceptable than IG for parents of children with T1D and school workers. Nasal glucagon training with videos could improve school workers' involvement in severe hypoglycemia management. Clinical Trial number, URL to the registration: NCT05395000, https://clinicaltrials.gov/ct2/show/NCT05395000.

Probiotic interventions promote metabolic health in high fat-fed hamsters in association with gut microbiota and endocannabinoidome alterations

Probiotics represent a promising tool to improve metabolic health, including lipid profiles and cholesterol levels. Modulation of the gut microbiome and the endocannabinoidome - two interrelated systems involved in several metabolic processes influenced by probiotics - has been proposed as a potential mechanism of action. This study establishes the impact of probiotics on metabolic health, gut microbiota composition and endocannabinoidome mediators in an animal model of hypercholesterolaemia. Syrian hamsters were fed either a low-fat low-cholesterol or high-fat high-cholesterol (HFHC) diet to induce hypercholesterolaemia and gavaged for 6 weeks with either Lactobacillus acidophilus CL1285, Lactiplantibacillus plantarum CHOL-200 or a combination of the two. Globally, probiotic interventions ameliorated, at least partially, lipid metabolism in HFHC-fed hamsters. The interventions, especially those including L. acidophilus, modified the gut microbiota composition of the small intestine and caecum in ways suggesting reversal of HFHC-induced dysbiosis. Several associations were observed between changes in gut microbiota composition and endocannabinoidome mediators following probiotic interventions and both systems were also associated with improved metabolic health parameters. For instance, potential connexions between the Eubacteriaceae and Deferribacteraceae families, levels of 2‑palmitoylglycerol, 2‑oleoylglycerol, 2‑linoleoylglycerol or 2‑eicosapentaenoylglycerol and improved lipid profiles were found. Altogether, our results suggest a potential crosstalk between gut microbiota and the endocannabinoidome in driving metabolic benefits associated with probiotics, especially those including L. acidophilus, in an animal model of hypercholesterolaemia.

Adrenal insufficiency among children treated with hormonal therapy for infantile spasms

OBJECTIVE

Hormonal therapy is a standard treatment for children with infantile spasms. However, the high doses given and long treatment duration expose patients to the risk of adrenal insufficiency (AI). This study aims to quantify the cumulative incidence of AI among children with infantile spasms treated with high-dose corticosteroids and/or adrenocorticotropic hormone.

METHODS

A retrospective chart review of patients treated for infantile spasms was performed between January 2009 and March 2020 in one pediatric specialized hospital. Variables collected include patient and treatment characteristics, risk factors of AI, and adrenal function testing. Analysis included descriptive statistics such as incidence and bivariate analysis.

RESULTS

Thirty-one patients were included and received a total of 33 courses of treatment (17 corticosteroids [prednisone/prednisolone], 12 adrenocorticotropic hormone, and four combined). Physiologic hydrocortisone replacement therapy with stress supplementation was received after 32 of 33 (97%) courses of treatment. Adrenal function was assessed in 32 of 33 (97%) and AI occurred in 25 of 33 (76%, 95% confidence interval = 58-89). No predictive factor of AI was identified after hormonal treatment. No drug regimen was found to be safe. The two patients who developed an acute adrenal crisis presented to the emergency room within the days (between 2 and 7) following weaning off of hormonal treatment. They were the youngest children of the cohort, and both received prednisolone.

SIGNIFICANCE

Adrenal insufficiency is frequent and can potentially lead to an adrenal crisis in this population. This study highlights the necessity of hydrocortisone replacement therapy until AI has been excluded in a patient who has received hormonal therapy to treat infantile spasms. As such, routine laboratory assessment of adrenal function should be done in all patients.

71 Adrenal Insufficiency among Children treated with Hormonal Therapy for Infantile Spasms

Primary Subject area

Endocrinology and Metabolism

Background

Hormonal therapy is a standard treatment for children with infantile spasms. However, the high doses given and long treatment duration exposes patients to the potential risk of adrenal insufficiency (AI). There is, presently, limited data on occurrence of AI after hormonal therapy in this population.

Objectives

This study aims to quantify the incidence of AI among children with infantile spasms treated with high-dose corticosteroids and/or adrenocorticotropic hormone (ACTH).

Design/Methods

A retrospective chart review of patients less than 2 years old treated for infantile spasms was performed between January 2009 to March 2020 in one pediatric specialized hospital. Variables collected included sex, age, etiology, age at treatment initiation, type of hormonal treatment, dose and duration of treatment, concomitant medication and illness, other corticosteroid uses, hydrocortisone replacement therapy use, adrenal function testing, and signs of AI. Analysis included descriptive statistics, such as incidence and bivariate analysis.

Results

Thirty-one patients met the inclusion criteria and received a total of 33 separated courses of hormonal treatment. Adrenal function following each course of treatment was evaluated in all patients, either by tests or by the presence of adrenal crisis. Oral hydrocortisone replacement therapy was received by 32/33 (97%) children. AI occurred in 25/33 (76% [95% CI 58-89]) children. There was no predictive factor for adrenal insufficiency after hormonal treatment, and no drug regimen (duration or total received dose) was safe. Two patients (6%) presented to the emergency room with an acute adrenal crisis the day following the weaning off of hormonal treatment. They were the youngest children of the cohort, with an age of 1,6 and 2,7 months at the initiation of treatment. All other patients were aged 4 months and older.

Conclusion

This study suggests that adrenal suppression is frequent after standard hormonal therapy regimen for infantile spasms. This can lead to serious complications, such as adrenal crisis, if not supplemented. A routine laboratory assessment of adrenal function should be done after hormonal therapy for all patients. We suggest that hydrocortisone replacement therapy should be given at the end of hormonal therapy and until testing results for adrenal function are obtained, particularly for younger patients.

Risk of adrenal insufficiency following intra-articular or periarticular corticosteroid injections among children with chronic arthritis

Objectives Intra-articular and/or periarticular corticosteroid injection (IACI) is a common procedure in pediatric rheumatology. Despite many adult studies demonstrating a significant risk of adrenal insufficiency (AI) following the procedure, very little evidence is available in the pediatric literature regarding this risk. The main goal of this study is to evaluate the prevalence of AI in children with chronic arthritis following IACI. Methods This is a retrospective study including children aged 0-18 years who had an IACI from June 2017 to July 2019. An 8:00 morning cortisol (8MC) sample was drawn around two weeks after the injection, and an ACTH 1mcg stimulation test was performed if morning cortisol level was low. AI was defined as an 8MC under 50 nmol/L or an abnormal ACTH stimulation test. Risks factors for AI and its duration were assessed. Results Sixty patients were included in this study. AI prevalence was 30% with 18 of 60 affected patients. The corticosteroid dose injected was statistically associated with the development of AI. Median duration of AI was 181 days for the nine patients who were followed up until resolution of AI. Four patients developed symptoms of AI, namely fatigue (2 of 4), nausea (2 of 4) and abdominal pain (3 of 4). None were hospitalized or died. Conclusions In this cohort of children with chronic arthritis who had an IACI, we found a high prevalence of AI. Monitoring and counseling of such complication is warranted until further evidence is available.

Primary prevention of Clostridium difficile infections with a specific probiotic combining Lactobacillus acidophilus, L. casei, and L. rhamnosus strains: assessing the evidence

Clostridium difficile infection (CDI) has become the leading healthcare-associated infection and cause of outbreaks around the world. Although various innovative treatments have been developed, preventive strategies using multi-faceted infection control programmes have not been successful in reducing CDI rates. The major risk factor for CDI is the disruption of the normally protective gastrointestinal microbiota, typically by antibiotic use. Supplementation with specific probiotics has been effective in preventing various negative outcomes, including antibiotic-associated diarrhoea and CDI. However, a consensus of which probiotic strains might prevent CDI has not been reached and meta-analyses report high degrees of heterogeneity when studies of different probiotic products are pooled together. We searched the literature for probiotics with sufficient evidence to assess clinical efficacy for the prevention of CDI and focused on one specific probiotic formulation comprised of three lactobacilli strains (Lactobacillus acidophilus CL1285, Lactobacillus casei LBC80R, Lactobacillus rhamnosus CLR2, Bio-K+) for its ability to prevent CDI in healthcare settings. A literature search on this probiotic formulation was conducted using electronic databases (PubMed, Google Scholar), abstracts from infectious disease and infection control meetings, and communications from the probiotic company. Supporting evidence was found for its mechanisms of action against CDI and that it has an excellent safety and tolerability profile. Evidence from randomized controlled trials and facility-level interventions that administer Bio-K+ show reduced incidence rates of CDI. This probiotic formulation may have a role in primary prevention of healthcare-associated CDI when administered to patients who receive antibiotics.

Probiotics and prevention of Clostridium difficile infection

The role of probiotics as adjunctive measures in the prevention of Clostridium difficile infection (CDI) has been controversial. However, a growing body of evidence has suggested that they have a role in primary prevention of CDI. Elements of this controversy are reviewed and the proposed mechanisms of action, the value and cost effectiveness of probiotics are addressed with a focus on three agents, Saccharomyces boulardii, Lactobacillus rhamnosus GG and the combination of Lactobacillus acidophilus CL1285, Lactobacillus casei LBC80R, Lactobacillus rhamnosus CLR2 (Bio-K+).

Somatic GPR101 Duplication Causing X-Linked Acrogigantism (XLAG)-Diagnosis and Management

CONTEXT

Recent reports have proposed that sporadic or familial germline Xq26.3 microduplications involving the GPR101 gene are associated with early-onset X-linked acrogigantism (XLAG) with a female preponderance.

CASE DESCRIPTION

A 4-year-old boy presented with rapid growth over the previous 2 years. He complained of sporadic headaches and had coarse facial features. His height Z-score was +4.89, and weight Z-score was +5.57. Laboratory testing revealed elevated serum prolactin (185 μg/L; normal, <18 μg/L), IGF-1 (745 μg/L; normal, 64-369 μg/L), and fasting GH > 35.0 μg/L. Magnetic resonance imaging demonstrated a homogenous bulky pituitary gland (18 × 15 × 13 mm) without obvious adenoma. A pituitary biopsy showed hyperplastic pituitary tissue with enlarged cords of GH and prolactin cells. Germline PRKAR1A, MEN1, AIP, DICER1, CDKN1B, and somatic GNAS mutations were negative. Medical management was challenging until institution of continuous sc infusion of short-acting octreotide combined with sc pegvisomant and oral cabergoline. The patient remains well controlled with minimal side effects 7 years after presentation. His phenotype suggested XLAG, but his peripheral leukocyte-, saliva-, and buccal cell-derived DNA tested negative for microduplication in Xq26.3 or GPR101. However, DNA isolated from the pituitary tissue and forearm skin showed duplicated dosage of GPR101, suggesting that he is mosaic for this genetic abnormality.

CONCLUSIONS

Our patient is the first to be described with somatic microduplication leading to typical XLAG phenotype. This patient demonstrates that a negative test for Xq26.3 microduplication or GPR101 duplication on peripheral blood DNA does not exclude the diagnosis of XLAG because it can result from a mosaic mutation affecting the pituitary.

Programme to provide Quebec infants with free vitamin D supplements failed to encourage participation or adherence

AIM

The aim of this study was to evaluate the uptake of a free vitamin D infant prescription programme and to determine the incidence of nutritional rickets.

METHODS

This was a retrospective cohort study of infants from Quebec, Canada, involving term infants born between 1998 and 2008 and covered by the public insurance programme. Data were extracted from the Quebec Pregnancy Cohort. Predictors of programme participation were identified through logistic regression.

RESULTS

A total of 123 018 infants were eligible, and the mean annual prevalence of supplemental vitamin D exposure was 17.9 ± 5.6%. The median age for obtaining the first bottle was 36 days and half only obtained one bottle of 50 doses. Mothers with higher socio-economic status, those who lived as a couple, older mothers or a prescription by a paediatrician significantly increased the odds of obtaining vitamin D. There was a decline in programme participation over time (OR 0.89/year, 95% CI = 0.88-0.90). The incidence of rickets was 23.9 cases per 100 000 live births, with an annual increase of 1.12 cases/year (95% CI = 1.01-1.24).

CONCLUSION

Without educational measures, a free prescription programme for vitamin D failed to encourage participation or adherence. Moreover, participation decreased with time. New strategies, including educational support, need to be developed to increase vitamin D supplementation rates.

Glucose-responsive insulin and glucagon delivery (dual-hormone artificial pancreas) in adults with type 1 diabetes: a randomized crossover controlled trial

BACKGROUND

Most patients with type 1 diabetes do not achieve their glycemic targets. We aimed to assess the efficacy of glucose-responsive insulin and glucagon closed-loop delivery for controlling glucose levels in adults with type 1 diabetes.

METHODS

We conducted a randomized crossover trial involving 15 adults with type 1 diabetes, comparing standard insulin-pump therapy with dual-hormone, closed-loop delivery. Patients were admitted twice to a clinical research facility and received, in random order, both treatments. Each 15-hour visit (from 1600 to 0700) included an evening exercise session, followed by a medium-sized meal, a bedtime snack and an overnight stay. During visits that involved closed-loop delivery, basal insulin and glucagon miniboluses were delivered according to recommendations based on glucose sensor readings and a predictive dosing algorithm at 10-minute intervals. During visits involving standard insulin-pump therapy (control visits), patients used conventional treatment.

RESULTS

Dual-hormone closed-loop delivery increased the percentage of time for which patients' plasma glucose levels were in the target range (median 70.7% [interquartile range (IQR) 46.1%-88.4%] for closed-loop delivery v. 57.3% [IQR 25.2%-71.8%] for control, p = 0.003) and decreased the percentage of time for which plasma glucose levels were in the low range (bottom of target range [< 4.0 mmol/L], 0.0% [IQR 0.0%-3.0%] for closed-loop delivery v. 10.2% [IQR 0.0%-13.0%] for control, p = 0.01; hypoglycemia threshold [< 3.3 mmol/L], 0.0% [IQR 0.0%-0.0%] for closed-loop delivery v. 2.8% [IQR 0.0%-5.9%] for control, p = 0.006). Eight participants (53%) had at least 1 hypoglycemic event (plasma glucose < 3.0 mmol/L) during standard treatment, compared with just 1 participant (7%) during closed-loop treatment (p = 0.02).

INTERPRETATION

Dual-hormone, closed-loop delivery guided by advanced algorithms improved short-term glucose control and reduced the risk of hypoglycemia in a group of 15 adults with type 1 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT01297946.

Effect of selected antimicrobial compounds on the radiosensitization of Salmonella Typhi in ground beef

AIMS

In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces.

METHODS AND RESULTS

Ground beef samples inoculated with Salmonella Typhi (10(6) CFU g(-1)) were treated with each antimicrobial compound at a concentration of 0.5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a (60)Co irradiator at doses from 0 to 1.75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D(10) value in the absence/presence of antimicrobial compound.

CONCLUSIONS

Depending on the compound tested, the addition of antimicrobial compound decreased the D(10) value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans-cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef.

SIGNIFICANCE AND IMPACT OF THE STUDY

These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi.

Effect of selected plant essential oils or their constituents and modified atmosphere packaging on the radiosensitivity of Escherichia coli O157:H7 and Salmonella typhi in ground beef

Twenty-six different essential oils were tested for their efficiency to increase the relative radiosensitivity of Escherichia coli and Salmonella Typhi in medium-fat ground beef (23% fat). Ground beef was inoculated with E. coli O157:H7 or Salmonella (10(6) CFU/g), and each essential oil or one of their main constituents was added separately at a concentration of 0.5% (wt/wt). Meat samples (10 g) were packed under air or under modified atmosphere and irradiated at doses from 0 to 1 kGy for the determination of the D10-value of E. coli O157:H7, and from 0 to 1.75 kGy for the determination of the D10-value of Salmonella Typhi. Depending on the compound tested, the relative radiation sensitivity increased from 1 to 3.57 for E. coli O157:H7 and from 1 to 3.26 for Salmonella Typhi. Addition of essential oils or their constituents before irradiation also reduced the irradiation dose needed to eliminate both pathogens. In the presence of Chinese cinnamon or Spanish oregano essential oils, the minimum doses required to eliminate the bacteria were reduced from 1.2 to 0.35 and from 1.4 to 0.5 for E. coli O157:H7 and Salmonella Typhi, respectively. Cinnamon, oregano, and mustard essential oils were the most effective radiosensitizers.

Purification and identification of the pediocin produced by Pediococcus acidilactici MM33, a new human intestinal strain

AIMS

The aim of this study was to purify and identify the bacteriocin produced by Pediococcus acidilactici MM33, a strain previously isolated from human gut.

METHODS AND RESULTS

Purification of the bacteriocin was performed by cationic exchange chromatography followed by a reverse phase step. Biochemical and mass spectrometry analysis showed homology with pediocin PA-1. To verify if P. acidilactici MM33 carried the pediocin PA-1 gene, total DNA was used to amplify the pediocin gene. The PCR product obtained was then sequenced and the nucleotide sequence revealed to be identical to that of pediocin PA-1. Treatment of P. acidilactici MM33 with novobiocin resulted in a plasmid-cured strain without bacteriocin-producing capacity. Antimicrobial assay and molecular analysis demonstrated that this strain was ped(-) suggesting that the ped cluster is plasmid encoded. Antimicrobial assay revealed that pediocin was bactericidal against Listeria monocytogenes, showing a minimal inhibitory concentration (MIC) of 200 AU ml(-1).

CONCLUSIONS

A two-step purification procedure was elaborated in this study. The bacteriocin secreted by the human strain P. acidilactici MM33 is carried on a plasmid and the amino acid sequence is identical to pediocin PA-1.

SIGNIFICANCE AND IMPACT OF THE STUDY

Pediococcus acidilactici MM33 is the first human pediocin-producing strain reported and could be used as probiotic to prevent enteric pathogen colonization.

Partial characterization of bacteriocins produced by human Lactococcus lactis and Pediococccus acidilactici isolates

AIMS

The aim of this study was to isolate bacteriocin-producing lactic acid bacteria (LAB) from human intestine.

METHODS AND RESULTS

A total of 111 LAB were isolated from human adult stool and screened for their bacteriocin production. Neutralized cell-free supernatants from Lactococcus lactis subsp. lactis MM19 and Pediococcus acidilactici MM33 showed antimicrobial activity. The antimicrobials in the supernatant from a culture of L. lactis inhibited Enterococcus faecium, various species of Lactobacillus and Staphylococcus aureus; while those in the supernatant from a culture of P. acidilactici inhibited Enterococcus spp., some lactobacilli and various serotypes of Listeria monocytogenes. The antimicrobial metabolites were heat-stable and were active over a pH range of 2-10. The antimicrobial activities of the supernatants of both bacteria were inhibited by many proteases but not by catalase. The plate overlay assay allowed an approximation of size between 3.5 and 6 kDa for both antimicrobial substances.

CONCLUSIONS

As the antagonistic factor(s) produced by L. lactis MM19 and P. acidilactici MM33 were sensitive to proteolytic enzymes, it could be hypothesized that bacteriocins were involved in the inhibitory activities. Inhibition spectrum and biochemical analysis showed that these bacteria produced two distinct bacteriocins.

SIGNIFICANCE AND IMPACT OF THE STUDY

We are the first to isolate bacteriocin-producing strains of Pediococcus and Lactococcus from human intestine. These strains might be useful for control of enteric pathogens.

In vitro growth control of selected pathogens by Lactobacillus acidophilus- and Lactobacillus casei-fermented milk

AIMS

Food-borne pathogen inhibition was tested in the presence of a mixture of Lactobacillus acidophilus and Lactobacillus casei during fermentation under controlled pH conditions.

METHODS AND RESULTS

The growth of Escherichia coli O157:H7, Salmonella serotype Typhimurium, Staphylococcus aureus, Listeria innocua, Enterococcus faecium and Enterococcus faecalis was evaluated for 48 h at 37 degrees C. In the presence of the lactic acid bacteria (LAB), an increase of the generation time was observed for all the gram-positive bacteria evaluated. Staphylococcus aureus was the most sensitive strain showing an increase of the generation time by 210%. However, for all the gram-negative bacteria evaluated, no inhibition occurred after 8 h of fermentation. The soluble portion of Lact. acidophilus- and Lact. casei-fermented milk was recuperated and tested for its antimicrobial activity. Listeria innocua and Staph. aureus were the most sensitive to the presence of fermented milk supernatant showing an inhibition of 85.9% and 84.7%, respectively. This soluble fraction was neutralized to eliminate the antimicrobial effect of the organic acids produced; the most sensitive strains were L. innocua and E. coli O157:H7 showing an inhibition of 65.9% and 61.9%, respectively. Finally, the soluble fraction was neutralized and irradiated at 45 kGy using a (60)Co source to eliminate the possible antimicrobial effect of both organic acids and bacteriocin-like substances. Enterococcus faecalis, E. coli O157:H7 and Staph. aureus were the most affected bacteria by this fraction, showing 39.1, 32 and 31.2% inhibition, respectively.

CONCLUSIONS

The results obtained in this study suggest the implication of both organic acids and bacteriocin-like inhibitory substances in the antimicrobial activity observed in the soluble fraction of the probiotic preparation.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study revealed the antimicrobial mechanisms of action of Lact. acidophilus- and Lact. casei-fermented milk used to prevent antibiotic-associated diarrhoea.

Combined effects of antimicrobial coating, modified atmosphere packaging, and gamma irradiation on Listeria innocua present in ready-to-use carrots (Daucus carota)

The objective of this study was to evaluate the effect of an edible antimicrobial coating combined with modified atmosphere (MA) packaging (60% O2, 30% CO2, and 10% N2) and gamma irradiation on peeled minicarrots inoculated with Listeria innocua. Carrots were inoculated with L. innocua (10(3) CFU/g) and then coated with an antimicrobial coating based on calcium caseinate containing trans-cinnamaldehyde. The same formulation without trans-cinnamaldehyde was used as an inactive coating. Coated and uncoated carrots were packed under the MA or under air, irradiated at 0.25 or 0.5 kGy, and stored at 4 +/- 1 degrees C for 21 days. Samples were evaluated periodically for enumeration of L. innocua. Unirradiated carrots stored under air had the highest concentrations of L. innocua after 21 days of storage: 2.23 CFU/g in the uncoated samples and 2.26 CFU/ g in samples coated with the inactive coating. These results suggest that the inactive coating did not have any antimicrobial effect against L. innocua. However, the addition of the antimicrobial coating resulted in a 1.29-log reduction in the concentration of L. innocua in carrots packed under air after 21 days of storage and a 1.08-log reduction in carrots packed under MA after 7 days of storage. After 7 days of storage, no L. innocua was detected in samples treated at 0.5 kGy under air or in samples treated at 0.25 kGy under MA. A complete inhibition of L. innocua was also observed during all storage periods in uncoated and coated samples treated at 0.5 kGy under MA. These results indicate that the combination of irradiation and MA conditions play an important role in the radiosensitization of L. innocua.

Influence of antimicrobial compounds and modified atmosphere packaging on radiation sensitivity of Listeria monocytogenes present in ready-to-use carrots (Daucus carota)

Radiosensitization of Listeria monocytogenes was determined in the presence of trans-cinnamaldehyde, Spanish oregano, winter savory, and Chinese cinnamon on peeled minicarrots packed under air or under a modified atmosphere (60% O2, 30% CO2, and 10% N2). Samples were inoculated with L. monocytogenes HPB 2812 serovar 1/2a (106 CFU/g) and were coated separately with each active compound (0.5%, wt/wt) before being packaged under air or the modified atmosphere and irradiated at doses from 0.07 to 2.4 kGy. Results indicated that the bacterium was more resistant to irradiation under air in the absence of active compound. The dose required to reduce L. monocytogenes population by 1 log CFU (D10) was 0.36 kGy for samples packed under air and 0.17 kGy for those packed under the modified atmosphere. The active compounds evaluated in this study had an effect on the radiation sensitivity of L. monocytogenes on carrots. The most efficient compound was trans-cinnamaldehyde, where a mean 3.8-fold increase in relative radiation sensitivity was observed for both atmospheres compared with the control. The addition of winter savory and Chinese cinnamon produced a similar increase in relative radiation sensitivity but only when samples where packed under modified atmosphere conditions.

Antimicrobial potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 against selected bacteria

Immobilization of living cells of lactic acid bacteria could be an alternative or complementary method of immobilizing organic acids and bacteriocins and inhibit undesirable bacteria in foods. This study evaluated the inhibition potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 on selected bacteria by a modified method of the agar spot test. L. lactis was immobilized in calcium alginate (1 to 2%)-whey protein concentrate (0 and 1%) beads. The antimicrobial potential of immobilized L. lactis was evaluated in microbiological media against pathogenic bacteria (Escherichia coli, Salmonella, and Staphylococcus aureus) or Pseudomonas putida, a natural meat contaminant, and against seven gram-positive bacteria used as indicator strains. Results obtained in this study indicated that immobilized L. lactis inhibited the growth of S. aureus, Enterococcus faecalis, Enterococcus faecium, Lactobacillus curvatus, Lactobacillus sakei, Kocuria varians, and Pediococcus acidilactici. Only 4 h of incubation at 35 degrees C resulted in a clear inhibition zone around the beads that increased with time. With the addition of 10 mM of a chelating agent (EDTA) to the media, results showed growth inhibition of E. coli; however, P. putida and Salmonella Typhi were unaffected by this treatment. These results indicate that immobilized lactic acid bacteria strains can be successfully used to produce nisin and inhibit bacterial growth in semisolid synthetic media.