Effects of Thiamphenicol and Chloramphenicol in Inhibiting Neisseria gonorrhoeae Isolates

Abstract

Thiamphenicol was compared with penicillin, tetracycline, and chloramphenicol for its ability to inhibit 530 isolates of Neisseria gonorrhoeae, including 13 penicillinase-producing isolates. Thiamphenicol proved to be as active as chloramphenicol in inhibiting all of the isolates.Thiamphenicol, a chloramphenicol analog in which the nitro group has been substituted with a methylsulfonyl group (2), has been suggested as a viable alternate therapy regimen to penicillin in the treatment of infections with Neisseria gonorrhoeae (2). This antibiotic has been successfully used in treatment of uncomplicated gonococcal infections in both men and women (4, 15), with failure rates as low as 2 to 3%.Because penicillin and tetracycline treatment failures have been correlated with increased resistance to those antibiotics (5, 6), the use of thiamphenicol as an alternate therapy regimen in the treatment of N. gonorrhoeae should be seriously evaluated. In the present study, we have examined the minimal inhibitory concentrations (MICs) of 530 isolates of N. gonorrhoeae, including 13 f)-lactamase-producing isolates, to penicillin, tetracycline, chloramphenicol, and thiamphenicol.The fi-lactamase-producing isolates were obtained from Canadian, Asian, American, and African sources during the period 1976 to 1978. The other 517 nonpenicillinase-producing isolates were collected during a previous study (la) in 1973 to 1974. All strains were maintained at -70°C in heart infusion broth (Difco Laboratories, Detroit, Mich.) plus 20% glycerol. Before determining MICs, all isolates were subcultured on GC medium base (Difco), containing 1% (vol/vol) defined supplement (8), followed by incubation for 18 h at 35°C in an atmosphere containing 5% CO2. Penicillin-resistant isolates were tested for the production of fi-lactamase by using the chromogenic cephalosporin substrate, nitrocefin (13). MICs were determined by an agar dilution technique, and antibiotic-containing plates were inoculated by an adaptation of the method of Maier et al. (10). Antibiotic media consisted of GC medium base with 2% defined supplement to which the following antibiotics Organization isolates III, V, and VII (supplied by A. Reyn, Copenhagen) were used as control strains. The results were read after 18 h of incubation at 35°C in a 5% CO2 atmosphere. The MIC was considered to be that concentration of antibiotic which completely inhibited growth; the presence of one to nine colonies was accepted as being indicative of drug susceptibility. Table 1 shows the susceptibility of 517 non-,B-lactamase-producing isolates to penicillin, tetracycline, thiamphenicol, and chloramphenicol. Penicillin and tetracycline were more active than thiamphenicol and chloramphenicol; over 60% of the isolates was inhibited by concentrations of 0.25 U of penicillin or 0.25 ,ug of tetracycline per ml, as compared to under 30% inhibition by chloramphenicol and thiamphenicol at this concentration level. Over 90% of the isolates was inhibited by 2 jig of thiamphenicol or chloramphenicol per ml.In exa...

Comparative in vitro Activity of Chloramphenicol and Thiamphenicol against <i>Haemophilus Influenzae</i>, <i>Neisseria Gonorrhoeae</i> and the Typhoid and Paratyphoid Bacilli

“…Thiamphenicol has been found to be effective in the treatment of gonococcal infections [4] and this correlated well with the in vitro activity of this drug against N. gonorrhoeae [20], In accord with the results obtained on 13 ^-lactamase-producing N. gonorrhoeae strains reported by Duck et al [21], we have observed that the activity of thiamphenicol are not affected by ^-lacta mase production. Although both chloram phenicol and thiamphenicol have primarily a bacteriostatic action, Thayer et al [20] have reported that the bacteriocidal action of thiamphenicol against N. gonorrhoeae strains is only twice that of the bacteriostat ic concentration.…”

Time-kill curve analysis and pharmacodynamic modelling for in vitro evaluation of antimicrobials against Neisseria gonorrhoeae

“…These effects were confirmed by growth rates close to zero at high antimicrobial concentrations ( ψ min ). Resistance to tetracycline is widespread [ 36 ] and chloramphenicol is relatively toxic and has undesirable side effects [ 37 ], so neither of these antimicrobials is currently routinely used for the treatment of gonorrhoea.…”

Abstracts

“…A comparison of the in vitro activity of rosamicin, erythromycin, penicillin and tetracycline against N. gonorrhoeae, including P-lactamase producing isolates J. R. DILLON, P. D. DUCK, AND L. EIDUS (1978). Journal of Antimicrobial Chemotherapy, 4, [477][478][479] This paper examines the in-vitro activity of rosamicin, erythromycin, spiramycin, penicillin, and tetracycline against 517 nonpenicillinase-producing strains, and 13 penicillinase-producing strains of N. gonorrhoeae.…”