Factors Influencing Emergence of Tularemia, Hungary, 1984–2010

described for each of these drugs, but only 1 case of Rhodococcus infection has been reported for a patient receiving methotrexate and none have been described for patients receiving rituximab (10). Because of diffi culties in species identifi cation and delays in growth, non–R. equi infections might be underdiagnosed (9). This fi nding is complicated by the fact that these gram-positive bacilli may be misidentifi ed as contaminating diphtheroids (9). It is unlikely that this organism was a contaminant, given that the fever in the patient relapsed after antimicrobial drugs were discontinued and no other cause was identifi ed. The isolate from the patient was identifi ed by sequencing the fi rst ≈500 bp of the 16S rRNA gene, which is a useful molecular technique for speciation of the genus Rhodococcus (9). The isolate showed 99.8% identity with R. erythropolis type strain DSM 43066. Antimicrobial drug susceptibility patterns in non–R. equi rhodococci have not been studied, and there are no established standards for treating patients with Rhodococcus spp. infections. This case, along with previously reported cases, represents emergence of an opportunistic pathogen in a rapidly increasing patient population, namely those with impaired local or systemic immunity.