Prevalence and level of Listeria monocytogenes and other Listeria sp. in ready-to-eat minimally processed and refrigerated vegetables.

Minimally processed and refrigerated vegetables can be contaminated with Listeria species bacteria including Listeria monocytogenes due to extensive handling during processing or by cross contamination from the processing environment. The objective of this study was to examine the microbiological quality of ready-to-eat minimally processed and refrigerated vegetables from supermarkets in Osijek, Croatia. 100 samples of ready-to-eat vegetables collected from different supermarkets in Osijek, Croatia, were analyzed for presence of Listeria species and Listeria monocytogenes. The collected samples were cut iceberg lettuces (24 samples), other leafy vegetables (11 samples), delicatessen salads (23 samples), cabbage salads (19 samples), salads from mixed (17 samples) and root vegetables (6 samples). Listeria species was found in 20 samples (20 %) and Listeria monocytogenes was detected in only 1 sample (1 %) of cut red cabbage (less than 100 CFU/g). According to Croatian and EU microbiological criteria these results are satisfactory. However, the presence of Listeria species and Listeria monocytogenes indicates poor hygiene quality. The study showed that these products are often improperly labeled, since 24 % of analyzed samples lacked information about shelf life, and 60 % of samples lacked information about storage conditions. With regard to these facts, cold chain abruption with extended use after expiration date is a probable scenario. Therefore, the microbiological risk for consumers of ready-to-eat minimally processed and refrigerated vegetables is not completely eliminated.

Biological properties of a naturally attenuated infectious bursal disease virus isolated from a backyard chicken flock.

The biological properties of an infectious bursal disease (IBD) virus isolated from bursas collected during an outbreak in a village chicken flock in Macedonia are described. The mortality rate was 50%. Two viruses coexisted in the bursas of infected chickens (IBDVwt and IBDVtc). The virus termed IBDVtc grows on chicken embryo fibroblast (CEF) cells from the first passage. Specific pathogen free chickens inoculated with IBDVtc at passage level 4 did not develop any clinical signs of disease. Some discrete bleeding on the leg muscles was seen and the bursa of Fabricius revealed pathological lesions similar to those caused by classical strains. However, the bursa recovered quickly (bursa lesion score 2) by 14 days post infection (PI). We also found evidence of bursal repopulation by means of perinuclear antigen staining. Strong CD3 influx was evident at 4 days PI, and at 33 days PI the CD3+ cell finding was comparable to the control. The mean antibody titre was 9.2 log 2 at 14 days PI. The amino acid composition of VP2 in IBDVwt (222 Ala, 242 Ile, 253 Gln, 256 Ile, 279 Asp, 284 Ala, 294 Ile and 299 Ser) is described. The same sequence was found in IBDVtc, except for two point mutations, at Gln253→His and Ala284→Thr. Such amino acid substitution is responsible for partial attenuation and the ability of the strain to replicate in cell culture. None of the commercial vaccine viruses has a similar arrangement of amino acids in the variable domain of IBDV. This strongly suggests that IBDVtc originates from a very virulent strain. To the best of our knowledge, this is the first report of a concomitant infection of chickens with highly pathogenic IBDV and its mutant counterpart.