Comparison of M4 and M4RT media for transporting cervical swab samples for PCR detection of Chlamydia trachomatis and Neisseria gonorrhoeae

Abstract

In a prospective study, M4RT medium was compared to the traditional M4 medium to transport cervical swab specimens for Neisseria gonorrhoeae/Chlamydia trachomatis (NG/CT) PCR testing using the Roche COBAS Amplicor. Two cervical swab samples were collected from 270 consecutive patients screened for NG/CT in a satellite facility. The swabs were placed individually in M4RT and M4 medium and were immediately refrigerated, transported to the laboratory on wet ice, and stored at 2 to 8°C until the PCR testing was performed within 7 da of collection. Seven of the cervical swab samples transported in M4 or M4RT were PCR positive for CT. Two additional samples transported in M4RT and a third swab transported in M4 were CT PCR positive. These samples were PCR negative in the alternative medium. Similarly, 12 of the cervical swabs transported in M4 or M4RT were NG PCR positive. Three additional swabs transported in M4 media were NG PCR positive. Initially, 2 of these samples when transported in M4RT were NG PCR equivocal and were considered NG PCR positive on repeat testing. Similarly, 2 additional swab samples transported in M4 RT media were NG PCR positive. These samples, when transported in M4 media, were NG PCR equivocal or negative. However, on repeat testing the equivocal sample was considered NG PCR positive. We conclude M4 and M4RT transport media are equally reliable for transporting cervical swab samples for NG/CT PCR testing. M4RT medium is more convenient to use, as it did not require refrigeration until it was inoculated with the clinical sample.