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

Unidad de Sanidad Animal, Centro de Investigación y Tecnología Agroalimentaria (CITA) de Aragón, Zaragoza, 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.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Brucellosis is a zoonosis caused by Brucella species. Brucellosis research in natural hosts is often precluded by practical, economical and ethical reasons and mice are widely used. However, mice are not natural Brucella hosts and the course of murine brucellosis depends on bacterial strain virulence, dose and inoculation route as well as breed, genetic background, age, sex and physiological statu of mice. Therefore, meaningful experiments require a definition of these variables. Brucella spleen replication profiles are highly reproducible and course in four phases: i), onset or spleen colonization (first 48 h); ii), acute phase, from the third day to the time when bacteria reach maximal numbers; iii), chronic steady phase, where bacterial numbers plateaus; and iv), chronic declining phase, during which brucellae are eliminated. This pattern displays clear physiopathological signs and is sensitive to small virulence variations, making possible to assess attenuation when fully virulent bacteria are used as controls. Similarly, immunity studies using mice with known defects are possible. Mutations affecting INF-γ, TLR9, Myd88, Tγδ and TNF-β favor Brucella replication; whereas IL-1β, IL-18, TLR4, TLR5, TLR2, NOD1, NOD2, GM-CSF, IL/17r, Rip2, TRIF, NK or Nramp1 deficiencies have no noticeable effects. Splenomegaly development is also useful: it correlates with IFN-γ and IL-12 levels and with Brucella strain virulence. The genetic background is also important: Brucella-resistant mice (C57BL) yield lower splenic bacterial replication and less splenomegaly than susceptible breeds. When inoculum is increased, a saturating dose above which bacterial numbers per organ do not augment, is reached. Unlike many gram-negative bacteria, lethal doses are large (≥ 108 bacteria/mouse) and normally higher than the saturating dose. Persistence is a useful virulence/attenuation index and is used in vaccine (Residual Virulence) quality control. Vaccine candidates are also often tested in mice by determining splenic Brucella numbers after challenging with appropriate virulent brucellae doses at precise post-vaccination times. Since most live or killed Brucella vaccines provide some protection in mice, controls immunized with reference vaccines (S19 or Rev1) are critical. Finally, mice have been successfully used to evaluate brucellosis therapies. It is concluded that, when used properly, the mouse is a valuable brucellosis model.
    Veterinary Research 04/2012; 43(1):29. · 3.38 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: (Full text is available at Isolation of slowly growing and fastidious Brucella spp strains from clinical specimens is difficult, because of varying factors, including species specificities, stadium of disease, and previous antibiotic treatment of the patients. The use of automated blood culture systems has overcome some cultivation problems. The automated identification system such as VITEK 2 compact allows more precise identification, as well. Aim: To present our own experience in the isolation of Brucella species from blood cultures, by the Bact/Alert automated system, identification by the VITEK 2 compact system and antimicrobial susceptibility of isolated strains. Material and Methods: Patients from various regions of Macedonia hospitalized in the University Infectious Diseases and Febrile Condition Clinic in Skopje. FAN blood culture bottles (aerobic and anaerobic) of the Bact/Alert system were used, inoculated with 5-10 ml of blood, incubated under continuous agitation and monitored for up to 5 days or until they became positive (in our cases for 2-3 days). Confirmations of all isolates were made by the VITEK 2 automated system on GN cards. Results: During a period of three years, 113 blood cultures from patients with diagnosis of brucellosis hospitalized at the above-mentioned clinic were examined. A total of 16 blood cultures from different patients were positive (14.2%), showing Gram negative bacilli, oxidase positive small colonies on Columbia agar media. The isolates were identified as four biochemically different types of B. mellitensis, mainly within 8 hours. Susceptibility testing by the disk diffusion method on Muller Hinton agar showed sensitivity of all strains to cephalosporin, tetracycline, aminoglycoside and quinolone antibiotic groups. Conclusion: With the BacT/Alert system Brucella spp. were isolated in 14.2% of suspected cases of brucellosis. Isolation was done within 2-3 days. Only B. melitensis from the Brucella genus could be identified by the VITEK 2 system and some biochemical differences could be detected. The VITEK 2 system is not able to determine the susceptibility of B. melitensis. The Disk-diffusion method used in this study showed sensitivity to all tested antibiotics, although not recommended by CLSI for the Brucella genus. Key words: Brucella, BacT/Alert blood culture system, VITEK 2 compact system.
    Prilozi / Makedonska akademija na naukite i umetnostite, Oddelenie za biološki i medicinski nauki = Contributions / Macedonian Academy of Sciences and Arts, Section of Biological and Medical Sciences 07/2010; 31(1):117-32.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Brucellosis, a zoonosis caused by four species of brucella, has a high morbidity. The major cause of brucellosis worldwide is brucella melitensis. Medicinal plants are considered as new antibacterial sources that could replace conventional antibiotics in the treatment of antibiotic-resistant bacteria. The aim of this study was to evaluate the efficacy of some native plants, alone and in combination with some antibiotics, in the treatment of brucellosis. Methods: The present experimental in vitro study was carried out to evaluate the anti-brucella activities of essential oils of Rosmarinus officinalis L., Origanum syriacum, Thymus syriacus, Salvia palaestina Benth, Mentha piperia, and Lavandula stoechas L., alone and in combination with some antibiotics. The activity against 16 tetracycline-resistant B. melitensis isolates was determined by disc diffusion method incorporating a concentration of 5%. Antibiotic discs were also used as a control. Microdilution brucella broth susceptibility assay was used in order to determine the MICs of essential oils and five antibiotics. Results: Among all the herbs evaluated, only the essential oils of O. syriacum and T. syriacus plants demonstrated most effective anti-brucella activity, and were then chosen for MIC study. The minimal inhibitory concentrations (MIC50) of essential oils of O. syriacum and T. syriacus against tetracycline-resistant B. melitensis were 3.125 µl/ml and 6.25 µl/ml, respectively. Conclusion: Among the essential oils studied, those of O. syriacum and T. syriacus were most effective. Since a combination of levofloxacin and Thymus syriacus essential oil increased the efficacy of this antibiotic, O. syriacum and T. syriacus are recommended to be used as bactericidal agents against B. melitensis.
    Iranian Journal of Medical Sciences 03/2013; 38(1):44-50.


Available from
May 20, 2014