Examination of Pseudomonas aeruginosa-gentamicin discrepancies encountered in an Autobac I-disk diffusion comparison

J. B. Mayo, T. E. Kiehn, Brian Wong, E. M. Bernard, D. Armstrong

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Seven Pseudomonas aeruginosa strains found to be susceptible to gentamicin by the Autobac I system and resistant by the Bauer-Kirby disk diffusion method were tested for the presence of mixed populations of cells. Double zones of inhibition randomly appeared on gentamicin disk diffusion plates, and susceptible and resistant subpopulations were isolated from these plates. Growth kinetic studies of separated strains and mixed subpopulations indicated that the susceptible organisms grew rapidly and were read as susceptible at 5 h with the Autobac I system. Resistant organisms entered a sustained lag phase and did not achieve sufficient turbidity to be read as resistant with the Autobac I system before 6 h. Thus, a false reading of susceptible could be obtained with the Autobac I system, depending on the ratio of susceptible organisms to resistant organisms selected for testing. A mixed susceptible and resistant population could be recognized by extending the incubation time of the Autobac I cuvette or by using other susceptibility methods to test isolates with light scattering indexes of <1.0.

Original languageEnglish (US)
Pages (from-to)412-415
Number of pages4
JournalAntimicrobial Agents and Chemotherapy
Volume21
Issue number3
StatePublished - 1982
Externally publishedYes

Fingerprint

Gentamicins
Pseudomonas aeruginosa
Disk Diffusion Antimicrobial Tests
Population
Reading
Light
Growth

ASJC Scopus subject areas

  • Pharmacology (medical)

Cite this

Examination of Pseudomonas aeruginosa-gentamicin discrepancies encountered in an Autobac I-disk diffusion comparison. / Mayo, J. B.; Kiehn, T. E.; Wong, Brian; Bernard, E. M.; Armstrong, D.

In: Antimicrobial Agents and Chemotherapy, Vol. 21, No. 3, 1982, p. 412-415.

Research output: Contribution to journalArticle

Mayo, J. B. ; Kiehn, T. E. ; Wong, Brian ; Bernard, E. M. ; Armstrong, D. / Examination of Pseudomonas aeruginosa-gentamicin discrepancies encountered in an Autobac I-disk diffusion comparison. In: Antimicrobial Agents and Chemotherapy. 1982 ; Vol. 21, No. 3. pp. 412-415.
@article{19a0cc80eb474fc38710dc5264d80565,
title = "Examination of Pseudomonas aeruginosa-gentamicin discrepancies encountered in an Autobac I-disk diffusion comparison",
abstract = "Seven Pseudomonas aeruginosa strains found to be susceptible to gentamicin by the Autobac I system and resistant by the Bauer-Kirby disk diffusion method were tested for the presence of mixed populations of cells. Double zones of inhibition randomly appeared on gentamicin disk diffusion plates, and susceptible and resistant subpopulations were isolated from these plates. Growth kinetic studies of separated strains and mixed subpopulations indicated that the susceptible organisms grew rapidly and were read as susceptible at 5 h with the Autobac I system. Resistant organisms entered a sustained lag phase and did not achieve sufficient turbidity to be read as resistant with the Autobac I system before 6 h. Thus, a false reading of susceptible could be obtained with the Autobac I system, depending on the ratio of susceptible organisms to resistant organisms selected for testing. A mixed susceptible and resistant population could be recognized by extending the incubation time of the Autobac I cuvette or by using other susceptibility methods to test isolates with light scattering indexes of <1.0.",
author = "Mayo, {J. B.} and Kiehn, {T. E.} and Brian Wong and Bernard, {E. M.} and D. Armstrong",
year = "1982",
language = "English (US)",
volume = "21",
pages = "412--415",
journal = "Antimicrobial Agents and Chemotherapy",
issn = "0066-4804",
publisher = "American Society for Microbiology",
number = "3",

}

TY - JOUR

T1 - Examination of Pseudomonas aeruginosa-gentamicin discrepancies encountered in an Autobac I-disk diffusion comparison

AU - Mayo, J. B.

AU - Kiehn, T. E.

AU - Wong, Brian

AU - Bernard, E. M.

AU - Armstrong, D.

PY - 1982

Y1 - 1982

N2 - Seven Pseudomonas aeruginosa strains found to be susceptible to gentamicin by the Autobac I system and resistant by the Bauer-Kirby disk diffusion method were tested for the presence of mixed populations of cells. Double zones of inhibition randomly appeared on gentamicin disk diffusion plates, and susceptible and resistant subpopulations were isolated from these plates. Growth kinetic studies of separated strains and mixed subpopulations indicated that the susceptible organisms grew rapidly and were read as susceptible at 5 h with the Autobac I system. Resistant organisms entered a sustained lag phase and did not achieve sufficient turbidity to be read as resistant with the Autobac I system before 6 h. Thus, a false reading of susceptible could be obtained with the Autobac I system, depending on the ratio of susceptible organisms to resistant organisms selected for testing. A mixed susceptible and resistant population could be recognized by extending the incubation time of the Autobac I cuvette or by using other susceptibility methods to test isolates with light scattering indexes of <1.0.

AB - Seven Pseudomonas aeruginosa strains found to be susceptible to gentamicin by the Autobac I system and resistant by the Bauer-Kirby disk diffusion method were tested for the presence of mixed populations of cells. Double zones of inhibition randomly appeared on gentamicin disk diffusion plates, and susceptible and resistant subpopulations were isolated from these plates. Growth kinetic studies of separated strains and mixed subpopulations indicated that the susceptible organisms grew rapidly and were read as susceptible at 5 h with the Autobac I system. Resistant organisms entered a sustained lag phase and did not achieve sufficient turbidity to be read as resistant with the Autobac I system before 6 h. Thus, a false reading of susceptible could be obtained with the Autobac I system, depending on the ratio of susceptible organisms to resistant organisms selected for testing. A mixed susceptible and resistant population could be recognized by extending the incubation time of the Autobac I cuvette or by using other susceptibility methods to test isolates with light scattering indexes of <1.0.

UR - http://www.scopus.com/inward/record.url?scp=0020027775&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0020027775&partnerID=8YFLogxK

M3 - Article

C2 - 6808909

AN - SCOPUS:0020027775

VL - 21

SP - 412

EP - 415

JO - Antimicrobial Agents and Chemotherapy

JF - Antimicrobial Agents and Chemotherapy

SN - 0066-4804

IS - 3

ER -