Proteolytic activity of molds and their metabiotic association with Salmonella in a model system.

The aim of this study was to investigate the proteolytic ability of some strains of aspergilli, fusaria, and penicillia and the metabiotic effect of Fusarium oxysporum and Penicillium expansum on Salmonella. The proteolytic activity of the target molds was determined on tomato juice agar and tomato juice, whereas the metabiotic effect of F. oxysporum and P. expansum on Salmonella was assessed in a model system consisting of tryptone soy broth with different amounts of tomato juice added. Fusaria, some aspergilli, and one strain of penicillium showed a proteolytic activity on tomato juice agar. In addition, Salmonella survival was enhanced in tryptone soy broth plus 20 or 50% tomato juice in the model system previously inoculated with F. oxysporum.

Suitability of bifidobacteria and thymol as biopreservatives in extending the shelf life of fresh packed plaice fillets.

AIMS: The present study was aimed to evaluate the microbiological and sensory characteristics of biopreserved packed fresh plaice (Pleuronectes platessa), during storage. METHODS AND RESULTS: Fish samples were treated with a Bifidobacterium bifidum strain and thymol as preservatives, stored at different temperatures (4 and 12 degrees C) and package atmospheres (in air, under vacuum, modified atmosphere). Data about the total viable count (TVC) were used to predict the shelf life of the fish fillets as affected by the preservatives used and the storage conditions. Data obtained revealed that B. bifidum could perform an efficient synergy with thymol, in controlling the hygiene biological markers. Besides, the tested bifidobacterial species, combined with low storage temperature and anoxia/hypoxia, showed a great efficacy against the main fresh packaged fish spoilage species (Pseudomonas spp., Photobacterium phosphoreum). CONCLUSIONS: The studied technique could be considered effective in fresh fish spoilage control. SIGNIFICANCE AND IMPACT OF THE STUDY: Great interest is developing on food biopreservation, because of the ever increasing needs to protect consumers' and environment's health, and to revalorize some important food characteristics, such as naturalness and authenticity, without leaving the safety aside.

Use of chitosan to prolong mozzarella cheese shelf life.

This study was undertaken to evaluate the feasibility of using chitosan, a natural antimicrobial substance, to improve the preservation of a very perishable cheese. The effectiveness of chitosan to inhibit the growth of spoilage microorganisms in Mozzarella cheese was studied during refrigerated storage. A lactic acid/chitosan solution was added directly to the starter used for Mozzarella cheese manufacturing. Mozzarella cheese samples were stored at 4 degrees C for about 10 d and microbial populations as well as the pH were monitored. Results demonstrated that chitosan inhibited the growth of some spoilage microorganisms such as coliforms, whereas it did not influence the growth of other microorganisms, such as Micrococcaceae, and lightly stimulated lactic acid bacteria.

Development of a structured model for batch cultures of lactic acid bacteria.

A combined stochastic-deterministic model able to predict the growth curve of microorganisms, from inoculation to death, is presented. The proposed model is based on the assumption that microorganisms can experience two different physiological states: non-proliferating and proliferating. The former being the physiological state of the cells right after their inoculation into the new extracellular environment; the latter the state of microorganisms after adaptation to the new medium. To validate the model, a Lactobacillus bulgaricus strain was tested in a medium at pH 4.6 at two different temperatures (42 degrees C and 35 degrees C). Curves representing the bacterial growth cycle were satisfactorily fitted by means of the proposed model. Moreover, due to the mechanistic structure of the proposed model, valuable quantitative information on the following was obtained: rate of conversion of non-proliferating cells into proliferating cells, growth and death rate of proliferating cells, and rate of nutrient consumption.

Evaluation of recovery methods to detect faecal streptococci in polluted waters.

AIMS: This paper compares the faecal streptococci count on 25 samples of polluted waters obtained with three techniques: most probable number (MPN), membrane filtration (MF) and pour plate (PP) methods. Although the PP method is a simple technique, familiar to water bacteriologists, it is not recommended in the international methods. METHODS AND RESULTS: For the MPN method, azide dextrose broth and ethyl violet azide broth were employed. For the MF technique, Millipore filters were placed onto azide maltose agar (KF agar), while for the PP method, 1 ml of a decimal water dilution was added to (Kennel Faecal) KF medium. Regression analysis and Friedman's ANOVA were performed to determine the relationship between faecal streptococci counts obtained with the three techniques. Statistical analysis of the results showed that the MPN, MF and PP techniques were equally valid with respect to faecal streptococci enumeration in polluted waters. CONCLUSION: Since the PP method was found to be as good as the other techniques, it may be preferred in polluted waters. It is more economical in terms of both time and materials than the MPN count, and it is as accurate as the MF count. SIGNIFICANCE AND IMPACT OF THE STUDY: This study indicates that the PP method, although not recommended internationally, is a reliable alternative to MF and MPN.

The occurrence of Aeromonas spp. in natural mineral water and well water.

The presence of motile Aeromonas spp. in natural mineral water (NMW) and drinking well water in the area of Lecce (Italy) was investigated. Aeromonas spp. were not detected in any of the 60 NMW samples either by the direct and enrichment method. From a total of 20 wells, five were found to contain Aeromonas species with cell number ranging from 26 to 1609 250 ml(-1). In two wells the presence of Aeromonas spp. was not associated to the presence of faecal indicators, i.e. coliforms and faecal coliforms. Sixty-five Aeromonas spp. strains isolated in this survey were identified at species level and some were examined for haemolysis, Voges Proskauer reaction, lysine decarboxylase and sorbitol fermentation, tests which had been previously shown to correlate with production of enterotoxin/cytotoxin. Isolates identified as A. hydrophila and A. sobria showed potentially virulent properties.

In vitro survival of Listeria monocytogenes in human amniotic fluid.

A Listeria monocytogenes strain (CA01/93), haemolytic and virulent in mice, was inoculated in 16 samples of sterile human amniotic fluid to study the growth curves and to provide more information about the pathophysiology of the microorganism in pregnancy. A control test for every analysis was performed with an Escherichia coli strain (CN 02/95). Regardless of the amniotic fluid samples were taken at 34th-39th week of gestation, when it expresses maximum ability to inhibit growth of E. coli, the growth curves of L. monocytogenes do not show any bactericidal (only bacteriostatic) activity of the amniotic fluids against the tested strain. This gives an interesting result about the pathogenesis of the infection in pregnancy and about the potential environmental contamination due to long surviving times of the microorganism in-amniotic fluid.

Fate of Escherichia coli O157:H7 in unpasteurized milk stored at 8 degrees C.

Escherichia coli O157:H7 and verocytotoxins were not found in any of 100 unpasteurized milk samples obtained from the bulk tanks of eight dairy farms located in the Puglia and Basilicata areas. Seven E. coli O157:H7 (EHEC) strains were inoculated separately into raw milk samples and then examined periodically to determine the fate of EHEC as influenced by the storage temperature (8 degrees C) and time. There was essentially no change in the viable population of three EHEC strains for up to 14 d. The remaining four strains showed an increase in population from < 2 log to 3 log cfu ml-1 in a time period of between 9 and 17 d. The results indicate good survival or even multiplication of E. coli O157:H7 in raw milk when stored at 8 degrees C and reaffirm the need for pasteurization and holding the milk at < or = 5 degrees C.

Survival of Escherichia coli O157:H7 in yoghurt during preparation and storage at 4 degrees C.

Cow's milk was inoculated with ca 10(3) and 10(7) cfu ml-1 Escherichia coli O157:H7. After fermentation at 42 degrees C for 0-5 h, the yoghurt was stored at 4 degrees C. Two kinds of yoghurt were used: traditional yoghurt (TY), made with Streptococcus thermophilus and Lactobacillus bulgaricus starter cultures, and 'bifido' yoghurt (BY), made with the two starter cultures plus Bifidobacterium bifidum. After 7 d E. coli O157:H7 decreased from 3.52 to 2.72 log10 cfu ml-1 and from 7.08 to 5.32 log10 cfu ml-1 in TY, and from 3.49 to 2.73 log10 cfu ml-1 and from 7.38 to 5.41 log10 cfu ml-1 in BY. The pH values of yoghurt dropped from 6.6 to 4.5 and 4.4 in TY (for low and high pathogen inocula, respectively), and from 6.6 to 4.6 and 4.5 in BY (for low and high pathogen inocula, respectively).

Factors affecting nPCR in hemodialysed patients.

The determination of dialysis adequacy is difficult and definitions are in a state of flux (Lindsay). In fact, after fifteen years from the introduction of urea kinetics into clinical practice, nephrologists still do not agree on recognizing the real utility of it. Gotch and Sargent in their mechanistic analysis of the NCDS indicated that the dose of small molecules removal could be defined by Kt/V urea. The results of the NCDS were depicted in a three-variable plot in which six domains could be seen. Several reports have documented malnutrition as being frequently present in patients on maintenance hemodialysis. It is generally accepted that a suboptimal nutritional status is associated with an increased morbidity and may adversely affect rehabilitation and the quality of life. In 1989 Lindsay et al showed that low levels of Kt/V corresponded with low levels of nPCR and found a direct correlation between the two parameters. On this basis, they suggested the hypothesis of nPCR dependence on Kt/V. The Authors showed a good correlation (r = 0.73) between nPCR and Kt/V in 55 patients. This work aims to evaluate the correlation between Kt/V and nPCR, real age and dialytic age in a dialytic population in Southern Italy, during a long period of observation (six years, follow up 2,692 months). One hundred and thirty-four patients were studied in six years of observation. Follow up: 2,692 months. Twenty-six patients died during the observation period. The simple regression analysis of nPCR vs. Kt/V, real age and dialytic age was performed in 63 anuric patients.(ABSTRACT TRUNCATED AT 250 WORDS)