Biomedical subjects

D B Drucker

Publications and source records attributed to D B Drucker.

At least 73 records · Page 4Linked to original sources

PubMed1993

Polar lipids of strains of Prevotella, Bacteroides and Capnocytophaga analysed by fast atom bombardment mass spectrometry.

The polar lipid composition of representative strains of Bacteroides fragilis, Prevotella intermedia, P. melaninogenica and Capnocytophaga ochracea was determined. Samples were analysed by FAB-MS. Forty major peaks had m/z values expected for known carboxylate anions, ranging from m/z 211 (tridecenoate) to m/z 381 (pentacontanoate). A further fifty-five major peaks were studied between m/z 561 and m/z 722. Forty-five anionic phospholipids of several series were identified. The Pearson coefficient of linear correlation revealed the similarity of the P. intermedia spectra from repeat experiments (r = 0.98), as opposed to inter-species comparisons (0.55, 0.22, 0.20). Thus, FAB-MS rapidly yields data on molecular species within phospholipid families not readily obtained by other means. The data obtained may have chemotaxonomic potential.

Bacteroides↗

PubMed1992

Fast atom bombardment-mass spectrometry for bacterial chemotaxonomy: influence of culture age, growth temperature, gaseous environment and extraction technique.

Extracted phospholipids of Escherichia coli, Proteus mirabilis and Enterobacter cloacae were examined by fast atom bombardment-mass spectrometry which yielded major peaks between m/z 225 and 761. The result of extracting freeze-dried or 'wet' cells showed that freeze-drying may be omitted although weighing of dried cells offers a useful means of standardizing the extraction procedure. Anaerobic growth quantitatively altered the chemical finger-print as a result of increase in ratio of saturated: unsaturated carboxylic acids. Growth temperature also affected profiles over the temperature range 24-45 degrees C. A less drastic influence on mass spectra was culture age, over the range 16-48 h. Comparison of spectra was possible with Pearson's coefficient of linear correlation which yielded the following values: wet and lyophilized cells, r = 0.97; aerobic and anaerobic growth, r = 0.82; 24 degrees C and 45 degrees C, r = 0.76; 16 h and 48 h, r = 0.95. These results show that although quantitative differences do occur between spectra for the same organism prepared in different ways, they are less than interspecies variation, e.g. with E. coli and P. mirabilis, r = 0.46. Any differences which are due preparation method can be overcome by standardization of technique.

Aerobiosis↗

PubMed1992

Analysis of polar lipids from some representative enterobacteria, Plesiomonas and Acinetobacter by fast atom bombardment-mass spectrometry.

Fast atom bombardment-mass spectrometry (FAB-MS) was used to analyse lipid extracts of bacteria to assess its usefulness for analysing anionic phospholipids of potential chemotaxonomic value. The following micro-organisms were tested: Acinetobacter calcoaceticus, Acinetobacter sp., Citrobacter freundii, Enterobacter cloacae (2 strains), Escherichia coli (3 strains), Hafnia alvei, Klebsiella oxytoca, Klebsiella pneumoniae, Morganella morganii, Plesiomonas shigelloides, Proteus mirabilis (3 strains), Serratia liquefaciens and Serratia marcescens. Negative-ion spectra provide data for twenty-seven major carboxylate anions (m/z 209-325) and for thirty-seven major phospholipid anions (m/z 645-774). Generally, the largest carboxylate peaks were due to 16:1, 16:0, cyc17 and 18:1 while the largest phospholipid anion peaks were due to PE(32:1), PE(33:1), PE(34:1), PE(34:2), PG(30:2), PG(31:2), PG(32:2), PG(34:1) and PS(33:0). However, quantitative differences were observed. For example, Acinetobacter lacked PE (33:1) but had exceptionally high peaks at m/z 748, PS(33:0), and m/z 281, octadecanoate. Unknown 'carboxylate' peaks were detected at m/z 254, 256, 261, 268, 282 and 301. In some cases, unknown peaks appeared to constitute possible homologous series being separated by delta m/z of 14(identical to methylene). For chemotaxonomic purposes, the complexity of the data required numerical analysis. Using the Pearson coefficient of linear correlation, as a measure of association, it was possible to compare all strains analysed. Typical results for strain comparisons were as follows: Ent. cloacae vs Ent. cloacae, r = 0.90 (Ent. cloacae vs Ac. calcoaceticus, r = 0.46). Thus FAB-MS represents an excellent means of obtaining large quantities of data on polar lipids of a range of bacterial isolates, which may be suitable for chemotaxonomic purposes.

Acinetobacter↗

PubMed1992

Bacterial toxins: a possible cause of cot death.

AIM: To test the hypothesis that sudden infant death syndrome (SIDS) may be caused by toxins of commonly occurring bacteria in infants lacking developed immunity. METHODS: Nasopharyngeal microbial isolates from 22 pairs of SIDS cases and healthy infants matched for age (by month), sex, and sampling time (by month) were compared for lethal toxigenicity. Crude toxin preparations were made from isolates cultured on dialysis membrane overlaid on agar, and these preparations were then tested for lethality by intravenous injection into 11 day old chick embryos. RESULTS: Fifteen (68%) of the SIDS cases were each found to have at least one lethally toxigenic organism in their nasopharyngeal flora; only eight (36%) of the flora of normal infants included a lethally toxigenic species. CONCLUSION: Infants who have died of SIDS have a significantly higher (p less than 0.05) probability than matched healthy infants of having a lethally toxigenic bacterial species in their nasopharyngeal flora.

Bacteria↗

PubMed1992

Evaluation of Mast-ID 15 system for identification of fresh clinical isolates of Enterobacteriaceae and Acinetobacter.

AIMS: To assess the accuracy of the Mast-ID 15 system compared with API 20 E for the identification of stock and fresh clinical strains of Enterobacteriaceae and Acinetobacter spp; to compare the accuracy of 19 pin and 36 pin multipoint inoculator heads. METHODS: One hundred frozen stock cultures of Enterobacteriaceae and Acinetobacter spp which had previously been identified by the API 20E were classified by the Mast-ID using 19 and 36 pin multipoint inoculator heads. Reproducibility was determined by testing 36 randomly selected organisms in duplicate. Four hundred and sixty nine consecutive fresh clinical isolates of Enterobacteriaceae and Acinetobacter spp were identified by the Mast-ID using a 36 pin multipoint inoculator and by the API 20E. Reproducibility for the fresh isolates was determined by testing 96 randomly selected strains in duplicate. RESULTS: The Mast-ID 15 identified 82% and 85% of frozen strains to species level and reproducibility was 80% and 86% using 19 and 36 pin inoculator heads, respectively. Of the 469 fresh clinical isolates, the Mast-ID identified 70% of strains to species level; 19% were not identified and 11% were identified incorrectly by comparison with the API 20E. The Mast-ID achieved a reproducibility level of 80% with the fresh clinical isolates. CONCLUSIONS: The use of a 36 pin multipoint inoculator head in preference to the standard 19 pin head for the Mast-ID was advantageous as it allowed greater numbers of strains to be identified at a reduced cost. Unfortunately, in our hands, the Mast-ID system was insufficiently accurate for routine use in the clinical laboratory. Modifications to some of the problematic tests may result in a sufficient increase in accuracy and reproducibility to make the system beneficial in the routine clinical laboratory.

Acinetobacter↗

PubMed1992

Lethal synergistic action of toxins of bacteria isolated from sudden infant death syndrome.

AIM: To test the hypothesis that lethal toxins of bacteria associated with sudden infant death syndrome (SIDS) can act synergistically. METHODS: Bacteria occurring together in the nasopharynx of cases of cot death were studied. The lethal toxicity of crude toxin preparations was determined over a range of dilutions by injections into the chorioallantoic vein of the chick embryo. Toxin preparations of low lethality for the chick embryo SIDS model were then tested in combination. RESULTS: Staphylococcus aureus toxin preparations showed low lethality when tested alone, even at low dilution. At 1 in 100 dilution S aureus toxin was lethal to one out of 15 chick embryos. Escherichia coli toxin preparations showed high lethality except on high dilution (1 in 80) when lethality fell to two out of 15 of chick embryos. When the same toxin preparations were tested simultaneously in combination, lethality rose to 14 out of 15. Similar findings were observed over a range of toxin dilutions. This finding was highly significant (p = 0.0012). CONCLUSIONS: That synergy between toxins can enhance the lethality of toxins elaborated by bacteria associated with SIDS.

Animals↗

PubMed1992

Possibility of separating toxins from bacteria associated with sudden infant death syndrome using anion exchange chromatography.

AIMS: To develop techniques for the characterisation of toxins elaborated by a strain of Escherichia coli associated with sudden infant death syndrome (SIDS). METHODS: E coli SIDS 04, isolated from the nasopharynx of a case of SIDS, was studied. Cell-free toxin preparations were standardised, their protein measured, and analytical separation of proteins achieved using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Acetone precipitation of proteins was required prior to Coomassie blue staining of bands. Preparative separation was achieved on an anion exchange column using a programmed concentration gradient of NaCl in TRIS buffer. Fractions were tested individually or pooled for presence of lethal toxin including endotoxin. Lethal toxin was detected with the chick embryo test system. Endotoxin was measured using a chromogenic modification of the Limulus amoebocyte assay. RESULTS: Twenty one peaks were detected by chromatography. Ten individual, or pooled, fractions were assayed for endotoxin which ranged from 27-33 pg/ml. Much greater variation was found when the same fractions were assayed in chick embryos. E coli fractions varied considerably in lethal toxicity, from 0/10 to 10/10 chick embryos killed/tested. Certain E coli fractions tested individually (lethality four out of 10 to eight out of 10) proved more lethal (10 out of 10) if pooled prior to testing. CONCLUSIONS: In E coli infection associated with SIDS relatively low concentrations of extracellular protein are lethally toxigenic for the chick embryo model of SIDS. These proteins can be separated analytically by SDS-PAGE and preparatively by anion exchange chromatography. Toxicity of individual fractions is not correlated with endotoxin concentrations in samples tested.

Animals↗

PubMed1992

Susceptibility of sixty-five non-oral clinical isolates of the Streptococcus milleri group to seven antimicrobial agents.

Antimicrobial susceptibilities of sixty-five non-oral Streptococcus milleri group clinical isolates to penicillin, gentamicin, lincomycin, ampicillin, chloramphenicol, tetracycline and erythromycin were determined by an agar dilution method. All strains were penicillin-sensitive (MIC < or = 0.031 microgram/ml) and the majority (64/65) were susceptible to erythromycin (MIC < or = 0.125 microgram/ml). Low-level resistance to gentamicin was observed, and the majority of strains possessed an MIC of 8 micrograms/ml. Lincomycin and ampicillin at 0.5 microgram/ml inhibited 52/65 and 61/65 strains, respectively. Of the isolates 92% were inhibited by chloramphenicol at < or = 2 micrograms/ml. Twenty-two S. milleri group strains (of which thirteen were vaginal isolates) were resistant to tetracycline (MIC > or = 8 micrograms/ml).

Anti-Bacterial Agents↗

PubMed1992

The endodontic microflora revisited.

The microbial flora of 35 dental root canals were examined, taking care to maintain the viability of obligate anaerobes which accounted for 45% of total isolations, while streptococcal species accounted for 24% of the total species isolated. Individual root canals yielded a maximum of eight bacterial species. A total of 40 different species was isolated of which the most prevalent were the facultative anaerobe Streptococcus sanguis and the obligate anaerobe, Peptostreptococcus micros (both in 23% of root canals), followed by Eubacterium aerofaciens and the 'Streptococcus milleri group' (both 17%) then Prevotella melaninogenica (formerly Bacteroides melaninogenicus), Enterococcus faecalis and Prevotella oralis (formerly Bacteroides oralis), which were each isolated from 14% of root canals. Highly significant associations were discovered between four pairs of species, viz P. melaninogenica with P. micros, P. melaninogenica with P. oralis, Prevotella corporis with Streptococcus morbillorum and Actinomyces odontolyticus with E. faecalis.

Dental Pulp Cavity↗

PubMed1992

Numerical taxonomy of Bacteroides and other genera of Gram-negative anaerobic rods.

A numerical taxonomy was performed on 157 cultures (141 different strains) of species of Bacteroides, Polyphyromonas, Prevotella [not Prevotella (Labroue, 1976)] and Fusobacterium. Isolates were each tested for 111 phenotypic characters which included possession of constitutive enzymes, fermentation of specific carbohydrates, gas chromatographic analysis of metabolic end-products and of cellular carboxylic acid composition. Computation of similarity coefficients was followed by a single-linkage cluster analysis. At the 94% similarity level, the following groupings at genus level were apparent: (1) Bacteroides ureolyticus; (2) Fusobacterium mortiferum, F. necrogenes, F. necrophorum, F. nucleatum and F. varium; (3) B. caccae, B. distasonis, B. eggerthii, B. fragilis, B. merdae, B. ovatus, B stercoris, B. thetaiotaomicron, B. uniformus and B. vulgatus; (4) B. splanchnicus; (5) Porphyromonas asaccharolytica; (6) B. bivius (Prevotella bivia); (7) B. disiens (P. disiens); (8) B. intermedius (P. intermedia);and (9) B. melaninogenicus (P. melaninogenica). Single isolates of B. ruminicola (P. ruminicola), B. denticola (P. denticola) and B. capillosus did not cluster with other strains.

Bacterial Typing Techniques↗

PubMed1991

An examination of strains of the bacterium Streptococcus vestibularis for relative cariogenicity in gnotobiotic rats and adhesion in vitro.

The cariogenicity and adhesion of six strains of Streptococcus vestibularis were compared with those of strains of Strep. salivarius. All strains of Strep. vestibularis produced low levels of caries, confined to the fissures, whereas the two strains of Strep. salivarius produced high levels of caries, with one strain producing approximal as well as fissure caries. The values for adhesion to saliva-coated hydroxyapatite of Strep. vestibularis in the absence (median 4.74%) and the presence (median 4.67%) of sucrose were not statistically different, nor did they differ significantly from those of Strep. salivarius. Strains of Strep. vestibularis were able to adhere to buccal epithelial cells (median 1.19%) as well as could Strep. salivarius strain HB (1.65%). Neither sucrose nor saliva greatly aggregated the strains of either species. Strep. vestibularis did not adhere to hexadecane (median 18.5%) to the same extent as did Strep. salivarius strains (median 69%). There was a significant correlation between the adhesion in the presence and absence of sucrose (p less than 0.01). Strep. vestibularis strains could not coaggregate with either actinomycetes or Veillonella spp. whereas Strep. salivarius strains were able to coaggregate with Veillonella spp.

Actinomyces↗

PubMed1991

Identification, and susceptibility to seven antimicrobial agents, of 61 gram-negative anaerobic rods from periodontal pockets.

Sixty-one cultures of Gram-negative anaerobic rods were isolated from deep periodontal pockets of patients with rapidly progressive periodontitis. Isolates were speciated as Bacteroides gingivalis (18 isolates), Bacteroides intermedius (8), Bacteroides oris (1), Bacteroides gracilis (17) and Fusobacterium nucleatum (17). Their susceptibilities, to seven antimicrobial agents, were determined in vitro using a plate dilution technique. Amoxycillin and amoxycillin with clavulanic acid were active against all isolates (MIC less than 1 mg/l) and proved the most effective agents tested. F. nucleatum and B. gracilis showed resistance to erythromycin; F. nucleatum had MIC values ranging from 0.03 mg/l up to 128 mg/l when tested with this, least effective agent. Metronidazole was effective against all isolates except for a few strains of B. gracilis (MIC less than 4 mg/l). Tetracycline hydrochloride and minocycline were active against all isolates except for a few strains of B. gracilis (MIC less than 2 mg/l with both minocycline and tetracycline hydrochloride). Penicillin proved less effective than amoxycillin with regard to inhibition of B. gracilis.

Amoxicillin↗

PubMed1991

Evaluation of acrylic strips containing amoxycillin with clavulanic acid for local drug delivery.

The in vitro release of amoxycillin with clavulanic acid from acrylic strips at initial concentrations of 30, 40 and 50 per cent w/w was monitored using a double-beam ultraviolet spectrophotometer and compared with release of tetracycline hydrochloride. Highest levels of the antibacterial agents were released during the first 24 h period. Therapeutic levels of the drugs continued to be released during the subsequent 9 day period and were shown to be biologically active. Furthermore, for amoxycillin with clavulanic acid, an initial concentration of 40 per cent gave the highest level of release on day 10; while, for tetracycline, 50 per cent provided the highest level of release. Local application of 40 per cent amoxycillin with clavulanic acid incorporated into acrylic strips placed in periodontal pockets in patients with established periodontitis produced a marked change in the subgingival microflora as monitored by dark-field microscopy and cultural techniques. These changes in the subgingival flora were concomitant with elimination of bleeding on probing at the treated sites and were still evident 3 weeks after removal of the acrylic strips. The sensitivity of Bacteroides gingivalis (syn. Porphyromonas gingivalis) and Bacteroides intermedius (syn. Prevotella intermedia) isolated before and after treatment to amoxycillin with clavulanic acid remained unchanged.

Acrylic Resins↗

PubMed1991

Amoxycillin with clavulanic acid and tetracycline in periodontal therapy.

The effects of tetracycline and amoxycillin with clavulanic acid on the clinical parameters and subgingival flora of eight patients with rapidly progressive periodontitis was assessed. Subjects received either tetracycline 250 mg four times daily or amoxycillin 250 mg with clavulanic acid 125 mg three times daily for a period of 2 weeks together with subgingival scaling and root planning. Both treatment regimens produced significant reductions in bleeding on probing and probing pocket depths which were still present 16 weeks after the antibiotic therapy. A significant reduction in the mean percentage of black-pigmented Bacteroides spp., Fusobacterium nucleatum and anaerobic corroding bacilli was also obtained. Both treatment regimens were equally effective in reducing the clinical parameter and altering the subgingival flora. The MIC values for Bacteroides gingivalis (Porphyromonas gingivalis). Bacteroides intermedius (Prevotella intermedia) and F. nucleatum to amoxycillin with clavulanic acid remained constant throughout the period of investigation. The MIC values of these organisms to tetracycline increased.

Amoxicillin↗

PubMed1991

Evaluation of the RAPID ID 32A system for the identification of Bacteroides fragilis and related organisms.

This study evaluated the ability of a rapid identification system for anaerobic bacteria, ATB 32A, now renamed RAPID ID 32A (API-bioMérieux UK Ltd., Basingstoke), to identify accurately 74 strains of the 'B. fragilis group'. ATB 32A identified correctly 78.4% of strains to species level, without supplemental tests. The percentage of strains identified to species level rose to 94.6% when a supplementary test (advised by bioMérieux) for catalase production was used to differentiate between Bacteroides ovatus and Bacteroides uniformis. RAPID ID 32A is a rapid, accurate method for the identification of members of the 'B. fragilis group' isolated within a routine clinical laboratory.

Bacteroides↗

PubMed1991

Improved detection of Candida albicans in a blood-culture model.

Human blood reduced the numbers of colony-forming units (cfu) of Candida albicans in a blood-culture model so that the detection time was increased by 12 h. Reduction in cfu was accompanied not by reduction in cell mass but by observable clumping of cultures, which was attributable to a heat-stable serum component. The action of the latter component could be negated if the medium were supplemented by a combination of trypsin, 2-phenyl ethanol, liquoid and Tween 80, when a statistically significant improvement was noted in minimum detection time for C. albicans growing in blood-culture medium.

Candida albicans↗

PubMed1990

In vivo dental plaque-forming ability and cariogenicity of the bacterium Streptococcus bovis in gnotobiotic rats.

Germ-free Fisher rats, fed on a high sucrose diet, were monoinfected with Streptococcus bovis strains. High levels of fissure caries were formed by three strains; one strain produced moderate levels; another produced only very low levels. No strain could produce approximal or buccal/lingual lesions. All strains could colonize the fissures of teeth in the lower jaw, as shown by scanning electron microscopy. The most cariogenic strains were associated with caries scores similar to those of Strep. salivarius and members of the mutants streptococci.

Animals↗

PubMed1990

Cohesion between oral streptococci and Neisseria pharyngis on saliva-coated glass, in the presence and absence of sucrose.

Ten strains of oral streptococci, comprising nine species, were screened for their in vitro cohesive interactions with a freshly isolated strain of Neisseria pharyngis. Strains of mutans streptococci, Streptococcus salivarius, Streptococcus sanguis I, Streptococcus milleri and Streptococcus mitis were able to cohere with N. pharyngis cells attached to a salivary pellicle adsorbed to glass. The cohesion was either due to coaggregation between the different genera or modification of the salivary pellicle by N. pharyngis MW2. S. sanguis II and Streptococcus oralis strains could not cohere with the N. pharyngis strain. Extracellular polysaccharide formed from sucrose was found to mediate cohesion between certain strains of mutans streptococci or S. oralis and N. pharyngis MW2.

Bacterial Adhesion↗