Rhodococcus equi is an unusual zoonotic pathogen that can cause pneumonia in susceptible hosts. Twelve cases of R. equi infection were identified at a tertiary care center in central Kentucky. These patients were compared to cases reported in the literature, and an empiric treatment regimen for R. equi infection proposed.
Following IRB approval, patients with R. equi infection were identified by a SUNQUEST Epi computer search and the charts were reviewed. A literature search for publications with at least 10 cases of R. equi infection identified 4 studies from Europe and 2 studies from the United States (US) representing 137 cases. Current and previously reported cases were analyzed for clinical manifestations, prognosis, and susceptibility of R. equi isolates to antibiotics.
In the series of 12 cases of R. equi infection from Kentucky, all 8 immunocompromised patients (6 HIV-positive and 2 organ transplants) and 2 immunocompetent patients presented with pneumonia at initial diagnosis. Although the lungs were the primary site of infection in immunocompromised patients, extrapulmonary involvement only was more common in immunocompetent patients (p <0.0001). Mortality in R. equi-infected HIV patients was lower in the HAART era (8%) than in pre-HAART era (56%) (p<0.0001), suggesting that HAART improves prognosis in these patients.
In patients for whom susceptibility test results were available, 85%-100% of isolates were susceptible to vancomycin, erythromycin/clarithromycin, rifampin, aminoglycosides, ciprofloxacin and imipenem. In contrast, 0-14% of isolates were susceptible to penicillin, ampicillin, cephalothin oxacillin, and clindamycin. Of interest, there was a marked difference in susceptibility of R. equi to co-trimoxazole between the isolates from Europe (35/76; 46%) and those from the US (15/15; 100%) (p<0.0001).
The clinical presentation for R. equi infection differed for immunocompromised and immunocompetent patients. Empiric treatment of R.equi infection should include a combination of two antibiotics, preferably selected from vancomycin, clarithromycin/azithromycin, ciprofloxacin, rifampin or co-trimoxazole. Co-trimoxazole may be a therapeutic option in the US, but not Europe.
P. Gundelly, None