Various embodiments of the present disclosure describe systems and methods for testing samples (e.g., biological samples, environmental samples, food samples etc.) for microbial contamination. For example, some embodiments describe an adapter assembly with a means to penetrate a septum of a collection vessel and permit gaseous communication between a headspace of the collection vessel and a sensor. In some embodiments, the gases in the headspace of the collection vessel can exit the collection vessel without contaminating the environment outside the system or allowing sample contamination. In some embodiments, the adapter assembly includes a membrane configured to prevent liquid in the collection vessel from contacting the sensor. In some embodiments, the adapter assembly can be used to access media inside the collection vessel for subculturing or aliquotting for another diagnostic process such as molecular diagnostics.