Article

Efficacy of several antibiotic combinations against Brucella melitensis Rev 1 experimental infection in BALB/c mice

University of Barcelona, Barcino, Catalonia, Spain
Journal of Antimicrobial Chemotherapy (Impact Factor: 5.44). 10/2006; 58(3):622-6. DOI: 10.1093/jac/dkl289
Source: PubMed

ABSTRACT The objective of the present study was to compare the efficacy of gentamicin given alone or combined with doxycycline with that of standard combination therapies in BALB/c mice experimentally infected with the Brucella melitensis vaccine strain Rev 1.
A standard broth microdilution method was applied to determine the susceptibility of strain Rev 1 to the clinically most relevant aminoglycosides. Eight groups of BALB/c mice were inoculated intraperitoneally (ip) with 1 x 10(6) cfu/mouse of strain Rev 1. While one group remained untreated, the other seven groups were treated 10 days later once a day for 14 days with (i) doxycycline given orally at 2 mg/day; (ii) streptomycin given ip at 0.4 mg/day; (iii) gentamicin given ip at 0.4 mg/day; (iv) rifampicin given orally at 0.5 mg/day; (v) doxycycline plus streptomycin; (vi) doxycycline plus gentamicin; and (vii) doxycycline plus rifampicin. The number of cfu per spleen and clearance of Rev 1 were assessed 34 days after inoculation.
With the exception of streptomycin, strain Rev 1 was susceptible to all aminoglycosides tested. As expected, the combination doxycycline/streptomycin was ineffective against Rev 1 infection. In contrast, the combinations doxycycline/gentamicin and doxycycline/rifampicin were effective in the clearance of Rev 1 infection, but only the former improved significantly the therapeutic efficacy as compared with that of the antibiotics given alone.
Gentamicin may be used along with doxycycline when the classical combination is considered the first choice in the treatment of patients with brucellosis due to B. melitensis vaccine strain Rev 1.

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    • "tetracyclines and streptomycin. As well, studies have shown that for treatment of patients with Br. melitensis vaccine strains Rev1, a gentamicin/doxycycline combination may be the first choice (Grilló et al., 2006). In general, tetracycline/aminoglycoside combinations are the most common antibiotics used for brucellosis treatment. "
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    ABSTRACT: Brucellosis, a zoonosis caused by four species of brucella, has a high morbidity. Brucella melitensis is the main causative agent of brucellosis in both human and small ruminants. As an alternative to conventional antibiotics, medicinal plants are valuable resources for new agents against antibiotic-resistant strains. The aim of this study was to investigate the usage of native plants for brucellosis treatment. For this purpose, the anti-brucella activities of ethanolic and methanolic extracts of Salvia sclarea, Oliveria decumbens, Ferulago angulata, Vitex pseudo-negundo, Teucrium polium, Plantago ovata, Cordia myxa, and Crocus sativus were assessed. The activity against a resistant Br. melitensis strain was determined by disc diffusion method at various concentrations from 50-400 mg/ml. Antibiotic discs were also used as a control. Among the evaluated herbs, six plant (Salvia sclarea, Oliveria decumbens, Ferulago angulata, Vitex pseudo-negundo, Teucrium polium, and Crocus sativus) showed anti-brucella activity. Oliveria decumbens was chosen as the most effective plant for further studies. A tested isolate exhibited resistance to tetracycline, nafcillin, oxacillin, methicillin, and colistin. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values for Oliveria decumbens against resistant Br. melitensis were the same (5 mg/ml), and for gentamicin they were both 2 mg/ml. Time-kill kinetics for a methanolic extract of Oliveria decumbens was 7 h whereas for an ethanolic extract it was 28 h. Also, Oliveria decumbens extracts showed a synergistic effect in combination with doxycycline and tetracycline. In general, the similar values of MIC and MBC for Oliveria decumbens suggest that these extracts could act as bactericidal agents against Br. melitensis. In addition to Oliveria decumbens, Crocus sativus and Salvia sclarea also had good anti-brucella activity and these should be considered for further study.
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    • "Although the reversion of Rev 1 to a virulent phenotype is unlikely (Ne'eman, 1968a,b), Rev 1 is able to induce abortions in pregnant animals and was also found excreted in milk of adult vaccinated animals (Banai, 2002). Virulence of Rev 1 strain for humans is well documented (Blasco and Diaz, 1993; Banai, 2002; Grilló et al., 2006). Although the owners of the dog had no particular recollection of a contact of their dog with farm animals, it is conceivable that the animal got infected directly by contact or indirectly via contaminated aborted fetus or milk of vaccinated animals. "
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    • "Thirty-six B. melitensis Rev 1 vaccine strains were investigated (Fig. 1). This collection includes 18 field strains isolated from ovine, bovine or human sources from Spain, France, South Africa or Israel, 11 strains from commercial batches obtained from 5 different Spanish manufacturing laboratories , 5 isolates from an experimental infection in mouse model [14] and 2 reference strains from culture collections (from Spain and France). Two B. melitensis 16M strains from different collections were used as references of biovar 1 and two additional field isolates of B. melitensis biovar 1 were included as controls. "
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    ABSTRACT: The assessment of the genetic stability is one of the essential elements to guarantee the biological quality of live anti-bacteria vaccines. Live attenuated Brucella melitensis Rev 1 is the most effective vaccine against brucellosis in small ruminants. Thirty-six B. melitensis Rev 1 vaccine strains isolated from human or animal sources from different geographic regions, from different commercial batches or laboratory collections were typed by the multiple-locus variable-number tandem repeat (VNTR) analysis (MLVA) recently described for Brucella spp. Our results demonstrated that B. melitensis Rev 1 group as assayed by MLVA is genetically very homogeneous. We believe that MLVA methodology could be an essential assay to guarantee the quality and stability of live anti-bacterial vaccines being produced worldwide and can be included as in vitro control.
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