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PubMed1990

Colonization resistance of defined bacterial plaques to Streptococcus mutans implantation on teeth in a model mouth.

We investigated the ability of Streptococcus mutans C67-1 to colonize simple bacterial plaques and the effects of age and stability of the pre-formed plaque on colonization resistance. Mixed-plaques of Actinomyces viscosus WVU627, 'Streptococcus mitior' LPA-1, and Veillonella dispar OMZ193 were grown on tooth segments, mounted back to back for simulation of approximal sites in a model mouth for 66 h. S. mutans C67-1 was either included in the original inoculum or super-inoculated onto the developing plaque. Inclusion of S. mutans C67-1 did not alter the total viable counts, but the proportional composition changed due to inter-species interactions. Colonization resistance of the mixed-plaque samples developed within 24 h, although S. mutans C67-1 was always able to colonize these stagnation sites. Colonization resistance of 24-hour plaque against a fresh isolate, S. mutans CP3, was also studied. There was greater colonization resistance by the basic plaque to this organism, compared with S. mutans C67-1, although the reasons for this were not clear. These initial experiments demonstrate the way in which the factors involved in bacterial colonization resistance in microbial films on teeth can be studied under controlled conditions.

Actinomyces↗
PubMedDate not supplied

Quantifying heterogeneity: flow cytometry of bacterial cultures.

Flow cytometry is a technique which permits the characterisation of individual cells in populations, in terms of distributions in their properties such as DNA content, protein content, viability, enzyme activities and so on. We review the technique, and some of its recent applications to microbiological problems. It is concluded that cellular heterogeneity, in both batch and continuous axenic cultures, is far greater than is normally assumed. This has important implications for the quantitative analysis of microbial processes.

Bacteria↗
PubMed1990

[Colonization by pyocyanic bacillus and its treatment in cystic fibrosis].

In cystic fibrosis infection is localized to the bronchi and self-perpetuated by a disorder of mucociliary clearance. At a certain stage of the disease infection is caused by Pseudomonas aeruginosa (PA), and the patient cannot get rid of it as cystic fibrosis reduces his defence mechanisms against this organism, a naturally weak pathogen. The presence and significance of persistent bronchial PA infection result from complex phenomena which have been summarized as "an opportunistic organism in a host whose defences have been very peculiarly compromised". The toxicity of PA and the inappropriate inflammatory response of the host concur to create permanent alveolar lesions which are gradually spreading out. The effectiveness of antibiotics depends on the organism and its resistance, on pharmacokinetic factors bringing the drug in situ and on local conditions of redox, physico-chemical environment and nutrition. Other factors intervene more roughly, including patient's age, liver impairment, lung anatomy (excluded areas), general malnutrition and vitamin deficiencies. Thus, the part played by other treatments in the antibiotic therapy of cystic fibrosis can no longer be ignored, just as it is no longer sensible to limit the use of antibiotics to obvious infections. To evaluate the effectiveness of antibiotics is not easy, but it can be demonstrated beyond any doubt when the above mentioned factors are taken into account. The use of antibiotics creates practical problems relating to their cost, their dosage, their side-effects, the adequacy of therapeutic infrastructures and, above all, it raises the question of short- and long-term changes in microbial ecology.

Adolescent↗
PubMed1991

Performance and ruminal function development of young calves fed diets with Aspergillus oryzae fermentation extract.

Neonatal Holstein heifer (n = 72) and bull (n = 40) calves were used to study the effects of Aspergillus oryzae fermentation extract (Amaferm) on their performance and on rumen development. The starter diets were formulated to achieve Amaferm consumption of 0, .5, 1, or 3 g per calf daily. Calves were fed milk daily and allowed to consume starter and a mixture of alfalfa and bromegrass hay ad libitum. Weaning was when calves consumed 550 g of starter on 2 consecutive d. Weight gain and feed consumption were recorded weekly. Forty of the heifer calves, 10 from each treatment, were selected randomly to study the effects of Amaferm on ruminal fermentative development. Ruminal fluid samples were collected for pH, ruminal fermentation products, and for bacterial enumerations. Overall, Amaferm-supplemented calves were weaned 1 wk earlier than unsupplemented calves. They had higher total VFA, propionate, and acetate concentrations in the rumen than unsupplemented calves. Total anaerobic, hemicellulolytic, and pectinolytic bacterial counts were higher; cellulolytic bacterial counts tended to be higher for the Amaferm-supplemented calves than for controls. In general, Amaferm-supplemented calves had greater ruminal microbial activity than those not fed Amaferm.

Animal Feed↗
PubMed1989

[The identification of microorganisms from groundwater and characterization of their physiologic activities].

The microbiological method presented in this contribution allows the following investigations: --Identification of aerobic, heterotrophic environmentally-related organisms. --Investigation of different physiological activities of the test bacteria (e.g., degradation of different organic carbonaceous compounds, formation of extracellular enzymes). --Characterization of biological communities and their diversity. --Estimation of activities in environmental samples and mixed cultures. --Evaluation of a micro-site quality, e.g., reductions in the numbers of species or in a specific activity due to the effects of toxic substances. --Monitoring of the microbial community and its activities during biorestoration processes.

Bacteria↗
PubMed1991

Comparison of microbiologic assay methods for hemodialysis fluids.

To help prevent pyrogenic reactions and bacteremia in hemodialysis patients, the Association for the Advancement of Medical Instrumentation and the Centers for Disease Control recommend microbiologic assay of hemodialysis fluids at least monthly. Five commercially available assay systems were evaluated by using the membrane filtration technique with standard methods agar and trypticase soy agar as the standards for comparison. Each assay system was challenged with dialysate and reverse-osmosis water from local dialysis centers, aqueous suspensions of eight laboratory strains of gram-negative bacilli and nontuberculous mycobacteria, and a mixed microbial flora inoculated into reverse-osmosis water and laboratory-prepared dialysate. Mean viable counts from triplicate samples were obtained after incubation at 37 degrees C for up to 72 h. The efficiency of recovery varied with the specific type of microbial challenge. The SPC water sampler (Millipore Corp., Bedford, Mass.) was the most consistent in obtaining the highest viable counts. Other commercial systems were comparable to each other in overall performance. All assay systems tested provided an acceptable balance between microbial recovery and required sampling time, equipment, and expertise.

Bacteria↗
PubMed1991

Scanning electron microscopy of bacteria in the apical part of root canals in permanent teeth with periapical lesions.

The most apical 2 mm of the root canals of periapically diseased roots were examined for microorganisms by scanning electron microscopy (SEM). Bacteria in this area were observed in 10 out of 12 (83.3%) cases. The two remaining cases exhibited bacteria more coronally, with tissue remnants between the bacterial front and the apical foramen. Rod-shaped bacteria dominated, but filaments, spirochetes and cocci were also seen. Cocci and rods sometimes formed micro-colonies. Occasionally, cocci were seen attached to filaments forming "corn-cob"-like structures. Deposits resembling bacterial plaque were also found inside the root canal. SEM is useful for studying microbial topography of the apical root canal.

Bacteria↗
PubMed1989

Antibacterial effect of tetracaine hydrochloride (Pontocaine) in the aspect of exposure time--in vitro study.

Antibacterial effect of tetracaine hydrochloride was studied. Tetracaine hydrochloride (preservative free) were incubated with Staphylococcus aureus, coagulase negative staphylococcus and Pseudomonas aeruginosa respectively, for 18 hours and for 2 minutes. Then it was diluted and cultured on nutrient agar plate. Colony counts were done after 18 hours. In case of 18 hours incubation, there was no growth of microbials in 0.5%, 0.1% tetracaine hydrochloride, but there was no inhibitory effect of 0.02% tetracaine hydrochloride on growth of microbials, irrespective of inoculum amount. In case of 2 minutes incubation with 0.5% tetracaine hydrochloride, there was no difference between the amount of microbial inoculum and colony count. Above indicates that tetracaine hydrochloride has no inhibitory effect on bacterial growth after short exposure of less than 2 minutes.

Anti-Bacterial Agents↗
PubMed1990

[Microbiological diagnosis of lower respiratory tract infections].

Successful microbiological diagnosis of lower respiratory tract infections demands a close cooperation between clinician and clinical microbiologist. Because of the broad spectrum of possible respiratory pathogens precise requests are necessary for adequate laboratory procedures. The high rate of potential pathogens requires quantitative microbiological and cytological data in order to differentiate between colonisation and infection. Pathophysiological reactions on microbial colonisation of the bronchial tree may contribute to acute exacerbations of a chronic bronchitis. The precise role of microbial nocuous agents, however, remains to be clarified.

Bronchi↗
PubMedDate not supplied

[Characteristics of the transphase and transovarial transmission of Rickettsia sibirica by ixodid and argasid ticks].

Both the specific vector Dermacentor silvarum and the nonspecific one Ornithodoros papillipes are shown to become Rickettsia sibirica infected while sucking blood on the infected guinea pigs. Meanwhile, the specific vector D. silvarum is more sensitive to R. sibirica than the nonspecific. O papillipes. The infectivity of D. silvarum and O. papillipes ticks by R. sibirica was found to be dependent on the intensity of guinea pigs' rickettsemia. Transovarial transmission of Rickettsia has been established for the D. silvarum and O. papillipes ticks, but the Rickettsia titer in the infested D. silvarum larvae exceeded that O. papillipes. Survival of D. silvarum ticks infected by various concentrations of the R. sibirica microbial bodies was found to exceed that of O. papillipes.

Animals↗
PubMed1991

Effects of defaunation and various nitrogen supplementation regimens on microbial numbers and activity in the rumen of sheep.

Five sheep (average BW 62 kg) were fed 65% roughage: 35% concentrate diets (CP = 15%) in a 5 x 5 Latin square design to study the effects of combinations of defaunation and N supplements (soybean meal [SBM], corn gluten meal [CGM], blood meal [BM], urea, and casein) differing in ruminal degradation on ruminal microbial numbers and activity. Diets were fed twice daily (DM intake 1,759 g/d). Defaunation was accomplished with doses of 30 ml of alkanate 3SL3.sheep-1.d-1 for 3 d with 2 d of fasting. Treatment 1 (control) involved feeding faunated sheep a diet in which the supplemental N was 67% SBM N and 33% urea N. Treatment 2 involved feeding defaunated sheep the same diet as the control. Treatments 3, 4, and 5 involved feeding defaunated sheep diets in which the supplemental N source was either 67% CGM-BM N (CGM and BM combined on a 1:1 N ratio): 33% urea N, or 33% CGM-BM N:67% urea N or 33% CGM-BM N:33% urea N:33% casein N, respectively. Compared with the faunated control, defaunation (Treatments 2, 3, 4, and 5) increased (P less than .05) total direct counts of ruminal bacteria (2.7 vs 1.3 x 10(11)/ml), fungal zoospores (2.8 vs 1.4 x 10(5)/ml), and ruminal microbial protease activity (1.4 vs 1.0 mg azocasein/[ml ruminal fluid.h]). Defaunation did not have a consistent effect on ruminal microbial deaminase activity. Compared with the control, defaunation resulted in lower (P less than .05) total perchloric acid-soluble amino N in ruminal fluid at 4 and 10 h after the morning feeding. Defaunation did not decrease (P greater than .05) total free amino acid concentrations in ruminal fluid, but it altered the profile of free amino acids. Although defaunation increased (P less than .05) ruminal bacterial numbers, no increases in total microbial CP or OM concentrations in ruminal contents were observed.

Amino Acids↗
PubMedDate not supplied

[Effects of nifuroxazide on fecal flora in healthy subjects].

Effect of nifuroxazide on fecal flora was studied in 12 healthy volunteers receiving, in hazardous order and double-blind procedure, three six-days courses of treatment separated by eight-days spaces of time: the conventional dosage of 400 mg twice a day, a dosage of 1200 mg once a day, and placebo. Among six settled bacteriological index (wealth of the fecal flora, percentage of gram-negative bacteria, numbers of E. coli, Enterococcus, Clostridium and Bacteroides), no significant variation was found by means of statistical study between D0, D2 and D7, nor between the three courses of treatment. Therefore nifuroxazide, even in high dosage, does not injure integrity of microbial intestinal ecosystem under so defined experimental conditions, similar with clinical conditions.

Adult↗
PubMed1988

Post-processing microflora and the shelf stability of gari marketed in Port Harcourt.

Gari was examined for its post-processing microbial content. Aerobic mesophilic bacteria and fungi were isolated from all samples. The total viable bacterial counts ranged from 2.0 X 10(2) to 8.0 X 10(4) cfu/g. Fungal counts ranged from 1.0 X 10(2) to 1.5 X 10(4) cfu/g. The total viable counts of fresh samples were much lower than those of market and packaged samples. Bacillus, Micrococcus and Proteus spp. were the bacteria isolated, Aspergillus niger, Aspergillus flavus and Penicillium spp. the fungi. Food borne parasites and pathogens such as Staph. aureus and Clostridium perfringens were not found. The gari samples were quite stable, having a shelf life of 3-6 months. The water activities of the samples ranged from 0.52 to 0.68. Based on the microbial counts of the samples, the critical upper limit for the safety of gari was set at 10(4) cfu/g dry sample.

Bacteria, Aerobic↗
PubMed1989

A review of bioluminescent ATP techniques in rapid microbiology.

Use of firefly luciferase to assay adenosine triphosphate (ATP) extracted from microorganisms provides an easy means to enumerate microbes within minutes. The small amount of light produced is proportional to ATP and thus microbial number. The average bacterium contains around 10(-15) g ATP per cell. Present reagents permit detection of 10(3) cells per tube. Luminometers currently on the market detect about 10(-12) g ATP. Proper extraction of ATP from the microbes is an essential part of any protocol, as is the removal of non-microbial ATP from, for example, somatic cells also present in samples. The technique may be applied to a wide range of samples, for example food and beverages and clinical samples such as urine. The ATP assay gives a global measure of microbial numbers, i.e. it is not species specific unless a species separation step is included in the protocol.

Adenosine Triphosphate↗