Open AccessEffect of Several Components of Anaerobic Incubation on Antibiotic Susceptibility Test Results
Author(s) -
Jon E. Rosenblatt,
Fritz D. Schoenknecht
Publication year - 1972
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.1.5.433
Subject(s) - incubation , anaerobic exercise , microbiology and biotechnology , agar , chloramphenicol , biology , aminoglycoside , incubation period , antibiotics , tetracycline , food science , bacteria , biochemistry , physiology , genetics
The factors influencing the in vitro activity of antibiotics during anaerobic incubation were studied by the disc method with a facultative organism,Escherichia coli . We observed the effects of incubation aerobically, anaerobically (Torbal jars), in a CO2 incubator, and aerobically and anaerobically with all CO2 removed. We also monitoredp H changes during incubation and observed the effect of two different initial agarp H values (7.4 and 8.3). With aminoglycosides, zones were larger atp H 8.3 and, in each agarp H group, zones were decreased by incubation with increased CO2 (anaerobically and CO2 incubator). A fall in agarp H took place during the first 5 to 7 hr of incubation when increased CO2 was present. Decreased aminoglycoside zones in the presence of increased CO2 were due to fall in agarp H. Erythromycin showed the same zone size changes as the aminoglycosides. Chloramphenicol zones were somewhat smaller at the lower mediump H. Zones around tetracycline discs were largest after incubation anaerobically. Further aerobic (or CO2 ) incubation of plates after anaerobic incubation resulted in large “zones of relative inhibition” around the aminoglycoside discs. This suggests that these antibiotics had become more active after exposure to aerobic conditions. Our studies indicate that antibiotic susceptibility test results can be significantly altered by several components of anaerobic incubation including changes in agarp H and CO2 concentration as well as anaerobiosis per se.