title: Low concentrations of antibiotics.
abstract: Low concentrations of antibiotics have been shown to alter the morphology and ultrastructure of bacteria. Exposure to beta-lactam antibiotics produces large Gram-positive cocci or long filaments of Gram-negative bacilli. The ultrastructure of staphylococci in infected animals and patients treated with beta-lactam antibiotics is comparable to the structure of staphylococci grown on a solid support medium such as hard agar or a filter membrane but is different from the structure of staphylococci grown in liquid media. Antibiotic-modified bacteria are phagocytosed very efficiently; considering their bacterial mass, Escherichia coli filaments are killed much more efficiently by PMNs than is an equal mass of normal sized bacilli. Antibiotics at sub-MIC alter the synthesis and excretion of bacterial metabolites which results in a change in their virulence. Antibiotics at a very low dosage, 10 mg of ampicillin per day which resulted in sub-MICs in the urine, were shown to cure urinary infections in patients. These therapeutic results were attributed to the inhibition of bacterial adherence by sub-MICs of ampicillin.
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D007769:Lactams; D010587:Phagocytosis / Q000187:drug effects; D014552:Urinary Tract Infections / Q000188:drug therapy
chemical_list: D000900:Anti-Bacterial Agents; D007769:Lactams