Genomic insights into persistence of Listeria species in the food processing environment.

AIMS: Listeria species may colonize and persist in food processing facilities for prolonged periods of time, despite hygiene interventions in place. To understand the genetic factors contributing to persistence of Listeria strains, this study undertook a comparative analysis of seven persistent and six presumed non-persistent strains, isolated from a single food processing environment, to identify genetic markers correlating to promoting persistence of Listeria strains, through whole genome sequence analysis. METHODS AND RESULTS: A diverse pool of genetic markers relevant to hygiene tolerance was identified, including disinfectant resistance markers qacH, emrC and the efflux cassette bcrABC. Both persistent and presumed non-persistent cohorts encoded a range of stress resistance markers, including heavy metal resistance, oxidative and pH stress, although trends were associated with each cohort (e.g., qacH and cadA1C resistance was more frequently found in persistent isolates). Persistent isolates were more likely to contain mutations associated with attenuated virulence, including a truncated InlA. Plasmids and transposons were widespread between cohorts. CONCLUSIONS: Results suggest that no single genetic marker identified was universally responsible for a strain's ability to persist. Persistent strains were more likely to harbour mutation associated with hypovirulence. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides additional insights into the distribution of genetic elements relevant to persistence across Listeria species, as well as strain virulence potential.

Towards a one-step Enterobacter sakazakii enrichment.

AIMS: The current international standard method for detection of Enterobacter sakazakii from milk products is by the International Organization for Standardization and the International Dairy Federation documented method, a procedure involving two-step enrichment. This study aimed to assess enrichment of E. sakazakii using a one-step enrichment. METHODS AND RESULTS: Enrichment of four strains of E. sakazakii was compared using five different media, with stressed or unstressed cells, and at three levels of competing microflora, which were included to assess their effects on the positive isolation of E. sakazakii. Enrichment of milk powders, prepared by spray-drying milk seeded with E. sakazakii, was assessed using one-step enrichment for detection of E. sakazakii, followed by confirmation of positive isolates by real-time PCR. CONCLUSIONS: Current media are unsuitable for enrichment and detection of all E. sakazakii isolates, in particular, when high levels of background microflora are present in the sample matrix, and new defined media are needed for successful one-step enrichment. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings provide further analysis of one-step enrichment processes for E. sakazakii in the presence of competing microflora, and show that further formulation is needed for a universal E. sakazakii enrichment medium, with careful selection of both nutrients and selective agents.

Urea formaldehyde foam insulation: defusing a timebomb.

With the onset of the energy crisis in the 1970's, thousands of homeowners insulated their homes with Urea Formaldehyde Foam Insulation (UFFI). The discovery that UFFI releases formaldehyde, a carcinogen and irritant, prompted various state and federal responses to this problem. This Note reviews those responses and concludes that a ban on the sale of UFFI, coupled with a removal and repurchase program, is the most effective solution from the standpoint of consumer health.

Surveillance of verocytotoxigenic Escherichia coli in Irish bovine dairy herds.

Verocytotoxigenic Escherichia coli (VTEC) are highly significant zoonotic threats to public health, and have been the causative agent implicated in numerous high-profile outbreaks affecting large numbers of people. Serovar O157 is most frequently linked with human illness; however, other serovars, such as O26, O103, O111 and O145, have also been implicated. This study aimed to characterize the prevalence and virulence determinants of these five serovars in Irish dairy farm herds, and their milk. Using real-time PCR (RTi-PCR), bovine rectal faecal swabs and raw milk samples, along with milk filters, were screened for the presence of vt genes. Positive samples were then screened for the five serovars using sero-specific PCR. Serovar-positive samples were subjected to immunomagnetic separation, to isolate viable VTEC strains. These isolates were subsequently screened for four virulence factors: vt1, vt2, eaeA and hlyA. Three hundred and eighty six of the 600 rectal faecal swabs, 85 of the 117 milk-filters and 43 of the 120 bulk-tank milk samples, were positive for vt genes. From these 514 total vt-positive samples, 58 O26, 162 O103, 1 O111, 324 O145 and 26 O157 positives were detected by sero-specific RTi-PCR. Immunomagnetic separation yielded 12 O26, 26 O103, 0 O111, 19 O145 and 10 O157 isolates. Ten of these isolates contained at least one of the four virulence determinants screened for (i.e. vt1, vt2, eaeA and hlyA). Of these 10 isolates, pulsed-field gel electrophoresis showed that two of the O26 isolates from different farms were indistinguishable. Two O157 isolates were also indistinguishable. This study found serovars O103 and O145 to be the most prevalent in samples tested. Apart from the occurrence of VTEC in dairy herds, this study shows a high occurrence of vt genes in the environment, creating the possibility of horizontal gene transfer and emergence of new VTEC strains.