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PubMed1999

Mulundocandin, an echinocandin-like lipopeptide antifungal agent: biological activities in vitro.

Mulundocandin (MCN) is an antifungal lipopeptide which belongs to the echinocandin class of antimycotic agents. MCN exhibited good in vitro activity against Candida albicans and C. glabrata isolates with MIC ranges of 0.5-4.0 microg/ml and 2.0-4.0 microg/ml, respectively. MCN also exhibited some activity against C. tropicalis isolates (MIC range 1.0-8.0 microg/ml). However, MCN was poorly active against other non-albicans isolates and was inactive against Cryptococcus neoformans, Aspergillus species and Trichophyton. MCN appeared to exert its antifungal activity through preferential inhibition of germ tube formation (MIC-HY 0.015-0.03 microg/ml) and was typically less active on the yeast form (MIC 0.5-4.0 microg/ml). In kill-curve experiments 99.9% reductions in cell viability were observed following 8 hours exposure to MCN at 4 x MIC and 8 x MIC and after 5 hours exposure to 16 x MIC.

Antifungal Agents↗

PubMed1990

Comparison of automated and manual methods for islet isolation.

The authors used the principal features of a collagenase perfusion technique and an automated dissociation technique to determine if islets could be isolated from the large mammal pancreas and to compare the effects of the two methods on isolated islets. The pancreases of 16 dogs were cannulated and perfused with collagenase at 4 degrees C, then warmed to 37 degrees C. Group 1 (eight) pancreases were perfused at 37 degrees C until digested, then dissociated manually by teasing and trituration. Group 2 (eight) pancreases were transferred to a closed chamber for continued collagenase digestion and dissociation at 37 degrees C. Islets were purified using identical Ficoll gradients. Aliquots were stained with dithizone and evaluated for number, size and purity. Total islet volume was calculated. Group 2 pancreases were thoroughly digested leaving only a few residual ducts, but undigested fragments persisted in group 1 pancreases. Islet size was similar in both groups. There was a greater islet volume before and after Ficoll purification in group 2, but the difference was not significant. Purity was greater than 90% in both groups. Perifusion with 28 mM glucose elicited a biphasic insulin release from islets in both groups. The data show that the combined protocol enables mass isolation of purified islets from the canine pancreas. Compared with the manual technique, the automated protocol for pancreas dissociation tends to improve the yield of islets without compromising islet size and viability. It provides the advantages of a closed system with increased control over the extent of collagenase digestion.

Animals↗

PubMed1990

Inhibition of the bacteriolytic effect of beta-lactam-antibiotics on Staphylococcus aureus by the polyanionic drugs suramin and Evans Blue.

The anionic polyelectrolytes suramin and Evans Blue inhibited different autolytic systems involved in wall growth and wall turnover of growing staphylococci and in wall autolysis of resting bacteria. Moreover, both substances lowered the beta-lactam-induced pre-lytic release of cytoplasmic constituents from staphylococci, and inhibited the beta-lactam-induced bacteriolysis as well as the loss of viability. The protective effects of these sulfonated drugs against bacteriolysis were also monitored by electron microscopy. Some medical implications of our results are discussed.

Anti-Bacterial Agents↗

PubMed1993

Cell function and viability in glucose polymer peritoneal dialysis fluids.

OBJECTIVE: To investigate the biocompatibility profile of a new peritoneal dialysis fluid containing glucose polymer (GPF). DESIGN: Viability and function of peripheral neutrophils (PMN) from healthy donors and cultured human peritoneal mesothelial cells were assessed in vitro after exposure to dialysis fluids. Phagocytosis, leukotriene B4 synthesis, and respiratory burst activation were measured following stimulation with serum-treated zymosan (STZ) or opsonized Staphylococcus epidermidis (S. epidermidis). Bacterial growth in the fluids was also investigated. In vivo pH equilibration of GPF and subsequent respiratory burst activation following incubation in spent dialysate were studied. RESULTS: For all the host defense parameters measured, commercial dialysis fluids (Dianeal; 1.36% and 3.86% glucose) and GPF (pH 5.2) were significantly more inhibitory than the control buffer (pH 7.3). Mesothelial cell viability was reduced by all the fluids tested irrespective of pH. Glucose polymer fluid was significantly more inhibitory than Dianeal 1.36% for STZ phagocytosis and respiratory burst activation. In contrast, it was less suppressive than Dianeal 3.86% for LTB4 synthesis. For all parameters tested, except LTB4 generation, there was a marked effect of pH, with GPF being significantly more inhibitory at pH 5.2 than at pH 7.3. None of the fluids tested supported the growth of S. epidermidis, although the viable counts in GFP were significantly higher than in Dianeal. Fluid inhibition of PMN respiratory burst activation and cytotoxicity were reduced in a time-dependent manner following increasing dwell time in vivo. CONCLUSIONS: GPF does not appear to be significantly different from Dianeal as far as host defense parameters are concerned. However, the cell viability and bacterial survival data suggest some possibly negative aspects of this fluid formation.

Biocompatible Materials↗

PubMed2002

The effect of a quaternary ammonium biocide on the performance and characteristics of laboratory-scale rotating biological contactors.

AIMS: To study the effect of a quaternary ammonium biocide, didecyldimethylammonium chloride (DDAC), on the treatment efficiency of laboratory-scale rotating biological contactors (RBCs) as well as their component biofilms. METHODS AND RESULTS: Biofilms were established on the RBCs and then exposed to 0-160 mg l(-)1 (p.p.m.) DDAC at a flow rate of 2.5 l h(-1). The treatment efficiency of the RBC and the microbial activity of the biofilms were markedly decreased when 40 mg l(-1) DDAC or greater were applied to the units. However, DDAC had no effect on the number of viable bacteria in the biofilms when DDAC concentrations up to 80 mg l(-1) were applied to the RBCs. No viable bacteria could be detected in the biofilm when DDAC was applied at 160 mg l(-1). Extended observation over a further 40 d with 20 and 80 mg l(-1) DDAC showed similar results in terms of chemical oxygen demand removal, ATP content and viability of biofilms compared with those values over the first 12 d of exposure. CONCLUSIONS: There was at least a fourfold difference in the susceptibility of planktonic and sessile bacteria to DDAC. Cells acclimatized to DDAC did not increase their capability to degrade normal carbon sources or DDAC under the conditions used in this study. SIGNIFICANCE AND IMPACT OF THE STUDY: The results show that RBCs can be used to treat effluents containing DDAC at concentrations up to 20 mg l(-1) and that 160 mg l(-1) of DDAC was required to eliminate cells in established biofilms.

Animals↗

PubMed1988

The plant cell/microbe coincubation assay for the analysis of plant-activated promutagens.

The preincubation and suspension procedures of the plant cell/microbe coincubation assay are described and the activation of 2-aminofluorene and m-phenylenediamine by cultured tobacco, cotton, carrot and maize cells is compared. The assay measures the plant activation of promutagens into genotoxins detected in Salmonella typhimurium as well as toxicity in plant and microbial cells. At concentrations of 2-aminofluorene 0-0.5 mumoles/reaction tube, the rank order of the efficiency of activation by plant cells was tobacco much greater than cotton greater than carrot. Cultured maize cells did not activate 2-aminofluorene. The tobacco cell activation of 2-aminofluorene was inhibited 50% by 750 microM diethyldithiocarbamate under conditions that did not affect the cell viability. Tobacco cells were also the most efficient plant cells in activating m-phenylenediamine (0-5 mumoles/reaction tube). The 'biological affinity' of m-phenylenediamine for the activation system in tobacco cells was approximately 100 microM.

Biotransformation↗

PubMed2002

New approaches towards the identification of antibiotic and vaccine targets in Streptococcus pneumoniae.

Streptococcus pneumoniae causes more than one million deaths every year, mostly of young children in developing countries, due to pneumonia, bacteremia and meningitis. The emergence and dissemination of drug-resistant pneumococcal strains, coupled to changing patterns of virulence and the inadequacy of available vaccines, calls for an aggressive search for novel targets for antibiotic and vaccine development. Microbial genomics techniques allow genetic and biochemical tools to be employed to tackle discovery, design and development of new anti-infective agents based on the identification of hundreds of new targets. In this review, novel approaches employed to identify potential antibiotic and vaccine targets in S. pneumoniae are highlighted. Recently identified virulence factors, as well as molecules essential for bacterial viability, cell wall integrity and infectivity, are discussed.

Anti-Bacterial Agents↗

PubMed1996

Cost and quality considerations in antibiotic formulary management.

Numerous factors are considered in the design of an antibiotic formulary, consisting primarily of indicators of clinical efficacy and safety, as well as economic viability. Similarly, there are many potential strategies for subsequent antibiotic formulary management ranging from global educational efforts to comprehensive required antibiotic justification programs. Antibiotic formulary management programs should be tailored to individual institutions and utilize a multidisciplinary approach where possible. The primary outcome goals of such programs are generally controlled antibiotic costs, optimized clinical efficacy, minimization of adverse events, and reduced microbial resistance development, although quantification of program impact on these parameters continues to be a challenge.

Anti-Bacterial Agents↗

PubMed1999

Superiority of 11,12 carbonate macrolide antibiotics as inhibitors of translation and 50S ribosomal subunit formation in Staphylococcus aureus cells.

Three pairs of related macrolide antibiotics, differing at the 11,12 position of the macrolactone ring, were compared for effects on growth rate, cell viability, protein synthesis, and 50S ribosomal subunit formation in Staphylococcus aureus cells. For each parameter measured, the 11,12 carbonate-derivatized compound was more inhibitory compared with the corresponding 11,12-hydroxy antibiotic. Substitution at the 3-position of the ring was also important in the relative inhibition observed. The degree of inhibition found in two different growth media was proportional to the generation time of the cells. Inhibition of both protein synthesis and 50S subunit formation by each drug correlated well with the inhibition of cell viability. The results indicate that closure of the 11,12-hydroxyl groups in macrolide antibiotics with a carbonate substitution generates a more effective antimicrobial agent.

Anti-Bacterial Agents↗

PubMed1988

Protein microinjection by protease permeabilization of fibroblasts.

Exposure of cultured diploid fibroblasts to protease solutions induces a hyperpermeable state which permits entry of exogenous macromolecules directly into the cytosol. We have exploited this finding to devise a microinjection method whose chief advantages are simplicity and good retention of cell viability. Proteins successfully injected by this technique range from insulin to thyroglobulin. The amounts injected range from 4 X 10(5) to 5 X 10(6) molecules/cell.

Cell Membrane Permeability↗

PubMed2006

Influence of harvest date and geographical location on kernel symptoms, fungal infestation and embryo viability of malting barley.

This study focused on the influence of harvest timing and geographical location on spring malting barley (potential malting variety) in terms of fungal infestation and seedling viability in symptomatic and asymptomatic kernels. The study was conducted over two consecutive crop years (2003-2004) at four locations in Slovakia. The following categories of the barley kernels were used for the assessment: kernels with black point symptoms (BPK), kernels with black cover on their surface (BCK), pink-colored kernels (PCK) and asymptomatic kernels (AK). The occurrence of various fungi was detected in all kernel categories ranging from 60 to 100%. The most frequent fungal contaminants were members of the genus Alternaria, recovered from BPK in the range of 52.6-69.85%, BCK (62.36-73.28%) and AK (55.35-69.58%). The prevalence of Alternaria spp. was recorded for each harvest time. Other dematiaceous fungi, Epicoccum nigrum and Cochliobolus sativus were found with medium frequency in the same three categories. However, C. sativus was recovered with a higher frequency in BPK (2.6-25.3%). In PCK, the most commonly recovered fungi were species of Fusarium with F. avenaceum (59.2-93.2%) as the most prevalent. The infestation of kernels by fungi from other genera showed only low frequency within all the kernel categories investigated. There was no significant influence of the year and location on the proportion of the symptomatic kernel categories. Kernel germination was inhibited to a greater degree in the wetter and colder year. The strongest inhibition of germination ranging from 2.35 to 22.45% was recorded in PCK in all locations and both years. Germination declined from PCK to BCK (43.2-90.32%), and BPK (45.6-91.61%), while it was highest in AK at all harvest times (63-93.6%). This study found that the black covering symptoms (BCK) caused greater damage to viability of the kernels than black point symptoms (BPK). The delayed harvest time resulted not only in increasing numbers of discolored kernels and undesirable symptomatic kernel fractions but also in lower germination of the kernels tested.

Alternaria↗

PubMed2000

Anti-Listeria effect of enterocin A, produced by cheese-isolated Enterococcus faecium EFM01, relative to other bacteriocins from lactic acid bacteria.

Enterocin A produced by Enterococcus faecium EFM01 displayed a narrow antimicrobial spectrum, mainly directed against Listeria spp. In particular, the bacteriocin was extremely active against 13 Listeria monocytogenes strains. This high specificity of action of enterocin A for Listeria spp. relative to lactic acid bacteria, together with its broad range of activity from pH 4.0 to pH 9.0, are factors which may be of great interest with respect to the potential antilisterial use of this bacteriocin in fermented foods. Assessment of the effect of enterocin A concentration on the extent and kinetics of bactericidal activity on L. monocytogenes Lm 6 (107 cfu ml-1 in culture broth), suggested that viability losses of higher than 5 log10, and time intervals necessary for maximum loss of viability of less than 2 h, could not be obtained. Moreover, it was shown that both parameters are closely dependent on the Listeria strain used. On the other hand, at concentrations inducing destruction of approximately 2 log10 cycles, maximum loss of viability was achieved within time intervals which varied widely from one lactic acid bacteria bacteriocin to another.

Bacteriocins↗

PubMed1998

FtsK is an essential cell division protein that is localized to the septum and induced as part of the SOS response.

The role of ftsK in the growth of Escherichia coli was examined by turning off its expression. This resulted in smooth filaments without constrictions, indicating that FtsK was required at an early step in septation. Consistent with this, FtsK was found to localize to the septum in 70% of the cells, indicating that it was recruited relatively early in this process. FtsK localization required the function of FtsZ and FtsA but not FtsI and FtsQ. Consistent with this, Z rings were present in FtsK-depleted filaments. Subcellular localization of FtsK confirmed that it was a membrane protein. Only the first 202 amino acids of FtsK were essential for its role in membrane localization, cell division and viability. The expression of ftsK increased as part of the SOS response, and increased expression of ftsK conferred increased resistance to DNA damage.

Bacterial Proteins↗

PubMed2002

Influence of sub-inhibitory concentrations of conventional antifungals on metabolism of Candida albicans and on its adherence to polystyrene and extracellular matrix proteins.

Five antifungal agents with different mechanisms of action were compared for their ability to affect mitochondrial dehydrogenase activity and adherence capacity of Candida albicans to polystyrene and extracellular matrix proteins. Only amphotericin B inhibited mitochondrial dehydrogenase activity when the culture medium was supplemented with galactose. 5-Fluorocytosine and terbinafine did not affect this activity, whereas itraconazole and fluconazole improved it. Furthermore, in these experimental conditions, the effect of sub-inhibitory concentrations of antifungals on adherence was dependent on the tested antifungal and the adherence surface: amphotericin B inhibited adherence to polystyrene and fibrinogen, but improved adherence to extracellular matrix. For all surfaces tested, when culture medium was supplemented with galactose, fluorocytosine did not affect adherence, and itraconazole, fluconazole and terbinafine inhibited adherence. Our results also confirmed the influence of the carbohydrates: sub-minimum inhibitory concentrations (MIC) of itraconazole increased or did not modify the mitochondrial metabolism of yeasts when the culture medium was supplemented with galactose, but this antifungal always decreased mitochondrial metabolism when the culture medium was supplemented with glucose. These data indicate that antifungals used below their MIC values can have various effects. It is important to distinguish the effects of antifungals on the metabolism of C. albicans from effects on its adherence capacity. The former effects are linked to the viability of the yeast and the latter depends on the colonization of cellular as opposed to inert surfaces.

Amphotericin B↗

PubMed1995

Anti-Candida activity of a novel killer toxin from the yeast Williopsis mrakii.

A screening of putative killer yeast strains showed that spore-forming ascomycetous yeasts of the genera Pichia and Williopsis displayed the broadest range of activity against sensitive strains of Candida spp. and Saccharomyces cerevisiae. Williopsis mrakii (NCYC 500) showed extensive anti-Candida activity against strains isolated from clinical specimens. W. mrakii killer factor was produced in minimal media as a function of growth and its activity reached constant levels as cells entered stationary phase. The proteinaceous killer toxin was found to be unstable without a specific range of temperature and pH (above 30 degrees C and pH 4.0), and further analysis showed that the active toxin molecule was an acidic polypeptide with a relative molecular mass between 1.8-5.0 kDa. At critical concentrations the killer factor exerted a greater effect on stationary phase cells of Candida than cells from an exponential phase of growth. At low concentrations, the killer toxin produced a fungistatic effect on sensitive yeasts but at higher concentrations there was evidence to suggest that membrane damage accounted for the zymocidal effects of the killer factor. the cidal nature of the toxin was reflected in a rapid decrease in sensitive cell viability. Findings presented suggest that W. mrakii killer toxin has potential as a novel antimycotic agent in combatting medically important strains of Candida.

Antifungal Agents↗

PubMed1996

Growth and viability of Alcaligenes eutrophus JMP134 in seawater as affected by substrate and nutrient amendment.

Growth and viability of Alcaligenes eutrophus JMP134 was studied in laboratory microcosms with 0.2 microns-filtered seawater prior to release in field-based mesocosms. In unamended systems JMP134 did not grow and viability, measured as direct viable counts combined with immunofluorescence microscopy, was 40-50%. Addition of a nitrogen + phosphorus nutrient mixture caused a greater growth response than amendment with a carbon substrate. Amendment with substrate and/or nutrients caused an increase in viability to ca 100% but only for a brief period coinciding with cell proliferation. Hence, Alc. eutrophus JMP134 has a limited survival potential in seawater unless it is supplied with additional nutrients.

Alcaligenes↗

PubMed2003

Acanthamoeba polyphaga strain age and method of cyst production influence the observed efficacy of therapeutic agents and contact lens disinfectants.

The effects of age in culture and the type of medium used for induction of Acanthamoeba polyphaga (Ros) cysts on susceptibilities to polyhexamethylene biguanide (PHMB; 3 micro g/ml), chlorhexidine digluconate (30 micro g/ml), myristamidopropyl dimethylamine (20 micro g/ml), H(2)O(2) (3%), and two multipurpose contact lens solutions (MPS-1 and MPS-2, based on 1 micro g of PHMB per ml) were examined. Strain Ros-02 was cryopreserved on isolation in 1991, while strain Ros-91 had been in continuous axenic culture. Significant differences in susceptibilities to the disinfectants were found depending on the medium used for cyst preparation and the age of the test strain, with Ros-02 generally being more resistant. For example, the killing of Ros-91 cysts produced from an axenic culture of trophozoites in the presence of 50 mM MgCl(2) by MPS-2 was 4 logs, but the killing of Ros-02 by MPS-2 was only 2 logs (P < 0.05) and killing of both strains with cysts obtained from monoxenic cultures with Escherichia coli was only 1 log (P < 0.001). Assays repeated with different batches of the various cyst types gave consistent results. A batch of Ros-91 cysts stored at 4 degrees C and tested over an 8-week period with MPS-1 showed progressively increasing susceptibility to disinfection, although there was no loss of viability during storage (P < 0.01). These observations have important implications for the standardization and interpretation of Acanthamoeba disinfectant and therapeutic agent testing.

Acanthamoeba↗

PubMed1981

Variation in isoniazid susceptibility of Mycobacterium avium during the cell cycle.

A strain Mycobacterium avium that had limited susceptibility to isonicotinic acid hydrazide (INH) at 5 micrograms/ml of medium was tested for its susceptibility under cell cycle conditions. The INH-susceptible cells of M. avium were prevented from elongating if INH was present in the medium and, although there was an initial lag of 15 to 20 h, INH was bactericidal for the susceptible cells. Resurgence of viability in the INH-treated cultures was due to multiplication of INH-resistant cells. Ethidium bromide, if present in the INH-treated cultures, prevented multiplication of the INH-resistant cells.

Cell Cycle↗