Assays Compared For Diagnosis of Mycoplasma Infection

Both molecular and serological assays have been compared for detection of Mycoplasma infection in nasopharyngeal aspirates and serum samples.

Two commercial polymerase chain reaction (PCR) assays including a real-time PCR test, and an oligochromatographic test, and one serology test were compared for the ability to detect Mycoplasma pneumoniae mainly in pediatric patients.

At the Universitat Autònoma de Barcelona (Spain) a total of 145 nasopharyngeal aspirate specimens were collected from June 2008 to December 2009. This included samples from pediatric patients with respiratory infection who presented at the emergency department and healthy children. Serum samples were obtained on admission, and convalescent serum samples were obtained 4–6 weeks later from all patients. Serum samples were tested on reception.

Serum samples were tested against M. pneumoniae using a commercial particle semiquantitative agglutination test kit (Serodia-Myco II test, Fujirebio; Tokyo, Japan, ). This agglutination assay uses gelatin particles sensitized with a crude antigen suspension of M. pneumoniae. The Speed-oligo M. pneumoniae test (Vircell; Granada, Spain) is a PCR-based method coupled to a dipstick device that enables a rapid detection of M. pneumoniae in clinical samples. The real-time PCR was performed with the SmartCycler II instrument (Cepheid; Sunnyvale, CA, USA).

Among the 145 samples, 32 serum pairs were serologically positive for M. pneumoniae. Of these, in 30 nasopharyngeal aspirates, M. pneumoniae was detected using the real-time PCR assay and 25 using Speed-oligo, corresponding to a sensitivity of 93.7% and 78.1%, respectively. Among the 94 samples with negative serology, only one positive result was obtained by real-time PCR assay. In the group of samples from healthy children, no positive results were obtained. M. pneumoniae is a pathogen that is a causative agent of respiratory tract infections

The authors concluded both PCR methods are fast; real-time PCR needs about one hour to complete and Speed-oligo PCR is completed within 55 minutes and detection requires no more than five minutes. However, the laboratory diagnosis of a chosen clinical episode should not rest on the PCR or acute phase serologic assay alone, but must also include antibody assays to confirm whether infection is current or represents persistence from past exposure. The study was published online on October 14, 2011, in the journal Diagnostic Microbiology and Infectious Disease.

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Universitat Autònoma de Barcelona
Fujirebio
Cepheid