In vitro post-antibiotic effect of fluoroquinolones, macrolides, beta-lactams, tetracyclines, vancomycin, clindamycin, linezolid, chloramphenicol, quinupristin/dalfopristin and rifampicin on Bacillus anthracis.
OBJECTIVE
The aim of this study was to investigate in vitro the post-antibiotic effect (PAE) of 19 antibacterial agents against two strains of Bacillus anthracis (ST-1 and Sterne strains).


METHODS
PAE was determined by calculating the time required for the viable counts of antibiotic-exposed bacteria (at concentrations of 10x MIC and exposure for 2 h) at 37 degrees C to increase by 1 log10 above the counts observed immediately after antibiotic removal compared with the corresponding time for controls not exposed to antibiotics.


RESULTS
The PAEs of the fluoroquinolones (ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin and garenoxacin) were 2-5 h. The macrolide (erythromycin, clarithromycin and telithromycin) PAEs were 1-4 h, and that of clindamycin was 2 h. The PAEs induced by tetracycline and minocycline were 1-3 h. The PAEs induced by the beta-lactams (penicillin G, amoxicillin and ceftriaxone), vancomycin, linezolid and chloramphenicol were 1-2 h. The PAE induced by rifampicin was 4-5 h. Quinupristin/dalfopristin had the longest PAE, lasting for 7-8 h.


CONCLUSIONS
Our results indicate that the PAE is unrelated to the MIC but may be related to the rapidity of bacterial kill. These observations may bear importance on treatment regimens of human anthrax.
The Triangle Research and Development Center, Kfar-Qaraa, Israel.
A
A
Athamna
M
M
Athamna
B
B
Medlej
D J
DJ
Bast
E
E
Rubinstein
D000081:Acetamides / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001408:Bacillus anthracis / Q000187:drug effects* / Q000254:growth & development*; D002701:Chloramphenicol / Q000494:pharmacology; D002981:Clindamycin / Q000494:pharmacology; D024841:Fluoroquinolones / Q000494:pharmacology; D000069349:Linezolid; D018942:Macrolides / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D023303:Oxazolidinones / Q000494:pharmacology; D012293:Rifampin / Q000494:pharmacology; D013754:Tetracyclines / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology; D014769:Virginiamycin / Q000494:pharmacology; D047090:beta-Lactams / Q000494:pharmacology
D000081:Acetamides; D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D018942:Macrolides; D023303:Oxazolidinones; D013754:Tetracyclines; D047090:beta-Lactams; D014769:Virginiamycin; C062940:quinupristin-dalfopristin; D002981:Clindamycin; D002701:Chloramphenicol; D014640:Vancomycin; D000069349:Linezolid; D012293:Rifampin