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Biomedical subjects

P C Fuchs

Publications and source records attributed to P C Fuchs.

At least 37 records · Page 2Linked to original sources
PubMed2001

Influence of variations in test methods on susceptibility of Haemophilus influenzae to ampicillin, azithromycin, clarithromycin, and telithromycin.

The National Committee for Clinical Laboratory Standards standard broth microdilution method for testing the susceptibility of Haemophilus influenzae to ampicillin, azithromycin, clarithromycin, and telithromycin was evaluated by altering one variable at a time. Variables that were tested included age of colony for inoculum preparation, inoculum density, test medium, incubation atmosphere, and incubation time. For the macrolide, azalide, and ketolide agents, incubation in 5 to 7% CO(2) most significantly affected the MICs, producing nearly twofold increases for clarithromycin and telithromycin and a greater than threefold increase for azithromycin. For ampicillin, a 10-fold increase in inoculum density increased the geometric mean MICs for beta-lactamase-negative strains from 1. 50 to 2.45 microg/ml. In addition, 206 H. influenzae strains were tested for their susceptibilities to the same drugs by the broth microdilution tests in two media, as well as by agar dilution tests, disk diffusion tests, and Etests, on six different agar media. The three standard methods with Haemophilus test medium (HTM) compared favorably with each other except for a high minor discrepancy rate (27%) by the disk diffusion test with ampicillin and clarithromycin. Agar dilution test MICs on the five comparative media were generally higher than those on HTM agar but were only rarely more than one twofold concentration higher. Etest MICs of azithromycin and telithromycin were more than twofold higher than agar dilution and broth microdilution MICs on HTM; ampicillin Etest MICs were nearly twofold lower. The use of media other than HTM agar appears to have a minimal effect on susceptibility test results for the ketolide, azalide, or macrolide drugs that we tested against H. influenzae.

Ampicillin↗
PubMed2000

Susceptibility of Streptococcus pneumoniae and Haemophilus influenzae to cefditoren, and provisional interpretive criteria.

In vitro cefditoren antimicrobial activity was tested by broth microdilution and disk diffusion methods against 300 Streptococcus pneumoniae and 299 Haemophilus influenzae isolates. MICs were also determined for three comparison drugs. The MICs of cefditoren were very comparable to those of cefotaxime against both species. If penicillin-resistant pneumococci are to be considered not susceptible to cefditoren, the tentative MIC breakpoints for cefditoren of < or = 0.25 microg/ml for susceptible and > or 1.0 microg/ml for resistant could be selected. With these breakpoints, all penicillin-susceptible pneumococci were cefditoren-susceptible, as were 85% of penicillin-intermediate strains. Provisional zone diameter breakpoints would be > or = 26 mm for susceptible and < or = 20 mm for resistant. If penicillin-resistant pneumococcal infections are shown to clinically respond to cefditoren therapy, then a susceptible MIC breakpoint of < or = 1.0 microg/ml would be appropriate, with a corresponding zone diameter breakpoint of > or = 21 mm. A susceptible MIC breakpoint of < or = 0.5 or < or = 1.0 microg/ml is appropriate for H. influenzae, but lack of correlation between cefditoren MICs and disk diffusion zone diameters when testing H. influenzae leads us to make no recommendations at this time regarding cefditoren disk tests for H. influenzae.

Ampicillin↗
PubMed2000

Daptomycin susceptibility tests: interpretive criteria, quality control, and effect of calcium on in vitro tests.

Daptomycin MICs were determined for 844 Gram-positive bacteria in three concentrations of Ca(++) and compared with the MICs of vancomycin and teicoplanin. Daptomycin was twofold to fourfold more active against most species when tested in 50 microg/ml of Ca(++) than in 25 microg/ml. In 50 microg/ml of Ca(++) daptomycin was more active against methicillin-resistant staphylococci and vancomycin-resistant enterococci than teicoplanin or vancomycin; 100% of these isolates were susceptible to < or =2.0 microg/ml of daptomycin. Different lots of Mueller-Hinton agar were variable in Ca(++) content, and daptomycin disk diffusion zone diameters were affected, i.e., zones were 1 to 15 mm smaller on one lot of agar with only 6 microg/ml of Ca(++) compared to another lot with 28 microg/ml. The previously proposed daptomycin interpretive breakpoints performed satisfactorily when MICs were determined in Mueller-Hinton broth with 50 microg/ml of Ca(++) and when the agar gave appropriate zones with quality control strains. To define those control limits, replicate tests with four quality control strains were performed in ten laboratories using broth microdilution tests (with Ca(++) supplemented broth) and disk diffusion tests on Mueller-Hinton agar without cation adjustments.

Anti-Bacterial Agents↗
PubMed2000

In vitro activity of gemifloxacin against contemporary clinical bacterial isolates from eleven North American medical centers, and assessment of disk diffusion test interpretive criteria.

A total of 5499 contemporary clinical bacterial isolates were tested for susceptibility to gemifloxacin and four comparison agents by the broth microdilution method. Gemifloxacin activity against Enterobacteriaceae was generally comparable to that of ciprofloxacin and trovafloxacin, but because the gemifloxacin susceptible MIC breakpoint is lower, the percent susceptible to gemifloxacin was less than that to the other quinolones for some species. All agents were less active against Pseudomonas spp. Gemifloxacin was the most active agent tested against Gram-positive species, though Corynebacterium jeikeium and vancomycin-resistant enterococci were uniformly resistant to all agents tested. With staphylococci, a bimodal distribution of gemifloxacin MICs corresponded with susceptibility or resistance to ciprofloxacin. The significance of ciprofloxacin-resistant staphylococci that have susceptible gemifloxacin MICs is not known at this time. Disk diffusion tests were performed simultaneously with gemifloxacin and trovafloxacin as a control drug. Gemifloxacin MIC-zone diameter scattergrams indicated that interpretive discrepancy rates based on previously proposed criteria when using < or = 0.5 microg/ml as the susceptible MIC breakpoint was within acceptable limits. However, with the currently proposed MIC breakpoint of < or = 0.25 microg/ml, tentative zone diameter breakpoints of > or = 22 mm for susceptible, 19-21 mm for intermediate and < or = 18 mm for resistant are proposed.

Anti-Infective Agents↗
PubMed2000

Bactericidal activity of quinupristin-dalfopristin against Staphylococcus aureus: clindamycin susceptibility as a surrogate indicator.

Of 516 Staphylococcus aureus strains tested, 97.1% were susceptible to quinupristin-dalfopristin, which was bactericidal for 22 (56%) of the 39 strains tested, comparable to vancomycin. All 17 clindamycin and macrolide-resistant strains were inhibited but not killed by quinupristin-dalfopristin, whereas all 22 clindamycin-susceptible strains (5 were macrolide resistant) were killed.

Anti-Bacterial Agents↗
PubMed1999

Antibacterial activity of moxifloxacin (Bay 12-8039) against aerobic clinical isolates, and provisional criteria for disk susceptibility tests.

Moxifloxacin (Bay 12-8039), ciprofloxacin, and levofloxacin were compared in vitro against 1074 clinical isolates gathered from different medical centers throughout North America during the winter months of 1997. Moxifloxacin E tests and broth microdilution tests gave comparable results. Moxifloxacin was particularly potent against respiratory pathogens such as Haemophilus influenzae and Streptococcus pneumoniae. Ciprofloxacin was the most potent study drug against the family of Enterobacteriaceae and Pseudomonas spp. For tests of 5 microg moxifloxacin disks, zone size criteria of < or = 17 mm for resistant (MIC > or = 8 microg/ml) and > or = 21 mm for susceptible (MIC < or = 2 microg/ml) are provisionally proposed for use while clinical trials are under way.

Anti-Infective Agents↗
PubMed1999

In vitro activity of trovafloxacin against ciprofloxacin-susceptible and -resistant clinical bacterial isolates and assessment of the trovafloxacin disk test.

A total of 4241 consecutive clinical bacterial isolates from 10 North American medical centers were tested for susceptibility to trovafloxacin. Trovafloxacin was significantly more active than ciprofloxacin against Gram-positive bacteria, Acinetobacter spp., and Stenotrophomonas maltophilia, and resistance to trovafloxacin occurred in these groups only among isolates with high-level resistance (MIC > or = 16 micrograms/mL) to ciprofloxacin. With other species, the two drugs had comparable activity. Concerns about staphylococci and Pseudomonas aeruginosa with trovafloxacin MICs of 2.0 micrograms/mL (the upper end of the susceptible category) are discussed. Results of trovafloxacin disk diffusion test on more than 3200 nonfastidious isolates supported the FDA-approved zone size interpretive criteria when the MIC breakpoint of < or = 2.0 micrograms/mL is used to define the trovafloxacin-susceptible category.

Anti-Infective Agents↗
PubMed1999

A new technique for quantitative bacterial assessment on burn wounds by modified dermabrasion.

Bacterial colonization and invasive bacterial infection is still one of the major problems in the treatment of burn victims. The standard procedures of bacterial monitoring of the burn would are i) swab-culture which is non-invasive but detects bacteria at the very surface and ii) biopsy-culture which gives a more complete view but has the disadvantage of being invasive. Therefore we developed a new technique for examination of microbial colonization of the wound surface. Dermabrasion of the upper layers of the wound was performed using a small rotating carbon-steel disc of defined roughness. The tissue samples obtained were analysed for bacterial growth in different culture media. Results were qualitatively and quantitatively compared with those of standard techniques performed in parallel. Our results show that this new technique is superior to the swab culture in identifying different bacterial species. The results can be compared with the biopsy technique, but has the advantage of being less invasive.

Adolescent↗
PubMed1999

Fosfomycin tromethamine susceptibility of outpatient urine isolates of Escherichia coli and Enterococcus faecalis from ten North American medical centres by three methods.

One hundred percent of 1097 Escherichia coli and 97.5% of 157 Enterococcus faecalis isolates from outpatient urine specimens at ten North American medical centres were susceptible to fosfomycin tromethamine. The Etest MICs correlated well with those of agar dilution. Disc diffusion zone diameters correlated well with MICs and supported the previously proposed zone diameter breakpoints for fosfomycin.

Anti-Bacterial Agents↗
PubMed1999

In-vitro antimicrobial activity of a carbapenem, MK-0826 (L-749,345) and provisional interpretive criteria for disc tests.

The in-vitro activity of MK-0826, a new oral carbapenem, was compared with that of imipenem by broth microdilution susceptibility tests against 545 bacterial isolates. MK-0826 had significantly greater activity against Enterobacteriaceae and poorer activity against Pseudomonas aeruginosa and many gram-positive species. MK-0826 disc diffusion tests were also performed according to the NCCLS procedure and tentative interpretive criteria were determined for possible susceptible MIC breakpoints of < or = 4.0 and < or = 2.0 mg/L.

Bacteria, Aerobic↗
PubMed1999

In vitro activities of SCH27899 alone and in combination with 17 other antimicrobial agents.

SCH27899, an everninomicin antibiotic, was tested for its in vitro activity against 718 bacterial isolates representing 27 species. The Enterobacteriaceae and nonenteric gram-negative bacilli were resistant to > or = 8.0 microg/ml, but all others were inhibited by < or = 1.0 microg/ml. When tested in combination with 17 other antimicrobial agents against 110 strains, SCH27899 demonstrated no significant antagonism or synergy. Consequently, combination therapy is not contraindicated.

Aminoglycosides↗
PubMed1998

Multicenter survey of the in vitro activity of four expanded-spectrum beta-lactams against consecutive contemporary clinical isolates.

A survey of the in vitro susceptibility of consecutive clinical bacterial isolates to cefotaxime, ceftazidime, cefpodoxime, and aztreonam was conducted at 10 North American medical centers during the first quarter of 1997. All four drugs had good activity against Enterobacteriaceae and fastidious Gram-negative bacteria and poor activity against enterococci and methicillin-resistant staphylococci. No significant trends in susceptibility to cefotaxime or ceftazidime were observed when compared with a previous similar survey. The use of cefpodoxime MIC > 2.0 micrograms/mL as a marker for extended-spectrum beta-lactamase production by Escherichia coli and Klebsiella spp. had good sensitivity, but the specificity was very poor for E. coli. Thus, at least for E. coli, this screening test seems to be of questionable value unless used to indicate the need for additional tests such as clavulanic acid inhibition. Disk diffusion zone diameters correlated well with the MICs for all four drugs and support the current interpretive criteria.

Anti-Bacterial Agents↗
PubMed1998

Susceptibility to RPR 106,972, quinupristin/dalfopristin and erythromycin among recent clinical isolates of enterococci, staphylococci and streptococci from North American medical centres.

An orally administered streptogramin (RPR 106,972) and a parenteral streptogramin (quinupristin/dalfopristin) were evaluated against a collection of 2481 recent clinical isolates of gram-positive cocci. The isolates were gathered from ten North American medical centres during the winter months of 1996-1997. In spite of minor differences, both streptogramins had essentially identical spectra of activity which included many erythromycin-resistant isolates. Previously proposed interpretative criteria for quinupristin/dalfopristin disc diffusion susceptibility tests were confirmed.

Academic Medical Centers↗
PubMed1998

PMX-622 (polymyxin B-dextran 70) does not alter in vitro activities of 11 antimicrobial agents.

Because of its capacity to neutralize the lethality of gram-negative bacterial endotoxic lipopolysaccharides, PMX-622 (polymyxin B bound to dextran 70) is being developed for possible adjunctive therapy of gram-negative sepsis. In this study, it was determined that the in vitro antimicrobial activity of PMX-622 was minimal and that it does not interfere with the in vitro antimicrobial activity of 11 antibiotics commonly used to treat gram-negative infections.

Anti-Bacterial Agents↗
PubMed1998

Antipneumococcal activities of a ketolide (HMR 3647), a streptogramin (quinupristin-dalfopristin), a macrolide (erythromycin), and a lincosamide (clindamycin).

Four different compounds belonging to the macrolide-lincosamide-streptogramin B (MLSb) class of antimicrobial agents were tested against 611 Streptococcus pneumoniae strains. The ketolide (HMR 3647, previously RU66647) and the streptogramin (quinupristin-dalfopristin) were both active against pneumococci with high-level MLSb resistance (clindamycin-resistant strains) as well as those with low-level macrolide resistance (clindamycin-susceptible strains).

Anti-Bacterial Agents↗
PubMed1998

In vitro antimicrobial activity of MSI-78, a magainin analog.

MSI-78 is a cationic peptide with broad-spectrum antimicrobial activity and is being developed as a topical agent. We compared the in vitro activity of MSI-78 with those of ofloxacin and other antibiotics against fresh clinical isolates. Based on MIC distribution statistics, strains for which the MSI-78 MIC was < or = 64 micro/ml were assumed to be susceptible for purposes of this report. Of 411 aerobic isolates tested, 91% were susceptible to MSI-78, compared to 91% for ofloxacin and 92% for ciprofloxacin. Only enterococci consistently required > or = 64 microg of MSI-78/ml for inhibition. MSI-78 demonstrated bactericidal activity equivalent to that of ofloxacin. Of 61 anaerobes, 97% were susceptible to MSI-78. Of 10 isolates of Candida albicans, 3 were inhibited by MSI-78 at 24 h. Further studies of this compound appear to be warranted.

Anti-Infective Agents↗