[Species identification and molecular epidemiology of bacteria belonging to Ochrobactrum genus]. / Identification d'espèce et épidémiologie moléculaire des bactéries du genre Ochrobactrum.

Two species of medical interest belong to the genus Ochrobactrum, Ochrobactrum anthropi and Ochrobactrum intermedium. They are members of the microbiota of soil and an increasing number of works report the isolation of O. anthropi from clinical specimen, especially from immunocompromised patients and nosocomial infection. Involving of each species in human infection is poorly estimated due to unclear differential phenotypic characters. We performed 16S rDNA sequencing for identification of 20 clinical isolates of Ochrobactrum sp. to the species level. Then, we studied the phenotype of each isolate especially, morphology, culture onto different media and at different temperatures, biochemical characters and antibiotics resistance pattern. Colony morphology after growth onto Trypticase-Soy and McConkey agar, culture at 45 degrees C onto Trypticase-Soja agar, presence of urease, and netilmycin, tobramycin and colistin resistance allowed identification of species. Ribotyping using HindIII and EcoRI gave a supplementary criterion for species determination but did not allow typing at the infra-species level. In contrast, Pulsed-Field Gel Electrophoresis showed high degree of polymorphism between strains and proved the clonality of certain isolates. Thus, this method could be a useful tool for molecular epidemiology of Ochrobactrum infections.

Interactions between pairs of bacteriocins from lactic bacteria.

Activity of pairs of crude extracts of lactic acid bacteria (LAB) containing different bacteriocins (nisin, pediocin AcH, lacticin 481, lactacin F, and lactacin B) was measured against 10 different indicator strains. Experiments were carried out both in liquid and on solid media. Both synergisms and antagonisms were observed. Lacticin 481 produced mainly antagonistic effects whereas pediocin AcH produced mainly synergistic effects. The use of more than one LAB bacteriocin as a combination biopreservative might be envisaged.

Detection kinetics for positive blood culture bottles by using the VITAL automated system.

The VITAL system principle is based on homogeneous fluorescence technology. During an 11-month period, a total of 19,706 blood cultures from adult patients hospitalized in various establishments of the Montpellier Teaching Hospital were collected in VITAL bottles, of which 1,939 were declared positive. Only 204 bottles (1.04%) were false positives. The 1,735 true-positive bottles were collected from 130 patients. The final visual control permitted the detection of 10 falsely negative bottles (0.05%), of which 5 contained clinically significant microorganisms from four patients. The kinetics of detection for all microorganisms showed that 66.6% were detected within 24 h, 83.1% within 48 h, 95.5% within 120 h, and 100% within 150 h. No clinical episode would have been missed had a 5-day protocol been used instead of a 7-day protocol. Among the positive bottles, 65.7% were detected by the SLOPE algorithm, 20.1% by the DELTA algorithm, and 14.2% by the THRESHOLD algorithm. This retrospective study of our results shows that a 5-day protocol is sufficient for the detection of septic episodes using the VITAL system.

[In vitro activity of disinfectants against bacteria isolated in water for hemodialysis]. / Activité in vitro de désinfectants vis-à-vis de bactéries isolées d'eau pour hémodialyse.

The bactericidal and sporicidal activities of six disinfectants (Acétoper, Cidex, Phagoseptyl, Pyosynthène, Bétadine, Sterlane) were studied against 21 bacterial strains recovered from hemodialysis machines, and against two bacterial spores. AFNOR methods were used (NF T. 72-151, NF T. 72-171 et NF T. 72-231). Only Acétoper presented a bactericidal and sporicidal activity. A disparity in bactericidal concentrations was observed among Gram negative bacteria. Phenolic compound (Phagoseptyl) was not influenced by interfering substances. pH have a clear effect upon Cidex and Bétadine activities. Statistical analysis (variance and multiple comparisons test of Ryan-Einot) showed the significant role of the type of bacteria and the nature of disinfectants. These compounds were classified according to their increasing activity as following: Cidex, Sterlane, Phagoseptyl, Bétadine, Pyosynthène, Acétoper.

[Ciprofloxacin, clarithromycin, rifampin: in vitro bactericidal activity of double and triple drug combinations against strains of atypical mycobacteria]. / Ciprofloxacine, clarithromycine, rifampicine: activité bactéricide in vitro de doubles et triple associations sur des souches de mycobactéries atypiques.

Bactericidal activity of ciprofloxacin (CIP), clarithromycin (CLA), rifampin (RIF) alone and in combinations was studied against five atypical mycobacteria (4 isolates from patients with Acquired Immunodeficiency Syndrome and 1 collection strain) by time killing curves method. Drugs were used at their attainable serum levels: CIP (1 microgram/ml), CLA (2 micrograms/ml), RIF (16 micrograms/ml). The decrease in CFU in comparison to inoculum (10(6)-10(7) CFU/ml) was evaluated by viable counts after 1, 2, 3, 4 and 5 days of incubation at 35-37 degrees C. Drug combinations enhanced slightly the killing of drugs alone. CIP+CLA was the most effective against MAC strains whereas CIP+RIF appeared as the best combination against rapidly growing species except M. phlei which was the most resistant strain.

[Kinetics of bactericidal and sporicidal effects of a disinfectant against bacteria isolated from hospital units]. / Cinétiques des effets bactéricides et sporicides d'un désinfectant sur des bactéries isolées de l'environnement hospitalier.

The bactericidal and sporicidal activities of a peracetic acid disinfectant commonly used in hospitals (Acetoper 200) was studied using three bacterial species recovered in water from hemodialysis machines and humidifiers, i.e., Pseudomonas aeruginosa, Serratia liquefaciens, and Bacillus subtilis (spores). The method used was derived from AFNOR norms NF T 72-151 and NF T 72-231. For each strain, three concentrations of disinfectant were tested. Counts were performed every five minutes for one hour to evaluate killing kinetics. For both Gram-negative organisms, survival curves were biphasic, whereas B. subtilis counts decreased logarithmically. Both concentration and time influenced the 5 log10 decrease in counts. With S. liquefaciens and B. subtilis (spores), the 5 log10 decrease was not reached with low levels of disinfectant. In every case, the D value decreased substantially with increasing levels of disinfectant.

Comparative sensitivity study of Clostridium perfringens towards 16 antibiotics from different classes.

A series of 16 antibiotics from different classes (5-nitro imidazoles, beta-lactams, cyclins, macrolids, chloramphenicol) was examined for their bacteriostatic and bactericidal activities on 45 strains of Clostridium perfringens, with determination of MIC and MBC values. Several techniques of multivariate analysis were used in order to visualize differentiations in sensitivity profiles: Principal component analysis (PCA) and preferentially Correspondence factorial analysis (CFA). This approach revealed the efficacy of antibiotics from both general and family classifications.

[In vitro bactericidal effect of a piperacillin-pefloxacin combination against isolated strains of nosocomial pneumopathies in intensive care]. / Activité bactéricide in vitro de l'association pipéracilline-péfloxacine sur des souches isolées de pneumopathies nosocomiales en réanimation.

Combinations of piperacillin and pefloxacin are evaluated in vitro using checkerboard and killing-curves methods against 19 clinical isolates: S. aureus, K. pneumoniae, K. oxytoca, C. freundii, P. stuartii, Ps. aeruginosa, Ps. maltophilia and Ac. anitratum. The static checkerboard method showed more synergistic antibacterial effects than the killing curves method. The best synergistic effects appeared against S. aureus, K. oxytoca, P. stuartii, Ps. aeruginosa Ac. anitratum, including a notable increase of the rapidity of bactericidal activity. The combination PIP 64 micrograms - PEF 4 micrograms prevents the frequent secondary regrowth seen after 6 hours with the antibiotics used alone. No activity is obtained against S. aureus meti-R and Ps. maltophilia.

[Comparative effect of apalcillin and other beta-lactam antibiotics against the Bacteroides fragilis group]. / Activité comparée de l'apalcilline à celle d'autres bêtalactamines vis-à-vis de Bacteroides du groupe fragilis.

The in vitro activity of apalcillin was compared with those of mezlocillin, piperacillin, cefoxitin, cefotaxime and cefotetan against 50 strains of Bacteroides fragilis group. The minimal concentrations were determined by a microdilution method in Wilkins-Chalgren medium and subculturing on agar. On the basis of MICs and MBCs range, the activity of apalcillin was similar to that of other beta-lactam antibiotics; cefoxitin was slightly more active. The mode MICs were as follow: apalcillin = 16 micrograms/ml, mezlocillin = 8 micrograms/ml, piperacillin = 2 micrograms/ml, cefoxitin = 8 micrograms/ml, cefotaxime = 8 and 32 micrograms/ml, cefotetan = 4 micrograms/ml. All the strains of B. thetaiotaomicron and B. vulgatus were susceptible to the six beta lactam compounds. The MBCs and MICs were similar. Apalcillin had the greatest bactericidal activity.

Determination of aminoglycosides in pharmaceutical formulations--I. Thin-layer chromatography.

A simple, fast and reliable procedure for the determination of seven major aminoglycosides in commercial formulations (injections, capsules, eye drops, solutions and ointments) is presented. The aminoglycosides are separated on silica gel plates then located with ninhydrin and analysed in situ using a chromatogram spectrophotometer. Linearity tests, repeatability (relative standard deviation congruent to 3.5%) detection limits (60-200 ng) were satisfactory for all the compounds. Recovery data in pharmaceutical formulations (expressed as the percentage of the label claim) from thin-layer chromatography (TLC) and microbiological assays did not give any significant difference (P = 0.05); this result shows that TLC is a reliable method for the determination of aminoglycosides as the drug substance and in pharmaceutical formulations.

[Detection of visna-maedi virus antibodies and antigens by immunoblotting]. / Détection d'anticorps et d'antigènes du virus de Visna-Maedi par immunotransfert.

The visna-maedi virus was immunologically diagnosed using an immunoblotting technique from an antigenic preparation of the visna-maedi virus K796 purified by sucrose density gradient centrifugation. After SDS-PAGE electrophoresis and transfer onto a nitrocellulose sheet, the immunoblotting procedure was adapted to the search for specific antibodies in ovine serum samples. The results obtained showed that, in the natural visna-maedi disease, antibodies are not systematically detectable against every viral protein of the virus core. We have demonstrated the existence of antibodies directed against the proteins coded by the gag and the pol genes.

Photodegradation paths of cefotaxime.

The degradation kinetics of cefotaxime sodium salt in aqueous solution, under UV light at 254 nm, was investigated by HPLC and antibiotic activity. This degradation is the result of two competitive processes, an isomerization and a photolysis. This study is mostly about the isomerization step. The measured quantum yields for the cefotaxime to its anti-isomer and anti-isomer to cefotaxime isomerizations are, respectively, 0.10 and 0.12. A photostationary state characterized by an anti:syn ratio of 1.2 is obtained after 30 min of irradiation. The competitive photolysis, which actually consists of at least two processes (one on the delta 3-cephem ring and the second on the methoxyimino group), leads to an intense yellowing of the solution corresponding to the destruction of the molecule. The comparative evolution of the absorption spectra, under irradiation at 254 nm, of cefotaxime, thiazoximic acid, and 7-aminocephalosporanic acid shows that it is the delta 3-cephem ring photolysis which gives the yellow color. The major conclusion of this work is to call attention to the photoisomerization step which leads efficiently to the inactive anti-isomer, without giving any visible notice of degradation. Such a process is to be expected in all antibiotics containing an alkoxyimino linkage on the C-7 substitution.

[Influence of the inoculum effect on minimal inhibitory concentrations of 3 derivatives of 5-nitro-imidazole and 11 other antibiotics on Bacteroides fragilis]. / Influence de l'effet inoculum sur les concentrations minimales inhibitrices de trois dérivés du 5-nitro-imidazole et onze autres antibiotiques sur Bacteroides du groupe fragilis.

Three nitro-imidazole derivatives and eleven other antibiotics were studied for both their antimicrobial activity and the degree to which they produced inoculum effect on twenty strains of Bacteroides fragilis group. Five inocula were studied ranging from 10(5) to 10(9) CFU/ml. Statistical analysis show the significant influence of inoculum and those of strains. Nitro-imidazole derivatives exhibited a large inoculum effect while other antibiotics exhibited only a minimal to-no-inoculum effect.

[Comparative bactericidal kinetics of ciprofloxacin, ofloxacin and pefloxacin alone and in combination against strains of group D Streptococcus]. / Cinétiques de bactéricidie comparées de la ciprofloxacine, de l'ofloxacine et de la péfloxacine seules et en association sur des souches de streptocoques du groupe D.

Killing curves method was used to study bactericidal activity of the three quinolones, alone and in combination with penicillin, amoxicillin, fosfomycin, netilmicin, vancomycin against six isolates of enterococci. Alone, ofloxacin showed the most initial bactericidal effect but ciprofloxacin was the most frequently bactericidal without any regrowth in 24 hours. The combinations with beta-lactams and netilmicin were sometimes synergistic in 24 hours; fosfomycin increased initial bactericidal effect.

[Post-antibiotic effect of ciprofloxacin alone and in combination on Streptococcus faecalis]. / Effet post-antibiotique de la ciprofloxacine seule et en association sur Streptococcus faecalis.

Post-antibiotic effect (PAE) of ciprofloxacin has been studied on 2 strains of S. faecalis in the logarithmic phase after 2 exposure times and at concentrations ranging 0.5-10 times the MIC. At the end of the exposure period the antimicrobial is removed by dilution. Similar PAE is observed for ciprofloxacin and ofloxacin, higher than for pefloxacin. Ciprofloxacin-fosfomycin or ciprofloxacin-vancomycin combinations are indifferent or even antagonistic (vancomycin) in regards to PAE. Ciprofloxacin-penicillin or ciprofloxacin-netilmicin are weakly synergistic.

[Cytomorphological study of the action of ornidazole against Bacteroides fragilis]. / Etude cyto-morphologique de l'action de l'ornidazole sur Bacteroides fragilis.

The action of ornidazole on Bacteroides fragilis at the following concentrations, 4 MIC--MIC--MIC/2--MIC/4, is observed by electron microscopy, transmission and scanning, for 18 to 48 hours. The primary effect on ultrastructure was characterized by a distinct change in the morphology with filament formations and abnormal forms. Secondary effects were significant change in the distribution of ribosomes and abnormal cell division. No significant alterations in the peripheral cell wall were observed.

[In vitro study of the combination of pefloxacin with other antibiotics against Pseudomonas aeruginosa and Streptococcus group D]. / Etude in vitro de l'association de la péfloxacine à d'autres antibiotiques sur Pseudomonas aeruginosa et les Streptocoques du groupe D.

The comparative susceptibility of 50 isolates of enterococci and 50 isolates of Pseudomonas aeruginosa to pefloxacin and different antibiotics was tested using MIC determination. The results showed only 6% sensitive strains of enterococci and 36% of P. aeruginosa. The high level resistant streptococci against aminoglycosides and resistant Pseudomonas strains have weakly higher MIC than sensitive strains. The activity of the combination of pefloxacin and other antibiotics was determined by a checkerboard micromethod. Fractional concentration index (FIC and FBC) show most frequently addition, uncommonly synergy.

[Diffusion of piperacillin in the healthy human peritoneum after administration of a prophylactic dose]. / Diffusion de la pipéracilline dans le péritoine sain de l'homme après administration à dose prophylactique.

The passage of piperacillin into the omentum was evaluated in 23 patients who received one single intravenous injection of 2 grams. Median concentrations were 7.05 micrograms.g-1 at 30 min, 7.2 micrograms.g-1 at 60 min., 4.65 micrograms.g-1 at 90 min. and 3.53 micrograms.g-1 at 120 min. The corresponding maximal values were 36 micrograms.g-1, 59.7 micrograms.g-1, 36 micrograms.g-1 and 32 micrograms.g-1 respectively. Specimens collected beyond 2 hours showed that the concentrations obtained were maintained.