We analyzed the presence of Listeria spp. in oyster, fish, and seawater samples and tested isolates for antibiotic sensitivity. Listeria monocytogenes was found in 4.5% of fish samples and 8.3% of seawater samples and was not recovered from oysters. Multiresistant environmental strains were found, representing a potential threat to human health.Human listeriosis is a public health problem of low incidence but high mortality, requiring prompt diagnosis and adequate antibiotic therapy (1). Over the last 2 decades a high number of food-borne listeriosis outbreaks have occurred, some with high mortality rates (2,13,19). Antibiotic resistance and inefficient empirical treatment of Listeria infections could be responsible for this increased mortality (4). Since the first multiresistant Listeria monocytogenes strain was observed in France (14), different antibiotic resistance patterns in environmental, food, and clinical sources have been reported (7,12,20). Information on the presence of Listeria monocytogenes in Mexico is scarce, and the frequency of listeriosis is unknown. The purpose of this study was to determine the presence of Listeria spp. in fish, oysters, and saline waters in an area where fish are caught for local and regional consumption and to determine the sensitivities of the L. monocytogenes isolates to different antimicrobial agents.A total of 66 oyster, 66 fish, and 144 estuarine water samples were collected over a 12-month period (June 2001 to May 2002) from 12 sites of the Pueblo Viejo lagoon, Veracruz, Mexico (Fig. 1). Fish and oyster samples were transported on dry ice in separate thermal containers, and estuarine water samples were collected in sterile plastic bottles (Nalgene) and transported to the laboratory on ice. Oyster and fish samples were processed as previously described (9). Seawater samples were filtered through a 14-cm-diameter and 0.45-m-pore membrane (Millipore). Twenty-five milliliters of seawater or 25 g oyster or fish samples was added to 225 ml enrichment broth (EB; Merck) and incubated at 30°C for 24 to 48 h. The filter used for the water samples was washed with 100 ml peptone solution (0.1%), added to 225 ml EB, and incubated at 4°C for 7 days. Afterwards, a 0.1-ml sample was streaked in Oxford agar (Oxoid) and incubated at 30°C for 24 to 48 h. L. monocytogenes isolates were identified and serotyped as previously described (8). Antibiotic sensitivity was assessed using the Kirby-Bauer disk diffusion assay. The test and control strains were seeded in Mueller-Hinton agar supplemented with 0.5% defibrinated sheep blood and 0.1% esculin (17). Commercially available disks (Bio-Rad) with the following antibiotics were used: ampicillin, cephalothin, cefotaxime, ceftazidime, cefuroxime, dicloxacillin, erythromycin, gentamicin, pefloxacin, penicillin, tetracycline, and trimethoprim-sulfamethoxazole. MICs at which 50% of the isolates were inhibited (MIC 50 s) and MIC 90 s were calculated by following the CLSI (formerly NCCLS) guidelines (11). L. monocytogenes ATCC 19114, Escherichia co...

The aim of this study was to determine the effect of Tai Chi on biological markers of oxidative stress in saliva and its relationship with periodontal disease (PD) in older adults. We carried out a quasi-experimental study with a sample of 71 sedentary volunteers with PD who were divided into a control group of 34 subjects and an experimental group of 37 subjects who performed Tai Chi 5 days a week for a period of 6 months. PD status was characterized using the Periodontal Disease Index (PDI). Superoxide dismutase (SOD), total antioxidant status (TAS), and TBARS levels of both groups were measured by spectrophotometric methods. In addition, inflammation markers (TNF-α, IL-1β, IL-6, IL-8, and IL-10) were measured by flow cytometry. We found a statistically significant increase in SOD activity (P < 0.001) and TAS concentration (P < 0.05), whereas levels of IL-1β were significantly lower (P < 0.01). Likewise, a statistically significant decrease in the PDI (P < 0.05) was observed in subjects who performed Tai Chi during a period of 6 months. Our findings suggest that the practice of Tai Chi has both antioxidant and anti-inflammatory effects that are linked to the improvement of PD in older adults.

Marinating with calcium chloride had been employed to activate the endogenous proteolitic enzymatic system in muscle tissue. The activation of calpains leads to the disruption of major proteins responsible for myofilament structure. Nonetheless, intrinsic differences regarding enzymatic activity between different species need to be established, which concerns protein degradation and ultrastructural changes. In this study, four species-horse, chicken, rabbit and beef-were marinated in 150 mM CaCl 2 solution. Calpain activity was determined by low and high molecular weight protein degradations (SDS-PAGE) and light microscopy, which was compared to a non-treated control. All the studied species presented an increase in the number of low molecular weight bands, corresponding to the 30 kDa polypeptide that resulted from tropomiosin degradation. High molecular weight protein degradation corresponds to the formation of breakdowns and amorphous regions in tissue micrographs. These results support the evidence of meat quality improvement by calcium marination.

Overall, meat texture is composed of two types of toughness: primary toughness, because of mechanical resistance of the myofibrillar structure, and secondary toughness, by reason of connective tissue content. Primary toughness can be reduced during aging by intrinsic and extrinsic protease activity. Secondary toughness is determined by a given amount of epimysial and perimysial connective tissue, which cannot be reduced as no collagenases are naturally present in the muscle or produced by native meat microbial populations. The objective of this work was to study primary toughness reduction in meat from four animal species, i.e., beef, horse, rabbit and hen, employing M. Biceps femoris, by calpain activation with calcium chloride. Secondary toughness, expressed as hydroxyproline content, and contribution of both parameters to overall hardness were also studied. Marination with 150 mM CaCl 2 increased enzymatic activity in pre-rigor meat (horse and beef), but higher concentrations (250 mM) reduced enzymatic activity increments. Although beef marination considerably increased enzymatic activity, it did not reduce hardness, probably because of high collagen content. The high hydroxyproline concentration in beef and horse caused an overall hardness. Marinated horse meat had lower collagen content and a higher enzyme activity, resulting in less hard samples. As expected, pre-rigor meats, hen and rabbit, Blackwell Science, LtdOxford, UKJMFJournal of Muscle Foods1046-0756Copyright 2004 by Food & Nutrition Press, Inc., Trumbull, Connecticut.162141154Original ArticleEFFECT OF CALCIUM CHLORIDE MARINATION AND COL-LAGEN CONTENT M.L. PEREZ-CHABELA ET AL. 142 M.L. PEREZ-CHABELA ET AL.had low hardness values for both control and treated samples. Because CaCl 2 in high concentrations inhibits calpain activity, it was assumed that rabbit meat calpains were inhibited at concentrations as low as 150 mM. Therefore, calpains were active in control pre-rigor rabbit meat but were inactivated by CaCl 2 addition.

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