H. B. Drugeon

Dietzia maris has been isolated from soil and the skin and intestinal tract of carp [1, 2] but has not yet been implicated in human disease. To our knowledge, w

DNA fingerprinting analysis of Mycobacterium tuberculosis is used for epidemiological studies and the control of laboratory cross-contamination. Because standardized procedures are not entirely safe for mycobacteriology laboratory staff, the paper proposes a new technique for the processing of specimens. The technique ensures the inactivation of M. tuberculosis before DNA extraction without the loss of DNA integrity. The control of inactivated cultures should be rigorous and should involve the use of two different culture media incubated for at least 4 months.

The aim of this study was to evaluate the relative potential of levofloxacin to select for resistance in Streptococcus pneumoniae in comparison with ciprofloxacin, sparfloxacin and ofloxacin. Two S. pneumoniae strains were studied; HBD 153 (parental strain, serotype 3) and HBD 964 (selected from the parental strain in an experimental mouse peritonitis infection model). MICs for the two strains were, respectively: 2 and 2 mg/L for ciprofloxacin; 2 and 4 mg/L for ofloxacin; 0.5 and 1 mg/L for sparfloxacin; 2 and 2 mg/L for levofloxacin. In-vitro, with 4 × MIC as the selection concentration, no mutant was obtained with strain HBD 153 (mutation frequency −8 ). With HBD 964, the mutation frequency was 9 × 10 ⁻⁷ for ofloxacin, 10 ⁻⁷ for ciprofloxacin, 4 × 10 ⁻⁵ for sparfloxacin and −8 for levofloxacin. In an immunosuppressed mouse peritonitis model (20 mice per dose), the S. pneumoniae strains were studied with sc doses of ciprofloxacin, sparfloxacin and ofloxacin at 50 mg/kg od, and with sc levofloxacin at a dose of 10 and 50 mg/kg od, or 10 and 50 mg/kg bid. The MICs for strains isolated after antibiotic treatment and the mutation frequencies at 4 × MIC were determined. Against HBD 153, sparfloxacin was the most active treatment, followed by levofloxacin 10 mg/kg and 50 mg/kg bid, but strains identical to HBD 964 (showing a resistant variant at 4 × MIC) were selected by sparfloxacin. Against HBD 964, levofloxacin (10 mg/kg and 50 mg/kg) was the most active drug. Highly resistant mutants were selected by ofloxacin and ciprofloxacin, but not by sparfloxacin and levofloxacin. In conclusion, the relative potential of levofloxacin to select for fluoroquinolone-resistant S. pneumoniae is lower than that of ciprofloxacin, ofloxacin and sparfloxacin both in vitro and in vivo.

The Roche Amplicor Mycobacterium tuberculosis PCR test was compared with mycobacterial culture for direct detection of M. tuberculosis in extrapulmonary specimens. From January 1995 to October 1996, 124 clinical specimens from 112 patients were assessed, including 47 body fluids, 61 tissue specimens and 16 abscesses. The sensitivity and specificity of Amplicor PCR compared to culture were 63.6% and 93.1% respectively. Analysis of 7 PCR-positive, culture-negative specimens confirmed that all were from patients with recently diagnosed tuberculosis under treatment. Eight specimens were PCR negative-culture positive, including a pleural fluid containing inhibitory substances. On acid-fast bacilli (AFB) smear-negative specimens, sensitivity and specificity were 53 and 100% respectively. The best results for Amplicor PCR were obtained with abscesses and biopsies. It is concluded that this test, highly specific for the diagnosis of tuberculosis, is at least as sensitive on extrapulmonary specimens as on smear-negative respiratory specimens.

Ofloxacin exhibit a good activity against the pathogen bacteria of the respiratory tract, except for S. pneumoniae. Its use is interesting because it has a good diffusion into respiratory tissues. However, the combination with an another antibiotic was necessary to spread the activity spectrum and to prevent the resistant variants. By the new killing curve checkerboard method, these 2 combinations are studied against 8 strains: 4 H. influenzae (2 beta-lactamase producers), 2 S. pneumoniae and 2 K. pneumoniae, at 0, 2, 4, 6 and 24 hours, a viable bacteria counting is executed by a microdilution method and is subcultured with a Steers-type multiple inoculator. With K. pneumoniae, ofloxacin has a dose dependent bactericidal activity which is maximum at 1 mg/l, While augmentin has a time-dependent activity. In the combination the synergy is rare. With H. influenzae, the results are the same; the bactericidal activity is less rapid but it is better than the ones with amoxicillin and clavulanic acid. With S. pneumoniae, the 2 antibiotics have the same activity. No antagonism is observed. And the antibiotic which has a better bactericidal activity determine the viable bacteria count.

Bactericidal action of antibiotics seems to be a test for the choice of antibiotic used and its dosage's adjustment. However, its use is limited by the determination's methods employed until now. By a viable bacteria counting micromethod, bactericidal action of three aminoglycosides: gentamicin, tobramycin and amikacin, is studied towards 48 bacterial strains. For each strain and each antibiotic, 11 antibiotic's concentration have been used, in a dilution range varying from 0.06 to 256 mg x l-1. Viable bacteria counting is executed after 1.5 h, 3 h and 5 hours of incubation. These antibiotics have a dose-dependent action. Regarding the smallest concentration of antibiotic permitted to lower to 3 log10 the bactericidal initial population, one can see that a concentration of 4 mg x l-1 is sufficient for 50% of strains with gentamicin and tobramycin, while a concentration of 16 mg x l-1 is necessary for amikacin. This result is corroborated by a statistical analysis carrying out by a variance analysis: it is showing a little significant difference between gentamicin and tobramycin, and very much significant differences between amikacin and the two others antibiotics.

The bactericidal activity of piperacillin was evaluated by the kill rate kinetics method. Piperacillin compared with amoxicillin, amdinocillin, mezlocillin, cefotaxime, ceftazidime and latamoxef. Against E. coli, piperacillin and antibiotics electively bound to penicillin-binding protein (PBP) 3 had the same, mainly time-dependent, bactericidal activity. Antibiotics bound to PBP 1 and 2 mainly have a dose-dependent activity. The bactericidal activity of piperacillin against E. coli was enhanced when the drug was combined with amoxicillin and amdinocillin; in contrast, the kill rate remained unmodified when piperacillin was combined with latamoxef. When the piperacillin-amikacin combination was tested against Pseudomonas aeruginosa, Enterobacter cloacae, Escherichia coli and Serratia marcescens, early synergism (5th hour), was weak, but after 24 hours piperacillin reduced the regrowth observed with the aminoglycoside, and synergism was much more pronounced irrespective of the species investigated.

Third-generation cephalosporins such as ceftriaxone are often used alone; however, with Enterobacter (ENT), Citrobacter (CIT), Serratia (SER) and Morganella (MOR), a combination of two drugs is advisable. Aminoglycoside-beta-lactam combinations are often synergistic. However, results are not consistent with the new cephalosporins. We determined the killing kinetics of ceftriaxone (C) alone, amikacin (A) alone and both drugs in combination (AC). The antibiotics were tested in the following concentrations: 0.25, 1, 4 and 16 X MIC for C, 0.5, 2 and 8 X MIC for A, and, for AC, 0.5-0.25 X MIC (1), 0.5-1 X MIC (2) and 2-0.25 X MIC (3). Surviving bacteria were enumerated at 0 h, 1 h, 3 h, 5 h and 24 hours. Amikacin showed a strong, dose-dependent bactericidal activity. Maximal activity of ceftriaxone was observed at 1 or 4 X MIC. Time of contact had a significant influence, indicating a time-dependent activity. In 5 hours, the killing effect of the AC combination rarely exceeded that of each antibiotic alone. Higher killing rates were observed with AC and; the killing effect of AC (3) was similar to amikacin's maximal killing effect. In 24 hours, the AC (3) combination was clearly synergistic with inhibition of late regrowths.

Cefsulodin, a new semi-synthetic cephalosporin, is characterized by its activity against P. aeruginosa. In this study the authors compared this new molecule with other four betalactamines, carbenicillin, ticarcillin, azlocillin and mezlocillin, and two aminoglycosides, amikacin and netilmicin. Two hundred and forty five strains studied were 100 Pseudomonas aeruginosa, 20 Acinetobacter, 42 Proteus, 21 Serratia, 22 Enterobacter, 20 Klebsiella and 20 E. coli. One hundred twenty strains of these showed carbenicillin resistant phenotype. MIC were determined by the agar dilution method. Cefsulodin was only active on Pseudomonas aeruginosa. MICs were at least 16 mg/l in the other species. On carbenicillin susceptible P. aeruginosa strains, the average MIC of cefsulodin, amikacin and netilmicin was 1 mg/l, and MICs of azlocillin, mezlocillin, ticarcillin and carbenicillin were 4-8 mg/l, 8 mg/l, 16 mg/l and 32 mg/l, respectively. On carbenicillin resistant P. aeruginosa, ticarcillin and mezlocillin were not effective and MICs of azlocillin and cefsulodin were 16 mg/l and 4-8 mg/l, respectively. However, MICs were between 64 and 128 mg/l in 20 p. cent of carbenicillin resistant strains.