gistfile1.py

#!/usr/bin/python

import sys
import string
import re

word_separator = re.compile('(?:,|\n)')

filename = sys.argv[1]
filedata = open(filename).read()

lines = re.compile('\n').split(filedata)
words = word_separator.split(filedata)

for line in lines:
    for comp in re.compile(',').split(line):
        if not words.count(comp) > 1:
            lines.remove(line)
            break

print string.join(lines, '\n')