WordPress with SQLite Integration Plugin

just downloaded wordpress-4.1.2.zip and sqlite-integration.1.8.1.zip and unzipped them locally in a system with the following specifications:

• Apache: Apache/2.4.7 (Ubuntu)
• PHP: 5.5.9-1ubuntu4.9
• php5-sqlite: 5.5.9+dfsg-1ubuntu4.9

I stored sqlite-integration folder in plugins folder, and moved db.php file to wp-content folder and generated the required keys... The result was this message:

PDO Driver for SQLite is missing. Your PHP installtion appears not to have the right PDO drivers loaded. These are required for this version of WordPress and the type of database you have specified.

Did I miss something?

Thanks in advance for the help.