Determination of the prevalence of antimicrobial resistance to macrolide antimicrobials or rifampin in Rhodococcus equi isolates and treatment outcome in foals infected with antimicrobial-resistant isolates of R equi

Abstract

Interpretation of the results emphasized the importance of microbiological culture and antimicrobial susceptibility testing in foals with pneumonia caused by R equi.

Susceptibility profile of Brazilian Rhodococcus equi isolates against azithromycin, clarithromycin and erythromycin

“…BUCKLEY et al (2007) (GIGUÈRE et al, 2010). Differently, in this study it was not observed significant increase in the MIC values for isolates collected from 1991 to 2013 (P>0.05).…”

“…However, for CLR, the clinical samples showed the major MIC values when compare with R. equi isolates from feces, soil and installations samples (P<0.05). This result is according to selection pressure hypothesis, since rhodococcosis is a chronic disease and repeated treatment can easily target to macrolide resistance (GIGUÈRE et al, 2010). RIBEIRO et al (2006) demonstrated strong efficacy of AZM against Brazilian R. equi isolates (MIC 90 <1.5µg ml -1 ).…”

“…This disease is responsible for large economic losses due to mortality, since pneumonia is a major cause of death in foals (GIGUÈRE et al, 2011). In vitro, R. equi has to be sensitive to a wide variety of antibiotics, such as aminoglycosides, beta-lactams and second-generation of cephalosporins (GIGUÈRE et al, 2010). However, their ability to replicate in macrophages and neutrophils limited the therapeutic options to drugs able to penetrate in lipophilic environment (BUCKLEY et al, 2007).…”

“…The antimicrobials (AZM, CLR and ERY) were tested at 0.03 up 128µg ml -1 . The standard strain, R. equi ATCC 33701, known to be sensitive to AZM, CLR and ERY, was used as quality control tests (GIGUÈRE et al, 2010). The MIC was defined as the lowest concentration of antimicrobials that inhibited the visible growth of R. equi isolates after overnight incubation evidenced by the addition of 20μL of 2,3,5-triphenyltetrazolium chloride (Vetec ® ) 1%.…”

Efficacy of Gamithromycin for the Treatment of Foals with Mild to Moderate Bronchopneumonia

“…In addition, the use of the 2 classes of drugs in combination reduces the likelihood of development of resistance to either drug 24, 25, 26. This is particularly important given the fact that the prevalence of macrolide resistance among R. equi isolates might be increasing 27. A recent study documented emergence of widespread macrolide resistance at a farm after widespread use of these drugs was instituted for the treatment of foals with subclinical pulmonary lesions 28…”