Aztreonam selective agar for gram positive bacteria.

Aztreonam blood agar, a new selective medium for Gram positive aerobic bacteria, was evaluated in comparison with conventional media for skin swabs. Aztreonam agar increased the number of isolates of Staphylococcus aureus by 17%. By producing purer growths on primary isolation, it significantly speeded up the identification and sensitivity testing of staphylococci and streptococci. All major Gram positive aerobic pathogens grow on this medium. Aztreonam agar is now an established addition to our culture media. It is used for swabs which are likely to have a mixed Gram positive and Gram negative flora, such as ears, burns, ulcers, and for the sputa of patients with cystic fibrosis.