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Biomedical subjects

D N Wright

Publications and source records attributed to D N Wright.

At least 19 recordsLinked to original sources

Serum IgE and human immunodeficiency virus (HIV) infection.

Human immunodeficiency virus infection is characterized by a progressive depletion of helper T-lymphocytes and, like allergic diseases, is associated with altered T cell regulation. Total serum IgE was measured in 67 infected male subjects, 27 uninfected heterosexual male subjects, and 18 uninfected homosexual male subjects. The mean IgE level (132 IU/ml) of infected subjects with a helper T-lymphocyte number less than or equal to 200/mm3 was significantly greater than mean IgE levels of the uninfected heterosexual (38 IU/ml) and homosexual (35 IU/ml) groups. IgE levels were inversely related to both helper T cell and suppressor/cytotoxic T cell numbers but not to IgG or IgA levels. The increase in IgE was not a reflection of an increased prevalence of atopic disease (allergic asthma, allergic rhinitis, or atopic dermatitis) in the infected subjects. The elevation of IgE may be related to a difference among the groups in T cell production of IgE regulatory lymphokines.

Acquired Immunodeficiency Syndrome

In vitro activities of cefoperazone and sulbactam singly and in combination against cefoperazone-resistant members of the family Enterobacteriaceae and nonfermenters.

Among 28,000 isolates of the family Enterobacteriaceae and nonfermenters isolated at multiple medical centers, 1,084 (4%) were resistant to cefoperazone (MIC, greater than or equal to 64 micrograms/ml) and 1,711 (6%) exhibited cefoperazone MICs of 2 to 32 micrograms/ml. Ninety-six percent of these 2,795 isolates produced beta-lactamase, as determined by the nitrocefin test. Sulbactam alone (8 micrograms/ml) was inactive against 99.6% of the isolates other than Acinetobacter calcoaceticus and Pseudomonas cepacia. Sulbactam enhanced the activity of cefoperazone against 56% of the isolates of the family Enterobacteriaceae and 44% of the nonfermenters. In the presence of sulbactam concentrations of less than or equal to 8 micrograms/ml, 65% of the cefoperazone-resistant isolates had reductions in cefoperazone MICs of greater than or equal to 2 log2 dilution steps and were susceptible to less than or equal to 32 micrograms/ml. Antagonism was not observed.

Bacteria

Evaluation of four newer antimicrobial agents in the Avantage susceptibility test system.

Antimicrobial elution disks containing amoxicillin-clavulanic acid (Augmentin), cefotetan, ciprofloxacin, or norfloxacin were tested in the Avantage automated susceptibility test system. Performance was compared against an agar diffusion procedure in a three-site collaborative study. Results of 1,500 comparison with amoxicillin-clavulanic acid showed a full accord (agreement of both systems) of 93.6% and an essential accord (agreement excluding minor discrepancies) of 97.6%. Results for cefotetan showed a full accord of 95.1% and an essential accord of 98.3% by the two methods. Results for both ciprofloxacin and norfloxacin were in full accord for more than 98% of tests with gram-negative bacilli and staphylococci, but tests with enterococci gave 38 and 26.1% minor discrepancies (the result of one method was resistant or susceptible and the result of the other method was intermediate), respectively. The results indicated that the Avantage test system is accurate and reliable and provides appropriate determination of bacterial susceptibility with the four antibiotics tested.

Amoxicillin

In vitro inactivation of aminoglycosides by cephalosporin antibiotics.

The in vitro inactivation of aminoglycoside antibiotics by semisynthetic penicillins complicates antibiotic assays. Due to the increasing number of new cephalosporins and use of aminoglycoside-cephalosporin combinations, we determined the in vitro stability of 28 aminoglycoside-cephalosporin combinations (gentamicin sulfate, tobramycin sulfate, netilmicin sulfate [10 micrograms/mL], and amikacin [20 micrograms/mL] in combination with cefazolin sodium, cefoxitin sodium, cefoperazone sodium, cefotaxime sodium, ceftazidime acid pentahydrate, cefsulodin sodium, or cefpiramide sodium at 100, 200, and 300 micrograms/mL). These mixtures were incubated at 37 degrees C and sampled at 0, 8, and 24 hours. Amikacin and tobramycin were most stable and netilmicin was the least stable of the aminoglycosides. Cefoxitin, ceftazidime, and cefotaxime were the least inactivating of the cephalosporins. When combined with first- and second-generation cephalosporins, aminoglycosides are relatively stable, but some laboratory precautions may be necessary when determining aminoglycoside levels in the presence of third-generation cephalosporin compounds.

Aminoglycosides

In vitro activity in deptomycin (LY-146032) compared with other antimicrobial agents against gram-positive cocci.

A comparison was made of the activity of deptomycin (LY-146032) with that of ampicillin, cephalexin, cefamandole, cephalothin, erythromycin, teicoplanin, tetracycline, and vancomycin. The minimal inhibitory concentration (MICs) for greater than or equal to 90% of 356 Gram-positive cocci, against deptomycin, were less than or equal to 2 micrograms/ml. The MICs for the other antimicrobials varied greatly depending on the compound. A slight and unexplained inoculum effect was observed for LY-146032.

Anti-Bacterial Agents

Comparison of visual and photometric Bac-T-Screen results.

The Bac-T-Screen (Marion Laboratories, Kansas City, MO) was used to screen 826 urine specimens. Of these, 85 either pigmented or clogged the Bac-T-Screen filter and could not be evaluated. Results for the remaining 741 specimens were examined both visually and photometrically by a newly developed photometric card reader. The results were then compared. Screening results for all urines containing greater than or equal to 10(5) pathogens/mL were equivalent for both methods, with sensitivity and predictive negative values of greater than 98% and greater than 99%, respectively. The predictive values of positive tests were also equivalent at 57.5% for visual and 59.6% by photometry. The overall agreement varied with the card reader value used because the photometric card-reader procedure allows the user to select desired sensitivity and specificity levels.

Bacteriological Techniques

In vitro inactivation of aminoglycosides by apalcillin.

Apalcillin, at concentrations of 75, 150, 300, and 600 micrograms/ml, was combined in vitro with amikacin, gentamicin, netilmicin, or tobramycin. Incubation at 37 degrees C resulted in an apalcillin concentration-dependent and time-dependent decrease of aminoglycoside activity of up to 60%. Amikacin was the most stable and tobramycin was the least stable aminoglycoside under the conditions tested.

Amikacin

Use of the Bac-T-Screen to predict bacteriuria from urine specimens held at room temperature.

Results from the Bac-T-Screen (BTS) of fresh urine specimens were compared with the BTS results obtained when the same urine specimens had been held at room temperature for 24 h. Of the 246 specimens studied, 43 were initially BTS positive, 11 were false-negative, and 39 had greater than or equal to 10(5) CFU/ml. After 24 h at room temperature an additional 60 specimens had greater than or equal to 10(5) CFU/ml, of which only 16 were BTS positive; 10 specimens still gave false-negative results, and the number of false-positive specimens increased by only 6.5% of all specimens. For significant specimens (containing greater than or equal to 10(5) CFU of probable pathogens per ml), the predictive value of a negative test changed by only 0.1% (99.5 to 99.4%), whereas the sensitivity of the test remained at 96.4% for incubated specimens. Of those specimens that developed greater than or equal to 10(5) CFU/ml in vitro, 85% contained gram-negative bacilli. Neither bacteria grown in vitro nor urine specimens from normal females containing greater than or equal to 10(5) CFU/ml were positive with the BTS. For reasons not entirely understood, the BTS system may be unique in its ability to discriminate between bacteria which represent true bacteriuria and those which are present because of contamination, possibly due to other cellular elements present in infection-related bacteriuria, namely leukocytes and sloughed bladder epithelial cells.

Bacteriological Techniques

Effect of urine preservation on urine screening and organism identification.

Three urine preservation-transport methods were examined for their effect on rapid urine-screening procedures. Results from fresh urine specimens, screened for bacteriuria by leukocyte esterase, nitrate, Autobac, Bac-T-Screen, Auto Microbic System (AMS), and bioluminescence procedures, were compared with urine-screen results from urine specimens held for 24 hours at room temperature in chemical preservatives. Quantitative discrepancies ranged from 0%, for urine preserved with glycerin-boric acid-sodium formate and tested by AMS or leukocyte esterase, to 21% for urines in the same preservative tested by bioluminescence or nitrate. Up to 62% of the organism identifications made from preserved urine specimens tested by the AMS urine card were in error. These data suggest that it may be inadvisable to use weak organic acid-based urine preservation systems in conjunction with these urine-screen procedures.

Bacteriuria

Gram stain in Legionnaires' disease.

A case of Legionnaires' disease is presented in which gram staining of impression smears from lung biopsy specimens showed Legionella pneumophila while other laboratory findings remained negative. This case illustrates the usefulness of gram staining in this disease and in the management of therapy.

Bacteriological Techniques

In vitro susceptibility of Nocardia asteroides to 25 antimicrobial agents.

Fifty-two clinical isolates of Nocardia asteroides were tested by agar dilution for their susceptibility to 25 antimicrobial agents. In general, susceptibility could not be predicted based on the antibiotic class tested. However, the beta-lactams, including third-generation cephalosporins, were generally ineffective (MIC for 90% of the organisms [MIC90], between 64 and greater than 256 micrograms/ml), whereas minocycline and doxycycline were generally effective (MIC90, 4 and 8 micrograms/ml, respectively). Cycloserine was not effective below 60 micrograms/ml. The MIC50 and MIC90 of sulfamethoxazole was 16 and 32 micrograms/ml, respectively, and that of trimethoprim varied widely (16 and greater than 256 micrograms/ml, respectively). Based on MIC90 data, only doxycycline, minocycline, sulfamethoxazole, and imipenem could be applied empirically.

Anti-Bacterial Agents

Mycobacterium thermoresistibile infection in an immunocompromised host.

This is the second report of Mycobacterium thermoresistibile as the etiological agent of a pulmonary granuloma and the first occurrence of this organism in a patient who has not been outside the continental United States. The organism is susceptible to rifampin, ethambutol, and streptomycin but resistant to isoniazid and p-aminosalicylic acid.

Granuloma

Cefoperazone: regression analysis, disk content, and disk susceptibility testing considerations.

Cefoperazone agar dilution minimal inhibitory concentration (MIC) susceptibility results were compared with zones of inhibition produced by disk diffusion susceptibility testing. Disks containing 30, 50, 75, and 100 micrograms of cefoperazone were tested for purposes of regression line comparisons and error rate-bounded analysis. Results suggest that if the MIC equivalent of susceptibility is 32 micrograms/ml, either a 50-micrograms disk with zone sizes of susceptibility (S) greater than or equal to 15 mm and resistance (R) less than or equal to 12 mm or a 75-micrograms disk with zone sizes of S greater than or equal to 17 mm and R less than or equal to 14 mm may be appropriate. If the MIC equivalent of susceptibility is 64 micrograms/ml, this would dictate use of a 75-micrograms disk with zone sizes of S greater than or equal to 17 mm and R less than or equal to 12 mm. Disks containing either less than or equal to 30 or greater than or equal to 100 micrograms of cefoperazone did not adequately discriminate among susceptible and resistant bacterial strains at either the 32- or 64-micrograms/ml MIC equivalent.

Anti-Bacterial Agents

Rapid screening for bacteriuria by light scatter photometry (Autobac): a collaborative study.

A total of 2,720 urine specimens from three laboratories were evaluated by Autobac (Pfizer Diagnostics) and were compared with simultaneous colony counts for evidence of bacteriuria. Of 599 specimens with a colony count of greater than or equal to 10(5) colony-forming units per ml, 93.8% were detected within 6 h. This detection rate increased to 97% of 447 positive urine specimens when only specimens from patients not on antimicrobials were evaluated. The majority (77.9%) of positive specimens were detected as early as 3 h. Those specimens with greater than or equal to 10(5) colony-forming units per ml, which were negative by Autobac at 6 h, included organisms which are frequently considered to be contaminants (diphtheroids, lactobacilli, alpha and gamma streptococci, yeasts, and Staphylococcus epidermidis), or were from patients who were being treated with antimicrobial agents. Of 2,121 urine specimens with colony counts of less than 10(5), 98.1% were correctly determined to be negative by Autobac at 3 h. This percentage decreased to 86.0 at 6 h. The majority of these false-positive specimens were those with colony counts of 10(4) to 10(5) colony-forming units per ml. There appeared to be no major difference in results from the three laboratories or among the four lots of broth used in this study.

Anti-Bacterial Agents

Bioassay of antibiotics in body fluids from patients receiving cancer chemotherapeutic agents.

Patients receiving antitumor chemotherapy are at increased risk of developing nosocomial infections, and the antibacterial therapy of such infections is often monitored by bioassay. The effect of antitumor agents on seven bioassay procedures using strains of Sarcina, Klebsiella, Clostridium, Pseudomonas, Staphylococcus aureus, and S. epidermidis or Bacillus was evaluated. The minimum inhibitory concentrations of six antitumor drugs, cytarabine, dactinomycin, doxorubicin, 5-fluorouracil, methotrexate, and vinblastine, determined for each of the test organisms, showed that 5-fluorouracil, dactinomycin, and doxorubicin are used at blood levels sufficient to interfere with bioassay procedures. The other drugs have minimum inhibitory concentrations as much as 100 times the expected blood levels. Antibiotic (gentamicin, kanamycin, cephalothin, and carbenicillin) recovery experiments in the presence of therapeutic levels of antitumor agents showed no in vitro inactivation of antibiotic. However, at low cephalothin concentrations (less than 20 microgram/ml) in the presnce of 5-fluorouracil, bioassay results were in error by as much as 100%. The data indicate that bioassay procedures for the determining of antibacterial drug levels may need to be modified for those patients receiving antitumor therapy with 5-fluorouracil, doxorubicin, or dactinomycin.

Anti-Bacterial Agents

Use of preserved organisms for individual test-use quality control of bacterial typing antisera.

Bacterial antigens representing 14 of the most common clinical isolates requiring serological confirmation for identification were prepared. These antigens were stable for periods in excess of 5 months, readily available, and sero-specific. Use of these antigens for quality control of bacterial typing antisera increased the accuracy, reduced the technician time, and obviated the delay which otherwise occurred while stock isolates were subcultured to provide a sero-specific control for this procedure.

Antigens, Bacterial

A serologic survey of mule deer and elk in Utah.

Sera from mule deer (Odocoileus hemionus) and elk (Cervus canadensis) in central and northern Utah were tested for the prevalence of antibodies to 11 diseases communicable to man or domestic livestock. Antibodies to Francisella tularensis (at 1:20) were found in 47 of 88 (53.4%) elk and 1 of 89 (1.1%) deer. A screening slide agglutination test for titers to Brucella (at 1:20) showed two reactors in elk but none in deer sera. No positive antibody titers were obtained in tests for anaplasmosis, Colorado tick fever, Rocky Mountain spotted fever, Q-fever, psittacosis, Powassan, western equine encephalitis, St. Louis encephalitis and California encephalitis.

Animals