Confirmed Mycoplasma pneumoniae Endocarditis

To the Editor: In Rosario, Ar-gentina, during June 2005, a 15-year-old boy was hospitalized because of a 2-month history of fever. The patient had no history of cardiac disease or intravenous drug use. The results of the physical examination and the laboratory tests were within normal limits, except for an increased leukocyte count (14,000/μL) with 68% neutrophils. Transesophagic echocardiogra-phy showed mural vegetation on the right ventricle (30 mm × 20 mm) with no valve involvement. The patient was empirically treated with penicillin , gentamicin, and ceftriaxone. After treatment failed to produce a response, blood was submitted for culture for mycobacteria, brucellae, bartonellae, molds, and yeasts. BacT/ALERT bottles (bioMérieux, Durham, NC, USA), Hemoline performance biphasic medium (bioMérieux, Marcy L'Etoile, France), lysis centrifugation, and homemade culture broth were used. All culture results were negative. Results of PCR performed on serum for Actinobacillus actinomycetemcomi-tans were also negative. Because only the fi rst samples were obtained before antimicrobial drug administration, a false-negative result was suspected. The patient underwent surgery for pulmonary microembolisms, and the vegetation was removed 4 weeks after drug treatment had started. The histo-logic appearance of the vegetation was consistent with infectious endocarditis, but the culture result was negative. After 6 weeks of treatment, the patient was discharged from the hospital ; however, 10 days after discharge he again became febrile and was read-mitted to the hospital. The vegetation was again found. On this second admission , all cultures were performed before administration of antimicrobial drugs, and several types of culture media were used. In the absence of any growth by day 6, the patient's serum was screened for antibodies to Myco-plasma pneumoniae, Chlamydia pneu-moniae, and Bartonella henselae. Se-rologic tests for immunoglobulin (Ig) G and IgM were conducted by indirect immunofl uorescence assay (slides from Bion; Des Plaines, IL, USA) and fl uorescein-labeled anti-human IgG and IgM (bioMérieux). For the IgM assay, the serum was pretreated with IgG/RF stripper (The Binding Site Ltd., Birmingham, UK). The titers for M. pneumoniae IgG and IgM antibod-ies were 2,048 and 160, respectively. Blood cultures were then subcultured in homemade Hayfl ick medium. These samples were incubated in 5% CO 2 in a 37°C incubator and examined 2×/week for typical M. pneumoniae colonies. After 9 days of incubation, Hay-fl ick agar plates inoculated with ali-quots taken from homemade blood culture bottles (beef extract 5 g, yeast extract 5 g, peptone 10 g, glucose 2 g, NaCl …