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We studied 127 samples of bivalve mollusks (Mediterranean mussel, Mytilus galloprovincialis; smooth clam, Callista chione; grooved carpet‐shell clam, Tapes decussatus; and striped venus clam, Chamelea gallina) obtained in the winter and spring of 2009 from retail fish and shellfish vendors in Granada, Spain. Samples were analyzed (raw and after steaming) to determine the prevalence of Escherichia coli, mesophilic aerobes, Staphylococcus aureus and the disease‐causing microorganisms Salmonella spp., Listeria monocytogenes and Vibrio parahaemolyticus. E. coli was found in 25% of raw samples and 4% of cooked samples. Aerobes were found in 89% of raw samples (more than 1,000 cfu/g), and S. aureus was found in 37.0%. Only one raw sample was positive for V. parahaemolyticus. The percentage of positive findings was fourfold as high in the spring sample as in the winter sample. Contamination was most frequent in the smooth clam, and samples obtained on Mondays were more frequently contaminated than those obtained on other days of the week. PRACTICAL APPLICATIONS Current Spanish legislation establishes that all bivalve mollusks intended for commercial sale and human consumption must be treated at a detoxification center. The application of detoxification is of fundamental importance because it constitutes a barrier against the transmission of bacterial and viral diseases of aquatic origin. We analyzed possible differences in contamination parameters in this type of shellfish, indicated characteristics that may be affected by alterations in quality, and discussed the potential effects of these alterations on human health.

The aim of this research was to study the phenotypic resistances to disinfectants and antibiotics in strains of methicillin-resistant Staphylococcus aureus (MRSA) obtained from Canary black pigs. Analyses were performed on 54 strains of MRSA, isolated in Canary black pigs from the province of Tenerife (Spain); all of them carried the mecA gene. The strains were isolated by means of nasal swab samples of healthy pigs, collected under veterinarian supervision. Bactericidal activity of antiseptics and disinfectants was tested by means of the dilution-neutralization method. Susceptibility to the disinfectants glutaraldehyde, peracetic acid and silver nitrate was assessed, as well as to the antiseptics chlorhexidine, benzalkonium chloride and povidone iodine. Susceptibility to a wide array of antibiotics representing the main groups was determined by means of the disc diffusion method. All the strains demonstrated susceptibility to the disinfectants tested at the recommended concentration, and even to dilutions equal to or lesser than 1/16. The most effective antiseptic and disinfectant were, respectively, chlorhexidine and silver nitrate. With regard to the antibiotics, the strains proved to be multiresistant. All presented phenotypic resistance to the β-lactam antibiotics ampicillin, penicillin and cefoxitin, as well as to numerous aminoglycosides, tetracycline and trimethoprim-sulfamethoxazole. It was also observed that 61.1% of the strains were carriers of plasmids. Our results underline that in the strains such as MRSA, which show multiple resistances to antibiotics, the antiseptics and disinfectants show great efficacy. Moreover, as other authors also suggest, for the treatment and prevention of infections caused by MRSA, the use of β-lactam and aminoglycoside antibiotics may be less effective.

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