Figure 2.

Spread-patch assay confirmation testing of purified antibiotic producers isolated using the modified crowded plate technique (mCPT). (A,B) Isolates identified using a d-alanine auxotroph of B. subtilis were retested on drug-sensitive B. subtilis (A) and S. aureus (B). (C,D) Confirmed antibiotic producers were tested using the spread-patch assay with vancomycin-intermediate strain of S. aureus (VISA5—resistant to 9 clinically used antibiotics) (C) and a carbapenem-resistant strain of K. pneumoniae (CRE143—resistant to 24 clinically used antibiotics) as target organisms (D). TYME plates were imaged at 7 days post-inoculation. For most isolates, zones of inhibition on the spread-patch assay are normally not observed until 3 days post-inoculation.