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C C Knapp

Publications and source records attributed to C C Knapp.

36 records · Page 2Linked to original sources
PubMed1991

Comparison of the Vitek Immunodiagnostic Assay System with an indirect immunoassay (Toxostat Test Kit) for detection of immunoglobulin G antibodies to Toxoplasma gondii in clinical specimens.

The value and convenience of testing for specific anti-Toxoplasma gondii antibodies have led to the development of various antibody detection methods, such as the enzyme immunoassay. Two enzyme immunoassays, the Vitek Immuno-Diagnostic Assay System (VIDAS; Vitek Systems, Hazelwood, Mo.) and the Toxostat Test Kit (TST; Whittaker Bioproducts, Walkersville, Md.), were compared for their ability to detect T. gondii immunoglobulin G antibodies in fresh human sera. Specimens were tested according to the instructions of each manufacturer. Of 304 serum specimens tested, the results for 282 (93%) agreed in both assays (77 were positive and 205 were negative). The results for the remaining 22 (7%) specimens were discrepant; 20 of the 22 specimens tested low positive or equivocal by Toxostat and negative by VIDAS. Upon retesting, 8 of these 22 specimens were in concordance, increasing the level of agreement to 95.3%. Intra-assay reproducibility was tested with four to nine replicates of each of seven samples (four positive, one negative, and two equivocal) by both tests and six replicates of one standard by VIDAS. Coefficients of variation (CVs) for VIDAS were 6, 8, 10, 15, 18, 19, and 23% for the samples and 14% for the standard. For Toxostat the CVs were 2, 8, 10, 10, 13, and 16%. In general, CVs for VIDAS were slightly larger than the CVs for Toxostat. Day-to-day variability over 3 days was tested by VIDAS for only six samples (three positive, two negative, and one equivocal) and four standards; CVs ranged from 2 to 15% for the samples and from 6 to 13% for the standards. In conclusions, VIDAS is a rapid, convenient, non-labor-intensive, and easily performed test for the detection of immunoglobulin G antibodies to T. gondii in serum specimens.

Animals↗
PubMed1991

Interpretive criteria and quality control guidelines for Neisseria gonorrhoeae susceptibility test standardization for cefotetan.

Cefotetan was tested in a multilaboratory study to standardize susceptibility testing criteria and quality control guidelines for Neisseria gonorrhoeae. Cefotetan was most active against penicillinase-producing and penicillin-susceptible strains (MIC for 50% of strains tested, 0.5 micrograms/ml) and was least active against the chromosomally resistant isolates (MIC for 50% of strains tested, 2 micrograms/ml). The recommended 30-micrograms disk cefotetan interpretive criteria were as follows: susceptible at greater than or equal to 26 mm (less than or equal to 2 micrograms/ml), intermediate at 20 to 25 mm (4 micrograms/ml), and resistant at less than or equal to 19 mm (greater than or equal to 8 micrograms/ml). Quality control guidelines for agar dilution and disk diffusion tests were established by using numerous GC agar lots, three cefotetan 30-micrograms disk lots, two quality control organisms, and a volume of tests consistent with National Committee for Clinical Laboratory Standards M23-T guidelines.

Cefotetan↗
PubMed1990

Antistaphylococcal activities of sparfloxacin (CI-978; AT-4140), ofloxacin, and ciprofloxacin.

The activity of sparfloxacin (CI-978; AT-4140) was compared with those of ofloxacin and ciprofloxacin against clinical isolates of Staphylococcus aureus and Staphylococcus epidermidis. All 10 ciprofloxacin-resistant staphylococci had reduced susceptibility to sparfloxacin and ofloxacin. Against 105 ciprofloxacin-susceptible strains of S. aureus, the sparfloxacin MIC for 90% of strains tested was at least fourfold lower than those of ciprofloxacin and ofloxacin, while against 104 ciprofloxacin-susceptible strains of S. epidermidis, the MIC of sparfloxacin for 90% of strains tested was twofold lower than that of ciprofloxacin and fourfold lower than that of ofloxacin. MBCs of sparfloxacin were less than or equal to 4 x MICs. The effects of inoculum size and pH variations, as well as the presence of serum, on the MICs of sparfloxacin were minimal. Subinhibitory concentrations of sparfloxacin did reduce adherence of S. epidermidis.

Anti-Infective Agents↗
PubMed1989

Evaluation of trehalose-mannitol broth for differentiation of Staphylococcus epidermidis from other coagulase-negative staphylococcal species.

Trehalose-mannitol agar and various broth formulations thereof were evaluated for the differentiation of Staphylococcus epidermidis from other common coagulase-negative staphylococcal species isolated from human blood cultures. While this differentiation was accurately made on trehalose-mannitol agar in 18 h, modification of the medium to a broth formulation containing 2% each trehalose and mannitol in 0.2 ml of purple broth base provided greater than 95% accuracy when a heavy inoculum was incubated on a rotary shaker for at least 4 h.

Culture Media↗
PubMed1988

In vitro activities of LY163892, cefaclor, and cefuroxime.

The in vitro activity of LY163892, a synthetic oral cephalosporin, was compared with those of cefaclor and cefuroxime against 1,193 clinical isolates. MIC ranges and MICs for 50 and 90% of isolates of the three cephalosporins were comparable. The activities of LY163892 and cefaclor were, however, highly inoculum dependent against beta-lactamase-positive Haemophilus influenzae and Staphylococcus aureus; that of cefuroxime was not. LY163892 and cefuroxime appeared stable in microdilution trays stored at 5 and -20 degrees C for 5 weeks, in contrast to cefaclor which remained stable for more than a week only at -5 degrees C.

Anti-Bacterial Agents↗
PubMed1988

Antibacterial activities of cefpodoxime, cefixime, and ceftriaxone.

Cefpodoxime, cefixime, and ceftriaxone inhibited Branhamella catarrhalis at less than or equal to 1 microgram/ml, beta-hemolytic streptococci at less than or equal to 0.25 microgram/ml, Neisseria meningitidis at less than or equal to 0.06 microgram/ml, and Haemophilus influenzae (other than beta-lactamase-negative, ampicillin-resistant isolates) at less than or equal to 0.12 microgram/ml. The MICs for 50% of isolates of the family Enterobacteriaceae other than Citrobacter freundii, Enterobacter aerogenes, and Enterobacter cloacae were less than or equal to 1 microgram/ml for all three cephalosporins. The MICs of each cephalosporin for 90% of staphylococci, enterococci, and Pseudomonas aeruginosa isolates were greater than 16 micrograms/ml. Inoculum effects were noted with cefpodoxime and cefixime with beta-lactamase-positive H. influenzae.

Bacteria↗
PubMed1988

Characterization of resistance phenotype and cephalosporin activity in oxacillin-resistant Staphylococcus aureus.

Forty isolates of methicillin-resistant Staphylococcus aureus were tested versus oxacillin at 30 and 35 degrees C with and without 2% NaCl supplementation of Mueller-Hinton broth and classified as having resistance that was low (MIC, less than or equal to 16 micrograms/ml) or high (MIC, greater than or equal to 32 micrograms/ml) and temperature or NaCl dependent. Only three isolates had low-grade resistance at both 30 and 35 degrees C; for two isolates the MICs at 35 degrees C were greater than or equal to 4 X the MICs at 30 degrees C. NaCl usually increased the MICs two- to fourfold. Efficiency of plating studies were performed on strains selected for their level of oxacillin resistance and according to temperature-related difference in MICs. Most strains appeared to represent the heterogeneous resistance phenotype. Cefamandole MICs were little affected by temperature but increased with NaCl. With three exceptions, cefamandole MCBs were less than or equal to 4 X MICs. For only six isolates were cefuroxime MICs less than or equal to 16 micrograms/ml. Four strains that were susceptible to both cefuroxime and cefamandole were selected for time-killing curve studies at inocula of 10(7) CFU/ml. At 8 X MIC, cefuroxime failed to reduce the concentration of any strain by greater than or equal to 3 X log10 CFU/ml. Killing of greater than or equal to 3 X log10 CFU/ml was achieved by cefamandole at 4X and 8 X MIC in one strain, at 8 X MIC only in two strains, and by neither 4 X nor 8 X MIC in one strain. Within therapeutically attainable blood levels, cefuroxime is essentially inactive and cefamandole is variably bactericidal against oxacillin-resistant s. aureus.

Analysis of Variance↗
PubMed1987

Rapid identification of Staphylococcus epidermidis.

A panel of Minitek sugar disks, consisting of trehalose, mannitol, xylose, and sucrose, was evaluated for its ability to identify blood culture isolates of Staphylococcus epidermidis (SE). Using a heavy suspension of organism in Mueller-Hinton broth, 50 microL was pipetted onto each disk in wells of a flat-bottomed microtiter tray. The tray was covered, incubated in a moist chamber in non-CO2 at 35 degrees C, and examined after 5 and 24 hours. A color change of yellow or orange was positive; no color change (red) was negative. Expected reactions for SE were as follows: negative trehalose, mannitol, and xylose; positive, sucrose. On evaluation of 227 coagulase-negative staphylococci (CNS) at 5 and 24 hours, the panel had a sensitivity of 94 and 96%, specificity of 92 and 89%, predictive value of positive tests of 97 and 96%, and predictive value of negative tests of 84 and 87%. This panel offered an inexpensive and convenient method for differentiating SE from the other CNS in five hours.

Alkaline Phosphatase↗
PubMed1987

Relationship between cefamandole and cefuroxime activity against oxacillin-resistant Staphylococcus epidermidis and oxacillin resistance phenotype.

The activity of cefamandole and cefuroxime against oxacillin-resistant staphylococcus epidermidis was studied in vitro to determine whether there was any relationship between oxacillin resistance phenotypes and cephalosporin activity. Oxacillin resistance phenotypes were determined by efficiency-of-plating studies on Mueller-Hinton agar containing oxacillin, with and without NaCl, and incubated at 30 and 35 degrees C. On the basis of MIC and MBC determinations, cefamandole was more active than cefuroxime against oxacillin-resistant S. epidermidis. Although temperature had minimal effect on the activity of either cefamandole or cefuroxime, NaCl significantly decreased the activity of cefuroxime but not of cefamandole. Neither cephalosporin consistently produced greater than or equal to 99.9% bactericidal activity within 24 h in timed killing-curve studies. No consistent relationship was observed between cefamandole or cefuroxime activity and oxacillin resistance phenotype.

Cefamandole↗
PubMed1986

Antistaphylococcal activity of a cyclic peptide, LY146032, and vancomycin.

The inhibitory and bactericidal activities of a novel cyclic peptide antibiotic, LY146032, and vancomycin against oxacillin-susceptible and oxacillin-resistant staphylococci were compared. The MICs for 90% of strains were two- to fourfold higher for vancomycin than for LY146032. MBC/MIC ratios for all strains were less than or equal to 2. In killing rate studies with four strains of staphylococci, there was no detectable growth in the presence of 4X the MIC of either LY146032 or vancomycin after 24 h of incubation.

Anti-Bacterial Agents↗
PubMed1986

Detection of methicillin-resistant Staphylococcus epidermidis.

To determine whether methods suggested for detecting methicillin-resistant Staphylococcus aureus apply equally to methicillin-resistant Staphylococcus epidermidis, 135 S. epidermidis isolates were tested by the Vitek AMS gram-positive susceptibility card (Vitek Systems, Inc., Hazelwood, Mo.) and by modifications of agar screen, disk diffusion, and microdilution methods. Modifications included 24- versus 48-h incubation, unsupplemented versus 2% NaCl-supplemented broth, and standard versus direct inoculum. At 24 h, the highest number of resistant strains, 59, was detected by oxacillin (1 microgram) disk diffusion. At 48 h, three additional strains were judged resistant. With one exception, results for oxacillin disk diffusion and agar screen were equivalent at 24 and 48 h. Vitek detected 50 resistant strains. Significantly fewer resistant strains were detected at 24 h by methicillin disk diffusion (5 micrograms) and methicillin microdilution with 2% NaCl. For oxacillin microdilution, neither 2% NaCl supplementation nor the method of inoculum preparation significantly affected the results. Oxacillin microdilution with cation- rather than non-cation-supplemented broth detected significantly fewer (n = 33) resistant strains at 24 h; 51 were resistant at 48 h. To detect methicillin-resistant S. epidermidis, a direct inoculum with either 24-h oxacillin disk diffusion and reincubation of intermediate strains for an additional 24 h or 24-h oxacillin agar screen and reincubation of strains with no growth for a total of 48 h is recommended.

Humans↗
PubMedDate not supplied

Activity of ticarcillin/clavulanate and piperacillin/tazobactam (YTR 830; CL-298,741) against clinical isolates and against mutants derepressed for class I beta-lactamase.

Piperacillin/tazobactam (YTR 830; CL-298,741) was tested against fresh and stock clinical isolates of Gram-negative bacilli, as well as against Gram-negative bacilli that had stably derepressed Class I beta-lactamases or that were hyperproductive of non-Class I beta-lactamases. Of 63 clinical isolates of the Enterobacteriaceae with ticarcillin (plus clavulanate) minimum inhibitory concentrations (MICs) of greater than or equal to 128 micrograms/ml, 16 had piperacillin/tazobactam MICs of less than or equal to 16/2 micrograms/ml. Of 48 clinical isolates of Pseudomonas spp. with ticarcillin (plus clavulanate) MICs of greater than or equal to 128 micrograms/ml, 35 had piperacillin/tazobactam MICs of less than or equal to 64/8 micrograms/ml. Tazobactam generally reduced piperacillin MICs by two- to greater than or equal to eightfold against stably derepressed mutants for Class I beta-lactamases.

Bacteria↗
PubMedDate not supplied

Comparative in vitro activity of cefoperazone and various combinations of cefoperazone/sulbactam.

Cefoperazone with 2 and 4 micrograms/ml of sulbactam and in a 2:1 ratio was tested against 1258 clinical isolates of Gram-positive and Gram-negative bacteria, as well as against Gram-negative bacilli that had stably derepressed Type I beta-lactamase or that were hyperproductive of non-Type I beta-lactamases. The 2:1 cefoperazone/sulbactam combination was the most potent combination tested. With this combination cefoperazone minimum inhibitory concentrations (MICs) of 27 of 40 (67%) of the clinical isolates of Pseudomonas species and 64 of 67 (95%) of clinical isolates of the Enterobacteriaceae were reduced from greater than or equal to 64 micrograms/ml by at least two-fold. In contrast, cefoperazone MICs of greater than or equal to 64 micrograms/ml remained unchanged for 26 (65%) and 24 (60%) of Pseudomonas species and 35 (52%) and 30 (45%) of the Enterobacteriaceae in the presence of 2 and 4 micrograms/ml of sulbactam, respectively. Cefoperazone/sulbactam in the 2:1 ratio was also the most active combination against the mutants derepressed for Type I beta-lactamase. Although the 2:1 combination of cefoperazone/sulbactam had the greatest potency in vitro, it remains to be seen whether this combination is predictive of clinical outcome from treatment of cefoperazone-resistant Gram-negative bacilli with cefoperazone/sulbactam.

Bacteria↗
PubMedDate not supplied

Development of Neisseria gonorrhoeae in vitro susceptibility test methods for cefixime including quality control guidelines.

Cefixime was tested in a multilaboratory study to establish susceptibility testing interpretive criteria and quality control (QC) guidelines for Neisseria gonorrhoeae. Interpretive criteria were established by using triplicate testing of 102 representative gonococcal strains. Only a susceptible category was proposed for cefixime (greater than or equal to 31 mm and less than or equal to 0.25 micrograms/ml) because of very rare, resistant isolates. QC ranges [N. gonorrhoeae American Type Culture Collection (ATCC) 49226] were established using multiple GC agar lots, three disk lots, and a number of test replicates consistent with the National Committee for Clinical Laboratory Standards (NCCLS) M23-T guidelines. Cefixime was stable in GC agar medium for at least 21 days when stored at 2 degrees-5 degrees C. Oral third-generation cephalosporins, such as cefixime, appear to represent potentially useful clinical alternatives to parenteral drugs of the same class for single-dose therapy of gonorrhea.

Cefixime↗
PubMedDate not supplied

Accuracy of microdilution and the AutoMicrobic System in detection of beta-lactam resistance in gram-negative bacterial mutants with derepressed beta-lactamase.

Microdilution and the AutoMicrobic System (AMS) were compared with macrodilution for accuracy in detecting beta-lactam resistance in 16 isogenic pairs of gram-negative wild-type bacterial strains and mutant strains with derepressed class I beta-lactamase; an additional 12 gram-negative derepressed mutants were also tested. Of a total of 352 organism-beta-lactam combinations resulting in 840 determinations of minimum inhibitory concentration, the overall rates of very major discrepancy were 3% between macrodilution and microdilution and 2% between macrodilution and AMS. The corresponding rates of very major discrepancies with the derepressed mutants were both 2.7%. All but three of the wild-type strains were susceptible to all beta-lactam drugs tested but cefoxitin, while nearly 90% of derepressed mutants were resistant to these antibiotics. When careful attention was given to inoculum size and incubation time, microdilution and the AMS yielded results comparable to those obtained by macrodilution.

Anti-Bacterial Agents↗
PubMedDate not supplied

Comparative activity of newer antibiotics against gram-negative bacilli.

The in vitro activities of cefoperazone, cefotaxime, ceftriaxone, ceftazidime, azlocillin, mezlocillin, piperacillin, ticarcillin/clavulanate, aztreonam, imipenem, and ciprofloxacin were concurrently determined against over 1,000 isolates of gram-negative bacilli from clinical specimens of patients at the Cleveland Clinic. Cephalosporins, penicillins, and aztreonam were active against species of Enterobacteriaceae other than Citrobacter freundii, Enterobacter aerogenes, and Enterobacter cloacae. Ceftazidime was the most active cephalosporin against Pseudomonas aeruginosa. Against the Enterobacteriaceae, the rank order of activity of penicillins was ticarcillin/clavulanate greater than piperacillin greater than mezlocillin greater than azlocillin. Against P. aeruginosa, the rank order of activity of penicillins was piperacillin greater than ticarcillin/clavulanate greater than azlocillin greater than mezlocillin. Aztreonam was less active v P. aeruginosa than ceftazidime, cefoperazone, or piperacillin. The most active antimicrobials against all isolates tested were imipenem and ciprofloxacin.

Aztreonam↗