PubMed Health⌕ Search

Biomedical subjects

D F Welch

Publications and source records attributed to D F Welch.

At least 55 records · Page 3Linked to original sources
PubMed1987

Selective and differential medium for recovery of Pseudomonas cepacia from the respiratory tracts of patients with cystic fibrosis.

A selective and differential medium, OFPBL (oxidation-fermentation base supplemented with agar, lactose, and two antimicrobial agents), for the isolation of Pseudomonas cepacia from respiratory specimens of patients with cystic fibrosis was developed and tested. Among 725 specimens submitted from seven centers over a 4- to 6-month period, 58 (8%) yielded P. cepacia on OFPBL; only 19 of these were recovered on MacConkey or sheep blood agar (P less than 0.001). No isolate was recovered on MacConkey or sheep blood agar alone. Ranges of recovery rates among centers were 0 to 15% on OFPBL and 0 to 10% on MacConkey or sheep blood agar. Ninety percent of P. cepacia isolates were detected on OFPBL in less than or equal to 3 days. Other nonfermenters and yeasts isolated on OFPBL were distinguished from P. cepacia by failure to acidify the medium. The new medium was clearly superior to MacConkey and sheep blood agars for the isolation of P. cepacia from the respiratory secretions of patients with cystic fibrosis.

Culture Media↗
PubMed1986

Antimicrobial susceptibility of Aeromonas species isolated from patients with diarrhea.

In vitro susceptibility to 17 antimicrobial agents was determined for Aeromonas caviae, A. hydrophila, and A. sobria isolated from feces of patients with diarrhea. The three Aeromonas species shared a similar susceptibility pattern, except to cephalothin. Of the oral antimicrobial agents, the quinolones, followed by chloramphenicol, were most active; trimethoprim-sulfamethoxazole and tetracycline had good but variable activity.

Adult↗
PubMed1985

Low frequency of bacterial resistance to enoxacin in vitro and in experimental pneumonia.

The tendency for bacteria to develop resistance to enoxacin (Cl-919, AT-2266), a new oxyquinolone derivative, was investigated in vitro and in vivo. The mutation frequencies of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Salmonella sp., and Haemophilus influenzae to enoxacin, norfloxacin, nalidixic acid, tobramycin, cephalexin, cefotaxime, ampicillin, azlocillin, oxacillin, and ticarcillin were determined by plating large numbers of organisms onto antibiotic-containing agar. Enoxacin resistance developed infrequently. For example, the mutation frequency of Ps. aeruginosa in the presence of enoxacin was 1 in 2.8 X 10(9) cells as compared to 1 in 1.1 X 10(6) for nalidixic acid. The increase in MIC after serial transfer through increasing concentrations of enoxacin ranged from 8-fold for Ps. aeruginosa and Staph. aureus to 256-fold for H. influenzae. Rats with chronic Ps. aeruginosa pneumonia were given subtherapeutic doses of enoxacin daily for ten weeks. Two rats were sacrificed weekly and the homogenized lungs were cultured on agar containing 5 mg/l of enoxacin and on antibiotic-free agar. No organisms resistant to 5 mg/l of enoxacin were recovered. No increase in the minimum inhibitory concentration of enoxacin for the infecting organism was seen.

Animals↗
PubMed1985

In vitro antibacterial activities of antibiotics against Pseudomonas aeruginosa in peritoneal dialysis fluid.

Intraperitoneal antibiotics are used to treat Pseudomonas aeruginosa peritonitis, a serious complication of continuous ambulatory peritoneal dialysis. However, P. aeruginosa killing is often inefficient despite low MBCs. Broth dilution MIC/MBC and time kill curves of tobramycin, amikacin, netilmicin, azlocillin, piperacillin, ceftazidime, cefsulodin, and ciprofloxacin were determined in peritoneal dialysis fluid (PDF), buffered PDF, fluid recovered from patients on continuous ambulatory peritoneal dialysis (RPF), and cation-supplemented Mueller-Hinton broth. MBCs of all antibiotics were 8 to 16 times greater in PDF and RPF than in Mueller-Hinton broth or buffered PDF. Use of the time kill curve technique and Mueller-Hinton broth showed that aminoglycosides killed greater than or equal to 99.9% of P. aeruginosa at 1 h, ciprofloxacin killed greater than or equal to 99.9% at 2 h, and beta-lactams killed greater than or equal to 99.9% at 6 h. In contrast, killing was not demonstrated in PDF by any drug at 6 h and by aminoglycosides only at 24 h. Bactericidal activity was optimal in RPF for ciprofloxacin at 1 h and for aminoglycosides at 2 h; bactericidal activity was not demonstrated in RPF with any beta-lactam (no kill by penicillins; less than 99% kill by cephalosporins). Slow bacterial growth, increased protein binding, and glucose concentrations and other inhibitors may interfere with beta-lactam activity in RPF. These considerations and reported clinical failures and toxicity of aminoglycoside therapy warrant further study of quinolones and drug combinations in P. aeruginosa peritonitis.

Anti-Bacterial Agents↗
PubMed1985

Recognition of Staphylococcus saprophyticus in urine cultures by screening colonies for production of phosphatase.

Phenolphthalein diphosphate was incorporated into a primary blood agar medium for use in performing quantitative urine cultures. Phosphatase-negative staphylococci, such as Staphylococcus saprophyticus, were differentiated from phosphatase-positive species, such as Staphylococcus epidermidis, by spot testing colonies on filter paper saturated with 1 N NaOH. Phosphatase-positive colonies turned pink within seconds, and phosphatase-negative colonies showed no color. None of 55 S. saprophyticus isolates showed production of phosphatase on this medium. Of 193 consecutive coagulase-negative staphylococci isolated from the urine of 190 adolescent female patients, 84% were phosphatase positive, non-S. saprophyticus species; 16% were phosphatase-negative and indicated S. saprophyticus (22), Staphylococcus haemolyticus (4), Staphylococcus simulans (2), Staphylococcus warneri (1), and Staphylococcus hominis (1). Phosphatase activity was variable in the other flora encountered in the urine cultures. Mixtures of phosphatase-positive and -negative organisms did not cause false-positive reactions.

Adolescent↗
PubMed1985

Evaluation of a lysis direct plating method for pediatric blood cultures.

The Isolator 1.5 Microbial tube (E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.) is a commercially available blood culture system for use in pediatrics. The methodology is based on blood lysis followed by direct plating of the sample on culture media to detect bacteria and fungi. Comparative recovery rates of pathogens from blood collected in this and a conventional broth system were similar. The Isolator detected 104 of 120 clinically significant isolates, whereas 106 of 120 isolates were detected by the broth system. The major advantage of the Isolator methodology was early detection of septicemia. Initial detection of gram-negative bacteria occurred an average of 14.2 h earlier by the Isolator system than by the conventional broth method. The Isolator also permitted quantitation of bacteremia and fungemia. Probable contaminants were recovered from 10.0% of the cultures processed by the Isolator, but steps which could be taken to minimize this problem were identified. The Isolator is a useful method for pediatric blood cultures.

Bacteriological Techniques↗
PubMed1985

Comparison of sedimentation and flotation techniques for identification of Cryptosporidium sp. oocysts in a large outbreak of human diarrhea.

Cryptosporidiosis, previously seen mostly among immunocompromised patients, is now recognized among immunocompetent patients. During a large outbreak of cryptosporidiosis in two day-care centers, we compared two procedures for the demonstration of the organism in preserved stool specimens. Of 703 stool specimens tested by both techniques, Sheather sucrose flotation (SSF) identified 127 (18.1%) as positive for Cryptosporidium sp. oocysts. Ritchie Formalin-ethyl acetate sedimentation (F/EA) plus a modified cold Kinyoun acid-fast stain (MCK) of the sediment identified 129 (18.4%) as positive for Cryptosporidium sp. oocysts. The degree of agreement between the two tests was statistically highly significant (P less than 0.0001). A total of 161 (22.9%) were positive by one technique or the other; 95 (13.5%) were positive by both techniques. A total of 32 specimens were positive by SSF but negative by F/EA plus MCK, and 34 specimens were positive by F/EA plus MCK but negative by SSF. The discrepancies between the two techniques occurred in stool specimens that contained rare to a few oocysts. Other parasitic forms were found by both techniques. F/EA plus trichrome staining recovered 126 (17.9%) specimens with Giardia lamblia, whereas SSF recovered only 42 (6.0%) specimens with G. lamblia. No association (chi 2 = 0.02, P = 0.89) was observed between the presence of G. lamblia and Cryptosporidium sp. in these stool specimens. We concluded that F/EA plus MCK of the sediment was as effective in the concentration and identification of Cryptosporidium sp. oocysts as SSF. F/EA plus MCK may be advantageous as a single concentration method for general parasitology when Cryptosporidium sp. is also being sought.

Child Day Care Centers↗
PubMed1985

A multicenter comparison of related pharmacologic features of cephalexin and dicloxacillin given for two months to young children with cystic fibrosis.

Twenty-one cystic fibrosis patients under 3 years of age were enrolled in an open multicenter study to assess the feasibility of the study design and to compare selected pharmacologic features of cephalexin or dicloxacillin administered orally for 2 months. Patient tolerance and compliance were significantly less for dicloxacillin (p less than .01 and p less than .001, respectively). Superficial Candida infections were more common in the cephalexin group (p = 0.02), however increased stool frequency and nonspecific diaper rashes were more prevalent in patients receiving dicloxacillin (p less than .05). Staphylococcus aureus was isolated from respiratory secretions after 2 months from two dicloxacillin and no cephalexin patients. Areas under the curve and peak serum concentrations were higher for cephalexin (p less than .05 and p = .02), but antistaphylococcal activity in serum was higher for dicloxacillin (p less than .05) due to a lower mean MIC compared to cephalexin. Deep pharyngeal plus routine throat culture yielded more pathogens than either method alone. Express mail and central processing of respiratory specimens was efficient for most organisms, however there was some loss of Streptococcus pneumoniae and Haemophilus influenzae. Cephalexin was associated with better patient acceptance and compliance despite higher rates of superficial fungal infections as compared to dicloxacillin. Cephalexin, routine bacteriologic throat swabs processed locally or centrally, mail-in urine compliance assessment and a multicenter design are feasible components for a long-term prospective evaluation of antibiotic prophylaxis in patients with cystic fibrosis.

Administration, Oral↗
PubMed1984

Evaluation of an enzyme immunoassay for detection of Neisseria gonorrhoeae in an adolescent population.

We compared a modified procedure of Gonozyme , an enzyme immunoassay for detection of gonococcal antigen in urogenital specimens, with bacterial culture for Neisseria gonorrhoeae in a hospital-based adolescent clinic. In 839 patients studied, prevalence of urogenital gonorrhea by culture was 14.3%. The sensitivity of the immunoassay was 90.0%, and the specificity was 98.1%; predictive values for a positive and a negative test result were 88.5% and 98.3%, respectively. Gonozyme was highly accurate in 57 males studied; sensitivity, specificity, and predictive values were 100%. In 782 females, sensitivity was 87.5%, specificity was 98.0%, positive predictive value was 85.7%, and negative predictive value was 98.2%. Patients with false-negative immunoassay results had lower colony counts on culture. Gonozyme is an acceptable substitute for culture in males and in females with intermediate or high prevalence of gonorrhea. Results can be available within three hours.

Adolescent↗
PubMed1984

In vitro antimicrobial activity of aztreonam alone and in combination against bacterial isolates from pediatric patients.

We examined 134 pediatric clinical isolates of Enterobacteriaceae, Pseudomonas aeruginosa, and gram-positive cocci for susceptibility to aztreonam alone and in combination with seven other antibiotics. All 98 gram-negative isolates were susceptible to aztreonam with similar inhibitory and bactericidal activity. Combinations of aztreonam with cefoxitin, ampicillin, or clindamycin were generally indifferent or additive. Synergism was occasionally seen against enteric organisms with aztreonam plus cefoxitin or clindamycin. Combinations of tobramycin and aztreonam were synergistic (62%) against P. aeruginosa; aztreonam plus piperacillin or ticarcillin was additive. Aztreonam did not affect the activity of nafcillin against Staphylococcus aureus, or of ampicillin against species of Streptococcus group B or D. Antagonism was seen only with aztreonam plus cefoxitin against Enterobacter species, but not at clinically significant concentrations. Several combinations of antibiotics with aztreonam should be appropriate for initial therapy of infections in children without major risks of antibacterial antagonism.

Anti-Bacterial Agents↗
PubMed1984

Neutralization of the inhibitory effect of sodium polyanetholesulfonate on Neisseria meningitidis in blood cultures processed with the Du Pont Isolator System.

The inhibitory and bactericidal effects of sodium polyanetholesulfonate on Neisseria meningitidis were neutralized by blood lysis which occurs within the pediatric Isolator 1.5 Microbial tube (E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.). Lysed blood was more effective than 2.5% gelatin in preventing the inhibitory effect. All but 1 of 16 N. meningitidis strains were killed by 0.06% sodium polyanetholesulfonate in the absence of lysed blood, whereas none were killed by 1.0% sodium polyanetholesulfonate when lysed blood was present. The possible clinical relevance of these results was reflected in the improved detection of meningococcemia in children when the Isolator 1.5 Microbial tube was compared with a conventional broth system.

Bacteriological Techniques↗
PubMed1984

Campylobacter enteritis. A 3-year experience.

Campylobacter jejuni was isolated from 135 infants and children seen at the Oklahoma Children's Memorial Hospital over a 3-year period. The comparative frequency of isolation of C. jejuni, Salmonella, and Shigella were 1.5 percent, 2.2 percent, and 3.1 percent, respectively. Campylobacter enteritis was most prevalent during the warm months from May to October, peaking in July. Seventy percent of the afflicted children were 2 years old or younger; only 13 percent were older than 5 years. There were the usual clinical presentations (acute onset of diarrhea, fever, abdominal pain, and bloody stools) of Campylobacter enteritis, but other, less common, patterns also were seen. These included chronic diarrhea without significant systemic manifestations; asymptomatic bloody stools, particularly in neonates; and fever and abdominal pain without diarrhea. Severe complications included hemolytic-uremic syndrome, sepsis associated with septic arthritis and osteomyelitis, and failure to thrive.

Adolescent↗
PubMed1983

Neonatal sepsis and meningitis due to alpha-hemolytic Streptococcus.

We have reported a case of septicemia and meningitis due to alpha-hemolytic Streptococcus in a 5-day-old infant. The microbiologic and clinical characteristics of neonatal infection with this organism lead us to conclude that this bacterium can be pathogenic in the newborn and should not be dismissed as a contaminant.

Adult↗
PubMed1983

In vitro activity of CI-919 (AT-2266), an oral antipseudomonal compound.

We tested CI-919 (AT-2266), a nalidixic acid analog, against 555 gram-positive and gram-negative bacteria, using microbroth or agar dilution methods. The activity of CI-919 was compared with those of cephalosporins, tobramycin, ticarcillin, dicloxacillin, rifampin, chloramphenicol, ampicillin, and trimethoprimsulfamethoxazole. The minimal inhibitory concentrations of CI-919 for 90% of isolates were (in micrograms per milliliter): Pseudomonas spp. (including Pseudomonas aeruginosa), 4.0; Enterobacteriaceae, 0.5; Staphylococcus spp., 2.0; Haemophilus influenzae, 0.12; Campylobacter jejuni, 0.12; and enterococci, 16. The minimal inhibitory concentrations of CI-919 for 90% of 82 tobramycin-resistant, gram-negative strains was 4.0 micrograms/ml. CI-919 was bactericidal for most isolates, showing no cross-resistance with unrelated antimicrobial agents, and was stable for 11 weeks at temperatures ranging from 22 to -70 degrees C. Inoculum size and media pH had little effect on the antibacterial activity of CI-919 for nine strains tested. CI-919 may be useful as an oral antibiotic for the treatment of infections due to diverse bacteria, including P. aeruginosa.

Anti-Bacterial Agents↗
PubMed1983

Effect of inoculum size on Haemophilus influenzae type b susceptibility to new and conventional antibiotics.

Thirty-three Haemophilus influenzae type b isolates, including beta-lactamase acetyltransferase-positive strains, were tested by microtiter broth dilution for susceptibility to eight beta-lactam compounds and chloramphenicol. All antibiotics except ampicillin and chloramphenicol were highly bactericidal against all isolates at an inoculum of 10(5) CFU/ml. However, at an inoculum of 10(5) CFU/ml, the minimal bactericidal concentrations of all drugs except ceftriaxone were above levels usually achievable in cerebrospinal fluid. Results of time-kill studies confirmed this inoculum effect. In vivo studies are needed to test the clinical impact of these observations.

Anti-Bacterial Agents↗
PubMed1983

Evaluation of the Phadebact CSF test for detection of the four most common causes of bacterial meningitis.

A five-center collaborative study was undertaken to determine the suitability of the Phadebact CSF test kit and the Phadebact group B Streptococcus reagent for routine use by clinical laboratories to detect antigens of common organisms causing bacterial meningitis. The kits employ staphylococcal protein A coagglutination to detect the antigens of Haemophilus influenzae types a, b, c, d, e, and f, Neisseria meningitidis groups A, B, C, Y, and W135, Streptococcus pneumoniae (83 serotypes), and group B Streptococcus. A total of 2,817 individual tests were performed on 577 cerebrospinal fluid specimens. The percent positive specimens detected by coagglutination was as follows: overall, 84%; H. influenzae, 97%; group B Streptococcus, 75%; S. pneumoniae, 71%; and N. meningitidis, 58%. Eighty-five of the specimens were also tested by counterimmunoelectrophoresis. Coagglutination was more sensitive than counterimmunoelectrophoresis because it detected 74% of the positive specimens, whereas counterimmunoelectrophoresis detected only 65%. No false-positive results were obtained with coagglutination. The Phadebact CSF test kit is recommended for routine use in screening cerebrospinal fluid samples for antigens of the common organisms causing bacterial meningitis along with the Gram stain and culture for delayed confirmation of the rapid results.

Agglutination Tests↗
PubMed1982

Activities of various beta-lactams and aminoglycosides, alone and in combination, against isolates of Pseudomonas aeruginosa from patients with cystic fibrosis.

The inhibitory and bactericidal activities of carbenicillin, ticarcillin, moxalactam, cefoperazone, azlocillin, piperacillin, ceftazidime, and three aminoglycosides, alone and in various combinations, were determined against 60 isolates of Pseudomonas aeruginosa from the sputum of patients with cystic fibrosis. Ceftazidime was the most active beta-lactam, with minimum inhibitory and bactericidal concentrations for 90% of isolates of 4 micrograms/ml. Moxalactam was the least active of the new beta-lactams, with activity equivalent to that of carbenicillin; each had a minimum inhibitory concentration for 90% of isolates of 64 micrograms/ml and a minimum bactericidal concentration for 90% of isolates of 128 microgram/ml. All combinations of an aminoglycoside plus a beta-lactam showed favorable inhibitory effects. Combinations of beta-lactams showed mostly addition or indifference. Although little antagonism was seen with combinations of beta-lactams or with aminoglycoside-beta-lactam combinations, no consistent advantage of beta-lactam combinations was demonstrated in vitro. These results suggest several single drugs and combinations that merit clinical evaluation in cystic fibrosis patients with Pseudomonas pulmonary infections.

Amikacin↗