Salvo Rindi

Occurrence of Vancomycin-Resistant Enterococci in Foods of Animal Origin Purchased in Tuscany

Enterococci are ubiquitous microorganisms, commonly found in plants, insects and wild animals, and are normal residents of the gastrointestinal tract of both animals and humans. They frequently occur in large numbers in certain foods, especially those of animal origin. Over the last 10 years, enterococci have emerged as major nosocomial pathogens, thus representing an increasingly important problem for public health, in relation to their ability to acquire resistance to some antimicrobial agents of relevance to human therapy, such as glycopeptides, particularly vancomycin. In this regard, the food chain represents a possible source of vancomycin-resistant enterococci for humans, mainly as a result of the use of avoparcin, a vancomycin-like glycopeptide, as a feed additive for growth promotion of farm animals, as undoubtedly established by previous studies (Bates, 1997; Mc Donald et al., 1997). Although the utilization of avoparcin in animal husbandry has been banned since 1997, VRE have recently been isolated from foods of different typology (Giraffa et al., 2000; Knijff et al., 2002), therefore investigation into the frequency of recovery of VRE at this level is still recommendable. Thus, the present survey was carried out with the aim of evaluating the occurrence of VRE in foods of animal origin purchased in Tuscany, considering that these microorganisms could play a relevant role both directly as potential pathogens for humans, as well as in relation to their capability to spread antibiotic resistance genes to other pathogenic bacteria, such as Staphylococcus aureus.

Occurrence and antimicrobial susceptibility of aeromonads from maricultured gilthead seabream (Sparus aurata)

In Europe the demand for gilthead seabream (Sparus aurata) has increased significantly over the past decade as well as its aquaculture production. In aquaculture, antibiotics are commonly used for prevention or cure of diseases. A mayor potential consequence of this use is the development of drug-resistant bacteria. Furthermore, inappropriate use is likely to cause an unnecessary impact on the environment. In this work we studied the antimicrobial susceptibility pattern of Aeromonas strains, considering that aeromonads are found in a diversity of habitats and are responsible for human and fish infections. A total of 80 fish was examined in 2009 in March and September. The fish came from 2 types of mariculture farms in Italy: a traditional, in Ligury (in-shore cages) and an atypical, in Tuscany (initial phase of fish life in cages and then free life in lacoon). Aeromonads were counted from skin, gills, flesh and gut of the fish on Aeromonas Agar (Ryan), GSP Agar and Starch DNA Agar. Means and standard deviations were determined for aeromonads counts and means were compared by T-test. Seventy Aeromonas isolates, preidentified at genus level and confirmed with a genus-specific PCR, were phenotypically identified at group level using API20 E and 20 NE kits, completed by testing gas production from glucose. The strains, belonging to A. caviae, A. hydrophila, A. sobria groups, were studied for their antimicrobial susceptibility pattern considering 20 antimicrobials by the disk diffusion technique, according to the CLSI recommendations and a χ2 test was performed. The highest mean counts were reached in gills in September in both plants with values over 5 log cfu/g, whereas flesh samples never gained 3 log cfu/g. All strains exhibited resistance against at least 4 antimicrobials. Three strains from the Ligurian farm showed resistance to 10-13 antimicrobials.