Article Figures & Data
Figures
- FIG. 1.
Schematic representation of antibiotic exposure and recovery of MRSA isolates as a function of calendar dates (month/day/year). Antibiotic concentrations are given in micrograms per milliliter.
- FIG. 2.
PFGE patterns of JH isolates recovered at different times during the patient's clinical history. Chromosomal DNA was prepared, SmaI restricted, and separated by PFGE. For identification of the isolates, see Table 1.
- FIG. 3.
Oxacillin (top panel) and vancomycin (bottom panel) susceptibility profiles for JH isolates. Bacterial cultures were grown and plated on agar containing various concentrations of antibiotics for population analysis.
- FIG. 4.
Enrichment of the JH1 culture for a subpopulation of bacteria with elevated oxacillin resistance. Isolate JH1 was plated for population analysis on agar containing increasing concentrations of imipenem. Bacterial cells capable of forming colonies on agar containing 50 μg of imipenen/ml (arrow) were picked, diluted in drug-free TSB, grown overnight, and plated for population analysis on both imipenem- and oxacillin-containing plates.
- FIG. 5.
Enrichment of the JH1 culture for subpopulations of bacteria for which vancomycin MICs were elevated. Isolate JH1 was plated for population analysis on agar containing increasing concentrations of vancomycin. Bacterial cells capable of forming colonies on agar containing 4.0 μg of vancomycin/ml (arrow) were picked, diluted in drug-free TSB, grown overnight, and plated for population analysis (mutant JH1P4). Extended exposure of mutant JH1P4 to gradually increasing concentrations of vancomycin in growth medium eventually allowed for the selection of mutant JH1P4T4, for which the vancomycin MIC was 8.0 μg/ml.
- FIG. 6.
Suppression of phenotypic expression of resistance to oxacillin by selection of vancomycin resistance in isolate JH3. Bacterial cultures were grown in TSB to stationary phase and plated at several dilutions on TSA containing various concentrations of vancomycin. Single colonies that could grow at concentrations of vancomycin above the MICs for the majority of the cells were picked and suspended in growth medium supplemented with the same drug concentrations. After several cycles of selection, a mutant (JH3V8) for which the vancomycin MIC was 16 μg/ml was obtained.
- FIG. 7.
Changes in susceptibility to the bactericidal effect of vancomycin. The viability of isolates JH 1 and JH14 was determined during exposure to vancomycin at concentrations corresponding to 1, 2, 5, and 10 times the MIC. Exponentially growing cultures were exposed to the antibiotic (arrow), and aliquots were removed at various times to determine the viable titer of bacteria as described in Materials and Methods.
- FIG. 8.
Vancomycin susceptibility of strain PA237. The strain was grown overnight in TSB and then plated for population analysis on TSA plates containing various concentrations of vancomycin (○). A colony of strain PA237 growing on an agar plate containing 4 μg of vancomycin/ml was picked (arrow) and used as an inoculum for drug-free TSB to generate a new culture (PA237P4), the PAP for which is also shown (•).
Tables
- TABLE 1.
Genetic profiles of analyzed MRSA isolates
Isolate Date obtained (mo/day) Source MIC, μg/ml, of: MLST spaA type PFGE pattern Oxacillin (hetero classa) Vancomycinb JH1 7/20 Blood 0.75 (1) 1.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 JH2 9/20 Blood 25 (3) 4.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 JH3 9/24 Blood 100 (3) 4.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 JH5 10/01 Blood 0.75 (1) 6.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 JH6 10/06 Blood 1.5 (1) 8.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 JH9 10/13 Blood 0.75 (1) 8.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 JH14 10/17 Heart valve 1.5 (1) 8.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 JH15 10/23 Nares of contact 0.75 (1) 1.0 1-4-1-4-12-1-28 TJMBMDMGMK A0 PA237 1.0 1-4-1-4-12-1-10 TJMBMDMGMK A1 PC3 8.0 1-4-1-4-12-1-10 TJMBMDMGMK A1 Mu50 8.0 1-4-1-4-12-1-10 TJMBMDMGMK A2 M1 8.0 1-4-1-4-12-1-10 TJMGMK A1 NJ 8.0 1-4-1-4-12-1-10 TMBMDMGMK A3
- Top
- Article
- ABSTRACT
- MATERIALS AND METHODS
- Antibiotic susceptibility.
- Time-kill curves.
- DNA manipulations.
- MLST and spaA typing.
- Detection of mecA.
- RESULTS AND DISCUSSION
- Changes in oxacillin and vancomycin susceptibilities as a function of the chronological date of isolation of JH strains.
- Changes in growth rate and susceptibility to the bactericidal effect of vancomycin as a function of the chronological dates of isolation of JH strains.
- Vancomycin susceptibility of MRSA strain PA237.
- ADDENDUM
- ACKNOWLEDGMENTS
- FOOTNOTES
- REFERENCES
- Figures & Data
- Info & Metrics