Using nginx + wordpress with all wordpress files in a subdirectory

You're just lacking an index directive

server {
  listen 80;
  server_name     www.example.com;

  access_log      /var/log/nginx/www.example.com.access.log main;

  root            /var/www/example/htdocs;
  index           index.php;

  location / {
     try_files $uri /wordpress$uri/ /wordpress/index.php?q=$uri&$args;
  }


  include /etc/nginx/includes/php5-wordpress.conf;
  include /etc/nginx/includes/deny.conf;
}