Characterization of coagulase-positive staphylococci isolated from tank and silo ewe milk.

The prevalence of coagulase-positive staphylococci (CPS) was studied among 390 samples of ewe milk. Fifty-seven (14.85%) samples of tank milk and all samples (6) of silo milk gave a positive result on Baird-Parker agar base supplemented with rabbit plasma fibrinogen, whereas amplification of the coagulase (coa) gene was successful in 6 (1.56%) samples of tank milk and in all silo samples. Phenotypic and genetic analysis of 153 isolates identified 151 (98.69%) as Staphylococcus aureus. Amplification of the coa gene was positive for 149 isolates (97.39%). The staphylococcal enterotoxin (SE) C gene was detected in 116 strains (75.82%), whereas more than one SE gene was carried in 5 strains (3.26%). None of the isolates harbored the genes for SEE or for methicillin resistance. A high prevalence of CPS carrying enterotoxin genes should be of concern because ewe milk is mainly processed into raw milk cheeses. The detection of the coa gene from milk samples could help to assess the microbiological safety of raw milk intended for direct use in the dairy industry.

Carnosic acid dietary supplementation at 0.12% rates slows down meat discoloration in gluteus medius of fattening lambs.

Thirty-two Merino lambs fed barley straw and a concentrate alone (CONTROL) or enriched with vitamin E (VITE006) or carnosic acid (CARN006; CARN012) were used to assess the effect of these antioxidant compounds on meat quality attributes. The animals were slaughtered after being fed for at least 5weeks with the experimental diets. The longissimus lumborum samples of VITE006, CARN006 and CARN012 groups showed higher values (P<0.001) of L* (lightness) through the complete storage period under modified atmosphere when compared to the CONTROL group. Moreover, the VITE006 and CARN012 samples revealed lower discoloration when compared to the CONTROL group, these differences being more apparent in a less color stable muscle such as gluteus medius (P<0.05 for hue after 14days of refrigerated storage). Meat sensory traits were not significantly affected by carnosic acid and microbiological analyses were not conclusive at the doses administered.

Identification and epidemiological relationships of Aeromonas isolates from patients with diarrhea, drinking water and foods.

A collection of Aeromonas isolates obtained over a three-year period in the same geographic area (León, NW of Spain) was characterized by (GTG)5-PCR fingerprinting, amplified fragment length polymorphism (AFLP) analysis and gyrB gene sequence analysis. The isolates originated from human diarrheal stools (29 isolates), potable water (13 isolates), rabbit meat (13 isolates) and marine fish (5 isolates). The distribution of Aeromonas species varied with the strain source. Aeromonas caviae HG4 and Aeromonas media HG5 were predominant in clinical and water isolates, respectively, whereas motile Aeromonas salmonicida HG3 strains were most frequently found in fish and meat. Molecular typing revealed several genotypic relationships among specific isolate subsets: (i) two clones of A. media HG5 persisted in drinking water over the study period, (ii) different patients harbored identical or closely related clones during several months, and (iii) clonal relatedness was observed in two sets of water and human isolates. The first of these sets comprised nine water isolates and two human A. media HG5 isolates, whereas the other one included a water isolate and a human isolate of A. caviae HG4. The latter finding suggests that Aeromonas transmission in the studied region followed a waterborne route. Interestingly, the three human isolates closely related to water isolates were recovered in a period of four days in June 2006 from non-related patients without underlying medical conditions that tested negative for other enteric pathogens. The data imply the transmission through contaminated water of strains of the A. caviae group that can produce disease in humans.

Identity, virulence genes, and clonal relatedness of Aeromonas isolates from patients with diarrhea and drinking water.

Among 800 stool specimens from patients with diarrhea submitted by Primary Care Centers for routine analysis to the Hospital of León (NW Spain) Microbiology and Parasitology Service, 32 (4%) were tested positive for Aeromonas spp. Mixed infections with other enteric pathogens occurred in 12 patients. A. caviae was isolated from 23 clinical specimens. There were also patients infected with A. media, A. hydrophila, A. bestiarum, and A. veronii biovar veronii. All but three isolates carried one or more of the virulence genes. The incidence of the alt, hlyA, aerA, ast, and laf genes was 71.9, 28.1, 25.0, 18.8, and 9.4%, respectively. The alt(+)/ast(+) combination was detected in four isolates and the aerA(+)/hlyA(+) combination was detected in the two A. hydrophila isolates. None of the strains harbored the TTSS, stx1, or stx2 genes and nine bore plasmids. Thirty clinical isolates and a collection of 12 A. caviae and A. media strains obtained from León municipal drinking water over the study period were typed by pulsed-field gel electrophoresis (PFGE). PFGE patterns revealed genetic relatedness and persistence over time among water isolates and some clinical isolates. Interestingly, one A. caviae (aerA(-)/hlyA(-)/alt(+)/ast(-)/laf(+)) human isolate and two A. caviae (aerA(-)/hlyA(-)/alt(+)/ast(-)/laf(+)) drinking water isolates had indistinguishable PFGE patterns, suggesting waterborne infection.

Foodborne and indicator bacteria in farmed molluscan shellfish before and after depuration.

Galicia's coast (northwestern Spain) is a major producer of bivalve molluscs. Over an 18-month period, the presence of Salmonella, Aeromonas, Plesiomonas shigelloides, Vibrio parahaemolyticus, and Clostridium botulinum was determined by PCR methods in mussels (22 batches) and infaunal bivalves (31 batches of clams and cockles) before and after depuration. All batches were harvested from Galician class B harvesting areas where bivalve molluscs must not exceed 4,600 Escherichia coli per 100 g of flesh and liquor in 90% of the samples. Virulence-associated genes of Salmonella (invA), Aeromonas (aerA, hlyA, alt, ast, and laf), P. shigelloides (hugA), V. parahaemolyticus (tdh and trh), and C. botulinum (BoNT) were not detected. The pR72H chromosomal DNA fragment, which is conservative in V. parahaemolyticus strains, was detected in five (4.7%) samples. A number of 192 suspect isolates did not fit the description of clinical Aeromonas phenospecies, pathogenic Vibrio spp., or P. shigelloides. The effectiveness of commercial depuration in reducing bacterial indicators was also examined. E. coli was reduced to < or = 230/100 g of flesh and liquor in 90.9% of mussel lots but in only 70.9% of infaunal bivalve lots. For total coliform elimination, mussels were also more effective. Total counts significantly (P < 0.005) correlated with numbers of Pseudomonas, Aeromonas, and Vibrio. Our data indicate that Salmonella and pathogenic bacteria indigenous to estuarine environments do not appear to be significant hazards in Galician molluscan shellfish. A reason for concern, however, is that clearance of E. coli to acceptable levels was not always achieved especially in infaunal bivalves.

Variation in resistance of natural isolates of Staphylococcus aureus to heat, pulsed electric field and ultrasound under pressure.

AIMS: To study and compare the resistance of 15 Staphylococcus aureus isolates to heat, pulsed electric field (PEF) and ultrasound (UW) under pressure (manosonication, MS). METHODS AND RESULTS: Survival curves to heat (58 degrees C), to PEF (22 kV cm(-1), 2 micros square wave pulses) and to UW under pressure (117 microm, 20 kHz, 200 kPa) were obtained and inactivation parameters (decimal reduction times for heat and UW under pressure, and b-values for PEF) were calculated. A wide resistance variation to heat treatment, but not to PEF and MS, was observed amongst the 15 strains. CONCLUSIONS: There was no relationship between the resistances to the three physical agents studied. Staphylococcus aureus was relatively resistant to MS but sensitive to PEF. Heat resistance varied with strain and was positively correlated to carotenoid pigment content. SIGNIFICANCE AND IMPACT OF THE STUDY: Results would help in defining safe food preservation processes. Care should be taken to choose the most adequate strain of S. aureus to model food preservation processing.