Food-borne infection with L. monocytogenes can cause febrile illness with gastroenteritis in immunocompetent persons.

The antimicrobial activity of 32 plant essential oils commonly used in food industry was examined against four strains of Listeria monocytogenes and one strain of Listeria innocua. Two different procedures were carried out to test the essential oils, a paper disc diffusion method and an inhibition curve. In the former procedure an absolute ethanolic solution (1:5 v/v) of each oil was tested on the plates inoculated with a bacterial concentration of 106 CFU/ml. Five of the 32 essential oils (cinnamon, clove, origanum, pimento, and thyme) showed antibacterial activity. Some of the five oils were also tested at lower concentration (1:50 v/v). The inhibition curve to study antilisteric efficacies of the five oils in a saline solution system was examined. Pimento oil showed marked and rapid activity (generally within 1 h of exposure), whereas clove, origanum, and thyme oils showed a more slow activity. The antilisteric activity of the tested oils seems to be strain dependent. A L. monocytogenes strain was also tested in a food matrix (minced pork meat) against thyme essential oil. Minced pork meat with thyme oil reduced the L. monocytogenes population by ca. 100-fold over the first week of storage.

a b s t r a c tThe intestinal microbiota is an ecosystem formed by a variety of ecological niches, made of several bacterial species and a very large amount of strains. The microbiota is in close contact with the intestinal mucosa or epithelial interface which is, after the respiratory area, the largest surface of the body, occupying approximately 250-400 m 2 . The physiological activities of the microbiota are manifold and are just being unraveled. Based on the observations of the multiple roles played by the microbiota in health and disease, the notion of modifying it with appropriate formulations, i.e. probiotics, is being tested in several settings.This review summarizes the current knowledge on probiotics and discusses both limitations and acquired evidence to support their use in preventive and therapeutic medicine.

The first two confirmed cases of type E infant botulism occurred in two 16-week-old girls in Rome, Italy. The original diagnosis for the first patient was intestinal blockage due to an ileocecal invagination, which was treated surgically. Postoperatively, the patient became unresponsive and required ventilatory assistance. A diagnosis of infant botulism was then made. The second infant presented to the same hospital 7 1/2 months later with profound weakness, hypotonicity, mydriasis, and areflexia. This case was recognized as possible botulism at admission. Both cases were confirmed by detection and identification of type E botulinal toxin in stool specimens and in enrichment cultures of those specimens. The toxigenic organisms isolated were quite different from Clostridium botulinum type E. The apparent causative organism in each case resembles Clostridium butyricum but produces a neurotoxin that is indistinguishable from type E botulinal toxin by its effects on mice and by its neutralization with type E botulinal antitoxin.

Two unconnected cases of type E botulism involving a 19-year-old woman and a 9-year-old child are described. The hospital courses of their illness were similar and included initial acute abdominal pain accompanied by progressive neurological impairment. Both patients were suspected of having appendicitis and underwent laparotomy, during which voluminous Meckel's diverticula were resected. Unusual neurotoxigenic Clostridium butyricum strains that produced botulinum-like toxin type E were isolated from the feces of the patients. These isolates were genotypically and phenotypically identical to other neurotoxigenic C. butyricum strains discovered in Italy in 1985-1986. No cytotoxic activity of the strains that might explain the associated gastrointestinal symptoms was demonstrated. The clinical picture of the illness and the persistence of neurotoxigenic clostridia in the feces of these patients suggested a colonization of the large intestine, with in vivo toxin production. The possibility that Meckel's diverticulum may predispose to intestinal toxemia botulism may warrant further investigation.

BackgroundPlasmids that encode certain subtypes of the botulinum neurotoxin type B have recently been detected in some Clostridium botulinum strains. The objective of the present study was to investigate the frequency with which plasmid carriage of the botulinum neurotoxin type B gene (bont/B) occurs in strains of C. botulinum type B, Ab, and A(B), and whether plasmid carriage is bont/B subtype-related.Methodology/Principal FindingsPCR-Restriction fragment length polymorphism was employed to identify subtypes of the bont/B gene. Pulsed-field gel electrophoresis and Southern blot hybridization with specific probes were performed to analyze the genomic location of the bont/B subtype genes. All five known bont/B subtype genes were detected among the strains; the most frequently detected subtype genes were bont/B1 and /B2. Surprisingly, the bont/B subtype gene was shown to be plasmid-borne in >50% of the total strains. The same bont/B subtype gene was associated with the chromosome in some strains, whereas it was associated with a plasmid in others. All five known bont/B subtype genes were in some cases found to reside on plasmids, though with varying frequency (e.g., most of the bont/B1 subtype genes were located on plasmids, whereas all but one of the bont/B2 subtypes were chromosomally-located). Three bivalent isolates carried both bont/A and /B genes on the same plasmid. The plasmids carrying the bont gene were five different sizes, ranging from ∼55 kb to ∼245 kb.Conclusions/SignificanceThe unexpected finding of the widespread distribution of plasmids harboring the bont/B gene among C. botulinum serotype B strains provides a chance to examine their contribution to the dissemination of the bont genes among heterogeneous clostridia, with potential implications on issues related to pathogenesis and food safety.

Internalin A (InlA), a cell wall-bound protein of Listeria monocytogenes, is among the major components involved in the adhesion to and invasion of host cells expressing specific forms of E-cadherin. Some L. monocytogenes strains secrete truncated non-functional forms of InlA. The purpose of this study is to compare the biofilm-forming abilities of L. monocytogenes strains from clinical sources expressing InlA proteins in the different forms. A total of 70 L. monocytogenes strains were examined using SDS-PAGE, Western blot, DNA sequencing, and microtitre plate biofilm formation assays. We found that 8 of the 70 strains expressed truncated InlA, and that this group of strains exhibited significantly enhanced biofilm-forming ability compared to the group expressing full-length InlA. Further experiments showed that: (i) L. monocytogenes biofilms were detached by treatment with protease K; (ii) protein fragments resulting from proteolysis, rather than intact proteins, are responsible for biofilm enhancement, because biofilm formation was impaired by the protease inhibitor alpha2-macroglobulin; (iii) truncated and/or proteolytically cleaved InlA are likely involved in the biofilm enhancement, based on the effects that anti-InlA monoclonal antibodies produced on the biofilm formation of L. monocytogenes strains expressing either truncated or full-length InlA. These data provide a basis for further investigation of the molecular structure and composition of L. monocytogenes biofilms.

We describe a strategy to identify the clusters of genes encoding components of the botulinum toxin type A (boNT/A) complexes in 57 strains of Clostridium botulinum types A, Ab, and A(B) isolated in Italy and in the United States from different sources. Specifically, we combined the results of PCR for detecting the ha33 and/or p47 genes with those of boNT/A PCR-restriction fragment length polymorphism analysis. Three different type A toxin gene clusters were revealed; type A1 was predominant among the strains from the United States, whereas type A2 predominated among the Italian strains, suggesting a geographic distinction between strains. By contrast, no relationship between the toxin gene clusters and the clinical or food source of strains was evident. In two C. botulinum type A isolates from the United States, we recognized a third type A toxin gene cluster (designated type A3) which was similar to that previously described only for C. botulinum type A(B) and Ab strains. Total genomic DNA from the strains was subjected to pulsed-filed gel electrophoresis and randomly amplified polymorphic DNA analyses, and the results were consistent with the boNT/A gene clusters obtained.