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Biomedical subjects

W D Welch

Publications and source records attributed to W D Welch.

At least 19 recordsLinked to original sources
PubMed1990

Quantitative bacteriology of closed-suction wound drainage in contaminated surgery.

This study was designed to evaluate the predictive value of quantitative bacteriology of closed-suction postoperative wound drainage in identifying the patient likely to develop wound infection as well as its subsequent flora. Forty-one patients undergoing major cancer surgery of the head and neck were studied. Postoperatively, closed-suction wound drainage was cultured, and anaerobic and aerobic bacterial isolates were quantitated. The wound infection rate was 20% (8/41). No trend toward increased rate of wound infection with increased numbers of bacteria colonizing the wound was observed. Additionally, there was no consistent correlation between species of bacteria isolated from closed-suction wound drainage and recovery from subsequent wound infection. Quantitative bacteriology of closed-suction wound drainage after contaminated head and neck cancer surgery does not accurately predict which patients were likely to become infected, or the probable bacteriology of subsequent wound infection.

Chi-Square Distribution↗
PubMed1988

Fluorescent monoclonal antibody compared with carbohydrate utilization for rapid identification of Neisseria gonorrhoeae.

A commercially available fluorescein-conjugated monoclonal antibody (MAb) (Syva Co., Palo Alto, Calif.; Genetic Systems, Seattle, Wash.) against Neisseria gonorrhoeae was compared with a standard cystine Trypticase agar (CTA) sugar utilization method and with three rapid carbohydrate utilization tests, including the Minitek (BBL Microbiology Systems, Cockeysville, Md.), Neisseria-Stat (Richardson Scientific, Dallas, Tex.), and Neisseria-Kwik (Micro-Biologics, St. Cloud, Minn.) systems for the identification of Neisseria species. The MAb correctly identified all 86 clinical isolates of N. gonorrhoeae. Of these 86 isolates, 28 were found later (48 h after the initial inoculation) to be contaminated with non-Neisseria bacteria. In the other four test systems studied, the identification rates for pure and contaminated N. gonorrhoeae cultures were, respectively, as follows: CTA sugars, 88 and 32%; Minitek, 67 and 50%; Neisseria-Stat, 97 and 96%; and Neisseria-Kwik, 80 and 74%. The MAb did not identify any of the 50 nongonoccocal Neisseria isolates tested. The most expensive test system was the MAb, followed by the Neisseria-Kwik, Minitek, Neisseria-Stat, and CTA sugars systems. The MAb appears to be a rapid and accurate method to identify in vitro isolates of N. gonorrhoeae.

Antibodies, Monoclonal↗
PubMed1987

Pharmacokinetics of penicillin-G in serum and nasal washings of Pasteurella multocida free and infected rabbits.

Treatment of infections due to Pasteurella multocida in rabbits usually consists of a single intramuscular injection of penicillin G and results in variable cure rates. We report here the levels of penicillin G in serum and nasal washings in P. multocida free and P. multocida infected rabbits following a single intramuscular injection over a 24 hours period. These levels were compared to the minimal inhibitory concentrations (MICS) of 50 clinical isolates of P. multocida of rabbit origin. Infected rabbits demonstrated higher serum levels of penicillin G over P. multocida free rabbits at 1, 3, and 5 hours after the injection. At 16 and 24 hours the penicillin G serum levels dropped to 0.14 and 0.07 microgram/ml, respectively, from 1.90 micrograms/ml at 8 hours. At these levels of penicillin G only 20% of the isolates tested in vitro for susceptibilities (MICs) would be inhibited. Levels of penicillin G in nasal washings at 4 hours after injection were 0.063 microgram/ml, or one-fourth the MIC of 80% of the P. multocida isolates tested (0.25 microgram/ml). In contrast, serum levels of approximately 5 micrograms/ml were seen at this time. Our results suggest that therapeutic blood levels could be achieved if rabbits are given injections of procaine penicillin G at 8 hour intervals.

Animals↗
PubMed1986

Cefotaxime metabolism by hemolyzed blood: quantitation and inhibition of the deacetylation reaction.

The metabolism of cefotaxime (CTX) by hemolyzed blood at different concentrations, time intervals, and temperatures was studied. Cefotaxime and desacetylcefotaxime (DES) levels were quantitated by reverse phase high pressure liquid chromatography. When CTX was added to tubes with 10% hemolysis, CTX/DES levels (micrograms per milliliter) were 123/134, 161/114, and 202/60 at 37 degrees C, room temperature, and 4 degrees C, respectively, after a 1 hr incubation. No reduction in CTX was observed in control experiments (10% blood, no hemolysis) at these temperatures after 1 hr; 200 +/- 23 micrograms/ml CTX; 5 +/- 2 micrograms/ml DES. The disappearance half-life of CTX in 10% hemolyzed blood at 37 degrees C was 45.7 min and at room temperature 84.3 min (p less than 0.001). The addition of the enzyme inhibitors ethylenediaminetetraacetic acid and p-hydroxymercuibenzoate reduced the metabolism of CTX in the presence of 10% hemolysis after 1 hr at 37 degrees C from 41% to 19% with ethylenediaminetetraacetic acid (0.45 mM) and to 0% with p-hydroxymercuibenzoate (10 mM). Our results suggest that for accurate determinations of CTX serum levels, which often have some degree of hemolysis, such specimens should be collected in tubes with ethylenediaminetetraacetic acid or p-hydroxymercuibenzoate and transported at 4 degrees C.

Adult↗
PubMed1986

Five cases of Haemophilus segnis appendicitis.

The clinical, histological, and bacteriological findings in five cases of acute appendicitis caused by Haemophilus segnis are reported. This is the first documentation of appendicitis associated with this organism.

Adolescent↗
PubMed1985

Evaluation of antibiotic susceptibility testing by agar dilution and the Micro Media system (Fox Panel).

The susceptibilities of 350 gram-positive cocci and 638 gram-negative bacilli to various antimicrobial agents were compared by using the Micro-Media system (MMS) (Fox Panel) (Micro-Media Systems, Inc., Potomac, Md.) and a standard agar dilution procedure. Major discrepancies occurred with enterococci, among which 48 of 53 isolates (91%) were found to be resistant to penicillin G by agar dilution and reported as susceptible by the MMS. Other large discrepancies occurred with Staphylococcus aureus and Acinetobacter calcoaceticus subsp. anitratus, among which more than 40% of the isolates were judged to be resistant to ampicillin by agar dilution and susceptible by the MMS. In terms of overall agreement in interpretation of MICs by the two systems, an agreement of greater than 84% was seen for both gram-positive and gram-negative organisms when ampicillin and cephalothin (68 and 78% agreement for gram-positive cocci, respectively) were excluded. These disagreements in MIC interpretations may result in part from the small number of organisms tested per well (4,000 CFU) in the MMS, as compared with 10,000 CFU per test in the agar dilution method.

Acinetobacter↗
PubMed1985

Enflurane and isoflurane inhibit the oxidative activity of pulmonary alveolar macrophages.

Enflurane and isoflurane, widely used general anesthetic agents, were shown to significantly inhibit the microbicidal oxidative activity of pulmonary alveolar macrophages (PAM) at clinically relevant concentrations. This inhibition was reversible, as exposing the anesthetic-treated PAM to air for 30 min completely removed any depression of oxidative activity. Using chemoluminigenic probes to analyze the generation of oxidative metabolites, a significant reduction in superoxide anion (O-2) production was found in PAM exposed to enflurane or isoflurane.

Acridines↗
PubMed1984

Evaluation of the MS-2 and Lumac systems for the rapid screening of urine specimens.

The authors have evaluated the MS-2 (Abbott) and Lumac (3M) systems for the rapid screening of urine specimens for bacteriuria. These systems, which can detect significant levels of microorganisms in urine in five hours (MS-2) or 30 minutes (Lumac), were compared with a standard overnight plate culture method. Three hundred fifty-eight voided urine specimens were examined. The two systems compared equally at greater than 10(5) colony-forming units (CFU)/mL in terms of false-positive results (11%), false-negative results (2%), sensitivity (98%), specificity (approximately equal to 86%), and positive predictive value (98%), although the Lumac was found to have a lower negative predictive value (by 10%) than the MS-2. The only organism not recognized by the MS-2 at greater than 10(5) CFU/mL was a Lactobacillus; whereas the only specimens missed by the Lumac at greater than 10(5) CFU/mL were two pure cultures of Escherichia coli. At counts of greater than 10(4) to 10(5) CFU/mL, both systems missed numerous (15 of 21 isolates for the MS-2; 12 of 9 isolates for the Lumac) gram-positive cocci. The Lumac system was the most costly, being 3.6 times as expensive as the standard plate method. Although both systems greatly reduce the time required to process urine specimens, the large number of false-positive results, false-negative results at greater than 10(4) to 10(5) CFU/mL, as well as cost suggest that a careful evaluation of a laboratory's specific needs for urine cultures be made to determine whether or not such rapid urine screening systems are appropriate.

Bacteria↗
PubMed1984

Interaction of clindamycin and cefpimizole (U63196E) in vitro against aerobic gram-negative rods and aerobic gram-positive cocci.

The combination of clindamycin plus a new semisynthetic cephalosporin, U63196E for which the United States approved name is cefpimizole, was tested against 47 aerobic Gram-negative rods and 30 aerobic Gram-positive cocci. Synergy was seen with Klebsiella pneumoniae (3 of 19 isolates) and Escherichia coli (2 of 21 isolates). All isolates of Pseudomonas aeruginosa, Staphylococcus aureus, methicillin-resistant Staph. aureus, and enterococci demonstrated either indifference or antagonistic reactions to the drug combination.

Cephalosporins↗
PubMed1984

Effect of enflurane, isoflurane, and nitrous oxide on the microbicidal activity of human polymorphonuclear leukocytes.

The effect of enflurane and isoflurane with and without nitrous oxide (N2O) on human polymorphonuclear leukocyte (PMNL) microbicidal function was studied. Bacterial killing was determined using a standard pour-plate technique and by oxidative activity as measured by chemiluminescence (CL). No killing of Escherichia coli, Klebsiella pneumoniae, or Staphylococcus aureus was seen at bacteria:PMNL ratios of 1 or 10:1 with either enflurane or isoflurane at concentrations greater than normally used (3%). However, at a clinically relevant concentration of 2%, a significant inhibition of bacterial killing was observed with enflurane but not isoflurane at a bacteria:PMNL ratio of 100:1. The CL response also was decreased significantly (28% inhibition) by 2% enflurane. N2O 70% plus O2 30% had no effect on bactericidal activity or chemiluminescence alone or in combination with enflurane or isoflurane. The inhibition of bacterial killing and CL following enflurane exposure could be reversed by exposing the enflurane treated PMNL to air for 30 min. These results suggest that enflurane is able to inhibit PMNL microbicidal activity only when the PMNL are stressed with a large bacterial challenge or stimulus. This inhibition is temporal and only occurs during enflurane exposure.

Blood Bactericidal Activity↗
PubMed1984

Unusual susceptibility of methicillin-resistant Staphylococcus aureus to erythromycin, clindamycin, gentamicin, and tetracycline at 30 degrees C but not at 35 degrees C.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in hospital environments, and optimal detection of MRSA requires nonroutine methods in clinical microbiology laboratories. One such method is an incubation temperature of 30 degrees C in contrast to the more commonly used temperature of 35 degrees C. To determine the percentage of MRSA isolates that would be missed if only one temperature were used, we evaluated methicillin resistance and susceptibility of 2,397 S. aureus isolates by agar dilution at 30 and 35 degrees C. Of the clinical isolates, 93% showed matching MICs of methicillin at both temperatures. Another 6.8% (162) showed different MICs at 30 and 35 degrees C, with 60 of the 162 isolates (2.5% of all isolates studied) being resistant to methicillin at 30 degrees C but susceptible at 35 degrees C (temperature-discrepant MRSA). MICs of other antimicrobial agents, measured at 35 degrees C, revealed an unusual pattern of susceptibility of these temperature-discrepant MRSA isolates. In contrast to previously reported resistance of MRSA at 35 degrees C to erythromycin, clindamycin, gentamicin, and tetracycline, the temperature-discrepant MRSA isolates were susceptible to these agents. This resistance pattern may be of value in identifying questionable MRSA isolates when only one incubation temperature is used.

Anti-Bacterial Agents↗
PubMed1984

Variability in CO2, O2, and pH levels in blood culture bottles from five different manufacturers.

The CO2, O2, and pH levels of commercially available blood culture bottles with tryptic soy broth medium from five different manufacturers were compared. Ranges of 1.3 to 6.9% for CO2, 1.1 to 6.0% for O2, and pH 6.94 to 7.26 were found. Different venting procedures revealed that blood culture bottles from which the rubber diaphragm was removed equilibrated the most rapidly (24 h) to the atmosphere (10, 5, and 2.5% CO2) they were incubated in. In contrast, blood culture bottles vented with cotton-plugged needles required 48 h to achieve similar CO2 levels in the medium. The ability of these venting procedures to support bacterial growth was confirmed by measuring the growth of a CO2-dependent Escherichia coli isolate in such vented bottles; blood culture bottles that showed rapid atmospheric (5 and 10% CO2) equilibration had the fastest growth curves. Our results suggest that the differences in the recovery of certain microorganism from blood culture bottles may be due in part to the large variability seen in CO2 and O2 concentrations and the use of various venting procedures.

Bacteria↗
PubMed1984

Evaluation of two bioluminescence-measuring instruments, the Turner Design and Lumac systems, for the rapid screening of urine specimens.

Two bioluminescence-measuring instruments, the Turner Design and Lumac systems, were compared with a standard plate culture method for their ability to rapidly screen 400 urine specimens. For cultures with less than 1,000 CFU/ml the Turner Design, with old and new evaluation formulas, gave 6.5 and 50.6% false-positive results, respectively, versus 17.6% at greater than or equal to 500 relative light units with the Lumac. For cultures which had greater than 10(5) CFU/ml the Turner Design gave 39% (old formula) and 14% (new formula) false-negative results compared with 4% at less than 200 relative units with the Lumac. The microorganisms most frequently isolated in the false-negative cultures from either system were gram-positive cocci. Predictive values for a positive test at greater than 10(5) CFU/ml were 77.4% (old formula) and 35.7% (new formula) for the Turner Design versus only 50% for the Lumac at greater than or equal to 500 relative light units. Predictive values for a negative test for both instruments were greater than 88% at greater than 10(5) CFU/ml. The Turner Design and Lumac systems were 4.0 and 3.7 times as expensive, respectively, as the plate culture method. Although both systems greatly reduce the time required to process urine specimens, their high costs as compared with that of plate culture, their failure to detect many specimens having greater than 10(5) CFU of gram-positive cocci per ml, and the numerous false-positives reported by both instruments suggest that additional improvements in the systems are warranted.

Bacteria↗
PubMed1983

Halothane inhibits the microbicidal oxidative activity of pulmonary alveolar macrophages.

The effect of clinical concentrations of halothane on the microbicidal oxidative activity of pulmonary alveolar macrophages (PAM) was investigated. PAM oxidative activity [generation of the microbicidal oxidative intermediates hydrogen peroxide (H2O2), hydroxyl radicals (OH), and superoxide anions (O2-)] was assessed using luminol and lucigenin chemiluminescence (CL). Whereas luminol CL is an indicator of oxidative activity due to H2O2, OH, or O2-, lucigenin CL provides an ultrasensitive measurement of O2- generation. The use of both chemoluminigenic probes thus enables a detailed analysis of PAM oxidative function. Exposure of PAM to 3, 2, and 1% halothane vaporized in air significantly inhibited both luminol (23-46%) and lucigenin (30-51%) CL responses, P less than 0.01. Halothane-treated PAM exposed to air recovered to the extent that their luminol CL responses were significantly greater than control (no halothane) experiments. Lucigenin reaction mixtures given halothane then air showed less inhibition than PAM treated with halothane only. These results suggest that 1) the generation of O2- and to a lesser extent other oxidative metabolites are decreased following halothane exposure, and 2) this inhibition is reversible.

Acridines↗
PubMed1983

Minimal inhibitory concentrations of 19 antimicrobial agents for 96 clinical isolates of group IVe bacteria.

Susceptibility testing of 96 clinical group IVe isolates to 19 antimicrobial agents by agar dilution revealed that, at drug levels achievable in serum, the isolates were susceptible only to aminoglycosides, cephalosporins, and colistin, whereas at drug concentrations attainable in urine, they were susceptible to erythromycin, tetracycline, and nitrofurantoin as well.

Anti-Bacterial Agents↗