PURPOSE: To determine the prevalence and persistence of Mp in subjects with RA by real-time polymerase chain reaction (PCR) targeting the CARDS Txn gene (mpn 372)and P1 adhesin (mpn 141).
METHODS: Sputum, throat swab, nasal lavage and serum were obtained from adult subjects(age 18-65) seen in an outpatient clinic. RA was defined by persistent symptoms despite Step 5 of the NAEPP asthma management guidelines (high-dose ICS + LABA/LTRA). Samples were evaluated by quantitative real time PCR. CARDS TX-specific primers and TaqMan probe (FAM-labeled)were designed using Primer Express software (v 2.1; Applied Biosystems). The presence of IgM and IgG antibodies to M. pneumoniae P1 and CARDS protein in the sera was determined by ELISA. Patients positive for Mp were screened every 8-12 weeks until specimens for Mp were negative on 2 consecutive visits.
RESULTS: Samples were obtained in 62 adult subjects and 30/62 (48.4%) were positive for the CARDS Txn gene (mpn372). Thirteen of 62 (21%) were positive for P1 adhesin (mpn 141). No subjects were positive to P1 adhesin alone. Six of 62 subjects (9.7%)were persistently positive for CARDS Txn for a durations of 10.3 months (range 3-15 months)and another 2/62 (3.2%)were intermittently positive. Overall, 38/62 (61.3%)were IgG positive for CARDS by ELISA. Four of six persistently positive subjects never converted their IgG to CARDS Txn or P1 adhesin.
CONCLUSION: Subjects with refractory asthma may be chronically infected with Mp. Detection of Mp is significantly more common when PCR is directed to the CARDS Txn gene (mpn 372). Despite persistence of Mp in subjects with RA, some subjects fail to mount an IgG response to the organism.
CLINICAL IMPLICATIONS: Mp may play a role in the pathogenesis or persistence of refractory asthma. The impact of eradicating Mp in the airway of subjects with RA needs to be assessed.
DISCLOSURE: Jay Peters, No Financial Disclosure Information; No Product/Research Disclosure Information