Biomedical subjects

G V Doern

Publications and source records attributed to G V Doern.

At least 55 records · Page 3Linked to original sources

PubMed1999

Colony morphology of Candida spp. as a guide to species identification.

The presence of colony projections, often referred to as "feet," have typically been considered a characteristic of Candida albicans. In the current study that examined the colony morphology of numerous different species of Candida, several clinical isolates of Candida tropicalis and Candida krusei were also noted to produce "feet." The medium and growth conditions under which colony projections were produced by these species were characterized.

Candida↗

PubMed1999

Multicenter evaluation of the antimicrobial activity for seven broad-spectrum beta-lactams in Turkey using the Etest method. Turkish Antimicrobial Resistance Study Group.

From March through July 1997, a nine laboratory surveillance project was initiated in Turkey to monitor the potency and spectrum of seven broad-spectrum antimicrobial agents (cefepime, ceftazidime, cefotaxime, imipenem, aztreonam, cefoperazone/sulbactam, and ticarcillin/clavulanate) tested against approximately 100 organisms (average 82; range 70 to 95 isolates) per participant center (736 strains). Eleven groups of organisms were tested by the Etest method (AB BIODISK, Solna, Sweden) with results validated by concurrent quality control strain analysis. Results from all centers were tabulated and 91.1% of quality assurance tests were within ranges recommended by the National Committee for Clinical Laboratory Standards. Among the seven beta-lactam-class drugs tested, imipenem and cefepime were the most active beta-lactams tested against all isolates. Overall, the rank order of susceptibility of the seven agents was imipenem > cefepime > cefoperazone/sulbactam > ceftazidime > cefotaxime > aztreonam > ticarcillin/clavulanate. Both cefepime and imipenem were active against ceftazidime-resistant strains of Enterobacteriaceae as well as against Streptococcus spp. and oxacillin-susceptible Staphylococcus aureus. Resistance phenotypes consistent with extended spectrum beta-lactamases were documented among Escherichia coli and Klebsiella spp., and profiles consistent with stably derepressed Bush-Jacoby-Mederios group 1 (Amp C) cephalosporinases were common among Enterobacter spp., Citrobacter spp., and Serratia spp. These data should be used to guide empiric therapy with beta-lactams in Turkey, and additionally will provide a reference statistical baseline to which future national studies of drugs in this class can be compared.

Anti-Bacterial Agents↗

PubMed1999

Multicenter evaluation of the antimicrobial activity for six broad-spectrum beta-lactams in Venezuela: comparison of data from 1997 and 1998 using the Etest method. Venezuelan Antimicrobial Resistance Study Group.

The minimum inhibitory concentrations of six broad-spectrum beta-lactam antimicrobial agents were determined in 1998 by use of the Etest versus a total of 502 bacteria in seven Venezuelan hospital laboratories. These data were compared with results of a similar study performed in 1997. The organisms tested included 309 recent clinical isolates of Enterobacteriaceae, 70 Pseudomonas aeruginosa, 54 Acinetobacter species, and 69 oxacillin-susceptible Staphylococcus aureus. Extended spectrum beta-lactamase production was noted among 30% of Klebsiella pneumoniae isolates. Hyperproduction of Amp C cephalosporinase producing resistance to ceftazidime and cefotaxime was observed with 10 to 37% of isolates of Enterobacter spp., Serratia spp., and Citrobacter freundii. The overall rank order of activity of the six beta-lactams tested in this study against all clinical isolates was imipenem (96.6% susceptible) > cefepime (90.4%) > piperacillin/tazobactam (85.7%) > ceftazidime (73.5%) > cefotaxime (70.5%) > piperacillin (55.0%). These findings were very similar to those reported for 1997.

Anti-Bacterial Agents↗

PubMed1999

Multicenter evaluation of antimicrobial resistance to six broad-spectrum beta-lactams in Colombia: comparison of data from 1997 and 1998 using the Etest method. The Colombian Antimicrobial Resistance Study Group.

The minimum inhibitory concentrations of six broad-spectrum beta-lactam antimicrobial agents were determined in 1998 by use of the Etest versus a total of 823 bacteria in 11 Colombian hospital laboratories. These data were compared with results of a similar study conducted in 1997. The organisms tested included 532 recent clinical isolates of Enterobacteriaceae, 108 Pseudomonas aeruginosa, 94 Acinetobacter species, and 89 oxacillin-susceptible Staphylococcus aureus. Extended-spectrum beta-lactamase production was noted among 27.8 to 33.9% of Escherichia coli isolates and 41.7 to 46.7% of Klebsiella spp. isolates. Hyperproduction of Amp C cephalosporinases was observed with 10.5 to 31.4% of isolates of Enterobacter spp., Serratia spp., and Citrobacter spp. An increase in resistance to all of the beta-lactams was observed among Enterobacteriaceae, Acinetobacter spp. and P. aeruginosa when 1998 results were compared with those obtained in 1997. The overall rank order of activity of the six beta-lactams tested in 1998 versus all clinical isolates was imipenem (93.2% susceptible) > cefoperazone/sulbactam (84.1%) > cefepime (80.9%) > ceftazidime (70.7%) > aztreonam (65.7%) > cefotaxime (65.6%). In contrast, the rank order of these same agents tested against a similar collection of Colombian isolates in 1997 was imipenem (96.6% susceptible) > cefepime (93.6%) > cefoperazone/sulbactam (90.5%) > cefotaxime (74.9%) > aztreonam (74.3%) > ceftazidime (73.2%).

Colombia↗

PubMed1999

A 1997-1998 national surveillance study: Moraxella catarrhalis and Haemophilus influenzae antimicrobial resistance in 34 US institutions.

From November 1, 1997 to April 30, 1998, 726 Moraxella catarrhalis isolates and 1529 Haemophilus influenzae isolates were obtained from 34 medical centres throughout the United States. Rates of beta-lactamase production were 94.6% among M. catarrhalis and 31.1% among H. influenzae strains. Susceptibility rates of M. catarrhalis isolates to selected antimicrobial agents were greater than 99% for amoxycillin-clavulanate, cefixime, cefpodoxime, cefuroxime, cefaclor, loracarbef, clarithromycin, azithromycin, chloramphenicol and tetracycline, 97.8% for cefprozil, 50.4% for trimethoprim-sulphamethoxazole and 28.1% for ampicillin. Of the antimicrobials tested against H. influenzae, the only agents with susceptibility rates below 96% were loracarbef (87.6%), cefprozil (83.4%), cefaclor (82.7%), trimethoprim-sulphamethoxazole (67.3%) and ampicillin (64.7%). The clarithromycin susceptibility rate was 67.4% but this agent was not tested in the presence of its 14-OH metabolite.

Adolescent↗

PubMed1999

Prevalence of macrolide resistance mechanisms in Streptococcus pneumoniae isolates from a multicenter antibiotic resistance surveillance study conducted in the United States in 1994-1995.

Two main mechanisms of macrolide resistance have been described in erythromycin-resistant Streptococcus pneumoniae (ERSP): a ribosomal methylase, ErmAM, and a macrolide efflux pump, MefE. In this study, we examined the prevalence of these mechanisms in 114 clinical isolates of ERSP from a 30-center study conducted in the United States between November 1994 and April 1995. The isolates were screened by polymerase chain reaction for the presence of known macrolide resistance genes. Seventy (61%) ERSP contained the macrolide efflux gene (mefE), whereas 36 isolates (32%) contained the biosomal methylase gene (ermAM). Isolates that were ermAM-positive had constitutive macrolide resistance. The minimum inhibitory concentrations (for which 90% of isolates were susceptible) of clarithromycin for the efflux-positive strains were much lower than those for the ermAM-positive strains (4 microg/mL vs. >128 microg/mL, respectively). The efflux mechanism is the predominant form of macrolide resistance in the United States.

Anti-Bacterial Agents↗

PubMed1999

Simultaneous respiratory tract colonization by multiple strains of nontypeable haemophilus influenzae in chronic obstructive pulmonary disease: implications for antibiotic therapy.

Nontypeable Haemophilus influenzae often causes exacerbations of chronic obstructive pulmonary disease (COPD), and these exacerbations are frequently treated with oral antibiotics. The goals of this study were to determine the frequency of the simultaneous presence of multiple strains of H. influenzae in sputum and to measure the MICs of antibiotics for the isolates. In a prospective study, adults with COPD were seen monthly. Sputum cultures were obtained, and individual colonies were subjected to genomic DNA typing and MIC determinations. Multiple strains of H. influenzae were present simultaneously in the sputum of 26.3% of adults with COPD. In 64.5% of these, MICs of >/=1 antibiotic varied by >/=4-fold among the strains. Therefore, multiple strains of H. influenzae are frequently present simultaneously in the sputum of adults with COPD, and the antimicrobial susceptibility of different strains in the same sputum sometimes differs.

Aged↗

PubMed1999

Survey of bloodstream infections due to gram-negative bacilli: frequency of occurrence and antimicrobial susceptibility of isolates collected in the United States, Canada, and Latin America for the SENTRY Antimicrobial Surveillance Program, 1997.

During 1997, a total of 4,267 nosocomial and community-acquired bloodstream infections due to gram-negative organisms were reported from SENTRY hospitals in Canada (8 sites), the United States (30 sites), and Latin America (10 sites). Escherichia coli was the most common isolate (41% of all gram-negative isolates), followed by Klebsiella species (17.9%), Pseudomonas aeruginosa (10.6%), and Enterobacter species (9.4%). For all gram-negative isolates combined, the most active antimicrobials tested were meropenem, imipenem, and cefepime. The quinolones levofloxacin (MIC90, 2 microg/mL), ciprofloxacin (MIC90, 1 microg/mL), gatifloxacin (MIC90, 2 microg/mL), sparfloxacin (MIC90, 2 microg/mL), and trovafloxacin (MIC90, 2 microg/mL) were also active against most isolates. Bloodstream infection isolates from Latin America were uniformly more resistant to all classes of antimicrobial agents tested than were isolates from Canada or the United States. Resistance phenotypes consistent with extended-spectrum beta-lactamase production were also most common among E. coli and Klebsiella species from Latin America. Further investigation of the reasons for regional differences in resistance patterns is needed, as is ongoing surveillance to detect resistance trends and to guide antimicrobial use.

Bacteremia↗

PubMed1999

Haemophilus influenzae and Moraxella catarrhalis from patients with community-acquired respiratory tract infections: antimicrobial susceptibility patterns from the SENTRY antimicrobial Surveillance Program (United States and Canada, 1997).

Between February and June of 1997, a large number of community-acquired respiratory tract isolates of Haemophilus influenzae (n = 1,077) and Moraxella catarrhalis (n = 503) from 27 U.S. and 7 Canadian medical centers were characterized as part of the SENTRY Antimicrobial Surveillance Program. Overall prevalences of beta-lactamase production were 33.5% in H. influenzae and 92.2% in M. catarrhalis with no differences noted between isolates recovered in the United States and those from Canada. Among a total of 21 different antimicrobial agents tested, including six cephalosporins, a beta-lactamase inhibitor combination, three macrolides, tetracycline, trimethoprim-sulfamethoxazole (TMP-SMX), rifampin, chloramphenicol, five fluoroquinolones, and quinupristin-dalfopristin, resistance rates of > 5% with H. influenzae were observed only with cefaclor (12.8%) and TMP-SMX (16.2%).

Anti-Bacterial Agents↗

PubMed1999

In vitro activities of BMS-207147 against over 600 contemporary clinical bloodstream isolates of Candida species from the SENTRY Antimicrobial Surveillance Program in North America and Latin America.

We compared the in vitro activity of BMS-207147, an investigational triazole, with those of itraconazole and fluconazole against 613 clinical bloodstream isolates of Candida spp. collected from SENTRY participating hospitals during 1997 and 1998. Overall, BMS-207147 was the most active azole against all Candida spp. While both BMS-207147 and itraconazole displayed a stepwise decrease in activity against isolates for which the fluconazole MICs were elevated, BMS-207147 had two- to fourfold greater activity than itraconazole both against Candida spp. that were dose-dependently fluconazole susceptible and against those that were fluconazole resistant.

Antifungal Agents↗

PubMed1999

Assessment of laboratory performance with Streptococcus pneumoniae antimicrobial susceptibility testing in the United States: a report from the College of American Pathologists Microbiology Proficiency Survey Program.

OBJECTIVE: To assess the performance of clinical microbiology laboratories in the United States when conducting in vitro susceptibility tests with Streptococcus pneumoniae. METHODS: The results of a nationwide College of American Pathologists Proficiency Survey test sample, in which susceptibility testing of an isolate of S. pneumoniae was performed, were assessed with respect to precision and accuracy. RESULTS: Wide variability was noted among participating laboratories with both minimum inhibitory concentration procedures and disk diffusion susceptibility tests when both methods were applied to S. pneumoniae. Despite this high degree of variation, categorical interpretive errors were uncommon. Numerous laboratories reported results for antimicrobial agents that are not recommended by the National Committee for Clinical Laboratory Standards for tests with S. pneumoniae. CONCLUSIONS: Current susceptibility testing practices with S. pneumoniae in the United States indicate limited precision and a tendency for laboratories to test and report results obtained with antimicrobial agents of questionable therapeutic value against this organism. Continued efforts to standardize susceptibility testing of S. pneumoniae in the United States are warranted. In addition, modifications of existing interpretive criteria may be necessary.

Anti-Bacterial Agents↗

PubMed1998

Influence of triple-lumen central venous catheters coated with chlorhexidine and silver sulfadiazine on the incidence of catheter-related bacteremia.

OBJECTIVE: To evaluate the efficacy of triple-lumen central venous catheters coated with a combination product of chlorhexidine and silver sulfadiazine (CSS) in reducing the incidence of local catheter infection and catheter-related bacteremia. DESIGN: Randomized, controlled trial. SETTING: The surgical intensive care units in a university hospital. PATIENTS: All patients who needed central venous catheterization were randomized to receive either an uncoated triple-lumen catheter (n = 157) or a catheter coated with CSS (n = 151). MAIN OUTCOME MEASURE: Catheters were removed when no longer needed or suspected as a cause of infection. The tip and a 5-cm segment of the intradermal portion of the catheter were cultured semiquantitatively. Blood cultures were obtained when clinically indicated. The remaining segment of catheters coated with CSS were cut and incubated on an agar plate with strains of Staphylococcus aureus and Enterococcus. Zone of inhibition was determined 24 hours later. Data were analyzed by survival and logistic multivariate regression methods. RESULTS: Catheters coated with CSS were effective in reducing the rate of significant bacterial growth on either the tip or intradermal segment (40%) compared with control catheters (52%; P = .04). However, there was no difference in the incidence of catheter-related bacteremia (3.8% [uncoated] vs 3.3% [coated]; P = .81). In vitro activity of catheters with CSS against S aureus was evident up to 25 days but activity against Enterococcus dissipated more quickly over time and was absent by day 4. The most common colonizing organisms were coagulase-negative staphylococcus and enterococcus. Variables that were associated with a significant amount of growth on the tip or intradermal segment were a duration of catheterization of longer than 7 days, jugular insertion site, and the absence of a CSS coating. The use of a guidewire when the catheter was removed was associated with a lower risk of significant bacterial growth. CONCLUSIONS: The use of CSS reduces the incidence of significant bacterial growth on either the tip or intradermal segments of coated triple-lumen catheters but has no effect on the incidence of catheter-related bacteremia. In this patient population, catheters coated with CSS provide no additional benefit over uncoated catheters.

Anti-Infective Agents, Local↗

PubMed1998

Multicenter evaluation of the antimicrobial activity for six broad-spectrum beta-lactams in Venezuela using the Etest method. The Venezuelan Antimicrobial Resistance Study Group.

In early 1997, a 15-laboratory surveillance project was initiated in Venezuela to monitor the potency and spectrum of 6 broad-spectrum antimicrobial agents (cefepime, cefotaxime, ceftazidime, piperacillin, piperacillin/tazobactam, and imipenem) tested against approximately 100 organisms per participant center (1297 strains). Ten groups of organisms were tested by the Etest method (AB BIODISK, Solna, Sweden) with results validated by concurrent quality control strain analysis. Results from all centers were tabulated and 96.3% of quality assurance tests were within ranges recommended by the National Committee for Clinical Laboratory Standards. Among the six beta-lactam class drugs tested, imipenem and cefepime were the most active against all isolates tested. Overall, the rank order of susceptibility of the six agents was imipenem (97.2%, susceptible; MIC90 2 micrograms/ml) > cefepime (92.8%; MIC90 6 micrograms/mL) > piperacillin/tazobactam (77.2-83.0%; MIC90 > 256 micrograms/mL) > cefotaxime (72.2%; MIC90 > 256 micrograms/mL) > piperacillin (56.8-65.8%; MIC90 > 256 micrograms/mL) > ceftazidime (64.66%; MIC90 128 micrograms/mL). Both cefepime and imipenem were active against ceftazidime-resistant strains of Enterobactericaeae as well as against Pseudomonas aeruginosa and oxacillin-susceptible staphylococci. Resistance phenotypes consistent with extended spectrum beta-lactamases (ESBLs) and stably derepressed Bush group 1 cephalosporinases were documented in strains of Klebsiella spp. and Enterobacters, respectively. These data should be used to guide empiric therapy with beta-lactams in Venezuela, and additionally will provide a reference statistical baseline to which future studies in this nation can be compared.

Acinetobacter↗

PubMed1998

Multicenter evaluation of the in vitro activity of six broad-spectrum beta-lactam antimicrobial agents in Puerto Rico. The Puerto Rico Antimicrobial Resistance Study Group.

The minimum inhibitory concentrations of 6 broad-spectrum beta-lactam antimicrobial agents were determined by use of the Etest versus a total of 569 bacteria in 7 Puerto Rican hospital laboratories. These included 342 recent clinical isolates of Enterobacteriaceae, 63 Pseudomonas aeruginosa, 54 Acinetobacter species, and 110 oxacillin-susceptible staphylococci. Extended spectrum beta-lactamase production was noted among 11% of Klebsiella pneumoniae isolates. Hyperproduction of Amp C cephalosporinase was observed with > 20% of isolates of Enterobacter spp., Serratia spp., and Citrobacter freundii. The overall rank order of activity of the six beta-lactams examined in this study versus all clinical isolates was imipenem (95.8% susceptible) > cefepime (91.1%) > piperacillin/ tazobactam (82.3%) > cefotaxime (77.6%) > piperacillin (72.5%) > ceftazidime (67.0%).

Anti-Bacterial Agents↗

PubMed1998

Pichia ohmeri fungemia.

A patient with a history of diabetes, coronary artery disease, stroke, previous renal transplantation, and multiple hospital admissions for recurrent pancreatitis was transferred to the hospital from a chronic care facility because of fever and severe epigastric discomfort. At the time of admission, she was receiving hyperalimentation through a central venous TPN catheter. Multiple blood cultures obtained on the first and second hospital days yielded pure cultures of the yeast, Pichia ohmeri. The patient developed acute renal failure, and despite high-dose amphotericin B therapy, ultimately expired.

Female↗

PubMed1998

Antimicrobial activity and spectrum investigation of eight broad-spectrum beta-lactam drugs: a 1997 surveillance trial in 102 medical centers in the United States. Cefepime Study Group.

Because antimicrobial agents become less effective after the emergence of resistance mechanisms in clinically prevalent pathogens, physicians must utilize local, regional, and national antimicrobial susceptibility surveillance data to assist in choices of appropriate agents. An investigation of the spectrum and potency of eight broad-spectrum beta-lactam drugs (cefepime, cefotaxime, ceftazidime, ceftriaxone, imipenem, piperacillin with or without tazobactam, and ticarcillin/clavulanic acid) was performed using a common protocol and method (Etest; AB BIODISK, Solna, Sweden) in 102 clinical microbiology laboratories in the United States. A total of 9777 strains of Gram-negative bacilli were tested from late 1996 through April 1997. Quality assurance measures using three control strains observed quality control failures in 13 laboratories (usually ticarcillin/clavulanic acid or piperacillin), but only 2% of results required deletion. A total of 33.4% of Enterobacter spp. (1977 strains) were either resistant or intermediately susceptible to ceftazidime. Only imipenem (99.6% susceptible) and cefepime (99.1%) remained highly active against strains of Enterobacter, as well as Citrobacter freundii, indole-positive Proteae, and Serratia spp. Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae were detected at rates of 10.3% and 23.8%, respectively. Although these were participant-selected strains, only imipenem and cefepime had broad-spectrum coverage (> or = 97.1%) against these extended-spectrum beta-lactamase phenotypes. A dominant number of these extended-spectrum beta-lactamase phenotypes were reported from medical centers in the Northeast, but a nationwide distribution was observed. Among the nonenteric Gram-negative bacilli (4057 strains), the rank order of susceptibility (percent inhibited at published breakpoint concentrations) was: imipenem (86.1%) > piperacillin/tazobactam (80.1%) > cefepime (77.1%) > ceftazidime = piperacillin (74.9%) > ticarcillin/clavulanic acid (61.6%) > cefotaxime (18.2%) > ceftriaxone (12.9%). The cephalosporins, cefepime and ceftazidime, had rates of resistance for the 3005 Pseudomonas aeruginosa isolates of 10.1% and 14.4%, respectively. For all Gram-negative strains tested, only two contemporary beta-lactam antimicrobials exhibited > 90% inhibition of strains, imipenem at 93.6% and cefepime at 90.2%. These drugs were superior to the other tested compounds (48.8-84.3%). Ticarcillin/clavulanic acid had the narrowest spectrum of activity (48.8% of isolates susceptible). These results indicate that carbapenems and a new fourth-generation cephalosporin, cefepime, possess usable in vitro potencies against current clinical strains of Gram-negative bacilli, many of which harbored resistance to other antimicrobial agents.

Anti-Bacterial Agents↗

PubMed1998

Enhancement of varicella-zoster virus detection in A-549 shell vials by use of freeze-thawed specimens, extended incubation, and "a centrifuged, not incubated" direct detection method.

A total of 95 clinical samples were cultured for periods of 2 and 7 days in centrifuged A-549 shell vials before and after freezing and thawing of specimens. In addition, centrifuged A-549 shell vials were tested directly for varicella-zoster virus without incubation using a direct fluorescent antibody (DFA) technique. Twenty-seven specimens were positive by at least one method. The sensitivity for DFA on unincubated A-549 shell vials was 85.2%; for unfrozen 2-day cultures, 88.9%; for unfrozen 7-day cultures, 92.6%; for freeze-thaw 2-day cultures, 92.6%; and for freeze-thaw 7-day cultures, 96.3%. Freeze-thawed specimens cultured for 7 days yielded the highest number of positive results with conspicuous cell-to-cell spread as a sign of viral replication.

Cell Line↗

PubMed1998

Evaluation of the Vitek system to accurately test the susceptibility of Pseudomonas aeruginosa clinical isolates against cefepime.

A total of 300 recent blood stream and pneumonia isolates of Pseudomonas aeruginosa from 32 different medical centers in the United States were used to assess the accuracy of the Vitek System (GNS-107 card) for cefepime, a new "fourth-generation" cephalosporin. The Vitek System test result was compared to the consensus of the three other methods (reference broth microdilution, disk diffusion, Etest (AB BIODISK, Solna, Sweden)); and 271 of 300 consensus category of susceptibility sets were unanimous. The Vitek System produced a 25.3% error rate (5.3% false resistance, 20.0% minor errors). A consistent trend toward higher MIC results with the Vitek System was observed that produced a 15.3 to 21.3% lower susceptible rate compared with the other susceptibility test methods. The consensus cefepime resistance rate was only 4.3% compared to 14.0% for the Vitek GNS-107 card. The error was reproducible on triplicate repeat testing. These results indicate an unacceptable rate of false resistance being produced by the Vitek System when testing cefepime against P. aeruginosa strains. Alternative methods are suggested for this broad-spectrum antipseudomonal cephalosporin.

Bacteremia↗