RHODOCOCCUS-EQUI - AN INCREASINGLY RECOGNIZED OPPORTUNISTIC PATHOGEN - REPORT OF 12 CASES AND REVIEW OF 65 CASES IN THE LITERATURE

Rhodococcus equi, a gram-positive, weakly acid-fast coccobacillus, ini tially isolated from horses, is becoming increasingly recognized as an important pathogen for immunosuppressed human hosts since the first h uman case was reported in 1967. A review of the English medical litera ture yielded 53 cases. During the last 11 years, the microbiology labo ratories of the authors isolated the organism from 12 patients. Of the total 65 cases, 60 occurred in immunosuppressed patients with HIV inf ection, malignant neoplasms, or chronic immunosuppressive therapy. The lung is the most common primary site of infection. Typically, the les ion is densely infiltrated by histiocytes with multiple microabscesses . Intracellular gram-positive coccobacilli are easily demonstrated. R equi grow's well on routine non-selective media at 35 degrees C. Previ ously, many cases may have been missed because the organism resembles oropharyngeal commensal diphtheroids. Clinical information with gram a nd Kinyoun stains on fresh isolates is helpful in recognizing the poss ibility of R equi infection.