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Biomedical subjects

J D Williams

Publications and source records attributed to J D Williams.

At least 325 records · Page 18Linked to original sources
PubMed1984

The activity of vancomycin and teicoplanin alone and in combination with gentamicin or ampicillin against Streptococcus faecalis.

The in vitro activities of vancomycin and teicoplanin against 56 strains of Streptococcus faecalis were compared. Killing curves showed that vancomycin and teicoplanin were bacteriostatic and that synergy was achieved when each was combined with gentamicin. The bactericidal activity displayed by 4 mg/l of ampicillin against Streptococcus faecalis was antagonized by 4 mg/l of vancomycin and 0.5 mg/l of teicoplanin respectively.

Ampicillin↗
PubMed1984

Cephalosporin-resistance in the Bacteroides fragilis group and the effect of clavulanic acid.

Thirty-five beta-lactam-resistant isolates of the Bacteroides fragilis group were examined for the susceptibility to eight cephalosporins, alone, and in combination with a subinhibitory concentration of the beta-lactamase inhibitor, clavulanic acid. The majority of strains tested became fully susceptible to cephaloridine, cefotaxime and ceftriaxone in the presence of clavulinic acid whereas the effect of the inhibitor on the susceptibility to compounds such as cefsulodin and ceftazidime and to a lesser extent cefoperazone varied according to species. Bact. fragilis strains almost invariably showed substantial reductions in MICs whereas those of other species, especially Bact. thetaiotaomicron, were influenced to a lesser extent. Susceptibility to cefoxitin was unaffected by the inhibitor but a few strains with high level resistance to latamoxef (moxalactam) became susceptible in the presence of clavulanic acid. All strains were found to produce beta-lactamase as determined by the nitrocefin test and these were characterized by isoelectric focusing.

Bacteroides fragilis↗
PubMed1984

Frequency of appearance of resistant variants to norfloxacin and nalidixic acid.

The clinical use of nalidixic acid has been hampered by the rapid appearance of resistant variants. This study compares the frequency of appearance of resistant variants to nalidixic acid and norfloxacin, a new quinolone-carboxylic acid with superior antimicrobial activity. We found a lower frequency of appearance of resistant variants with norfloxacin, although there was some cross-resistance between the two drugs. A gradation in this frequency was also noted between the species of Gram-negative rods tested, so that larger numbers of resistant variants appeared with the non-fermenters.

Anti-Infective Agents, Urinary↗
PubMed1984

National survey of antibiotic resistance in Pseudomonas aeruginosa.

The antibiotic susceptibility of 1866 consecutive non-replicate clinical isolates of Pseudomonas aeruginosa from 24 British hospitals was examined. Antibiotics tested and resistance breakpoints selected were: carbenicillin (MIC greater than 128 mg/l), azlocillin (greater than 32 mg/l), cefotaxime (greater than 16 mg/l), cefoperazone (greater than 16 mg/l), ceftazidime (greater than 16 mg/l), amikacin (greater than 4 mg/l) and gentamicin (greater than 2 mg/l). Resistance frequencies detected were: carbenicillin 9.6%, azlocillin 3.9%, cefotaxime 19.0%, cefoperazone 4.3%, ceftazidime 0.3%, amikacin 3.8%, and gentamicin 5.5%.

Anti-Bacterial Agents↗
PubMed1984

The effect of clavulanic acid on the susceptibility of Bacteroides fragilis to three acyl-ureidopenicillins, ampicillin and carbenicillin.

The susceptibilities of 50 clinical isolates of the Bacteroides fragilis group to ampicillin, carbenicillin, mezlocillin, azlocillin and piperacillin were similar, modal MICs being 8-32 mg/l. However, in the presence of clavulanic acid, 45 and 43 strains became susceptible (MIC less than or equal to 4 mg/l) to ampicillin and carbenicillin respectively whilst 27, 37 and 35 strains became susceptible (MIC less than or equal to 4 mg/l) to mezlocillin, azlocillin and piperacillin. Clavulanic acid did not influence the susceptibility of six (12%) strains. The isoelectric points of the beta-lactamases from Bact. fragilis and Bact. thetaiotaomicron were similar to those found by others.

Ampicillin↗
PubMed1984

Mechanisms of beta-lactam resistance in British isolates of Pseudomonas aeruginosa.

The mechanisms of resistance to beta-lactam antibiotics in 191 isolates of Pseudomonas aeruginosa were examined. These represented the most resistant organisms of 1866 isolates collected during a national survey of antibiotic resistance in this species. One hundred and seventy-two isolates were selected because they were resistant to carbenicillin (MIC greater than 128 mg/L) and 19 because the MICs of cefotaxime were greater than the MICs of carbenicillin. Of the carbenicillin-resistant isolates, 35 produced plasmid-mediated beta-lactamases known to be active against carbenicillin and seven produced unusual beta-lactamases; in 131 strains, resistance could not be attributed to beta-lactamase production and was considered to be intrinsic. The unusual antibiogram in which the MIC of cefotaxime was greater than the MIC of carbenicillin was associated with overproduction of the chromosomally-determined Sabath and Abrahams ' beta-lactamase. Selection of strains with this last mechanism represents a novel resistance problem and one which may increase with increased use of newer antipseudomonal beta-lactams.

Anti-Bacterial Agents↗
PubMed1984

Detection of PSE-2 beta-lactamase in enterobacteria.

PSE-2, a plasmid-mediated beta-lactamase which was previously considered pseudomonas specific, was observed in clinical isolates of Escherichia coli, Klebsiella pneumoniae, Providencia stuartii, and Enterobacter cloacae. All four isolates transferred PSE-2 production, together with resistance to gentamicin, tobramycin, kanamycin, and sulfamethoxazole, into Escherichia coli J62-1 and Pseudomonas aeruginosa PU21. Transfer correlated with acquisition by the transconjugants of a 65-megadalton plasmid, and this element was considered to encode PSE-2 expression. The PSE-2 enzyme conferred high-level carbenicillin resistance on both J62-1 and PU21 transconjugants, although the PSE-2-producing Providencia stuartii isolate was susceptible to carbenicillin.

Conjugation, Genetic↗
PubMed1984

Characteristics of the phagocytically induced respiratory burst in leukocytes from young adult and aged beagle dogs.

Phagocytically stimulated canine leukocyte suspensions obtained from 12 young adult and 43 aged individuals were examined for several physiological manifestations of the phagocytically induced respiratory burst. There was considerable variation in levels of oxygen consumption, glucose oxidation via the hexose monophosphate shunt (HMPS), and chemiluminescence response by both resting and phagocytically stimulated leukocytes from different individual animals in each age-group. Leukocyte suspensions from specific individuals in each age-group exhibited a weakly responsive respiratory burst. Chronological age could not be used as a predictor of either the specific (oxygen consumption and HMPS activity) or nonspecific (chemiluminescence response) manifestations of the respiratory burst. The kinetics of the chemiluminescence response were similar for all age-groups. Collectively, the results suggest that there is not an age-related alteration in the phagocytically induced respiratory burst of canine neutrophils and that cells from young adult and aged dogs have a comparable capacity to generate levels of highly reactive antimicrobial oxidizing agents. The increased relative susceptibility of aging dogs to microbial agents is apparently not related to an absent, abbreviated, or reduced leukocyte respiratory burst.

Aging↗
PubMed1984

Release of leukotrienes by human monocytes on stimulation of their phagocytic receptor for particulate activators.

The respective capacities of adherent human monocytes to metabolize endogenous arachidonic acid into leukotrienes C4 (LTC4) and B4 (LTB4) in response to activation with an ionophore, A23187, or to phagocytosis of unopsonized zymosan particles and IgG-sensitized sheep erythrocytes ( EsIgG ) were compared under optimal conditions for each stimulus. Resolution of the cellfree supernatant, after ionophore activation, by reverse-phase high performance liquid chromatography (RP-HPLC) identified only two products which eluted at the retention times of LTC4 and LTB4. There was correspondence between their quantitation by integrated optical density and radioimmunoassay, and the recoveries from the initial supernatant were 80% by radioimmunoassay. Activation of adherent monocytes from 12 donors by ionophore and by zymosan particles released 68.1 ng and 10.0 ng LTB4 and 29.5 ng and 2.1 ng LTC4, respectively. With trypsin pretreatment, the monocytes responded fully to ionophore activation but were inhibited in their response to zymosan particles as assessed by phagocytosis and leukotriene release, indicating that the zymosan stimulus acted through a trypsin-sensitive membrane receptor. When the response of adherent monocytes from nine donors to zymosan particles and to EsIgG were compared at identical particle concentrations and with similar numbers of ingesting monocytes, zymosan elicited LTB4 release (mean 6.7 ng) from all and LTC4 (mean 1.5 ng) from eight donors, while EsIgG caused low level release of LTB4 (mean 0.7 ng) from six and LTC4 from only one of the donors. Neither zymosan nor ionophore stimulation led to the metabolism of exogenously added [3H]LTB4 or [3H]LTC4 as assessed by RP-HPLC of the cellfree supernatants and by quantitation of the eluted labeled products. Thus, transmembrane activation of adherent monocytes by their receptor for particulate activators, in contrast to stimulation of their IgG-Fc receptor, reproducibly releases substantial quantities of LTB4 and LTC4, and may represent an important mechanism for regulating the microenvironment in the nonimmune host.

Arachidonic Acid↗
PubMed1984

Activation of the alternative complement pathway by isolated human glomerular basement membrane.

The capacity of isolated human glomerular basement membrane (GBM) to initiate surface activation of the human alternative complement pathway was defined by the deposition of C3b under circumstances in which the classical complement pathway was inoperative. The deposition of C3b from normal or C2-deficient serum was time- and magnesium-dependent, implying a role for the alternative pathway. Normal human serum rendered deficient in D did not sustain C3b deposition until its reconstitution with D, indicating an absolute requirement for a protein unique to the alternative pathway and essential to the cleavage activation of the C3 amplification convertase of that pathway. The capacity of the excess control proteins H and I to prevent C3b deposition onto GBM incubated in C2-deficient serum provided further evidence for the direct activation of the alternative pathway in this system. The use of radiolabeled monoclonal antibody to localize the deposited C3b afforded specificity and quantitation of about 100 ng of C3b/mg of GBM. Immunohistochemical analysis with a monoclonal antibody to detect C3b demonstrated its deposition to be confined to the epithelial surface of the GBM.

Antibodies, Monoclonal↗
PubMed1983

Cefotetan activity against Gram-negative aerobes and anaerobes.

The activity of cefotetan has been determined against strains of bacteroides, Haemophilus influenzae and klebsiella. The activity against bacteroides was lower than that of cefoxitin and moxalactam. The activity against multi-resistant klebsiella was very high, most strains requiring a concentration of 0.06 mg/l for inhibition. The stability to various beta-lactamases was demonstrated by testing the compound against beta-lactamase-producing H. influenzae and Enterobacteriaceae.

Anaerobiosis↗
PubMed1983

The killing effects of cefathiamidine or ampicillin alone and in combination with gentamicin against enterococci.

The in-vitro activity of cefathiamidine against Streptococcus faecalis and Str. faecium were studied in comparison with other beta-lactams. All the 56 strains of Str. faecalis tested were inhibited by 2 mg/l of cefathiamidine. MICs of ampicillin were twofold higher than those of cefathiamidine and MICs of cephaloridine and cephazolin were 8-16-fold higher. No significant inoculum effect on MICs of cefathiamidine could be seen. Two isolates of Str. faecium showed resistance to the four antibiotics. The MBCs of cefathiamidine and ampicillin for ten strains of Str. faecalis showed that the ratios of MBC/MIC were greater than 64. The rates of killing of Str. faecalis were reduced at concentrations of cefathiamidine and ampicillin greater than the MIC. The most rapid killing was obtained at 2 mg/l cefathiamidine or 4 mg/l of ampicillin. With the addition of 1 mg/l gentamicin this paradoxical bacteriocidal effect was eliminated. Time killing studies showed 99.9% of the cells were killed within 6 h by a combination of aminoglycoside and beta-lactam. The paradoxical bacteriocidal effect of cefathiamidine and ampicillin was also demonstrated on solid media.

Ampicillin↗
PubMed1983

Blood transfusions, suppressor T cells, and renal transplant survival.

Fifteen men undergoing chronic hemodialysis were transfused with 2 units of packed red cells, none of these patients having been previously transfused. They were studied before and after transfusion to determine suppressor T cell numbers and activity, and to monitor the appearance of cytotoxic antibodies. Although the number of suppressor T cells did not change, their function was significantly increased three weeks after the transfusion. This had largely returned to normal by 20 weeks. No cytotoxic antibodies were produced. Twelve of the patients subsequently received cadaveric renal transplants and nine of these kidneys are currently functioning more than a year after transplantation. Although the blood transfusions may have helped to produce these satisfactory results, it is accepted that the nonspecific increase in suppressor cell function may not have been the only mediator because this activity had returned to normal in most cases by the time the patients were transplanted.

Adult↗
PubMed1983

Accuracy of methods used for susceptibility testing of Haemophilus influenzae in United Kingdom laboratories.

Antibiotic susceptibility test reports on 1841 strains of Haemophilus influenzae from 25 microbiology laboratories were compared with results obtained with the same strains at The London Hospital Medical College. Of strains found to be sensitive to the antibiotics tested, 0.5% were reported as tetracycline-resistant, 1.6% as ampicillin-resistant, and 6.2% as trimethoprim-resistant. Of strains found to be resistant to these antibiotics, 37% were reported as tetracycline-sensitive, 27% as ampicillin-sensitive, and 66.7% as trimethoprim-sensitive. Factors found to be of significance in improving accuracy of sensitivity reporting included use of chromogenic cephalosporin and low-content antibiotic discs for detection of ampicillin resistance, and use of lysed blood agar rather than chocolated blood agar to detect trimethoprim sensitivity.

Ampicillin↗
PubMed1983

Pedigree analysis of four decades of Quarter Horse breeding.

Pedigrees of randomly selected Quarter Horses born in each of the years 1946, 1956, 1966 and 1976 and of winning halter, cutting and race horses born in the same years were evaluated and compared. Average inbreeding and inter se relationship levels and relationships of influential ancestors to the sample were calculated for each sample. The amount of Thoroughbred influence and the average generation interval were also determined for each random sample. The levels of inbreeding found in the random samples were low, ranging from 1.3% in 1956 to 2.6% in 1966; however, these levels were higher than would be expected if mating were random. Show and race winners born in 1976 appeared to be less inbred than random horses of the breed. The estimated average inter se relationship within the random samples increased from 0% in 1946 to 3% in 1966, decreasing again to 0% in 1976. Horses in the elite samples appeared to be more closely related to each other than those in the random samples. Fifteen ancestors of horses in the random samples were identified as influential to the Quarter Horse breed. Many of these same ancestors were influential in the halter and cutting samples, but only one was influential in the race samples. The percentage of pedigree lines in the random samples that contained a Thoroughbred ancestor were as follows; 1946, 27.5%; 1956, 19.2%; 1966, 23.2% and 1976, 31.4%. The average generation interval fluctuated from approximately 8 yr to approximately 10 yr for the random samples.

Animals↗