Evaluation of oxacillin tolerance in Staphylococcus aureus by a novel method

Norfloxacin, ofioxacin, and other new quinolones, which are antagonists of the enzyme DNA gyrase, rapidly kill bacteria by largely unknown mechanisms. Earlier, we isolated, after mutagenesis, Escherichia coli DS1, which exhibited reduced killing by quinolones. We evaluated the killing of DS1 and several other strains by quinolones and j-lactams. In An important property of quinolones is their ability effectively to kill many bacterial species (11,12,47,60). Exposure of E. coli to a quinolone results in an initial rapid decrease in cell viability followed by a slowing or cessation of killing (6,8,11,12,18,21,47,62). The refractory subpopulation is composed of persisters (3, 24, 37) which are neither resistant mutants nor mutants that are less effectively killed on growth and reexposure to drug (62). Additional characteristics of killing by quinolones include a paradoxical reduction in killing at high drug concentrations (9,12,47,59); reduced killing in the presence of chloramphenicol, rifampin, or other treatments that inhibit protein synthesis (suggesting a requirement for synthesis of a protein [s] for killing [8,9,11,12,47,48,51,59,65]

Section: Discussionmentioning

confidence: 99%

Mutants of Escherichia coli K-12 exhibiting reduced killing by both quinolone and beta-lactam antimicrobial agents

Wolfson

Hooper

McHugh

et al. 1990

“…We recently introduced the ADPC method (27)(28)(29) as an alternative to the broth dilution plate count (BDPC) approach for the quantitative measurement of bacterial inhibition and killing by P-lactam agents. The procedure was designed to avoid the severe dependency on technical factor variations which have been shown to confound BDPC results.…”

Section: Discussionmentioning

confidence: 99%

“…We recently described a novel agar dilution plate count (ADPC) method for the quantitative measurement of Staphylococcus aureus inhibition and killing by oxacillin (27)(28)(29). Since Each culture was then further diluted as needed with MHB-C to produce standardized inoculum preparations for the ADPC tests.…”

mentioning

confidence: 99%

Ampicillin killing curve patterns of Haemophilus influenzae type b isolates by agar dilution plate count method

Woolfrey

Gresser-Burns

Lally

1987

Self Cite

“…Because the effects of 2% NaCl and temperature on the MBCs of oxacillin against such strains had not been examined, for each strain the MCB was determined under four conditions: in MHB with and without 2% NaCl supplementation and incubation at 30 and 35°C. And given the inherent problems with the MBC test (11,12,20) and the fact that, at least with cefamandole against Staphylococcus epidermidis (18), the MBC may not accurately reflect the activity of a specific antibiotic, for selected strains we also performed time-kill rate studies under the four conditions listed above. We found that neither salt supplementation of MHB nor the temperature of incubation influenced the MIC (macrotube) of oxacillin.…”

mentioning

confidence: 99%

Bactericidal activity of oxacillin against beta-lactamase-hyperproducing Staphylococcus aureus

Woods

Yam

1988

The bactericidal activit of oxacilin against ,B-lactamase-hyperproducing strains of Staphylococcus aureus for which the MIC by MicroScan was 1 or 2 ,ug/ml after incubation for 24 h was evaluated by MBC studies and kill kinetics methods. MBC and kil kinetics tests were both performed using Mueler-Hinton broth (MIIB), with and without 2% NaCl supplementation, and incubation at 30 (13,14,17). The use of these detection methods has allowed identification of strains that have been classified ase-resistant penicillin. One way to approach the question of appropriate therapy in the laboratory is bactericidal testing. Therefore, we examined the bactericidal activity of oxacillin against 3-lactamase-hyperproducing strains of S. aureus by determining the MBC. Moreover, because it has been shown that the MBC may not accurately reflect the activity of an antibiotic (18), we also conducted time-kill rate studies. For all tests performed, the effects of 2% NaCl and temperature were examined.