Hi there! I'm studying Beta lactamase THIS week in my microbiology class! Cool! <img src="i/expressions/face-icon-small-blush.gif" border="0">) Sorry, I love science.
B-lactamase negative is GOOD. It's an enzyme that many bateria use as a defense mechanism to penicillin and many of it's derivitives, such as methicillin. Penicillin contains something called a beta lactam ring that binds to a protein in the bacterial cell wall (these proteins help build the bacteria's wall). The B-lactam binds and stops the bacteria's cell wall production, thus stopping the bacteria (it will burst). B-lactamase (the bacteria's defense that they aquire through mutations) open penicillin's B-lactam ring and render it useless, it can't bind to the proteins, so it can't stop the wall from being functional. The good thing is, when potassium clavulanate is added to Amoxicillin (it's then called Augmentin) that stops stops B-lactamase activity. Confusing, but this class and Anatomy and Physiology have helped me SO much in understanding what my daughters doctors are saying, what tests mean, etc.