I finally decided to do it by direct query to the database. Here is the query which gives the correct result for people who contributed very recently on blog.

Use following code to use above query in wordpress page:

<?php $fiverecentAuthors = $wpdb->get_results("SELECT post_author, max(post_date) as postdate FROM wp_posts WHERE post_type = 'post' AND post_status='publish' GROUP BY post_author ORDER BY postdate DESC LIMIT 5");

	foreach ($fiverecentAuthors as $recentAuthor) {
		$userId = $recentAuthor->post_author;
	}
?>

You can direclty get the user’s data using get_userdata() function supported by wordpress and use it for displaying details about selected authors.

<?php
    $user = get_userdata($userId);
?>

Hope it can be used by some people looking for similar requirements.

Here are two simple steps:

1. Create user

mysql> create user 'user'@'host' identified by 'some_password';

2. Grant privileges

mysql> grant select on db.* to 'user'@'host' with grant option;

Now user can login from host machine to check values in db schema.