To determine ability of lactobacilli strains indigenous for oral cavity of healthy persons to adhesion, autoaggregation, surface hydrophobicity, coaggregation and formation of biofilms.
Twenty-three anatagonistically active isolates of lactobacilli, including 5 strains of Lactobacillus plantarum, 6--L. rhamnosus, 4--L. paracasei, and 8--L. fermentum, were studied. Characteristics of lactobacilli associated with adhesion, autoaggregation, surface hydrophobicity, coaggregation, and formation of biofilms were determined.
Bacteria were characterized by high and intermediate level of adhesion, autoaggregation, surface hydrophobicity, expressed ability to form biofilms and different coaggregation activity relative to test-strains Staphylococcus aureus, Escherichia coli, Candida albicans, Pseudomonas aeruginosa, and Bacillus subtilis.
Studied characteristics of lactobacilli could be used for development of new probiotics aimed at stabilization of oral cavity normoflora.
A new probiotic Biosporin and other commercial biopreparations based on aerobic sporulating bacteria of the Bacillus genus have been comparatively studied for their specific activity and safety. It has been established that only Biosporin is characterized by expressed antagonistic activity in respect to a wide range of pathogenic and conditionally pathogenic microorganisms including those with multiple resistance to antibiotics. Biosporin is also characterized by the absence of any negative action on the organism of animals even in the doses considerably exceeding those recommended for use.
Dental caries is an infectious process which ultimately destroys the tooth. Streptococcus mutans is considered to be the main agent causing this disease. If microorganisms with antagonistic action on S. mutans were found, they might provide a way of avoiding or controlling the disease. Within the framework of the Oral Microbial Ecology approach, the aim of this project was to identify S. mutans strains with antagonistic effect upon S. mutans. Saliva samples were taken from 66 children and cultured on Blood agar and Mitis Salivarius Bacitracin agar. They were incubated at 37 degrees C in anaerobic atmosphere for 48 hours, after which bacteria were counted and biochemical tests performed on colonies compatible with S. mutans. Antagonistic effect was determined using the double layer in agar technique. In children without and with caries, the frequency of S. mutans was 91.7% and 96.7%, respectively. In the group of patients without caries, only two strains had no antagonistic action, and three strains had full antagonistic action (100%), while the rest showed different kinds of inhibitory action. In the group of patients with caries, only 5 strains had no antagonistic action, 32 strains had full antagonistic action (100%) and the rest had variable inhibitory action. To conclude, 112 S. mutans strains with high antagonistic potential were identified, which, after other requirements are fulfilled, could be used in caries prevention or control strategies.
The natural microflora of cold-smoked fish at the end of shelf-life are lactic acid bacteria (LAB). Some of these display a capacity to inhibit spoilage as well as several strains of pathogenic micro-organisms, e.g. Listeria monocytogenes which is isolated frequently from cold-smoked salmon (CSS). Eight batches of sliced vacuum-packed CSS from Norway, Scotland and Spain were collected at retail. Packs were stored at 5 degrees C and examined for chemical and microbiological characteristics, at purchase date and at expiration date. pH, water activity and salt content were similar to available data on lightly preserved fish products. There was a consistent pattern in the development of the microflora on CSS; the initial level of LAB was low on freshly produced CSS (10(2) cfu g(-1)); however, storage in vacuum packaging at refrigeration temperature was elective for LAB. At the end of the stated shelf-life these micro-organisms, represented mainly by Lactobacillus spp., attained ca.10(7) cfu g(-1) while Enterobacteriaceae counts were consistently lower (10(5) cfu g(-1)), which indicates the ability of LAB to grow and compete with few carbohydrates available and in the presence of moderate salt concentrations. L. monocytogenes was not found in any sample. Forty-one percent of LAB strains isolated exhibited inhibitory capacity against Listeria innocua, in a plate assay. A majority of the inhibitory effects were non-bacteriocinogenic, but nevertheless were very competitive cultures which may provide an additional hurdle for improved preservation by natural means.
The potential use of the commercial biocontrol products Serenade (Bacillus subtilis QST-713) and Trichodex (Trichoderma harzianum Rifai strain T39) to inhibit the postharvest pathogenic molds Penicillium crustosum and Mucor circinelloides was investigated. Both products exhibited antagonistic activity in vitro against the pathogens, reducing their growth at different levels. In addition, epiphytic yeasts isolated from peaches were identified as Candida maltosa, Pichia fermentans, and Pichia kluyveri by PCR-restriction fragment length polymorphism of internal transcribed spacer regions and screened for antagonistic activity against the same molds. The efficacy of biocontrol in vitro was dependent on the concentration of the yeast cells. Optimal yeast concentrations were above 10(7) CFU ml(-1). However, C. maltosa and P. fermentans were more effective than P. kluyveri in inhibiting molds. The exclusion of antifungal metabolite production and direct competition for nutrients or space with the pathogens was proposed as the mechanism of biocontrol. Application of biocontrol agents directly on artificially wounded peach fruits significantly reduced the incidence of mold rot during storage at 20 degrees C.
To choose lactobacilli-contained probiotic for complex treatment of acute enteric infection caused by Klebsiella in infants.
On the basis of bacteriological analysis the group consisting of 40 infants with acute enteric infection caused by Klebsiella was formed. Efficacy of three probiotic preparations--lactobacterin, vitaflor, and biobacton--was assessed depending on biological features of causative agents and contents of lactobacilli and bifidobacteria in obligate gut microflora. Intraspecies antagonistic characteristics of manufacturing strains of lactobacilli against 9 clinical isolates of K. pneumoniae and 8 strains of indigenous lactoflora, as well as interspecies antagonism between Klebsiella and probiotic and indigenous strains of lactoflora were studied.
It was shown that complex therapy of Klebsiella infection in infants using vitaflor or biobacton promoted elimination of K. pneumoniae and restoration of indigenous microflora which became apparent in significant increase of titer of lactobacilli. In vitro maximal antagonism to K. pneumoniae was noted for vitaflor, lactobacterin and heteroenzyme autostrains of ill children's lactoflora. Contrantagonism to lactoflora was typical for slowly growing strains of Klebsiella.
It is therapeutically rational to use vitaflor, which promotes rapid elimination of infectious agent, in initial phase of acute infection caused by Klebsiella, and biobacton, which increases the titers of indigenous lactoflora, in phase of convalescence.
Foodborne salmonellosis constitutes a major health problem in many countries. Moreover, the costs associated with salmonellosis could be considerable. There are thus strong arguments for preventive efforts. Ambitious, often government-sponsored, programmes aimed at preventing and controlling salmonellosis in for instance, poultry production represent one alternative to lower salmonellosis-related illness and economic costs. On the other hand, such comprehensive programmes are rather resource-demanding. From the economic point of view the key problem is to find the optimal level for prophylactic measures. The purpose of this study is to compare two different approaches to preventing poultry-borne salmonellosis among humans. We identify and compare the economic costs of illness due to poultry-borne salmonellosis and the costs of salmonella control in England and Wales and Sweden, respectively. An alternative option is then introduced: the concept of competitive exclusion (CE). Our results show that the cost of illness constitutes the major part of the total cost in England and Wales, whereas in Sweden, the control cost amounts to 95% of the total cost. By using the CE concept, the cost of illness due to poultry-borne salmonellosis in England and Wales could be reduced by at least GB pound 12.6 million. These advantages apply to individuals, producers, and to society, and we thus conclude that the CE concept is a very cost-effective way of using scarce resources.
Different amounts of enterotoxin A-, B-, and C1-producing staphylococci were added to dry sausage prepared by normal processes, either alone or in conjunction with a starter culture (micrococci and lactobacilli). The sausage was examined after 0, 3, 7, 14, and 30 days for staphylococci, micrococci, and lactobacilli, and measurements were made of water activity, pH, enterotoxin, and thermostable nuclease. The results showed that in the absence of starter culture measurable amounts of enterotoxin A were formed in a 200-g sample of dry sausage in 3 days, the level of Staphylococcus aureus infection being over 10(6) cells/g. Enterotoxin B was not found, although the total number of staphylococci was over 10(8) cells/g. Enterotoxin C1 was observed when the Staphylococcus count was about 8 X 10(7) cells/g, but was no longer detectable after 7 days. The starter culture prevented the production of enterotoxin A in all cases investigated. By contrast, a very high-level inoculation of an enterotoxin C1-producing strain gave a positive result after 3 days of incubation even in the presence of a starter culture. Heat-stable nuclease was observed in all sausages to which enterotoxin-producing staphylococci were added. The cell count determined in a sample of sausage had no definite correlation with the thermonuclease activity of the sample.
Produce Safety and Microbiology Research Unit, U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan Street, Albany, California 94710, USA. firstname.lastname@example.org
Escherichia coli O157:H7 can survive in low numbers in soil and on plants. Occasionally, conditions may occur in the field that lead to contamination of produce. Survival of enteric pathogens in the field is controlled to a certain extent by complex interactions with indigenous soilborne and seedborne epiphytes. Identifying these interactions may assist in developing strategies to improve produce safety. Two epiphytes were isolated from pathogen-contaminated plants that interact differently with E. coli O157:H7. Wausteria paucula enhanced the survival of E. coli O157:H7 six-fold on lettuce foliage grown from coinoculated lettuce seed. In contrast, Enterobacter asburiae decreased E. coli O157:H7 survival 20- to 30-fold on foliage. Competition also occurred in the rhizosphere and in plant exudate. This competition may be the result of E. asburiae utilization of several of the carbon and nitrogen substrates typically present in exudate and also used by E. coli O157:H7. Hence, competition observed on the plant may involve one or more nutrients provided by the plant. In contrast, a different mechanism may exist between E. coli O157:H7 and W. paucula since commensalism was only observed on foliage, not in the rhizosphere or plant exudate. Good agricultural practices that encourage the growth of competing bacteria, like E. asburiae, may reduce the incidence of produce contamination.