Bactericidal activities of chloramphenicol and eleven other antibiotics against Salmonella spp

Abstract

The bactericidal activity of chloramphenicol against 27 strains of Salmonella typhi and 33 strains of S. enteritidis was compared with those of 11 other antibiotics. The geometric mean bactericidal concentrations of chloramphenicol against susceptible strains (36.10 and 43.13 ,ug/ml for S. typhi and S. enteritidis, respectively) far exceeded those of the other 11 antibiotics, with cephalothin having the next highest values (2.67 and 8.66 ,uglml) and moxalactam (0.09 and 0.28 ,ug/ml), cefotaxime (0.08 and 0.28 ,ug/ml), ceftriaxone (0.07 and 0.16 ,uglml), norfloxacin (0.06 and 0.10 ,ug/ml), and aztreonam (0.05 and 0.20 ,ug/ml) having the lowest values. The results for imipenem (0.24 and 0.81 ,ug/ml) and ceftazidime (0.22 and Q.75 ,ug/ml) were lower than those noted for trimethoprim-sulfamethoxazole (1.20 and 5.56 ,ug/ml), cefamandole (0.62 and 3.29 ,ug/ml), and ampicillin (Q.55 and 2.78 ,ug/ml). The were carried out in duplicate in microtiter trays with Mueller-Hinton broth (14). The antibiotic concentrations used ranged from 0.05 to 100 ,ug/ml. Each well was inoculated to a cell density of ca. 100,000 CFU/ml. Pairs of inoculation trays were incubated at 37°C, one tray for 24 h and one tray for 48 h. The MIC was defined as the lowest concentration of antibiotic able to inhibit visible growth of the test organism. The contents of each clear well (0.1 ml) were spotted onto the surface of a predried Mueller-Hinton agar plate. After the spots had soaked into the agar, the plate was incubated at 37°C for 24 h. The MBC was defined as the lowest concentration of antibiotic able to kill at least 99.9% of the original inoculum (i.e., '10 colonies per spot).Summary MICs and MBCs were calculated including only susceptible strains. For calculation of the geometric mean (GM) MICs and MBCs, results that were equal to or less than the lowest concentration tested were used as is, whereas results that were greater than the highest concentration tested were arbitrarily assigned a value that was one dilution higher. RESULTSBased on both disk diffusion and MIC results, 6 (22%) of the 27 S. typhi strains were resistant to chloramphenicol. One of these six isolates was also resistant to ampicillin, whereas one other was also resistant to TMP-SMZ. The S. enteritidis isolates were more resistant. Of the 33 isolates, 17 (52%) were resistant to ampicillin. These 17 strains included 4 (12%) that were also resistant to chloramphenicol and 9 (27%) others that were also resistant to both cephalothin and cefamandole.In general, MICs and MBCs for S. enteritidis were higher than those for S. typhi (Tables 1 and 2). Chloramphenicol and cephalothin had the highest GM MICs for both S. typhi and S. enteritidis (for chloramphenicol, 2.60 and 2.31 ,ug/ml, respectively; for cephalothin, 1.76 and 3.04 ,ug/ml, respectively) (

Salmonella meningitis and its complications in infants

“…Five cases in this series had a documented recrudescence or relapse. Various reasons including antagonism between ampicillin and chloramphenicol against Salmonellae ; 18 the increasing resistance rate of common serotypes of Salmonella species to ampicillin and chloramphenicol, 19 and the bacteriostatic nature of chloramphenicol against Salmonella species, 20 have all been postulated as the possible reasons.…”

Therapy of experimental meningitis due to Salmonella enteritidis

“…Chloramphenicol is bacteriostatic against S. typhi and S. enteritidis strains in vitro (30) and does not fulfill this important criteria for the optimal therapy of meningitis. Although TMP-SMX is bactericidal against S. typhi at clinical concentrations, the agent is bacteriostatic only against most S. enteritidis isolates (30). Ceftriaxone and imipenem are very active against both of these Salmonella species as well as the less common S. cholerasuis (MBC for 90% of strains, 0.25 to 0.5 ,ug/ml).…”

“…Ampicillin has less bactericidal activity than ceftriaxone or imipenem against Salmonella spp. in vitro (4,26,30).…”

“…They have excellent activities against Salmonella spp. in vitro (26,30) and favorable pharmacokinetics in CSF (7,9,11). The increased prevalence of in vitro resistance to ampicillin, chloramphenicol, and TMP-SMX by the causative serotypes and the frequent complications of Salmonella meningitis outlined above prompted us to investigate alternative agents for the therapy of experimental Salmonella meningitis in vivo in a rabbit model.…”

The Cephalosporin Antibiotic Agents — II. First- and Second-Generation Agents

“…2 In vitro susceptibility tests poorly predict the inadequate clinical responses in Salmonella {typhi and enteritidis) infections treated with cefamandole. 7 Penicillinase-producing strains of N. gonorrhoeae and H. influenzae 2 as well as Clostridiumperfringens and other non B.fragilis, anaerobic bacteria are sensitive to cefamandole. 3,6 Cefoxitin, a cephamycin, is highly resistant to betalactamase hydrolysis.…”