A survey of soft cheeses in Greek retail outlets highlights a low prevalence of Listeria spp.

Abstract

International audienc

Identification of non-Listeria spp. bacterial isolates yielding a β-d-glucosidase-positive phenotype on Agar Listeria according to Ottaviani and Agosti (ALOA)

“…in the Laboratory of Milk Hygiene and Technology, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki (Angelidis et al, 2012). In that study, during the concurrent application of the ISO 11290-1 and 11290-2 methods, certain cheese samples yielded bluish-green colonies on ALOA i.e., presumptive Listeria spp.…”

“…These 64 presumptive Listeria spp. isolates originated from three different steps of the analytical protocols, depending on the medium (the stage of the ISO protocol) that had been used to inoculate the ALOA plates (Angelidis et al, 2012). Hence, isolates were obtained from ALOA that had been inoculated from: i) unsupplemented HalfFraser Broth (HFB) during enumeration testing and prior to adding the selective agents (ferric ammonium citrate, nalidixic acid and acriflavine HCl) to HFB (hereafter referred to as "uB isolates"), ii) HFB incubated for 24 h at 30°C during detection testing ("HFB isolates") and iii) Fraser Broth (FB) incubated for 48 h at 37°C during detection testing ("FB isolates").…”

“…In order to exclude potential batch-related or manufacturer-related effects, all isolates were additionally checked for colony phenotypic characteristics: a) on ALOA base medium and supplements of the same manufacturer (Biolife), but of different lot numbers from those used during the original isolation experiments (Angelidis et al, 2012), hereafter referred to as "ALOA B" and also b) on Chromocult® Listeria Selective Agar (Merck), a medium corresponding to Agar Listeria acc. to Ottaviani and Agosti in line with the recommendations of ISO 11290, hereafter referred to as "ALOA-M".…”

Prevalence and survival of Listeria monocytogenes in various types of cheese—A review

“…Although L. monocytogenes may not be present in a cheese sample, other Listeria species can sometimes be isolated, such as Listeria innoccua (Angelidis et al . ). The presence of other species of the genus suggests that the conditions could also be suitable for the growth of L. monocytogenes and therefore specific measures should be implemented (Pintado et al .…”

Analysis of the baseline survey on the prevalence ofListeria monocytogenesin certain ready-to-eat foods in the EU, 2010-2011 Part A:Listeria monocytogenesprevalence estimates

“…The survey was designed according to the Report of the Task Force on Zoonoses Data Collection on the proposed technical specifications for a survey on L. monocytogenes (EFSA, 2009a), with the exception that cheeses were examined at the time of sampling and also fresh cheeses were included in the analysis. None of the samples tested positive for L. monocytogenes (either qualitatively or quantitatively) (0 %; 95 % CI = 0-2.2 %) (Angelidis et al, 2012). However, a very low prevalence of L. monocytogenes in semi-soft cheese at retail was also noted in a national survey in Sweden in 2010 in which L. monocytogenes was detected in 0.4 % of 525 cheese samples (Lambertz et al, 2012).…”