Madeleine Ravaoarinoro

Preparation, properties and the effects of amikacin, netilmicin and tobramycin in free and liposomal formulations on Gram-negative and Gram-positive bacteria.

The most common problems limiting the medical use of aminoglycosides have been the nephro- and oto-toxicities and the increasing bacterial resistance. It has been shown that encapsulation of drugs into liposomes enhances their efficacy while reducing their toxicities. The present in vitro study was designed to evaluate the antimicrobial activities of free and liposomal amikacin, netilmicin and tobramycin. We, therefore, encapsulated these drugs into liposomes prepared by sonication. The drug contained in liposomes was measured by enzyme multiplied immunoassay technique (EMIT) after lysis of the vesicles by 0.2% Triton X-100. The comparative encapsulation efficiency of the three antibiotic preparations was assessed. Aminoglycosides kinetic release from liposomes in presence of normal human sera was also studied in vitro over a 48 h period at 37 degrees C under 5% CO(2). The MICs of these encapsulated drugs to Pseudomonas aeruginosa, Xanthomonas maltophilia, Escherichia coli, Streptococcus faecalis and Staphylococcus aureus were determined and compared to those of respective free drugs using an agar dilution method. The amikacin and tobramycin encapsulation efficiencies were significantly (P </= 0.05) higher (5.36% +/- 0.17 and 5.06% +/- 0.10) than those of netilmicin (3% +/- 0.18). However, in presence of sera, liposomal retention of netilmicin was significantly (P </= 0.05) lower (61.88 +/- 0.14%) than that of amikacin (81.45 +/- 0.64%) and tobramycin (94.07 +/- 0.18%) after 1 h of incubation and then remained nearly constant over an 48 h period of the study. The MICs of liposomal netilmicin against all bacterial strains tested were reduced, compared to those of free netilmicin. However, liposomal amikacin and tobramycin MICs were nearly similar to those of free respective drugs. Overall, liposomal netilmicin appears to be a promising approach in the management of Gram-positive and Gram-negative bacterial infections and should be further evaluated in in vivo experiments.

Prevalence of and risk factors for sexually-transmitted infections in hidden female sex workers.

OBJECTIVES We wanted to determine the age-specific prevalence of selected sexually transmitted infections while assessing the risk factors among hidden female sex workers (HFSW). METHODS One hundred HFSW over 15 years of age were recruited in an impoverished area of Antananarivo, Madagascar. After oral informed consent, blood and endocervical swabs were tested for specific antigens, antibodies, and pathogens using molecular, serologic, and microscopic examinations. A risk factor analysis was conducted with odds ratios and 95% confidence intervals. RESULTS Thirty-two percent, 27, 12, and 7% of HFSW were infected respectively with Trichomonas vaginalis, Neisseria gonorrhoeae, Chlamydia trachomatis. Specific antibodies against, syphilis were detected in 11%. None were HIV-positive. The main factors associated with STI were: young age, being married, lower education level, early age for first intercourse, and a history of genital infection.

β-Lactamases and outer membrane investigations in β-lactam-resistant Comamonas acidovorans strains

Abstract Imipenem-induced β-lactamase (level of expression, specific activity and kinetic parameters (Vmax and Km) in response to nitrocefin) and outer membrane proteins (OMPs) (hydrophobicity, permeability and electrophoretic pattern) were characterized in, one β-lactam sensitive (PAC-9), one resistant (PAC-1) and two resistant laboratory mutants (PAC-9M, PAC-9M2) of Comamonas acidovorans strains. β-lactamases from both mutant strains showed different Vmax values compared to the parental strains. β-lactam resistance was found to be associated in PAC-1 with inducible β-lactamase production and OMP alteration by the appearance of a 102-KDa protein. Moreover, PAC-1 was less permeable to nitrocefin than PAC-9. These data indicate that C. acidovorans resistance to β-lactam resulted from synergy between β-lactamase and OMP alterations.

Comparative in vitro activity of nine antistaphylococcal agents against 275 recent isolates of Gram-positive cocci

The aim of this study was to compare the in vitro activities of 9 antistaphylococcal agents including teicoplanin (TEI) against 275 non-repetitive clinical strains representing 15 species of staphylococci and 27 strains of Enterococcus (E.) faecalis, isolated from various specimens between 1991-1992 at a Canadian teaching hospital. The NCCLS agar dilution method was used (10(4) colonyforming units/spot). In terms of MIC(90), TEI and vancomycin (VAN) appeared to be the most potent antibiotics against all staphylococci tested (TEI: 2.0-4.0 mug/ml; VAN: 1.0-2.0 mug/ml; ciprofloxacin (CPF): 0.25-32 mug/ml; cefazolin (CEF): 8.0-256 mug/ml; methicillin (MET): 2.0->256 mug/ml; imipenem (IMP): 1.0-32 mug/ml; erythromycin (ERT): 16->256 mug/ml; ampicillin (AMP): 16-128 mug/ml; fusidic acid (FSA): 0.5-16 mug/ml). Multiple resistant strains, including MET-resistant Staphylococcus (Staph.) aureus and Staph. epidermidis, were susceptible to TEI and VAN with respective MICs of 2-4 mug/ml and 1-2 mug/ml regardless of specimen type. Moreover, TEI was highly active against E. faecalis (MIC(90) for TEI and VAN: 0.5 and 4.0 mug/ml, respectively).

Inducible beta‐lactamases in clinical isolates of non‐aeruginosa Pseudomonas

The incidence of antimicrobial resistance and expression of imipenem‐inducible beta‐lactamase were examined in 22 strains of non‐aeruginosa Pseudomonas isolated from clinical specimens. The percentage of strains resistant to from one to eight antibiotics was 45. The most active antibiotics against all strains were norfloxacin, ciprofloxatin and imipenem. Eighteen out of the 22 strains were positive for beta‐lactamase in a spectrophotometric assay using nitrocefin as substrate. A low inducible beta‐lactamase specific activity (0.001‐0.999 nmoles nitrocefin hydrolyzed/min/mg protein) was found in twelve strains whereas six strains had a relatively high specific activity (3.5–159.8 nmoles nitrocefin hydrolyzed/min/mg protein). Five strains representing different Pseudomonas spp. and showing high beta‐lactamase activity were studied further. Crude enzymes from two species (Pseudomonas mendocina, Pseudomonas acidovorans) hydrolyzed cefazolin at a higher rate than penicillin and ampicillin. All enzymes from the five species were inhibited by cloxacillin and p‐chloromercuribenzoate (1 mM), but were insensitive to inhibition by clavulanic acid, ethylenediamine acetic acid (EDTA) at the same concentration. The isoelectric point and molecular weight of the main beta‐lactamase band from the 5 species were 6.5–6.8 and 47000 respectively.

Serotyping clinical isolates of Pseudomonas aeruginosa in relation to infection site antibiotic susceptibility and beta-lactamase production.

The present study investigates the association of O-serotype with isolation site, antibiotic resistance, and beta-lactamase production to determine the profiles of Pseudomonas aeruginosa clinical isolates circulating in a Canadian teaching hospital. The most frequently encountered serotypes of Pseudomonas aeruginosa strains isolated from inpatients at Hôtel-Dieu de Montréal hospital during the period 1992-1993 were O1, O3, O5, O6, O10, and O11 (9-13%) isolated from pus, urine, sputa and other sources. Serotype O1 was the most sensitive in contrast to serotype O3 which was resistant to virtually all antibiotics tested except to imipenem and quinolone. Of the strains of Pseudomonas aeruginosa, more than 50% with the most encountered serotype produced a high level of beta-lactamase.