Antimicrobial susceptibility of Enterococcus spp. isolated from freshwater fish and personnel and equipment of fish markets in northern Greece

Διερευνήθηκε η ευαισθησία στα αντιμικροβιακά φάρμακα και η ικανότητα παραγωγής βιογενών αμινών από στελέχη Enterococcus spp. από ψάρια του γλυκού νερού και το προσωπικό και τον εξοπλισμό ιχθυοπωλείων στη Βόρειο Ελλάδα. Εξετάσθηκαν 270 συνολικά δείγματα και απομονώθηκαν εντερόκοκκοι από 9,6% των δειγμάτων, συγκεκριμένα από 7,4% των δειγμάτων απομονώθηκε Enterococcus faecium και από 2,2% των δειγμάτων απομονώθηκε Enterococcus casseliflavus. Τα απομονωθέντα στελέχη εξετάσθηκαν για την ευαισθησία τους έναντι 20 αντιμικροβιακών ουσιών που χρησιμοποιούνται συνήθως σε ελληνικά νοσοκομεία. Όλα τα στελέχη, εκτός ενός, ήταν πολυανθεκτικά εμφανίζοντας αντοχή σε 7-15 αντιμικροβιακά φάρμακα. Αυξημένη συχνότητα ανθεκτικότητας παρατηρήθηκε στην πενικιλλίνη, στις κεφαλοσπορίνες και στην ερυθρομυκίνη. Σχετικά αυξημένη συχνότητα παρατηρήθηκε στην κινουπριστίνη/δαλφοπριστίνη και τη λινεζολίδη, φάρμακα χρησιμοποιούμενα στη θεραπευτική αγωγή λοιμώξεων από ανθεκτικούς στη βανκομυκίνη εντεροκόκκους. Σε ένα στέλεχος E. faecium και ένα E. casseliflavus παρατηρήθηκε μέτρια ανθεκτικότητα έναντι της βανκομυκίνης. Με εξέταση με πολλαπλή αλυσιδωτή αντίδραση πολυμεράσης (multiplex PCR) των στελεχών E. faecium δεν ανιχνέυτηκαν γονίδια αντοχής στη βανκομυκίνη. Όλα τα στελέχη E. faecium και ένα τρίτο των στελεχών E. casseliflavus είχαν την ικανότητα αποκαρβοξυλίωσης της τυροσίνης, όχι όμως της ιστιδίνης, ορνιθίνης και λυσίνης. Τα αποτελέσματα υποδεικνύουν ότι τα ψάρια του γλυκού νερού και το περιβάλλον των ιχθυοπωλείων αποτελούν πιθανές πηγές διασποράς πολυανθεκτικών στελεχών εντερόκοκκων σε ανθρώπους.In total, 270 samples from freshwater fish and personnel and equipment from retail fish markets in three cities in northern Greece, were examined for presence of antimicrobial resistance and biogenic amine production of Enterococcus spp. strains. Enterococci were isolated from 9.6% of the samples; from 7.4% and 2.2%, respectively, Enterococcus faecium and Enterococcus casseliflavus were recovered. Isolates were tested for antibacterial susceptibility to 20 antibiotics used regularly in Greek hospitals. All isolates except one were multi drug resistant, to 7-15 antibiotics. Increased rates of resistance were recorded to penicillin, cephalosporins and erythromycin. Relatively increased rates were recoreded to quinupristin/casdalfopristin and linezolid, drugs commonly used as treatment options of infections by vancomycin-resistant enterococci. One E. faecium and one E. casseliflavus isolate showed intermediate resistance to vancomycin. Multiplex PCR assay for presence of van genes in E. faecium was negative. All E. faecium isolates and one third of E. casseliflavus isolates were able to decarboxylate tyrosine, but not histidine, ornithine or lysine. The results indicate that freshwater fish and fish markets are potential reservoirs of multi-drug resistant enterococci

Effect of chitosan coating on the shelf life of ready-to-eat bovine meatballs and the control of Listeria monocytogenes growth on their surface during refrigeration storage

Edible chitosan coating on the surface of ready-to-eat (RTE) bovine meatballs was evaluated for its effect on their shelf life and the control of Listeria monocytogenes at 5 °C. L. monocytogenes was inoculated onto the surface of RTE bovine meatballs with and without edible chitosan coating. The samples were stored at 5 °C. Total aerobic viable count (TVC) and the bacterial counts of L. monocytogenes, lactic acid bacteria and Enterobacteriaceae were determined on days 0,1,7,14,21 and 28. The sensory characteristics were also evaluated at the same time spots by semi trained panelists. The results of the microbiological analysis depicted that the use of edible chitosan membranes reduced all of the microbial populations that were enumerated, and retarded their growth leading to the conclusion that they can prolong the shelf life of these products by 14 days. Moreover, the population of the inoculated L. monocytogenes was about 2 log CFU/g lower in the meatballs coated with chitosan, indicating an inhibitory effect of chitosan in the growth of L. monocytogenes. The sensory analysis showed that the samples coated with chitosan were satisfactorily accepted by the panelists even at day 28, in contrast to the samples without chitosan (control samples) which were unacceptable at day 14. These results indicate that edible chitosan coatings represent a potential agent in controlling L. monocytogenes on the surface of RTE meatballs as well as other RTE meat products, prolonging their shelf life without affecting their sensory characteristics. © 2019

Fate of enterotoxigenic Staphylococcus aureus and staphylococcal enterotoxins in Feta and Galotyri cheeses

In this study the fate of enterotoxigenic Staphylococcus aureus and staphylococcal enterotoxins in Feta and Galotyri cheeses were studied. Initially, the enterotoxigenic abilities of four Staph. aureus LHA, LHB, LHC and LHD strains isolated from raw ovine milk were examined in both BHI broth and ovine milk. In BHI broth, the Staph. aureus LHA, LHB, LHC and LHD strains were found toxigenic at 37 degrees C producing the staphylococcal enterotoxins (SEs) serotypes SEA, SEB, SEC and SED, respectively, whereas in ovine milk at 37 degrees C, Staph. aureus LHD was found to produce only SED, while no SE production was observed for the other examined strains. Thus, the fate of only Staph. aureus LHD and SED were examined in Feta and Galotyri cheeses. The cheeses were made from raw ovine toxic milk with preformed SED or raw ovine milk contaminated with high (ca 6 log cfu/ml) and low inocula (ca 3 log cfu/ml) of Staph. aureus LHD. Results showed that the pathogen was eliminated at slower rate in Galotyri cheese than in Feta cheese, for the high (5 d vs. 16 d) or the low (1 d vs. 12 d) inoculum trials. In both cheeses produced from the toxic milk, SED was detected during manufacturing and storage. SED was also detected in the curd (2 h), when Staph. aureus LHD populations had reached ca 7 log cfu/g, and up to the end of storage for the high inoculum trials of both cheeses. No SED was observed for the low inoculum trials of either cheese