Piperacillin susceptibility tests by the single-disk agar diffusion technique

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Cefsulodin (formerly SCE-129) is a cephalosporin which has in vitro activity against Pseudomonas aeruginosa, Staphylococcus aureus, and most other gram-positive cocci (4, 7-9). However, it has very little activity against the enterococci and members of the Enterobacteriaceae (7-9). Such a limited-spectrum antimicrobial agent may be advantageous when treating bacterial infections of known etiology.In the present report we compare cefsulodin with four penicillins with antipseudomonal activity (carbenicillin, ticarcillin, mezlocillin, and piperacillin). For this purpose, 778

supporting

confidence: 78%

Cefsulodin: antibacterial activity and tentative interpretive zone standards for the disk susceptibility test

Barry¹,

Jones²,

Thornsberry³

1981

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“…The pharmacokinetics of mezlocillin appear to be well established (2,3,8,13). We report herein attempts to confirm a recent report on the interpretive zone standards for this semisynthetic penicillin with commercially prepared disks and the disk diffusion susceptibility testing technique (11,15 (1,6). Disk diffusion tests on the same isolates were performed, utilizing the latest method recommended by the National Committee for Clinical Laboratory Standards (NCCLS) (11).…”

supporting

confidence: 63%

Mezlocillin: tentative interpretive standards for disk diffusion susceptibility testing

Fuchs¹,

Barry²,

Thornsberry³

et al. 1981

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The susceptibility of 447 clinical bacterial isolates to mezlocillin and carbenicillin was tested by standardized agar disk diffusion and reference broth microdilution methods. Tentative interpretive criteria for disk susceptibility testing by using 75-,ug mezlocillin disks are proposed: susceptible, 516 mm; indeterminate, 13 to 15 mm; and resistant, c12 mm. These would be applicable to both Pseudomonas species and the Enterobacteriaceae, but not to Staphylococcus aureus. For S. aureus, the breakpoints for susceptible, 529 mm, and resistant, c28 mm, hold for mezlocillin as well as for the other penicillinase-susceptible penicilhins.Mezlocillin is a new ureidopenicillin with a well-documented broad spectrum of in vitro antimicrobial activity (4,5,17,18 Organisms. The 447 selected recent clinical bacterial isolates tested are listed in Table 1. Of the isolates, 55% were tested by both methods at the Centers for Disease Control, Atlanta, Ga., and 55% were tested at the University of California, Davis, Medical Center, Sacramento, Calif. Ten percent of the isolates were tested at both institutions as a quality control of the methods, in addition to the strains recommended by the NCCLS, viz., Eacherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, and Pseudomonas aeruginosa ATCC 25853. RESULTSThe distribution of MICs of mezlocillin and carbenicillin for the 447 selected clinical isolates is shown in Table 1. The differences in activity against the Enterobacteriaceae species were not great for most species. Exceptions to this were Citrobacter diversus and Klebsiella pneumoniae, which were eight times more susceptible to mezlocillin than to carbenicillin. E. coli was about twice as susceptible to mezlocillin. The 83 P. aeruginosa strains tested showed slightly less than one dilution step greater susceptibility to mezlocillin than to carbenicillin. This difference favoring mezlocillin was up to eightfold greater for other Pseudomonas species. Among the gram-positive isolates, mezlocillin had eight times greater activity than did carbenicillin against Streptococcus faecalis. Against penicillinase-producing S. aureus, carbenicillin was the more active drug, but non-beta-lactamase-producing strains were equally susceptible (MIC c 1 ug/ml) to both drugs. on May 7, 2018 by guest http://aac.asm.org/ Downloaded from

“…Tests with 463 selected bacterial isolates were performed at the Center for Disease Control, Atlanta, Ga., and at the University of California (Davis) Medical Center, Sacramento, Calif., as previously described (2,5 Class concept. Before we proceeded with the development of a disk diffusion susceptibility testing procedure, it seemed appropriate to determine whether tests with an established cephalosporin could predict susceptibility or resistance to moxalactam.…”

Section: Methodsmentioning

confidence: 99%

Tentative interpretive standards for disk susceptibility tests with moxalactam (LY127935)

Barry¹,

Thornsberry²,

Jones³

et al. 1980

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Moxalactam (LY127935; 6059-S) is a new beta-lactam antibiotic. We propose tentative zone standards for agar diffusion susceptibility tests with 30-,ug strains with minimal inhibitory concentrations of 8 ,ug/ml from strains requiring <2 ,ug/ml for inhibition, because the regression line became parabolic at concentrations of 2 pg/ml and below. However, the disk tests were satisfactory for categorizing isolates into the above-described susceptible, moderately susceptible (intermediate), and resistant categories.Moxalactam (LY127935; 6059-S) is a new beta-lactam antibacterial agent (a 1-oxa betalactam) with a broad spectrum of activity (3, 4, 4a, 8-10