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PubMed2003

Effects of fish farming on microbial enzyme activities and densities: comparison between three Mediterranean sites.

AIM: The effects of fish farming on microbial enzyme activities and heterotrophic bacterial density were investigated in three Mediterranean sites before and after the start of mariculture. METHODS AND RESULTS: Microbial activities were measured on water and sediment samples by using fluorogenic substrates specific for leucine aminopeptidase, beta-glucosidase and alkaline phosphatase (AP); bacterial counts were determined by Marine agar plates. SIGNIFICANCE AND IMPACT OF THE STUDY: Comparison of activity and abundance values obtained before and after the experiment showed that fish farming mainly affected the levels of microbial activities; they were significantly enhanced both in water and sediments, reaching an increase of 183.66 times for AP in Castellammare Gulf. After mariculture, no significant variations were recorded in heterotrophic bacterial density in the waters, while significant changes were observed in the sediments. Effects induced appeared to be extended not only to stations in which cages were located, but also to control sites far from the direct influence of fish farming.

Animals↗

PubMed2003

Influence of high salinities on the degradation of diesel fuel by bacterial consortia.

Microbial communities from three Argentinean saline soils were extracted and tested for their ability to degrade diesel fuel in liquid culture at salinities between 0% and 25%. In each case, the degradation process was continuously monitored by measuring oxygen consumption. Two communities (CR1 and CR2) showed nearly equal degrees of degradation across a salinity range of 0%-10% (the former degrading about 63% of the diesel fuel and the latter about 70% after 53 and 80 d, respectively). Furthermore, the degree of degradation was not significantly lower in the presence of 17.5% salt (58% and 65% degraded, respectively). A third community (El Zorro) showed a maximum turnover at 5% salt (79% diesel fuel degraded) and significant degradation (66%) at a salinity of 10%. However, the degree of degradation by this community clearly dropped at 0% and 15% salt. None of the communities were able to degrade diesel fuel in the presence of 25% salt, but the living cell counts showed that components of the microbial population survived the long-term exposure. The surviving portion is obviously sufficient to allow substantial restoration of the original community, as verified by the BIOLOG method. Isolates of the CR1 community were identified as members of the genera Cellulomonas, Bacillus, Dietzia, and Halomonas. In light of our investigations, the bioremediation of contaminated saline soils should be quite possible if the salinity of the soil water is lower than 15% or if it is reduced below this limit by the addition of water.

Agriculture↗

PubMed2001

Influence of copper-alloying of austenitic stainless steel on multi-species biofilm development.

AIMS: To investigate the bactericidal influence of copper-alloying of stainless steel on microbial colonization. METHODS AND RESULTS: Inhibition of bacterial adherence was investigated by monitoring (192 h) the development of a multi-species biofilm on Cu-alloyed (3.72 wt%) stainless steel in a natural surface water. During the first 120 h of exposure, lower numbers of viable bacteria in the water in contact with copper-containing steel relative to ordinary stainless steel were observed. Moreover, during the first 48 h of exposure, lower colony counts were found in the biofilm adhering to the Cu-alloyed steel. No lower colony or viable counts were found throughout the remainder of the experimental period. CONCLUSION: The presence of Cu in the steel matrix impedes the adhesion of micro-organisms during an initial period (48 h), while this bactericidal effect disappears after longer incubation periods. SIGNIFICANCE AND IMPACT OF THE STUDY: The application of Cu-alloyed stainless steels for bactericidal purposes should be restricted to regularly-cleaned surfaces.

Bacteria↗

PubMed2004

Comparison of biogenic amine profile in cheeses manufactured from fresh and stored (4 degrees C, 48 hours) raw goat's milk.

In this study, the evolution of microbial counts, biogenic amine contents, and related parameters (pH, moisture, and proteolysis) in goat cheese made from fresh raw milk or raw milk stored for 48 h at 4 degrees C was examined. In both cases the milk was nonpasteurized. This study was designed to evaluate the effect of milk quality on the profile of biogenic amines in relation to the evolution of the microbial population during cheese making. Cheese made from raw milk stored for 48 h at 4 degrees C showed the highest microbial counts and biogenic amine levels. The storage of milk under refrigeration caused significant increases in the levels of some microbial and biogenic amines during ripening, but not initially. Tyramine was the main biogenic amine in the two cheeses tested, followed by cadaverine. However, the main differences in amine contents between batches were found for putrescine, histamine, and beta-phenylethylamine, whose levels were more than twofold higher in samples from raw milk refrigerated for 48 h than in samples from fresh milk.

Animals↗

PubMed1999

Microbial shelf life determination of vacuum-packaged fresh beef treated with polylactic acid, lactic acid, and nisin solutions.

The effectiveness of polylactic acid, lactic acid, nisin, and combinations of the acids and nisin on extending the shelf-life of raw beef was determined. Fresh beef pieces (5 by 5 by 2.5 cm) were dipped in a solution of 2% low molecular weight polylactic acid (LMW-PLA), 2% lactic acid (LA), 200 IU of nisin per ml, or the combinations of nisin in either 2% LMW-PLA or 2% LA. The samples were then drip-dried, vacuum-packaged, and stored at 4 degrees C for up to 56 days. The beef surface pH values and numbers of psychrotrophic aerobic bacteria, psychrotrophic and mesophilic Enterobacteriaceae, Pseudomonas, and Lactobacillus were determined weekly for 56 days. The average surface pH values of the beef samples treated with 2% LMW-PLA or the combination of 200 IU of nisin per ml and 2% LMW-PLA were significantly reduced to 5.19 and 5.17, respectively, at day 0 (P < or = 0.05), while those decontaminated with 2% LA or 200 IU of nisin per ml in 2% LA solution were significantly decreased from 5.62 to 4.98 and 4.96, respectively. The 2% LMW-PLA, 2% LA, or the combinations of each acid and nisin showed immediate inhibitory effects on psychrotrophic aerobic bacteria (1.94, 2.36, 2.59, and 1.76 log reduction, respectively), psychrotrophic Enterobacteriaceae (1.37, 1.86, 1.77, and 1.35 log reduction, respectively), mesophilic Enterobacteriaceae (1.00, 1.00, 0.82, and 0.68 log reduction, respectively), and Pseudomonas (1.77, 1.57, 1.76, and 1.41 log reduction, respectively) on fresh beef (P < or = 0.05). The reduction was evident up to 56 days as seen by the numbers of Enterobacteriaceae and Pseudomonas (P < or = 0.05). Because there was no interaction between treatments and storage times, the data in each period were combined and presented as effect of treatments on overall microbial counts of fresh beef. It was found that 2% LMW-PLA, 2% LA, and the combinations of each acid and nisin significantly lowered the population of the above organisms compared with the untreated control, water, or nisin alone (P < or = 0.05).

Animals↗

PubMed2006

Inactivation of Saccharomyces cerevisiae and polyphenoloxidase in mango nectar treated with UV light.

Fresh mango nectar was processed by UV light at five flow rates (0.073 to 0.451 liter/min) and five UV light doses (75 to 450 kJ/m2) to evaluate total microbial load, Saccharomyces cerevisiae survival, and polyphenoloxidase activity. UV systems containing an inner mercury lamp (254 nm) each with intensity of 25 mW/cm2 were used as germicidal sources. In addition, mango nectar was treated for 15 min at 0.073 and 0.451 liter/min, stored at 3 degrees C, and evaluated periodically for total microbial count, yeast count, color, and polyphenoloxidase activity. The first-order kinetics modeling found that DUV-values in mango nectar ranged from 27.9 to 10.9 min (R2 > 0.950) and 26.0 to 11.8 min (R2 > 0.962) for total microbial count and yeast count, respectively. The maximum log reduction (CFU per milliliter) was 2.71 and 2.94 for total microbial count and yeast count, respectively, after 30 min of UV treatment at 0.451 liter/min. DUV-values ranging from 156 to 204 min were observed for polyphenoloxidase activity. The remaining polyphenoloxidase activity after 30 min of UV treatment at 0.451 liter/min was 19 +/- 4%. Initial microbial load and yeast in stored mango nectar were reduced in the range 2.86 to 3.41 and 1.82 to 1.97 log (CFU/ml) cycles, respectively. No substantial microbial growth was observed prior to 20 days of storage. Averages of 1,055 +/- 32, 803 +/- 32, and 710 +/- 37 enzyme activity units were observed in mango nectar UV processed at 0, 0.073, and 0.451 liter/min, respectively, during the entire storage period. However, mango nectar treated at 0.073 and 0.451 liter/min maintained a yellow and yellow-orange color, respectively, after 26 days of storage.

Catechol Oxidase↗

PubMed1996

Microbial detection.

There is a widespread need for commercial instrumentation for the rapid and inexpensive detection of microbial contamination of food, industrial waste water and clinical samples. A large number of detection methods have been developed utilizing the optical, electrochemical, biochemical and physical properties of microorganisms. The need for a device which can produce a rapid, accurate, sensitive, real-time analysis for clinical, industrial and environmental applications has led to considerable progress being achieved in recent years in the development of biosensors for microbial detection. This intense research has resulted in the commercialization of several instruments. Techniques used for the quantification of microorganisms are reviewed under the general categories of non-bioelectrochemical and bioelectrochemical methods.

Bacteriological Techniques↗

PubMed2006

Effects of high pressure homogenisation of raw bovine milk on alkaline phosphatase and microbial inactivation. A comparison with continuous short-time thermal treatments.

Raw whole milk of high microbial quality ( 58 degrees C), but markedly decreased above 200 MPa when Tin=24 degrees C (T2>60 degrees C). In contrast to inactivation induced by continuous short-time thermal treatments, ALP inactivation induced by HP homogenisation was clearly due to mechanical forces (shear, cavitation and/or impact) in the HP valve and not to the short (<<1 s) residence time at temperature T2 in the same valve. Inactivation of the three exogenous microorganisms led to similar conclusions. Homogenisation at 250 MPa or 300 MPa (Tin=24 degrees C) induced a 2-3 log cycle reduction of the total endogenous milk flora and a 1.5-1.8 log cycle reduction of inoculated List. innocua. Higher reduction ratios (2-4 log cycles) were obtained for the two other microorganisms. The highest levels of ALP inactivation corresponded to the highest extents of microbial reduction. Running the milk twice or three times through the homogeniser (recycling), keeping temperature T1 approximately 29 degrees C and pressure=200 MPa, increased homogenisation efficiency.

Alkaline Phosphatase↗

PubMed1992

[Persistence and transient conjunctival pathogen colonization before planned intraocular interventions].

The risk of a postoperative endophthalmitis is influenced by the presence of a significant bacterial colonisation of the conjunctiva before intraocular surgery. Between February and August 1990 we performed conjunctival smears in 481 patients 1) on the eve of the operation and 2) just before planned intraocular surgery, to evaluate a persistent or transient microbial colonisation of the conjunctiva. 352 patients showed insignificant ("negative") and 129 patients a significant ("positive") bacterial growth in the first conjunctival smear. 96% of the patients (n = 336) had a negative result in both smears. 30% of the patients (n = 37) with a positive conjunctival smear showed a persisting bacterial colonisation, whereas 70% of the patients (n = 92) had a transient colonisation of the conjunctiva with a negative second smear. As a persisting microbial colonisation of the conjunctiva may be an important factor for the development of postoperative endophthalmitis, we recommend prophylactic conjunctival smears before surgery to diminish the risk of intraocular infections after surgery.

Bacteria↗

PubMed2006

Bacterial contamination of keyboards: efficacy and functional impact of disinfectants.

BACKGROUND: Computers are ubiquitous in the healthcare setting and have been shown to be contaminated with potentially pathogenic microorganisms. This study was performed to determine the degree of microbial contamination, the efficacy of different disinfectants, and the cosmetic and functional effects of the disinfectants on the computer keyboards. METHODS: We assessed the effectiveness of 6 different disinfectants (1 each containing chlorine, alcohol, or phenol and 3 containing quaternary ammonium) against 3 test organisms (oxacillin-resistant Staphylococcus aureus [ORSA], Pseudomonas aeruginosa, and vancomycin-resistant Enterococcus species) inoculated onto study computer keyboards. We also assessed the computer keyboards for functional and cosmetic damage after disinfectant use. RESULTS: Potential pathogens cultured from more than 50% of the computers included coagulase-negative staphylococci (100% of keyboards), diphtheroids (80%), Micrococcus species (72%), and Bacillus species (64%). Other pathogens cultured included ORSA (4% of keyboards), OSSA (4%), vancomycin-susceptible Enterococcus species (12%), and nonfermentative gram-negative rods (36%). All disinfectants, as well as the sterile water control, were effective at removing or inactivating more than 95% of the test bacteria. No functional or cosmetic damage to the computer keyboards was observed after 300 disinfection cycles. CONCLUSIONS: Our data suggest that microbial contamination of keyboards is prevalent and that keyboards may be successfully decontaminated with disinfectants. Keyboards should be disinfected daily or when visibly soiled or if they become contaminated with blood.

Aspergillus↗

PubMed2006

Isoniazid's bactericidal activity ceases because of the emergence of resistance, not depletion of Mycobacterium tuberculosis in the log phase of growth.

BACKGROUND: It is believed that the cessation of isoniazid's early bactericidal activity during the initial phase of antituberculosis therapy is due to the depletion of Mycobacterium tuberculosis in the exponential phase of growth. We examined the veracity of this cornerstone belief. METHODS: We used an in vitro infection model in which M. tuberculosis was exposed to isoniazid concentration-time profiles encountered in human patients. Experiments were performed to examine the time-related changes in the total bacterial population, the isoniazid-susceptible subpopulation, and the isoniazid-resistant subpopulation. RESULTS: The cessation of microbial kill occurred between days 3 and 4 of isoniazid therapy, as occurs in patients. There were multiple logs of organisms in the exponential phase of growth remaining at the time when bactericidal activity ceased. The isoniazid-susceptible subpopulation was replaced by an isoniazid-resistant subpopulation after 80 h of therapy. The size of the isoniazid-susceptible subpopulation continued to decrease after the total population had ceased to decrease, whereas the resistant subpopulation remained in the exponential phase of growth. Resistance was due to single point mutations in the catalase-peroxidase gene and to reserpine-inhibitable efflux pumps. CONCLUSIONS: The age-old hypothesis that isoniazid's microbial killing of M. tuberculosis during log-phase growth ceases because of the depletion of this bacillary population needs to be modified.

Antitubercular Agents↗

PubMedDate not supplied

Pathogenesis of experimental endocarditis.

Numerous important observations concerning the pathogenesis of infective endocarditis have been made over the past 18 years. Many of these observations have been obtained with animal models of endocarditis in which an indwelling catheter has been used to produce predisposing endocardial lesions for subsequent infection. Unlike several previously used animal models, the catheter-induced endocarditis models have many characteristics similar to infective endocarditis in humans. Key findings regarding microbial adherence and persistence and the host response to endocardial infection have led to a better appreciation of the complex issues operative in the pathogenesis of endocarditis.

Animals↗

PubMed2002

On the risk of mortality to primates exposed to anthrax spores.

Current events have heightened the importance of understanding the risks from inhalation exposure to small numbers of spores of Bacillus anthracis. Previously reported data sets have not been fully assessed using current understanding of microbial dose response. This article presents an assessment of the reported primate dose-response data. At low doses, the risk to large populations of low doses of inhaled spores (e.g., < 100) is not insignificant.

Administration, Inhalation↗

PubMed1999

The influence of bacterial inoculants on the microbial ecology of aerobic spoilage of barley silage.

The aerobic decomposition of barley silage treated with two inoculants (LacA and LacB) containing mixtures of Lactobacillus plantarum and Enterococcus faecium was investigated over a 28-day period. Initially, yeast and bacterial populations were larger in silage inoculated with LacA than in silage treated with LacB or water alone (control). Differences in the succession of yeasts in silage treated with LacA were observed relative to the other two treatments. From silage treatment with LacA, Issatchenkia orientalis was the most prevalent yeast taxon over all of the sample times, and the filamentous fungus Microascus brevicaulis was also frequently isolated at later sample dates (> or = 14 days). In contrast, Saccharomyces exiguus was the most prominent yeast recovered from silage treated with LacB and water alone on days 2 and 4, although it was supplanted by I. orientalis at later sample times. Successional trends of bacteria were similar for all three treatments. Lactobacillus spp. were initially the most prevalent bacteria isolated, followed by Bacillus spp. (primarily Bacillus pumilus). However, the onset of Bacillus spp. prominence was faster in LacA silage, and Klebsiella planticola was frequently recovered at later sample times (> or = 14 days). More filamentous fungi were recovered from LacA silage on media containing carboxylmethylcellulose, pectin, or xylan. The most commonly isolated taxa were Absidia sp., Aspergillus flavus, Aspergillus fumigatus, Byssochlamys nivea, Monascus ruber, Penicillium brevicompactum, Pseudoallescheria boydii, and M. brevicaulis. The results of this study indicated that the two bacterial inoculants incorporated into barley at the time of ensilage affected the microbial ecology of silage decomposition following exposure to air. However, neither of the microbial inoculants effectively delayed aerobic spoilage of barley silage, and the rate of decomposition of silage treated with one of the inoculants (LacA) was actually enhanced.

Aerobiosis↗

PubMed2002

Factors influencing oral colonization in premature infants.

BACKGROUND: Factors influencing the oral flora of premature infants have not been adequately investigated. OBJECTIVE: To investigate the effects of gestational age and of anti-bacterial therapy on the oral flora of premature infants. METHODS: Oral cultures were obtained at age 1 day and age 10 days from 65 premature infants, divided into three groups: a) 24 neonates of 30-34 weeks gestation who did not receive ABT, b) 23 neonates of 30-34 weeks gestation who received ABT, and c) 18 neonates < 30 weeks gestation who received ABT. RESULTS: Oral bacterial colonization increased from day 1 to day 10 of life. In 24-34 week neonates, gestational age did not affect early bacteremia or oral colonization at birth. Neither gestational age nor ABT affected late bacteremia or oral colonization at day 10. In 30-34 week neonates with ABT, the oral flora consisted mainly of non-Escherichia coli gram-negative bacteria, whereas those who did not receive ABT grew mainly alpha-hemolytic streptococci, Klebsiella pneumoniae and E. coli. In neonates < 30 weeks who received ABT the oral flora were mainly coagulase-negative staphylococci. Oral colonization with anaerobes was zero and colonization with fungi was minimal. CONCLUSIONS: Acquisition of oral bacteria rose from day 1 to day 10 of life, regardless of gestational life or ABT. On day 10 of life, the spectrum of oral bacterial flora changed following ABT and consisted mainly of coagulase-negative Staphylococcus and non-E. coli gram-negative bacteria. Oral colonization showed few fungi but no anaerobes. These microbiologic observations merit attention when empirical anti-microbial therapy is considered in premature infants suspected of having late-onset sepsis.

Age Factors↗

PubMed2005

[Effects of returning maize straw into field on dynamic change of soil microbial biomass C, N and P under different promoted decay condition].

A 2-year field experiment of wheat-maize rotation was conducted on a cinnamon soil of east Hebei Province to study the effects of returning maize straw into field on the dynamics of soil microbial biomass C, N and P, and their relationships with soil nutrients and enzyme activities. The results showed that under the condition of returning maize straw combined with applying chemical fertilizer to adjust straw C/N, the application of effective microorganisms could increase soil microbial biomass C, N and P in each crop growth period, advance their peak time, and better regulate soil nutrient supply, compared with no application of effective microorganisms. Soil microbial biomass had a significantly positive correlation with soil enzyme activities, but its correlation with soil hydrolysable N and available P was strongly affected by crop growth and fertilization system.

Carbon↗

PubMed2001

Microbiological quality and shelf life modeling of ready-to-eat cicorino.

Growth of the microbial population resident in ready-to-use fresh cut cicorino, a variety of Chichorium intybus, was determined in the various preparation steps with the aim of defining the hazard critical control points. The investigation concerned cut cicorino from two producers. During the process a 1- to 1.5-fold increase of microbial counts was observed, and the retail product showed values of 10(5) to 10(6) CFU/g. The shelf life of the product was kinetically modeled in order to check the effects of storage temperature and assess the microbial indexes most relevant for hygiene and quality of the distributed product. A modified Gompertz function described the kinetics of microbial growth and allowed definition of a stability time and its dependence on temperature. Stability times were of 0.3, 3.7, and 4.7 days at storage temperatures of 20, 10, and 5 degrees C, respectively. Q10 (the fold decrease of stability time for an increase of 10 degrees C) was 3.85. The results from this study may be used to predict the effects of temperatures experienced in the distribution chain on bacterial levels in cicorino.

Bacteria↗

PubMed2000

On estimating the probability of aperiodic outbursts of microbial populations from their fluctuating counts.

The irregular sequence of counts of a microbial population, in the absence of observable corresponding environmental changes (e.g., temperature), can be regarded as reflecting the interplay of several unknown or random factors that favor or inhibit growth. Since these factors tend to balance one another, the fluctuations usually remain within bounds, and only by a coincidence--when all or most act in unison--does an 'outburst' occur. This situation can be represented mathematically as a sequence of independent random variables governed by a probability distribution. The concept was applied to reported microbial counts of ground meat and wastewater. It is found that the lognormal distribution could serve as a model, and that simulations from this model are indistinguishable from actual records. The parameters of the lognormal (or other) distribution can then be used to estimate the probability of a population outburst, i.e., an increase above a given threshold. Direct estimation of the outburst probability based on frequency of occurrence is also possible, but in some situations requires an impractically large number of observations. We compare the efficiency of these two methods of estimation. Such methods enable translation of irregular records of microbial counts into actual probabilities of an outburst of a given magnitude. Thus, if the environment remains 'stable' or in dynamic equilibrium, the fluctuations should not be regarded merely as noise, but as a source of information and an indicator of potential population outbursts even where obvious signs do not exist.

Animals↗