These resistant strains not only survive but multiply and pass from person to person. Penicillin, for example, was once highly effective in knocking out infection.
लेकिन वे हमेशा सभी हानिकारक जीवाणुओं को नहीं मारतीं; जीवाणुओं के कुछ अंश हमले का विरोध करते हैं ।