Skip to main content
NCBI home page
Antimicrobial Agents and Chemotherapy logoLink to Antimicrobial Agents and Chemotherapy
. 1975 Aug;8(2):172–186. doi: 10.1128/aac.8.2.172

Disk Diffusion and Serial Dilution Tests of Susceptibility of Some Pathogenic Gram-Negative Bacilli and Enterococci to Carbenicillin and Ampicillin

Carol Garner †, Bernard Rosner †, Maxwell Finland *
PMCID: PMC429285  PMID: 810078

Abstract

Tests for susceptibility to ampicillin and carbenicillin were performed with 35 strains each of Klebsiella, Enterobacter, Serratia, and Proteus, 71 strains of Pseudomonas aeruginosa, and 68 strains of enterococci by serial dilution and disk-diffusion tests employing 10−3 dilutions of overnight cultures as inocula for both. Commercial 10-μg ampicillin and 50- and 100-μg carbenicillin disks, and freshly prepared 10-, 50-, and 75-μg ampicillin and 10- and 50-μg carbenicillin disks were used. Results were displayed as cumulative distribution curves for both minimal inhibitory concentrations and zone diameters, and as scattergrams for correlating them. Differences in susceptibility to the two antibiotics were small for Klebsiella, Enterobacter, and Serratia and large for the others. The freshly prepared and commercial disks of the same content gave comparable zones. There was good correlation of zone diameter with each disk and the minimal inhibitory concentration. Among the ampicillin disks tested, none was useful for Pseudomonas; with the other species, the 10-μg disk, as well as those with higher ampicillin content, could discriminate susceptible from resistant strains. However, only the 75-μg disk selected some Klebsiella strains susceptible to high concentrations. The 50- and 100-μg carbenicillin disks were equally discriminating for most strains, but the higher concentration was more selective for Klebsiella. The 10-μg carbenicillin disk was as effective as the 50- and 100-μg disks for discriminating among Enterobacter, Serratia, Pseudomonas, and Proteus, but not for Klebsiella or enterococci. The 10−3 inoculum gave zone sizes considerably larger than those reported by other workers who used the standard Kirby-Bauer method.

Full text

PDF
172

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Adler J. L., Burke J. P., Martin D. F., Finland M. Proteus infections in a general hospital. I. Biochemical characteristics and antibiotic susceptibility of the organisms. With special reference to proticine typing and the Dienes phenomenon. Ann Intern Med. 1971 Oct;75(4):517–530. doi: 10.7326/0003-4819-75-4-517. [DOI] [PubMed] [Google Scholar]
  2. Anderson J. D., Warner M., Forshaw H. L. Studies on the effect of amoxycillin and ampicillin on Enterobacteriaceae in an experimental model of urinary infection. J Antimicrob Chemother. 1975 Jun;1(2):197–204. doi: 10.1093/jac/1.2.197. [DOI] [PubMed] [Google Scholar]
  3. Barry A. L., Effinger L. J. Evaluation of two standardized disk methods for testing antimicrobial susceptibility of Pseudomonas aeruginosa and of the Enterobacteriaceae. Antimicrob Agents Chemother. 1974 Oct;6(4):452–459. doi: 10.1128/aac.6.4.452. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Bauer A. W., Kirby W. M., Sherris J. C., Turck M. Antibiotic susceptibility testing by a standardized single disk method. Am J Clin Pathol. 1966 Apr;45(4):493–496. [PubMed] [Google Scholar]
  5. Eickhoff T. C., Steinhauer B. W., Finland M. The Klebsiella-Enterobacter-Serratia division. Biochemical and serologic characteristics and susceptibility to antibiotics. Ann Intern Med. 1966 Dec;65(6):1163–1179. doi: 10.7326/0003-4819-65-6-1163. [DOI] [PubMed] [Google Scholar]
  6. Klastersky J., Daneau D., Swings G., Weerts D. Antibacterial activity in serum and urine as a therapeutic guide in bacterial infections. J Infect Dis. 1974 Feb;129(2):187–193. doi: 10.1093/infdis/129.2.187. [DOI] [PubMed] [Google Scholar]
  7. Matsen J. M., Lund M. E., Brooker D. C. Comparison and evaluation of carbenicillin disks in diffusion susceptibility testing. Antimicrob Agents Chemother. 1974 Jun;5(6):599–606. doi: 10.1128/aac.5.6.599. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Toala P., McDonald A., Wilcox C., Finland M. Susceptibility of group D streptococcus (enterococcus) to 21 antibiotics in vitro, with special reference to species differences. Am J Med Sci. 1969 Dec;258(6):416–430. doi: 10.1097/00000441-196912000-00006. [DOI] [PubMed] [Google Scholar]
  9. Washington J. A., 2nd, Hall M. M., Fausch C. J., Brackin K. L. In vitro activity of carbenicillin against Pseudomonas using the disc diffusion method. Mayo Clin Proc. 1973 Oct;48(10):718–721. [PubMed] [Google Scholar]

Articles from Antimicrobial Agents and Chemotherapy are provided here courtesy of American Society for Microbiology (ASM)

RESOURCES