In vitro antibiotic activity on cecal anaerobes with emphasis on uric acid-utilizing bacteria

A total of 741 individual colonies or representative colonial types were isolated on basal-hlf-uric acid (UA) agar plates containing various antibiotics and on two types of control media. All of the antibiotics utilized in this study were capable of reducing bacterial numbers and/or bacterial groups in vitro when compared to the control plates. None of the antibiotics were selective for the uric acid bacteria. The majority (96%) of the cecal isolates utilizing uric acid were gram-positive. The basal-half-uric acid agar was a nonselective growth medium and supported the growth of virtually every bacterial group reported to be present in the avian cecum. The cecal flora of the adult White Leghorn hens tested was observed to be composed of 23% G+ (gram-positive) rods, 24% G- (gram-negative) rods, 26% G+ cocci, 9% G- cocci, and 18% G+ coccal-bacilli.